Journal articles: 'Leading-edge suction'

1

Badran, B., S. McCormick, and I. Gursul. "Control of Leading-Edge Vortices with Suction." Journal of Aircraft 35, no. 1 (January 1998): 163–65. http://dx.doi.org/10.2514/2.2279.

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2

Wong, P. W. C., M. Maina, and A. M. Cobbin. "Transition and separation control in the leading edge region." Aeronautical Journal 105, no. 1049 (July 2001): 371–78. http://dx.doi.org/10.1017/s0001924000012288.

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Abstract This paper describes an investigation of methods of controlling transition and separation in the leading edge region of military aircraft wings. For wings with the high leading edge sweep relevant to some military aircraft, if attachment line contamination can be prevented then transition is predominantly caused by crossflow instability close to the leading edge. The use of surface suction or cooling for suppressing these instabilities in order to delay transition, has been investigated in a parametric study. The placing of a short suction panel close to the leading edge has been found to be an effective means of controlling instability. Conversely, the level of cooling required to suppress crossflow instability may be too high for practical aircraft applications. The use of suction for preventing laminar separation for pressure distributions with a leading edge suction peak has also been included in the parametric study. The suction quantity required is strongly dependent on the peak height. The suction quantity that can be achieved in practice will limit the maximum peak height that can be attained without laminar separation. An investigation of leading edge stall and control has also been carried out. The analysis suggests that it is important to be able to identify whether the stall is due to laminar bubble bursting or turbulent re-separation, since different methods of controlling the stall may be required.

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3

Er-El, Joseph, and Zohar Yitzhak. "Experimental examination of the leading-edge suction analogy." Journal of Aircraft 25, no. 3 (March 1988): 195–99. http://dx.doi.org/10.2514/3.45577.

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Arnal, D., J. C. Juillen, J. Reneaux, and G. Gasparian. "Effect of wall suction on leading edge contamination." Aerospace Science and Technology 1, no. 8 (December 1997): 505–17. http://dx.doi.org/10.1016/s1270-9638(97)90000-6.

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5

Parmenter, K., and D. Rockwell. "Transient response of leading-edge vortices to localized suction." AIAA Journal 28, no. 6 (June 1990): 1131–33. http://dx.doi.org/10.2514/3.25177.

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6

Deparday, J., and K. Mulleners. "Critical evolution of leading edge suction during dynamic stall." Journal of Physics: Conference Series 1037 (June 2018): 022017. http://dx.doi.org/10.1088/1742-6596/1037/2/022017.

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7

Hardy, B. C., and S. P. Fiddes. "Prediction of vortex lift of non-planar wings by the leading-edge suction analogy." Aeronautical Journal 92, no. 914 (April 1988): 154–64. http://dx.doi.org/10.1017/s0001924000025562.

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SummaryA three-dimensional panel method has been used to calculate edge-suction forces for thin sharp-edged wings in incompressible flow. The suction forces have been used to estimate the vortex lift on the wings by means of the leading-edge suction analogy due to Polhamus.The results for planar wings are in acceptable agreement with other methods based on the suction analogy. A limited comparison with results from experiments for non-planar wings revealed good prediction of lift and drag increments associated with the deflection of leading and trailing edge flaps for ‘conventional’ wings of high sweep, but only moderate agreement for a grossly non-planar configuration.

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8

Wang, Chao, Ying Xiong, Guo Liang Wang, and Hai Peng Guo. "Prediction of Hydrodynamic Performance of Hydrofoil with Suction and Jet Equipment." Applied Mechanics and Materials 444-445 (October 2013): 432–36. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.432.

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In order to improve the hydrodynamic performance of the hydrofoil, one new foil is brought forward which has slits near the leading edge and the trailing edge. In this article, the NACA0012 foil whose performance was calculated by CFD method was chose as a study object. And the validity of the CFD method was proved by contrasting the calculation results with the experiments. Through calculating and analyzing the hydrodynamic performance of the new hydrofoil that has suction inlet and jet outlet in the leading edge and the trailing edge respectively, the result shows that such performance of suction-jet hydrofoil has advantages of both suction hydrofoil and water-jet hydrofoil.

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9

Li, Shao Hua, Li Mei Du, Wen Hua Dong, and Ling Zhang. "A Numerical Study on the Characteristics of How Heat and Cooling Transfer on the Leading Edge of a Film-Cooling Blade." Advanced Materials Research 383-390 (November 2011): 3963–68. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.3963.

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In this paper, a numerical simulation was performed to investigate heat transferring characteristics on the leading edge of a blade with three rows of holes of film-cooling using Realizable k- model. Three rows of holes were located on the suction side leading edge stagnation line and the pressure surface. The difference of the cooling efficiency and the heat transfer of the three rows of holes on the suction side and pressure side were analyzed; the heat transfer and film cooling effectiveness distribution in the region of leading edge are expounded under different momentum rations.The results show that under the same condition, the cooling effectiveness on the pressure side is more obvious than the suction side, but the heat transfer is better on the suction side than the pressure side. The stronger momentum rations are more effective cooling than the heat transfer system.

