scholarly journals Finite Difference Analysis of Unsteady Heat and Flow of an Incompressible Third Grade Fluid

2021 ◽  
pp. 307-318
Author(s):  
I Nayak
Keyword(s):  
Finite Difference ◽  
Viscous Dissipation ◽  
High Speed ◽  
Transfer Problem ◽  
Coupled System ◽  
Elastic Parameter ◽  
Physical Parameters ◽  
Fully Implicit ◽  
Grade Fluid ◽  
Matlab Programming

An unsteady flow and heat transfer problem with viscous dissipation of a third order fluid placed within two long parallel flat porous walls is studied in present work. The governing equations are non- dimensionalized and finally a non-linear coupled system of partial differential equation is obtained. An approximated solution is obtained using finite difference method of fully implicit form. With help of high speed MATLAB programming numerical solution is procured and presented graphically. Investigation is made on effect of different physical parameters on flow and heat profile. The notable finding in the current work is that for smaller values of visco-elastic parameter ®, the velocity rises with raising the values of ®. But for larger visco-elastic parametric values of ®, a reversed effect is seen on velocity field. Also with the increase of viscous-dissipation parameter, more viscous-dissipation heat generated that increases the temperature field.

scholarly journals Analysis of Electro-MHD of Third Grade Fuid Flow Through Porous Channel

2020 ◽  
Vol 13 (5) ◽  
pp. 1270-1284
Author(s):  
Sukanya Padhi ◽  
Itishree Nayak
Keyword(s):  
Magnetic Field ◽  
Nonlinear Partial Differential Equation ◽  
Mhd Flow ◽  
Elastic Parameter ◽  
Third Grade ◽  
Porous Channel ◽  
Third Grade Fluid ◽  
Fully Implicit ◽  
Contrasting Effect ◽  
Grade Fluid

This paper examines the Electro-MHD flow and heat transfer of a third grade fluid passing through a porous channel. An unidirectional and one-dimensional flow is propelled with the aid of lorentz force generated due to interaction of vertically applied magnetic field along with horizontally applied electric field. The equations of momentum and energy governing the third grade fluid flow are transformed to algebraic equation from nonlinear partial differential equation by implementing fully implicit finite difference scheme and solution is obtained by damped-Newton method. Lastly, the problem is simulated using MATLAB and the influence on velocity and temperature profiles with variation of non-dimensional parameters are depicted graphically. The noteworthy findings of this study is that the increasing values of elastic parameter α and non-Newtonian parameter γ diminishes the flow velocity and results in enhancement of temperature profile. A completely contrasting effect is observed for increasing values of strength of electric and magnetic field.

scholarly journals A Fully Implicit Finite Volume Scheme for a Seawater Intrusion Problem in Coastal Aquifers

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1639
Author(s):  
Abdelkrim Aharmouch ◽  
Brahim Amaziane ◽  
Mustapha El Ossmani ◽  
Khadija Talali
Keyword(s):  
Finite Volume ◽  
Coastal Aquifers ◽  
Nonlinear Partial Differential Equations ◽  
Time Integration ◽  
Mass Conservation ◽  
Coupled System ◽  
Finite Volume Scheme ◽  
Time Step ◽  
Volume Scheme ◽  
Fully Implicit

We present a numerical framework for efficiently simulating seawater flow in coastal aquifers using a finite volume method. The mathematical model consists of coupled and nonlinear partial differential equations. Difficulties arise from the nonlinear structure of the system and the complexity of natural fields, which results in complex aquifer geometries and heterogeneity in the hydraulic parameters. When numerically solving such a model, due to the mentioned feature, attempts to explicitly perform the time integration result in an excessively restricted stability condition on time step. An implicit method, which calculates the flow dynamics at each time step, is needed to overcome the stability problem of the time integration and mass conservation. A fully implicit finite volume scheme is developed to discretize the coupled system that allows the use of much longer time steps than explicit schemes. We have developed and implemented this scheme in a new module in the context of the open source platform DuMu X . The accuracy and effectiveness of this new module are demonstrated through numerical investigation for simulating the displacement of the sharp interface between saltwater and freshwater in groundwater flow. Lastly, numerical results of a realistic test case are presented to prove the efficiency and the performance of the method.

