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C. R. Smith - One of the best experts on this subject based on the ideXlab platform.
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Boundary Layer Influence on the Unsteady Horseshoe Vortex Flow and Surface Heat Transfer
Journal of Turbomachinery, 2008Co-Authors: Daniel R. Sabatino, C. R. SmithAbstract:The spatial-temporal flow field and associated surface heat transfer within the leading edge, end-wall region of a bluff body were examined using both particle image velocimetry and thermochromic liquid crystal temperature measurements. The Horseshoe Vortex system in the end-wall region is mechanistically linked to the upstream boundary layer unsteadiness. Hairpin Vortex packets, associated with turbulent boundary layer bursting behavior, amalgamate with the Horseshoe Vortex resulting in unsteady strengthening and streamwise motion. The Horseshoe Vortex unsteadiness exhibits two different natural frequencies: one associated with the transient motion of the Horseshoe Vortex and the other with the transient surface heat transfer. Comparable unsteadiness occurs in the end-wall region of the more complex airfoil geometry of a linear turbine cascade. To directly compare the Horseshoe Vortex behavior around a turning airfoil to that of a simple bluff body, a length scale based on the maximum airfoil thickness is proposed.
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Boundary Layer Influence on the Unsteady Horseshoe Vortex Flow and Surface Heat Transfer
Volume 6: Turbo Expo 2007 Parts A and B, 2007Co-Authors: Daniel R. Sabatino, C. R. SmithAbstract:The spatial-temporal flow-field and associated surface heat transfer within the leading edge, end-wall region of a bluff body were examined using both particle image velocimetry and thermochromic liquid crystal temperature measurements. The Horseshoe Vortex system in the end-wall region is mechanistically linked to the upstream boundary layer unsteadiness. Hairpin Vortex packets, associated with turbulent boundary layer bursting behavior, amalgamate with the Horseshoe Vortex resulting in unsteady strengthening and streamwise motion. The Horseshoe Vortex unsteadiness exhibits two different natural frequencies: one associated with the transient motion of the Horseshoe Vortex, and the other with the transient surface heat transfer. Comparable unsteadiness occurs in the end-wall region of the more complex airfoil geometry of a linear turbine cascade. To directly compare the Horseshoe Vortex behavior around a turning airfoil to that of a simple bluff body, a length scale based on the maximum airfoil thickness is proposed.Copyright © 2007 by ASME
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the dynamics of the Horseshoe Vortex and associated endwall heat transfer part ii time mean results
Journal of Turbomachinery-transactions of The Asme, 2006Co-Authors: T. J. Praisner, C. R. SmithAbstract:Time-mean endwall heat transfer and flow-field data in the endwall region are presented for a turbulent juncture flow formed with a symmetric bluff body. The experimental technique employed allowed the simultaneous recording of instantaneous particle image velocimetry flow field data, and thermochromic liquid-crystal-based endwall heat transfer data. The time-mean flow field on the symmetry plane is characterized by the presence of primary (Horseshoe), secondary, tertiary, and corner vortices. On the symmetry plane the time-mean Horseshoe Vortex displays a bimodal vorticity distribution and a stable-focus streamline topology indicative of Vortex stretching. Off the symmetry plane, the Horseshoe Vortex grows in scale, and ultimately experiences a bursting, or breakdown, upon experiencing an adverse pressure gradient. The time-mean endwall heat transfer is dominated by two bands of high heat transfer, which circumscribe the leading edge of the bluff body. The band of highest heat transfer occurs in the corner region of the juncture, reflecting a 350% increase over the impinging turbulent boundary layer. A secondary high heat-transfer band develops upstream of the primary band, reflecting a 250% heat transfer increase, and is characterized by high levels of fluctuating heat load. The mean upstream position of the Horseshoe Vortex is coincident with a region of relatively low heat transfer that separates the two bands of high heat transfer.
