Yong Guan¹, Wanling Hu^{1, 2, *}, Yun Zhang¹, Kewei Song^{2, 3}, Liangbi Wang^{2, 3}

CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 237-256, 2020, DOI:10.32604/cmes.2020.09141

Abstract The application of vortex generators in tube-finned heat exchangers is very universal. The vortex generators can generate secondary flow, and as we all know secondary flow can obviously strengthen heat transfer. To use vortex generators much more efficiently in the circle tube-finned heat exchangers, the intensity correlation study between secondary flow and heat transfer is needed. 22 different structures of circle tubefinned heat exchangers were numerically studied, including the plain fin cases and the cases with vortex generators. In addition, the influence of fin spacing, transverse and longitudinal tube pitch, heights and attack angle of vortex generators, positions of vortex… More >

Primož Kocutar^{1, *}, Jure Ravnik¹, Leopold Škerget¹

CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 1-22, 2020, DOI:10.32604/cmes.2020.08728

Abstract In this paper, we develop and test a unified hybrid LES/URANS turbulence model with two different Large Eddy Simulation (LES) turbulence models. The numerical algorithm is based on the Boundary Element Method. In the existing hybrid LES/URANS turbulence model we implemented a new Smagorinsky LES turbulence model. The hybrid LES/URANS turbulence model is unified, which means that the LES/URANS interface is changed dynamically during simulation using a physical quantity. In order to define the interface between LES and unsteady Reynolds Averaged Navier Stokes (URANS) zones during the simulation, we use the Reynolds number based on turbulent kinetic energy as a… More >

Suvash C. Saha^1,*, Ali M. Sefidan², Atta Sojoudi³

Energy Engineering, Vol.117, No.1, pp. 1-17, 2020, DOI:10.32604/EE.2020.010418

Abstract Free convection inside an attic enclosure in which sinusoidal heat flux applied on the inclined walls and a constant temperature applied on the base wall has been investigated numerically to demonstrate the primary flow characteristics and heat transfer within the attic enclosure over daily routine cycles. To solve the governing equations, the finite volume technique has been utilized. After performing the grid independency and time step size tests, the roles of Rayleigh number (Ra) and the attic aspect ratio (AR) on the unsteady flow structure and heat transfer phenomenon are explained for a constant Prandtl number (0.72) for the air.… More >

Zaiguo Fu^{1, *}, Huanhuan Gao¹, Zhuoxiong Zeng¹, Jiang Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.122, No.3, pp. 805-830, 2020, DOI:10.32604/cmes.2020.08825

Abstract In order to comprehensively evaluate the flow and heat transfer performance of a large-size annular combustion chamber of a heavy-duty gas turbine, we carried out numerical computation and analyses on the velocity, temperature and pressure fields in the chamber with double swirlers. The mathematical model of the coupling combustion, gas flow, and heat transfer process was established. The influences of the inlet swirling strength, fuel-air ratio and temperature of the premixed gas on the multi-field characteristics and synergy were investigated on the basis of field synergy theory. The results showed that the central recirculation zone induced by the inlet swirling… More >

Shuo Yang¹, Yuanhai Li^{1, 2, ∗}, Xiaojie Tang^{1, 2}, Jinshan Liu^{1, 2}

CMES-Computer Modeling in Engineering & Sciences, Vol.122, No.2, pp. 633-659, 2020, DOI:10.32604/cmes.2020.07919

Abstract The deformation and damage evolution of sandstone after heat treatment greatly influence the efficient and safe development of deep geothermal energy extraction. To investigate this issue, laboratory confined compression tests and numerical simulations were conducted on pre-holed sandstone specimens after heat treatment. The laboratory test results show that the failure modes are closely related to the heat treatment temperature, with increasing treatment temperature, the failure modes change from mixed and shear modes to a splitting mode. The cracks always initiate from the sidewalls of the hole and then propagate. The failure process inside the hole proceeds as follows: calm period,… More >

