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  • 1.
    Ahlgren, Fredrik
    et al.
    University of Kalmar, Kalmar Maritime Academy.
    Ahlgren, Kristoffer
    University of Kalmar, Kalmar Maritime Academy.
    Gasens inverkan på oljan i ett hydrauliksystem2009Independent thesis Basic level (degree of Bachelor), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [en]

    I detta arbete har vi med en litteraturstudie försökt påvisa vad en inblandad gas i oljan i ett hydrauliksystem har för betydelse för funktionen. Vi har använt information i traditionell facklitteratur samt i tidskrifter och vetenskapliga rapporter och upptäckt att problemen som uppkommer av inblandade gaser inte är väl kända. Dagens lösningar på problemen är nästan alltid kostsamma och handlar om att behandla symptomen. Vi har tittat på de olika fysikaliska data som gasen inverkar på i oljan, utifrån detta har vi analyserat vilka effekter detta har för ett hydrauliksystems funktion. Vi kommer att diskutera grundproblemet till kavitation och vanliga problem som ett hydrauliksystem ofta har. Vi har lyckats presentera resultat på att inblandad gas i oljan har en mycket stor inverkan på ett hydrauliksystem. Vi har kommit fram till att mycket av dagens problem med hydrauliksystem helt skulle kunna byggas bort om man tog större hänsyn till oljans förmåga att lösa in luft.

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  • 2.
    Andersson, Anders
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Nilsson, Börje
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Acoustic Transmission in Ducts of Various Shapes with an Impedance Condition2008In: International Conference on Numerical Analysis and Applied Mathematics 2008, AIP, Melville, USA , 2008, p. 33-36Conference paper (Refereed)
    Abstract [en]

    Propagation of acoustic waves in a two-dimensional duct with an impedance condition at the boundary, is studied. The duct is assumed to have two ends at infinity being asymptotically straight, but otherwise to be arbitrarily shaped.The so called Building Block Method allows us to synthesize propagation properties for ducts with complicated geometries from results for simpler ducts. Conformal mappings can be used to transform these simple ducts to straight ducts with constant cross-sections.By using recently developed techniques for numerical conformal mappings, it is possible to construct a transformation between an infinite strip and an arbitrarily shaped duct with smooth or piecewise smooth boundary, keeping both smoothness and the well controlled boundary direction towards infinity that the above mentioned method requires.To accomplish a stable formulation of the problem, we express it in terms of scattering operators. The resulting differential equation is solved using wave splitting and invariant embedding techniques. We expand the involved functions in Fourier series, and hence, it is possible to give the operators a matrix representation. Numerical results are produced using truncated matrices.

  • 3.
    Axén, Evelina
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Jonasson, Ida
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Bulleråtgärder vid kapsåg2006Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This project is about noise reduction of a cross cut saw at ProfilGruppen Extrusions AB, Åseda. The problems with the sound level depend on the structure-borne sound that generates in the long profiles. To lower the sound level have press clamp constructions been developed which reduce and further attends have been suggested.

    Attempts and comperative measurings of the sound level have been evaluated. The results of the comperative measurings with viscoelastic plastic as damping element display certain damping. The damping can in all probability become larger using a thicker damping element.

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  • 4.
    Basic, Eldar
    et al.
    Växjö University. Växjö University, Faculty of Mathematics/Science/Technology. Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Fransson, Johan
    Växjö University. Växjö University, Faculty of Mathematics/Science/Technology. Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Omkonstruktion av friskluftsventil2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    By design and manufacturing of prototypes, in conjunction with sound and flow measurements, we successfully increased air flow through the vent Al-db 450. The producer of this fresh air vent is Fresh AB in Gemla, Sweden. For sound testing a box was designed and manufactured.

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  • 5.
    Bergquist, Martin
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Dzanic, Nermin
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Dämpning av fläktljud i diskmaskin2007Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This dissertation examines acoustic research of a disinfecting dishwasher type Getinge 8666/8668. The research has been performed in collaboration with Getinge Desinfection AB, a world wide known manufacturer of disinfecting equipment for healthcare, located in Växjö, Sweden. We have examined how to reduce noise from the dishwasher with simple measures. Measurements have been performed during the drying program of the machine. The drying fans are the dominating sources of sound, and the sound is air bourn. A systematic method by reducing the sound step by step shows that the major ways of sound is through the ceiling and through the floor. There is also a minor noise leakage through the gaps in the walls of the dishwasher. By isolating the ceiling, the floor and the gaps in the walls, it is possible to reduce the noise with totally 5.9 dB. With more production adapted solutions, in shape of an isolated floor base and a more efficient fan cover, it is possible to reduce the noise with as much as 3.6 dB. This dissertation is thought to be used as a basis for further acoustic research at Getinge Desinfection AB.

