Date of Award
Doctor of Philosophy
Civil and Environmental Engineering
Dr. Gregory A. Kopp
Dr. Paul J. Sullivan
An experimental investigation has been carried out in a relatively simple turbulent flow in order to directly measure for the first time the Expected Mass Fraction (EMF) of the state of a contaminant concentration field within a contaminant cloud. Particle image velocimetry (PIV) and Planar laser induced fluorescence (PLIF) were used to measure simultaneous velocity and concentration fields, respectively. The EMF is a relatively simple measure of the state of a contaminant cloud. It has been shown that the EMF is approximately self-similar when concentrations are normalized by the centreline mean concentration. It has been shown that a reasonable approximation of the EMF moments is
possible by using the centreline absolute moments. The results are compared with the theoretical and experimental results established for a line source of scalar in grid turbulence.
The two closure approximations in the evolution of the moments of the probability density function of a scalar concentration are validated experimentally using simultaneous measurements of velocity and concentration fields. The effect of molecular diffusivity is brought into the convective closure approximation by introducing a representative ‘local concentration scale’, which appears to be a robust improvement in the approximation and can be estimated directly from the centreline moments. The concept o f fractal scaling is used in dealing with under-resolved dissipation measurements by using an extrapolation scheme. This leads to two distinct self-similar regions within the Batchelor scale and the Integral scale, separated by the Kolmogorov scale, in the measured constant of the dissipative closure approximation.
Sarathi, Partha, "EXPERIMENTAL STUDY OF THE SCALAR CONCENTRATION FIELD IN TURBULENT FLOWS" (2009). Digitized Theses. 4030.