Experimental investigation of wall heat transfer due to spray combustion in a high-pressure/high-temperature vessel

2021 ◽  
pp. 146808742110072
Author(s):  
Karri Keskinen ◽  
Walter Vera-Tudela ◽  
Yuri M Wright ◽  
Konstantinos Boulouchos
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
High Temperature ◽  
High Speed ◽  
Transfer Problem ◽  
Wall Heat Transfer ◽  
Gas Temperature ◽  
Reference Case ◽  
High Pressure High Temperature

Combustion chamber wall heat transfer is a major contributor to efficiency losses in diesel engines. In this context, thermal swing materials (adapting to the surrounding gas temperature) have been pinpointed as a promising mitigative solution. In this study, experiments are carried out in a high-pressure/high-temperature vessel to (a) characterise the wall heat transfer process ensuing from wall impingement of a combusting fuel spray, and (b) evaluate insulative improvements provided by a coating that promotes thermal swing. The baseline experimental condition resembles that of Spray A from the Engine Combustion Network, while additional variations are generated by modifying the ambient temperature as well as the injection pressure and duration. Wall heat transfer and wall temperature measurements are time-resolved and accompanied by concurrent high-speed imaging of natural luminosity. An investigation with an uncoated wall is carried out with several sensor locations around the stagnation point, elucidating sensor-to-sensor variability and setup symmetry. Surface heat flux follows three phases: (i) an initial peak, (ii) a slightly lower plateau dependent on the injection duration, and (iii) a slow decline. In addition to the uncoated reference case, the investigation involves a coating made of porous zirconia, an established thermal swing material. With a coated setup, the projection of surface quantities (heat flux and temperature) from the immersed measurement location requires additional numerical analysis of conjugate heat transfer. Starting from the traces measured beneath the coating, the surface quantities are obtained by solving a one-dimensional inverse heat transfer problem. The present measurements are complemented by CFD simulations supplemented with recent rough-wall models. The surface roughness of the coated specimen is indicated to have a significant impact on the wall heat flux, offsetting the expected benefit from the thermal swing material.

scholarly journals A new fourth-order explicit group method in the solution of two-dimensional fractional Rayleigh–Stokes problem for a heated generalized second-grade fluid

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Muhammad Asim Khan ◽  
Norhashidah Hj. Mohd Ali ◽  
Nur Nadiah Abd Hamid
Keyword(s):  
Finite Difference ◽  
Stokes Problem ◽  
Stability And Convergence ◽  
Second Grade ◽  
Group Method ◽  
Two Dimensional ◽  
Second Grade Fluid ◽  
The Matrix ◽  
Grade Fluid ◽  
Generalized Second Grade Fluid

Abstract In this article, a new explicit group iterative scheme is developed for the solution of two-dimensional fractional Rayleigh–Stokes problem for a heated generalized second-grade fluid. The proposed scheme is based on the high-order compact Crank–Nicolson finite difference method. The resulting scheme consists of three-level finite difference approximations. The stability and convergence of the proposed method are studied using the matrix energy method. Finally, some numerical examples are provided to show the accuracy of the proposed method.

VERTICAL SCALING OF TYPE I InP HBT WITH FT > 500 GHZ

2004 ◽  
Vol 14 (03) ◽  
pp. 625-631 ◽  
Author(s):  
J. W. LAI ◽  
W. HAFEZ ◽  
M. FENG
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
High Speed ◽  
Impact Ionization ◽  
Cutoff Frequency ◽  
Current Gain ◽  
Vertical Scaling ◽  
Physical Parameters ◽  
Type I ◽  
Peak Current Density ◽  
Rf Performance

We have fabricated the high-speed InP/InGaAs -based single heterojunction bipolar transistors (SHBTs) with current gain cutoff frequency, fT from 166GHz to over 500GHz by the approach of vertical scaling. Collector thickness is reduced from 3000Å to 750Å and the peak current density is increased up to 1300kA/cm2. In this paper, device rf performance has been compared with respect to materials with different vertical dimensions. The scaling limitation is also studied by analytical approach. The extracted physical parameters suggest that the parasitic emitter resistance is the major limit on further enhancing ultra-scaled HBT intrinsic speed due to the associated RECBC delay. The cut-off frequency of a 500Å collector SHBT has been measured and the results indicate a dramatic drop on fT, supporting the conclusion projected by model analysis. It is also commented that for deeply downscaled HBTs, impact ionization could be another degrading mechanism limits device bandwidth.

scholarly journals On the Influence of Soret and Dufour Effects on MHD Free Convective Heat and Mass Transfer Flow over a Vertical Channel with Constant Suction and Viscous Dissipation

