An exact theory of three-dimensional fixed separation in unsteady flows

Surana, Amit; Jacobs, Gustaaf; Grunberg, Oliver; Haller, George

doi:10.1063/1.2988321

Cited by 39 publications

(26 citation statements)

References 25 publications

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“…For the case of a two-dimensional mean flow, extensive measurements and simulations were reported by Cantwell (1981), Dupont et al (2005), Ganapathisubramani, Clemens & Dolling (2007), Humble, Scarano & van Oudheusden (2007), Dupont et al (2008), Humble et al (2009), Priebe, Wu & Martín (2009), Souverein et al (2010 and DeBonis et al (2012). Relevant mathematical analysis has been presented by Wu et al (2000) and Surana, Grunberg & Haller (2006), Surana et al (2008).…”

Section: Previous Related Sbli Researchmentioning

confidence: 97%

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Shock wave–boundary layer interactions in rectangular inlets: three-dimensional separation topology and critical points

Eagle

Driscoll

2014

J. Fluid Mech.

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The interaction between two separated flow regions was studied for the fundamental problem of a shock wave-boundary layer interaction (SBLI) within a rectangular inlet. One motivation is that the inlet of an engine on a supersonic aircraft may contain separation zones on the sidewalls and the bottom wall; if one region separates first it can alter the flow on the other wall and lead to engine unstart. In our work an oblique shock wave was generated by a wedge suspended from the upper wall of a Mach 2.75 wind tunnel. Stereo particle image velocimetry (PIV) measurements were recorded in 25 planes that include all three possible orthogonal orientations. The lateral velocity and vorticity measurements help to explain the underlying flow structure and these quantities were not measured previously for this problem. It is concluded that the sidewall and bottom wall separation zones interact due to an underlying flow structure that is similar to the two types of 3-D separation patterns previously described by Tobak & Peake (Annu. Rev. Fluid Mech., vol. 14, 1982, pp. 61-85). Separation first occurs at an upstream location where the shock interacts with the sidewall. Lateral velocities direct flow toward the centreline to cause separation on the bottom wall. This causes significant curvature of the shock wave, so that even the region near the tunnel centreline cannot be explained by conventional 2-D concepts. A number of critical points (saddle points, nodes, focus points) were identified. Results are consistent with the general ideas of Burton & Babinsky (J. Fluid Mech., vol. 707, 2012, pp. 287-306) and help to provide details of how the sidewalls redistribute the adverse pressure gradient in space.

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Section: Previous Related Sbli Researchmentioning

confidence: 97%

“…Squire (1961) has demonstrated that oil film lines are accurate markers of the skin friction lines in steady flows. Surana et al (2008) pointed out that applying these concepts to unsteady, compressible flows may lead to errors. However, for qualitative explanations they remain useful.…”

Section: Brief Review Of Critical Point Theorymentioning

confidence: 97%

Shock wave–boundary layer interactions in rectangular inlets: three-dimensional separation topology and critical points

Eagle

Driscoll

2014

J. Fluid Mech.

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“…Also, the structure of WSS lines have been used in developing theories for flow separation using dynamical system methods (Surana et al 2006(Surana et al , 2008. Recently, WSS critical points associated with rare near wall backflow have been observed in turbulent channel flows (Lenaers et al 2012;Brücker 2015).…”

Section: Introductionmentioning

confidence: 99%

Lagrangian wall shear stress structures and near-wall transport in high-Schmidt-number aneurysmal flows

et al. 2016

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The wall shear stress (WSS) vector field provides a signature for near wall convective transport, and can be scaled to obtain a first order approximation of the near wall fluid velocity. The near wall flow field governs mass transfer problems in convection dominated open flows with high Schmidt number, in which case a flux at the wall will lead to a thin concentration boundary layer. Such near wall transport is of particular interest in cardiovascular flows whereby hemodynamics can initiate and progress biological events at the vessel wall. In this study we consider mass transfer processes in pulsatile blood flow of abdominal aortic aneurysms resulting from complex WSS patterns. Specifically, the Lagrangian surface transport of a species released at the vessel wall was advected in forward and backward time based on the near wall velocity field. Exposure time and residence time measures were defined to quantify accumulation of trajectories, as well as the time required to escape the near wall domain. The effect of diffusion and normal velocity was investigated. The trajectories induced by the WSS vector field were observed to form attracting and repelling coherent structures that delineated species distribution inside the boundary layer consistent with exposure and residence time measures. The results indicate that Lagrangian wall shear stress structures can provide a template for near wall transport.

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“…More recently, Surana et al [13,17,18] demonstrated an exact theory of three-dimensional flow separations, taking into account the strength of the skin-friction lines convergence. They found in particular that only four types of separation lines-shown in Figure 6-can engender a unique and well-defined separation surface in physical flow fields.…”

Section: Skin-friction Pattern For Understanding 3d Flow Separationsmentioning

confidence: 99%

Study and Control of a Radial Vaned Diffuser Stall

Marsan

Trébinjac

Coste

et al. 2012

International Journal of Rotating Machinery

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The aim of the present study is to evaluate the efficiency of a boundary layer suction technique in case of a centrifugal compressor stage in order to extend its stable operating range. First, an analysis of the flow pattern within the radial vaned diffuser is presented. It highlights the stall of the diffuser vanes when reaching a low massflow. A boundary layer separation in the hub-suction side corner grows when decreasing the massflow from the nominal operating point to the surge and finally leads to a massive stall. An aspiration strategy is investigated in order to control the stall. The suction slot is put in the vicinity of the saddle that originates the main separating skin-friction line, identified thanks to the analysis of the skin-friction pattern. Several aspiration massflow rates are tested, and two different modelings of the aspiration are evaluated. Finally, an efficient control is reached with a removal of only 0,1% of the global massflow and leads-from a steady-state calculations point of view-to an increase by 40% of the compressor operating range extent.

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An exact theory of three-dimensional fixed separation in unsteady flows

Cited by 39 publications

References 25 publications

Shock wave–boundary layer interactions in rectangular inlets: three-dimensional separation topology and critical points

Shock wave–boundary layer interactions in rectangular inlets: three-dimensional separation topology and critical points

Lagrangian wall shear stress structures and near-wall transport in high-Schmidt-number aneurysmal flows

Study and Control of a Radial Vaned Diffuser Stall

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