An Improved Synthetic Eddy Method for Generating Inlet Turbulent Boundary Layers

An improved synthetic eddy method (SEM) is proposed in this paper for generating the boundary layer at the inlet of a computational domain via direct numerical simulation. The improved SEM modified the definition of the radius and the velocities of the eddies according to the distance of the eddies from the wall in the synthetic region. The regeneration location of the eddies is also redefined. The simulation results show that the improved SEM generates turbulent fluctuations that closely match the DNS results of the experiments. The skin friction coefficient of the improved SEM recovers much faster and has lower dimensionless velocity at the outer of the boundary layer than that of the traditional SEM.

Effect of moving stretching sheets on natural convection in partially heated square cavity filled with nanofluid

This article deals with the heat transfer enhancement due to buoyancy force in a partially heated square enclosure filled with nanofluids. The model is developed to analyse the behaviour of nanofluids taking into account of volume fraction and stretching parameter, when square horizontal walls are moving in opposite directions to each other. Implicit alternate direct finite difference method has been used to solve the governing equations of vorticity, energy, and kinematics. Graphically investigated the effect of physical pertinent controlling parameters on the dimensionless velocity, streamlines, isothermal, and Nusselt number. The obtained numerical solution achieves the best configuration for Rayleigh number 103 ≤ Ra ≤ 105, stretching parameter 0 ≤ τ ≤ 2.5, and volume fraction 0 ≤ ϕ ≤ 0.2. It is found that the stretching parameter and direction of moving walls affect the fluid flow, flow strength, and heat transfer in the cavity.

Symmetric and Non-Symmetric Flows of Burgers’ Fluids through Porous Media between Parallel Plates

Unidirectional unsteady flows of the incompressible Burgers’ fluids between two infinite horizontal parallel plates are analytically studied when the magnetic and porous effects are taken into consideration. The fluid motion is induced by the two plates, which move in their planes with time-dependent velocities. Exact general expressions are established both for the dimensionless velocity and shear stress fields as well as the corresponding Darcy’s resistance in the channel using the Laplace transform. If both plates move with equal velocities in the same direction, the fluid motion becomes symmetric with respect to the mid-plane between them. Otherwise, its motion is non-symmetric. To bring to light the behavior of the fluid, the dimensionless velocity profiles versus the spatial variable as well as its time evolution are presented both for the symmetric and asymmetric case. Finally, for comparison, similar graphical representations are presented together for the velocities of the incompressible Oldroyd-B and Burgers’ fluids. For large values of the time t, as expected, the behavior of the two different fluids is almost identical. The Darcy’s resistance against y is also graphically represented for the symmetric flow at different values of the time t. The influence of the magnetic field on the fluid motion is graphically revealed and discussed.

Critical values in axisymmetric flow of magneto–Cross nanomaterial towards a radially shrinking disk

In this study, we investigated dual solutions for the influence of chemical reaction and radiation effect on axisymmetric flow of magneto-Cross nanomaterial towards a radially shrinking disk on taking account of stagnation point. The governing expressions which describe the assumed flow are reduced to ordinary differential equations by opting suitable similarity variables. The dual solutions on the performance of dimensionless velocity, thermal, concentration gradients, skin friction, rate of heat and mass transfer with the impact of relevant parameters are studied using suitable graphs. Result outcomes reveal that, upsurge in Brownian motion parameter improves the thermal gradient in case of both the solution but, converse trend is detected in concentration gradient. The uplift of thermophoresis parameter boosts up the concentration gradient in both branch solution but reverse trend is noticed in concentration profile for inclined values of Schmidt number. Further, dual nature of solutions exists only for certain range of shrinking parameter.

Conundrum of aortic stenosis in a case of multivalvular rheumatic heart disease: perspicuity is in the details

A 36-year-old woman presented with dyspnoea on exertion for 5 years. She was evaluated elsewhere and diagnosed to have severe mitral stenosis. She was referred for mitral valve replacement to our centre. Echocardiography revealed a thickened aortic valve with mild aortic regurgitation, with transaortic gradient suggestive of mild aortic stenosis, in addition to severe rheumatic mitral stenosis. Detailed echocardiographic analysis and cardiac catheterisation revealed features suggestive of moderate to severe aortic stenosis. Detailed assessment of aortic valve needs to be done in patients with coexistent mitral stenosis. Each modality for assessment of aortic stenosis has its own limitations and a decision regarding treatment needs to be taken based on combined analysis of all the parameters. Dimensionless velocity index is a relatively less time-consuming, flow independent measure of aortic stenosis. Prompt recognition of this concealed aortic stenosis helps to avoid repeat valve surgery. Subsequently, patient was sent for dual valve replacement.

