Momentum Flux in Plane, Parallel Jets

The evolution of the streamwise momentum flux for two turbulent, plane, parallel jets discharging through slots in a direction normal to a wall was studied both numerically and experimentally. The numerical results, obtained by solving the Reynolds-averaged Navier-Stokes equations employing a standard $k−ε$ turbulence model, predicted to within experimental error measured integrals of the momentum flux downstream of the merge point for jet spacing $S/d=5.$ Integration of the streamwise component of the Reynolds-averaged Navier-Stokes equations over a control volume results in an integral constant that was evaluated numerically for jet spacings $S/d=3,$ 5, 7, 9, and 11, and for different levels of turbulence kinetic energy and dissipation rate at the jet inlet boundaries. Results revealed that the integral constant is decreased as the jet spacing increases, and is also decreased as jet entrainment rates are increased due to higher levels of inlet turbulence kinetic energy, or alternatively, decreased levels of dissipation rate. Streamwise distance to the merge point was also found to decrease for increased levels of turbulence kinetic energy or decreased levels of dissipation rate at the jet inlet.