Numerical Investigations of Unsteady Aerodynamics and Aeroelastic Stability of Engine Nacelles.

Abstract

The nacelles of modern aeroengines are constantly increasing in size.Thus, engine airloads are becoming more powerful and their importancefor aeroelastic stability is becoming more significant. The principlegoal of this study is to answer the question of how unsteady airloadsvary while shifting to transonic Mach numbers. The investigations arecarried out by applying a Finite Volume Euler method to a harmonically oscillating annular wing. The results show that transonic effects in the case of an annular wing are essentially weaker than in the case of an airfoil. The order of magnitude of the variations is about 10%. Possible consequences for aeroelastic stability are investigated with the example of an elastically mounted annular wing in transonic flow. The shifts of the stability curves also remain within a range of 10%. In addition, an Actuator Disk method, which is freqeuntly utilized for the simulation of the fan jet, is expanded in such a way that unsteady flows can be treated. Some unsteady airloads are strongly dependent on the pressure jump across the fan.