Dissertations / Theses on the topic 'Wall suction'
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Heidarpour, Manouchehr. "Turbulent flow in a porous tube with wall suction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq28345.pdf.
Full textChoudhari, Meelan 1963. "Boundary layer receptivity at a suction surface-hard wall junction." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277030.
Full textBobke, Alexandra. "Simulations of turbulent boundary layers with suction and pressure gradients." Licentiate thesis, KTH, Linné Flow Center, FLOW, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185275.
Full textQC 20160418
Khapko, Taras. "Transition to turbulence in the asymptotic suction boundary layer." Licentiate thesis, KTH, Stabilitet, Transition, Kontroll, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141344.
Full textQC 20140213
Avsarkisov, Victor [Verfasser], Martin [Akademischer Betreuer] Oberlack, and Suad [Akademischer Betreuer] Jakirlić. "Turbulent Poiseuille Flow with Uniform Wall Blowing and Suction. / Victor Avsarkisov. Betreuer: Martin Oberlack ; Suad Jakirlic." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2013. http://d-nb.info/1110792190/34.
Full textTilton, Nils Guillaume. "The effects of wall permeability on the linear stability of channel flow and the asymptotic suction boundary layer." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86673.
Full textIn the second part of this thesis, we study the effects of wall permeability on the linear stability of the asymptotic suction boundary layer developed over a rigid, homogeneous, isotropic, porous plate. For this purpose, we propose a new approach to modeling wall suction. The porous plate is bounded above by a semi-infinite fluid region in which a boundary layer is driven by a constant free-stream velocity and pressure. The porous plate is bounded below by a semi-infinite plenum chamber maintained at a constant suction pressure lower than the free-stream pressure. The difference in pressure drives a constant suction through the porous plate. We consider both a temporal and spatial fully coupled linear stability analysis of the flow fields in the boundary layer, porous layer, and plenum chamber. As in the first part of the thesis, we constrain the study to porous materials of small permeability in which inertial effects may be neglected. We find that small amounts of wall permeability destabilize the Tollmien-Schlichting wave and cause the critical Reynolds number to decrease to less than 20% the value which is predicted by previous studies of the ASBL. We perform a parametric study in which we vary the permeability and depth of the porous layer, the Reynolds number, the streamwise wavenumber of temporal disturbances, and the frequency of spatial disturbances. We compare our results with previously published theoretical and experimental studies. We use our model to find the optimal operating conditions which minimize the skin friction drag and the power required to apply the suction.
Nous étudions l'action des parois poreuses sur la stabilité linéaire de deux écoulements classiques. Dans la première partie de cette thèse, nous considérons un écoulement laminaire qui évolue dans un canal plan délimité par deux parois rigides, à porosité homogène et isotrope. Nous limitons cette étude aux matériaux à faible perméabilité au sein desquels le fluide a une faible vitesse et pour lesquels les effets inertiels peuvent ainsi être négligés. Nous réalisons l'analyse de stabilité linéaire des différents écoulements qui evoluent dans le canal et dans les régions poreuses adjacentes. Pour cela, nous modulons quatre paramètres caractéristiques des parois: la perméabilité, la porosité, l'épaisseur, et un coefficient associé aux échanges de quantité de mouvement aux interfaces entre le canal et les parois poreuses. Nous décrivons les mécanismes qui interagissent sur la stabilité de l'écoulement. Pour la plupart des paramètres sélectionnés, nous observons que les parois ont un effet déstabilisant significatif et que le nombre de Reynolds critique s'en trouve considérablement reduit. Ainsi, dans les cas extrêmes, la valeur du nombre de Reynolds critique peut être de l'ordre de 10% de celle obtenue avec un écoulement Poiseuille classique. Toutefois, nous observons également que pour des configurations particuliéres, les parois poreuses peuvent avoir un rôle stabilisateur. Nos résultats sont comparés à des études numériques et expérimentales précédemment publiées.