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10

Hobson, Garth V., Bryce E. Wakefield, and William B. Roberts. "Turbulence Amplification with Incidence at the Leading Edge of a Compressor Cascade." International Journal of Rotating Machinery 5, no. 2 (1999): 89–98. http://dx.doi.org/10.1155/s1023621x99000081.

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Detailed measurements, with a two-component laser-Doppler velocimeter and a thermal anemometer were made near the suction surface leading edge of controlled-diffusion airfoils in cascade. The Reynolds number was near 700,000, Mach number equal to 0.25, and freestream turbulence was at 1.5% ahead of the cascade.It was found that there was a localized region of high turbulence near the suction surface leading edge at high incidence. This turbulence amplification is thought to be due to the interaction of the free-shear layer with the freestream inlet turbulence. The presence of the local high turbulence affects the development of the short laminar separation bubble that forms very near the suction side leading edge of these blades. Calculations indicate that the local high levels of turbulence can cause rapid transition in the laminar bubble allowing it to reattach as a short “non-burst” type.The high turbulence, which can reach point values greater than 25% at high incidence, is the reason that leading edge laminar separation bubbles can reattach in the high pressure gradient regions near the leading edge. Two variations for inlet turbulence intensity were measured for this cascade. The first is the variation ofmaximum inlet turbulence with respect to inlet-flow angle; and the second is the variation of leading edge turbulence with respect to upstream distance from the leading edge of the blades.

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11

Traub, Lance W. "Extending the Leading-Edge Suction Analogy to Nonslender Delta Wings." Journal of Aircraft 55, no. 5 (September 2018): 2176–78. http://dx.doi.org/10.2514/1.c034939.

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12

Schulten, Johan B. H. M. "Unsteady Leading-Edge Suction Effects on Rotor-Stator Interaction Noise." AIAA Journal 38, no. 9 (September 2000): 1579–85. http://dx.doi.org/10.2514/2.1140.

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13

Lan, C. Edward, and Ingchung Su. "Effect of a round airfoil nose on leading-edge suction." Journal of Aircraft 24, no. 7 (July 1987): 472–74. http://dx.doi.org/10.2514/3.45504.

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14

Amiet, R. K. "Airfoil leading-edge suction and energy conservation for compressible flow." Journal of Fluid Mechanics 289 (April 25, 1995): 227–42. http://dx.doi.org/10.1017/s0022112095001315.

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When a flat-plate airfoil at zero angle of attack encounters a vertical gust in an otherwise uniform flow, it experiences a force along the chord. This leading-edge suction force is examined for compressible flow with a time-dependent gust. A simple derivation of the thrust force is based on the fact that the leading edge is a singular point so that the flow here is dominated by the leading-edge dipole strength. From the viewpoint of a fluid-fixed observer the fluid does work on the airfoil, and this energy must come from the incident gust. Demonstrating energy conservation is not surprising, but it gives a better understanding of the relationship between the individual energy terms. The derivation shows that the acoustic energy can be calculated using compact assumptions at low frequency, but that it must be calculated non-compactly at high frequency. For a general gust the work done on the airfoil is shown to equal the energy taken from the fluid, the energy transfer occurring at the leading edge. For a sinusoidal gust the energy contained in the incident gust is shown to equal the sum of the energy remaining in the wake, the work done on the airfoil and the acoustic energy radiated away. The relative proportions of the incident energy going to these three energy types depends on the gust frequency, the acoustic radiation becoming more efficient as the frequency increases. For a fixed gust frequency, the thrust force goes to zero at a Mach number of one, and for an incident gust consisting of vorticity on the airfoil axis, the entire energy of the gust is radiated as acoustic energy at this Mach number.

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15

Schulten, Johan B. H. M. "Unsteady leading-edge suction effects on rotor-stator interaction noise." AIAA Journal 38 (January 2000): 1579–85. http://dx.doi.org/10.2514/3.14584.

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16

Reichert, Todd M., and James D. DeLaurier. "Performance of Articulated Flapping Wings with Partial Leading-Edge Suction." Journal of Aircraft 44, no. 4 (July 2007): 1395–98. http://dx.doi.org/10.2514/1.29616.

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17

He, Guosheng, Julien Deparday, Lars Siegel, Arne Henning, and Karen Mulleners. "Stall Delay and Leading-Edge Suction for a Pitching Airfoil with Trailing-Edge Flap." AIAA Journal 58, no. 12 (December 2020): 5146–55. http://dx.doi.org/10.2514/1.j059719.

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18

Maqsood, Adnan, and Tiauw Hiong Go. "Aerodynamic Estimation of Annular Wings Based on Leading-Edge Suction Analogy." AIAA Journal 51, no. 2 (February 2013): 529–34. http://dx.doi.org/10.2514/1.j051914.

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19

Traub, Lance W. "Analytic Drag Prediction for Cambered Wings with Partial Leading Edge Suction." Journal of Aircraft 46, no. 1 (January 2009): 312–19. http://dx.doi.org/10.2514/1.38558.

