Stagnation Line and Upwash Formation of Two Impinging Jets

When two jets in reasonable proximity exhaust into ambient surroundings and impinge on a ground plane, radial wall jets are formed which interact and form a stagnation region. The flow then is deflected upward to form an "upwash" sheet. These individual upwash flows are the heart of the complicated effects experienced by VTOL aircraft when they operate in ground proximity. It is the intent of this study to develop relatively simple flow models and prediction techniques, based primarily on momentum principles and empirical observations, for the estimation of two-jet ground impingement phenomena. Comparisons with experimental data indicate that these simple computational techniques can yield very reasonable estimates of certain overall aspects of the two-jet impingement problem.