Weihua Fang¹, Zhilin An², Tiantang Yu^{2, *}, Tinh Quoc Bui^{3, 4, *}

CMC-Computers, Materials & Continua, Vol.62, No.2, pp. 929-962, 2020, DOI:10.32604/cmc.2020.05022

Abstract Numerical analysis of unsteady heat transfer problems with complex geometries by the isogeometric boundary element method (IGABEM) is presented. The IGABEM possesses many desirable merits and features, for instance, (a) exactly represented arbitrarily complex geometries, and higher-order continuity due to nonuniform rational B-splines (NURBS) shape functions; (b) using NURBS for both field approximation and geometric description; (c) directly utilizing geometry data from computer-aided design (CAD); and (d) only boundary discretization. The formulation of IGABEM for unsteady heat transfer is derived. The domain discretization in terms of IGABEM for unsteady heat transfer is required as that in traditional BEM. The internal… More >

M. H. Ghasemi¹, S. Hoseinzadeh^{2, 3, *}, P. S. Heyns², D. N. Wilke²

CMES-Computer Modeling in Engineering & Sciences, Vol.122, No.1, pp. 399-414, 2020, DOI:10.32604/cmes.2020.07827

Abstract In this study, transient non-Fourier heat transfer in a solid cylinder is analytically solved based on dual-phase-lag for constant axial heat flux condition. Governing equations for the model are expressed in two-dimensional cylindrical coordinates; the equations are nondimensionalized and exact solution for the equations is presented by using the separation of variable method. Results showed that the dual-phase-lag model requires less time to meet the steady temperature compared with single-phase-lag model. On the contrary, thermal wave diffusion speed for the dual-phase-lag model is greater than the single-phase-lag model. Also the effect of relaxation time in dual-phase-lag model has been taken… More >

Ivan V. Kazachkov^1,2,*

FDMP-Fluid Dynamics & Materials Processing, Vol.15, No.5, pp. 491-507, 2019, DOI:10.32604/fdmp.2019.06477

Abstract Non-classical subjects relating to the dynamics of jet and film flow and related heat transfer processes are considered. These problems, which are relevant to several technological applications, cannot completely be addressed in the frame of the canonical Navier-Stokes equations. The first example deals with the formation of a film flow as a result of the hydraulic shock of a vertical jet impinging on a horizontal plane. The effective thickness of the film resulting from the hydraulic shock is much less than the value obtained using the conventional approach (relying on the assumption of smooth flow), while the corresponding speed is… More >

S . Samantha Kumari^1,*, G. Sankara Sekhar Raju²

FDMP-Fluid Dynamics & Materials Processing, Vol.15, No.5, pp. 471-489, 2019, DOI:10.32604/fdmp.2019.04222

Abstract This paper investigates the chemical reaction and thermal radiation effects on unsteady MHD free convective flow past a vertical porous plate in the presence of heat absorption/generation. The novelty of present investigation is that the temperature and concentration of the plate are span wise cosinusoidally unsteady with time. The second order perturbation technique is employed to study the non-linear partial differential equations which govern the fluid flow. The effects of magnetic parameter, radiation, Eckert number, Schmidt number and chemical reaction parameters on velocity, temperature and concentration distributions as well as skin friction coefficients, the rate of heat transfer and the… More >

Mohamed Abd El-Aziz^{1, 2}, A. M. Aly^{1, 3, *}

CMC-Computers, Materials & Continua, Vol.62, No.1, pp. 37-59, 2020, DOI:10.32604/cmc.2020.08488

Abstract In the present study, the effects of the magnetic field on the entropy generation during fluid flow and heat transfer of a Sisko-fluid over an exponentially stretching surface are considered. The similarity transformations are used to transfer the governing partial differential equations into a set of nonlinear-coupled ordinary differential equations. Runge-Kutta-Fehlberg method is used to solve the governing problem. The effects of magnetic field parameter M, local slip parameter λ, generalized Biot number γ, Sisko fluid material parameter A, Eckert number Ec, Prandtl number Pr and Brinkman number Br at two values of power law index on the velocity, temperature,… More >