G.S. Li¹, D. Yao², Y.Z. Wang³, H.Y. Jiang²

CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.1, pp. 53-72, 2009, DOI:10.3970/cmes.2009.051.053

Abstract In this paper, an undisturbed soil-column infiltrating experiment is investigated, and a mathematical model describing multi-components solutes transport behaviors in the column is put forward by combing hydro-chemical analysis with advection dispersion mechanisms, which is a group of advection-dispersion-reaction partial differential equations. Since the model involving six reaction coefficients which can not be obtained directly, an optimal perturbation regularization algorithm of determining these parameters is performed, and numerical simulations under different conditions are carried out. Furthermore, the inversion algorithm is applied to solve the real inverse problem by utilizing the measured breakthrough data. The reconstruction data basically coincide with the… More >

J.M.C.Pereira¹, N.A.R.Maia¹, J.C.F.Pereira¹

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 113-142, 2009, DOI:10.3970/cmes.2009.049.113

Abstract We present a 2D incompressible Navier-Stokes numerical simulation of a virtual model of an elliptic, or flat plate, foil in hovering flight configuration. Computations obtained with a general purpose solver were validated against reference data on forward flapping flight, normal or dragonfly hovering. The moving mesh technique allows airfoil translation and angular mesh movement accompaining the airfoil stroke motion. Close to the ground the mesh deforms to occupy the narrow computational domain formed between the airfoil and the ground. Computations have been carried out for some parameters, including the distances h between the foil center and the surface, h/c =… More >

Tao Cui¹, Wenhao Liao¹ and Daren Yu ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.45, No.3, pp. 273-294, 2009, DOI:10.3970/cmes.2009.045.273

Abstract Aerodynamic hysteresis is of practical importance for the flying airfoils. Motivated by the problem of global description on the hysteresis behaviors, this paper proposes a topological approach to analyze and model the hysteresis behaviors exhibited in the airfoil flow from a viewpoint of dynamic system theory. The approach is based on the topological invariant rules of singular points under topological mapping. It is able to theoretically explain such discontinuous hysteresis phenomena, and make consistent and accurate predictions of the hysteresis behaviors in the airfoil flow. The model results have shown that the present model is in good agreement with the… More >

Liviu Marin¹, Henry Power¹, Richard W. Bowtell², Clemente Cobos Sanchez², Adib A. Becker¹, Paul Glover²，Arthur Jones¹

CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.3, pp. 149-174, 2008, DOI:10.3970/cmes.2008.023.149

Abstract We investigate the reconstruction of a divergence-free surface current distribution from knowledge of the magnetic flux density in a prescribed region of interest in the framework of static electromagnetism. This inverse problem is motivated by the design of gradient coils for use in magnetic resonance imaging (MRI) and is formulated using its corresponding integral representation according to potential theory. A novel boundary element method (BEM) which employs linear interpolation on quadratic surfaces and also satisfies the continuity equation for the current density, i.e. a divergence-free BEM, is presented. Since the discretised BEM system is ill-posed and hence the associated least-squares… More >

Ehsan Jabbari¹, Behrouz Gatmiri^2,3

CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.1, pp. 31-44, 2007, DOI:10.3970/cmes.2007.018.031

Abstract In this paper after a discussion about the evolution of the unsaturated soils' governing differential equations and a brief history of the Green's functions for porous media, the governing equations, i.e., the mathematical model in the presence of heat effects are presented and simplified so as the derivation of the associated Green's functions be in the realm of possibility. The thermal two- and three-dimensional, full- and half-space Green's functions for unsaturated porous media, although in a relatively simplified form, are being introduced for the first time, following the previous works of the authors. The derived Green's functions have been demonstrated… More >

Rosario M. A. Marretta¹, Giovanni Lombardi², Roberto Antinoro¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.1, pp. 73-84, 2003, DOI:10.3970/cmes.2003.004.073

Abstract An approach based on Lighthill's transpiration velocity is explored and proposed for a new design criterion for airfoils in unsteady and viscous flows. This criterion confines its methodologies to the close proximity of the laminar and turbulent boundary layer and it shows good efficiency in predicting and calculating the wake evolution regions in a wide range of operating unsteady parameters. Also, the criterion is capable of predicting low Mach number, attached flow-fields as accurately as the full Navier-Stokes solutions when the massive flow separation is avoided. The agreement of the present results with those empirically and theoretically determined is very… More >

Ori Levin, Wei Shyy¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.4, pp. 523-536, 2001, DOI:10.3970/cmes.2001.002.523

Abstract Typical low Reynolds number airfoils suffer from reduced lift-to-drag ratio and are prone to flow separation. In order to improve the aerodynamic performance of such airfoils in an unsteady freestream, the concept of passive control is investigated. In this study, a membrane with varying thickness distribution and mechanical properties is attached on the upper surface of a modified Clark-Y airfoil and is free to move upwards and downwards in response to the pressure difference across it. The response surface method is employed to investigate the individual and collective effects of the membrane's prestress, elastic modulus, and thickness distribution on aerodynamic… More >

Daoming Shen¹, Hua Si^1,*, Jinhong Xia¹, Shunqun Li²

FDMP-Fluid Dynamics & Materials Processing, Vol.15, No.1, pp. 63-76, 2019, DOI:10.32604/fdmp.2019.04799

Abstract The correct determination of thermal parameters, such as thermal conductivity and specific heat of soil during freezing, is the most important and basic problem for the construction of an appropriate freezing method. In this study, a calculation model of three stages of soil temperature was established. At the unfrozen and frozen stages, the specific temperatures of dry soil, water, and ice are known. According to the principle of superposition, a calculation model of unfrozen and frozen soils can be established. Informed by a laboratory experiment, the latent heat of the adjacent zone was calculated for the freezing stage based on… More >

Hadil Abu Khalifeh¹, Hadi Belhaj²

FDMP-Fluid Dynamics & Materials Processing, Vol.12, No.3, pp. 124-135, 2016, DOI:10.3970/fdmp.2016.012.124

Abstract In this work, asphaltenes precipitation and deposition induced by applying an electric field to Abu Dhabi crude oil sample were studied. The asphaltic particle electrical charge and asphaltic deposits mass at different operating conditions were determined. Direct current (DC) was applied between two graphite electrodes dipped in crude oil/synthetic formation water mixture of 240K ppm salinity. Three current densities of 10, 20, and 30 A/m2 were applied. Deposits were collected on the electrodes surfaces and their mass was recorded using low capacity load cells (up to 50g). Anodic and cathodic deposits were observed at different operating conditions. The results revealed… More >

Hameed Muhamad¹, Simant Upreti ², Ali Lohi³, Huu Doan⁴

FDMP-Fluid Dynamics & Materials Processing, Vol.12, No.3, pp. 111-123, 2016, DOI:10.3970/fdmp.2016.012.111

Abstract Heavy Oil is an up and coming energy resource that is aggressively being sought after as the world’s energy demand increases. As technology continues to improve, this once costly energy source is quickly becoming a more viable alternative. Vapor extraction (Vapex) process is an emerging technology for viscous oil recovery that has gained much attention in the oil industry. The vapor extraction of heavy oil system is presented to describe experimental setups and procedures used to perform different experiments of vape extraction process. The generated experimental data were used to calculate the live oil maximum interfacial solvent concentration as function… More >