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20

Bloxham, Matthew J., and Jeffrey P. Bons. "Leading-Edge Endwall Suction and Midspan Blowing to Reduce Turbomachinery Losses." Journal of Propulsion and Power 26, no. 6 (November 2010): 1268–75. http://dx.doi.org/10.2514/1.46105.

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21

Riley, N., and J. H. B. Smith. "Prediction of leading-edge vortex behaviour to supplement the suction analogy." Journal of Engineering Mathematics 19, no. 2 (1985): 157–72. http://dx.doi.org/10.1007/bf00042738.

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22

Walraevens, R. E., and N. A. Cumpsty. "Leading Edge Separation Bubbles on Turbomachine Blades." Journal of Turbomachinery 117, no. 1 (January 1, 1995): 115–25. http://dx.doi.org/10.1115/1.2835626.

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Results are presented for separation bubbles of the type that can form near the leading edges of thin compressor or turbine blades. These often occur when the incidence is such that the stagnation point is not on the nose of the aerofoil. Tests were carried out at low speed on a single aerofoil to simulate the range of conditions found on compressor blades. Both circular and elliptic shapes of leading edge were tested. Results are presented for a range of incidence, Reynolds number, and turbulence intensity and scale. The principal quantitative measurements presented are the pressure distributions in the leading edge and bubble region, as well as the boundary layer properties at a fixed distance downstream, where most of the flows had reattached. Reynolds number was found to have a comparatively small influence, but a raised level of free-stream turbulence has a striking effect, shortening or eliminating the bubble and increasing the magnitude of the suction spike. Increased free-stream turbulence also reduces the boundary layer thickness and shape parameter after the bubble. Some explanations of the processes are outlined.

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23

Sparenberg, J. A., and E. M. de Jager. "New Approach to the Suction Force at the Leading Edge of a Profile With Zero Thickness." Journal of Ship Research 48, no. 04 (December 1, 2004): 305–10. http://dx.doi.org/10.5957/jsr.2004.48.4.305.

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This paper considers the suction force at the leading edge of a profile with zero thickness in an incompressible and inviscid fluid flow. The theory is linear, and the approach to the suction force is from the innerside of the profile. It is shown that the suction force can be considered as an "integral" over a delta function of Dirac situated at the nose of the profile. An application of the method is given to show that in the linear theory a nonslotted periodically moving profile that does not shed free vorticity cannot yield a nonzero mean thrust.

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24

Ye, Liuqing, Zhengyin Ye, and Boping Ma. "An active control method for reducing sonic boom of supersonic aircraft." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 39, no. 3 (June 2021): 566–75. http://dx.doi.org/10.1051/jnwpu/20213930566.

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Sonic boom reduction has been an urgent need to develop the future supersonic transport, because of the heavy damages of the noise pollution. This paper provides an active control method for the supersonic aircraft to reduce the sonic boom, wherein a suction slot near the leading edge and an injection slot near the trailing edge on the airfoil suction surface are opened, and the mass flow sucked in near the leading edge is equal to the mass flow injected near the trailing edge. The diamond and 566 airfoils are adopted as the baseline airfoil to verify the capability of the active control method, and the effects of the suction and injection location, the mass flow rate and the attack angle on the ground boom signature, the maximum overpressure, the drag coefficients and the ratio of lift to drag are studied in detail. The results show that the proposed active control method can significantly reduce the sonic boom, and the reduction of the sonic boom intensity is more sensitive to the injection near the trailing edge than the suction near the leading edge. Applying this active control method to the diamond (NACA0008) airfoil, when the mass flow rate is 6.5 kg/s(7.5 kg/s), the value of maximum positive overpressure is decreased by 12.87%(12.85%), the value of maximum negative overpressure is decreased by 33.83%(56.77%) and the drag coefficient is decreased by 9.50%(10.96%). It can be seen that the method proposed in this paper has great benefits in the reduction of sonic boom and provides a useful reference for designing a new generation of lower sonic boom supersonic aircraft.

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25

John, Michael O., Dominik Obrist, and Leonhard Kleiser. "Secondary instability and subcritical transition of the leading-edge boundary layer." Journal of Fluid Mechanics 792 (March 4, 2016): 682–711. http://dx.doi.org/10.1017/jfm.2016.117.

