Use of dual plane PIV to assess scale-by-scale energy budgets in wall turbulence*

Dual plane particle image velocimetry (PIV) data are acquired in streamwise-spanwise planes in the logarithmic region of the turbulent boundary layer in a zero pressure gradient flow at friction Reynolds number $Re_\tau = 1160$. The dual plane technique allows determination of the full velocity gradient tensor in the measurement plane. In earlier work, data were acquired in fields of size $1.1\delta$ by $1.1\delta$ and velocities were resolved to areas of $25$ viscous wall units. This resolution was found to be adequate for identification of the energy-containing vortical structures. In current work, we repeat the experiments using smaller fields of size $0.5\delta$ by $0.5\delta$ in order to capture and investigate smaller scales. The combined data from both fields can be used to assess scale-by-scale energy budgets including the turbulent dissipation rate. The experimental results will be compared with results from a direct numerical simulation (DNS) of a fully developed channel flow at $Re_\tau = 934$.