A Preconditioned Arbitrary Mach Number Scheme Applied to Rotating Machinery

Predicting Cooling Fan Noise of Electric Motor Using Compressible Large Eddy Simulation

Volume 3B: Fluid Applications and Systems ◽

10.1115/ajkfluids2019-4699 ◽

2019 ◽

Author(s):

Kimihisa Kaneko ◽

Tsutomu Yamamoto

Keyword(s):

Mach Number ◽

Large Eddy Simulation ◽

Electric Motor ◽

Pressure Fluctuation ◽

Sound Pressure ◽

Sound Propagation ◽

Rotating Machinery ◽

Eddy Simulation ◽

Large Eddy ◽

Good Agreement

Abstract This paper describes prediction of aeroacoustics from a rotating machinery fan using compressible Large Eddy Simulation (LES). The fan is installed semi-opened space located between the fan cover and the body of rotating machinery such as a electric motor. The fan distributes air from the fan cover intake onto the cooling fins. The Reynolds number of the rotating fan is 9 × 105; its Mach number is approximately 0.1. Under the low Mach number regime, hybrid computational aeroacoustics (hybrid CAA) method, which is solved turbulent flow and acoustics separately, is generally used. However, we used a direct CAA method because interaction between pressure fluctuation from the turbulence and sound propagation should be considered. For the direct CAA method approach, compressible Navier–Stokes equations are solved. Density is calculated from the ideal gas law. To compute turbulence phenomena, LES is used as the turbulence model. The Dynamic Smagorinsky Model is used for the subgrid scale. The sound propagation speed is approximately 10 times faster than the flow speed. Therefore, the numerical schemes, time step, and computational grids size were evaluated with line sound source in the two-dimensional domain as a fundamental study to determine the numerical schemes. Subsequently we evaluated the sound pressure level with the electric motor fan, which is an experimental structure. Through verification of the direct CAA model, we obtained the following results. (1) The predicted pressure fluctuation spectra show good agreement with the experimentally obtained spectra. Specifically, the blade passing frequency (BPF) and trend of the pressure fluctuation decay in the inertial turbulence subrange were predicted. (2) The predicted sound pressure spectra also show good agreement with BPF. Specifically, the acoustic mode and broadband turbulence noise level were predicted.

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A Global Preconditioning Method for Low Mach Number Viscous Flows in Rotating Machinery

Volume 6: Turbomachinery, Parts A and B ◽

10.1115/gt2006-91189 ◽

2006 ◽

Cited By ~ 1

Author(s):

Chunhua Sheng ◽

Xiao Wang

Keyword(s):

Mach Number ◽

Rotational Speed ◽

Stokes Equations ◽

Viscous Flows ◽

Rotating Machinery ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Low Mach Number ◽

Low Speed ◽

Preconditioning Method

A preconditioning scheme is applied to a compressible turbomachinery flow solver MSU-TURBO for simulating viscous flows at low Mach number and incompressible region. The Navier-Stokes equations are cast in a non-inertial rotating frame. A constant diagonal preconditioning matrix is applied to the conservative form of the governing equations, which contains a single parameter depending on the reference Mach number and rotational speed of the relative frame. The effect of the rotational speed on preconditioned scheme is numerically investigated for two low speed viscous flows in rotating machinery, a NASA low speed centrifugal compressor (LSCC) and a marine propeller (P5168). Computations are compared against the original MSU-TURBO solutions, and suggestions are provided for computing the low Mach number flows in rotating turbomachinery using the preconditioned TURBO solver.

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