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The leading-edge boundary layer (LEBL) in the front part of swept airplane wings is prone to three-dimensional subcritical instability, which may lead to bypass transition. The resulting increase of airplane drag and fuel consumption implies a negative environmental impact. In the present paper, we present a temporal biglobal secondary stability analysis (SSA) and direct numerical simulations (DNS) of this flow to investigate a subcritical transition mechanism. The LEBL is modelled by the swept Hiemenz boundary layer (SHBL), with and without wall suction. We introduce a pair of steady, counter-rotating, streamwise vortices next to the attachment line as a generic primary disturbance. This generates a high-speed streak, which evolves slowly in the streamwise direction. The SSA predicts that this flow is unstable to secondary, time-dependent perturbations. We report the upper branch of the secondary neutral curve and describe numerous eigenmodes located inside the shear layers surrounding the primary high-speed streak and the vortices. We find secondary flow instability at Reynolds numbers as low as$Re\approx 175$, i.e. far below the linear critical Reynolds number$Re_{crit}\approx 583$of the SHBL. This secondary modal instability is confirmed by our three-dimensional DNS. Furthermore, these simulations show that the modes may grow until nonlinear processes lead to breakdown to turbulent flow for Reynolds numbers above$Re_{tr}\approx 250$. The three-dimensional mode shapes, growth rates, and the frequency dependence of the secondary eigenmodes found by SSA and the DNS results are in close agreement with each other. The transition Reynolds number$Re_{tr}\approx 250$at zero suction and its increase with wall suction closely coincide with experimental and numerical results from the literature. We conclude that the secondary instability and the transition scenario presented in this paper may serve as a possible explanation for the well-known subcritical transition observed in the leading-edge boundary layer.

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26

Karim, M. Ahsanul, and Mukund Acharya. "Suppression of dynamic-stall vortices over pitching airfoils by leading-edge suction." AIAA Journal 32, no. 8 (August 1994): 1647–55. http://dx.doi.org/10.2514/3.12155.

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27

Alrefai, Mah'd, and Mukund Acharya. "Controlled leading-edge suction for management of unsteady separation over pitching airfoils." AIAA Journal 34, no. 11 (November 1996): 2327–36. http://dx.doi.org/10.2514/3.13398.

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28

Goldstein, R. J., H. P. Wang, and M. Y. Jabbari. "Darryl E. Metzger Memorial Session Paper: The Influence of Secondary Flows Near the Endwall and Boundary Layer Disturbance on Convective Transport From a Turbine Blade." Journal of Turbomachinery 117, no. 4 (October 1, 1995): 657–65. http://dx.doi.org/10.1115/1.2836585.

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A naphthalene sublimation technique is used to investigate convective transport from a simulated turbine blade in a stationary linear cascade. In some of the tests undertaken, a trip wire is stretched along the span of the blade near the leading edge. The disturbance produced by tripping the boundary layers on the blade near the leading edge causes early boundary layer transition, creates high mass transfer rate on the pressure side and in the laminar flow region on the suction side, but lowers the transfer rate in the turbulent flow region on the suction side. Comparison is made with other heat and mass transfer studies in the two-dimensional region far from the endwall and good agreement is found. Near the endwall, flow visualization indicates a strong secondary flow pattern. The impact of vortices initiated near the endwall on the laminar–turbulent transition extends three-dimensional effects to about 0.8 chord lengths on the suction side and to about 0.2 chord lengths on the pressure side away from the endwall. The effect of the passage vortex and the new vortex induced by the passage vortex on mass transfer is clearly seen and can be traced along the suction surface of the blade. Close to the endwall the highest mass transfer rate on the suction surface is not found near the leading edge. It occurs at about 27 percent of the curvilinear distance from the stagnation line to the trailing edge where a strong main flow and the secondary passage flow from the pressure side of the adjacent blade interact. The influences of some small but very intense corner vortices and the passage vortex on mass transfer are also observed on both surfaces of the blade.

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29

Li, Shao Hua, Hong Wei Qu, Mei Li Wang, and Ting Ting Guo. "An Experimental Investigation of Flow Characteristics Downstream of Discrete Film Cooling Holes on Turbine Blade Leading Edge." Advanced Materials Research 383-390 (November 2011): 5553–60. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.5553.

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The gas turbine blade was studied on the condition that the mainstream velocity was 10m/s and the Renolds number based on the chord length of the blade was 160000.The Hot-film anemometer was used to measure the two-dimension speed distribution along the downstream of the film cooling holes on the suction side and the pressure side. The conclusions are as follows: When the blowing ratio of the suction side and the pressure side increasing, the the mainstream and the jet injection mixing center raising. Entrainment flow occurs at the position where the blade surface with great curvature gradient, simultaneously the mixing flow has a wicked adhere to the wall. The velocity gradient of the u direction that on the suction side increase obviously, also the level of the wall adherence is better than the pressure side. With the x/d increasing, the velocity u that on the pressure side gradually become irregularly, also the secondary flow emerged near the wall region where the curvature is great. The blowing ratio on the suction side has a little influence on velocity v than that on the pressure side.

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30

Wei, Zhicong, Wei Yang, and Ruofu Xiao. "Pressure Fluctuation and Flow Characteristics in a Two-Stage Double-Suction Centrifugal Pump." Symmetry 11, no. 1 (January 8, 2019): 65. http://dx.doi.org/10.3390/sym11010065.

