Turbulent wall pressure reduction using suction control

A study of the fluctuating wall pressure beneath a 2-d turbulent boundary layer was conducted in a water tunnel with Reynolds numbers, based on momentum thickness, ranging between 2,100 and 4,300. The boundary layer was perturbed with steady mild suction to assess the effect of upstream suction on the fluctuating wall pressure measured downstream of the suction slit. Wall pressure signatures were captured using a custom-fabricated piezo-ceramic array with d ⁺ values ranging between 64 and 107. Likewise, the velocity field was measured with a laser Doppler velocimeter with l ⁺ values ranging between 4.0 and 6.7 for the lowest and highest Re _θ investigated. Estimates of the wall pressure spectra revealed a noticeable hydrodynamic peak that scaled reasonably well with outer variables and with an average convective speed of 75 % of the free stream velocity (based on unconditionally sampled pressure time series). Two boundary layer suction control cases were studied corresponding to suction rates of less then 30 % of the boundary layer momentum. The findings reveal how only modest amounts of suction are needed to reduce upwards 50–60 % of the hydrodynamic ridge.