scholarly journals NUMERICAL INVESTIGATION OF THE INFLUENCE OF SURFACE ROUGHNESS ON CONVECTIVE HEAT TRANSFER AT AIRFOIL ICING PROCESS

2018 ◽  
Vol 40 (2) ◽  
pp. 65-71
Author(s):  
A. A. Prykhodko ◽  
S. V. Alekseyenko
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Stokes Equations ◽  
Rough Wall ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Differential Model ◽  
The One

The technique of the processes of investigating of convective heat transfer determining in the problems of icing of aerodynamic surfaces on the basis of the solution of the Reynolds-averaged Navier- Stokes equations and the one-parameter Spalart-Allmaras turbulence differential model with correction for a rough wall is presented. A methodology that allowed to simulate airfoils icing processes taking into account the ice surface roughness is presented. For the description of the external air-droplet flow a model of interpenetrating media was used. For the description of the ice growing process the method of surface control volumes using the methodology of determining the convective heat transfer based on the solution of the Navier-Stokes equations and the one-parameter differential Spalart-Allmaras turbulence model with a correction for a rough wall were used. Verification was performed by comparing the calculations results with the data obtained with the help of known semiempirical relationships. The proposed approach, unlike existing methods, will allow us to begin solving problems in a three-dimensional statement, with a rather complex geometry, in the presence of transonic regions in the airflow, and also to determine the aerodynamic characteristics of streamlined bodies with rough ice accretions. References 15, figures 3.

scholarly journals On Linear and Non-Linear Approximation In the Theory of Convective Heat Transfer

2021 ◽  
pp. 44-51
Author(s):  
M. Y. Davidzon
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Stokes Equations ◽  
Linear Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Linear System Of Equations ◽  
Non Linear ◽  
Non Linear System

A system of linear equations that is currently widely used to describe convective heat transfer does not seem to be able to explain some experimental facts. One of the reasons for this may lie in using Newton’s and Fourier’s linear laws when deriving energy and Navier-Stokes equations. Replacing linear equations with nonlinear ones, as well as using an expression for surface heat flux density that is based on laws of physics instead of expressions called ‘cooling laws,’ would allow to solve a wider range of problems, and also would better agree with the experimental data. The use of proposed non-linear system of equations would also permit engineers in chemical, textile, defense, power, and other industries to design more economical and smaller-sized heat exchange devices.

Convective Heat Transfer in Turbulent Flow Near a Gap

2006 ◽  
Vol 128 (7) ◽  
pp. 701-708 ◽  
Author(s):  
D. Chang ◽  
S. Tavoularis
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Large Scale ◽  
Stokes Equations ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vortical Structures

Convective heat transfer in a rectangular duct containing a heated rod forming a narrow gap with a plane wall has been simulated by solving the unsteady Reynolds-averaged Navier-Stokes equations with a Reynolds stress model. Of particular interest is the role of quasi-periodic coherent structures in transporting fluid and heat across the gap region. It is shown that the local instantaneous velocity and temperature vary widely because of large-scale transport by coherent vortical structures forming in pairs on either side of the rod.

Mixed Convective Heat Transfer From Rotating Spheres

1998 ◽  
Author(s):  
Ali Heydari ◽  
Bahar Firoozabadi ◽  
Hamid Fazelli
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Transfer Coefficients ◽  
Navier Stokes Equations ◽  
Flow And Heat Transfer ◽  
Layer Flow

Abstract This paper presents an analysis of flow and heat transfer over a rotating axsisymmetric body of revolution in a mixed convective heat transfer along with surface conditions of heating or cooling as well as surface transpriation. Boundary-layer approximation reduces the elliptic Navier-Stokes equations to parabolic equations, where the Keller-Cebeci method of finite-difference solution is used to solve the resulting system of partial-differential equations. Comparison of the calculated values of the velocity and temperature profiles as well as the shear and the heat transfer coefficients at the surface for the case of a sphere with the available literature data indicate the model well predicts the boundary-layer flow and heat transfer over a rotating axsisymmetric body.

Electric Field Effects on Natural Convection in Enclosures

1986 ◽  
Vol 108 (4) ◽  
pp. 749-754 ◽  
Author(s):  
D. A. Nelson ◽  
E. J. Shaughnessy
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Stokes Equations ◽  
Experimental Studies ◽  
Navier Stokes ◽  
First Order Theory

The enhancement of convective heat transfer by an electric field is but one aspect of the complex thermoelectric phenomena which arise from the interaction of fluid dynamic and electric fields. Our current knowledge of this area is limited to a very few experimental studies. There has been no formal analysis of the basic coupling modes of the Navier–Stokes and Maxwell equations which are developed in the absence of any appreciable magnetic fields. Convective flows in enclosures are particularly sensitive because the limited fluid volumes, recirculation, and generally low velocities allow the relatively weak electric body force to exert a significant influence. In this work, the modes by which the Navier–Stokes equations are coupled to Maxwell’s equations of electrodynamics are reviewed. The conditions governing the most significant coupling modes (Coulombic forces, Joule heating, permittivity gradients) are then derived within the context of a first-order theory of electrohydrodynamics. Situations in which these couplings may have a profound effect on the convective heat transfer rate are postulated. The result is an organized framework for controlling the heat transfer rate in enclosures.

scholarly journals Efficient Simulations of Large Scale Convective Heat Transfer Problems

