Abstract

A Large-Eddy Simulation of the tip leakage flow of a single airfoil is carried out. The configuration consists of a non-rotating, isolated airfoil between two horizontal plates with a gap of 10 mm between the tip of the airfoil and the lower plate. The Mach number of the incoming flow is 0.2, and the Reynolds number based on the chord is 9.3 × 105. The objective of the present study is to investigate the best way to compute both the aerodynamics and acoustics of the tip leakage flow. In particular, the importance of the inflow conditions on the prediction of the tip leakage vortex and the airfoil loading is underlined. On the other hand, the complex structure of the tip leakage vortex and its convection along the airfoil was recovered due to the use of a mesh adaptation based on the dissipation of the kinetic energy. Finally, the ability of the wall law to model the flow in the tip leakage flow region was proven in terms of wall pressure fluctuations and acoustics in the far-field.

Highlights

  • Due to strong environmental constraints regarding the noise emitted by aircraft, the bypass ratio of modern turbofan engines has tended to increase

  • This mechanism consists of coherent vortical structures coming from the tip clearance that interact with the fan blades, causing periodic fluctuations of the blade loading, and inducing tonal noise in the far field

  • The objective of the present study is to investigate the best way to compute both the aerodynamics and acoustics of the tip leakage flow in order to transfer the methodology to real turbomachinery configurations

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Summary

Introduction

Due to strong environmental constraints regarding the noise emitted by aircraft, the bypass ratio of modern turbofan engines has tended to increase. Kameier and Neise [3] identified a component of the tip clearance noise called the rotating instability This mechanism consists of coherent vortical structures coming from the tip clearance that interact with the fan blades, causing periodic fluctuations of the blade loading, and inducing tonal noise in the far field. As these vortices have a range of tangential velocities, broadband humps are observed instead of sharp tonal peaks. Concluding remarks and perspectives are given in the last section

Experimental Set-Up
Numerical Settings
Instantaneous Flow
Mean Flow
Tip Leakage Vortex Trajectory
Tip Leakage Vortex Convection
Spectral Signature of the Tip Leakage Flow
Findings
Conclusions
Full Text
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