German Aerospace

This study is focused on developing a process that couples the near-field unsteady flow field data computed by a 3-D Detached Eddy Simulation (DES) code with a Ffowcs Williams -Hawkings (FW-H) formulation for the far-field noise prediction of turbulent jets. In particular the numerical method to create a general and flexible interface between these simulation methodologies is presented. It is shown that using DES for the near-field and a FW-H approach for the far-field yields a versatile tool for jet noise prediction. Nomenclature c 0 speed of sound c b bias constant of DES scheme C DES calibration constant of DES model (C DES ≈ 0.

The present paper describes the use of various high-order schemes in a finite volume formulation for use on structured grids. In particular, WENO and compact upwind schemes as well as central and upwind schemes are investigated. Their efficiency and accuracy are compared to the well-established second- and third-order MUSCL family of schemes. The different schemes are analyzed and tested numerically using canonical flow problems in the context of the two-dimensional Euler equations. Results are shown for the two-dimensional advection of a density pulse to quantify the dissipation and dispersion properties of the schemes. To investigate the non-oscillatory nature of the schemes and the resolution of discontinuities the Riemann problem is analyzed. The simulations are performed on uniform as well as non-uniform meshes.

This work is about numerical simulations of vortex induced acoustic resonance in a duct, experimentally investigated by Welsh et al. Vortex shedding of low-speed flow over a flat plate excites an acoustic duct mode, leading to a lock-in of shedding and acoustic resonance frequency over a wide range of flow velocities. This study shows that a state-of-the-art compressible Navier–Stokes flow solver is able to capture the lock-in phenomenon. The focus is on the numerical parameters required to precisely recover the experimental results in terms of lock-in range and acoustic pressure levels. Complete and reliable physical data are thereby obtained, which can aid in developing a systematic understanding of the complex flow interactions. Furthermore, hysteresis behavior is discovered and numerically explored.

In this paper, various averaging techniques commonly used in turbomachinery applications are analyzed. It is shown how the work average relates to Miller’s mechanical work potential and that it is, in a certain way, consistent with Hartsel’s cooled turbine efficiency. It is found that a key to understand these approaches is to analyze the impact that entropy variations at inflows have on them. Second-order asymptotics of mixing entropy are used to establish a close relationship between flux and work averages. It is found that the mixing entropy asymptotic due to entropy modes is identical for both averages. The work average, along with Miller’s mechanical work potential analysis, is as optimistic as the entropy average for vorticity and acoustic modes, but as pessimistic as the flux averaging for entropy variations. This explains why mechanical work potential-based analysis is pessimistic about the inflow and thus optimistic about the efficiency of a turbine for high entropy variati...