A coupled weak-form meshfree method for underwater noise prediction

2022 ◽  
Author(s):  
Shaowei Wu ◽  
Yang Xiang ◽  
Guangnian Li
Keyword(s):  
Meshfree Method ◽  
Weak Form ◽  
Noise Prediction ◽  
Underwater Noise

A Moving Kriging Interpolation Meshfree Method Based on Naturally Stabilized Nodal Integration Scheme for Plate Analysis

2019 ◽  
Vol 16 (04) ◽  
pp. 1850100 ◽  
Author(s):  
Chien H. Thai ◽  
H. Nguyen-Xuan
Keyword(s):  
Computational Cost ◽  
Meshfree Method ◽  
Weak Form ◽  
Delta Function ◽  
Current Approach ◽  
Kriging Interpolation ◽  
Integration Scheme ◽  
Nodal Integration ◽  
Moving Kriging Interpolation ◽  
Quadrature Scheme

A moving Kriging interpolation (MKI) meshfree method based on naturally stabilized nodal integration (NSNI) scheme is presented to study static, free vibration and buckling behaviors of isotropic Reissner–Mindlin plates. Gradient strains are directly computed at nodes similar to the direct nodal integration (DNI). Outstanding features of the current approach are to alleviate instability solutions in the DNI and to decrease computational cost significantly when compared with the traditional high-order Gauss quadrature scheme. The NSNI is a naturally implicit gradient expansion and does not employ a divergence theorem for strain fields as addressed in the stabilized conforming nodal integration method. The present formulation is derived from the Galerkin weak form and avoids a naturally shear-locking phenomenon without using any other techniques. Thanks to satisfied Kronecker delta function property of MKI shape function, essential boundary conditions (BCs) are easily and directly enforced similar to the finite element method. A variety of numerical examples with various geometries, stiffness ratios and BCs are studied to verify the effectiveness of the present approach.

scholarly journals A Meshfree Method for Simulating Myocardial Electrical Activity

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
Heye Zhang ◽  
Huajun Ye ◽  
Wenhua Huang
Keyword(s):  
Shape Function ◽  
Meshfree Method ◽  
Weak Form ◽  
Solution Technique ◽  
Heart Model ◽  
Element Free Galerkin Method ◽  
Element Free Galerkin ◽  
Monodomain Model ◽  
Element Free ◽  
Myocardial Electrical Activity

An element-free Galerkin method (EFGM) is proposed to simulate the propagation of myocardial electrical activation without explicit mesh constraints using a monodomain model. In our framework the geometry of myocardium is first defined by a meshfree particle representation that is, a sufficient number of sample nodes without explicit connectivities are placed in and inside the surface of myocardium. Fiber orientations and other material properties of myocardium are then attached to sample nodes according to their geometrical locations, and over the meshfree particle representation spatial variation of these properties is approximated using the shape function of EFGM. After the monodomain equations are converted to their Galerkin weak form and solved using EFGM, the propagation of myocardial activation can be simulated over the meshfree particle representation. The derivation of this solution technique is presented along a series of numerical experiments and a solution of monodomain model using a FitzHugh-Nagumo (FHN) membrane model in a canine ventricular model and a human-heart model which is constructed from digitized virtual Chinese dataset.

scholarly journals GEOMETRICALLY NONLINEAR ANALYSIS OF MICROSWITCHES USING THE LOCAL MESHFREE METHOD

2008 ◽  
Vol 05 (04) ◽  
pp. 513-532 ◽  
Author(s):  
Y. T. GU
Keyword(s):  
Nonlinear Analysis ◽  
Large Deformation ◽  
Geometrical Nonlinearity ◽  
Meshfree Method ◽  
Weak Form ◽  
Deformation Analysis ◽  
Geometrically Nonlinear ◽  
Mems Devices ◽  
Mesh Distortion ◽  
Geometrically Nonlinear Analysis

In the modeling and simulation of microelectromechanical system (MEMS) devices, such as the microswitch, the large deformation or the geometrical nonlinearity should be considered. Due to the issue of mesh distortion, the finite element method (FEM) is not effective for this large deformation analysis. In this paper, a local meshfree formulation is developed for geometrically nonlinear analysis of MEMS devices. The moving least squares approximation (MLSA) is employed to construct the meshfree shape functions based on the arbitrarily distributed field nodes and the spline weight function. The discrete system of equations for two-dimensional MEMS analysis is obtained using the weighted local weak form, and based on the total Lagrangian (TL) approach, which refers all variables to the initial configuration. The Newton–Raphson iteration technique is used to get the final results. Several typical microswitches are simulated by the developed nonlinear local meshfree method. Some important parameters of these microswitches, e.g. the pull-in voltage, are studied. Compared with the experimental results and results obtained by linear analysis, nonlinear meshfree analysis of microswitches is accurate and efficient. It has demonstrated that the present nonlinear local meshfree formulation is very effective for geometrically nonlinear analysis of MEMS devices, because it totally avoids the issue of mesh distortion in the FEM.

scholarly journals Study of the Sound Escape with the Use of an Air Bubble Curtain in Offshore Pile Driving

2021 ◽  
Vol 9 (2) ◽  
pp. 232
Author(s):  
Yaxi Peng ◽  
Apostolos Tsouvalas ◽  
Tasos Stampoultzoglou ◽  
Andrei Metrikine
Keyword(s):  
Noise Reduction ◽  
Wave Field ◽  
Ecological Impact ◽  
Free Field ◽  
Pile Driving ◽  
Noise Prediction ◽  
Underwater Noise ◽  
Air Bubble ◽  
Noise Transmission ◽  
Bubble Curtain

