Wavelet BEM for large-scale Stokes flows based on the direct integral formulation

2011 ◽  
Vol 88 (7) ◽  
pp. 693-714 ◽  
Author(s):  
Jinyou Xiao ◽  
Wenjing Ye
Keyword(s):  
Large Scale ◽  
Integral Formulation ◽  
Direct Integral ◽  
Stokes Flows

A Surface-Integral Formulation for Jet Noise Prediction Based on the Pressure Signal Alone

1998 ◽  
Vol 06 (03) ◽  
pp. 307-320 ◽  
Author(s):  
R. R. Mankbadi ◽  
S. H. Shih ◽  
D. R. Hixon ◽  
J. T. Stuart ◽  
L. A. Povinelli
Keyword(s):  
Cylindrical Surface ◽  
Large Scale ◽  
Near Field ◽  
Jet Noise ◽  
Normal Derivative ◽  
Integral Formulation ◽  
Noise Prediction ◽  
Far Field ◽  
Surface Integral ◽  
Large Scale Simulation

While large-scale simulation of jet noise is the most thorough technique currently available for jet noise prediction, three-dimensional direct computation of both the near and far field requires prohibitive computational capability. In this work we propose to limit large-scale simulation to the near field to provide the pressure distribution over a cylindrical surface surrounding the jet. A surface-integral formulation is presented herein in which the calculated pressure on the cylindrical surface is used to obtain the far-field sound, without the need for the normal derivative of the pressure. The results are compared to that of direct large-scale simulation and to the zonal approach in which linearized Euler equations are used as an extension tool.

scholarly journals Damage Detection for Large-Scale Grid Structure Based on Virtual Axial Strain

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jian-xin Yu ◽  
Hui-feng Tan
Keyword(s):  
Damage Detection ◽  
Large Scale ◽  
Domain Decomposition Method ◽  
Axial Strain ◽  
Time History ◽  
Space Structure ◽  
Grid Structure ◽  
Modal Parameter ◽  
Direct Integral ◽  
Frequency Domain Decomposition

To identify the damaged beams in large-scale spatial structure, a damage indicator based on virtual axial strain calculated from mode shape vectors was proposed. The damage detection process was performed based on the dynamic simulation flowchart. Firstly, random signals were used for excitation and the damage was simulated by decreasing beam elasticity modulus. Then, the NEWMARK-β precision direct integral method was appreciated for calculating time history response. Finally, the frequency-domain decomposition method only using output response signal was selected for modal parameter estimation. A double-layer grid structure was taken as example for verifying the damage detection method. Results indicate that the proposed indicator was insensitive to environmental noise and capable of localizing multiple damaged members in space structure without the baseline data.

Muffler Performance Studies Using a Direct Mixed-Body Boundary Element Method and a Three-Point Method for Evaluating Transmission Loss

1996 ◽  
Vol 118 (3) ◽  
pp. 479-484 ◽  
Author(s):  
T. W. Wu ◽  
G. C. Wan
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Velocity Potential ◽  
Transmission Loss ◽  
Point Method ◽  
Integral Formulation ◽  
Pressure Jump ◽  
Direct Integral ◽  
Body Boundary ◽  
Element Method

In this paper, a single-domain boundary element method is presented for muffler analysis. This method is based on a direct mixed-body boundary integral formulation recently developed for acoustic radiation and scattering from a mix of regular and thin bodies. The main feature of the mixed-body integral formulation is that it can handle all kinds of complex internal geometries, such as thin baffles, extended inlet/outlet tubes, and perforated tubes, without using the tedious multi-domain approach. The variables used in the direct integral formulation are the velocity potential (or sound pressure) on the regular wall surfaces, and the velocity potential jump (or pressure jump) on any thin-body or perforated surfaces. The linear impedance boundary condition proposed by Sullivan and Crocker (1978) for perforated tubes is incorporated into the mixed-body integral formulation. The transmission loss is evaluated by a new method called “the three-point method.” Unlike the conventional four-pole transfer-matrix approach that requires two separate computer runs for each frequency, the three-point method can directly evaluate the transmission loss in one single boundary-element run. Numerical results are compared to existing experimental data for three different muffler configurations.

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