Dans la seconde partie de cette thèse, nous étudions la stabilité linéaire d'une couche limite développée sur une plaque plane, rigide, à porosité homogène et isotrope, et à travers laquelle une aspiration est maintenue constante. Nous proposons une nouvelle approche pour modéliser l'aspiration pariétale. La plaque est située entre deux régions semi-infinies. Au-dessus de la plaque, évolue une couche limite dans laquelle la pression ambiante demeure constante, et au-dessous, existe une chambre d'aspiration dans laquelle la pression est maintenue inférieure à cette pression ambiante. C'est cette différence de pression qui entraîne une aspiration au travers de la plaque. Comme dans la première partie de cette thèse, nous limitons l'étude aux parois à faible perméabilité pour lesquelles les effets inertiels peuvent être négligés. Nous réalisons l'analyse de stabilité linéaire des différents écoulements qui evoluent au-dessus, au-dessous, et au sein de la plaque poreuse. Nous observons que la perméabilité pariétale et la chambre d'aspiration ont un effet déstabilisant significatif. La valeur du nombre de Reynolds critique peut ainsi être de l'ordre de 20% de celle reportée dans des études précédemment publiées et qui ignorent les effets dûs à la perméabilité. Nous proposons un modèle pour déterminer les conditions d'opération optimales de telle sorte que le frottement pariétal et l'alimentation nécessaire à maintenir une aspiration constante soient minimisés.
Levin, Ori. "Numerical studies of transtion in wall-bounded flows." Doctoral thesis, KTH, Mechanics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-546.
Full textDisturbances introduced in wall-bounded flows can grow and lead to transition from laminar to turbulent flow. In order to reduce losses or enhance mixing in energy systems, a fundamental understanding of the flow stability and transition mechanism is important. In the present thesis, the stability, transition mechanism and early turbulent evolution of wall-bounded flows are studied. The stability is investigated by means of linear stability equations and the transition mechanism and turbulence are studied using direct numerical simulations. Three base flows are considered, the Falkner-Skan boundary layer, boundary layers subjected to wall suction and the Blasius wall jet. The stability with respect to the exponential growth of waves and the algebraic growth of optimal streaks is studied for the Falkner-Skan boundary layer. For the algebraic growth, the optimal initial location, where the optimal disturbance is introduced in the boundary layer, is found to move downstream with decreased pressure gradient. A unified transition prediction method incorporating the influences of pressure gradient and free-stream turbulence is suggested. The algebraic growth of streaks in boundary layers subjected to wall suction is calculated. It is found that the spatial analysis gives larger optimal growth than temporal theory. Furthermore, it is found that the optimal growth is larger if the suction begins a distance downstream of the leading edge. Thresholds for transition of periodic and localized disturbances as well as the spreading of turbulent spots in the asymptotic suction boundary layer are investigated for Reynolds number Re=500, 800 and 1200 based on the displacement thickness and the free-stream velocity. It is found that the threshold amplitude scales like Re^-1.05 for transition initiated by streamwise vortices and random noise, like Re^-1.3 for oblique transition and like Re^-1.5 for the localized disturbance. The turbulent spot is found to take a bullet-shaped form that becomes more distinct and increases its spreading rate for higher Reynolds number. The Blasius wall jet is matched to the measured flow in an experimental wall-jet facility. Both the linear and nonlinear regime of introduced waves and streaks are investigated and compared to measurements. It is demonstrated that the streaks play an important role in the breakdown process where they suppress pairing and enhance breakdown to turbulence. Furthermore, statistics from the early turbulent regime are analyzed and reveal a reasonable self-similar behavior, which is most pronounced with inner scaling in the near-wall region.
Gao, Tian. "Direct Strength Method for the Flexural Design of Through-Fastened Metal Building Roof and Wall Systems under Wind Uplift or Suction." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28553.
Full textPh. D.
Ferro, Marco. "Experimental study on turbulent boundary-layer flows with wall transpiration." Doctoral thesis, KTH, Mekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217125.
