Y. Dubief et al., THE MEASUREMENT OF PARTIAL-DERIVATIVE-U PARTIAL-DERIVATIVE-Y IN A TURBULENT BOUNDARY-LAYER OVER A RIBLET SURFACE/, International journal of heat and fluid flow, 18(2), 1997, pp. 183-187
Statistics of partial derivative u/partial derivative y have been meas
ured in a turbulent boundary layer over either a smooth wall or a ribl
et surface using parallel hot wires. Over the riblets, the mean square
value of partial derivative u/partial derivative y (normalised with s
mooth wall variables) is smaller than over the smooth wall; the differ
ence increases as the distance to the wall decreases. Also this differ
ence is larger when the riblets operate in a drag-augmenting mode, The
se changes would reflect changes in the near-wall turbulence structure
. Furthermore, on the basis that partial derivative u/partial derivati
ve y is a major contributor to the spanwise vorticity, the results ind
icate that, relative to the smooth wall, the mean square spanwise vort
icity is reduced near a riblet surface. (C) 1997 Elsevier Science Inc.