scholarly journals Combination of the Improved Diffraction Nonlocal Boundary Condition and Three-Dimensional Wide-Angle Parabolic Equation Decomposition Model for Predicting Radio Wave Propagation

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Ruidong Wang ◽  
Guizhen Lu ◽  
Rongshu Zhang ◽  
Weizhang Xu
Keyword(s):  
Boundary Condition ◽  
Wave Propagation ◽  
Parabolic Equation ◽  
Nonlocal Boundary Condition ◽  
Nonlocal Boundary ◽  
Three Dimensional ◽  
Wide Angle ◽  
Computational Accuracy ◽  
Decomposition Model ◽  
Convolution Integrals

Diffraction nonlocal boundary condition (BC) is one kind of the transparent boundary condition which is used in the finite-difference (FD) parabolic equation (PE). The greatest advantage of the diffraction nonlocal boundary condition is that it can absorb the wave completely by using one layer of grid. However, the speed of computation is low because of the time-consuming spatial convolution integrals. To solve this problem, we introduce the recursive convolution (RC) with vector fitting (VF) method to accelerate the computational speed. Through combining the diffraction nonlocal boundary with RC, we achieve the improved diffraction nonlocal BC. Then we propose a wide-angle three-dimensional parabolic equation (WA-3DPE) decomposition algorithm in which the improved diffraction nonlocal BC is applied and we utilize it to predict the wave propagation problems in the complex environment. Numeric computation and measurement results demonstrate the computational accuracy and speed of the WA-3DPE decomposition model with the improved diffraction nonlocal BC.

scholarly journals A NONLOCAL COMPUTATIONAL BOUNDARY CONDITION FOR DUCT ACOUSTICS

1995 ◽  
Vol 03 (01) ◽  
pp. 15-26 ◽  
Author(s):  
WILLIAM E. ZORUMSKI ◽  
WILLIE R. WATSON ◽  
STEVE L. HODGE
Keyword(s):  
Boundary Condition ◽  
Acoustic Waves ◽  
Nonlocal Boundary Condition ◽  
Nonlocal Boundary ◽  
Three Dimensional ◽  
Computational Domain ◽  
Radiation Boundary Condition ◽  
Constant Matrix ◽  
Duct Acoustics ◽  
Computational Solution

A nonlocal boundary condition is formulated for acoustic waves in ducts without flow. The ducts are two-dimensional with constant area, but with variable impedance wall lining. Extension of the formulation to three-dimensional and variable area ducts is straightforward in principle, but requires significantly more computation. The boundary condition simulates a nonreflecting wave field in an infinite duct. It is implemented by a constant matrix operator which is applied at the boundary of the computational domain. An efficient computational solution scheme is developed which allows calculations for high frequencies and long duct lengths. This computational solution utilizes the boundary condition to limit the computational space while preserving the radiation boundary condition. The boundary condition is tested for several sources. It is demonstrated that the boundary condition can be applied close to the sound sources, rendering the computational domain small. Computational solutions with the new nonlocal boundary condition are shown to be consistent with the known solutions for nonreflecting wave fields in an infinite uniform duct.

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