Relevant bibliographies by topics / Wall suction

Academic literature on the topic 'Wall suction'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Wall suction"

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Zhao, Jianghong, Xin Li, and Jin Bai. "Experimental study of vortex suction unit-based wall-climbing robot on walls with various surface conditions." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 21 (August 17, 2018): 3977–91. http://dx.doi.org/10.1177/0954406218791203.

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This study presents a wall-climbing robot called Vortexbot. Vortexbot has a suction unit that uses vortex flow to generate a suction force. Unlike the traditional unit based on contact-type suction, the suction unit can maintain a suction force without any contact with the wall surface. Therefore, the suction unit can provide a climbing robot with sufficient stable suction force even on walls with very rough surfaces and raised obstacles/grooves, and there is no wear and tear. Furthermore, the compressed air vents from the gap between the suction unit and the wall surface after rotating in the vortex chamber. Hence, such kind of flow direction can avoid the effect of the dust and dropped items on the wall surface. In this paper, we first introduced the vortex suction unit principle and discuss the feasibility of its application to a wall-climbing robot. Subsequently, the mechanical structure of Vortexbot was designed. After which, we surveyed the suction properties of the suction unit on a smooth wall surface. Then the functional relationship between the percentage change in the suction force and the supply flow rate was obtained. In addition, we studied the effect of the roughness and shape (a raised obstacle and groove) of the wall surface on the suction performance of the suction unit. Finally, we experimentally verified the climbing performance of Vortexbot on several kinds of walls with different surface conditions. It was confirmed that using the suction unit improves the robot’s climbing performance.
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Abu-Nada, E., A. Al-Sarkhi, B. Akash, and I. Al-Hinti. "Heat Transfer and Fluid Flow Characteristics of Separated Flows Encountered in a Backward-Facing Step Under the Effect of Suction and Blowing." Journal of Heat Transfer 129, no. 11 (February 1, 2007): 1517–28. http://dx.doi.org/10.1115/1.2759973.

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Abstract Numerical investigation of heat transfer and fluid flow over a backward-facing step (BFS), under the effect of suction and blowing, is presented. Here, suction/blowing is implemented on the bottom wall (adjacent to the step). The finite volume technique is used. The distribution of the modified coefficient of friction and Nusselt number at the top and bottom walls of the BFS are obtained. On the bottom wall, and inside the primary recirculation bubble, suction increases the modified coefficient of friction and blowing reduces it. However, after the point of reattachment, mass augmentation causes an increase in the modified coefficient of friction and mass reduction causes a decrease in modified coefficient of friction. On the top wall, suction decreases the modified coefficient of friction and blowing increases it. Local Nusselt number on the bottom wall is increased by suction and is decreased by blowing, and the contrary occurs on the top wall. The maximum local Nusselt number on the bottom wall coincides with the point of reattachment. High values of average Nusselt number on the bottom wall are identified at high Reynolds numbers and high suction bleed rates. However, the low values correspond to high blowing rates. The reattachment length and the length of the top secondary recirculation bubble are computed under the effect of suction and blowing. The reattachment length is increased by increasing blowing bleed rate and is decreased by increasing suction bleed rate. The spots of high Nusselt number, and low coefficient of friction, are identified by using contour maps.
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Michinaga, Yuki, Tamaki Takano, Takamitsu Terasaki, Souma Miyazaki, Noritoshi Kikuchi, and Kenji Okada. "Hemolytic characteristics of three suctioning systems for use with a newly developed cardiopulmonary bypass system." Perfusion 34, no. 2 (August 19, 2018): 136–42. http://dx.doi.org/10.1177/0267659118793559.

