A remote sensing technique, free from many of the problems associated with Inserting probes into a liquid flow, has been developed to measure turbulent density fluctuations In a low speed, submerged water jet. The technique employs two schlieren optical systems, composed of He-Ne lasers and photo detectors. The optical beams intersect in the flow in a plane perpendicular to the flow direction. Knife edges are aligned such that the systems are sensitive to gradients of refractive index in the flow direction. An analysis is presented which relates the cross-covariance of the two signals to the local two-point refractive-index covariance and thence to the two-point density covariance within the jet. The limitations and assumptions involved in the analysis are discussed in detail.

Measurements of density fluctuation profiles in a 1.2 m/sec. vertical water jet are presented and compared with available hot film data. The turbulent convection speed has also been measured by separating the beams in the flow direction. The effects of the presence of air bubbles in the jet are discussed.

Meeting Name

Symposium on Turbulence Measurements in Liquids (1969: Sep., Rolla, MO)


Chemical and Biochemical Engineering

Document Type

Article - Conference proceedings

Presentation Type

Contributed Paper


Light Transmission Techniques

Document Version

Final Version

File Type





© 1972 University of Missouri--Rolla, All rights reserved.