Дисертації з теми "Duct wall"
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Slabaugh, Carson. "HEAT TRANSFER AUGMENTATION IN A NARROW RECTANGULAR DUCT WITH DIMPLES APPLIED TO A SINGLE WALL." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2172.
M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering MSME
Krishnan, Vaidyanathan. "The nature of Turbulence in a Narrow Apex Angle Isosceles Triangular Duct." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3811.
Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering PhD
He, Long. "A Study of Immersed Boundary Method in a Ribbed Duct for the Internal Cooling of Turbine Blades." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78069.
Master of Science
Kandindi, Muteba. "Heat transfer and pressure drop investigation for prescribed heat fluxes on both the inner and outer wall of the annular duct." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/61299.
Dissertation (MSc)--University of Pretoria, 2016.
Mechanical and Aeronautical Engineering
MSc
Unrestricted
Myers, Jeremy. "Computational Fluid Dynamics in a Terminal Alveolated Bronchiole Duct with Expanding Walls: Proof-of-Concept in OpenFOAM." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/5011.
Jamois, Alexis. "Modélisation et réalisation d'absorbants acoustiques par impression 3D : étude en incidence normale et application au traitement d'un conduit." Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0010.
Conventional rigid porous materials such as wools or foams do not provide effective absorption at low frequencies in complex industrial environments. For these applications, the structures developed are generally quarter-wave resonators or Helmholtz resonators. In recent years, 3D printing techniques have made it possible to produce resonator geometries that were previously difficult to produce. The ease of use and affordability of these techniques means that it is now possible to create tailor-made absorbing devices to meet specific requirements very quickly. This long-term objective requires, on the one hand, validation of the reliability of the dimensions obtained during the production of absorbent structures and, on the other hand, the ability to effectively model a variety of geometries in different contexts. In this thesis, stereolithography was chosen to print the samples based on literature results. Studies have concluded that it is more accurate for acoustic devices than other techniques. The geometry chosen for this study consists in a stack of volumes (spherical or cubic), connected in the three directions of space by channels in the image of cubic crystals. A large number of samples were manufactured varying the production parameters in order to measure the variability of the characteristic dimensions of the samples. Among the various modelling approaches presented, the numerical tests carried out led to the choice of equivalent fluid modelling based on the identification of JCAPL parameters. They are identified in a representative volume homogenised throughout the sample. This homogenisation of behaviour is suited to the geometries studied because of their periodic nature. The reaction of the geometries we are considering makes impedance modelling impossible. The samples are first studied at normal incidence, in order to link the variability of realisation to the measured acoustic behaviour. The measurement results and the predictions are in good agreement. Some samples were made specifically for duct wall measurement, in order to validate the use of the equivalent fluid approach. These tests were also used to confirm the conclusions drawn for normal incidence. The variability of the geometry has a real impact on the acoustic behaviour, but the main problem with rigid 3D printed samples is their adaptation to the measurement benches
AIT, ALDJET BOUHADEF KHEDIDJA. "Evaporation d'eau entre plaques parallèles humides sous l'effet d'un écoulement d'air en convection forcée : application à l'évaluation des transferts couplés de chaleur et de masse." Poitiers, 1988. http://www.theses.fr/1988POIT2009.
Eames, Ian. "Displacement of material by a solid body moving away from a wall." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362975.
Walgode, Vitor. "Analysis and design of rectangular ducts with thin walls." Thesis, The University of Sydney, 1992. https://hdl.handle.net/2123/26742.
Sebastian, Robin. "Numerical simulation of acoustic propagation in a turbulent channel flow with an acoustic liner." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2297/document.
Acoustic liners are a key technology in aeronautics for the passive reduction of the noise generated by aircraft engines. They are employed in a complex flow scenario in which the acoustic waves, the turbulent flow, and the acoustic liner are interacting.During this thesis, in a context of high performance computing, a compressible Navier-Stokes solver has been developed to perform implicit large eddy simulations of a model problem of this interaction: a turbulent plane channel flow with one wall modeled as an impedance condition.As a preliminary step the wall-turbulence in rigid channel flows and associated large-scale motions are investigated. A straightforward algorithm to detect these flow features is developed and the effect of compressibility on the flow structures and their contribution to the drag are studied. Then, the interaction between the acoustic liner and turbulent flow is investigated assuming periodicity in the streamwise direction. It is shown that low resistance and low resonance frequency tend to trigger flow instability, which modifies the conventional wall-turbulence and also results in drag increase.Finally, the simulation of a spatial channel flow was addressed. In this case no periodicity is assumed and an acoustic wave can be injected at the inlet of the domain. The effect of turbulence on sound attenuation is studied without liner, before a liner is introduced on a part of the channel bottom wall. In this more realistic case, it is confirmed that low resistance acoustic liners trigger an instability at the leading edge of the liner, resulting in drag increase and excess noise generation
Gottmann, Matthias 1964. "Local wall shear stress and interface behavior of adiabatic air-water flows in rectangular ducts." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282445.