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  • 6.
    Blomgren, Niklas
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Expanded Metal Screens as Flow Controllers2010Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project was to investigate if expanded metal screens can deflect the flow around a bend, into the reactor of a selective catalytic reduction unit and to find a way of determining which screen would be optimal.

    The current solution is very heavy compared to expanded metal. Construction costs may be reduced if the expanded metal screens work.

    A screen is needed to minimize the wear on the catalysts in the reactor.

    For this project a model , in scale 1/10, measuring equipment, consisting of Prandtl-tubes, an anemometer and smoke torches were used. Eight different expanded metal screens were tested.

    The results showed that the expanded metal works well for the purposes of deflecting flow. The angle of the flow entering the catalysts was good, and the flow was evenly distributed across the cross-section of the reactor.

     

  • 7. Boij, Susann
    et al.
    Nilsson, Börje
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering. matematik.
    Scattering and absorption of sound at flow duct expansions2006In: Journal of sound and vibration, Vol. 289, no 3, p. 577-594Article in journal (Refereed)
  • 8. Boij, Susann
    et al.
    Nilsson, Börje
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering. matematik.
    Sound in flow ducts with sharp edges2007In: 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference) , Rome, Italy, May 21-23, 2007: Paper AIAA-2007-3410, 2007Conference paper (Other academic)
    Abstract [en]

    Important transmission paths for the noise produced by fans, engines and other machinery are the connecting ducts used for transport of gases. Hence, reliable methods for calculating the acoustic attenuation in such systems are of great interest. In the presence of sharp edges strong interaction between sound and flow may occur even at low Mach numbers, which should be accounted for. The interaction has been successfully described using the vortex sheet model with an unexpanded and unstable jet. The current paper deals with the generalization to stable jets.

    By using the so-called Building Block Method, rather complex silencers can be modelled from the results of two canonical problems: the scattering at the trailing and leading bifurcations, respectively. The strong flow-acoustic interaction occurs at the trailing edge only. Results are presented here for the bifurcation and the sudden area change at the trailing edge.

    The flow in the large part of the duct downstream and upstream of an area change is modelled in two regions where the acoustically thin shear layer is described by a newly proposed set of coupling conditions. We use a simple model with physically realistic stability properties for acoustically thin layers allowing for a hydrodynamically thick shear layer. In fact, the dynamic properties of the shear layer are changed continuously with the shear layer Strouhal number s from the unstable at vanishing s to a stable layer at high s. The transfer Strouhal number marks the border between the unstable and stable region.

    Like the vortex sheet model, two coupling conditions relate the fields on each side of the sheet, one of them being continuity of pressure. The second coupling condition means continuity of a variable ranging from displacement, similar to the vortex sheet model, at vanishing s via velocity to pressure gradient at infinite s. The used shear layer model is uniformly valid for all s and allows a straightforward generalization of a scattering theory for unstable shear layers, i.e. for small s. Analytic as well as numerical results for the acoustic scattering are presented.

  • 9.
    Bolmsvik, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Evaluation of vibration distribution from a full scale measurement in an eight storey wooden house2008In: Proceedings of ISMA2008: International Conference on Noise and Vibration Engineering / [ed] Sas, P. & Bergen, B., Katholieke Universiteit Leuven, Department of Mechanical Engineering , 2008, p. 593-607Conference paper (Refereed)
    Abstract [en]

    Flanking transmission measurements has been done in an eight storey wooden building in Växjö, Sweden. The flanking transmission is evaluated by studying the vibration distribution from a well defined source to the flanking surfaces in the room one floor below. Besides the vibration distribution measurements the sound pressure in the room were measured. The measuring campaign shows that the used technique can be carried out to capture the flanking transmission in a direct and trustful way. The technique shows that peaks in the sound pressure can also be related to peaks in different surfaces frequency response functions. By calculating the energy distribution between surface elements it was shown that the roof in the examined room was the part that absorbed the most of the added energy from the source. Thereby it was regarded as the flanking part that needed an improved design most.

  • 10.
    Bolmsvik, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Structural Vibrations of Wooden House Walls2006In: Journal of BUILDING ACOUSTICS, Vol. 13, no 4, p. 285-293Article in journal (Refereed)
    Abstract [en]

    The flanking transmission between apartments due to a structure borne source is studied. The apartments studied were two-storey houses with a wooden framework. Acoustic measurements are often made in new built apartments to make sure that they fulfil the building regulations. Traditional measurements give no information about the contribution of the surrounding walls to the sound transmission.