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Introduction: We have been developing a closed-circuit cardiopulmonary bypass (CPB) system (“Dihead CPB”) for application during coronary artery bypass grafting (CABG) and valve surgery. To strive for minimal hemolysis during Dihead CPB, we compared the hemolysis caused by three different suction systems and performed a clinical study with the newly applied suction system. Materials & Methods: We evaluated the hemolysis caused by roller-pump suction, the SmartSuction® Harmony® and wall suction systems with respect to suction speed and compared the systems by means of in vitro studies. A clinical study was also performed on 15 volunteers to assess hemolysis and the adequacy of the newly applied suction system with Dihead CPB. Results: Pressure inside the suction cannula was −22.5 ± 0.1 mmHg at a maximum flow of 1.5 L/min for roller-pump suction and −43.4 ± 0.1 mmHg at −150 mmHg of the set vacuum pressure of wall suction. With the SmartSuction, the pressure inside the cannula varied from −76.3 ± 1.0 to −130.3 ± 1.5 mmHg, depending on suctioning conditions. Suction speed (to suction 50 ml of blood) was fastest with the SmartSuction (69.7 ± 3.58 s) whereas, with roller suction, it was 117.3 ± 8.47 s and with wall suction 96.9 ± 7.10 s. The SmartSuction had the highest hemolysis rate (2.00 ± 0.33%) vs. 0.61 ± 0.10% for roller suction and 0.41 ± 0.11% for wall suction (p<0.001). The clinical study with wall suction showed no significant increase in plasma free hemoglobin during or after CPB compared with before surgery. Conclusions: Wall suction had less hemolysis than roller suction or the SmartSuction in the in vitro study and the clinical study with wall suction showed efficient suction speed and acceptable hemolysis, suggesting that Dihead CPB with wall suction is feasible for CABG.
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Gofar, Nurly, and Hanafiah. "Contribution of suction on the stability of reinforced-soil retaining wall." MATEC Web of Conferences 195 (2018): 03004. http://dx.doi.org/10.1051/matecconf/201819503004.

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Existing design methods of a reinforced-soil retaining wall were established for walls with cohesionless soil backfill. However, local soil has been used widely in the construction of such a wall for economic reasons. Laboratory and numerical studies have pointed out the merit of using cohesive backfill in association with geosynthetic reinforcement. Since the compacted soil was in an unsaturated condition during the construction of the reinforced wall, the apparent cohesion derived from both soil mineralogy and suction could contribute to the stability of the wall. This paper considers methods to include the suction contribution to the existing design guidelines based on slope stability analysis, i.e. simplified method and simplified stiffness method. The analyses were carried out on a case study of geosynthetics reinforced soil retaining wall. Results show that the contribution of suction as part of cohesion existing in the cohesive backfill could be considered for the stability analysis of reinforced soil retaining walls using the available design guidelines.
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Muthuraj, R., and S. Srinivas. "Influence of magnetic field and wall slip conditions on steady flow between parallel flat wall and a long wavy wall with Soret effect." Journal of Naval Architecture and Marine Engineering 6, no. 2 (June 23, 2010): 62–71. http://dx.doi.org/10.3329/jname.v6i2.3061.

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The steady MHD flow in the presence of temperature dependent heat source in a viscous incompressible fluid bounded by a parallel flat wall and a long wavy wall is studied with heat and mass transfer, taking into account the thermal-diffusion (Soret) effects, when the no-slip condition at the channel wall in no longer valid. An external uniform magnetic field and a uniform suction are applied perpendicular to the flat wall. The walls are kept at different but constant temperatures. The velocity, temperature and concentration field have been evaluated numerically for various values of the parameters entering the problem. The skin friction, rate of heat and mass transfer at the walls are obtained and discussed graphically. Keywords: Wavy wall; slip parameter; Sherwood number; suction parameter; Soret number DOI: 10.3329/jname.v6i2.3061
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Tokuomi, Saeko, and Kazuya Mori. "Suction Cup for Concrete Wall Testing Robot." Journal of Robotics and Mechatronics 28, no. 2 (April 19, 2016): 194–97. http://dx.doi.org/10.20965/jrm.2016.p0194.

