scholarly journals Simulation of Thermal Radiation and Turbulent Free Convection in an Enclosure with a Glass Wall and a Local Heater

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 91
Author(s):  
Igor V. Miroshnichenko ◽  
Aidar A. Toilibayev ◽  
Mikhail A. Sheremet
Keyword(s):  
Thermal Radiation ◽  
Large Scale ◽  
Fluid Motion ◽  
Great Influence ◽  
Robin Boundary Condition ◽  
Surface Emissivity ◽  
Convective Boundary ◽  
Glass Wall ◽  
Uniform Grids ◽  
Robin Boundary

In this study, a numerical modelling of thermal radiation and turbulent thermogravitational convection in a large-scale chamber containing a thermally-generating element is conducted. The lower border of the cabinet is maintained under adiabatic conditions, while on the other walls the convective boundary conditions (Robin boundary condition) are used. The managing equations with corresponding restrictions are transformed using the stream function–vorticity formulation and then solved by employing a finite difference method. The influence of both the height and wall emissivity of the heated source on fluid motion and the heat transmission in a large-scale chamber is investigated. Our results of the calculations on non-uniform grids with algebraic transformation are in excellent agreement with other available experimental and numerical outcomes for turbulent thermal convection in enclosures. The computations indicate that the average total Nusselt number is enhanced up to 2 times with an increase in the heater height. The results show that the surface emissivity of the heat source has a great influence on the total thermal transference coefficient. Furthermore, a growth of the heater surface emissivity has no significant effect on the flow structure.

CASIMIR EFFECT FOR THE ROBIN SURFACES IN STATIC ROBERTSON–WALKER SPACE–TIME

2011 ◽  
Vol 20 (02) ◽  
pp. 161-168 ◽  
Author(s):  
MOHAMMAD R. SETARE ◽  
M. DEHGHANI
Keyword(s):  
Scalar Field ◽  
Energy Momentum Tensor ◽  
Casimir Effect ◽  
Vacuum Expectation ◽  
Robin Boundary Condition ◽  
Momentum Tensor ◽  
Space Time ◽  
Conformally Invariant ◽  
Time Space ◽  
Robin Boundary

We investigate the energy–momentum tensor for a massless conformally coupled scalar field in the region between two curved surfaces in k = -1 static Robertson–Walker space–time. We assume that the scalar field satisfies the Robin boundary condition on the surfaces. Robertson–Walker space–time space is conformally related to Rindler space; as a result we can obtain vacuum expectation values of the energy–momentum tensor for a conformally invariant field in Robertson–Walker space–time space from the corresponding Rindler counterpart by the conformal transformation.

scholarly journals Solutions for parametric double phase Robin problems

2021 ◽  
Vol 121 (2) ◽  
pp. 159-170 ◽  
Author(s):  
Nikolaos S. Papageorgiou ◽  
Calogero Vetro ◽  
Francesca Vetro
Keyword(s):  
Boundary Condition ◽  
Existence Theorems ◽  
Robin Boundary Condition ◽  
Phase Problem ◽  
Double Phase ◽  
Robin Boundary ◽  
Double Phase Problem

We consider a parametric double phase problem with Robin boundary condition. We prove two existence theorems. In the first the reaction is ( p − 1 )-superlinear and the solutions produced are asymptotically big as λ → 0 + . In the second the conditions on the reaction are essentially local at zero and the solutions produced are asymptotically small as λ → 0 + .

