An Analytical Model for Boundary Layer Control Via Steady Blowing and Its Application to NACA-65-410 Cascade

In this paper, boundary-layer flow-control technique via steady blowing for low-speed compressor cascade applications is investigated using an analytical model based on the integral method and computational fluid dynamics (CFD). The integral method is developed and used to investigate the effect of the momentum, the velocity magnitude, and the angle of the blowing flow on the behavior of the boundary layer. It is found that the change in the boundary layer momentum thickness across the blowing location is a linear function of the blown-flow momentum coefficient and a decaying function of the blown-flow velocity ratio. For the case when the size of the blowing slot and the velocity magnitude of the blown-flow are kept constant and the blowing mass flow rate is increased by increasing the blowing angle, there is an “optimum” blowing angle that maximizes the benefit of the boundary layer blowing. This angle increases with increasing velocity ratio and reaches an asymptotic value of 45 deg. According to the model, the change in the momentum thickness across the blowing location is conveyed exponentially downstream; thus, a small change in the momentum thickness due to flow blowing can have significant effect downstream. The developed model is applied to the NACA-65-410 low speed cascade using CFD, and good agreement between theory and CFD is obtained.