Forced Convection Past an Oblate Spheroid at Low to Moderate Reynolds Numbers

2005 ◽  
Vol 127 (9) ◽  
pp. 1062-1070 ◽  
Author(s):  
Rajai S. Alassar
Keyword(s):  
Forced Convection ◽  
Transfer Rate ◽  
Oblate Spheroid ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Axis Ratio ◽  
Thermal Fields ◽  
Energy Equations ◽  
Published Research ◽  
Series Truncation Method

Abstract Forced convection past a heated oblate spheroid is studied in an attempt to investigate the effect of the axis ratio on the heat transfer rate. The time-dependent full Navier–Stokes and energy equations are solved using a series truncation method. The axis ratios considered range from 1∕2 to 1 (a perfect sphere). The results for the flow and thermal fields are satisfactorily compared with relevant published research. The results are presented in the form of streamlines, isotherms, and the local and averaged Nusselt number distributions.

On cavity flow at high Reynolds numbers

1977 ◽  
Vol 79 (2) ◽  
pp. 391-414 ◽  
Author(s):  
M. Nallasamy ◽  
K. Krishna Prasad
Keyword(s):  
Reynolds Numbers ◽  
Separated Flows ◽  
Navier Stokes ◽  
Thermal Fields ◽  
High Reynolds Numbers ◽  
Wide Range ◽  
High Reynolds ◽  
Energy Equations ◽  
First Time ◽  
Finite Difference Techniques

The flow in a square cavity is studied by solving the full Navier–Stokes and energy equations numerically, employing finite-difference techniques. Solutions are obtained over a wide range of Reynolds numbers from 0 to 50000. The solutions show that only at very high Reynolds numbers (Re[ges ] 30000) does the flow in the cavity completely correspond to that assumed by Batchelor's model for separated flows. The flow and thermal fields at such high Reynolds numbers clearly exhibit a boundary-layer character. For the first time, it is demonstrated that the downstream secondary eddy grows and decays in a manner similar to the upstream one. The upstream and downstream secondary eddies remain completely viscous throughout the range of Reynolds numbers of their existence. It is suggested that the behaviour of the secondary eddies may be characteristic of internal separated flows.

The motion of an ellipsoid in tube flow at low Reynolds numbers

1996 ◽  
Vol 324 ◽  
pp. 287-308 ◽  
Author(s):  
Masako Sugihara-Seki
Keyword(s):  
Initial Conditions ◽  
Flow Direction ◽  
Major Axis ◽  
Oblate Spheroid ◽  
Reynolds Numbers ◽  
Prolate Spheroid ◽  
Stable Configuration ◽  
Axis Ratio ◽  
Low Reynolds Numbers ◽  
Freely Suspended

The motion of a rigid ellipsoidal particle freely suspended in a Poiseuille flow of an incompressible Newtonian fluid through a narrow tube is studied numerically in the zero-Reynolds-number limit. It is assumed that the effect of inertia forces on the motion of the particle and the fluid can be neglected and that no forces or torques act on the particle. The Stokes equation is solved by a finite element method for various positions and orientations of the particle to yield the instantaneous velocity of the particle as well as the flow field around it, and the particle trajectories are determined for different initial configurations. A prolate spheroid is found to either tumble or oscillate in rotation, depending on the particle–tube size ratio, the axis ratio of the particle, and the initial conditions. A large oblate spheroid may approach asymptotically a steady, stable configuration, at which it is located close to the tube centreline, with its major axis slightly tilted from the undisturbed flow direction. The motion of non-axisymmetric ellipsoids is also illustrated and discussed with emphasis on the effect of the particle shape and size.