    This paper describes a method of measuring flanking transmission. The acceleration levels on the receiving parts in the apartment below the source are studied. Thereby the contribution to the sound pressure in the room from each flanking part can be distinguished.

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  • 11.
    Bolmsvik, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Structural-acoustic analysis of wall-to-floor joints in timber-framed housing2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Even though a building meets the regulations with respect to impact sound, structures with wooden frames may receive complaints from the inhabitants due to structure-borne sound in the lower frequencies. In this thesis measuring methods that are more precise than the traditional measuring methods have been used to see if they could give a better knowledge about flanking transmission in the low frequencies in timber-framed structures. The measuring results have been compared to FE models of a complete room. By comparing the non-traditional measurement results with the results from the FE model a straight forward comparison could be made.

    Two field measurements have been made within the scope of this thesis. In the first field measurement a two-storey house with four apartments was studied. A traditional tapping machine was used as a source, and an accelerometer measured the responses in the apartment below. This study showed differences in acceleration levels on the surrounding surfaces in the room below the source. The non-bearing apartment-separating wall was the surface that had the largest acceleration levels. In the second field measurement several accelerometers were used simultaneously to measure the responses. With the help of experimental modal analysis and by measuring at several points at the same time the operational deflection shapes of all surrounding surfaces in the reception room could be captured. In this measurement a shaker was used as a source, so that the applied load could be measured the whole time. The load had constant level containing all frequencies within the studied frequency range. Simultaneously, a microphone was used and the acceleration levels in the surrounding surfaces could be compared to the sound pressure in the room. The measurements showed, not surprisingly, that at the frequency where the largest sound pressure was found all surrounding surfaces had acceleration peaks.

    An FE analysis of the room from the second field measurement has been made. The analysis shows that by using a load similar to the load used in the experiments the velocity level of the responses are in the same range both in the analysis and in the experiments. It also shows that damping has a large influence and that the damping needs to be studied further to be able to use the model as a prediction tool for flanking transmission.

    However, even though the results from the measurements and the analysis have some deviations, a great deal can be learned about the phenomenon of flanking transmission of timber-framed structures by using the proposed methods.

  • 12.
    Bolmsvik, Åsa
    Linnaeus University, Faculty of Engineering and Technology, Department of Building and Energy Technology.
    Structural-acoustic vibrations in wooden assemblies:: Experimental modal analysis and finite element modelling2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This doctoral thesis concerns flanking transmission in light weight, wooden multi-storey buildings within the low frequency, primarily 20-120 Hz. The overall aim is to investigate how the finite element method can contribute in the design phase to evaluate different junctions regarding flanking transmission.

    Two field measurements of accelerations in light weight wooden buildings have been evaluated. In these, two sources; a stepping machine, and an electrodynamic shaker, were used. The shaker was shown to give more detailed information. However, since a light weight structure in field exhibit energy losses to surrounding building parts, reliable damping estimates were difficult to obtain.

    In addition, two laboratory measurements were made. These were evaluated using experimental modal analysis, giving the eigenmodes and the damping of the structures. The damping for these particular structures varies significantly with frequency, especially when an elastomer is used in the floor-wall junction. The overall damping is also higher when elastomers are used in the floor-wall junction in comparison to a screwed junction. By analysing the eigenmodes, using the modal assurance criterion, of the same structure with two types of junctions it was concluded that the modes become significantly different. Thereby the overall behavior differs.

    Several finite element models representing both the field and laboratory test setups have been made. The junctions between the building blocks in the models have been modeled using tie or springs and dashpots. Visual observation and the modal assurance criterion show that there is more rotational stiffness in the test structures than in the models.

    The findings in this doctoral thesis add understanding to how modern joints in wooden constructions can be represented by FE modelling. They will contribute in developing FE models that can be used to see the acoustic effects prior to building an entire house. However, further research is still needed.

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  • 13.
    Bolmsvik, Åsa
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Damping Assessment of Light Wooden Assembly With and Without Damping Material2013In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 49, p. 434-447Article in journal (Refereed)
    Abstract [en]

    Damping elastomers are often used in lightweight wooden constructions and are believed to have good sound insulating effects. In the present study the influence on the structural behaviour by using elastomer damping material (Sylomer®) in the joints, with particular respect to footsteps and floor vibrations, has been investigated. A full scale wooden mock-up was assembled with two different joint configurations and studied under free-free boundary conditions. In the first configuration, the joints between the floor and underlying walls were screwed together. In the second configuration the floor was resting free on top of ribs of elastomer damping material, equivalent to normal building practice when this material is used. Both configurations were analysed and evaluated using experimental modal analysis, in the frequency interval 10-115 Hz.

