An Overview of High Fidelity CFD Engine Modeling

Abstract

In this work we give an overview over state of the art engine performance modeling with CFD. For both flow solvers predominantly used at DLR we show the available methods to model aircraft engine performance with high fidelity. Within the TAU code, a solver mainly used for outer aerodynamics, full annulus uRANS simulations with a rotating fan may be used to model the engine accurately. In RANS simulations an actuator disk method or a body force model are available to represent the fan stage. In the flow solver TRACE, primarily developed to model internal turbomachinery flow, single passage RANS simulations with mixing-planes or uRANS simulations with time-shifted boundary conditions can be used. Additionally full annulus uRANS simulations may be performed as well. A test case is run with the aforementioned engine modeling methods allowing for comparison and evaluation of the different models. Integral engine performance metrics and radial distributions are compared to assess the capabilities of different simulation approaches. High fidelity 360° uRANS methods deliver accurate results but are costly in terms of time and resources. The RANS methods presented pose as viable alternatives to model engine performance metrics requiring only a fraction of the resources of an unsteady simulation. Single passage uRANS simulations utilizing time shifted boundary conditions fill the gap between full annulus uRANS and RANS methods by simulating unsteady aerodynamic phenomena with an acceptable demand for computational resources.