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The Dynamics of the Horseshoe Vortex and Associated Endwall Heat Transfer—Part I: Temporal Behavior
Journal of Turbomachinery, 2005Co-Authors: T. J. Praisner, C. R. SmithAbstract:Instantaneous flow topology and the associated endwall heat transfer in the leading-edge endwall region of a symmetric airfoil are presented. An experimental technique was employed that allowed the simultaneous recording of instantaneous particle image velocimetry flow field and thermochromic liquid-crystal-based endwall heat transfer data. The endwall flow is dominated by a Horseshoe Vortex that forms from reorganized impinging boundary layer vorticity. A relatively small Vortex is shown to be a steady feature of the corner region, while a secondary Vortex develops sporadically immediately upstream of the Horseshoe Vortex. The region upstream of the Horseshoe Vortex is characterized by a bimodal switching of the near-wall reverse flow, which results in quasiperiodic eruptions of the secondary Vortex. The bimodal switching of the reverse flow in the vicinity of the secondary Vortex is linked to the temporal behavior of the down-wash fluid on the leading edge of the foil. Frequency analysis of the flow field and endwall heat transfer data, taken together, indicate that the eruptive behavior associated with the Horseshoe Vortex occurs at a frequency that is essentially the same as the measured turbulence bursting period of the impinging turbulent endwall boundary layer.
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The Dynamics of the Horseshoe Vortex and Associated Endwall Heat Transfer—Part II: Time-Mean Results
Journal of Turbomachinery, 2005Co-Authors: T. J. Praisner, C. R. SmithAbstract:Time-mean endwall heat transfer and flow-field data in the endwall region are presented for a turbulent juncture flow formed with a symmetric bluff body. The experimental technique employed allowed the simultaneous recording of instantaneous particle image velocimetry flow field data, and thermochromic liquid-crystal-based endwall heat transfer data. The time-mean flow field on the symmetry plane is characterized by the presence of primary (Horseshoe), secondary, tertiary, and corner vortices. On the symmetry plane the time-mean Horseshoe Vortex displays a bimodal vorticity distribution and a stable-focus streamline topology indicative of Vortex stretching. Off the symmetry plane, the Horseshoe Vortex grows in scale, and ultimately experiences a bursting, or breakdown, upon experiencing an adverse pressure gradient. The time-mean endwall heat transfer is dominated by two bands of high heat transfer, which circumscribe the leading edge of the bluff body. The band of highest heat transfer occurs in the corner region of the juncture, reflecting a 350% increase over the impinging turbulent boundary layer. A secondary high heat-transfer band develops upstream of the primary band, reflecting a 250% heat transfer increase, and is characterized by high levels of fluctuating heat load. The mean upstream position of the Horseshoe Vortex is coincident with a region of relatively low heat transfer that separates the two bands of high heat transfer.
T. J. Praisner - One of the best experts on this subject based on the ideXlab platform.
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the dynamics of the Horseshoe Vortex and associated endwall heat transfer part ii time mean results
Journal of Turbomachinery-transactions of The Asme, 2006Co-Authors: T. J. Praisner, C. R. SmithAbstract:Time-mean endwall heat transfer and flow-field data in the endwall region are presented for a turbulent juncture flow formed with a symmetric bluff body. The experimental technique employed allowed the simultaneous recording of instantaneous particle image velocimetry flow field data, and thermochromic liquid-crystal-based endwall heat transfer data. The time-mean flow field on the symmetry plane is characterized by the presence of primary (Horseshoe), secondary, tertiary, and corner vortices. On the symmetry plane the time-mean Horseshoe Vortex displays a bimodal vorticity distribution and a stable-focus streamline topology indicative of Vortex stretching. Off the symmetry plane, the Horseshoe Vortex grows in scale, and ultimately experiences a bursting, or breakdown, upon experiencing an adverse pressure gradient. The time-mean endwall heat transfer is dominated by two bands of high heat transfer, which circumscribe the leading edge of the bluff body. The band of highest heat transfer occurs in the corner region of the juncture, reflecting a 350% increase over the impinging turbulent boundary layer. A secondary high heat-transfer band develops upstream of the primary band, reflecting a 250% heat transfer increase, and is characterized by high levels of fluctuating heat load. The mean upstream position of the Horseshoe Vortex is coincident with a region of relatively low heat transfer that separates the two bands of high heat transfer.