Full textGenom att använda sig av genomströmmande ytor, med sugning eller blåsning, kan man relativt enkelt och effektivt påverka ett gränsskikts tillstånd. Genom sin potential att påverka olika strömningsfysikaliska fenomen så som att senarelägga både avlösning och omslaget från laminär till turbulent strömning (genom sugning) eller som att exempelvis minska luftmotståndet i turbulenta gränsskikt och ge kyleffekt (genom blåsning), så har ett otaligt antal studier genomförts på området de senaste decennierna. Trots detta så är den grundläggande förståelsen bristfällig för de strömningsfenomen som inträffar i turbulenta gränsskikt över genomströmmande ytor. Det råder stora meningsskiljaktigheter om de mest elementära strömningskvantiteterna, såsom medelhastigheten, när sugning och blåsning tillämpas även i det mest förenklade gränsskiktsfallet nämligen det som utvecklar sig över en plan platta utan tryckgradient. För att ta fram nya experimentella data på gränsskikt med sugning och blåsning genom ytan så har vi designat en ny experimentell uppställning samt tagit den i bruk.Den genomströmmande ytan spänner över hela bredden av vindtunnelns mätsträcka (1.2 m) och är 6.5 m lång i strömningsriktningen och är därmed betydligt längre än vad som använts i tidigare studier. Detta gör det möjligt att bättre utforska gränsskiktet som utvecklas över ytan i strömningsriktningen. Kvaliteten på den experimentella uppställningen och valda mätprocedurerna har verifierats genom omfattande tester, som även inkluderar benchmarking mot tidigare resultat på turbulenta gränsskikt utan tryckgradient eller blåsning/sugning och på laminära asymptotiska sugningsgränsskikt. De experimentella resultaten på turbulenta gränsskikt med sugning bekräftar för första gången att det är möjligt att experimentellt sätta upp ett turbulent asymptotiskt sugningsgränsskikt där gränsskiktets medelhastighetsprofil blir oberoende av strömningsriktningen och där sugningshastigheten utgör den enda kontrollparametern. Det turbulenta asymptotiska sugningsgränsskiktet visar sig ha en medelhastighetsprofil normalt mot ytan med en lång logaritmisk region och utan förekomsten av en yttre vakregion. Om man använder yttre skalning av medelhastigheten, med friströmshastigheten och gränsskiktstjockleken som karaktäristisk hastighet respektive längdskala, så kan det logaritmiska området beskrivas med en lutning på Ao=0.064 och ett korsande värde med y-axeln på Bo=0.994, som är oberoende av sugningshastigheten. Om sugningshasigheten normaliserad med friströmshastigheten överskrider värdet 3.70x10^-3 så återgår det ursprungligen turbulenta gränsskiktet till att vara laminärt. Sugningen genom väggen dämpar hastighetsfluktuationerna i gränsskiktet med upp till 50-60% vid direkt jämförelse av det inre toppvärdet i ett turbulent gränsskikt utan sugning och vid jämförbart Reynolds tal. Denna minskning av turbulent aktivitet verkar härstamma från en ökad stabilitet av hastighetsstråken närmast ytan. Mätningar på turbulenta gränsskikt med blåsning har genomförts för blåsningshastigheter mellan 0.1 och 0.37% av friströmshastigheten och täcker Reynoldstalområdet (10-36)x10^3, med Reynolds tal baserat på rörelsemängds-tjockleken. Vid blåsning genom ytan får man en stark modifiering av formen på hastighetesfördelningen genom gränsskiktet. När blåsningshastigheten ökar så kommer till slut den logaritmiska regionen av medelhastigheten, karaktäristisk för turbulent gränsskikt utan blåsning, att gradvis försvinna. God överens-stämmelse av medelhastighetsprofiler mellan turbulenta gränsskikt med och utan blåsning erhålls för alla Reynoldstal och blåsningshastigheter när profilerna normaliseras med Zagarola-Smits hastighetsskala. Blåsning vid väggen ökar intensiteten av hastighetsfluktuationerna, speciellt i den yttre regionen av gränsskiktet. Vid riktigt höga blåsningshastigheter och Reynoldstal så kommer den yttre toppen av hastighetsfluktuationer i gränsskiktet att överskrida den inre toppen, som i sig gradvis försvinner.