The Investigation of MHD Williamson Nanofluid over Stretching Cylinder with the Effect of Activation Energy

In this paper, we discussed the effect of activation energy on mixed convective heat and mass transfer of Williamson nanofluid with heat generation or absorption over a stretching cylinder. Dimensionless ordinary differential equations are obtained from the modeled PDEs by using appropriate transformations. Numerical results of the skin friction coefficient, Nusselt number, and Sherwood number for different parameters are computed. The effects of the physical parameter on temperature, velocity, and concentration have been discussed in detail. From the result, it is found that the dimensionless velocity decreases whereas temperature and concentration increase when the porous parameter is enhanced. The present result has been compared with published paper and found good agreement.

Lie Group Analysis of Unsteady Flow of Kerosene/Cobalt Ferrofluid Past A Radiated Stretching Surface with Navier Slip and Convective Heating

In this work, we identified the characteristics of unsteady magnetohydrodynamic (MHD) flow of ferrofluid past a radiated stretching surface. Cobalt–kerosene ferrofluid is considered and the impacts of Navier slip and convective heating are additionally considered. The mathematical model which describes the problem was built from some partial differential equations and then converted to self-similar equations with the assistance of the Lie group method; after that, the mathematical model was solved numerically with the aid of Runge–Kutta–Fehlberg method. Graphical representations were used to exemplify the impact of influential parameters on dimensionless velocity and temperature profiles; the obtained results for the skin friction coefficient and Nusselt number were also examined graphically. It was demonstrated that the magnetic field, Navier slip, and solid volume fraction of ferroparticles tended to reduce the dimensionless velocity, while the radiation parameter and Biot number had no effects on the dimensionless velocity. Moreover, the magnetic field and solid volume fraction increase skin friction whereas Navier slip reduces the skin friction. Furthermore, the Navier slip and magnetic field reduce the Nusselt number, whereas solid volume fraction of ferroparticles, convective heating, and radiation parameters help in increasing the Nusselt number.

Modeling the Transport of Hydrocarbons in the Subsurface Environment with Chemical Reaction

The objective of the present study is to investigate the transport of hydrocarbons with chemical reaction due to oil flow through the subsurface. The coupled nonlinear differential equations governing the flow and mass transfer are simplified using perturbation technique and solved numerically. The dimensionless velocity and concentration profiles are depicted graphically and discussed for the effects of the parameters involved.

Characterization of drag reduction performance over rotating microgrooves with different cross-sections

This paper presents a study of cross-sectional parameters and optimal drag reduction performance specifically for drag reduction in rotating microgroove applications. Rotating triangular microgrooves with nine asymmetrical and symmetrical cross-sections were numerically studied. In addition, a representative symmetrical rotating microgroove was experimentally tested. Positive asymmetrical microgrooves (including symmetrical microgrooves) were found to be sensitive to rotating Reynolds numbers and produced more significant drag reduction. Compared with a dimensioned asymmetry variable and other dimensionless parameters, the dimensionless asymmetry variable i+ could be used to describe drag reduction performance, which captured both the influence of microgroove cross-sectional asymmetry and turbulence intensity. A maximum drag reduction of up to 8.9% was obtained at 9.2 i+. With the exception of the torque, the velocity shift obtained from dimensionless velocity profiles could also be used to predict drag reduction performance, which has the potential for wider and more comprehensive application for any drag reduction technology.

3D Simulation of Incompressible Poiseuille Flow through 180° Curved Duct of Square Cross-section under Effect of Thermal Buoyancy

In this paper, three-dimensional numerical simulations are carried out to investigate and analyze the gradual effects of thermal buoyancy strength on laminar flow of an incompressible viscous fluid and heat transfer rate inside a 180° curved channel of square cross-section. The governing equations of continuity, momentum and energy balance are obtained and solved numerically using finite volume method. The effect of Dean number, De, and Richardson number, Ri, on dimensionless velocity profiles and Nusselt number are examined for the conditions: De = 125 to 150, Ri = 0 to 2 at Pr = 1. The mean results are illustrated in terms of streamline and isotherm contours to interpret the flow behaviors and its effect on heat transfer rate. Dimensionless velocity profiles and the local Nusselt number at the angle 0° and 90° are presented and discussed. Also, the average Nusselt number on surfaces of curved duct is computed. The obtained results showed that by adding thermal buoyancy to computed domain, some early Dean vortices are observed at the angle 0° and new sort are observed at 90°. Furthermore, increase in Dean number increases the heat transfer rate. In other hand, increase in Richardson number decreases the average Nusselt number of 180° curved duct.