scholarly journals A Study of Multi-Component Oscillating-Foil Hydrokinetic Turbines with a GPU-Accelerated Boundary Element Method

2019 ◽  
Vol 7 (12) ◽  
pp. 424 ◽  
Author(s):  
Panagiotis E. Koutsogiannakis ◽  
Evangelos S. Filippas ◽  
Kostas A. Belibassakis
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
High Performance ◽  
Singular Integrals ◽  
The Body ◽  
Initial Shape ◽  
Hydrokinetic Turbines ◽  
Parallel Configuration ◽  
Oscillating Foil ◽  
Element Method

A biomimetic semi-activated oscillating-foil device with multiple foils in a parallel configuration is studied for the extraction of marine renewable energy. For the present investigation, an unsteady boundary element method (BEM) is used for the simulation of 3D lifting flows. For this work, the device is assumed to be submerged far from the free surface and the sea bottom. However, the geometry of the body and the initial shape of the wake are general. For the numerical simulations, a high performance in-house GPU-accelerated code (GPU-BEM) is developed. For the calculation of singular integrals, an adaptive algorithm based on the Gauss–Lobatto quadrature is used. Concerning the numerical scheme of GPU-BEM, the convergence of the method was tested, the numerical characteristics were determined and the method was validated. A parametric study of a single-foil device is presented to determine the performance characteristics of such devices. Next, twin-foil devices are investigated in parallel and staggered configurations with a phase difference between the two foils. Finally, the multiple-foil parallel configuration is compared against turbines. After enhancement and further verification, the present method is proposed for the design and control of such biomimetic devices for the extraction of energy from waves and tidal currents nearshore.

Realistic Design of a Floating Breakwater Design with Moonpools

2015 ◽  
Vol 69 (7) ◽  
Author(s):  
Faisal Mahmuddin ◽  
Rahimuddin Rahimuddin
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
High Performance ◽  
3D Model ◽  
Longitudinal Direction ◽  
Realistic Model ◽  
The Body ◽  
Efficient Design ◽  
Floating Breakwater ◽  
Element Method

In an attempt to obtain a 2D floating breakwater model with high performance in wave reflection, genetic algorithm (GA) was combined with boundary element method (BEM) in the previous study. The performance of the obtained model was verified with numerical relations as well as an experiment in towing tank. Moreover, its performance and characteristics in 3D case were also evaluated in the subsequent study. However, because the 3D model is formed by simply extruding the 2D shape in longitudinal direction, it only produces a model with uniform transversal shape which is considered to be less effective and efficient in terms of technical and economical points of view. Consequently, it is needed to modify the model to obtain a more realistic and efficient design without reducing significantly the high performance obtained previously. In the present study, several modifications of the original 3D model are performed which include placing moonpools inside the body. The performance and characteristics of the modified models in terms of wave elevations on the free surface are evaluated at various wavelengths by using higher order boundary element method (HOBEM). The accuracy of the computed results is confirmed with Haskind-Newman and energy conservation relations. From the modifications and evaluations of the models, it could be realized that the moonpools inside the body could be used to obtain a more realistic model without reducing the optimum performance of the original model shape.  

A modal boundary element method for axisymmetric acoustic problems in an arbitrary uniform mean flow

2020 ◽  
pp. 1475472X2097838
Author(s):  
Bassem Barhoumi ◽  
Jamel Bessrour
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Singular Integrals ◽  
Acoustic Radiation ◽  
Normal Derivative ◽  
Boundary Integral ◽  
Meridian Plane ◽  
Mean Flow ◽  
Transform Method ◽  
Element Method

