Ground Vortex Formation with Twin Impinging Jets 962257

Laser Doppler measurements and flow visualization are presented for a three-dimensional fountain flow generated by the impingement of two-axisymmetric turbulent jets on a ground plane through the influence of a low-velocity crossflow. The experiments were performed for a Reynolds number based on the jet-exit conditions of 1.05x10⁵, a free stream to jet velocity ratio, of 0.033, and a jet height to jet diameter ratio, H/D, of 5, and include mean and turbulent velocity characteristics along the two normal directions contained in planes parallel to the nozzle axis. The results, which have relevance to flows encountered by powered-lift aircraft operating in ground effect, show the presence of a complex 3-D scarf vortex formed around the impinging jets. In zones were measurement data are not available, the flow details are numerically visualized using a solution of the finite difference form of the three-dimensional Reynolds-averaged Navier-Stokes equations, incorporating the turbulence viscosity concept.