     

    The relative (viscous) damping ratios of the modes were found to be on average 1.2% for the screwed configuration and 2.1% for the configuration with elastomer damping material in the joints. The damping was found to vary significantly between modes in the elastomer case. It was found that at low frequencies damping was high for modes with large motion on the edge where the elastomer material was. At higher frequencies (above approx. 40 Hz), however, the damping for this configuration decreased. This is believed to be caused by a vibration isolation effect of the elastomer, decoupling the floor from the walls at higher frequencies.

     

    To assess the differences in vibration levels between the two configurations, mean acceleration levels of well spread points on the different building parts where computed and evaluated. It was found that above approximately 70 Hz, the mean vibration level in the elastomer configuration was significantly lower than for the screwed configuration. Below 70 Hz, however, for many frequencies the mean vibration level for the elastomer configuration was significantly higher than for the screwed configuration (as should be expected in vibration isolation). Problems with springiness and footsteps are due to loads in the frequency range of 10 to 50 Hz, this could indicate that elastomers, used as in the present study, could worsen these types of problems, although improving higher frequency acoustic performance.

  • 14.
    Bolmsvik, Åsa
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Ekevid, Torbjörn
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    FE modeling of wooden building assemblies2010In: InterNoise 2010-Lisbon Portugal 13-16 June, 2010, p. 1-10Conference paper (Refereed)
    Abstract [en]

    Residential timber framed buildings have in some cases received complaints from inhabitants due to structure-borne sound at low frequencies, even if the building meets the regulations with respect to impact sound quality. This paper describes FE-analyses to evaluate the test setups of a building assembly and to prepare for the full-scale experimental modal analysis planned. By modal analysis, the dynamic properties of a structure, such as eigen modes and damping characteristics, can be extracted.

     

    The test assembly consists of prefabricated wall and floor/roof timber elements. Different assembly and joining methods as well as building element are used. The eigen modes and damping differs between the assemblies investigated which influence the dynamic response in the lower frequencies. The results are carefully evaluated and planned measurements are discussed.

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  • 15.
    Celander, Filip
    University of Kalmar, Department of Technology.
    Rumsklang för hifi-lyssning: En undersökning av vanliga vardagsrums akustiska egenskaper2008Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpStudent thesis
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  • 16.
    Hamdan, Yosef
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. General electric .
    Rehmat, Hassam
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Influence of flow devices on partical,  flow, and temperature distribution in Electrostatic precipitator2019Independent thesis Advanced level (degree of Master (One Year)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Gaseous exhaust of different industries contains harmful particles such as dust or soot (unburned carbon) that can be dangerous for the environment. Electrostatic precipitators are used in industries to remove such harmful particles before its release into the atmosphere. Electrostatic precipitators are designed to remove more than 99% of the particles from the exhaust gases but there are many factors that can reduce the efficiency of an Electrostatic precipitator such as particle size distribution, velocity distribution, temperature skewness etc. This thesis evaluates the influcence of flow devices on temperature, flow, and particle distribution in an Electrostatic precipitator using computational fluid dynamics software Ansys CFX. With the introduction of well-designed and optimized flow devices, the temperature, flow, and particle distribution show a desired change and can hence positively influence the performance on an Electrostatic Precipitator.

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  • 17.
    Håbecker, Linus
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Strömberg, Victor
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Superhydrofobisk Coating: En studie som försöker minska rörfriktionsförluster med hjälp av invändig ytbehandling.2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The greatest loss of energy in a pipe system has many times been proven to be frictional loss. This study with that in mind, will try to answer if this type of loss can be prevented using a superhydrophobic coating on the inside of a pipe.

     

    This study uses two small-scale systems, one circulation system and one simplified system for freeflow testing. On both systems, measuring equipment is fixated close to the 1,5m test-pipe. Therefore, calculated and measured data is not distorted by the surrounding components. Measuring equipment is used to check volumetric flow, velocity, temperatures and differential-pressure. This data is later used to compare the frictional losses before and after applying the superhydrophobic coating.

     

    The results, after completed tests are the opposite of the expected results. The coating that has been used for this study causes a negative effect and, in turn results in a substantial increase of frictional loss.

