optimisation of trapped vortex cavity for airfoil separation control

The effects of a trapped vortex cavity (tvc) on the aerodynamic performance of a naca 0024 airfoil at a constant angle of attack (aoa) of 14◦ were investigated in this study. it was observed that mass suction (mfr) was required to stabilise the vortex within the cavity segment. lift to drag ratio (l/d) and mfr were chosen as performance objectives, along with a fully attached flow constraint (flow separation at x/c ≥ 95% ). parametric analysis was carried on the baseline airfoil with and without suction and compared to the airfoil with tvc with and without suction. it was observed that l/d increases as mfr increases for a baseline airfoil, and flow separation is delayed at high suction values (mfr = 0.2 kg/s). the tvc modifies the pressure distribution on the baseline airfoil when mfr is applied to the cavity section and there is a significant increase in lift; thus, l/d increases and flow separation is delayed. a lower value of mfr = 0.08 kg/s is sufficient to stabilise the vortex and improve the efficiency of the tvc airfoil. the findings of these parametric studies were used to do a multiobjective optimisation using a genetic algorithm to attain the desired cavity shape while achieving the largest l/d and the lowest mfr (that is proportional to the power required for control) with a fully attached flow constraint. it was found that mass suction and cavity shape both had an equal influence on flow control. the pareto optimal front yielded a series of optimum designs. one of them was subjected to an off-design analysis in order to validate its performance at other incidences. it was observed that it performs better than the baseline airfoil, with an improved l/d and an increase in stall angle from 10◦ to 14◦.