Oscillating vane for measuring speed of gas flow.

Experiments with an oscillatory vane in a wind tunnel reveal that the vane’s oscillation frequency is directly proportional to the square root of the dynamic pressure of the flow. The linear relationship is observed for flow speeds up to the speed of sound in air, argon, and helium. The vane’s oscillations are a measure of mass flow, or if used on an aircraft, of indicated air speed. In constant density media the oscillation frequency is directly proportional to flow speed, and a simple count of the oscillations is a measure of distance traveled. At given ambient temperature and pressure, the vane’s frequency is the same at the speed of sound for all gases, irrespective of their molecular weight. [ABSTRACT FROM AUTHOR]