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  • 18.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Muthusamy, Dinesh
    Blekinge Institute of Technology.
    Ahmad, Waqas
    Blekinge Institute of Technology.
    Gustavsson, Ingvar
    Blekinge Institute of Technology.
    Zackrisson, Johan
    Blekinge Institute of Technology.
    Nilsson, Kristian
    Blekinge Institute of Technology.
    Johansson, Sven
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Remotely Controlled Active Noise Contol Laboratiories2012In: The Nineteenth International Congress on Sound and Vivration, Curran Associates, Inc., 2012Conference paper (Other academic)
    Abstract [en]

    Remotely controlled laboratories in educational institutions are gaining popularity at an exponential rate due to the multidimensional benefits they provide. The Virtual Instrument Systems in Reality (VISIR) project by Blekinge Institute of Technology (BTH) Sweden has successfully implemented remotely controlled laboratories, with remotely controlled real instruments and experimental setups. Currently these laboratories provide students the opportunity to conduct experiments in the field of electronics, antenna theory and mechanical vibration measurements. In this paper a prototype system of a remotely controlled laboratory for active noise control (ANC) is introduced. The proposed lab will focus on addressing the problem of a ventilation duct noise. The laboratory is informative and to a great extent introduces a student to the general steps in ANC when it is suggested as a plausible solution for a noise problem. The student can perform an investigation concerning feasibility of active control, design, configuration and implementation of an active control system. The laboratory is based on a modern and relevant DSP platform with the corresponding software development environment controlled remotely. In addition, it may be utilized remotely both for lab assignments in acoustics courses and digital signal processing courses.

  • 19.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Nygren, Åse
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Challenges in Fulfilling the Intended Learning Outcomes of Remote of Laboratories: A Case Study of Active Noise Control and Acoustic Remote Laboratory2015In: 22nd International Congress on Sound and Vibration 2015 (ICSV 22), Curran Associates, Inc., 2015Conference paper (Other academic)
  • 20.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Żmuda, Maciej
    Konopka, Piotr
    Håkansson, Lars
    Blekinge Institute of Technology.
    Remote Control of Active Noise Control and Acoustics Experiment Setup via the Internet2014In: 21st International Congress on Sound and Vibration 2014 (ICSV 21) / [ed] Crocker, M.J., Curran Associates, Inc., 2014Conference paper (Other academic)
  • 21.
    Kodakadath Premachandran, Rammohan
    et al.
    Atlas Copco, SWE.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Comparison of Spectral Properties of the Vibration Signal and Line Pressure Signal of DTH Drill2016In: 23rd International Congress on Sound and Vibration 2016 (ICSV 23): From Ancient to Modern Acoustics, Publisher: Curran Associates, Inc., Curran Associates, Inc., 2016Conference paper (Other academic)
    Abstract [en]

    Quantifying and Monitoring of drilling performance are becoming exceedingly important in the case of Down the Hole drilling. Various economic, environmental and safety constraints are driving the drilling process to become more efficient. To make a robust system that would enable the performance/condition monitoring of the drilling, we must understand how different properties like different line pressure etc. respond to various drilling conditions and what information can they provide regarding the Drilling Performance. A comparison of different properties like spectral properties, of the vibration signals and Pressure signals under known conditions would enable better understanding of the drilling system and the physics behind the process. A comparison is made between the Spectral properties of the vibrational signals obtained from remote locations on the drill rig and pressure signals that provide the feed and holdback forces to the drill string and a correlation between their characteristics and patterns under good and bad drilling conditions have been made. A simplified model of the system is simulated and results are compared with the patterns obtained from analyzing the Vibration signals.

  • 22.
    Källström, Elisabeth
    et al.
    Luleå University of Technology ; Volvo Construction Equipment.
    Lindström, John
    Luleå University of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Karlberg, Magnus
    Luleå University of Technology.
    Bellgran, David
    Volvo Construction Equipment.
    Frenne, Nicklas
    Volvo Construction Equipment.
    Renderstedt, Reza
    Volvo Construction Equipment.
    Lundin, Joakim
    Volvo Construction Equipment.
    Larsson, Jonas
    Volvo Construction Equipment.
    Analysis of Automatic Transmission Vibration for Clutch Slippage Detection2015In: 22nd International Congress on Sound and Vibration 2015 (ICSV 22),, Curran Associates, Inc., 2015Conference paper (Refereed)
    Abstract [en]

    Heavy duty construction equipment is generally equipped with automatic transmission enablingto change gear ratio automatically. The clutches in an automatic transmission transfer torquefrom the engine to the gearbox and clutch failures may result in costly downtime of constructionequipment. To prevent costly downtime of construction equipment, condition monitoring in com-bination with condition based maintenance may be utilized. Different sensor data are collectedon a machine that enables condition monitoring. Vibration have been measured on an automatictransmission in a construction equipment machine during controlled driving sessions, with andwithout clutch slippage, on a test track. An initial investigation of the vibration measured on theautomatic transmission have been carried out with the purpose to find out if the vibration maycontain reliable information related to clutch slippage considered to be abnormal. Initial signalanalysis of the data have been carried out using Spectrogram and Spectral Kurtosis methods. Theresults indicate that information related to abnormal clutch slippage may be extracted from vibra-tion measured on an automatic transmission in a construction equipment machine.

