Numerical Study of Perpendicularly Injected Jet for Fluidic Thrust Vectoring Applications

Perpendicular (normal) injection has been proposed as an alternative actuation method for fluidic thrust vectoring (FTV), with the potential to reduce required actuation mass flow compared to tangential Coanda blowing. This paper investigates the feasibility and aerodynamic limitations of normal blowing in a convergent Coanda-coflow nozzle representative of a midsize mixed turbofan for unmanned aerial systems operating at maximum flight Mach numbers of 0.9. Two nozzle configurations, a slender, elongated geometry and a compact, blunt geometry, are analyzed using Reynolds-averaged Navier–Stokes simulations supported by a design-of-experiments approach and surrogate-based optimization. The results show that normal blowing can generate thrust vector angles comparable to tangential blowing at low actuation levels. However, perpendicular injection induces strong blockage of the upper primary channel, leading to reduced discharge coefficients, increased total-pressure losses, and limited vectoring efficiency. These effects are most pronounced for the blunt geometry, which exhibits early flow separation and poor robustness. The slender geometry delays blockage onset and consistently achieves superior performance. Overall, normal blowing is feasible but strongly geometry dependent and generally less efficient than tangential blowing for the configurations considered. The results highlight the importance of geometry–actuation interaction in FTV nozzle design.