Two opposing plane turbulent jet flows along a planar surface interact severely in the collision zone above the stagnation point and thereafter form a plane fountainlike merged jet perpendicular to the surface. Direct numerical simulations have been performed to explore the physics of the turbulence field in the collision zone and in the fountain jet formed as a merger of the two originally countercurrent jet streams. It is observed that the turbulence level is exceptionally high in the collision zone, i.e., just above the high-pressure stagnation region. This is ascribed to excess mean shear production arising from the streamline curvature of the bending jets. The turbulence is therefore far from equilibrium and the kinetic energy production exceeds its dissipation rate by a factor of 3. Mean-velocity profiles and second-order moments in the fountain jet compare well with measured data in similar flows. The growth rate of the fountain jet is about 0.15, which is 50% higher than the spreading rate of a conventional plane jet. Several physical aspects of this flow are hard to accommodate in Reynolds-averaged Navier-Stokes-based turbulence models. To facilitate the strive towards better turbulence closures, data fields for all terms in the kinetic energy budget are provided in this paper.
SUMMARYReduced basis simulations are used in order to generate turbulent inlet boundary conditions for a direct numerical simulation of two opposing wall jets. The two entering jets are fully turbulent channel ows of Reynolds number 180, based on friction velocity and half channel height. The in ow turbulence is generated by solving dynamical equations for the large scales only, while less energetic small scales are added randomly. The proper orthogonal decomposition method is used to identify the large scale modes used in the basis set. Mean velocity and turbulence statistics have been reported in various planes of the interaction region and the outwash jet. The increase in maximum turbulence energy from the inlet jet to the stagnation region is about 500%. The spreading rate of the merged jet was found to be 0.125.
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