The reduction of spatial aliasing by long hot-wire anemometer probes

Experiment and numerical analysis are presented to demonstrate that a hot-wire anemometer probe reduces spatial aliasing of turbulent velocity fluctuations because of the filtering property of the probe sensing element. The experiment focuses on the one-dimensional turbulent velocity spectrum and utilizes a long sensing length hot-wire probe to exaggerate the effect of the sensing element on the turbulent field. The numerical analysis utilizes a model of the hot-wire probe from Wyngaard (1968) along with isotropic turbulence relations to obtain an equation for the hot-wire response in a turbulent velocity field. The model can be used to determine the effect of hot-wire length on the one and three-dimensional turbulent spectra. The experimental study demonstrates that the finite length, hot-wire probe filters out energy in the high wave number region of the one-dimensional spectrum thereby verifying its ability to reduce spatial aliasing. Interestingly, the study also shows that energy in the low wave numbers of the one-dimensional spectrum is attenuated. The numerical study of the hot-wire probe demonstrates that this low wave-number attenuation is purely an artifact of the one-dimensional spectrum and not an effect of the hot-wire probe.