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The purpose of this paper is to focus on thermal characteristics behavior of forced convection flow in a duct over forward facing step (FFS), in which all of the heat transfer mechanisms, including convection, conduction and radiation, take place simultaneously in the fluid flow.

The fluid is treated as a gray, absorbing, emitting and scattering medium. The Navier‐Stokes and energy equations are solved numerically by computational fluid dynamics (CFD) techniques to obtain the velocity and temperature fields. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, all of the convection, conduction and radiation heat transfer take place simultaneously in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinate method (DOM) to find the radiative heat flux distribution inside the radiating medium. By this numerical approach, the velocity, pressure and temperature fields are calculated.

The effect of wall emissivity, optical thickness, albedo coefficient and the radiation‐conduction parameter on heat transfer behavior of the system are also investigated. The numerical results for two cases of convection‐conduction and conduction‐radiation problems are compared with the available data published in open literature and good agreement was obtained.

This is the first time in which flow over FFS in a duct, considering all heat transfer mechanisms including conduction, convection and radiation, is solved numerically.

The purpose of this paper is to assess the turbulent thermohydrodynamic (THD) performance characteristics of an axially grooved finite journal bearing for a variety of simulated operating conditions.

The set of governing equations consisting the Navier‐Stokes, turbulent kinetic energy and its dissipation rate equations coupled with the energy equation in the lubricant flow and the heat conduction equation for the bush are solved to obtain the three dimensional steady state THD characteristics of journal bearings. The lubricant flow in turbulent regime is modelled using the AKN low‐Re k−ϵ turbulence model. The problem is formulated mathematically and solved numerically using the computational fluid dynamics (CFD) approach with appropriate boundary conditions.

It was found that shaft rotational speed has dramatic effects on the maximum temperature of the bearing and lubricant, also on the maximum hydrodynamic pressure and the oil flow rate. Besides, it was revealed that the clearance ratio and eccentricity ratio significantly change the performance of the journal bearing.

The paper presents a very useful numerical method for the prediction of the pressure and temperature fields inside the lubricant and thermal simulation of the bearing.

The paper provides the numerical simulation of the flow and heat transfer inside the journal bearing. Present computational approach is valuable to the practical modeling of the journal bearing operating under turbulent regime and in preparing the design charts in prediction of both hydrodynamic and thermal behaviors of journal bearings.

This study aims to perform a comprehensive investigation to model the thermal characteristics of a coupled conduction-radiation heat transfer in a two-dimensional irregular enclosure including a triangular-shaped heat source.

For this purpose, a promising hybrid technique based on the concepts of blocked-off method, FVM and DOM is developed. The enclosure consists of several horizontal, vertical and oblique walls, and thermal conductivity within the enclosure varies directly with temperature and indirectly with position. To simplify the complex geometry, a promising mathematical model is introduced using blocked-off method. Emitting, absorbing and non-isotropic scattering gray are assumed as the main radiative characteristics of the steady medium.

DOM and FVM are, respectively, applied for solving radiative transfer equation (RTE) and the energy equation, which includes conduction, radiation and heat source terms. The temperature and heat flux distributions are calculated inside the enclosure. For validation, results are compared with previous data reported in the literature under the same conditions. Results and comparisons show that this approach is highly efficient and reliable for complex geometries with coupled conduction-radiation heat transfer. Finally, the effects of thermo-radiative parameters including surface emissivity, extinction coefficient, scattering albedo, asymmetry factor and conduction-radiation parameter on temperature and heat flux distributions are studied.

In this paper, a hybrid numerical method is used to analyze coupled conduction-radiation heat transfer in an irregular geometry. Varying thermal conductivity is included in this analysis. By applying the method, results obtained for temperature and heat flux distributions are presented and also validated by the data provided by several previous papers.

The purpose of this paper is to investigate a model for convection induced by the selective absorption of radiation in a fluid layer. The concentration based internal heat source is modelled quadratically. Both linear instability and global nonlinear energy stability analyses are tested using three dimensional simulations. The results show that the linear threshold accurately predicts on the onset of instability in the basic steady state. However, the required time to arrive at the steady state increases significantly as the Rayleigh number tends to the linear threshold.

The author introduce the stability analysis of the problem of convection induced by absorption of radiation in fluid layer, then the author select a situations which have very big subcritical region. Then, the author develop a three dimensions simulation for the problem. To do this, first, the author transform the problem to velocity – vorticity formulation, then the author use a second order finite difference schemes. The author use implicit and explicit schemes to enforce the free divergence equation. The size of the Box is evaluated according to the normal modes representation. Moreover, the author adopt the periodic boundary conditions for velocity and temperature in the $x, y$ dimensions.

This paper explores a model for convection induced by the selective absorption of radiation in a fluid layer. The results demonstrate that the linear instability thresholds accurately predict the onset of instability. A three-dimensional numerical approach is adopted.