Analytical Investigation of the Effect of Thermal Dispersion on Forced Convection in Heterogeneous Porous Media

2001 ◽  
Author(s):  
A. V. Kuznetsov
Keyword(s):  
Porous Media ◽  
Nusselt Number ◽  
Forced Convection ◽  
Boundary Layers ◽  
Solid Wall ◽  
Reynolds Numbers ◽  
Analytical Investigation ◽  
Heterogeneous Porous Media ◽  
Thermal Dispersion ◽  
Energy Equations

Abstract This paper presents a new analytical solution of a problem of forced convection in a heterogeneous channel filled with two different layers of isotropic porous media. The Brinkman-Forchheimer-extended Darcy equation is utilized to describe the fluid flow in the porous layers, and the effect of transverse thermal dispersion is accounted for in the energy equations. Three momentum boundary layers are identified in the channel: a boundary layer at the solid wall and two boundary layers at the interface between the porous media. The dependence of the Nusselt number on the Darcy numbers, Forchheimer coefficients, and particle Reynolds numbers in different parts of the channel is investigated. This study demonstrates that thermal dispersion has a strong effect on the Nusselt number in the channel for large particle Reynolds numbers.

Effects of Axis Ratio on the Vortex-Induced Vibration and Energy Harvesting of Rhombus Cylinder

2014 ◽  
Author(s):  
Li Zhang ◽  
Heng Li ◽  
Lin Ding
Keyword(s):  
Wide Band ◽  
Reynolds Numbers ◽  
Mechanical Power ◽  
Navier Stokes ◽  
Axis Ratio ◽  
Vortex Induced Vibrations ◽  
Mechanical Power Output ◽  
Wake Patterns ◽  
Wake Modes ◽  
High Reynolds

The vortex-induced vibrations of a rhombus cylinder are investigated using two-dimensional unsteady Reynolds-Averaged Navier-Stokes simulations at high Reynolds numbers ranging from 10,000 to 120,000. The rhombus cylinder is constrained to oscillate in the transverse direction, which is perpendicular to the flow velocity direction. Three rhombus cylinders with different axis ratio (AR=0.5, 1.0, 1.5) are considered for comparison. The simulation results indicate that the vibration response and the wake modes are dependent on the axis ratio of the rhombus cylinder. The amplitude ratios are functions of the Reynolds numbers. And as the AR increases, higher peak amplitudes can be made over a significant wide band of Re. On the other hand, a narrow lock-in area is observed for AR=0.5 and AR=1.5 when 30,000<Re<50,000, but the frequency ratio of AR=1.0 monotonically increases at a nearly constant slope in the whole Re range. The vortex shedding mode is always 2S mode in the whole Re range for AR=0.5. However, the wake patterns become diverse with the increasing of Re for AR=1.0 and 1.5. In addition, the mechanical power output of each oscillating rhombus cylinder is calculated to evaluate the efficiency of energy transfer in this paper. The theoretical mechanical power P between water and a transversely oscillating cylinder is achieved. On the base of analysis and comparison, the rhombus cylinder with AR=1.0 is more suitable for harvesting energy from fluid.

scholarly journals A Pore-Scale Investigation of the Transient Response of Forced Convection in Porous Media to Inlet Ramp Inputs

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Rabeeah Habib ◽  
Bijan Yadollahi ◽  
Nader Karimi
Keyword(s):  
Reynolds Number ◽  
Porous Media ◽  
Forced Convection ◽  
Transient Response ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Pore Scale ◽  
Staggered Arrangement ◽  
Energy Equations ◽  
Convection In Porous Media

Abstract This paper investigates the transient response of forced convection of heat in a reticulated porous medium through taking a pore-scale approach. The thermal system is subject to a ramp disturbance superimposed on the entrance flow temperature/velocity. The developed model consisted of ten cylindrical obstacles aligned in a staggered arrangement with set isothermal boundary conditions. A few types of fluids, along with different values of porosity and Reynolds number, are considered. Assuming a laminar flow, the unsteady Navier Stokes and energy equations are solved numerically. The temporally developing flow and temperature fields as well as the surface-averaged Nusselt numbers are used to explore the transient response of the system. Also, a response lag ratio (RLR) is defined to further characterize the transient response of the system. The results reveal that an increase in amplitude increases the RLR. Nonetheless, an increase in ramp duration decreases the RLR, particularly for high-density fluids. Interestingly, it is found that the Reynolds number has almost negligible effects upon RLR. This study clearly reflects the importance of conducting pore-scale analyses for understanding the transient response of heat convection in porous media.