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Pressure fluctuation is the primary factor that affects the stability of turbomachines. The goal of the present work is to explore the propagation of pressure fluctuations in a two-stage double-suction centrifugal pump. The pressure fluctuation characteristics of each component of a two-stage double-suction centrifugal pump are simulated under four typical flow rates based on the SST k-ω turbulence model. It is shown that the pressure fluctuation frequency at blade passing frequency and its first harmonic is the same at the suction chamber, the leading edge, and the middle of the first-stage impeller, which is different from the rotor–stator interaction. Moreover, the uneven impeller inlet flow distribution will produce fluctuations with rotation frequency and its harmonics at the leading edge of the impellers in both stages. Finally, broadband frequency is found at the trailing edge of the impellers in both stages associated with the first harmonic of the rotation frequency, especially under the part load condition. The large size backflow vortex appears in the blade flow channel leading to the low-pressure zone between the impeller, the tongue, and the start of the partition. That is why the pressure drops significantly twice in one rotation period when the blades pass through the tongue and the start of the partition.

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31

Ramesh, Kiran, Ashok Gopalarathnam, Kenneth Granlund, Michael V. Ol, and Jack R. Edwards. "Discrete-vortex method with novel shedding criterion for unsteady aerofoil flows with intermittent leading-edge vortex shedding." Journal of Fluid Mechanics 751 (June 23, 2014): 500–538. http://dx.doi.org/10.1017/jfm.2014.297.

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AbstractUnsteady aerofoil flows are often characterized by leading-edge vortex (LEV) shedding. While experiments and high-order computations have contributed to our understanding of these flows, fast low-order methods are needed for engineering tasks. Classical unsteady aerofoil theories are limited to small amplitudes and attached leading-edge flows. Discrete-vortex methods that model vortex shedding from leading edges assume continuous shedding, valid only for sharp leading edges, or shedding governed by ad-hoc criteria such as a critical angle of attack, valid only for a restricted set of kinematics. We present a criterion for intermittent vortex shedding from rounded leading edges that is governed by a maximum allowable leading-edge suction. We show that, when using unsteady thin aerofoil theory, this leading-edge suction parameter (LESP) is related to the $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}A_0$ term in the Fourier series representing the chordwise variation of bound vorticity. Furthermore, for any aerofoil and Reynolds number, there is a critical value of the LESP, which is independent of the motion kinematics. When the instantaneous LESP value exceeds the critical value, vortex shedding occurs at the leading edge. We have augmented a discrete-time, arbitrary-motion, unsteady thin aerofoil theory with discrete-vortex shedding from the leading edge governed by the instantaneous LESP. Thus, the use of a single empirical parameter, the critical-LESP value, allows us to determine the onset, growth, and termination of LEVs. We show, by comparison with experimental and computational results for several aerofoils, motions and Reynolds numbers, that this computationally inexpensive method is successful in predicting the complex flows and forces resulting from intermittent LEV shedding, thus validating the LESP concept.

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32

Hodson, H. P., and J. S. Addison. "Wake–Boundary Layer Interactions in an Axial Flow Turbine Rotor at Off-Design Conditions." Journal of Turbomachinery 111, no. 2 (April 1, 1989): 181–92. http://dx.doi.org/10.1115/1.3262254.

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A series of experimental investigations has been undertaken in a single-stage low-speed turbine. The measurements involved rotor blade surface flow visualization, surface-mounted hot-film anemometry, and exit pitot traverses. The effects of varying the flow coefficient and Reynolds number upon the performance of the rotor blade at midspan are described. At the design flow coefficient (φ = 0.495), the rotor pressure surface flow may be regarded as laminar, while on the suction surface, laminar flow gives way to unsteady stator wake-induced transition and then to turbulent flow. Over the range of Reynolds numbers investigated (1.8×105–3.3×105), the rotor midspan performance is dominated by the suction surface transition process; suction surface separation is prevented and the rotor midspan loss coefficient remains approximately constant throughout the range. At positive incidence, suction surface leading edge separation and transition are caused by a velocity overspeed. Reattachment occurs as the flow begins to accelerate toward the throat. The loss associated with the separation becomes significant with increasing incidence. At negative incidence, a velocity overspeed causes leading edge separation of the pressure side boundary layers. Reattachment generally occurs without full transition. The suction surface flow is virtually unaffected. Therefore, the rotor midspan profile loss remains unchanged from the zero incidence value until pressure side stall occurs.

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Li, Chenhao, David Poling, and David Wu. "Induced drag based on leading edge suction for a helicopter in forward flight." AIAA Journal 28, no. 2 (February 1990): 201–4. http://dx.doi.org/10.2514/3.10375.

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John, Michael O., Dominik Obrist, and Leonhard Kleiser. "Stabilisation of subcritical bypass transition in the leading-edge boundary layer by suction." Journal of Turbulence 15, no. 11 (July 31, 2014): 795–805. http://dx.doi.org/10.1080/14685248.2014.933226.

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35

Zhou, Zhiyu, Haiwang Li, Haichao Wang, Gang Xie, and Ruquan You. "Film cooling of cylindrical holes on turbine blade suction side near leading edge." International Journal of Heat and Mass Transfer 141 (October 2019): 669–79. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2019.07.028.