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[abstFig src='/00280002/10.jpg' width=""300"" text='Claws attached to suction cups' ]Efficient economical test methods are widely needed worldwide. One target of this is to develop climbing robots that check for defects in concrete. These concrete-wall-climbing robots generally use suction cups to support themselves and test apparatus, but the danger exists of this expensive equipment falling. This may occur due to one of two reasons. The first is inadequate ring-seal decompression in suction cups and the second is suction cup slippage. We have added claws to suction cups to help prevent slippage. The claws we developed are attached to the suction cups to help grip the wall. In the sections below, we discuss the scratch tests we performed to test claw effectiveness in improving suction cup grip. We then prove through tests under actual conditions that the estimated grip force matched that of an actual suction cup's grip force with the claw.
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DEY, SUBHASISH, TUSHAR K. NATH, and SUJIT K. BOSE. "Submerged wall jets subjected to injection and suction from the wall." Journal of Fluid Mechanics 653 (April 27, 2010): 57–97. http://dx.doi.org/10.1017/s0022112010000182.

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This paper presents an experimental study on turbulent flow characteristics in submerged plane wall jets subjected to injection (upward seepage) and suction (downward seepage) from the wall. The vertical distributions of time-averaged velocity components, turbulence intensity components and Reynolds shear stress at different horizontal distances are presented. The horizontal distributions of wall shear stress determined from the Reynolds shear stress profiles are also furnished. The flow field exhibits a decay of the jet velocity over a horizontal distance. The wall shear stress and the rate of decay of the jet velocity increase in the presence of injection and decrease with suction. Based on the two-dimensional Reynolds-averaged Navier–Stokes equations of a steady turbulent flow, the velocity and Reynolds shear stress distributions in the fully developed zone subjected to no seepage, injection and suction are theoretically computed. The response of the turbulent flow characteristics to injection and suction is analysed from the point of view of similarity characteristics, growth of the length scale and decay of the velocity and turbulence characteristics scales. The significant observation is that the velocity, Reynolds shear stress and turbulence intensities in the fully developed zone are reasonably similar under both injection and suction on applying the appropriate scaling laws. An analysis of the third-order moments of velocity fluctuations reveals that the inner layer of the jet is associated with the arrival of low-speed fluid streaks causing an effect of retardation. On the other hand, the upper layer of the jet is associated with the arrival of high-speed fluid streaks causing an effect of acceleration. Injection influences the near-wall distributions of the third-order moments by increasing the upward turbulent advection of the streamwise Reynolds normal stress. In contrast, suction influences the near-wall distributions of the third-order moments by increasing the downward turbulent advection of the streamwise Reynolds normal stress. Also, injection and suction change the vertical turbulent flux of the vertical Reynolds normal stress in a similar way. The streamwise turbulent energy flux travels towards the jet origin within the jet layer, while it travels away from the origin within the inner layer of the circulatory flow. The turbulent energy budget suggests that the turbulent and pressure energy diffusions oppose each other, and the turbulent dissipation lags the turbulent production. The quadrant analysis of velocity fluctuations reveals that the inward and outward interactions are the primary contributions to the Reynolds shear stress production in the inner and outer layers of the jet, respectively. However, injection induces feeble ejections in the vicinity of the wall.
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Portelinha, Fernando H. M., Jorge G. Zornberg, and Orencio M. Vilar. "Deformation analysis of an unsaturated geosynthetic reinforced soil wall subjected to infiltration." MATEC Web of Conferences 337 (2021): 03018. http://dx.doi.org/10.1051/matecconf/202133703018.

