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  • 1.
    Fallenius, Bengt E. G.
    et al.
    KTH Mechanics, Stockholm, Sweden.
    Sattari, Amir
    University of Gävle, Gävle, Sweden.
    Fransson, Jens H. M.
    KTH Mechanics, Stockholm, Sweden; University of Gävle, Gävle, Sweden.
    Sandberg, Mats
    University of Gävle, Gävle, Sweden.
    Experimental study on the effect of pulsating inflow to an enclosure for improved mixing2013In: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 44, p. 108-119Article in journal (Refereed)
    Abstract [en]

    Optimal control of inlet jet flows is of broad interest for enhanced mixing in ventilated rooms. The general approach in mechanical ventilation is forced convection by means of a constant flow rate supply. However, this type of ventilation may cause several problems such as draught and appearance of stagnation zones, which reduces the ventilation efficiency. A potential way to improve the ventilation quality is to apply a pulsating inflow, which has been hypothesised to reduce the stagnation zones due to enhanced mixing. The present study aims at testing this hypothesis, experimentally, in a small-scale two-dimensional water model using Particle Image Velocimetry with an in-house vortex detection program. We are able to show that for an increase in pulsation frequency or alternatively in the flow rate the stagnation zones are reduced in size and the distribution of vortices becomes more homogeneous over the considered domain. The number of vortices (all scales) increases by a factor of four and the swirl-strength by about 50% simply by turning on the inflow pulsation. Furthermore, the vortices are well balanced in terms of their rotational direction, which is validated by the symmetric Probability Density Functions of vortex circulation (Γ) around Γ= 0. There are two dominating vortex length scales in the flow, namely 0.6 and 0.8 inlet diameters and the spectrum of vortex diameters become broader by turning on the inflow pulsation. We conclude that the positive effect for enhanced mixing by increasing the flow rate can equally be accomplished by applying a pulsating inflow.

  • 2.
    Hüllmann, Dino
    et al.
    Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany.
    Neumann, Patrick P.
    Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany.
    Lilienthal, Achim J.
    Örebro University, School of Science and Technology.
    Gas Dispersion Fluid Mechanics Simulation for Large Outdoor Environments2019In: 36th Danubia Adria Symposium on Advances in Experimental Mechanics: Extended Abstracts, Pilsen, Czech Republic: Danubia-Adria Symposium on Advances in Experimental Mechanics , 2019, p. 49-50Conference paper (Refereed)
    Abstract [en]

    The development of algorithms for mapping gas distributions and localising gas sources is a challenging task, because gas dispersion is a highly dynamic process and it is impossible to capture ground truth data. Fluid-mechanical simulations are a suitable way to support the development of these algorithms. Several tools for gas dispersion simulation have been developed, but they are not suitable for simulations of large outdoor environments. In this paper, we present a concept of how an existing simulator can be extended to handle both indoor and large outdoor scenarios.

  • 3.
    Kabanshi, Alan
    et al.
    Högskolan Dalarna, Falun, Sweden.
    Sattari, Amir
    Högskolan Dalarna, Byggteknik, Falun, Sweden.
    Linden, Elisabet
    Högskolan Dalarna, Falun, Sweden.
    Wigö, Hans
    Högskolan Dalarna, Falun, Sweden.
    Sandberg, Mats
    Högskolan Dalarna, Falun, Sweden.
    Experimental study on contaminant entrainment in air distribution systems with free jets2017Conference paper (Refereed)
    Download full text (pdf)
    FULLTEXT01
  • 4.
    Kjellander, Manne
    Örebro University, School of Science and Technology.
    Akustisk design av studiorum för musikinspelning2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This project was carried out in collaboration with acoustics specialist Erling Nilsson at Ecophon in Hyllinge, Sweden. The job requester was music producer Magnus Ågren, owner of Flow Music Studios in Malmö. The task was to improve the acoustics in one of the rooms used for recording. Prior to the measures, the sound quality was rather poor with a harsh and unpleasant character. First, the way in which certain acoustic parameters should be affected was defined. Thereafter, measures were suggested with the target values in mind. Evaluating studies later showed that the parameters had been affected in the right direction, though not all of them as much as calculated. The main goal of the acoustic treatment was to add absorption in the middle and high frequencies, and to diffuse the sound waves as much as possible. Acoustic measurements also showed that the room might profit from a little more absorption and diffusion in the low frequencies.

