Merging jets in a coflowing ambient fluid - a hybrid approach

A multiple-point hybrid model for predicting the behavior of merging jets in a coflowing ambient fluid is presented. The hybrid model combines the modular structure of a length-scale model with the reduced empiricism of an Eulerian-integral model. Integral models of merging behavior are cumbersome because of the need to sum the momentum of individual jets during the merging process. A length-scale approach simplifies the model significantly, but details of the merging process are lost. A significant limitation of length-scale models is the assumption that the transition between flow regimes occurs at a single point. This difficulty can be overcome by allowing the transition to occur in stages and this leads to the use of the multiple-point approach. Predictions from the multiple-point hybrid model are compared with an equivalent single-point hybrid model and an Eulerian-integral solution for the same problem. The multiple-point approach significantly reduces transition errors when compared to the single-point model. These transition errors can result in inaccurate predictions of merging behaviour. Predictions from the multiple-point hybrid model are in good agreement with the integral solution.