Underwater noise pollution generated by offshore pile driving has raised serious concerns over the ecological impact on marine life. To comply with the strict governmental regulations on the threshold levels of underwater noise, bubble curtains are usually applied in practice. This paper examines the effectiveness of an air bubble curtain system in noise reduction for offshore pile driving. The focus is placed on the evaluation of noise transmission paths, which are essential for the effective blockage of sound propagation. A coupled two-step approach for the prediction of underwater noise is adopted, which allows us to treat the waterborne and soilborne noise transmission paths separately. The complete model consists of two modules: a noise prediction module for offshore pile driving aiming at the generation and propagation of the wave field and a noise reduction module for predicting the transmission loss in passing through an air bubble curtain. With the proposed model, underwater noise prognosis is examined in the following cases: (i) free-field noise prediction without the air bubble curtain, (ii) waterborne path fully blocked at the position of the air bubble curtain while the rest of the wave field is propagated at the target distance, (iii) similarly to (ii) but with a non-fully blocked waterborne path close to the seabed, and (iv) air bubble curtain modeled explicitly using an effective medium theory. The results provide a clear indication of the amount of energy that can be channeled through the seabed and through possible gaps in the water column adjacent to the seabed. The model allows for a large number of simulations and for a thorough parametric study of the noise escape when a bubble curtain is applied offshore.

A weak-form interpolation meshfree method for computing underwater acoustic radiation

2021 ◽  
Vol 233 ◽  
pp. 109105
Author(s):  
Shaowei Wu ◽  
Yang Xiang ◽  
Bao Liu ◽  
Guangnian Li
Keyword(s):  
Acoustic Radiation ◽  
Meshfree Method ◽  
Weak Form ◽  
Underwater Acoustic

Using Meshfree Weak-Strong Form Method for a 2-D Heat Transfer Problem

2009 ◽  
Author(s):  
S. Zahiri ◽  
F. Daneshmand ◽  
M. H. Akbari
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Transfer Problem ◽  
Interpolation Method ◽  
Meshfree Method ◽  
Weak Form ◽  
Heat Transfer Problem ◽  
Radial Point Interpolation ◽  
Point Interpolation ◽  
Local Weak Form

In this work, the numerical simulation of 2-D heat transfer problem is studied by using a meshfree method. The method is based on the local weak form collocation and the meshfree weak-strong (MWS) form. The goal of the paper is to find the temperature distribution in a rectangular plate. The results obtained are compared by those obtained by use of other numerical methods. Two types of boundary conditions are considered in this paper: Dirichlet and Neumann types. The Local Radial Point Interpolation Method (LRPIM) is used as the meshfree method. It is shown that the essential boundary conditions can be easily enforced as in the Finite Element Method (FEM), since the radial point interpolation shape functions posses the Kronecker delta property. It is also shown that the natural (derivative) boundary conditions can be satisfied by using the MWS method and no additional equation or treatment are needed. The MWS method as presented in this paper works well with local quadrature cells for nodes on the natural boundary and can be generated without any difficulty.

A study of numerical ship underwater noise prediction

2013 ◽  
Vol 66 ◽  
pp. 113-120 ◽  
Author(s):  
Paula Kellett ◽  
Osman Turan ◽  
Atilla Incecik
Keyword(s):  
Noise Prediction ◽  
Underwater Noise

Selection of a leading edge noise prediction method for PNoise

2018 ◽  
pp. 214-223
Author(s):  
AM Faria ◽  
MM Pimenta ◽  
JY Saab Jr. ◽  
S Rodriguez
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Prediction Method ◽  
Leading Edge ◽  
Wind Farms ◽  
Broadband Noise ◽  
Turbulence Energy ◽  
Noise Prediction ◽  
Migration Routes ◽  
Turbulent Inflow

Wind energy expansion is worldwide followed by various limitations, i.e. land availability, the NIMBY (not in my backyard) attitude, interference on birds migration routes and so on. This undeniable expansion is pushing wind farms near populated areas throughout the years, where noise regulation is more stringent. That demands solutions for the wind turbine (WT) industry, in order to produce quieter WT units. Focusing in the subject of airfoil noise prediction, it can help the assessment and design of quieter wind turbine blades. Considering the airfoil noise as a composition of many sound sources, and in light of the fact that the main noise production mechanisms are the airfoil self-noise and the turbulent inflow (TI) noise, this work is concentrated on the latter. TI noise is classified as an interaction noise, produced by the turbulent inflow, incident on the airfoil leading edge (LE). Theoretical and semi-empirical methods for the TI noise prediction are already available, based on Amiet’s broadband noise theory. Analysis of many TI noise prediction methods is provided by this work in the literature review, as well as the turbulence energy spectrum modeling. This is then followed by comparison of the most reliable TI noise methodologies, qualitatively and quantitatively, with the error estimation, compared to the Ffowcs Williams-Hawkings solution for computational aeroacoustics. Basis for integration of airfoil inflow noise prediction into a wind turbine noise prediction code is the final goal of this work.

Road Traffic Noise Prediction Model

2012 ◽  
Vol 3 (4) ◽  
pp. 110-112
Author(s):  
Rahul Singh ◽  
◽  
Parveen Bawa ◽  
Ranjan Kumar Thakur
Keyword(s):  
Prediction Model ◽  
Road Traffic ◽  
Traffic Noise ◽  
Road Traffic Noise ◽  
Noise Prediction
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