Helicopter Performance Enhancement by Improving Retreating Blade Stall Using Active Flow Control

Abstract In conventional helicopter there are many operation limits and constraints, one of them is the retreating blade stall. it is the phenomena of aggressive separation on the blade in the retreating side in the blade travel which is a result of high angle of attack combined with low relative velocity occurs in the retreating side. This phenomenon limits the helicopter forward speed, which after exceeding that limit helicopter start to roll and excessive vibration occurs and dangerous situations is happening. In this study a model is created numerically to study the effect of active flow control over helicopter blade to improve the retreating blade stall. Active flow control applied to helicopter blades determines if this technology is applicable and can improve retreating blade stall alongside overall helicopter performance. Models are built in 2D and 3D and numerically evaluated and compared with complete helicopter main rotor hub with known geometry and available performance parameters by NASA test rigs. Results shows a good impact of applying this technique on the stall in the 2D simulation which gives improving in aerodynamics which lead to overall performance enhancement represented by lift to drag ratio over the airfoil simulated in this study. A three-dimensional model with given geometry from NACA report for comparison and validation. Result in 3D model gives good matching results with available parameter for the benchmark cases and also desired enhancement reached in the controlled cases which separation delayed and aerodynamic parameters improved.