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Geosynthetic-reinforced soil walls are structures typically constructed with compacted and thus unsaturated soils. The use of local fine-grained soils as backfill material has been a common practice in view of the significant cost reduction in comparison to granular backfills. This is especially applicable in tropical areas where lateritic soils are found as these material scan exhibit outstanding geotechnical properties mainly under unsaturated conditions. Thus, it is possible to optimize the design and construction of geosynthetic-reinforced soil walls considering soil unsaturation, however it is not known to what extent infiltration can reduce soil suction impairing the safety of the structure. To address the influence of suction on the behavior of geosynthetic structures, a full-scale geotextile-reinforced wall was subjected to infiltration and instrumented to capture the distribution of moisture and soil suction along the reinforced zone, as well as reinforcements strains. This paper presents and discuss the influence of geotextile reinforcement acting as capillary barrier coupled with the wall performance. Results demonstrate that the advancement of infiltration front has a more pronounced effect on deformation as the changes on water contents. Capillary barriers were found to occur retarding infiltration, but not affecting the overall performance of the structure. The average of monitored suction values along the wall height, herein called as “global suction”, was found to be strictly related to maximum reinforcement strains behavior.
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Ricco, Pierre, Daniel Shah, and Peter D. Hicks. "Compressible laminar streaks with wall suction." Physics of Fluids 25, no. 5 (May 2013): 054110. http://dx.doi.org/10.1063/1.4807066.

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Chen, Rui, Leilei Fu, Yilin Qiu, Ruizhou Song, and Yan Jin. "A gecko-inspired wall-climbing robot based on vibration suction mechanism." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 19-20 (August 18, 2019): 7132–43. http://dx.doi.org/10.1177/0954406219869041.

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A prototype of gecko-inspired wall-climbing robot based on vibration suction mechanism is proposed. The robot adheres to the wall surface based on a novel negative pressure technology named as vibration suction. According to the theory of vibration suction, the vibration suction module is designed as the foot of the wall-climbing robot. In addition, the tripod gait of geckos is taken into account in the motion planning of the robot. By combining the unique properties of vibration suction mechanism and the tripod gait of the geckos, several advantages including stable motion, certain load capacity, anti-overturning ability, and good suction force to the wall surfaces are obtained. The climbing ability is verified by the experiment on the surface of the glass, which manifests that the robot can climb vertically at the highest speed of 13.75 mm/s with a spot turning at the single maximum turning angle of 20°. Potential applications of this proposed climbing robot in some fields include repair, construction, cleaning, and exploration.
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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.

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Choudhari, Meelan 1963. "Boundary layer receptivity at a suction surface-hard wall junction." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277030.

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Receptivity refers to the generation of boundary layer instability waves by external disturbances. Recent work by M. E. Goldstein has set the general framework for the different types of boundary layer receptivity mechanisms. Therefore, it is now understood that receptivity occurs near the leading edge or at locations downstream where the boundary layer undergoes a rapid streamwise adjustment. The present work analyzes the receptivity due to a free-stream acoustic wave interacting with a suction surface--hard wall junction. In this case, receptivity occurs because of the rapid changes in wall suction distribution. Analytical expressions for the amplitude of the generated instability wave have been derived and numerical estimates provided for parameter values typical of hybrid laminar flow control applications. The importance of the junction receptivity as compared to other receptivity mechanisms has been assessed.
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Bobke, 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.

