01. Experimental/Computational Fluid Dynamics

A hot-wire rake is a device consisting of an array of hot-wire sensors in the spanwise direction and is used to investigate flow structures such as wake, wall turbulence, and disturbances in transition boundary layers. When operating a hot-wire rake with the constant temperature mode (CTA), which has a high-frequency response, each sensor should be electrically isolated. On the other hand, if the same rake is operated with constant current mode (CCA), the spatial resolution in the spanwise direction is twice that of CTA if prongs are aligned at the same interval. However, it is known that in CCA, the frequency response of the output signal is only a few tenths of that of the CTA. If the frequency response of the recorded CCA output signal can be compensated by the transfer function of CCA circuit, we may obtain flow fields with high spatio-temporal resolution. In this study, we focused on how accurately the frequency response of CCA can be corrected for the frequency response of CTA. Simultaneous measurements of CTA and CCA were performed in the wake of a circular cylinder. The results showed that amplitude and phase were accurately compensated up to 5 kHz, that is, the output waveform of the CCA matched almost perfectly with that of the CTA.