Local isotropy of the velocity and vorticity fields in a boundary layer at high Reynolds numbers

Measurements of the velocity and vorticity field with a 12-sensor hot-wire probe were carried out in the boundary layer of the test section ceiling of the NASA Ames $80×120ft2$ wind tunnel at a turbulence Reynolds number of $Rλ≈875$⁠. Tests of local isotropy were applied to the data obtained at $y/δ=0.1$⁠. In the inertial subrange, which extended over a decade of wave numbers for this experiment, both the velocity and vorticity component one-dimensional $kx$ spectra agree well with the isotropic spectra of Kim and Antonia [J. Fluid Mech. 251, 219 (1993)]. This agreement extends into the dissipation range up to wave numbers at which the accuracy of the measurements is limited because of spatial resolution and other sources of error. Additional tests of local isotropy, from the characteristics of the Reynolds shear stress correlation coefficient cospectrum and from the isotropic relationships between the $kx$ spectra of the streamwise velocity and vorticity components with the $kx$ spectra of the respective cross-stream components, also show evidence of local isotropy at these higher wave numbers.