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The focus of the present licentiate thesis is on the effect of suction and pressure gradients on turbulent boundary-layer flows, which are investigated separately through performing numerical simulations.The first part aims at assessing history and development effects on adverse pressure-gradient (APG) turbulent boundary layers (TBL). A suitable set-up was developed to study near-equilibrium conditions for a boundary layer developingon a flat plate by setting the free-stream velocity at the top of the domain following a power law. The computational box size and the correct definition of the top-boundary condition were systematically tested. Well-resolved large-eddy simulations were performed to keep computational costs low. By varying the free-stream velocity distribution parameters, e.g. power-law exponent and virtual origin, pressure gradients of different strength and development were obtained. The magnitude of the pressure gradient is quantified in terms of the Clauser pressure-gradient parameter β. The effect of the APG is closely related to its streamwise development, hence, TBLs with non-constant and constant β were investigated. The effect was manifested in the mean flow through a much more pronounced wake region and in the Reynolds stresses through the existence of an outer peak. The terms of the turbulent kinetic energy budgets indicate the influence of the APG on the distribution of the transfer mechanism across the boundary layer. Stronger and more energetic structures were identified in boundary layers with relatively stronger pressure gradients in their development history. Due to the difficulty of determining the boundary-layer thickness in flows with strong pressure gradients or over a curvedsurface, a new method based on the diagnostic-plot concept was introduced to obtain a robust estimation of the edge of a turbulent boundary layer. In the second part, large-eddy simulations were performed on temporally developing turbulent asymptotic suction boundary layers (TASBLs). Findings from previous studies about the effect of suction could be confirmed, e.g. the reduction of the fluctuation levels and Reynolds shear stresses. Furthermore, the importance of the size of the computational domain and the time development were investigated. Both parameters were found to have a large impact on the results even on low-order statistics. While the mean velocity profile collapses in the inner layer irrespective of box size and development time, a wake region occurs for too small box sizes or early development time and vanishes once sufficiently large domains and/or integration times are chosen. The asymptotic state is charactersized by surprisingly thick boundary layers even for moderateReynolds numbers Re (based on free-stream velocity and laminar displacement thickness); for instance, Re = 333 gives rise to a friction Reynolds number Reτ = 2000. Similarly, the flow gives rise to very large structures in the outer region. These findings have important ramifications for experiments, since very large facilities are required to reach the asymptotic state even for low Reynolds numbers.

QC 20160418

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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.

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The focus of this thesis is on the numerical study of subcritical transition to turbulence in the asymptotic suction boundary layer (ASBL). Applying constant homogeneous suction prevents the spatial growth of the boundary layer, granting access to the asymptotic dynamics. This enables research approaches which are not feasible in the spatially growing case. In a first part, the laminar–turbulent separatrix of the ASBL is investigated numerically by means of an edge-tracking algorithm. The consideration of spanwise-extended domains allows for the robust localisation of the attracting flow structures on this separatrix. The active part of the identified edge states consists of a pair of low- and high-speed streaks, which experience calm phases followed by high energy bursts. During these bursts the structure is destroyed and re-created with a shift in the spanwise direction. Depending on the streamwise extent of the domain, these shifts are either regular in direction and distance, and periodic in time, or irregular in space and erratic in time. In all cases, the same clear regeneration mechanism of streaks and vor- tices is identified, bearing strong similarities with the classical self-sustaining cycle in near-wall turbulence. Bifurcations from periodic to chaotic regimes are studied by varying the streamwise length of the (periodic) domain. The resulting bifurcation diagram contains a number of phenomena, e.g. multistability, intermittency and period doubling, usually investigated in the context of low-dimensional systems. The second part is concerned with spatio–temporal aspects of turbulent ASBL in large domains near the onset of sustained turbulence. Adiabatically decreasing the Reynolds number, starting from a fully turbulent state, we study low-Re turbulence and events leading to laminarisation. Furthermore, a robust quantitative estimate for the lowest Reynolds number at which turbulence is sustained is obtained at Re  270.

QC 20140213

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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.

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Tilton, 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.

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We investigate the effects of wall permeability on the linear stability of two classical wall-bounded shear flows. In the first part of this thesis, we consider pressure driven, incompressible, fully developed, laminar flow in a channel delimited by rigid, homogeneous, isotropic, porous layers. We consider porous materials of small permeability in which the flow velocity is small and for which the inertial effects can be neglected. We solve the fully coupled, temporal, linear stability problem arising from the adjacent flows in the channel and porous regions. We perform a parametric study in which we vary the permeability, porosity, and height of the porous layers as well as a coefficient associated with the momentum transfer process at the interfaces between the channel and porous layers. We find that the overall stability is dictated by several competing mechanisms. For the majority of the parameter space studied, wall permeability has a significant destabilizing effect and the critical Reynolds number can decrease to values on the order of 10% that for plane Poiseuille flow. For particular configurations, however, we observe that permeability can have a stabilizing effect. We compare our results with previously published numerical and experimental studies.
In 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.
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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.

