Large Eddy Simulation Investigating Control of Flow Over a Flat-Window Cylindrical Turret

Abstract

This work presents multiple high-order implicit large eddy simulations (ILES) investigating control of ow over a cylindrical turret with a at window oriented at 100 measured from the upstream x axis. In a previous study by the current authors, the uncontrolled ow over the turret was investigated and compared to experimental results for multiple look angles (90, 100, and 120). Additionally, a simulation using pins upstream of the aperture for passive ow control was performed for the case of 100. The current research completes that study and extends the research by investigating three additional approaches to control the ow to reduce aero-optical aberrations. The three approaches include taller pins, steady blowing round jets, and leading edge suction. The ILES computations were obtained using a well-validated high-order Navier-Stokes ow solver employing a 6-order compact spatial discretization in conjunction with a 8-order low-pass spatial lter. Simulations were executed on a massively parallel computing platform using a high-order overset grid methodology on meshes with 28 55 million nodes. Results show that taller pins work almost as well as short pins but lose some e ectiveness because the streamwise vortices from the top of the pins no longer interact with the at window leading edge recirculation region. The second approach using steady blowing round jets into the cross ow was also found to be an e ective in reducing the size of the leading edge separation bubble. Finally, steady suction through a small slot at the leading edge of the at window aperture proved better than the other approaches by successfully reducing the size of the separation bubble by 88%. This eliminated a majority of the small scale ow structures and signi cantly decreased the turbulent kinetic energy levels over the aperture. Preliminary simulations demonstrate that leading edge suction is also e ective in eliminating massive separation at a larger look angle of 120.