Study of the Dynamic and Thermal Behaviors of an Air Flow in a T-Bifurcation

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Ali Riahi ◽  
Julien Pelle ◽  
Lilia Chouchene ◽  
Souad Harmand ◽  
Sadok Ben Jabrallah
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Initial Conditions ◽  
Research Work ◽  
Internal Surface ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Flow Ratio ◽  
Sst Turbulence Model ◽  
Dynamics Simulations

This paper presents a numerical and experimental study of a turbulent flow of air in a T-bifurcation. This configuration corresponds to a stator containing radial vents oriented vertically to the rotor–stator air gap in electrical machines. Our analysis focuses on the local convective heat transfer over the internal surface of the vents under a turbulent mass flow rate. To model the cooling installation in this region, computational fluid dynamics simulations and an experiment using particle image velocimetry (PIV) are performed. The resulting flow generally produces recirculation zones in various channels. The effect of the flow ratio and diameter of the bifurcation on the dynamic and thermal behavior of the flow is also examined. In this study, we apply a numerical approach based on the k–ω shear stress transport (SST) turbulence model (using the commercial software, “comsolmultiphysics”) to numerically solve the Navier–Stokes equations and energy equation of the system under consideration. We describe the different hypotheses necessary to formulate the equations governing the problem, initial conditions, and boundary condition. The velocity in the bifurcation calculated using the simulation is compared with that obtained by the experiment and it reveals a good agreement. The effect of the branch diameter of the bifurcation and flow ratio on the heat transfer is specifically analyzed in this research work.

Modeling and analysis of solar air channels with attachments of different shapes

2019 ◽  
Vol 29 (5) ◽  
pp. 1815-1845 ◽  
Author(s):  
Younes Menni ◽  
Ahmed Azzi ◽  
A. Chamkha
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Research Work ◽  
Convection Heat Transfer ◽  
Navier Stokes ◽  
Transfer Coefficients ◽  
Navier Stokes Equations ◽  
Content Type ◽  
Modeling And Analysis ◽  
Air Channels

Purpose This paper aims to report the results of numerical analysis of turbulent fluid flow and forced-convection heat transfer in solar air channels with baffle-type attachments of various shapes. The effect of reconfiguring baffle geometry on the local and average heat transfer coefficients and pressure drop measurements in the whole domain investigated at constant surface temperature condition along the top and bottom channels’ walls is studied by comparing 15 forms of the baffle, which are simple (flat rectangular), triangular, trapezoidal, cascaded rectangular-triangular, diamond, arc, corrugated, +, S, V, double V (or W), Z, T, G and epsilon (or e)-shaped, with the Reynolds number changing from 12,000 to 32,000. Design/methodology/approach The baffled channel flow model is controlled by the Reynolds-averaged Navier–Stokes equations, besides the k-epsilon (or k-e) turbulence model and the energy equation. The finite volume method, by means of commercial computational fluid dynamics software FLUENT is used in this research work. Findings Over the range investigated, the Z-shaped baffle gives a higher thermal enhancement factor than with simple, triangular, trapezoidal, cascaded rectangular-triangular, diamond, arc, corrugated, +, S, V, W, T, G and e-shaped baffles by about 3.569-20.809; 3.696-20.127; 3.916-20.498; 1.834-12.154; 1.758-12.107; 7.272-23.333; 6.509-22.965; 8.917-26.463; 8.257-23.759; 5.513-18.960; 8.331-27.016; 7.520-26.592; 6.452-24.324; and 0.637-17.139 per cent, respectively. Thus, the baffle of Z-geometry is considered as the best modern model of obstacles to significantly improve the dynamic and thermal performance of the turbulent airflow within the solar channel. Originality/value This analysis reports an interesting strategy to enhance thermal transfer in solar air channels by use of attachments with various shapes

Numerical Computation of Fluid Flow and Heat Transfer in Microchannels

2005 ◽  
Author(s):  
Ningli Liu ◽  
Rene Chevray ◽  
Gerald A. Domoto ◽  
Elias Panides
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Energy Equation ◽  
Stokes Equations ◽  
Numerical Approach ◽  
Time Dependent ◽  
Navier Stokes ◽  
Temperature Profiles ◽  
Navier Stokes Equations ◽  
Flow And Heat Transfer

A finite difference numerical approach for solving slightly compressible, time-dependent, viscous laminar flow is presented in this study. Simplified system of Navier-Stokes equations and energy equation are employed in the study in order to perform more efficient numerical calculations. Fluid flow and heat transfer phenomena in two dimensional microchannels are illustrated numerically in this paper. This numerical approach provides a complete numerical simulation of the development of the fluid flow and the temperature profiles through multi-dimensional microchannels.

