A TRACER-PARTICLE FLUID VELOCITY METER INCORPORATING A LASER

This paper describes a new type of laser fluid velocity meter. The device measures the time taken for a particle in a fluid flow to travel between two laser beams, enabling the particle velocity to be directly calculated. The device is simple and does not require the insertion of a probe into the flow. Experimental velocity measurements have been made, up to a velocity of approximately 200 m s-1, by using the naturally occurring dust particles in a wind tunnel flow. The results obtained with the laser velocity meter are in satisfactory agreement with those deduced from pressure measurements. The maximum velocities measured in the tests were limited by the capabilities of the wind tunnels used. It may be possible to measure higher velocities with the device but the accuracy of such measurements will depend on the fidelity with which particle velocities represent flow velocities under conditions of high acceleration.