    Download full text (pdf)
    Rapport - Akustisk design av studiorum för musikinspelning
    Download (pdf)
    Bilaga 1 - Ecophon Wall Panel A (produktblad)
    Download (pdf)
    Bilaga 2 - Ecophon Master Solo S (produktblad)
    Download (pdf)
    Bilaga 3 - Mätresultat
  • 5.
    Kucner, Tomasz Piotr
    et al.
    Örebro University, School of Science and Technology.
    Lilienthal, Achim
    Örebro University, School of Science and Technology.
    Magnusson, Martin
    Örebro University, School of Science and Technology.
    Palmieri, L.
    Corporate Research, Robert Bosch GmbH, Renningen, Germany.
    Swaminathan, Chittaranjan Srinivas
    Örebro University, School of Science and Technology.
    Modelling Motion Patterns with Circular-Linear Flow Field Maps2020In: Probabilistic Mapping of Spatial Motion Patterns for Mobile Robots, Springer, 2020, p. 65-113Chapter in book (Refereed)
    Abstract [en]

    The shared feature of the flow of discrete objects and continuous media is that they both can be represented as velocity vectors encapsulating direction and speed of motion. In this chapter, we present a method for modelling the flow of discrete objects and continuous media as continuous Gaussian mixture fields. The proposed model associates to each part of the environment a Gaussian mixture model describing the local motion patterns. We also present a learning method, designed to build the model from a set of sparse, noisy and incomplete observations. 

  • 6.
    Larsson, Tord
    et al.
    Örebro University, School of Science and Technology.
    Kjellander, Johan
    Örebro University, School of Science and Technology.
    Överstam, Henrik
    Örebro University, School of Science and Technology.
    “Aerosoltrap” a new device for inertial dust separation: CFD simulations with experimental validation2013In: Particulate Science and Technology, ISSN 0272-6351, E-ISSN 1548-0046, Vol. 31, no 3, p. 221-225Article in journal (Refereed)
    Abstract [en]

    Inertial separation of dust from air/gas streams using settling- or baffle chambers is simple and cost effective. In order to increase the effectiveness of a single chamber AerosolTrap has been developed. This new device uses 4 chambers in series, stacked on top of each other. The aim of the present study is to examine the performance of AerosolTrap and investigate if CFD simulations can be used as a tool to optimize its geometry. Simulations and validating laboratory experiments have been performed using different flows and different mix of particles. The paper describes the methodology used and presents results that show that CFD simulations predict the general characteristics of the AerosolTrap well but underestimates the separation coefficient slightly.

  • 7.
    Ranjbar, Parivash
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University, School of Science and Technology.
    Signal Processing Methods for Improvement of Environmental Perception of Persons with Deafblindness2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 902, p. 398-404Article in journal (Refereed)
    Abstract [en]

    Environmental perception is a functional area that is severely limited in persons with  deafblindness (DB) who belong a category of people with severe disabilities. Monitor is a vibratory aid developed with the aim to improve environmental perception of persons with DB. The aid consists of a mobile phone with an application connected to a microphone and vibrator. Monitor picks up the sounds produced by events by microphone, processes the sound using an algorithm programmed as an application in the mobile phone and then presents the signal via the vibrator to the persons with DB to be sensed and interpreted. In previous laboratory studies, four algorithms (AM, AMMC, TR, and TRHA) were developed based on modulating, and transposing principles.

    The algorithms were tested by persons with normal hearing/hearing impairment and selected as good candidates to improve vibratory identification of environmental sounds. In this on-going the algorithms are tested by 13 persons with congenital D and five persons with DB using Monitor in a realistic environment, living room, kitchen or office. Forty five recorded environmental sounds were used as test stimuli.

    The subjects tested the algorithms two times, Test and Retest each including a test session

    initiated by a training session. The four algorithms were tested in four days at Test and four days at Retest in total eight test days. Each test day began with a training session where a sound was presented as vibrations to be sensed by the person with the aim to remember its pattern and identity.

    The 45 sounds were grouped in four groups where an specific algorithm was chosen to process an specific sound group in a specific day. At the test session a sound was presented and the person was given 5 randomly chosen sound alternatives to choose the one as represented sound. The algorithms were different for different sound groups during four different test days so all algorithms were used to process all sounds. The algorithms were tested a second time, Retest, in same way as in Test.