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36

Guowei, Yang, Wang Shanwu, Liu Ningyu, and Zhuang Lixian. "Control of unsteady vortical lift on an airfoil by leading-edge blowing-suction." Acta Mechanica Sinica 13, no. 4 (November 1997): 304–12. http://dx.doi.org/10.1007/bf02487189.

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37

Chen, Long, and Chao Zhou. "Linearized Aerodynamic Modeling of Flapping Rotary Wings by Rotating the Leading-Edge Suction." AIAA Journal 59, no. 5 (May 2021): 1884–90. http://dx.doi.org/10.2514/1.j060230.

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38

Vasudeva Karanth, K., and N. Yagnesh Sharma. "Numerical analysis of a centrifugal fan for performance enhancement using boundary layer suction slots." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 8 (January 12, 2010): 1665–78. http://dx.doi.org/10.1243/09544062jmes1990.

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Flow in centrifugal fans tends to be in a state of instability with flow separation zones on both the suction surface and the front shroud. The overall efficiency of the diffusion process in a centrifugal fan could be enhanced by judiciously introducing the boundary layer suction slots. With easy accessibility of computational fluid dynamics (CFD) as an analytical tool, an extensive numerical whole field analysis of the effect of boundary layer suction slots in discrete regions of suspected separation points is possible. This article attempts to explore the effect of boundary layer suction slots corresponding to various geometrical locations on the impeller as well as on the diffuser. The analysis shows that the suction slots located on the impeller blade near to its trailing edge appreciably improves the static pressure recovery across the fan. Slots provided at a radial distance of 30 per cent from the leading edge of the diffuser vane also significantly contribute to the static pressure recovery across the fan.

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Guan, Peng, Yanting Ai, Yi Xu, Ming Zhao, and Jing Tian. "Numerical Study on the Effect of Thermocouple Mounting Coating on Temperature Measurement of Nozzle Guide Vane." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 38, no. 1 (February 2020): 95–103. http://dx.doi.org/10.1051/jnwpu/20203810095.

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To analyze the measurement error of thermocouple covered by mounting coating, which is mainly used in air-engine nozzle guide vane temperature test, a mathematical model of the temperature measurement structure was established referring to Mark Ⅱ nozzle guide vane. Based on the heat-flow coupling theory and conjugate heat transfer analysis, the Navier-Stokes equations and heat transfer problem were solved by using SST γ-θ turbulence model. The effects of coating position, coating thickness and coating edge fillet on the temperature of test positions were investigated, respectively. From this study, we find that the temperature predicted by SST γ-θ turbulence model well caters for the test data. The maximum error between calculation and test result is less than 10%. When the leading edge coating is near to the transition point of the suction side, the temperature error will increase. Comparing with that on the middle surface of the pressure side and the leading surface of the suction side, the thermocouple coating has slight effect on the temperature measurement accuracy of the middle surface and the trailing surface of the suction side. If the coating thickness is less than the total temperature boundary layer thickness, the measurement accuracy is almost unaffected. To apply a fillet to the leading edge of thermocouple coating is an effective method to improve the measurement accuracy.

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Ashwin Kumar, B., P. Kumar, S. Das, and JK Prasad. "Effect of leading edge shapes on 81°/45° double-delta wing at low speeds." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, no. 16 (August 10, 2017): 3100–3107. http://dx.doi.org/10.1177/0954410017724822.

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Investigations were performed on an 81°/45° sweep double-delta wing at a freestream velocity of 20 m/s. Experiments consisted of the measurement of forces, static pressures, and surface flow visualizations. Effect of the leading edge shapes of the double-delta wing was studied. Results indicated a strong influence of the leading edge shape on the aerodynamic performance of the body. The increase in the bluntness of the leading edge augments the suction pressure and delays the vortex lift phenomena at higher angles of attack, which in turn enhances the lift over the wing. A reasonable agreement between the experiments and computations were observed.

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Hu, Yong, Paul M. Jones, and Kangjie Li. "Air Bearing Dynamics of Sub-Ambient Pressure Sliders During Dynamic Unload." Journal of Tribology 121, no. 3 (July 1, 1999): 553–59. http://dx.doi.org/10.1115/1.2834103.

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The increasing effort to use sub-ambient pressure air bearing sliders for dynamic load/unload applications in magnetic hard disk drives requires desirable air bearing characteristics during the dynamic unload event. This paper establishes air bearing design criteria for achieving a smooth head unload performance, through a correlation study between the modeled unloading air bearing dynamics of two 30 percent proximity recording sub-ambient pressure sliders and motion sequence of the same sliders by a high-speed video camera. It is shown that the air bearing lifting force quickly responds to changes in fly height and pitch, while the suction force is relatively resistant to changes in fly height, but somewhat more sensitive to changes in pitch. This unique distinction results in different decreasing rates between the air bearing lifting and suction forces during the unload process, creating a strong dependence of the unloading characteristics on the location of the suction cavities. Both the modeled unloading air bearing dynamics and experimentally recorded motion sequence illustrate that a toward-trailing-edge located suction force acts to pitch the slider up, while the moment produced by a toward-leading-edge located suction force induces a negative pitch motion, resulting in an excessive flexure deformation and dimple separation. Therefore, placing the suction cavities towards the trailing edge offers a reliable unloading performance for the sub-ambient pressure air bearing sliders.

