Experimental Investigation of Surface-Pressure Fluctuations over a Venus Probe During Descent

A wind-tunnel test campaign was conducted to estimate the surface-pressure fluctuations on NASA’s Zephyr probe during its descent into the Venusian atmosphere. A 2%-scale model of the Zephyr probe was manufactured, instrumented with 18 microphones, and tested in two wind tunnels located in the Fluid Mechanics Laboratory of NASA Ames Research Center at velocities ranging from 13 to 48 m/s. Microphones were located to provide spectra of pressure fluctuations in regions with different flow characteristics, as well as for calculating various two-point statistics. Besides fluctuating surface-pressure measurements, hot-film velocity measurements as well as smoke–laser flow visualization were conducted to better understand the flow around the probe. The flow visualization showed three primary flow regimes: an attached turbulent boundary layer on the front; a region of separated flow upstream of the flared lip; and a large, separated wake at the rear. The acoustic spectra generally showed three different shapes corresponding to these flow regions, with the highest levels at the rear of the model and directly in front of the drag plate. The autospectra and cross spectra were used to determine Corcos model parameters and were passed on for vibroacoustic analysis of the probe and the science instruments inside.