Numerical investigation of helicopter hover state of flight enhancement by applying active flow control over helicopter special tip airfoil

Abstract

In conventional helicopter there are many operation limits and constraints, one of them is the maximum take-off weight and ability of main rotor to produce thrust during the hover mode of flight. In this study a numerical investigation is performed to show the effect of active flow control technique over the helicopter tip blade in hover mode to enhance the main rotor ability to produce lift by improving total performance of used airfoil. Active flow control applied to upper airfoil surface of blade tip close to the leading edge to control the boundary layer by adding momentum using small oscillating jet. The advantage of this technique comes from the small energy required to enrich the boundary layer which we use very small jet for excitation. Model is formed in 2D and is numerically investigated for airfoil used in main rotor blade tip with known geometry and performance parameter for clean rotor given by NASA test stand. Results shows very good impact on the hover mode in 2D model which gives enhancement in the overall performance represented by lift to drag ratio in the used tip airfoil in different case study used depending on the study plan that considered various excitation parameter. More than 60% increase in total performance represented by lift to drag ratio is obtained using suitable parameter and excitation point.