  • 23.
    Mohammadnejad, Mostafa
    et al.
    Blekinge Institute of Technology.
    Ghazvini, Mahdi
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Finite Element Modeling of Dynamic Properties of Power Supply for an Industrial Application2015In: 22nd International Congress on Sound and Vibration 2015 (ICSV 22), Curran Associates, Inc., 2015Conference paper (Other academic)
  • 24.
    Nilsson, Börje
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Augey, Romain
    National Institute of Advanced Technology (ENSTA, Paris), France.
    Andersson, Anders
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Acoustic waves in a mean flow duct with varying boundary2009In: 15th AIAA/CEAS Aeroacoustics Conference, Miami 11-13May 2009: Paper AIAA-2009-3407, 2009Conference paper (Other academic)
    Abstract [en]

    The problem of modelling sound waves in a two-dimensional wave-guide of general shape carrying a mean flow is addressed. The mean flow may be inhomogeneous but is irrotational. A convective wave equation for the velocity potential is derived. It is in a form suitable for generalizing an earlier developed theory for a stable modelling of acoustic waves in quiescent waveguides with complicated geometry to also include a mean flow. The theory is illustrated with numerical results for reflection and transmission demonstrating the effectiveness of the method for low and medium frequencies.

  • 25.
    Nilsson, Börje
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Boij, Susann
    MWL, KTH.
    Acoustic waves in ducts with thin shear layers2007In: Proceedings of the 13th AIAA/CEAS Aeroacoustics Conference, Rome 21-23 May 2007: Paper AIAA-2007-3409, 2007Conference paper (Other academic)
  • 26.
    Nilsson, Börje
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Fishman, LoisMDF International, USA.
    Mathematical Modeling of Wave phenomena: 2nd Conference on Mathematical Modelling of Wave Phenomena, Växjö, Sweden, 14 – 19 August 20052006Conference proceedings (editor) (Other academic)
    Abstract [en]

    This conference illuminates and benefits from relations between different types of waves, i.e., quantum physics methods in classical wave modeling. The proceedings are intended for researchers and graduate students in fundamental as well as applied sciences. The preface classifies and summarizes the conference giving relations between the papers.

  • 27.
    Nilsson, Börje
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Fishman, LoisMDF International, USA.Karlsson, AndersElektro- och informationsteknik, LTH.Nordebo, SvenVäxjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Mathematical Modeling of Wave phenomena.: 3rd Conference on Mathematical Modelling of Wave Phenomena, Växjö, Sweden, 9 – 13 June 20082009Conference proceedings (editor) (Other academic)
    Abstract [en]

     

     

    This conference illuminates and benefits from relations between different types of waves, i.e., quantum physics methods in classical wave modeling. The proceedings are intended for researchers and graduate students in fundamental as well as applied sciences. The preface classifies and summarizes the conference giving relations between the papers.

     

     

     

     

     

     

  • 28.
    Olsson, Jörgen
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. SP Technical Research Institute of Sweden.
    Low Frequency Impact Sound in Timber Buildings: Simulations and Measurements2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An increased share of construction with timber is one possible way of achieving more sustainable and energy-efficient life cycles of buildings. The main reason is that wood is a renewable material and buildings require a large amount of resources. Timber buildings taller than two storeys were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden.

        Some of the early multi-storey timber buildings were associated with more complaints due to impact sound than concrete buildings with the same measured impact sound class rating. Research in later years has shown that the frequency range used for rating has not been sufficiently low in order to include all the sound characteristics that are important for subjective perception of impact sound in light weight timber buildings. The AkuLite project showed that the frequency range has to be extended down to 20 Hz in order to give a good quality of the rating. This low frequency range of interest requires a need for knowledge of the sound field distribution, how to best measure the sound, how to predict the sound transmission levels and how to correlate numerical predictions with measurements.

        Here, the goal is to improve the knowledge and methodology concerning measurements and predictions of low frequency impact sound in light weight timber buildings. Impact sound fields are determined by grid measurements in rooms within timber buildings with different designs of their joist floors. The measurements are used to increase the understanding of impact sound and to benchmark different field measurement methods. By estimating transfer functions, from impact forces to vibrations and then sound pressures in receiving rooms, from vibrational test data, improved possibilities to correlate the experimental results to numerical simulations are achieved. A number of excitation devices are compared experimentally to evaluate different characteristics of the test data achieved. Further, comparisons between a timber based hybrid joist floor and a modern concrete floor are made using FE-models to evaluate how stiffness and surface mass parameters affect the impact sound transfer and the radiation.