Sebastian, Robin. "Numerical simulation of acoustic propagation in a turbulent channel flow with an acoustic liner." Electronic Thesis or Diss., Poitiers, 2018. http://www.theses.fr/2018POIT2297.
Acoustic liners are a key technology in aeronautics for the passive reduction of the noise generated by aircraft engines. They are employed in a complex flow scenario in which the acoustic waves, the turbulent flow, and the acoustic liner are interacting.During this thesis, in a context of high performance computing, a compressible Navier-Stokes solver has been developed to perform implicit large eddy simulations of a model problem of this interaction: a turbulent plane channel flow with one wall modeled as an impedance condition.As a preliminary step the wall-turbulence in rigid channel flows and associated large-scale motions are investigated. A straightforward algorithm to detect these flow features is developed and the effect of compressibility on the flow structures and their contribution to the drag are studied. Then, the interaction between the acoustic liner and turbulent flow is investigated assuming periodicity in the streamwise direction. It is shown that low resistance and low resonance frequency tend to trigger flow instability, which modifies the conventional wall-turbulence and also results in drag increase.Finally, the simulation of a spatial channel flow was addressed. In this case no periodicity is assumed and an acoustic wave can be injected at the inlet of the domain. The effect of turbulence on sound attenuation is studied without liner, before a liner is introduced on a part of the channel bottom wall. In this more realistic case, it is confirmed that low resistance acoustic liners trigger an instability at the leading edge of the liner, resulting in drag increase and excess noise generation
Hussmo, Daniel. "Dammhantering vid väggsågning." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Produktutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-35033.
Wall sawing in concrete generates a lot of dust. The dust is partly collected by the water that is applied as a coolant for the blade, which leads to a mixture called ”slurry”. The slurry as well as the dust needs to be removed after the sawing has been completed, which adds extra steps to the process for the user of the saw. The biggest issue here is the dust that is inhaled by the user, which can lead to diseases such as silicosis . This will probably lead to new regulations regarding how dust is managed, which has been the background of this thesis. The purpose of this study is therefore to evaluate how dust and slurry can be collected during wall sawing. The problem in wall sawing compared to other forms of processing of concrete is the difficulty in creating a seal towards the surface where the processing is being executed. It is for instance easier to create a sealed space around the are of processing during drilling where you can create a vacuum to collect the dust and slurry. An observation was conducted in order to give a basis for how the dust and slurry is acting during sawing. A case study was also executed to gather data regarding how the problem is solved today in the industry as well as to provide intel regarding important attributes that concepts must have in order to be considered attractive to the industry. Concepts were generated with the collected data as a base through brainstorming and morphology. The concepts were evaluated together with Husqvarna as well as with pugh’s matrix, where the set of criterias had been collected from the case study. The result was a slide on unit that locks to existing geometries and collects dust and slurry at the point where the biggest concentration is achieved during sawing. After the evaluation, a prototype was constructed in order to verify that dust and slurry could be collected and to measure the efficiency of the concept. The result of the test was that the prototype could collect approximately 23% of the slurry as well as significantly reduce the amount of visible dust. The concept could thereby fulfil the purpose of the study, especially regarding the decreasion of dust since the harmful effects of inhalation could be reduced.
Candanedo, Ibarra José A. "Time-mean wall static pressure distributions and module friction factors for spatially periodic fully developed flows in interrupted-plate rectangular ducts." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80002.
Gorin, S. Steven. "Control of the effects of wind, sand, and dust by the citadel walls, in Chan Chan, Peru." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53698.
PH. D.
Chovet, Rogelio. "Caractérisation expérimentale et numérique du comportement rhéologique d'un fluide complexe : application à une mousse en écoulement dans un canal horizontal droit avec et sans singularités." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0021/document.