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The Dynamics of the Horseshoe Vortex and Associated Endwall Heat Transfer—Part I: Temporal Behavior
Journal of Turbomachinery, 2005Co-Authors: T. J. Praisner, C. R. SmithAbstract:Instantaneous flow topology and the associated endwall heat transfer in the leading-edge endwall region of a symmetric airfoil are presented. An experimental technique was employed that allowed the simultaneous recording of instantaneous particle image velocimetry flow field and thermochromic liquid-crystal-based endwall heat transfer data. The endwall flow is dominated by a Horseshoe Vortex that forms from reorganized impinging boundary layer vorticity. A relatively small Vortex is shown to be a steady feature of the corner region, while a secondary Vortex develops sporadically immediately upstream of the Horseshoe Vortex. The region upstream of the Horseshoe Vortex is characterized by a bimodal switching of the near-wall reverse flow, which results in quasiperiodic eruptions of the secondary Vortex. The bimodal switching of the reverse flow in the vicinity of the secondary Vortex is linked to the temporal behavior of the down-wash fluid on the leading edge of the foil. Frequency analysis of the flow field and endwall heat transfer data, taken together, indicate that the eruptive behavior associated with the Horseshoe Vortex occurs at a frequency that is essentially the same as the measured turbulence bursting period of the impinging turbulent endwall boundary layer.
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The Dynamics of the Horseshoe Vortex and Associated Endwall Heat Transfer—Part II: Time-Mean Results
Journal of Turbomachinery, 2005Co-Authors: T. J. Praisner, C. R. SmithAbstract:Time-mean endwall heat transfer and flow-field data in the endwall region are presented for a turbulent juncture flow formed with a symmetric bluff body. The experimental technique employed allowed the simultaneous recording of instantaneous particle image velocimetry flow field data, and thermochromic liquid-crystal-based endwall heat transfer data. The time-mean flow field on the symmetry plane is characterized by the presence of primary (Horseshoe), secondary, tertiary, and corner vortices. On the symmetry plane the time-mean Horseshoe Vortex displays a bimodal vorticity distribution and a stable-focus streamline topology indicative of Vortex stretching. Off the symmetry plane, the Horseshoe Vortex grows in scale, and ultimately experiences a bursting, or breakdown, upon experiencing an adverse pressure gradient. The time-mean endwall heat transfer is dominated by two bands of high heat transfer, which circumscribe the leading edge of the bluff body. The band of highest heat transfer occurs in the corner region of the juncture, reflecting a 350% increase over the impinging turbulent boundary layer. A secondary high heat-transfer band develops upstream of the primary band, reflecting a 250% heat transfer increase, and is characterized by high levels of fluctuating heat load. The mean upstream position of the Horseshoe Vortex is coincident with a region of relatively low heat transfer that separates the two bands of high heat transfer.
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The Dynamics of the Horseshoe Vortex and Associated Endwall Heat Transfer: Part I — Temporal Behavior
Volume 3: Turbo Expo 2005 Parts A and B, 2005Co-Authors: T. J. Praisner, C. R. SmithAbstract:Instantaneous flow topology and the associated endwall heat transfer in the leading-edge endwall region of a symmetric airfoil are presented. An experimental technique was employed that allowed the simultaneous recording of instantaneous particle image velocimetry flow field and thermochromic liquid-crystal-based endwall heat transfer data. The endwall flow is dominated by a Horseshoe Vortex that forms from reorganized impinging boundary layer vorticity. A corner Vortex is shown to be a steady feature of the corner region, while a secondary Vortex develops sporadically immediately upstream of the Horseshoe Vortex. The region upstream of the Horseshoe Vortex is characterized by a bimodal switching of the near-wall reverse flow, which results in quasi-periodic eruptions of the secondary Vortex. The bimodal switching of the reverse flow in the vicinity of the secondary Vortex is linked to the temporal behavior of the down-wash fluid on the leading edge of the foil. Frequency analysis of the flow field and endwall heat transfer data, taken together, indicate that the eruptive behavior associated with the Horseshoe Vortex occurs at a frequency that is essentially the same as the measured turbulence bursting period of the impinging turbulent endwall boundary layer.Copyright © 2005 by ASME
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the dynamics of the Horseshoe Vortex and associated endwall heat transfer part i temporal behavior
