Comparison of turbulence measurements with single,X and triple hot-wire probes

The accuracy of Reynolds stresses and triple velocity correlations as measured by single, X and triple hot-wire anemometry was assessed from experiments in a complex turbulent boundary layer. The yaw sensitivity of each hot-wire sensor was calibrated in an accurate way, and taken into account by the digital reduction schemes used. For time-dependent two-component measurements of velocity fluctuations, a non-iterative data reduction method was proposed, which substantially reduced the required computer time. The accuracy of the standard evaluation of the Reynolds stresses from the X- and single-sensor measurements was shown to deteriorate as the local turbulence level increased up to 25%. On the other hand, improvements of the order of several percent can be achieved by inclusion of the triple-order terms into the calculation of the second-order ones. Finally, a triple-sensor hot-wire probe with an orthogonal sensor arrangement was introduced and used for comparison measurements of the Reynolds shear stresses and of the triple-velocity correlations.