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Disturbances 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.

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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.

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The design of metal building roof and wall systems under uplift and suction wind loading is complicated because the laterally unbraced purlin and girtâ s free flange is compressed, and the cross-section rotates due to the shear flow. The objective of this thesis is to introduce a Direct Strength Method (DSM) prediction approach for simple span purlins and girts with one flange through-fastened under uplift or suction loading. This prediction method is also applicable for the case when rigid board insulation is placed between the metal panel and through-fastened flange. The prediction method is validated with a database of 62 simple span tests. To evaluate the prediction for the case when rigid board is used, 50 full-scale tests with rigid board insulation are conducted by the author of this thesis. In the experimental study panel failure, connection failure and member (purlin and girt) failure are observed, and they all limit the systemâ s capacity. Another important contribution of this thesis is that it builds the foundation for future study of a general, mechanics-based limit state design approach for metal building roof and wall systems that can accommodate uplift and gravity loads, simple and continuous spans, and through-fastened and standing seam roofs.
Ph. D.
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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.

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Wall transpiration, in the form of wall-normal suction or blowing through a permeable wall, is a relatively simple and effective technique to control the behaviour of a boundary layer. For its potential applications for laminar-turbulent transition and separation delay (suction) or for turbulent drag reduction and thermal protection (blowing), wall transpiration has over the past decades been the topic of a significant amount of studies. However, as far as the turbulent regime is concerned, fundamental understanding of the phenomena occurring in the boundary layer in presence of wall transpiration is limited and considerable disagreements persist even on the description of basic quantities, such as the mean streamwise velocity, for the rather simplified case of flat-plate boundary-layer flows without pressure gradients. In order to provide new experimental data on suction and blowing boundary layers, an experimental apparatus was designed and brought into operation. The perforated region spans the whole 1.2 m of the test-section width and with its streamwise extent of 6.5 m is significantly longer than previous studies, allowing for a better investigation of the spatial development of the boundary layer. The quality of the experimental setup and measurement procedures was verified with extensive testing, including benchmarking against previous results on a canonical zero-pressure-gradient turbulent boundary layer (ZPG TBL) and on a laminar asymptotic suction boundary layer. The present experimental results on ZPG turbulent suction boundary layers show that it is possible to experimentally realize a turbulent asymptotic suction boundary layer (TASBL) where the boundary layer mean-velocity profile becomes independent of the streamwise location, so that the suction rate constitutes the only control parameter. TASBLs show a mean-velocity profile with a large logarithmic region and without the existence of a clear wake region. If outer scaling is adopted, using the free-stream velocity and the boundary layer thickness (δ99) as characteristic velocity and length scale respectively, the logarithmic region is described by a slope Ao=0.064 and an intercept Bo=0.994, independently from the suction rate (Γ). Relaminarization of an initially turbulent boundary layer is observed for Γ>3.70×10−3. Wall suction is responsible for a strong damping of the velocity fluctuations, with a decrease of the near-wall peak of the velocity-variance profile ranging from 50% to 65% when compared to a canonical ZPG TBL at comparable Reτ. This decrease in the turbulent activity appears to be explained by an increased stability of the near-wall streaks. Measurements on ZPG blowing boundary layers were conducted for blowing rates ranging between 0.1% and 0.37% of the free-stream velocity and cover the range of momentum thickness Reynolds number 10000<Reθ<36000. Wall-normal blowing strongly modifies the shape of the boundary-layer mean-velocity profile. As the blowing rate is increased, the clear logarithmic region characterizing the canonical ZPG TBLs gradually disappears. A good overlap among the mean velocity-defect profiles of the canonical ZPG TBLs and of the blowing boundary layers for all the Re number and blowing rates considered is obtained when normalization with the Zagarola-Smits velocity scale is adopted. Wall blowing enhances the intensity of the velocity fluctuations, especially in the outer region. At sufficiently high blowing rates and Reynolds number, the outer peak in the streamwise-velocity fluctuations surpasses in magnitude the near-wall peak, which eventually disappears.
Genom 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

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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.