ASME Turbo Expo 2005: Power for Land Sea and Air, 2005Co-Authors: T. J. Praisner, C. R. SmithAbstract:Instantaneous flow topology and the associated endwall heat transfer in the leading-edge endwall region of a symmetric airfoil are presented. An experimental technique was employed that allowed the simultaneous recording of instantaneous particle image velocimetry flow field and thermochromic liquid-crystal-based endwall heat transfer data. The endwall flow is dominated by a Horseshoe Vortex that forms from reorganized impinging boundary layer vorticity. A corner Vortex is shown to be a steady feature of the corner region, while a secondary Vortex develops sporadically immediately upstream of the Horseshoe Vortex. The region upstream of the Horseshoe Vortex is characterized by a bimodal switching of the near-wall reverse flow, which results in quasi-periodic eruptions of the secondary Vortex. The bimodal switching of the reverse flow in the vicinity of the secondary Vortex is linked to the temporal behavior of the down-wash fluid on the leading edge of the foil. Frequency analysis of the flow field and endwall heat transfer data, taken together, indicate that the eruptive behavior associated with the Horseshoe Vortex occurs at a frequency that is essentially the same as the measured turbulence bursting period of the impinging turbulent endwall boundary layer.Copyright © 2005 by ASME
Shyh-jiunn Shieh - One of the best experts on this subject based on the ideXlab platform.
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characteristics of Horseshoe Vortex system near a vertical plate base plate juncture
Experimental Thermal and Fluid Science, 2002Co-Authors: Chang Lin, Peng-hao Chiu, Shyh-jiunn ShiehAbstract:Abstract In-depth study of Horseshoe Vortex flows, near the juncture of a vertical plate and a base plate, is performed using flow visualization technique, fiber laser Doppler velocimetry and particle image velocimetry systems. The flow patterns are classified into four major categories while the Reynolds number, based on the free stream velocity and the width of vertical plate, varies from 400 to 11 000, and the height-to-width ratio changes from 0.5 to 4.0. These four major categories are defined as (1) steady Vortex system, (2) periodic oscillation Vortex system with small displacement, (3) periodic breakaway Vortex system, and (4) turbulent-like Vortex system. In the categories of periodic oscillation Vortex system with small displacement and periodic breakaway Vortex system, the Strouhal number increases with increasing Reynolds number if the width of the vertical plate is employed in the non-dimensional parameters. However, when the uniform flow speed and the height of vertical plate are maintained the same, the frequency of periodic oscillation and periodic breakaway Vortex systems do not increase with the increasing width. This indicates that the width of vertical plate is not a characteristic length that affects the frequency of the periodic motion of the Horseshoe Vortex system. Conversely, the Strouhal numbers, based on the boundary layer thickness, change from 0.0611 to 0.0896 and are found to be nearly independent of the Reynolds numbers. This clearly reveals that the boundary layer thickness is an important length scale that controls the frequency of the Horseshoe Vortex system.
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Characteristics of Horseshoe Vortex system near a vertical plate–base plate juncture
Experimental Thermal and Fluid Science, 2002Co-Authors: Chang Lin, Peng-hao Chiu, Shyh-jiunn ShiehAbstract:Abstract In-depth study of Horseshoe Vortex flows, near the juncture of a vertical plate and a base plate, is performed using flow visualization technique, fiber laser Doppler velocimetry and particle image velocimetry systems. The flow patterns are classified into four major categories while the Reynolds number, based on the free stream velocity and the width of vertical plate, varies from 400 to 11 000, and the height-to-width ratio changes from 0.5 to 4.0. These four major categories are defined as (1) steady Vortex system, (2) periodic oscillation Vortex system with small displacement, (3) periodic breakaway Vortex system, and (4) turbulent-like Vortex system. In the categories of periodic oscillation Vortex system with small displacement and periodic breakaway Vortex system, the Strouhal number increases with increasing Reynolds number if the width of the vertical plate is employed in the non-dimensional parameters. However, when the uniform flow speed and the height of vertical plate are maintained the same, the frequency of periodic oscillation and periodic breakaway Vortex systems do not increase with the increasing width. This indicates that the width of vertical plate is not a characteristic length that affects the frequency of the periodic motion of the Horseshoe Vortex system. Conversely, the Strouhal numbers, based on the boundary layer thickness, change from 0.0611 to 0.0896 and are found to be nearly independent of the Reynolds numbers. This clearly reveals that the boundary layer thickness is an important length scale that controls the frequency of the Horseshoe Vortex system.