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Ime Jimmy Uwanta ◽  
Halima Usman
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Viscous Dissipation ◽  
Convective Heat ◽  
Vertical Channel ◽  
Skin Friction Coefficient ◽  
Physical Parameters ◽  
Soret And Dufour Effects ◽  
Constant Suction ◽  
Dufour Number

The present paper investigates the combined effects of Soret and Dufour on free convective heat and mass transfer on the unsteady one-dimensional boundary layer flow over a vertical channel in the presence of viscous dissipation and constant suction. The governing partial differential equations are solved numerically using the implicit Crank-Nicolson method. The velocity, temperature, and concentration distributions are discussed numerically and presented through graphs. Numerical values of the skin-friction coefficient, Nusselt number, and Sherwood number at the plate are discussed numerically for various values of physical parameters and are presented through tables. It has been observed that the velocity and temperature increase with the increase in the viscous dissipation parameter and Dufour number, while an increase in Soret number causes a reduction in temperature and a rise in the velocity and concentration.

Paper 3: Recent Developments in Fluid Film Lubrication Theory

1967 ◽  
Vol 182 (1) ◽  
pp. 36-50 ◽  
Author(s):  
T. Lloyd ◽  
H. McCallion
Keyword(s):  
Finite Difference ◽  
High Speed ◽  
Lubrication Theory ◽  
Fluid Film ◽  
Special Topic ◽  
Finite Difference Schemes ◽  
Great Activity ◽  
Wide Range ◽  
Film Lubrication ◽  
Fluid Film Lubrication

Developments in high-speed electronic computers have greatly influenced the progress in fluid film lubrication over the past ten years. Static and dynamic oil film parameters have been computed for a wide range of finite geometries, for hydrostatic and hydrodynamic bearings lubricated by compressible and incompressible lubricants. These are either sufficient in themselves or else act as a yardstick against which approximate formulas may be tested. Much use has been made of iterative finite difference schemes, which are particularly well suited to digital computers, and these methods are now more fully understood. Other methods of solution include direct inversion of finite difference matrices and solution by expression of the pressure by some infinite series, a finite number of terms of which give adequate representation. Besides the increase in design data available, there has been substantial progress through a re-examination of the effects of modifying some of the assumptions inherent in most of the available solutions of the Reynolds equation. These include the assumption of constant lubricant viscosity, of rigid surfaces and of laminar flow. Major progress has been witnessed in two fields. The interaction of the lubricant film with elastic boundaries has been shown to be of prime importance in highly loaded contacts such as gears. This has led to the development of the special topic of elastohydrodynamic lubrication theory. The applicability of gas bearings in such growing industries as computers, space vehicles and nuclear reactors has resulted in great activity and progress in this field.

scholarly journals A gradient field defeats the inherent repulsion between magnetic nanorods

2014 ◽  
Vol 1 (2) ◽  
pp. 140271 ◽  
Author(s):  
Yu Gu ◽  
Ruslan Burtovyy ◽  
John Custer ◽  
Igor Luzinov ◽  
Konstantin G. Kornev
Keyword(s):  
Phase Portrait ◽  
High Speed ◽  
Uniform Magnetic Field ◽  
Gradient Field ◽  
Physical Parameters ◽  
Uniform Field ◽  
Experimental Conditions ◽  
Magnetic Nanorods ◽  
Field Gradients ◽  
And Control

When controlling the assembly of magnetic nanorods and chains of magnetic nanoparticles, it is extremely challenging to bring them together side by side while keeping a desired spacing between their axes. We show that this challenge can be successfully resolved by using a non-uniform magnetic field that defeats an inherent repulsion between nanorods. Nickel nanorods were suspended in a viscous film and a non-uniform field was used to control their placement. The in-plane movement of nanorods was tracked with a high-speed camera and a detailed image analysis was conducted to quantitatively characterize the behaviour of the nanorods. The analysis focused on the behaviour of a pair of neighbour nanorods, and a corresponding dynamic model was formulated and investigated. The complex two-dimensional dynamics of a nanorod pair was analysed analytically and numerically, and a phase portrait was constructed. Using this phase portrait, we classified the nanorod behaviour and revealed the experimental conditions in which nanorods could be placed side by side. Dependence of the distance between a pair of neighbour nanorods on physical parameters was analysed. With the aid of the proposed theory, one can build different lattices and control their spacing by applying different field gradients.

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