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Article
Publication date: 1 February 1992

K.A. ELRAIS, W. ECKERLE, G. AHMADI and A.H. ERASLAN

A three‐dimensional, two‐phase computational model for simulating boiling‐enhanced mixed convection in free‐surface flows is presented. The associated constitutive models for the…

Abstract

A three‐dimensional, two‐phase computational model for simulating boiling‐enhanced mixed convection in free‐surface flows is presented. The associated constitutive models for the thermophysical and transport properties are described. A computational model incorporating the discrete‐element analysis was used to simulate the multi‐dimensional, two‐phase flow around a heated chip in a test tank filled with Freon‐(R113). Two and three‐dimensional simulations of both natural convection and nucleate boiling heat transfer regimes are presented. The velocity field, the temperature distribution, and the vapour concentration profiles are evaluated and discussed. The simulated heat fluxes are compared with the available experimental data. While the heat fluxes from the two‐dimensional simulation agree with the fluxes calculated for the three‐dimensional case, the flow in the tank is essentially three‐dimensional. The results show that there are secondary flows which cannot be captured by a two‐dimensional model. The heat flux in the boiling heat transfer regime is only about ten times larger than that in the natural convection regime due to the small vapour concentration in tank.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 2 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 6 October 2023

Aoxiang Qiu, Weimin Sang, Feng Zhou and Dong Li

The paper aims to expand the scope of application of the lattice Boltzmann method (LBM), especially in the field of aircraft engineering. The traditional LBM is usually applied…

Abstract

Purpose

The paper aims to expand the scope of application of the lattice Boltzmann method (LBM), especially in the field of aircraft engineering. The traditional LBM is usually applied to incompressible flows at a low Reynolds number, which is not sufficient to satisfy the needs of aircraft engineering. Devoted to tackling the defect, the paper proposes a developed LBM combining the subgrid model and the multiple relaxation time (MRT) approach. A multilayer adaptive Cartesian grid method to improve the computing efficiency of the traditional LBM is also employed.

Design/methodology/approach

The subgrid model and the multilayer adaptive Cartesian grid are introduced into MRT-LBM for simulations of incompressible flows at a high Reynolds number. Validated by several typical flow simulations, the numerical methods in this paper can efficiently study the flows under high Reynolds numbers.

Findings

Some numerical simulations for the lid-driven flow of cavity, flow around iced GLC305, LB606b and ONERA-M6 are completed. The paper presents the investigation results, indicating that the methods are accurate and effective for the separated flow after icing.

Originality/value

LBM is developed with the addition of the subgrid model and the MRT method. A numerical strategy is proposed using a multilayer adaptive Cartesian grid method and its treatment of boundary conditions. The paper refers to innovative algorithm developments and applications to the aircraft engineering, especially for iced wing simulations with flow separations.

Details

Engineering Computations, vol. 40 no. 9/10
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 16 December 2019

Francisco-Javier Granados-Ortiz, Joaquin Ortega-Casanova and Choi-Hong Lai

Impinging jets have been widely studied, and the addition of swirl has been found to be beneficial to heat transfer. As there is no literature on Reynolds-averaged Navier Stokes…

Abstract

Purpose

Impinging jets have been widely studied, and the addition of swirl has been found to be beneficial to heat transfer. As there is no literature on Reynolds-averaged Navier Stokes equations (RANS) nor experimental data of swirling jet flows generated by a rotating pipe, the purpose of this study is to fill such gap by providing results on the performance of this type of design.

Design/methodology/approach

As the flow has a different behaviour at different parts of the design, the same turbulent model cannot be used for the full domain. To overcome this complexity, the simulation is split into two coupled stages. This is an alternative to use the costly Reynold stress model (RSM) for the rotating pipe simulation and the SST k-ω model for the impingement.

Findings

The addition of swirl by means of a rotating pipe with a swirl intensity ranging from 0 up to 0.5 affects the velocity profiles, but has no remarkable effect on the spreading angle. The heat transfer is increased with respect to a non-swirling flow only at short nozzle-to-plate distances H/D < 6, where H is the distance and D is the diameter of the pipe. For the impinging zone, the highest average heat transfer is achieved at H/D = 5 with swirl intensity S = 0.5. This is the highest swirl studied in this work.

Research limitations/implications

High-fidelity simulations or experimental analysis may provide reliable data for higher swirl intensities, which are not covered in this work.