QC 20171101
Gan, Subhadeep. "Active Separation Control of High-Re Turbulent Separated Flow over a Wall-Mounted Hump using RANS, DES, and LES Turbulence Modeling Approaches." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1275924069.
Full textRocha, Melina Freitas. "Influência do perfil de sucção em obras de contenção em solos não saturados." Universidade Federal de Goiás, 2013. http://repositorio.bc.ufg.br/tede/handle/tede/4433.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The need for the use of structures retaining wall have been increasingly used in engineering works. The valuation of soil use has led to wide-ranging exploration of the subsoil, resulting in large excavations that change the equilibrium state of the soil. The performance and design of retaining wall require a good understanding of the stress state of the soil, soil-structure interaction and varying the saturation of soil during construction and useful life. The useful life of retaining wall must ensure stability, functionality and durability. The analysis of soilstructure interaction becomes important by the fact that the same structure subjected to the same external load, presents support reactions that vary with the particular conditions of the mass of soil in which it lies. Therefore the study of soil-atmosphere interaction is an essential factor for unsaturated soils. In order to evaluate the influence of suction on structural design in balance were simulated real conditions of rainfall in three different soils for three excavations (3, 6 e 9 m) and inciciais different conditions N.A. It was observed that the behavior of the suction profile is inwardly related to the parameters as well as saturated and unsaturated soil each, with the intensity and duration of precipitation. Through the theory of earth pressure Rankine for saturated soils, the formulation was developed to calculate the active and passive earth pressure into account the unsaturated soil for three different behaviors of suction, i.e., constant suction over the depth matric suction decrease linearly with depth and suction profile mixed (ie, the part is kept constant and decrease linearly with depth). After determination of the active and passive earth pressure was established equilibrium limit retaining wall and give the sheet length for safety factors of 1,0 and 1,5. It was noticed that there is reduction in the active earth pressure and increased passive earth pressure for all conditions in suction profile. Due to suction, there is an increased horizontal depth tension zone that contributes to the reduction in the horizontal efforts on the structures retaining wall , then a reduction in the sheet length. Otherwise the specific weight natural varies with the suction and that is a factor that can increase efforts, particularly for rainfall with relative intensity close to 1 (q/ksat) and saturated soils with high permeability, where suction is small and has constant distribuiton in the soil profile.
A necessidade do uso das estruturas de contenção tem sido cada vez mais frequente em obras de engenharia. A valorização do uso do solo tem levado a exploração ampla do subsolo, implicando em grandes escavações que alteram o estado de equilíbrio do solo. O desempenho e dimensionamento da contenção exigem um bom entendimento do estado de tensões do solo, da interação solo-estrutura e da variação da saturação do solo durante a construção e vida útil da contenção. A vida útil de uma obra deve garantir estabilidade, funcionalidade e durabilidade. A análise da interação solo-estrutura torna-se importante pelo fato de que a mesma estrutura, submetida à mesma carga externa, apresenta reações de apoio que variam com as condições particulares do maciço de solo em que ela se encontra. Portanto o estudo da interação solo-atmosfera é um dos fatores essenciais para os solos não saturados. Com intuito de avaliar a influência da sucção no dimensionamente de uma estrutura de contenção em balanço, foram simulados condições reais de precipitações em três solos distintos para três profundidades de escavações (3, 6 e 9 m) e para várias condições inciciais de N.A. E observou-se que o comportamento do perfil de sucção está intimamente relacionado com os parâmetros saturados bem como os não saturados de cada solo, com a intensidade e duração da precipitação. Através da teoria do empuxo de terra de Rankine, para os solos saturados foram desenvolvidas as formulação para cálculo dos empuxos ativos e passivo levando em consideração a não saturação do solo, para três comportamentos diferentes da sucção, isto é; sucção constante ao longo da profundidade, sucção variando linearmente com a profundidade e perfil de sucção misto (i.e., parte é mantido constante e parte varia linearmente com a profundidade). Após a determinação dos empuxos ativo e passivo foi estabelecido o equilíbrio limite da contenção e determinado o comprimento da ficha para dos fatores de segurança de 1,0 e 1,5. Percebeu-se que há redução do empuxo ativo e um acréscimo do empuxo passivo para todas as condições de perfil de sucção. Devido a sucção, há um aumento da profundidade da tensão horizontal nula que foi um dos parâmetros que contribui para a redução dos esforços horizontais na contenção, logo uma redução no comprimento da ficha. Por outro lado o peso específico natural varia com a sucção e esse é um fator que pode aumentar os esforços, principalmente para chuvas com intensidade relativa próxima de 1 (q/ksat) e solos com permeabilidade saturada alta, onde a sucção é pequena e tem-se distribuição constante no perfil do solo.
