Non-Reflective Boundary Conditions for CAA
Summary
Non-reflective boundary conditions are essential for accurate computational aeroacoustic (CAA) simulations. Benchmark test cases were developed to quantify the reflections generated by outgoing acoustic and vortical disturbances. These test cases were used to develop a new blended zonal characteristic boundary condition (CBC) with optimized parameters to maximise the solution accuracy.
A zonal characteristic boundary condition was developed from two benchmark test cases. The acoustic plane wave tests accurately quantify the reflections generated a boundary condition across a range of Mach number, wave angle, and streamwise and transverse wave numbers. The other benchmark test case used synthetic turbulence to model the vorticity disturbances. Several tests were conducted to evaluate the performance of various methods. The free parameters in the zonal characteristic method were optimized to minimize the acoustic reflections for both acoustic and vortical cases. The final result is a near-perfect non-reflective boundary condition. Finally, the optimal methods from both benchmark cases were blended into a generalized formula
A zonal characteristic boundary condition was developed from two
benchmark test cases. The acoustic plane wave tests accurately
quantify the reflections generated a boundary condition across a
range of Mach number, wave angle, and streamwise and transverse
wave numbers.
The other benchmark test case used synthetic turbulence to model
the vorticity disturbances. Several tests were conducted to evaluate
the performance of various methods.
The free parameters in the zonal characteristic method were
optimized to minimize the acoustic reflections for both acoustic
and vortical cases. The final result is a near-perfect non-reflective
boundary condition. Finally, the optimal methods from both
benchmark cases were blended into a generalized formulation that
automatically switches depending on the local vorticity magnitude.