Tu Chengxu - One of the best experts on this subject based on the ideXlab platform.
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Method to Control Unsteady Force of Submarine Propeller Based on the Control of Horseshoe Vortex
Journal of Ship Research, 2012Co-Authors: Liu Zhihua, Xiong Ying, Tu ChengxuAbstract:The submarine propeller works in the submarine wake with severe circumferential nonuniformity, which causes the hydrodynamic force to act on the blade. This results in severe oscillation with the rotation of the propeller and impairs the hydrodynamics and noise performance of the submarine propeller. The Horseshoe Vortex generated at the hull-appendages junctions of the submarine has important influence on wake uniformity. In the present study, the state of the submarine Horseshoe Vortex is analyzed and a new method of Vortex control baffler is presented. The aim is to weaken the Horseshoe Vortex. Based on the wind tunnel experiment and numerical simulation on the submarine model, the Vortex control baffler can decrease the strength of the submarine Horseshoe Vortex and improve the uniformity of the submarine wake. Vortex control bafflers adapted for the fully appended SUBOFF model are designed, and the unsteady force of three kinds of propellers functioned after the SUBOFF model is calculated numerically. The results show that although the skew angle and blade number are different, the amplitudes of the unsteady force acting on the blades of all three propellers decreased by 50% to 80% due to the effects of the Vortex control baffler.
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Numerical simulation and control of Horseshoe Vortex around an appendage–body junction
Journal of Fluids and Structures, 2011Co-Authors: Liu Zhihua, Xiong Ying, Tu ChengxuAbstract:Abstract The Horseshoe Vortex generated around the appendage–body junction of submarines strongly influences the non-uniformity of submarine wakes at the propeller discs. The flow characteristics around the appended submarine body are numerically simulated and analyzed, and a new method on the Vortex control baffle is presented. Then, the influence of the Vortex control baffle on the Horseshoe Vortex generated at the sail–body junction is numerically studied, and the flow phenomena caused by the Vortex control baffle with different transverse positions is investigated further. Results show that the Vortex control baffle can induce a kind of attached Vortex in a rotational direction opposite to the Horseshoe Vortex; these two kinds of vortices undermine each other. Furthermore, when the transverse position of the Vortex control baffle is close to the Horseshoe Vortex, the state of the Horseshoe Vortex is directly affected, and the flow structure becomes even more complex. We adapt the Vortex control baffle for the Horseshoe Vortex generated at the stern foil–body junction. Results from the numerical simulation of the flow around the fully appended submarine model indicate that the effect of the Vortex control baffle greatly improves the performance of the submarine wake. The circumferential non-uniformity of the axial, tangential, and radial velocity components are decreased markedly. The engineering applicability of the Vortex control baffle has been well presented.
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numerical simulation and control of Horseshoe Vortex around an appendage body junction
Journal of Fluids and Structures, 2011Co-Authors: Liu Zhihua, Xiong Ying, Tu ChengxuAbstract:Abstract The Horseshoe Vortex generated around the appendage–body junction of submarines strongly influences the non-uniformity of submarine wakes at the propeller discs. The flow characteristics around the appended submarine body are numerically simulated and analyzed, and a new method on the Vortex control baffle is presented. Then, the influence of the Vortex control baffle on the Horseshoe Vortex generated at the sail–body junction is numerically studied, and the flow phenomena caused by the Vortex control baffle with different transverse positions is investigated further. Results show that the Vortex control baffle can induce a kind of attached Vortex in a rotational direction opposite to the Horseshoe Vortex; these two kinds of vortices undermine each other. Furthermore, when the transverse position of the Vortex control baffle is close to the Horseshoe Vortex, the state of the Horseshoe Vortex is directly affected, and the flow structure becomes even more complex. We adapt the Vortex control baffle for the Horseshoe Vortex generated at the stern foil–body junction. Results from the numerical simulation of the flow around the fully appended submarine model indicate that the effect of the Vortex control baffle greatly improves the performance of the submarine wake. The circumferential non-uniformity of the axial, tangential, and radial velocity components are decreased markedly. The engineering applicability of the Vortex control baffle has been well presented.