        The measurements of sound fields show that light weight timber floors in small rooms tend to have their highest sound levels in the low frequency region, where the modes are well separated, and that the highest levels even can occur below the frequency of the first room mode of the air. In rooms with excitation from the floor above, the highest levels tend to occur at the floor levels and in the floor corners, if the excitation is made in the middle of the room above. Due to nonlinearities, the excitation levels may affect the transfer function in low frequencies which was shown in an experimental study. Surface mass and bending stiffness of floor systems are shown, by simulations, to be important for the amount of sound radiated.

        By applying a transfer function methodology, measuring the excitation forces as well as the responses, improvements of correlation analyses between measurements and simulations can be achieved

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  • 29.
    Olsson, Jörgen
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. Research Institutes of Sweden (RISE).
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Measurements of low frequency impact sound transfer functions of light weight timber floors, utilizing the ISO rubber ball2018In: Proceedings of the 25th International Congress on Sound and Vibration, The International Institute of Acoustics and Vibration , 2018, p. 1-8Conference paper (Other academic)
    Abstract [en]

    Impact sound below 100 Hz is an important issue for light weight timber buildings. It is also well known that finite element model simulations are more beneficial in the low frequency range than in higher frequencies due to the longer wavelengths allowing the element meshes to be coarser. Utilizing transfer functions to describe impact sound would imply simplifications to correlate data stemming from measurements and low frequency finite element models. If the impact force is known, the simulations become easier since there would not be any need for the modelling of the impact mechanisms, just calculations of the transfer functions which are then combined with the force spectrum to give the resulting sound pressure. The impact ball has shown to be in close resemblance with a human's excitation in the low frequency range which makes it a suitable excitation device. However, when its force spectrum is needed, it may be hard in practice to achieve that during a regular measurement since the ball is not easily equipped with a force gauge. Here, two different methods are investigated. An investigation of the repeatability of the force spectrum of the rubber ball in the low frequency range for floors having different mobilities is made. To enable this, an equipment for field measurements of impact force spectrum and potentially point mobilities using an ISO ball, is designed, manufactured and evaluated. Impact force measurements are made on lightweight timber as well as concrete floors, with different properties for comparisons. Within the lowest frequencies it is potentially possible to use one given force spectrum from the ISO ball together with impact sound measurements for the creation of impact force to sound transfer functions on different floors.

    The full text will be freely available from 2020-08-03 10:06
  • 30.
    Peplow, Andrew
    et al.
    Hoare Lea Acoustics, Aztec West Business Park, England.
    Nilsson, Börje
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Acoustic Waves in Variable Sound Speed Profiles, 3rd Conference on Mathematical Modelling of Wave Phenomena2009In: Mathematical modellingg of wave phenomena: 3rd Conference on Mathematical Modelling of Wave Phenomena, Växjö, Sweden, 9 – 13 June 2008, Melville, New York: American Institute of Physics , 2009, p. 140-148Conference paper (Refereed)
    Abstract [en]

     

    An important topic in the area of airborne sound propagation is the prediction of sound propagation above an impedance ground with an atmospheric profile whose sound speed varies with height. Even if this problem is simple in concept, it leads to complications for general velocity profiles. This work illustrates the existence of a large class of realistic atmospheric profiles for which analytical solutions exist to be used as benchmark solutions for numerical methods. Spectral finite element results are discussed for sound propagation in a half-space situated above a ground surface impedance.

     

  • 31.
    Runesson, Sven
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Knutsson, Hugo
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Johansson, Steve
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Ljudreducering av värmepump2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This degree project handles acoustic measurements of the heat pump EcoAir 107, made by Enertech CTC AB. The sound from the three sound sources of the heat pump, fan, compressor and four way valve, have been measured to find out how they affect the total sound level of the product.

    Measures to attenuate the sound level have been developed and tested. By comparing these with the sound of the heat pump, in its original state, we have found out the measures which have best effects.

    The best attenuating measures came to be: taped openings and holes around the compressor space, isolating the top and the bottom of the whole construction, support of the fan bottom part and shielding of the sound source with a screen at a distance of 110 mm

    These measures have been tested together and an average attenuation of the total sound level with 3,9 dB have been accomplished. In the front of the fan where the continuous sound is the strongest, the attenuation was 4,7 dB.

    This project is meant to be used as a guide by Enertech CTC AB:s during their future developing process.

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  • 32.
    Tryggeson, Henrik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Analytical vortex solutions to Navier-Stokes equation2007Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Fluid dynamics considers the physics of liquids and gases. This is a branch of classical physics and is totally based on Newton's laws of motion. Nevertheless, the equation of fluid motion, Navier-Stokes equation, becomes very complicated to solve even for very simple configurations. This thesis treats mainly analytical vortex solutions to Navier-Stokes equations. Vorticity is usually concentrated to smaller regions of the flow, sometimes isolated objects, called vortices. If one are able to describe vortex structures exactly, important information about the flow properties are obtained.

