Abstract

The scaling of NSTAP probe data from the Princeton superpipe is examined and compared to both K41 and K62 theories for the inertial subrange. The comparisons are made at the pipe centre-line and in the logarithmic region, where in both cases, the transport equation for the turbulence kinetic energy is really quite simple. Nonetheless, single hot-wire data (resolved to less than three Kolmogorov lengthscales) for the streamwise velocity fluctuations show very little agreement with Kolmogorov’s theories at lambda-based Reynolds numbers of several hundred. Reasons for this are put forward and used to introduce a novel experiment in which free-stream turbulence, initially passing over a moving ground plane to produce a shearless boundary layer, is rapidly sheared on passing to a stationary surface. Such an arrangement is well suited to examining “top-down” and “bottom-up” transport mechanisms in a systematic manner. Here we focus on the linear (fast) and nonlinear (slow) contributions to static pressure fluctuations, both in-stream and at the wall.