Turbulence in the core of a transpired channel

Flow in a fully transpired channel is examined using Particle-Image Velocimetry(PIV) to investigate the effect of stream-wise injection length scales on the core flow mean and turbulence properties. Instantaneous velocity fields are captured in a stream-wise - wallnormal plane at four different stream-wise locations (x/h=7,15,25,35) and four different porous surfaces: 3.175-mm, 4.7625-mm, 6.35-mm, 9.525-mm honeycombs. The 3.175-mm and 4.7625-mm honeycombs create smaller fluctuations in the wall-normal injection velocity and result in lower core turbulence. As a result, their mean flow profiles follow the inviscid Culick solution for a considerable distance downstream. The 6.35-mm and 9.525-mm honeycombs create higher wall-normal perturbations which get strongly amplified by the mean strain field resulting in a higher turbulence intensity downstream. As a result, their mean flow profiles deviate significantly from the Culick solution. It is found that the turbulence is profoundly affected by the mean details of the wall boundary conditions. In addition, for the first time, a database of turbulence statistics along with the complete boundary conditions (including the wall dynamic impedance) is provided to completely characterize the flow in a fully transpired channel.