In this paper we explore a new hybrid method for the near wall treatment of viscous computation with block structured Cartesian mesh. Cloud of points are generated to resolve the near wall boundary layer and most of the points are distributed on one-dimensional lines along the wall normal directions, thus enabling the usage of high order scheme for the wall-normal flow derivative. In streamwise direction the flow derivative is approximated using second order least-square meshless method. Compared to the existing wall treatment methods for block structured Cartesian mesh, the current approach retains the flexibility of the least-square method and also offers the opportunity of high order accuracy along the wall-normal direction. A simple method is proposed to generate the near-wall points and it relieves the burden of body-fitted near-wall mesh generation. The current approach is tested with several high Reynolds number flows and the results are discussed.
Transfer matrix (TM) models are developed in this paper for varies types of synthetic jet (or zero-net mass-flux) actuators used in active flow control applications. The analysis and design of a synthetic-jet actuator is greatly simplified by the use of the transfer matrix method, which treats the synthetic-jet actuator as a two-port network with input and output ports. The TM method is a powerful alternative to lumped-element modeling. The models are summarized, and the resulting predictions match favorably with previously published results.
Unsteady vortex structure in the wake behind bluff body was experimentally investigated by wind tunnel experiment. A flexible rectangular plate, which was made of a soft polyurethane block, shows the sway motion and flow-induced vibration caused by fluid force. Phase-averaged vortex structures behind the flexible plate were educed by Particle Image Velocimetry (PIV) using light sensors. The size of recirculation region and upwash flow in the wake were influenced by unsteady motion of the plate vibration.
We investigated a supersonic flowfield with transverse injection of air or helium by stereoscopic particle image velocimetry and calculated single-time two-point spatial correlations of velocity fluctuations. For both injection gases, the bow shock wave formed by the injection and its reflection from the upper wall could be seen in the mean velocity distribution. In the velocity fluctuation intensity distribution, we observed vibrating counter-rotating vortex pair and the Reynolds stress was formed along the track of the maximum mean velocity gradient. Correlations showed the scale structure of turbulence and the shapes of the correlation region changed with the selected velocity component. Differences were observed between the results obtained for the two injectant species.
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