Predictive Modelling of Engine Inlet Distortion in Crosswind Conditions

飞机发动机进气口的构造是为了在广泛的运行条件下提供稳定和均匀的气流。机舱旨在优化巡航效率，同时在非设计条件下满足严格的操作要求。最关键的操作点之一发生在地面上，当飞机静止时，会有强烈的侧风。在此设置中，侧风导致外机舱出现停滞点，然后气流加速并绕过机翼，然后以接近音速的速度进入发动机。发动机入口处的负压力梯度导致流动分离，这会扭曲来流；当扭曲程度足够大时，风扇叶片可能会出现失速或气动不稳定。发动机进气变形的准确预测是极其困难的，因为它涉及层流到湍流的转变、复杂的几何形状和压力梯度以及流动分离。该项目旨在改进现有的过渡模型，以准确地确定复杂三维吊舱的过渡开始，从而提高这些临界变工况下来流变形的预测精度。

The intake of aircraft engines is constructed to provide a steady and uniform flow over a wide range ofoperating conditions. Nacelles are designed to optimize cruise efficiency while meeting the stringentoperational requirements at off-design conditions. One of the most critical operating points occurs on theground with severe crosswinds when the aircraft is at rest. In this setup, the crosswind causes a stagnation pointto occur on the outer nacelle, the flow then accelerates and transitions around the lip before entering the engineat a near-sonic speed. The negative pressure gradient at the engine inlet results in flow separation, whichdistorts the incoming flow stream; at sufficiently large distortion levels, stall or aerodynamic instabilities of thefan blades may arise. The accurate prediction of the engine inflow distortion is extremely difficult as it involveslaminar-to-turbulent transition, complex geometry and pressure gradients and flow separation. This projectseeks to improve on existing transitional models to accurately determine the onset of transition on a complexthree-dimensional nacelle, and thus improve the prediction accuracy of inflow distortion at these criticaloff-design conditions.