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Books on the topic "Wall suction"

1

Bodonyi, R. J. Boundary-layer receptivity due to a wall suction and control of Tollmien-Schlichting waves. Hampton, Va: Institute for Computer Applications in Science and Engineering, 1990.

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Murthy, A. V. Sidewall boundary-layer measurements with upstream suction in the Langley 0.3-meter Transonic Cryogenic Tunnel. Hampton, Va: Langley Research Center, 1988.

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W, Duck Peter, and Langley Research Center, eds. Boundary-layer receptivity due to a wall suction and control of Tollmein-Schlichting waves. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1990.

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Analytical Services & Materials, Inc. and United States. National Aeronautics and Space Administration. Scientific and Technical Information Program., eds. Secondary instability of high-speed flows and the influence of wall cooling and suction. Washington, D.C: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Program, 1992.

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W, Duck Peter, and Langley Research Center, eds. Boundary-layer receptivity due to a wall suction and control of Tollmein-Schlichting waves. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1990.

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Abouzgheib, Wissam, and Raquel Nahra. Management of pneumothorax and bronchial fistulae. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0124.

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The management of pneumothorax is dependent on size and associated symptoms. A conservative approach is preferred in small and asymptomatic ones. While a large pneumothorax warrants chest tube drainage, small bore could be as effective as large chest tubes and should be used first. The use of bedside ultrasound plays a major role in the acute management of pneumothorax and has an excellent negative predictive value. In some instances, there may be an associated air leak, caused by a broncho- or alveolopleural fistula, which can be managed by chest tube drainage, with or without suction, depending on the severity and extent of lung collapse. With a large air leak, wall suction is needed to keep the lung inflated. In small, intermittent air leaks, suction should be avoided to promote healing of the fistula. With the availability of one-way valves, management of these fistulae became easier, allowing blockage of the airway causing the air leak, and promoting healing and early chest tube removal.
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D, Vakili A., Wu Zhengming 1945-, University of Tennessee (System). Space Institute., and Ames Research Center, eds. Final report on investigation of transonic flow over segmented slotted wind tunnel wall with mass transfer. Tullahoma, TN: The University of Tennessee Space Institute, 1990.

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United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., ed. Sidewall boundary-layer measurements with upstream suction in the Langley 0.3-meter transonic cryogenic tunnel. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Division, 1988.

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Sidewall boundary-layer measurements with upstream suction in the Langley 0.3-meter transonic cryogenic tunnel. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Division, 1988.

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Book chapters on the topic "Wall suction"

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Ferro, Marco, Bengt E. G. Fallenius, and Jens H. M. Fransson. "On the Turbulent Boundary Layer with Wall Suction." In Springer Proceedings in Physics, 39–44. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-57934-4_6.

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Lee, Jeesoo, and Sanghoon Kim. "Suction Based Wall Climbing Robot for Edge Movement." In Lecture Notes in Electrical Engineering, 687–96. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-017-8798-7_79.

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Gorban, I. M., and O. V. Khomenko. "Active Near-Wall Flow Control via a Cross Groove with Suction." In Studies in Systems, Decision and Control, 353–67. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-19075-4_21.

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Sun, M. "Suction Force Induced by the Collapse of a Near-Wall Bubble." In 30th International Symposium on Shock Waves 2, 1281–86. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-44866-4_85.

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Chen, Rui, Yilin Qiu, Li Wu, Jinquan Chen, Long Bai, and Qian Tang. "A Gecko Inspired Wall-Climbing Robot Based on Vibration Suction Mechanism." In Communications in Computer and Information Science, 571–80. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-2396-6_53.

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Malik, M. R., and A. A. Godil. "Effect of Wall Suction and Cooling on the Second Mode Instability." In Advances in Soil Science, 235–45. New York, NY: Springer New York, 1990. http://dx.doi.org/10.1007/978-1-4612-3432-6_18.