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Han, S., and R. J. Goldstein. "Influence of Blade Leading Edge Geometry on Turbine Endwall Heat (Mass) Transfer." Journal of Turbomachinery 128, no. 4 (February 1, 2005): 798–813. http://dx.doi.org/10.1115/1.2221326.

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The secondary flows, including passage and other vortices in a turbine cascade, cause significant aerodynamic losses and thermal gradients. Leading edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading edge modified blade has not been investigated thoroughly. Since a fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a fillet geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having a modified leading edge by adding a fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the fillets. Apparently the corner vortices are intensified with the leading edge modified blade.

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Deparday, Julien, and Karen Mulleners. "Modeling the interplay between the shear layer and leading edge suction during dynamic stall." Physics of Fluids 31, no. 10 (October 1, 2019): 107104. http://dx.doi.org/10.1063/1.5121312.

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Dewynne, J. N., S. D. Howison, J. R. Ockendon, L. C. Morland, and E. J. Watson. "Slot suction from inviscid channel flow." Journal of Fluid Mechanics 200 (March 1989): 265–82. http://dx.doi.org/10.1017/s0022112089000650.

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Motivated by a problem in turbine blade cooling, we consider suction from an inviscid channel flow into a slot in the channel wall. The flow is assumed to separate smoothly from the leading edge of the slot and the pressure in the stagnant separated region controls the suction. The mass flux into the slot is found in terms of the pressure; for small values of this flux the predicted flow pattern is found to be quite different from that which would result if there were no separated region. In particular, the stagnation point never penetrates more than approximately 0.05 slot widths into the slot.

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Lamar, J. "A career in vortices and edge forces." Aeronautical Journal 116, no. 1176 (February 2012): 101–52. http://dx.doi.org/10.1017/s0001924000006667.

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Abstract This lecture recognises the background and distinguished work of Frederick William Lanchester, and notes that my background has a few similarities with his. These include a shared interest in wings, lift and vortices. My career at the NASA Langley Research Center spans the time-frame from America’s Super Sonic Transport through 2009. An early emphasis involved wind-tunnel testing of research aircraft models and the development of computer codes for subsonic aerodynamics of wing planforms. These attached-flow codes were applied to various configurations, including those with variable-sweep, dihedral, and more than one planform in both the analysis- and design-modes. These codes were used to provide a connection between leading-edge-forces and the associated additional lift on delta-wings with shed-vortex systems through the leading-edge suction analogy of Edward C. Polhamus. Subsequently, I extended the suction analogy to configurations with side-edges to predict the vortical-flow aerodynamics on complex configurations, including wing-strake combinations. These analysis codes could also be used in a design-by-analysis mode for configurations with leading-edge shed vortices. Later, I was involved in vortical-flow flight research with the F-106B and the F-16XL aircraft at cruise and maneuver conditions. Associated CFD predictions, generated by me and other members of the RTO/AVT-113 task group, have increased our understanding of the flight flow-physics measured on the F-16XL aircraft.

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Rakibuzzaman, Md, Keum-Young Jung, and Sang-Ho Suh. "A study on the use of existing pump as turbine." E3S Web of Conferences 128 (2019): 06004. http://dx.doi.org/10.1051/e3sconf/201912806004.

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Cavitation is an abnormal physical phenomenon which occurs in relatively low–pressure regions in turbomachinery such as pumps and hydraulic turbines. A comparison between the pump and turbine cavitation behavior is a significant and essential process. The work investigates feasibility of turbineusing existing pump and a comparative study of the cavitation characteristics on a centrifugal pump asturbine numerically and experimentally. The current work adopted the Rayleigh–Plesset cavitation model as the source term for inter–phase mass transfer to predict cavitation characteristics.The experimental data were compared with the numerical results and were found to be in good agreement.Results of the comparative study showed that cavitation first occurred at the suction leading edge on the impeller blades and attached cavitation observed on the impeller blade at the lower suction head in pump mode; however, for the turbine mode, the development of vortex cavitation happened at the runner outlet near thetrailing edge on the impeller blades. Also, in the pump, the cavitation became largerfromshroud to the hub and the cavitation rapidly extended from the suction side to the pressure side. On the other hand in the turbine mode, as the cavitation number decreased more vapor bubbles are drawnup at the runner outlet near trailing edge on the blade suction side.

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Mahmood, G. I., R. Gustafson, and S. Acharya. "Experimental Investigation of Flow Structure and Nusselt Number in a Low-Speed Linear Blade Passage With and Without Leading-Edge Fillets." Journal of Heat Transfer 127, no. 5 (May 1, 2005): 499–512. http://dx.doi.org/10.1115/1.1865218.

