NUMERICAL STUDY ON EFFECT OF REDUCED FREQUENCY ON A VORTEX INDUCED BY AN OSCILLATING SUB BOUNDARY LAYER VORTEX GENERATOR

This paper presents a numerical study of the effects of reduced frequency on the performance of an oscillating subboundary layer vortex generator. The numerical simulations were done using Fluent 6.3 and RANS equations were used to model the flow field induced by the vortex generator on a flat plate. A hybrid mesh with SST k-ω turbulence model was used during the computations. The undisturbed boundary layer thickness at the location of vortex generator was 80 mm and a vane-type VG with height of 40 mm was used. The flow Reynolds number based on the streamwise distance is 10^6. The VG was oscillated in a simple harmonic motion between 0° to 15° over a range of reduced frequency, F^+. The increase in the spanwise averaged skin friction with the increase in reduced frequency is clearly observed. Furthermore, the time averaged skin friction distribution for oscillating SBVG is less spread compared to the static SBVG. The results also show that an increase in the reduced frequency induces secondary vortex to appear. The simulations result obtained are also found in satisfactory agreement with the experimental results.