Effects of Important Parameters on the Transition from Forced to Mixed Convection Flow in a Square Cavity

2021 ◽  
Vol 406 ◽  
pp. 36-52
Author(s):  
Sofiane Boulkroune ◽  
Omar Kholai ◽  
Brahim Mahfoud
Keyword(s):  
Reynolds Number ◽  
Prandtl Number ◽  
Mixed Convection ◽  
Forced Convection ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Convection Flow ◽  
Square Cavity ◽  
Left Wall ◽  
Energy Equations

Combined free and forced convection in a square cavity filled with a viscous fluid characterized by a small Prandtl number is studied numerically. The left wall is moving with a constant velocity v and is maintained at a local cold temperature Tc, while the right wall is fixed and maintained at a local hot temperature Th (Tc <Th). The top and bottom walls of the cavity is assumed to be adiabatic. The governing Navier-Stokes, and energy equations along with appropriate boundary conditions are solved using the finite-volume method. The flow and temperature fields are presented by stream function and isotherms, respectively. The effects of important parameters such as Reynolds number, Prandtl number, and Grashof number on the transition from forced convection to mixed convection are investigated. Results indicate that increasing Reynolds number results to fluid acceleration and, thus, to flow transition. Results also show that Grashof and Prandtl's numbers influenced the conditions for the transition to the mixed convection regime.

A Numerical Study of Unsteady Laminar Forced Convection From a Circular Cylinder

1976 ◽  
Vol 98 (2) ◽  
pp. 303-307 ◽  
Author(s):  
P. C. Jain ◽  
B. S. Goel
Keyword(s):  
Nusselt Number ◽  
Circular Cylinder ◽  
Forced Convection ◽  
Stokes Equations ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Laminar Forced Convection ◽  
Good Agreement

A numerical investigation of an unsteady laminar forced convection from a circular cylinder is presented. The Navier-Stokes equations and the energy equation for an unsteady incompressible fluid flow are solved by the finite difference method. The results are obtained at Reynolds numbers 100 and 200. The temperature field around the cylinder is obtained throughout the region of computation and is shown by isotherms at different times. The variations of the local Nusselt number around the cylinder at different times are computed and shown by graphs. The mean Nusselt number and the Strouhal number are also calculated. The computed results are compared with the other available experimental and theoretical results and are found to be in good agreement with them.

Numerical Investigation of Flow Field and Heat Transfer in Cross-Corrugated Ducts

1999 ◽  
Vol 121 (2) ◽  
pp. 314-321 ◽  
Author(s):  
H. Blomerius ◽  
C. Ho¨lsken ◽  
N. K. Mitra
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Critical Reynolds Number ◽  
Wave Length ◽  
Reynolds Numbers ◽  
Sine Wave ◽  
Transitional Flow ◽  
Navier Stokes ◽  
Flow Oscillations ◽  
Energy Equations

Flow field and heat transfer in sine-wave crossed-corrugated ducts have been investigated by numerical solution of the Navier-Stokes and energy equations in the laminar and transitional flow regime between Re = 170 and 2000. The ratio of the corrugation wave length λ* to amplitude a* has been varied between 7 and 10. The angle of the corrugation of the neighboring plates has been kept fixed at 45 deg. Results show that the critical Reynolds number for self-sustained flow oscillations is about 240. For Reynolds numbers larger than 1000, the Nusselt number and the friction factor are nearly independent of the dimensionless wavelength. Computational results compare well with available experimental results.

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