    The mean value of identification of environmental sounds varied between 74.6% and 84.0% at Test and between 86.9% and 90.4% at Retest. The identification results at Retest were

    significantly improved (p<0.01) for all algorithms after a relatively short time of training indicating a good learning effect. At Test the algorithm AM was significantly better than the algorithms AMMC and TRHA (p< 0.01) and the algorithm TR was better than TRHA (p<0.01).

    The algorithms AM, AMMC, and TR were selected as good candidates to be implemented in the Monitor to improve environmental perception.

    Download full text (pdf)
    AMR.902.398.pdf
  • 8.
    Sattari, Amir
    Örebro University, School of Science and Technology.
    Effect of Pulsative Inflow to a Small-Scale Room model: CFD Simulation of an Innovative Ventilation Solution2019Conference paper (Refereed)
    Abstract [en]

    In this study, the effects of having a pulsative inflow to a wall jet within a 2-D enclosure are investigated using both (Particle Image Velocimetry (PIV) measurements and Computational Fluid Dynamics (CFD) simulations. The main hypothesis of the study is that the pulsation can improve the mixing performance of the wall jet into the small-scale 2-Droom model. Both CFD and PIV experiments focused on comparison of downstream flow-field of a wall-jet with constant and pulsative inflow modes. 

    Obtained results have proved that the pulsation has the ability to improve mixing thorough generating secondary vortices in the downstream of the wall-jet, and same global airflow pattern exists for both of the cases but with generation of more eddies and local periodical velocity variations for pulsation mode. This periodic generation of turbulence with pulsative inflo9w has happened despite the relatively low Reynolds numbers. The bigger size of boundary layer and higher turbulent kinetic energy for the pulsative inflow in comparison with the same flow rate in constant flow mode could result in more ventilation effectiveness without the need to increase flow rate. When itcomes to real-scale ventilation applications, a lower pulsated inflow could produce the same acceptable results in terms of mixing efficiency as a higher constant flow rate, which results in a more energy-efficient ventilation strategy with lower risk of draught and thus better thermal comfort. The computational is done thorough grid independency study.

    The study is therefore done with 3D SST-kΩ which yielded good prediction of velocity profiles near walls. For predicting turbulence parameters in the center of the domain SAS has been used which has been successful to get close toreality results.

  • 9.
    Sundberg, Daniel
    Örebro University, Department of Technology. Örebro University, School of Science and Technology.
    HANDSFREE-ENHET FÖR MOBIL TRYGGHETSTELEFON2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Cnior Mobile AB i Lindesberg utvecklar en mobil trygghetstelefon för äldre. Detta examensarbete går ut på att utforma en handsfree-enhet för denna. Handsfree-enheten ska integreras i larmknappen, som bärs av användaren runt handleden, och har kontakt med telefonen via blåtandsradio. I examensarbetet ingår att välja ut lämplig högtalare och mikrofon, hitta lösningar för smuts- och vattentålighet samt att lösa problem med ekon och bakgrundsstörningar.

    En högtalare hittades som uppfyllde kraven för smuts- och vattentålighet samtidigt som den hade utmärkt frekvensgång för återgivning av tydligt tal. Vattenavrinning från högtalaren löstes genom att ett sinussvep sänds ut från högtalaren varje gång ett samtal ska kopplas upp. På så sätt pressar ljudtrycket ut vattnet från handledsknappens kavitet. Olika utformningar av ljudhålen i handledsknappens skal provades. Den bästa lösningen för vattenavrinningen var att använda sju stycken runda hål med 1,3 mm i diameter. En ljudtrycksmätning säkerställde att ljudtrycket inte blev lidande av denna utformning av ljudhålen.

    Ekosläckning och bakgrundsstörningsundertryckning sköts av GSM-modulen i trygghetsmobilen. I ekosläckningens manual finns beskrivet hur ekosläckningens 24 parametrar kan justeras för att passa olika applikationer. Endast en mindre ändring av de rekommenderade parametervärdena behövdes för att ekosläckning och bakgrundsstörningsundertryckning skulle fungera tillfredställande.

    Eftersom mikrofonernas datablad visade på så snarlika egenskaper överlämnades mikrofonvalet till företaget, då det kan vara klokt att låta priset avgöra.

    Download full text (pdf)
    FULLTEXT01
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