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Fulachier, L., T. Benabid, F. Anselmet, R. A. Antonia, and L. V. Krishnamoorthy. "Behaviour of Coherent Structures in a Turbulent Boundary Layer with Wall Suction." In Advances in Turbulence, 399–407. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-83045-7_45.

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Antonia, R. A., Y. Zhu, and M. Sokolov. "Relaminarization of a Turbulent Boundary Layer by Suction Through a Short Porous Wall Strip." In Fluid Mechanics and Its Applications, 1–5. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0457-9_1.

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Zhao, Jianghong, and Xin Li. "Development of Wall-Climbing Robot Using Vortex Suction Unit and Its Evaluation on Walls with Various Surface Conditions." In Intelligent Robotics and Applications, 179–92. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-65298-6_17.

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Cathalifaud, Patricia, and Paolo Luchini. "Optimal Control by Blowing and Suction at the Wall of Algebraically Growing Boundary Layer Disturbances." In Laminar-Turbulent Transition, 307–12. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-662-03997-7_45.

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Conference papers on the topic "Wall suction"

1

Chung, Yongmann M., and Hyung Jin Sung. "MODULATION OF NEAR-WALL ANISOTROPY WITH UNIFORM WALL BLOWING AND SUCTION." In Second Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2001. http://dx.doi.org/10.1615/tsfp2.1270.

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Xu, Daijun, Xueshan Gao, Xiaobing Wu, Ningjun Fan, Kejie Li, and Koki Kikuchi. "Suction Ability Analyses of a Novel Wall Climbing Robot." In 2006 IEEE International Conference on Robotics and Biomimetics. IEEE, 2006. http://dx.doi.org/10.1109/robio.2006.340152.

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Qian, Zhi-yuan, Yan-zheng Zhao, and Zhuang Fu. "Development of Wall-climbing Robots with Sliding Suction Cups." In 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems. IEEE, 2006. http://dx.doi.org/10.1109/iros.2006.282579.

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Yoshioka, Shuya, Jens H. M. Fransson, and P. Henrik Alfredsson. "EVOLUTION OF DISTURBANCES IN BOUNDARY LAYERS WITH WALL SUCTION." In Third Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2003. http://dx.doi.org/10.1615/tsfp3.830.

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Yoshida, Yu, and Shugen Ma. "A wall-climbing robot without any active suction mechanisms." In 2011 IEEE International Conference on Robotics and Biomimetics (ROBIO). IEEE, 2011. http://dx.doi.org/10.1109/robio.2011.6181587.

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Yoshida, Yu, and Shugen Ma. "Design of a wall-climbing robot with passive suction cups." In 2010 IEEE International Conference on Robotics and Biomimetics (ROBIO). IEEE, 2010. http://dx.doi.org/10.1109/robio.2010.5723554.

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Malik, Abdullah, and Peter Render. "Use of Wall Suction In Half Model Wind Tunnel Testing." In 28th AIAA Applied Aerodynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-4828.

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Jankowski, T., and J. Majdalani. "Acoustical and vortical interactions inside a channel with wall suction." In 6th Aeroacoustics Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2000. http://dx.doi.org/10.2514/6.2000-1988.

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Chung, Yongmann M., and Hyung Jin Sung. "SENSITIVITY STUDY OF TURBULENCE CONTROL WITH WALL BLOWING AND SUCTION." In Third Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2003. http://dx.doi.org/10.1615/tsfp3.290.

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Li, Jun, Xueshan Gao, Ningjun Fan, Wei Zhu, Jin Yin, and Yujiao Jia. "Wall climbing robot based on negative pressure-thrust suction method." In 2008 IEEE International Conference on Mechatronics and Automation (ICMA) (Formerly ICIMA). IEEE, 2008. http://dx.doi.org/10.1109/icma.2008.4798825.

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