As the author believe, this paper is one of the first studies which deal with study of stability of convection using a three dimensional simulation. When the difference between the linear and nonlinear thresholds is very large, the comparison between these thresholds is very interesting and useful.

This paper aims to investigate the effects of inertia of the lubricant on the performance parameters of journal bearings textured with spherical-shaped textures.

The lubricant is assumed to be Newtonian, and the flow is considered laminar. Considering the lubricant inertia effects, the modified Reynolds equation is discretized using the finite difference method and solved with the Gauss–Seidel successive over-relaxation scheme using the progressive mesh densification method.

The results from this numerical study indicate that the lubricant inertia improves textured journal bearing performance characteristics significantly. The improvement is more significant in the case of heavily loaded bearings. Furthermore, it is observed that protruded texturing in journal bearings shows better results compared to dimple textured journal bearings.

Understanding the effect of lubricant inertia is essential for efficiently designing textured journal bearings. Thus, the results shown here would be helpful for the researchers and the bearing designers.

Present study aims to extend the lattice Boltzmann method (LBM) to simulate radiation in geometries with curved boundaries, as the first step to simulate radiation in complex porous media. In recent years, researchers have increasingly explored the use of porous media to improve the heat transfer processes. The lattice Boltzmann method (LBM) is one of the most effective techniques for simulating heat transfer in such media. However, the application of the LBM to study radiation in complex geometries that contain curved boundaries, as found in many porous media, has been limited.

The numerical evaluation of the effect of the radiation-conduction parameter and extinction coefficient on temperature and incident radiation distributions demonstrates that the proposed LBM algorithm provides highly accurate results across all cases, compared to those found in the literature or those obtained using the finite volume method (FVM) with the discrete ordinates method (DOM) for radiative information.

For the case with a conduction-radiation parameter equal to 0.01, the maximum relative error is 1.9% in predicting temperature along vertical central line. The accuracy improves with an increase in the conduction-radiation parameter. Furthermore, the comparison between computational performances of two approaches reveals that the LBM-LBM approach performs significantly faster than the FVM-DOM solver.

The difficulty of radiative modeling in combined problems involving irregular boundaries has led to alternative approaches that generally increase the computational expense to obtain necessary radiative details. To address the limitations of existing methods, this study presents a new approach involving a coupled lattice Boltzmann and first-order blocked-off technique to efficiently model conductive-radiative heat transfer in complex geometries with participating media. This algorithm has been developed using the parallel lattice Boltzmann solver.

This paper aims to reveal the cavitation characteristics of three oil wedges sleeve bearing and set the theoretical and experimental basis for defining the oil film boundary condition.

Computational fluid dynamics model of three oil wedges sleeve bearings based on the Navier–Stokes equation is set using Fluent considering turbulent situation and two-phase flow theory. The cavitation characteristics of bearing is investigated by taking pictures of experiment.

The rupture region of oil film and the contours of air volume fraction increase distinctly with the increase of rotating speed and the decrease of input pressure. The critical rotating speed of cavitation occurrence and oil film pressure increases with the increase of input pressure. The change trend of experiment cavitation with the rotating speed and input pressure is consistent with theoretical cavitation in general.

The finite element model of three oil wedges sleeve bearings is established based on the Navier-Stokes calculation equation of the fluid, two-phase flow theory and turbulent model. Sleeve bearing is transparent, the pictures of cavitation can be easily taken by high-speed camera, the cavitation characteristics of bearing is studied by experiment. The cavitation performance of three oil wedges bearings is studied with the change of input pressure and rotating speed, the change trend is basically consistent for theory and experiment. The study on critical rotating speed of cavitation occurrence is benefit for defining the oil film boundary condition.

This paper aims to examine the thermal transmission and entropy generation of hybrid nanofluid filled containers with solid body inside. The solid body is seen as being both isothermal and capable of producing heat. A time-dependent non-linear partial differential equation is used to represent the transfer of heat through a solid body. The current study’s objective is to investigate the key properties of nanoparticles, external forces and particular attention paid to the impact of hybrid nanoparticles on entropy formation. This investigation is useful for researchers studying in the area of cavity flows to know features of the flow structures and nature of hybrid nanofluid characteristics. In addition, a detailed entropy generation analysis has been performed to highlight possible regimes with minimal entropy generation rates. Hybrid nanofluid has been proven to have useful qualities, making it an attractive coolant for an electrical device. The findings would help scientists and engineers better understand how to analyse convective heat transmission and how to forecast better heat transfer rates in cutting-edge technological systems used in industries such as heat transportation, power generation, chemical production and passive cooling systems for electronic devices.

