Laser-Doppler Measurements in a Subsonic Jet Injected Into a Subsonic Cross Flow

Abstract

The flow field of a small nitrogen jet (5 mm diameter) injected into a cross flow of air at a momentum-flux ratio of 16 was explored in the plane of the trajectory by means of a laser-Doppler technique. Several traverses were made at right angles to the jet center line obtained from schlieren photographs of light and heavy gases. Velocities were measured in the direction of the traverse and at right angles to it. The locus of the maximum velocity in the direction of the jet trajectory is close to the photographic center line. The vortex center line was derived from the measurements by iteration, and results are in good agreement with those obtained by other investigators with different techniques on a much larger scale. The excess of the center line velocity over the parallel cross stream component decreases faster than for a jet without cross flow, and jet width increases linearly with distance from an effective origin about one jet diameter upstream of the injection point if distances are measured along the trajectory. Velocity profiles exhibit the same similarity as jets injected into stagnant gas.