An efficient and high-order sliding mesh method for computational aeroacoustics

This paper presents an efficient sliding mesh method to simulate the noise emission from aero-engines. The vortexes shed from the rotating blade and interact with the downstream stationary outlet guide vanes (OGVs), producing noise. The challenges in simulating the problem are the accurate modelling of the wake turbulence, and the capabilities to capture the acoustic waves, the energy of which is several orders lower than the turbulent components. To model the relative motion between the rotors and OGVs, a sliding mesh method is developed to account for the rotation of the rotor blades and wakes, which can lead to efficiency and accuracy challenges. In this work, an advanced treatment is developed for efficient and high-accuracy interpolation by combining both patch and sliding interfaces. The grid along the sliding interface is uniformly distributed taking advantage of the patch interface, providing huge benefits to the overall performance by reusing data and omitting repeated calculation. The algorithm using message passing interface is well designed for maintaining ideal performance of the code. The fan–OGV geometry is represented as unwrapped two-dimensional cascades with isotropic and anisotropic turbulence synthesised and injected to simulate the fan-wake. The numerical results are compared to analytical solutions for accuracy validation. The simulations numerically reveal the effect of turbulence intensity, length scale and anisotropy in the fan wake on the noise emission due to the turbulence-OGV interaction. Also the blockage effect of rotating blades on the noise propagation and its impact on the hearing of observers are discussed. Moreover, it is shown that the new method is able to maintain a high accuracy for acoustic computation and an ideal performance is obtained from the numerical code using a parallel computing algorithm.