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Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Streamwise Vortex ♦ Vortex Generator ♦ Apg Separation Control ♦ Downstream Development ♦ Wall Shear-stress ♦ Maximum Vorticity Max ♦ Vortex Center ♦ Wall-normal Velocity Vmax ♦ Separation Control ♦ Strong 3-dimensionality ♦ Instantaneous Wall-normal Position ♦ Turbulent Statistic ♦ Vortex Dynamic ♦ Downstream Direction ♦ Wall Pulsed-wires ♦ Particle Image Velocimetry ♦ Large Component ♦ Reynolds Shear Stress ♦ Instantaneous Behaviour ♦ Fixed Vortex Generator ♦ Vg-heights Downstream ♦ Maximum Spanwise Velocity Wmax ♦ Physical Mechanism ♦ Separating Turbulent Boundary Layer ♦ Vortical Structure ♦ Present Study ♦ Streamwise Velocity Distribution ♦ Instantaneous Spanwise Position ♦ Velocity Profile ♦ Velocity Field ♦ Closed Reverse-flow Region ♦ Large Negative Peak ♦ Vg Height ♦ High Momentum
Abstract The goal of the present study is to investigate the vortex dynamics and the physical mechanisms involved in the process of separation control by means of fixed vortex generators (VG) in a separating turbulent boundary layer with a closed reverse-flow region. The wall shear-stress in spanwise and downstream directions was measured using wall pulsed-wires. The 3-dimensionality in the wall shear-stress introduced by the VGs is persistent to approximately 30 VG-heights downstream of the VGs. The downstream development in terms of turbulent statistics and the instantaneous behaviour of the streamwise vortices were investigated in both the cross-stream (yz-) and the wall-normal (xy-) plane using Particle Image Velocimetry (PIV). It is shown that VGs reorganise the velocity field. High momentum is brought down to the wall in the wake of a VG. This can be seen in the streamwise velocity distribution (U) which is fuller, the wall normal (V) component has a large component towards the wall (Figure 1) and the Reynolds shear stress has a large negative peak, preventing separation. The instantaneous spanwise position, zp of the vortex center is fluctuating within a distance of about one VG height (h) whereas the instantaneous wall-normal position, yp is fluctuating within h/2 due to the damping of the wall (Figure 2). The downstream development of the vortical structure in terms of maximum vorticity ωx max, maximum spanwise velocity Wmax and wall-normal velocity Vmax shows that the strong 3-dimensionality is decreased. Figure 1: Velocity profiles at the centerline of a vortex generator at x/h = 5.
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study