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The potential of contouring the leading edge of a blade to control the development of the secondary flows in the blade passage and to reduce the thermal loading to the end wall is investigated experimentally. Fillets placed at the junctions of the leading edge and the end wall are used for contouring. Four different types of fillet profiles are tested in a low-speed linear cascade a Reynolds numbers of 233,000 based on the inlet velocity. Images of instantaneous smoke flow patterns show a smaller horseshoe vortex along the leading edge with the fillets. In the passage, the fillets cause the passage vortex to be located closer to the suction surface. Upstream of the throat, the normalized axial vorticity values for the passage vortex and the turbulence intensity levels are smaller with the fillets compared to the baseline. For the leading-edge fillet with a concave profile, the end-wall Nusselt number distributions show significant reductions compared to the baseline.

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MILLS, RICHARD, JOHN SHERIDAN, and KERRY HOURIGAN. "Particle image velocimetry and visualization of natural and forced flow around rectangular cylinders." Journal of Fluid Mechanics 478 (March 10, 2003): 299–323. http://dx.doi.org/10.1017/s0022112002003439.

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Particle image velocimetry (PIV) measurements and flow visualization in a water tunnel show that vortex shedding at the leading and trailing edges of rectangular cylinders can be simultaneously phase-locked to transverse velocity perturbations when the applied perturbation Stp is close to an impinging leading-edge vortex/trailing-edge vortex shedding (ILEV/TEVS) frequency. The transverse perturbations, analogous to β-mode duct acoustic resonances, are generated through harmonic oscillations of the sidewalls. When this occurs, the leading-edge vortices are found always to pass the trailing edge at the same phase in the perturbation cycle regardless of the chord-to-thickness (c/t) ratio. Applying perturbations at an Stp not equal to the natural global frequency also results in phase-locked vortex shedding from the leading edge, and a near wake with a frequency equal to the perturbation frequency. This is consistent with previous experimental findings. However, vortex shedding at the trailing edge is either weaker or non-existent. PIV results and flow visualization showed trailing-edge vortex growth was weaker because leading-edge vortices arrive at the trailing edge at a phase in the perturbation cycle where they interfere with trailing-edge shedding. The frequencies at which trailing-edge vortices form for different c/t ratios correspond to the natural ILEV/TEVS frequencies. As in the case of natural shedding, peaks in base suction occur when the leading-edge vortices pass the trailing edge at the phase in the perturbation cycle (and thus in the leading-edge shedding cycle) that allows strong trailing-edge shedding. This is the reason for the similarity in the Stvs.c/t relationship for three seemingly different sets of experiments.

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Akkala, James M., and James H. J. Buchholz. "Vorticity transport mechanisms governing the development of leading-edge vortices." Journal of Fluid Mechanics 829 (September 22, 2017): 512–37. http://dx.doi.org/10.1017/jfm.2017.559.

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The sequence of events constituting the formation of a leading-edge vortex (LEV) has been investigated for a periodically plunging nominally two-dimensional flat plate and a similarly articulated plate of aspect ratio two. Particle image velocimetry applied in multiple parallel planes and unsteady surface pressure measurements were used to quantify the sources and sinks of vorticity governing the growth of circulation in a control region moving with the plate in each case. In the two-dimensional case, the initial accumulation of (negative) vorticity in the nascent LEV produces a strong surface diffusive flux of vorticity that erodes the connection between the LEV and downstream boundary layer through cross-cancelation, initiating the ‘roll up’ of the LEV. Despite the significant diffusive flux earlier in the vortex development, there is no significant accumulation of secondary vorticity until after the severing occurs. The growth of the secondary vortex reduces the suction near the leading edge, such as to result in a self-limiting mechanism on the diffusive flux. In the finite-aspect-ratio case, a similar development is observed, except that the formation process is regulated or reversed by the spanwise convection of vorticity, which opposes the action of the surface diffusive flux. The physical mechanisms of vortex formation or reversal identified here can provide a basis for the design of passive or active flow control strategies to regulate vortex development.

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Zhang, Shuwei, Renhui Zhang, Sidai Zhang, and Junhu Yang. "Effect of Impeller Inlet Geometry on Cavitation Performance of Centrifugal Pumps Based on Radial Basis Function." International Journal of Rotating Machinery 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/6048263.

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Aiming at the cavitation problem, the blade leading edge shape has been changed to analyze its impact on the cavitation performance for centrifugal pumps. And the response model has been established based on the Radial Basis Function. The calculation case results show that the leading edge extending forward along the shroud can improve the inlet flow condition and cavitation performance. But the cavitation performance has been reduced immensely when the leading edge extends backward along the shroud. Along with the leading edge which extends forward along the hub, the cavitation performance increases at first and then decreases. A better cavitation performance for centrifugal pumps has lower load of blade inlet and higher pressure of blade suction side. The pressure pulsation is affected by the vortex out of the impeller and the falling-off and collapsing of the cavitation bubbles. The lower the pressure pulsation for blade passing frequency and the second harmonics of the samples is, the better the cavitation performance is. A relatively accurate response model based on the Radial Basis Function has been established to predict the effect of the shape of blade leading edge on the cavitation performance of centrifugal pumps.

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Journal articles on the topic 'Leading-edge suction'

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