Simulation of the Dynamic Response of a Sloshing Liquid to Horizontal Movements of the Tank

2014 ◽  
Author(s):  
Anaïs Brandely ◽  
Jean-Sébastien Schotté ◽  
Emmanuel Lefrançois ◽  
Benjamin Hagege ◽  
Roger Ohayon
Keyword(s):  
Free Surface ◽  
Dynamic Response ◽  
Stokes Equations ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Phase Flow ◽  
Viscous Effects ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Sst Turbulence Model

The dynamic response of a sloshing liquid to horizontal movements of a rectangular tank with a small amplitude is studied here by a numerical approach issued from a commercial CFD code. This numerical model solves Navier-Stokes equations considering a two-phase flow. In order to check the localized turbulence effects on the global fluid behavior, the averaged Navier-Stokes equations are solved with laminar option and with a k–ω SST turbulence model. The Volume Of Fluid (VOF) method is adopted to track the distorted free surface. The previous CFD solution is compared with a linearized approach based on the potential flow theory taking into account viscous effects. This model considers a single phase flow and is much less expensive in CPU time, especially thanks to the use of modal projection techniques. Both models are validated and applied on several cases. Free surface sloshing elevation and global forces, obtained for various excitation amplitudes and frequencies, are compared. Perfect and viscous liquids are considered.

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.

Computational Characterization of Passive Fluid Mixing in Microfluidics

Volume 3 ◽  
2004 ◽  
Author(s):  
Erik D. Svensson
Keyword(s):  
Stokes Equations ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Fluid Mixing ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Fluid Systems ◽  
Sensitive Dependence ◽  
Microfluidic Mixers

In this work we computationally characterize fluid mixing in a number of passive microfluidic mixers. Generally, in order to systematically study and characterize mixing in realistic fluid systems we (1) compute the fluid flow in the systems by solving the stationary three-dimensional Navier-Stokes equations or Stokes equations with a finite element method, and (2) compute various measures indicating the degree of mixing based on concepts from dynamical systems theory, i.e., the sensitive dependence on initial conditions and mixing variance.

Turbine Airfoil Heat Transfer Predictions Using CFD

2005 ◽  
Author(s):  
Anil K. Tolpadi ◽  
James A. Tallman ◽  
Lamyaa El-Gabry
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulence Modeling ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Design System ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Airfoils ◽  
Typical Design

Conventional heat transfer design methods for turbine airfoils use 2-D boundary layer codes (BLC) combined with empiricism. While such methods may be applicable in the mid span of an airfoil, they would not be very accurate near the end-walls and airfoil tip where the flow is very three-dimensional (3-D) and complex. In order to obtain accurate heat transfer predictions along the entire span of a turbine airfoil, 3-D computational fluid dynamics (CFD) must be used. This paper describes the development of a CFD based design system to make heat transfer predictions. A 3-D, compressible, Reynolds-averaged Navier-Stokes CFD solver with k-ω turbulence modeling was used. A wall integration approach was used for boundary layer prediction. First, the numerical approach was validated against a series of fundamental airfoil cases with available data. The comparisons were very favorable. Subsequently, it was applied to a real engine airfoil at typical design conditions. A discussion of the features of the airfoil heat transfer distribution is included.

Measurement and Calculation of Nozzle Guide Vane End Wall Heat Transfer

1998 ◽  
Author(s):  
Neil W. Harvey ◽  
Martin G. Rose ◽  
John Coupland ◽  
Terry Jones
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Guide Vane ◽  
Correction Method ◽  
Navier Stokes ◽  
Design Data ◽  
Navier Stokes Equations ◽  
Wall Functions ◽  
Transfer Rates ◽  
Nozzle Guide

A 3-D steady viscous finite volume pressure correction method for the solution of the Reynolds averaged Navier-Stokes equations has been used to calculate the heat transfer rates on the end walls of a modern High Pressure Turbine first stage stator. Surface heat transfer rates have been calculated at three conditions and compared with measurements made on a model of the vane tested in annular cascade in the Isentropic Light Piston Facility at DERA, Pyestock. The NGV Mach numbers, Reynolds numbers and geometry are fully representative of engine conditions. Design condition data has previously been presented by Harvey and Jones (1990). Off-design data is presented here for the first time. In the areas of highest heat transfer the calculated heat transfer rates are shown to be within 20% of the measured values at all three conditions. Particular emphasis is placed on the use of wall functions in the calculations with which relatively coarse grids (of around 140,000 nodes) can be used to keep computational run times sufficiently low for engine design purposes.

scholarly journals PARALLEL COMPUTATIONS IN STUDIES OF DEPENDENCE OF GAS DYNAMIC PARAMETERS OF UPWARD SWIRLING FLOW OF GAS ON BLOWING VELOCITY

2016 ◽  
pp. 92-97
Author(s):  
R. E. Volkov ◽  
A. G. Obukhov
Keyword(s):  
Stokes Equations ◽  
Swirling Flow ◽  
Initial Conditions ◽  
Exact Analytical Solution ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Heat Conducting ◽  
Computational Domain ◽  
Navier Stokes Equations ◽  
Gas Dynamic

The rectangular parallelepiped explicit difference schemes for the numerical solution of the complete built system of Navier-Stokes equations. These solutions describe the three-dimensional flow of a compressible viscous heat-conducting gas in a rising swirling flows, provided the forces of gravity and Coriolis. This assumes constancy of the coefficient of viscosity and thermal conductivity. The initial conditions are the features that are the exact analytical solution of the complete Navier-Stokes equations. Propose specific boundary conditions under which the upward flow of gas is modeled by blowing through the square hole in the upper surface of the computational domain. A variant of parallelization algorithm for calculating gas dynamic and energy characteristics. The results of calculations of gasdynamic parameters dependency on the speed of the vertical blowing by the time the flow of a steady state flow.

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