Thermal transmission and entropy generation of hybrid nanofluid are analysed within the enclosure. The domain of interest is a square chamber of size L, including a square solid block. The solid body is considered to be isothermal and generating heat. The flow driven by temperature gradient in the cavity is two-dimensional. The governing equations, formulated in dimensionless primitive variables with corresponding initial and boundary conditions, are worked out by using the finite volume technique with the SIMPLE algorithm on a uniformly staggered mesh. QUICK and central difference schemes were used to handle convective and diffusive elements. In-house code is developed using FORTRAN programming to visualize the isotherms, streamlines, heatlines and entropy contours, which are handled by Tecplot software. The influence of nanoparticles volume fraction, heat generation factor, external magnetic forces and an irreversibility ratio on energy transport and flow patterns is examined.

The results show that the hybrid nanoparticles concentration augments the thermal transmission and the entropy production increases also while the augmentation of temperature difference results in a diminution of entropy production. Finally, magnetic force has the significant impact on heat transfer, isotherms, streamlines and entropy. It has been observed that the external magnetic force plays a good role in thermal regulations.

Hybrid nanofluid is a desirable coolant for an electrical device. Various nanoparticles and their combinations can be analysed. Ferro-copper hybrid nanofluid considered with the help of prevailing literature review. The research would benefit scientists and engineers by improving their comprehension of how to analyses convective heat transmission and forecast more accurate heat transfer rates in various fields.

Due to its helpful characteristics, ferrous-copper hybrid nanofluid is a desirable coolant for an electrical device. The research would benefit scientists and engineers by improving their comprehension of how to analyse convective heat transmission and forecast more accurate heat transfer rates in cutting-edge technological systems used in sectors like thermal transportation, cooling systems for electronic devices, etc.

Entropy generation is used for an evaluation of the system’s performance, which is an indicator of optimal design. Hence, in recent times, it does a good engineering sense to draw attention to irreversibility under magnetic force, and it has an indispensable impact on investigation of electronic devices.

An efficient numerical technique has been developed to solve this problem. The originality of this work is to analyse convective energy transport and entropy generation in a chamber with internal block, which is capable of maintaining heat and producing heat. Effects of irreversibility ratio are scrutinized for the first time. Analysis of convective heat transfer and entropy production in an enclosure with internal isothermal/heat generating blocks gives the way to predict enhanced heat transfer rate and avoid the failure of advanced technical systems in industrial sectors.

Different groove angles are used to study performance characteristics of two-axial groove journal bearing. In this study two grooves are located at ±90º to the load line. The various angles of grooves have been taken as 10° to 40° in the interval of 5°. Different equations such as Reynolds equation, three-dimensional energy equation and heat conduction equation have been solved using finite element method and finite difference method. Pressure distribution in fluid is found by using Reynolds equation. The three-dimensional energy equation is used for temperature distribution in the fluid film and bush. One-dimensional heat conduction equation is used for finding temperature in axial direction for journal. There is a very small effect of groove angle on film thickness, eccentricity ratio and pressure. There is a drastic change in attitude angle and side flow. Result shows that there is maximum power loss at large groove angle. So the smaller groove angle is recommended for two-axial groove journal bearing.

The finite element method is used for solving Reynolds equation for pressure distribution in fluid. The finite difference method is adopted for finding temperature distribution in bush, fluid and journal.

Pressure distribution in fluid is found out. Temperature distribution in bush, fluid and journal is found out. There is a very small effect of groove angle on film thickness, eccentricity ratio and pressure.

The groove angle used is from 10 to 40 degree. The power loss is more when angle of groove increases, so smaller groove angle is recommended for this study.

The location of groove angle predicts the distribution of pressure and temperature in journal bearing. It will show the performance characteristics. ±90° angle we will prefer that will get before manufacturing of bearing.

Due to this study, we will get predict how the pressure and temperature distribute in the journal. It will give the running condition of bearing as to at what speed and load we will get the maximum temperature and pressure in the bearing.

The finite element method is used for solving the Reynolds equation. Three-dimensional energy equation is solved using the finite difference method. Heat conduction equation is also solved for journal. The C language is used. The code is developed in C language. There are different equations which depend on each other. The temperature is dependent on pressure viscosity of fluid, etc. so C code is preferred.

This paper aims to numerically analyze the effect of non-gray gas radiation on mixed convection in a horizontal circular duct with isothermal partial heating from the sidewall. The influence of heater location on heat transfer, fluid flow and entropy generation is given and discussed in this study.

The numerical computation of heat transfer and fluid flow has been developed by the commercial finite element software COMSOL Multiphysics. Radiation code is developed based on the T₁₀ Ray-Tracing method, and the radiative properties of the medium are computed based on the statistical narrow band correlated-k model.

The obtained results depicted that the radiation considerably contributes to the temperature homogenization of the gas. The findings highlight the impact of the heater location on swirling flow. It is also shown that the laterally heating process provides better energy efficiency than heating from the top of the enclosure.

This study is performed to improve heat transfer and to minimize entropy generation. Therefore, it is conceivable to improve the model design of industrial applications.