Abstract
In this article, a hybrid method combining large eddy simulation with acoustic analogy is presented to predict three-dimensional far field noise induced by flow around a cylinder. Firstly, the governing equation including RANS equations with shear-stress transport (SST) k-ω turbulent model is numerically solved for steady flow field by using Ansys Fluent. Transient flow field is numerically solved by LES. Then, the flow field simulation results are used to compute the flow-induced noise with the FW-H integral equation method and BEM method based on Lighthill acoustic analogy equation in Actran. Before using for flow around a cylinder, accuracy of flow turbulent model in predicting turbulent flow around a cylinder is tested by comparing with available experimental data. According on the simulation result, the characteristic of the acoustic field, noise at some special points in frequency domain, the noise radiation directivity are studied. Analysis of noise distribution and frequency spectrum curves shows that dipole source takes the dominant place in the noise around a cylinder under the conditions of this article. The flow noise around a cylinder is mainly concentrated in the low frequency range.
Highlights
As a basic structural form, cylindrical structure is very common in the fields of traffic transportation engineering, ocean engineering and fluid machinery
Taking the diameter D of the cylinder as the characteristic scale, the scale of the verification model is 20D×10D×3.14D, the inlet of the fluid domain is 5D from the center of the cylinder, the outlet is 15D from the cylinder, and the center of both sides is 5D from the center of the cylinder
The large eddy simulation (LES), stress transport (SST) and k-Omega models are used to simulate the transient flow field around a three-dimensional cylinder, and the farfield radiation noise is calculated by the boundary element method
Summary
As a basic structural form, cylindrical structure is very common in the fields of traffic transportation engineering, ocean engineering and fluid machinery. After flowing through the cylindrical structure, the fluid wakes alternately appear with the vortex at a certain Reynolds number These vortex streets cause pulsating pressure on the cylindrical surface, thereby generating noise. The relationship between the resistance of the flow around the cylinder and the flow noise is studied by the resistance coefficient of the flow around the cylinder and the total sound pressure level[1]. This experiment has been used as a benchmark for many researchers as a calculation reference. The differences of each model were compared, and the flow field simulation method suitable for flow noise calculation was selected. The proposed calculation method can provide support for large-scale ship flow noise prediction
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