Planar Velocity Measurements in an Incompressible and a Weakly Compressible Mixing Layer

For the weakly compressible mixing layer, the velocity ratio was 0.53, the density ratio was 0.67, and the convective Mach number was 0.38. At the location where the PIV images were obtained, Rex = 3.7 x 106 , Redw = 1.8 x 105, and Rx/lambda = 18. The planar velocity fields obtained in this study fall into three regimes characterized by the size and number of large-scale structures present. The large-scale rollers are either circular or elliptical, with the elliptical rollers having, in general, horizontal major axes. The transverse velocity fluctuations and Reynolds shear stress are suppressed for the weakly compressible mixing layer as compared to the incompressible case. The spatial correlations of velocity fluctuations are also smaller than those for the incompressible case. The linear stochastic estimate of a roller structure in the weakly compressible mixing layer is elliptical with the major axis oriented in the streamwise direction and with an eccentricity greater than for the incompressible case. The linear stochastic estimate of a braid suggests that the braids are vertically oriented, as opposed to the oblique orientation seen in the incompressible mixing layer. In addition, the braids in the weakly compressible case have a vertically oriented stagnation line, as opposed to the braids in the incompressible mixing layer where stagnation occurs at a point.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Olsen, Michael Gary

Contributors dc:contributor

• Dutton, J. Craig

• Applied Mechanics

Language dc:language

eng

Identifier

(MiAaPQ)AAI9921720

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/83982