This paper presents a new numerical analysis approach based on an improved Modal Boundary Element Method (MBEM) formulation for axisymmetric acoustic radiation and propagation problems in a uniform mean flow of arbitrary direction. It is based on the homogeneous Modal Convected Helmholtz Equation (MCHE) and its convected Green’s kernel using a Fourier transform method. In order to simplify the flow terms, a general modal boundary integral solution is formulated explicitly according to two new operators such as the particular and convected kernels. Through the use of modified operators, the improved MBEM approach with flow takes a convective form of the general MBEM approach and has a similar form of the nonflow MBEM formulation. The reference and reduced Helmholtz Integral Equations (HIEs) are implicitly taken into account a new nonreflecting Sommerfeld condition to solve far field axisymmetric regions in a uniform mean flow. For isolating the singular integrations, the modal convected Green’s kernel and its modified normal derivative are performed partly analytically in terms of Laplace coefficients and partly numerically in terms of Fourier coefficients. These coefficients are computed by recursion schemes and Gauss-Legendre quadrature standard formulae. Specifically, standard forms of the free term and its convected angle resulting from the singular integrals can be expressed only in terms of real angles in meridian plane. To demonstrate the application of the improved MBEM formulation, three exterior acoustic case studies are considered. These verification cases are based on new analytic formulations for axisymmetric acoustic sources, such as axisymmetric monopole, axial and radial dipole sources in the presence of an arbitrary uniform mean flow. Directivity plots obtained using the proposed technique are compared with the analytical results.

scholarly journals High-performance practical stiffness analysis of high-rise buildings using superfloor elements

2020 ◽  
Vol 7 (2) ◽  
pp. 211-227
Author(s):  
Ahmed A Torky ◽  
Youssef F Rashed
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Stiffness Matrix ◽  
High Performance ◽  
Parallel Processors ◽  
Element Formulation ◽  
Processing Unit ◽  
Stiffness Analysis ◽  
Industrial Level ◽  
Element Method

Abstract This study develops a high-performance computing method using OpenACC (Open Accelerator) for the stiffness matrix and load vector generation of shear-deformable plates in bending using the boundary element method on parallel processors. The boundary element formulation for plates in bending is used to derive fully populated displacement-based stiffness matrices and load vectors at degrees of freedom of interest. The computed stiffness matrix of the plate is defined as a single superfloor element and can be solved using stiffness analysis, $Ku = F$, instead of the conventional boundary element method, $Hu = Gt$. Fortran OpenACC code implementations are proposed for the computation of the superfloor element’s stiffness, which includes one serial computing code for the CPU (central processing unit) and two parallel computing codes for the GPU (graphics processing unit) and multicore CPU. As industrial level practical floors are full of supports and geometrical information, the computation time of superfloor elements is reduced dramatically when computing on parallel processors. It is demonstrated that the OpenACC implementation does not affect numerical accuracy. The feasibility and accuracy are confirmed by numerical examples that include real buildings with industrial level structural floors. Engineering computations for massive floors with immense geometrical detail and a multitude of load cases can be modeled as is without the need for simplification.

The Optimum Design of a Cavitator for High-Speed Axisymmetric Bodies in Partially Cavitating Flows

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
I. Rashidi ◽  
Mo. Passandideh-Fard ◽  
Ma. Pasandideh-Fard
Keyword(s):  
Boundary Element Method ◽  
Numerical Simulations ◽  
Drag Coefficient ◽  
Boundary Element ◽  
Cavitation Number ◽  
The Body ◽  
Total Drag ◽  
Conical Section ◽  
Disk Cavitator ◽  
Element Method

In this paper, the partially cavitating flow over an axisymmetric projectile is studied in order to obtain the optimum cavitator such that, at a given cavitation number, the total drag coefficient of the projectile is minimum. For this purpose, the boundary element method and numerical simulations are used. A large number of cavitator profiles are produced using a parabolic expression with three geometric parameters. The potential flow around these cavitators is then solved using the boundary element method. In order to examine the optimization results, several cavitators with a total drag coefficient close to that of the optimum cavitators are also numerically simulated. Eventually, the optimum cavitator is selected using both the boundary element method and numerical simulations. The effects of the body radius and the length of the conical section of the projectile on the shape of the optimized cavitator are also investigated. The results show that for all cavitation numbers, the cavitator that creates a cavity covering the entire conical section of the projectile with a minimum total drag coefficient is optimal. It can be seen that increasing the cavitation number causes the optimum cavitator to approach the disk cavitator. The results also show that at a fixed cavitation number, the increase in both the radius and length of the conical section causes the cavitator shape to approach that of the disk cavitator.

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