This work is an experimental and numerical study of aqueous foam flow inside a horizontal square duct, with and without flow disruption devices (fdd). It is especially devoted to determine the pertinent parameters of the flow: longitudinal pressure losses, velocity fields of foam flow near the walls, liquid film thickness (thick and thin), and the wall shear stress evolution, for an aqueous foam with a void fraction range between 55 and 85%, for a mean foam flow velocity of 2, 4 and 6 cm/s. Once they were determined, inside the horizontal channel, we carried out measurements over different geometries: half-sudden expansion, vertical fence and foam flow around a cylinder. The goal was to study the foam flow reorganization to well understand the rheological behavior of aqueous foam flow in the vicinities of different fdd. Finally, a numerical simulation (CFD), using the Bingham behavior model of non-Newtonian fluid, was undertaken to test its capacity to represent the aqueous foam flow inside the horizontal duct with flow disruption devices. First of all, we verified the static longitudinal pressure evolution, which varies linearly upstream and downstream far from the fdd. The singular pressure loss remains constant for a given mean foam velocity and a foam quality (void fraction). From the Particle Imaging Velocimetry (PIV) technique (2D), we determined the two velocity components in the immediate vicinities of the disruption devices. They allowed us to put into evidence the different foam flow regimes and to observe the foam flow reorganization and rheological behavior through the studied fdd. The slip-layer thickness analysis, obtained using the conductimetry method, shows that the wall presents a liquid film thick enough to apply an electrochemical technique (polarography). Thus, the polarographic signals, obtained for the foam flow, present important fluctuations. They were compared to the wall shear stress deducted from the measurement of pressure losses, showing a good similarity between them. The numerical study (CFD), carried out for aqueous foam flow with a void fraction of 70% and a mean foam flow velocity of 2 cm/s, shows that the Bingham rheological model can be adapted to this kind of aqueous foam flow which is flowing like a block
Weckmann, Armin. "Material migration in tokamaks: Studies of deposition processes and characterisation of dust particles." Licentiate thesis, KTH, Fusionsplasmafysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-178026.
QC 20151203
Dutt, Anne J. [Verfasser], and Hans-Werner [Akademischer Betreuer] Wahl. "Subjective Aging Experiences and Negative Affectivity: Examination of Fundamental Associations and of Underlying Pathways / Anne Josephine Dutt ; Betreuer: Hans-Werner Wahl." Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177385473/34.
Saad, Tony. "Theoretical Models for Wall Injected Duct Flows." 2010. http://trace.tennessee.edu/utk_graddiss/748.
Hwa, Chang Shu, and 張淑華. "Study on the Wall Vibration Produced by the Acoustic Propagation through a Duct." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/32417943484507369127.
國立臺灣大學
造船及海洋工程學研究所
89
This study is mainly intended to the determination on the wall vibration of duct, which is produced by the acoustic wave propagation through it. Therefore, the sound pressure in a steel duct is measured first. And then regarding the result as the required excited force to the other ducts else. Furthermore, some thin-shell ducts with materials iron, aluminum and plastics are selected to be the elastic ducts for this study. In the mean time, the resulting vibration for each elastic duct is calculated when excited by the same acoustic field as that obtained from the case for steel duct. From the viewpoint of energy conservation, the energy loss of an actual duct while in vibration due to its internal damping must equal the difference of acoustic power output at entrance from that at exit. Two acoustic power outputs can be measured by sound intensity method. The result as obtained clearly shows the predicted vibrations of elastic ducts are quite agreeable with that of measurement. Thereafter, the empirical formula developed from energy loss viewpoint can be used in some acceptable accuracy to predict the vibration of duct when acoustic waves propagate through it at low frequency. Upon the assumption as above, the law of energy conservation tells that the acoustic energy difference of the acoustic power of source from that at the exit of duct must equal the damping power efflux produced by the duct vibration. Therefore in mathematical expression, if we let the damping force of duct wall be equal to , the related damping power efflux will be , where U is the velocity amplitude, and . So forth the conservation of acoustic energy shows: where are, respectively, the acoustic intensities at source and exit. r, L are the radius and length of duct respectively. Since for single frequency sound, the amplitude A of wall vibration can be obtained as:
Chen, Tsung-Chih, and 陳宗志. "Active Control on the Acoustic Fields in Duct Using the Wall-Vibration Induced Acoustic Sources." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/78329946878278244270.