    Initially, the modeling of a conical vortex geometry is considered. The results are compared with wind-tunnel measurements, which have been analyzed in detail. The conical vortex is a very interesting phenomenaon for building engineers because it is responsible for very low pressures on buildings with flat roofs. Secondly, a suggested analytical solution to Navier-Stokes equation for internal flows is presented. This is based on physical argumentation concerning the vorticity production at solid boundaries. Also, to obtain the desired result, Navier-Stokes equation is reformulated and integrated. In addition, a model for required information of vorticity production at boundaries is proposed.

    The last part of the thesis concerns the examples of vortex models in 2-D and 3-D. In both cases, analysis of the Navier-Stokes equation, leads to the opportunity to construct linear solutions. The 2-D studies are, by the use of diffusive elementary vortices, describing experimentally observed vortex statistics and turbulent energy spectrums in stratified systems and in soapfilms. Finally, in the 3-D analysis, three examples of recent experimentally observed vortex objects are reproduced theoretically. First, coherent structures in a pipe flow is modeled. These vortex structures in the pipe are of interest since they appear for Re in the range where transition to turbulence is expected. The second example considers the motion in a viscous vortex ring. The model, with diffusive properties, describes the experimentally measured velocity field as well as the turbulent energy spectrum. Finally, a streched spiral vortex is analysed. A rather general vortex model that has many degrees of freedom is proposed, which also may be applied in other configurations.

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    FULLTEXT01
  • 33.
    Yanaz Cinar, Özge
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Boij, Susann
    MWL, KTH.
    Cinar, Gökhan
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Nilsson, Börje
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Jet pipe reflections – influence of geometrical and flow exit conditions2010In: 16th AIAA/CEAS Aeroacoustics Conference, Stockholm, Sweden, June 7-9 2010: Paper AIAA-2010-4013, AIAA , 2010Conference paper (Other academic)
    Abstract [en]

    In this paper, we study the influence of the exit conditions on the acoustic reactions at a jet pipe opening. For the flow exit conditions, the model of Munt assuming a vortex sheet at the exit of a semi-infinite jet pipe is improved by considering more general coupling conditions. We focus on modelling the acoustic properties at the shear layer in general and the stability properties in particular. Experimental methods are used for studying primarily the geometric exit conditions. Both theoretical and experimental results are presented and discussed. Numerical results related to the theory show that the improved modelling causes an expected increase in the magnitude of the reflection coefficient compared to the original Munt's model. The experimental results, on the other hand, show that there are additional effects due to the presence of thick walls at the exit of the straight pipes used in the experiments. These effects are observed to be more dominant than the effects due to the shapes of the edges. Based on the discussions, further theoretical and experimental investigations are proposed.

  • 34.
    Yanaz Cinar, Özge
    et al.
    Eskişehir Osmangazi University, Turkey.
    Boij, Susann
    KTH Royal Institute of Technology.
    Cinar, Gökhan
    Eskişehir Osmangazi University, Turkey.
    Nilsson, Börje
    Linnaeus University, Faculty of Technology, Department of Mathematics.
    Sudden area expansion in ducts with flow: A comparison between cylindrical and rectangular modelling2017In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 396, p. 307-324Article in journal (Refereed)
    Abstract [en]

    The acoustic properties of an area expansion are analyzed for frequencies where flow acoustic interaction may have a significant influence due to flow separation and vortex shedding. It is investigated why this interaction, which is seen in experimental data on a cylindrical duct as a resonance at a particular Strouhal number of order one, is present in rectangular but not in cylindrical modelling that would be expected to be more realistic; both models consider a plug flow. An analytic method that is suitable for identifying possible reasons for the discrepancies between the two geometries is used. The previously published rectangular model is generalized to the cylindrical case and both models are used to simulate results for all elements in the plane wave scattering matrix and for all parameters for which experimental results are available. The comparison between the two models and between models and measured data is thus not restricted to the flow acoustic induced resonance. The results show that the two geometries in general perform equally when compared with the experimental results, but that the rectangular modelling indeed performs better for some cases. This occurs around a critical Strouhal number, and for higher Mach number. Using the analytic form of the solution, it is shown that the observed discrepancy is related to interaction between the damped hydrodynamic mode and a downstream propagating higher order acoustic mode. Such interaction is not present in the corresponding quiescent duct, and is related to the presence of the shear layer. The analysis shows that the structure of the higher order acoustic modes is different for the cylindrical and rectangular case, respectively, causing the difference in resonant behaviour.

1 - 34 of 34
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