M. Kamalian and A. Sohrabi Bidar,
Volume 24, Issue 2 (1-2006)
Abstract
This paper presents the complete algorithm of site response analysis of nonhomogeneous topographic structures using transient two-dimensional boundary element method (BEM). Seismic behaviour of various topographic features including canyon, half plane, sedimentary filled valley and ridge sections, subjected to incident SV and P waves are analysed. The analysis shows the efficiency of the proposed algorithm and its advantage over common transformed domains methods in forming a basis for extension to non-linear behaviour.
Ali Pashaee and Nasser Fotouraee,
Volume 27, Issue 1 (7-2008)
Abstract
In this paper, the boundary-based estimation of pressure distribution in the cardiovascular system is investigated using two dimensional flow images. The conventional methods of non-invasive estimation of pressure distribution in the cardiovascular flow domain use the differential form of governing equations. This study evaluates the advantages of using the integral form of the equations in these calculations. The concepts provided with the Boundary Element Method (BEM) together with the boundary-based image segmentation tools are used to develop a fast calculation method. Boundary-based segmentation provides BEM with domain pixel extraction, boundary meshing, wall normal vector calculation, and accurate calculation of boundary element length. The integral form of the governing equations are reviewed in detail and the analytic value of integral constants at singular points are provided. The pressure data on boundary nodes are calculated to obtain the pressure data at every point in the domain. Therefore, the calculation of domain pressure could be considered as a post-processing procedure, which is an advantage of this approach. Both the differential and integral-based formulations are evaluated using mathematical Couette test flow image whose pressure domain is available. The resulting pressure distributions from both methods will be compared. According to the results obtained from this study, the use of BEM for estimating pressure values from a non-invasive flow image has the following advantages: reduced computational domain from two to one dimension, flexible calculation of pressure data at arbitrary points or at finer spatial resolutions, robustness against noise, less concern for its stability and compatibility, accuracy, and lower meshing attempts.
E. Yari , H. Ghassemi,
Volume 34, Issue 2 (1-2016)
Abstract
The main objective of this paper is to provide an applied algorithm for analyzing propeller-shaft vibrations in marine vessels. Firstly an underwater marine vehicle has been analyzed at different speed in unsteady condition using the finite volume method. Based on the results of this analysis, flow field of marine vehicle (wake of stern) and velocity inlet to the marine propeller is extracted at different times. Propeller inlet flow field is applied in the boundary element code and using this code, marine propeller has been analyzed in unsteady state. In continue, main / lateral forces and moments over the propeller are extracted. Then the data obtained from the boundary element code alongwith exact geometry of the propeller and shaft have been studied, using finite element code. Natural and forced frequency of the propeller have been determined in various modes of vibration. According to obtained data from Finite Element Method (FEM) numerical analysis, maximum displacement of propeller is for displacement of the propeller tip in forced vibration state