國立臺灣大學
工程科學及海洋工程學研究所
97
There are two techniques in noise control,which are passive and active noise control.This thesis is to provide another approach to active noise control(ANC).It is to use a piezoelectric transducer(PZT) to excite the duct wall.The wall-vibration induced feedback sound wave can combine with primary noise to reduce the downstream sound pressure.Accordingly,only a duct and a piezoelectric tr- ansducer are wanted in this approach.Thus the cost and the space required for the apparatus to be wanted are saved much more. In experiment,we use a FIR digital filter as the main structure of the control system and meanwhile take a single-frequency or a dual-frequency signal as the reference input directly produced by a function generator.Weighting coefficients of the digital filter are adjusted by using LMS algorithm in order to achieve the best performance.Besides,the sound radiation by vibrating an infinite cylindrical shell will be analyzed. The result of this study shows great attenuation of downstream sound pressure level by about 40 dB will be obtained at some frequencies.Similar situation occurs for dual frequencies at which greater radiation from duct wall exists,the attenuation of downstream sound pressure levels by about 15~35dB is obtained.The actuality as discussed can demonstrate it is feasible to use wall-vibration induced source to adaptively active control on the sound transmissi- on in a circular duct.
You, Chuan-bei, and 游川倍. "Experimental Study on the Performance of Sudden Expansion Silencer with Inner Baffle-Wall and Connnecting Duct." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/88445846136011392701.
國立中興大學
機械工程學系
86
This study investigates the performance of sudden expansion silencer with internal baffle-wall and connecting duct in relation to some design parameters. Such parameters are the length and the asymmetry of input and output ducts, the length and height of the connecting duct as well as the porosity ratio. The inflow frequency ranges from 10Hz to 120Hz. The evaluation is based on the magnitude of pressure variation within and sound level measurement downstream of the silencer . Frequency responses of both pressure variation and the sound level are coincident for frequency lower than 100Hz. However, deviation arises for frequency higher than 100Hz because of the presence of small scale eddy in the exhaust jet. Large porosity ratio can eliminates the noise level at low frequency range. Noise reduction is significant while the internal baffle-wall is inserted. Besides, the longer the connecting duct, the more reduction of the sound level. The height of the connecting duct determines the passage of energy at lower frequency. Thus, small height of the connecting duct can reduce effectively the sound level at low frequency range, and vice versa. Furthermore, longer inlet duct can increase the sound level at frequency higher than 100Hz. On the other hand, the longer outlet duct will decrease the resonant frequency of the flow tone inside the silencer. In the limiting case of no tail duct, the resonant frequency locates beyond 120Hz and the sound level is high within 00z In gnraly, h betperormne o nis reutio ca e atane ifthe veticl bfle-al i intlle isie teasymeti siener Beies, smaller eghtofth conctig uc an uitblelngt o te ilt ad utet ducts cn hlp olocteth reoantfreuncyofth flwton inie tesilencer Hihporsiy ati an lsob faoabl torduc te oun eve atlow frquecyrage.Keyword: suden xpnson iencr、aflewal Bconctig duc、orsit ati
Chen, Jiann Liang, and 陳建良. "Experimental Study of Convective Heat Transfer in a Radially Rotating Square Duct with Uniform Wall Heat Flux and Inward Flow." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/80870383751185376599.
Rodrigues, Sylvie Vaz. "Calibração de sondas do tipo Irwin em condições de gradiente de pressão nulo." Master's thesis, 2016. http://hdl.handle.net/10316/38832.
O principal objetivo deste trabalho é a calibração de sondas do tipo Irwin (1980) quando utilizadas em condições de gradiente pressão nulo. De modo a atingir este objetivo, foram realizados ensaios laboratoriais utilizando uma conduta de secção transversal rectangular, com cinco metros de comprimento, acoplada a um ventilador radial, onde foram colocadas sondas de pressão estática e as sondas de tensão parietal. Esta conduta tem como particularidade um tecto móvel que permite configurar diversas relações largura- altura (L:H). Testaram-se diversos caudais de ar, variando a área de obstrução do ventilador. Registou-se a distribuição de pressão ao longo da conduta de modo a identificar a zona de escoamento desenvolvido, local onde são colocadas as sondas para calibração. Com base na queda de pressão, pode-se então determinar o fator de atrito e correspondente tensão parietal. De modo a poder relacionar o escoamento no interior de uma conduta rectangular com o escoamento no interior de condutas circular, foi utilizado um parâmetro característico chamado de diâmetro hidráulico, por forma a comparar os resultados de conduta rectangular com valores de condutas circulares. Utilizando como referência os valores de pressão, medidos nas tomadas de pressão estática, fez-se o cálculo da tensão parietal, e foram então calibradas as sondas para medição de tensão parietal relacionando a diferença de pressão, em cada sonda, com os valores de tensão parietal calculados. Os maiores desvios, em relação à tensão parietal medida, foram observados para os caudais mais baixos.
