Passive fluidic control on aero-optics of transonic flow over turrets with rough walls.

In the transonic flow over a hemisphere-on-cylinder turret, strong aero-optical effects can be caused by local shock/boundary-layer interactions and separation shear layers at the turret's zenith. The effects of an annular rough wall on the passive control of fluid and aero-optics are investigated by experimental measurements and numerical simulations. The local shock/boundary-layer interaction and separated shear layer at the zenith of the turret are recorded using shadowing and Mach–Zehnder interferometer measurements. The aero-optics are measured using a Shack–Hartmann wavefront sensor. The experimental results show that the annular rough wall on the turret weakens the local shock wave, moves the flow separation point forward, and reduces the wavefront distortion at the zenith. The rough wall functions for the shear stress transport (SST) k-ω turbulence model proposed by B. Aupoix ["Roughness corrections for the k–ω shear stress transport model: Status and proposals," J. Fluids Eng. 137, 021202 (2014)] and C.-H. Lee ["Rough boundary treatment method for the shear-stress transport k–ω model," Eng. Appl. Comput. Fluid 12, 261–269 (2018)] are used to further study the control effect of different roughnesses. Numerical simulations based on both rough wall functions show good agreement with the experimental measurements. For various transonic flows, the steady wavefront distortions at the zenith with the rough wall at roughness k s = 1 mm are 21%–50% smaller than those with smooth walls. The smaller the supersonic region, the more effective the rough wall is in reducing wavefront distortion. [ABSTRACT FROM AUTHOR]