A fast-response aspirating probe for measurements of total temperature and pressure in transonic cryogenic wind tunnel

A newly developed, 3-mm-diam, dual hot-wire aspirating probe was used to measure the time-resolved stagnation temperature and pressure in a transonic cryogenic wind tunnel. The probe consists of two coplanar constant temperature hot wires at different overheat ratios operating in a 1.5-mm-diam channel with a choked exit. Thus, the constant Mach number flow by the wires is influenced only by free-stream stagnation temperature and pressure. Diffusion of the free-stream Mach number to a lower value in the channel reduces the dynamic drag on the hot-wire. Frequency response of the present design is dc to 20 kHz. The probe was used to measure the unsteady wake shed from an oscillating airfoil tested in the 0.3-m Transonic Cryogenic Tunnel at NASA-Langley Research Center. The hot-wire lasted for more than ten hours before breaking, proving the ruggedness of the probe and the usefulness of the technique in a high dynamic pressure, transonic cryogenic wind tunnel. Typical data obtained from the experiment are presented after reduction to stagnation pressure and temperature.