B. J. Zhu^1,2, Z. X. Hou¹, Y. F. Lu¹, S. Q. Shan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.105, No.6, pp. 467-490, 2015, DOI:10.3970/cmes.2015.105.467

Abstract This paper mainly analyzes the dynamic soaring of UAV utilizing gradient wind. Dynamic soaring is an efficient path in which UAV absorbs energy from environment to enhance its flight endurance. A set of three-dimensional point dynamic equations for a soaring aircraft in three degrees of freedom is used in calculations. To simplify the calculation, the gradient wind’s direction is taken into decomposition. The notion of trajectory subsection analysis is applied to account for the energy transformation mechanism during the dynamic soaring, and the zone of direction is converted into cutting-in angle, which is regarded as initial limiting condition in the… More >

Zhaohui Xu¹, Deli Gao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 17-24, 2012, DOI:10.3970/cmes.2012.089.017

Abstract Little is explained about the process of casing window milling for sidetracking due to lack of analytical method for its mechanical characteristic. In this paper, 3D FE models are established using the commercial finite-element software ABAQUS/Explicit to make simulation analysis for two key stages of the process including the initial stage of casing milling and the stage of full-gauge casing window milling. The models involve the effects of main drilling parameters such as reaction force, torque, speed, feed rate per revolution, and milling angle. The calculation results verify the capability and advantages of 3D FE simulation for the process of… More >

D.-A. An-Vo¹, N. Mai-Duy¹, T. Tran-Cong¹

CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.2, pp. 141-178, 2011, DOI:10.3970/cmes.2011.080.141

Abstract In this paper, 2-node integrated radial basis function elements (IRBFEs) [CMES, vol.72, no.4, pp.299-334, 2011] are further developed for the simulation of incompressible viscous flows in two dimensions. Emphasis is placed on (i) the incorporation of C²-continuous 2-node IRBFEs into the subregion and point collocation frameworks for the discretisation of the stream function-vorticity formulation on Cartesian grids; and (ii) the development of high order upwind schemes based on 2-node IRBFEs for the case of convection-dominant flows. High levels of accuracy and efficiency of the present methods are demonstrated by solutions of several benchmark problems defined on rectangular and non-rectangular domains. More >

Yuta Kitamura¹, Noriyuki Miyazaki¹, Takahito Kumazaki², Naoto Nagakura³, Yasuhiro Hashimoto³, Isao Masada³

CMES-Computer Modeling in Engineering & Sciences, Vol.68, No.2, pp. 151-166, 2010, DOI:10.3970/cmes.2010.068.151

Abstract CaF₂ single crystal is used as high performance optical elements. We developed an analysis system for simulating birefringence of CaF₂ single crystal used as a chamber window of a gas laser light source. The analysis system consists of a stress analysis and a birefringence analysis. In the stress analysis, the finite element method was applied to obtain the mechanical stress caused by a window holder and gas pressure. In the birefringence analysis, the photo-elastic effect gives the change of refractive indices, from which the optical path difference and the fast axis are calculated by using the average stress method. The… More >

Eugenio Brusa¹, Matteo Nobile²

CMES-Computer Modeling in Engineering & Sciences, Vol.48, No.2, pp. 155-190, 2009, DOI:10.3970/cmes.2009.048.155

Abstract Lightness of high pressure vessels is currently assured by composite materials. Construction of over-wrapped composite pressure vessels with inner metallic liner is for instance compatible with standards requirements of the hydrogen technology of energy storage. Therefore a typical layout manufactured by some industries consists of a cylindrical vessel with covering of carbon-epoxy laminates and metallic impermeable liner. To allow the filament winding of the composite fibres are used hoop and helical layers, respectively. A single nozzle is usually built. It requires that the vessel material is reinforced. This need imposes to have a variable thickness in the composite layer. In… More >

M. Haji Mohammadi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.2, pp. 75-94, 2008, DOI:10.3970/cmes.2008.029.075

Abstract In this paper, the truly Meshless Local Petrov-Galerkin (MLPG) method is extended for computation of steady incompressible flows, governed by the Navier--Stokes equations (NSE), in vorticity-stream function formulation. The present method is a truly meshless method based on only a number of randomly located nodes. The formulation is based on two equations including stream function Poisson equation and vorticity advection-dispersion-reaction equation (ADRE). The meshless method is based on a local weighted residual method with the Heaviside step function and quartic spline as the test functions respectively over a local subdomain. Radial basis functions (RBF) interpolation is employed in shape function… More >

Shueei-Muh Lin¹, Sen-Yung Lee², Yu-Sheng Lin³

CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.3, pp. 175-186, 2008, DOI:10.3970/cmes.2008.023.175

Abstract The blade of a horizontal-axis wind power turbine is modeled as a rotating beam with pre-cone angles and setting angles. Based on the Bernoulli-Euler beam theory, without considering the axial extension deformation and the Coriolis forces effect, the governing differential equations for the bending vibration of the beam are derived. It is pointed out that if the geometric and the material properties of the beam are in polynomial forms, then the exact solution for the system can be obtained. Based on the frequency relations as revealed, without tedious numerical analysis, one can reach many general qualitative conclusions between the natural… More >

Baran Aydın^1,2, Utku Kânoğlu³

CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.2, pp. 149-156, 2007, DOI:10.3970/cmes.2007.021.149

Abstract We developed analytical solutions to the wind set-down and the wind set-down relaxation problems. The response of the ocean to the wind blowing over a long-narrow and linearly sloping shallow basin is referred to as wind set-down. The shoreline exhibits oscillatory behavior when the wind calms down and the resulting problem is referred to as wind set-down relaxation. We use an existing hodograph-type transformation that was introduced to solve the nonlinear shallow-water wave equations analytically for long wave propagation and obtain an explicit-transform analytical solution for wind set-down. For the wind set-down relaxation, the nonlinear shallow-water wave equations are solved… More >

H. Lin, S.N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.2, pp. 117-142, 2001, DOI:10.3970/cmes.2001.002.117

Abstract The truly Meshless Local Petrov-Galerkin (MLPG) method is extended to solve the incompressible Navier-Stokes equations. The local weak form is modified in a very careful way so as to ovecome the so-called Babus^~ka-Brezzi conditions. In addition, The upwinding scheme as developed in Lin and Atluri (2000a) and Lin and Atluri (2000b) is used to stabilize the convection operator in the streamline direction. Numerical results for benchmark problems show that the MLPG method is very promising to solve the convection dominated fluid mechanics problems. More >

H. Lin, S.N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 45-60, 2000, DOI:10.3970/cmes.2000.001.205

Abstract Due to the very general nature of the Meshless Local Petrov-Galerkin (MLPG) method, it is very easy and natural to introduce the upwinding concept (even in multi-dimensional cases) in the MLPG method, in order to deal with convection-dominated flows. In this paper, several upwinding schemes are proposed, and applied to solve steady convection-diffusion problems, in one and two dimensions. Even for very high Peclet number flows, the MLPG method, with upwinding, gives very good results. It shows that the MLPG method is very promising to solve the convection-dominated flow problems, and fluid mechanics problems. More >