• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.1-13
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• 2000

This paper presents a review of the methodology, problems and progress in computational aeroacoustics(CAA). The nature, characteristics, and objectives of aeroacoustics problems are quite different from the commonly encountered CFD problems. In this paper, computational methods that are designed especially for CAA applications are introduced. The potential offered by CAA, the numerical issues which need to be given careful attention, and some of the recent progress in solving aeroacoustic problem are discussed

• The Journal of the Acoustical Society of Korea
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• v.25 no.2E
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• pp.85-88
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• 2006

Blade-vortex interaction (BVI) is one of the most important phenomena in rotor flow since it causes undesirable intense vibration and noise. Since three dimensional Euler or Navier-Stokes solutions to BVI require very high computational cost, BVI has been approximated by airfoil-vortex interaction (AVI) in chordwise planes. To describe more realistic situations with AVI, three dimensional vortex informations such as position, core size and strength are embedded artificially to Computational Aeroacoustics (CAA) calculation at each computational time step. To implement this requirement, in this paper, a technique called free vortex embedded method was used. And the solution by this method was compared with the solution by conventional method for interaction between freely convected vortex and airfoil. For the application to three dimensional free vortex embedded CAA, two dimensional free vortex embedded CAA method was validated in advance.

• Journal of computational fluids engineering
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• v.18 no.1
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• pp.22-27
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• 2013

Researches in the area of aeroacoustics have been conducted by two methods. In the first method theoretical formula or experimentation are utilized, and in the second method flow field analysis and acoustic analogy are utilized. In contrast to the first method, the second method does not need new experiments for every individual change of flow configurations and conditions, and it can predict their effects by the flow field analysis, which makes the second method preferred than the first one. In this paper numerical analysis to predict noise generated by a turbulent flow about a two dimensional circular cylinder by use of CAA (Computational Aeroacoustics) method is conducted and the results are compared to the available experimental data.

• Journal of the Korean Society of Visualization
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• v.2 no.2
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• pp.3-7
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• 2004

In this paper, computational aeroacoustics (CAA) method is used for flow-noise analysis and flow-noise visualization. High order high resolution scheme of optimized high order compact is used to resolve the small acoustic quantities and large flow quantities at the same time. An adaptive nonlinear artificial dissipation model and generalized characteristic boundary condition are also used. Aeolion tone noise, cavity noise, and jet noise are investigated. The visualizations of flow-noise are successful and characteristics of noise are studied. It is observed that the propagation directivity of noise is different with that of flow. With the help of CAA method, the visualization of noise is possible.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.66-68
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• 2006

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.46.5-47
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• 2008

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.757-761
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• 2001

In order to study noise barriers of complex shapes and to assess their efficiency, precise prediction model is required. For instance, geometrical approaches cannot deal with complex diffraction effects. So that in this paper, the time domain numerical computation method(Computational Aeroacoustics method) is applied to estimate noise reduction by diffraction and finite impedance condition. The CAA method can be used to calculate exactly the pressure of complex barrier shape with different impedance condition, such as T-shape, cylindrical edge and multi-edge noise barriers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.291-291
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• 2013

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. HMC is interested in the numerical prediction of this aerodynamic noise generated by the car windows with the final objective of improving the products design and reducing this noise. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using the CAA(Computational aeroacoustics) solver CAA++. The second step consists in the computation of the vibro-acoustic transmission through the side window using the finite element vibro-acoustic solver Actran. The internal air cavity including trim component are included in the simulation. In order to validate the numerical process, an experimental set-up has been created based on a generic car shape. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. First, this paper describes the method including the CAA and the vibro-acoustic models, from the boundary conditions to the different components involved, like the windows, the trims and the car cavity is detailed. In a second step, the experimental set-up is described. In the last part, the vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

• The Journal of the Acoustical Society of Korea
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• v.32 no.5
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• pp.369-376
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• 2013

Using Lowson's acoustic analogy, low frequency noise of a wind turbine (WT) is predicted in time domain and the noise sources contributing to the low frequency noise is analyzed. To compute averaged pressure distribution on blades of the WT as noise source, XFOIL is utilized. The blade source domain is divided into several segments along the span direction to compute force exerted on air surrounding the blade segments, which is used as input for noise prediction. The noise sources are decomposed into three terms of force fluctuation, acceleration and velocity terms and are analyzed to investigate each spectral contribution. Finally, predicted spectra are compared with measured low frequency noise spectrum of a wind turbine in operation. It is found that the force fluctuation component contributes strongly in low frequency range with increasing wind speed.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.76-80
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• 2001

Unsteady compressible Euler equation is solved and the high-order, high-resolution numerical solver, physical boundary condition, adaptive nonlinear artificial dissipation model and conformal mapping are applied to computation of steady transonic flow and unsteady acoustics. The acoustic characteristics of axi-symmetric duct and two dimensional straight/S channel are studied and the computation results shows good agreements with linear analysis. In transonic case, local time stepping and canceling-the-residual techniques are used for convergence acceleration. The aspect of flow and acoustics in S-channel and the Pattern of noise radiation is changed by inflow Mach no. and static pressure at fan-face.