Jets in crossflow mixing analysis using computational fluid dynamics and mathematical optimization

Computational fluid dynamics and mathematical optimization were used to investigate the mixing effectiveness of jets in crossflow. A numerical model was developed, validated, and calibrated against experimental measurements of a temperature distribution at different cross-sectional planes downstream of an orifice injection plane. Good agreement was obtained when the ratio between momentum and species diffusivities was varied according to the jetto-mainstream momentum flux ratio. Numerical optimization of various double-sided jet configurations followed, using a parametric approach. The results obtained showed that changes in orifice size and spacing at a constant orifice-to-mainstream area ratio and momentum flux ratio have a significant influence on mixing effectiveness. The optimum configuration compared favorably with an empirically defined relationship between orifice spacing and momentum flux ratio. Mathematical optimization was then combined with numerical methods to predict the optimum orifice configuration. The results showed the feasibility of using a gradient-based approximation method to allow, for a given set of parameters, the systematic adjustment of design variables to achieve improvement in performance.