The effect of different X-wire calibration schemes on some turbulence statistics

The effective-angle and look-up-table calibrations are used to reduce X-wire datasets in two flows: decaying grid turbulence at R(lambda)similar or equal to50 and the far field of a circular jet at R(lambda)similar or equal to400 with a mean streamwise velocity of nearly 6 ms(-1) in each case. A static check, which involves mean values of the velocity components, indicates that the effective-angle calibration incorrectly reduces the range of the estimated velocity components and is therefore likely to be less reliable than the look-up-table approach. The two methods produce significantly different results for both small- and large-scale statistics of the streamwise and, more especially, transverse velocity fluctuations. For grid turbulence, the mean-squared temporal derivatives of the streamwise and transverse velocities are larger by 3% and 19%, respectively, when estimated with the look-up-table method compared to the effective-angle calibration. The increase in the mean-squared transverse velocity derivative yields results in closer agreement with isotropy. At velocities below 6 ms(-1), the effective-angle is a quantity that strongly depends on the velocity magnitude and direction.