Sivasubramanian, Sriramkumar. "Optimization and simulation of formed suction cup to position aerospace CFRP parts during milling." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Konstruktion och produktutveckling, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-44566.
Full textPortelinha, Fernando Henrique Martins. "Avaliação experimental da influência do avanço do umedecimento no comportamento de muros de solos finos reforçados com geotêxteis não tecidos." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-18062013-110750/.
Full textThe effect of the wetting front advancement on the performance of nonwoven geotextile reinforced soil walls constructed with poorly draining soils was evaluated by laboratory full scale models. The tested models performances were monitored under rainfall conditions with different intensities and duration, as well as under intermittent precipitation with reduced intensity of precipitation (lower than the soil permeability). For comparison purposes, an evaluation of a full scale model was conducted with constant soil water content (compaction water content). As regards infiltration, capillary barrier formation have been observed on the interface soil-geotextile during infiltration process; besides, the drainage function of reinforcements after the breakthrough of water, in which water pressures development have not been allowed to occur even after rapid loading. After breakthrough of water, the degree of saturation was maintained around 90% and water pressures were negatives and close to zero. Besides, there are evidences that capillary barriers did not affect the model performance. As a result of wetting advancement, reinforcement strains and internal displacements have increased exponentially with the average of degree saturation of soil. Additionally, these parameters have shown to be correlated to the matric suction of soil with the same trend of the water retention curve. These relationships are essentially resulted from the soil stiffness alterations due to the wetting advancement and suction reduction. Under water content of compaction, reinforcement tensile forces were approximately zero, as a result of the relatively high stiffness of the unsaturated soil caused by the matric suction. Generally, displacements and reinforcement strains were small under wetting conditions and increased when stress increments were applied. However, these strains levels obtained cannot be considered excessive. A validation of laboratory results was observed in an instrumented geotextile reinforced soil wall, in addition to the comparison between woven and nonwoven geotextile sections, in which similar performances were found. Strains levels registered in field were consistent to the laboratory and the nonwoven geotextile wall was not affected by the wetting occurrence. Therefore, the efficiency of nonwoven geotextiles reinforced walls under wetting conditions is assured with no positive water pressures and relatively low levels of degree of saturation, being able to constitute permanent reinforced walls.
Avsarkisov, Victor. "Turbulent Poiseuille Flow with Uniform Wall Blowing and Suction." Phd thesis, 2013. https://tuprints.ulb.tu-darmstadt.de/3931/1/Diss.pdf.
Full textChiang, 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.
Full textLin, Mu-Chen, and 林沐謙. "A Low Reynolds Number .kappa.-.epsilon. Turbulence Model with Wall Blowing or suction and Heat Transfer." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/30229577722896249454.
Full text國立臺灣大學
機械工程研究所
81
This study proposes a low Reynolds number k-epsilon turbulent model which can be applied to flows with a wide range of blowing or suction.It is improved from the Lam-Bremhorst low Reynolds number turbulent model without blowing and suction.The model is tested in the flat-plate flow. The results show that not only the predicted velocity profile, shear stress distribution and drag coefficient(Cf),but also the turbulent viscosity are all in good agreement with available expermental data.An quantitative analysis of k and epsilon is also included in the present work. For thermal turbulent-boundary-layer with wall blowing in addition to the turbulent model proposed , this study also proposes a turbulent Prandtl number expression. It is a function of y+ and blowing parameter. Tested in the thermal turbulent-boundary-layer over a proposed turbulent model and turbulent Prandtl number expression can yield temperature distributions and St which are in good with experimental data.