Fotis Sotiropoulos - One of the best experts on this subject based on the ideXlab platform.
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reynolds number effects on the coherent dynamics of the turbulent Horseshoe Vortex system
Flow Turbulence and Combustion, 2011Co-Authors: Cristian Escauriaza, Fotis SotiropoulosAbstract:The adverse pressure gradient induced by a surface-mounted obstacle in a turbulent boundary layer causes the approaching flow to separate and form a dynamically rich Horseshoe Vortex system (HSV) in the junction of the obstacle with the wall. The Reynolds number of the flow (Re) is one of the important parameters that control the rich coherent dynamics of the Vortex, which are known to give rise to low-frequency, bimodal fluctuations of the velocity field (Devenport and Simpson, J Fluid Mech 210:23–55, 1990; Paik et al., Phys Fluids 19:045107, 2007). We carry out detached eddy simulations (DES) of the flow past a circular cylinder mounted on a rectangular channel for Re = 2.0 × 104 and 3.9 × 104 (Dargahi, Exp Fluids 8:1–12, 1989) in order to systematically investigate the effect of the Reynolds number on the HSV dynamics. The computed results are compared with each other and with previous experimental and computational results for a related junction flow at a much higher Reynolds number (Re = 1.15 × 105) (Devenport and Simpson, J Fluid Mech 210:23–55, 1990; Paik et al., Phys Fluids 19:045107, 2007). The computed results reveal significant variations with Re in terms of the mean-flow quantities, turbulence statistics, and the coherent dynamics of the turbulent HSV. For Re = 2.0 × 104 the HSV system consists of a large number of necklace-type vortices that are shed periodically at higher frequencies than those observed in the Re = 3.9 × 104 case. For this latter case the number of large-scale vortical structures that comprise the instantaneous HSV system is reduced significantly and the flow dynamics becomes quasi-periodic. For both cases, we show that the instantaneous flowfields are dominated by eruptions of wall-generated vorticity associated with the growth of hairpin vortices that wrap around and disorganize the primary HSV system. The intensity and frequency of these eruptions, however, appears to diminish rapidly with decreasing Re. In the high Re case the HSV system consists of a single, highly energetic, large-scale necklace Vortex that is aperiodically disorganized by the growth of the hairpin mode. Regardless of the Re, we find pockets in the junction region within which the histograms of velocity fluctuations are bimodal as has also been observed in several previous experimental studies.
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on the bimodal dynamics of the turbulent Horseshoe Vortex system in a wing body junction
Physics of Fluids, 2007Co-Authors: Joongcheol Paik, Cristian Escauriaza, Fotis SotiropoulosAbstract:The turbulent boundary layer approaching a wall-mounted obstacle experiences a strong adverse pressure gradient and undergoes three-dimensional separation leading to the formation of a dynamically rich Horseshoe Vortex (HSV) system. In a pioneering experimental study, Devenport and Simpson [J. Fluid Mech. 210, 23 (1990)] showed that the HSV system forming at the leading edge region of a wing mounted on a flat plate at Re=1.15×105 exhibits bimodal, low-frequency oscillations, which away from the wall produce turbulent energy and stresses one order of magnitude higher than those produced by the conventional shear mechanism in the approaching turbulent boundary layer. We carry out numerical simulations for the experimental configuration of Devenport and Simpson using the detached-eddy-simulation (DES) approach. The DES length scale is adjusted for this flow to alleviate the well known shortcoming of DES; namely that of premature, laminar-like flow separation. The numerical simulations reproduce with good acc...