Measurements of some features of turbulence in wall-proximity

Some quantities, like boundary layer parameters, turbulence intensity, and skewness and flatness of u and ∂u/∂t, were measured to specify the flow in which the effect of the wall proximity on hot-wire readings was studied and corrected. The relationship between skewness and flatness of ∂u/∂t established by Van Atta and Antonia (1980) is also valid in the flows investigated here. Experimental results show that the sublayer next to the wall exists in all flows (i.e., with different types of pressure gradients) and the velocity in this region is linear. This layer extends to a value of Y⁺ approximately equal to 5. Even in turbulent flow, t_w= |δŪ/ δ Y | _wis valid. The characteristics of sublayer are:Intensity of turbulence is a maximum at the edge of the sublayer (i.e., at Y⁺ = 5).The skewness of ∂u/∂t decreases in the sublayer towards the wall. Intensity of turbulence is a maximum at the edge of the sublayer (i.e., at Y⁺ = 5). The skewness of ∂u/∂t decreases in the sublayer towards the wall. The flatness of ∂u/∂t becomes very high towards the wall.