Mixing of Matter by a Rising Bubble Near a Wall

2011 ◽  
Author(s):  
Toru Koso ◽  
Hiroyuki Iwashita ◽  
Fumihiko Usuki
Keyword(s):  
Large Scale ◽  
Uv Light ◽  
Fluid Motion ◽  
Turbulent Diffusion Coefficient ◽  
Air Bubble ◽  
Rising Bubble ◽  
Mass Dispersion ◽  
Mixing Patterns ◽  
Bubble Rising ◽  
Near Wall

The turbulent mixing of liquid mass caused by an air bubble rising near a wall in a still liquid in a pipe is investigated experimentally using a photochromic dye. A part of the liquid is activated by UV light and subjected to the fluid motion caused by a zigzag rising bubble of which Reynolds number is 214. The visualized mixing patterns showed that the dye is mixed by vortex motions in the bubble wake that is similar to the case of a bubble rising in the center of the pipe. The concentration distributions were deduced from the dye images using Lambert-Beer’s law and the turbulent diffusion coefficient (TDC) was evaluated from the temporal changes in the mass dispersion. The TDCs showed that a near-wall bubble generates stronger mixing than for a bubble in the center of the pipe. This stronger mixing can be attributed to the large-scale vortices observed for a near-wall bubble, which remains active for a longer time due to the lack of oppositely rotating vortices and mixes more fluids.

Magnetohydrodynamics (MHD) Heat and Mass Transfer of Casson Fluid Flow Past a Semi-Infinite Vertical Plate with Thermophoresis Effect: Spectral Relaxation Analysis

2018 ◽  
Vol 389 ◽  
pp. 18-35
Author(s):  
Bidemi O. Falodun ◽  
C. Onwubuoya ◽  
F.H. Awoniran Alamu
Keyword(s):  
Thermal Radiation ◽  
Viscous Dissipation ◽  
Heat Generation ◽  
Porous Plate ◽  
Great Influence ◽  
Thermal Engineering ◽  
Concentration Profiles ◽  
Local Skin ◽  
Flow Equations ◽  
Spectral Relaxation

In this paper, boundary layer flow of non-Newtonian Casson fluids past a semi-infinite porous plate in the presence of thermal radiation, viscous dissipation and heat generation is explored. Fluids of this type act as solid elastic and they are very important in food technology, biological science, etc. The flow took place over a semi-infinite vertical porous plate. The presence of viscous dissipation in the flow equations plays a significant role on flows having high viscosity such as polymers and oils. Thermal radiation and heat generation plays a decisive role in the design of many advanced energy conversion system which operates at higher temperature. Hence, the present study is useful in food processing industries and thermal engineering processes. The flows governing equations are numerically solved with spectral relaxation method (SRM). SRM is an iterative procedure that employs the Gauss-siedel type of relaxation approach to linearize and decoupled the system of coupled differential equations. The influence of controlling parameters on velocity, temperature and concentration profiles are plotted in graphs. Furthermore, numerical computations of the local skin friction, local Nusselt number and local sherwood number are presented in tabular form. Results revealed that the presence of the thermophoresis in the concentration equation has great influence on the velocity and concentration profiles because increasing the thermophoresis parameter intensifies the velocity and concentration profiles.

scholarly journals Equivalent Robin boundary conditions for acoustic and elastic media

2016 ◽  
Vol 26 (08) ◽  
pp. 1531-1566 ◽  
Author(s):  
Julien Diaz ◽  
Victor Péron
Keyword(s):  
Acoustic Waves ◽  
Mathematical Problem ◽  
Diffraction Problem ◽  
Robin Boundary Condition ◽  
Elastic Displacement ◽  
Fluid Medium ◽  
Asymptotic Models ◽  
Multiscale Expansion ◽  
Robin Boundary ◽  
Equivalent Conditions

We present equivalent conditions and asymptotic models for a diffraction problem of acoustic and elastic waves. The mathematical problem is set with a Robin boundary condition. Elastic and acoustic waves propagate in a solid medium surrounded by a thin layer of fluid medium. Due to the thinness of the layer with respect to the wavelength, this problem is well suited for the notion of equivalent conditions and the effect of the fluid medium on the solid is as a first approximation local. This approach leads to solve only elastic equations. We derive and validate equivalent conditions up to the third order for the elastic displacement. The construction of equivalent conditions is based on a multiscale expansion in power series of the thickness of the layer for the solution of the transmission problem.

Sign in / Sign up

Export Citation Format

Share Document