A turbulent drag-reduction method employing synthetic jet sheets in a channel flow is investigated by direct numerical simulations. The are wall-parallel and produced periodic blowing suction from pairs of thin slots aligned with the main streamwise flow. By varying slot height jet-sheet angle respect to spanwise direction, margins between $10\,\%$ $30\,\%$ obtained for angles $45 ^{\circ }$ $7...

h = 9000. The discretisation is performed using a spanwise periodic spectral/hp element method. The inlet flow has turbulent velocity and pressure fields that are formed by a regenerating channel segment upstream of the inlet. Time and spanwise averages show secondary and tertiary corner eddies in addition to the primary recirculation bubble, while streamlines show a small eddy forming at the d...

Unsteady flow past a circular cylinder at a Reynolds number of 300 has been simulated. The spanwise extent of the computational domain has been systematically varied from zero (2-D) to a large value of 12&, where 4 is the spanwise wavelength of the fundamental mode-B 3-D instability (Williamson, 1996). Simulations with intermediate spanwise extent of 4 and U, have also been performed so as to i...

The QSQH theory is extended to all three velocity components taking into account the fluctuations of direction large-scale component wall friction. This effect found be significant. It explains large sensitivity longitudinal and spanwise velocities variations in Reynolds number comparison with mean velocity, stress, wall-normal fluctuations. analysis shows that variation dominated by amplitude ...

Using direct numerical simulations of turbulent channel flow, we present a new method for skin friction reduction by prevention of streamwise vortex formation near the wall. Based on recent evidence of streak instability-induced vortex generation, we develop a new technique for drag reduction, enabling large-scale flow forcing without requiring instantaneous flow information. As proof-of-princi...

Görtler vortex-induced hypersonic boundary layer transition controlled by grooves is investigated using direct numerical simulations and spatial bi-global stability analysis. In the simulations, vortices are excited wall steady blowing suction with spanwise wavelengths of 3 mm. It found that when covered grooves, streaks keep more regular even at end model. addition, skin friction coefficient r...

This paper presents an efficient Euler method on Cartesian grids coupled with an integral Boundary-Layer method. The unsteady Euler equations are solved using cell-centered finite volume method by the implicit-explicit dual-time stepping scheme. The wall boundary conditions on the wing are implemented on the wing chord plane by first order approximation so that non-moving Cartesian grids can be...

In this study, we investigated the effect of anticyclonic spanwise rotation on plane Couette flow at small Reynolds number Rew = 1300, defined by moving wall velocity, channel half-width, and kinematic viscosity direct numerical simulations using spectral method. We confirmed that typical number, mean velocity distribution became S-shape, a negative gradient appeared in centre. At significant d...

In this study, the effect of limited spatial resolution of hot wire anemometry (HWA) is investigated through analysis of the two dimensional energy spectra from direct numerical simulation (DNS) of turbulent channel flow at Reτ ≈ 934. Various spanwise filter lengths are applied to the streamwise velocity component in order to mimic the spatial resolution of the HWA experiments. The overall effe...

The two-dimensional low-speed structure of a turbulent boundary layer has been clearly visualized by a combination of a shear stress sensor using micro electro mechanical systems and the discrete wavelet transform. The application of two-dimensional discrete wavelet transforms to the visualization of wall shear stress data obtained using the micro shear stress imaging chip is described. The exp...