EFFECT OF CONCENTRATED WALL SUCTION ON A TURBULENT BOUNDARY LAYER

The effect of suction, applied through a short porous wall strip, on a low Reynolds number self‐preserving turbulent boundary layer has been quantified by measuring the local wall shear stress and the main Reynolds stresses downstream of the strip. When the suction rate is sufficiently high, pseudo‐relaminarization occurs almost immediately downstream of the strip. Farther downstream, transition occurs followed by a slow return to a fully turbulent self‐preserving state. During relaminarization, the measured skin friction coefficient cf falls below the level corresponding to the no suction value, reaching a minimum where transition begins. An empirical cf distribution is proposed that groups together results obtained at different streamwise stations and different suction rates. Of all the measured Reynolds stresses, the longitudinal turbulence intensity recovers relatively quickly from the change in boundary conditions while the wall‐normal turbulence intensity and the Reynolds shear stress are significan...