The main objective of this work is to calibrate type Irwin probes (1980) when used in zero gradient conditions. In order to achieve this objective laboratory tests were carried out using a rectangular cross section duct with five meters long, coupled to a radial fan, where were placed static pressure probes and wall shear stress probes. This duct has the particularity of a mobile roof that allows to configure various relations length-height (L: H). Several airflows rates were tested, by varying the fan blockage area. The pressure distribution along the duct was measured to identify the area of developed flow, where the probes are placed for calibration. Based on the pressure drop, were determined the corresponding friction factor and wall shear stress. In order to relate the flow within a rectangular duct with the flow inside circular ducts, a parameter called hydraulic diameter was used in order to compare the results of rectangular duct with circular ducts values. Using as reference pressure values measured in static pressure taps, the wall shear stress was calculated, and then were calibrated probes for wall shear stress measurement relating the pressure difference in each probe, to the wall shear stress values calculated. The largest deviation in relation to the measured wall shear stress has been observed to lower flowrates.
Whitelonis, Nicholas John 1984. "Investigation of high-frequency propagation channels through pipes and ducts for building interior reconnaissance." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-05-5651.
text
Chiang, Yu Wei, and 蔣有為. "Experimental Study on Heat Transfer in Square Ducts with One- Porous-Wall Suction." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/06960831289873566200.
Cheng, Yaw Chung, and 鄭耀宗. "Theoretical and Experimental Study on Laminar Flow and Heat Transfer in One-Porous-Wall Ducts." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/24505119407195943575.
黃成瑋. "Numerical Calculations of Heat Transfer and Friction Characteristic in Rectangular Ducts with Slit and Solid Ribs Mounted on One Wall." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/33386057453239936113.
國立成功大學
機械工程學系
88
This study presents the numerical calculation on turbulent heat transfer, fluid flow and friction characteristics comparison in rectangular ducts with slit ribs, solid ribs mounted on one wall and smooth duct. The turbulent governing equations are solved by a Control-Volume-based finite-difference method with power-law scheme and the well know k-εturbulence model and its associate wall function to describe the turbulent structure. The velocity and pressure terms of momentum equations are solved by SIMPLE (Semi-Implicit Method for Pressure-Linked Equation) method. An orthogonal, non-uniform, staggered grids are used for the establishment of mesh grids. The parameters studied include the entrance flow Reynolds number (Re=8000、15000、33000、58000) and rib void fraction (b=0.211、0.307、0.489); whereas the rib height-to-duct hydraulic diameter is fixed at 0.167 (H/De=0.167) and the working medium is air. The flow field numerical calculations indicate that the flow patterns around the slit rib and solid rib are different due to the different transport phenomena and it also influences the heat transfer. At the same Reynolds number, the recirculation phenomena that existed behind the solid rib disappears in the corresponding region of the slit rib. Relative to solid rib duct, the slit rib has a lower friction factor owing to less duct blockage. As to the heat transfer effect, both the solid rib and slit rib walls enhanced the heat transfer as compared with the smooth duct, because both the solid rib or slit rib are the mechanisms of heat transfer augmentation. With greater turbulence-mixing effect, the slit-ribbed geometry provides better heat transfer than solid-ribbed geometry. In addition, the slit rib has a more significant fin effect than the solid rib due to its larger heat transfer surface area.
Sun, Yi-Shin, and 孫臆勛. "A Study on Stains on External Building Wall Due to Dust and Rainfall─Effects of Surface Roughness and Angle Factors." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/50716473072749017917.
國立成功大學
建築學系碩博士班
90
The issue of building material’s durability has been taken seriously in recent years. The most noticeable among all kinds of deteriorations is the external building walls being soiled by its surrounding environmental factors, but it is always ignored. However, there is no standard test method available for accessing the dust pollution on external walls in Taiwan. The stain-resistance of wall materials can neither be quantitatively determined nor further analyzed. Thus several Japanese researches and standards were reviewed in this study in order to suggest an experimental method to observe the staining. It is expected to understand more about how the external wall materials are stained by dust and rainfall. The adhesion of dust to wall materials can be influenced by dozens of factors. The dirty surface flow and the cleansing ability of the rainfall can be influenced by many factors as well, including rainfall intensity and the contours of the external walls. Several important factors were selected for experiment according to an investigation and some literature. They are “angles” and “surface roughness” of the external wall panels. The result of the experiment tells that the way it stains differs with the angles and surface properties of the panels. The stains are more severe on flatter panels or rougher materials. The different degree of soiling can be attributed to the adhesion of dry dust, the cleansing ability of the rainfall, and the surface flow which brings dust or takes it off.