Aerodynamic disturbances of hot-wire probes and directional sensitivity

Directional responses of hot-wire probes are studied experimentally, and a theory is developed which attributes pitch response to aerodynamic disturbances caused by the probe and yaw response to a combination of aerodynamic disturbances and heat transfer effects. The predicted cooling velocity has the same form as Jorgensen's equation, and the pitch coefficient, predicted in terms of the probe geometry, compares favorably with experiments using ideal probes. Comparisons with real probes indicate the limits of validity imposed by hot-wire probe tolerances. The accuracy of Jorgensen's equation for combined yaw and pitch has been measured experimentally.