Wang, Huhu (2015-12). Experimental Study of the Turbulent Mixing of Two Parallel Jets for Benchmarking Numerical Models. Doctoral Dissertation.
Turbulent mixing of parallel jet flows has broad engineering applications. For example, in Gen IV conceptual nuclear reactors, high-temperature flows mix in the lower plenum before entering the secondary cooling system. The mixing condition needs to be accurately estimated and fully understood. In addition, massive computational works involved in the design process necessitate high-fidelity experimental data sets for benchmarking simulation results.
The purpose of this study is to use laser Doppler anemometry (LDA) and particle image velocimetry (PIV), both non-intrusive measuring techniques, to evaluate the mixing characteristics of two submerged parallel jets issuing from two rectangular channels. Flow characteristics including distributions of mean velocities, turbulence intensities, and Reynolds stresses were studied for the cases with equal and non-equal discharge velocities. The locations of the merging point (MP) and combining point (CP) were found. Spectral analyses including fast Fourier transform, power spectral density estimation and continuous wavelet transform of a segment of the LDA results revealed the scale and the evolution in time of varied-size eddies in the mixing region of the flow. At last, the results obtained from LDV and PIV with two different magnification factors were compared, and the discrepancies were quantified.
The experimental data obtained from the LDA and PIV measurements of the averaged quantities and transient are not only valid for benchmarking steady-state numerical simulations using turbulence models to solve RANS equations but they also enlarge the database of the experimental data for twin jets.