Dennis M. Bushnell

Model of drag reduction by compliant walls

A numerical model of the effect of compliant walls on turbulent boundary layer flows, has been investigated. The model is based on Burton’s1 observation that turbulent bursts produce large pressure fluctuations that tend to produce low speed ’’streaks’’ near the wall. These streaks undergo space‐time retardation and a new burst appears when the velocity profile becomes highly inflectional. The idea of the model is that the compliant wall motion interrupts this feedback loop of burst formation and that short wavelength wall motions can possibly delay burst formation long enough for the favorable gradient part of the pressure pulse caused by previous bursts to effect a decrease in the burst frequency. The numerical model involves solution of the two‐dimensional time‐dependent Navier–Stokes equations in a rectangular geometry. A typical calculation is performed using 257 grid points in the downstream direction with inflow‐outflow boundary conditions applied. In the boundary layer direction 33 Chebyshev polyn...