Experimental and numerical investigation of confined coaxial turbulent jets

The present study concentrates on the turbulent mixing of a primary jet and its surrounding fluid stream in a pipe. Detailed profiles of the axial mean and rms velocities have been measured with an LDA unit. Measured spectra of the centerline axial velocity fluctuations demonstrated the presence of coherent structures with Strouhal numbers between 0.33 and 0.51. A finite-difference numerical procedure was used for the prediction of the axisymmetric elliptic flow field. The performance of a two-equation turbulence model was tested for selected sets of previous experimental data. The dominance of numerical diffusion in the present computations has been documented. A set of numerical computations which utilize the detailed inlet profiles obtained during the present experimental work were also performed. Comparison of the numerical predictions to the present measurements were found to be satisfactory. 19 references