Practical implications

This two-step approach and the data provided is of interest to other related investigations (e.g. using arrays of jets or other surfaces than flat plates).

Originality/value

This paper is the first of its kind RANS simulation of the heat transfer from a flat plate to a swirling impinging jet flow issuing from a rotating pipe. An extensive study of these computational fluid dynamics (CFD) simulations has been carried out with the emphasis of splitting the large domain into two parts to facilitate the use of different turbulent models and periodic boundary conditions for the flow confined in the pipe.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 January 1991

T.S. LEE

Heat and fluid flow through a trapezoidal cooling chamber were studied numerically. Hot fluid is assumed inflow at some depth below the surface into one end of the chamber and…

Abstract

Heat and fluid flow through a trapezoidal cooling chamber were studied numerically. Hot fluid is assumed inflow at some depth below the surface into one end of the chamber and withdrawn at another depth from the other end. The top of the chamber is exposed to the surrounding for cooling and the remaining side‐walls are all insulated. Inflow Reynolds number Ro considered is in the range of 100 to 1000 and the inlet densimetric Froude number Fo considered is in the range of 0.5 to 50.0. Numerical experiments show that the flow and temperature fields in the flow‐through trapezoidal chamber are strong function of both Fo and Ro. The submergence ratio D/do, chamber length to depth ratio L/D and chamber wall angles are also significant in influencing the flow fields. Comparisons were also made with available experimental and prototype data.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 1 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 June 1997

Balasubramaniam Ramaswamy and Rafael Moreno

In part I uses an iterative point successive over‐relaxation (PSOR) finite difference scheme to solve the coupled unsteady Navier‐Stokes and energy equations for incompressible…

Abstract

In part I uses an iterative point successive over‐relaxation (PSOR) finite difference scheme to solve the coupled unsteady Navier‐Stokes and energy equations for incompressible, viscous and laminar flows in their primitive variable form. Presents the details concerning the derivation of the solution scheme, as well as details on its computer implementation. For validation purposes, includes the results of the two‐dimensional and three‐dimensional benchmark problem of natural convection in a cavity with differentially heated vertical walls. Benchmark computations have been performed for a Prandtl number of 0.71, and different values of the Rayleigh number ranging between 103 and 106 depending on the problem. By comparison with other approaches in the literature, the scheme has been found to be accurate even for large Rayleigh numbers.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 7 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 April 1992

SHIN FANN, WEN‐JEI YANG and S. MOCHIZUKI

A theoretical study is performed on three‐dimensional, heat transfer and fluid flow in radially rotating heated channels with steady, laminar throughflow. Consideration is given…

Abstract

A theoretical study is performed on three‐dimensional, heat transfer and fluid flow in radially rotating heated channels with steady, laminar throughflow. Consideration is given to the channel of different geometry. Both the rotational speed and throughflow rate are varied. The flow is hydrodynamically and thermally developing, with a constant wall heat flux. The velocity‐vorticity method is employed in the formulation and numerical results are obtained by means of a finite‐difference technique. The Nusselt number, friction factor, and temperature and velocity distributions are determined, and the role of the Coriolis force on the entrance‐region transport phenomena is investigated. Results are compared with the existing literature.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 2 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 8 February 2022

P.K. Ullas, Dhiman Chatterjee and S. Vengadesan

Understanding the interaction of turbulence and cavitation is an essential step towards better controlling the cavitation phenomenon. The purpose of this paper is to bring out the…

Abstract

Purpose

Understanding the interaction of turbulence and cavitation is an essential step towards better controlling the cavitation phenomenon. The purpose of this paper is to bring out the efficacy of different modelling approaches to predict turbulence and cavitation-induced phase changes.

Design/methodology/approach

This paper compares the dynamic cavitation (DCM) and Schnerr–Sauer models. Also, the effects of different modelling methods for turbulence, unsteady Reynolds-averaged Navier–Stokes (URANS) and detached eddy simulations (DES) are also brought out. Numerical predictions of internal flow through a venturi are compared with experimental results from the literature.

Findings

The improved predictive capability of cavitating structures by DCM is brought out clearly. The temporal variation of the cavity size and velocity illustrates the involvement of re-entrant jet in cavity shedding. From the vapour fraction contours and the attached cavity length, it is found that the formation of the re-entrant jet is stronger in DES results compared with that by URANS. Variation of pressure, velocity, void fraction and the mass transfer rate at cavity shedding and collapse regions are presented. Wavelet analysis is used to capture the shedding frequency and also the corresponding occurrence of features of cavity collapse.