2021 ◽  
Vol 22 (4) ◽  
Author(s):  
Damian Goik ◽  
Krzysztof Banaś ◽  
Jan Bielański ◽  
Kazimierz Chłoń
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Large Scale ◽  
Stokes Equations ◽  
Parallel Implementation ◽  
Navier Stokes ◽  
Flow Equations ◽  
Transfer Problems

We describe an approach for efficient solution of large scale convective heat transfer problems, formulated as coupled unsteady heat conduction and incompressible fluid flow equations. The original problem is discretized in time using classical implicit methods, while stabilized finite elements are used for space discretization. The algorithm employed for the discretization of the fluid flow problem uses Picard's iterations to solve the arising nonlinear equations. Both problems, heat transfer and Navier-Stokes quations, give rise to large sparse systems of linear equations. The systems are solved using iterative GMRES solver with suitable preconditioning. For the incompressible flow equations we employ a special preconditioner based on algebraic multigrid (AMG) technique. The paper presents algorithmic and implementation details of the solution procedure, which is suitably tuned, especially for ill conditioned systems arising from discretizations of incompressible Navier-Stokes equations. We describe parallel implementation of the solver using MPI and elements of PETSC library. The scalability of the solver is favourably compared with other methods such as direct solvers and standard GMRES method with ILU preconditioning.  

Numerical Computation of Roughness Effects on Heat Transfer and Hydrodynamic Characteristics in Microchannels

2006 ◽  
Author(s):  
Heming Yun ◽  
Lin Cheng ◽  
Liqiu Wang ◽  
Binjian Chen
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Roughness Effects ◽  
Navier Stokes Equations ◽  
Experimental Heat ◽  
Macro Scale

In the present paper we focus our attention on the analysis of surface roughness effects. In the process of numerical simulation, a finite-volume method was used to solve the three-dimensional Navier-Stokes equations and energy equation. In turbulent region, wall-function was used to solve the temperature and velocity of coolant in the area near the wall. In all computational regions, the fluid-solid Conjugate heat transfer is used to solve the microchannel heat transfer problems. In conclusion the effect of surface roughness on heat transfer and pressure drop can not be neglected. And one should be very careful in ascribing the roughness effect to the discrepancies between experimental heat transfer and the prediction for standard macro scale channels.

Three-dimensional combined radiation-magnetoconvection of low electrically conductive dielectric oxide melt

2019 ◽  
Vol 29 (10) ◽  
pp. 3611-3637 ◽  
Author(s):  
Abdullah A.A.A. Al-Rashed ◽  
Lioua Kolsi ◽  
Mohammed A. Tashkandi ◽  
Emad Hasani Malekshah ◽  
Ali J. Chamkha ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Electrically Conductive ◽  
Content Type ◽  
Oxide Melt

Purpose The purpose of this paper is to investigate the coupled effect of magnetic field and radiation on convective heat transfer of low electrically conductive dielectric oxide melt. Design/methodology/approach The 3D Navier–Stokes equations are formulated using the vector potential-vorticity formulation and solved using the finite volume method (FVM). The radiative heat transfer equation is discretized using the FTnFVM method. A code was written using FORTRAN language. Findings The obtained numerical results are focused on the effect of the different parameters on the heat transfer and the flow structure with a special interest on the 3D transvers flow. It is found that the flow is developing in inner spirals and the magnetic field intensifies this 3D character. The radiation acts mainly at the core of the enclosure and causes the apparition of the merging phenomenon near the front and back walls. Originality/value The effect of magnetic field on convective heat transfer of highly electrically conductive fluids has been intensively studied. Reciprocally, the case of a fluid with low electrical conductivity is not so much investigated, especially when it is coupled with the effect of radiation. These two effects are studied in this paper for the case of a low-conductive LiNbO3 oxide melt.

scholarly journals A Code for Simulating Heat Transfer in Turbulent Channel Flow

Mathematics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 756
Author(s):  
Federico Lluesma-Rodríguez ◽  
Francisco Álcantara-Ávila ◽  
María Jezabel Pérez-Quiles ◽  
Sergio Hoyas
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulent Channel Flow ◽  
Passive Scalar ◽  
Direct Numerical Simulations ◽  
Time Dependent ◽  
Navier Stokes ◽  
Thermal Flow ◽  
Navier Stokes Equations

One numerical method was designed to solve the time-dependent, three-dimensional, incompressible Navier–Stokes equations in turbulent thermal channel flows. Its originality lies in the use of several well-known methods to discretize the problem and its parallel nature. Vorticy-Laplacian of velocity formulation has been used, so pressure has been removed from the system. Heat is modeled as a passive scalar. Any other quantity modeled as passive scalar can be very easily studied, including several of them at the same time. These methods have been successfully used for extensive direct numerical simulations of passive thermal flow for several boundary conditions.

Fast forced liquid film spreading on a substrate: flow, heat transfer and phase transition

2010 ◽  
Vol 656 ◽  
pp. 189-204 ◽  
Author(s):  
ILIA V. ROISMAN
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Stokes Equations ◽  
Substrate Surface ◽  
Reynolds Numbers ◽  
Drop Impact ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Theoretical Predictions ◽  
Viscous Drop

This theoretical study is devoted to description of fluid flow and heat transfer in a spreading viscous drop with phase transition. A similarity solution for the combined full Navier–Stokes equations and energy equation for the expanding lamella generated by drop impact is obtained for a general case of oblique drop impact with high Weber and Reynolds numbers. The theory is applicable to the analysis of the phenomena of drop solidification, target melting and film boiling. The theoretical predictions for the contact temperature at the substrate surface agree well with the existing experimental data.

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