Originality/value

Based on the performance, computational time and resource requirements, this paper shows that the combination of DES and DCM is the most suitable option for predicting turbulent-cavitating flows.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 10
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 23 November 2020

Sylwia Boroń

This paper aims to study and assess a new approach for prediction of changes of pressure during gas discharge inside the room protected by fixed gaseous extinguishing system by…

Abstract

Purpose

This paper aims to study and assess a new approach for prediction of changes of pressure during gas discharge inside the room protected by fixed gaseous extinguishing system by computational fluid dynamics (CFD) simulations.

Design/methodology/approach

The research program consisted of two stages. The first stage was dedicated to the experimental measurements of pressure changes during extinguishing gas discharge into the test chamber in a real scale (70 m3), for two relief openings that differ in their area. The next step was about performing CFD simulations forecasting pressure changes during gas discharge into the numerically represented test chamber. Estimation of the correctness and usefulness of the CFD model was based on a comparison of the CFD results with standard calculations and experimental measurements.

Findings

Numerical modelling of pressure changes during the carbon dioxide discharge was very close to the experiment. The obtained results had sufficient accuracy (in most cases relative error <15%), while the standard approach predicted pressure changes with an average relative error over 36% and did not estimate the decrease of pressure at all.

Originality/value

Conducted research confirms the viability of the new approach in modelling the pressure changes and indicates additional benefits of the numerical analyses in the determination of the fire safety of protected premises.

Details

Journal of Structural Fire Engineering, vol. 12 no. 1
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 1 February 2002

W. Song and B.Q. Li

This paper describes the finite element solution of conjugate heat transfer problems with and without the use of gap elements. Direct and iterative methods to incorporate gap…

2187

Abstract

This paper describes the finite element solution of conjugate heat transfer problems with and without the use of gap elements. Direct and iterative methods to incorporate gap elements into a general finite element program are presented, along with their advantages and disadvantages of the two gap element treatments in the framework of finite elements. The numerical performance of the iterative gap element treatment is discussed in detail in comparison with analytical solutions for both 2‐ and 3‐D gap conductance problems. Numerical tests show that the number of iterations depends on the non‐dimensional number Bi = hL/k, and it increases approximately linearly with Bi for Bi≥0.6. Here, for gap heat transfer problems, h is taken to be the inverse of the contact resistance. This conclusion holds true for both 2‐ and 3‐D problems, for both linear and quadratic elements and for both transient and steady state calculations. Further numerical results for conjugate heat transfer problems encountered in heat exchanger and micro chemical reactors are computed using the gap element approach, the direct numerical simulations and analytical solutions whenever solvable. The results reveal that for the standard heat exchanger designs, an accurate prediction of temperature distribution in the moving streams must take into consideration the radial temperature distribution and the accuracy of the calculations depends on the non‐dimensional number Bi = hR/2k. From gap element calculations, it is found that classical analytical solutions are valid for a heat transfer analysis of an exchanger system, only when Bi<0.1. This important point so far has been neglected in virtually all the textbooks on heat transfer and must be included to complete the heat transfer theory for heat exchanger designs. Results also suggest that for thermal fluids systems with chemical reactions such as micro fuel cells, the gap element approach yields accurate results only when the heat transfer coefficient that accounts for the chemical reactions is used. However, when these heat transfer coefficients are not available, direct numerical simulations should be used for an accurate prediction of the thermal performance of these systems.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 12 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 7 August 2009

Ignacijo Bilus and Andrej Predin

This study aims to present the analysis of methods for cavitaion surge obstruction in water pump systems with particular focus on the two different inlet geometry configurations.

Abstract

Purpose

This study aims to present the analysis of methods for cavitaion surge obstruction in water pump systems with particular focus on the two different inlet geometry configurations.

Design/methodology/approach

A cavitating flow field was simulated by RANS based computational fluid dynamics (CFD) program for different pump configurations operating in the unstable cavitation regime, inducing surging process. Numerical simulation results were compared to visualization and measurements results.

Findings

Presented results show that a hydro dynamically induced surging regime could be limited and further advantages regarding operating characteristics of radial pumps could be achieved with presented geometry modifications.

Originality/value

This study provides insight into complicated transient cavitation flow patterns in conventional centrifugal pumps and introduces effective geometry optimization ideas useful to researchers and engineers in the area of fluid dynamics and hydromachinery.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 19 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

21 – 30 of over 3000