**Commenced**in January 2007

**Frequency:**Monthly

**Edition:**International

**Paper Count:**17

# Search results for: Buoyancy force

##### 17 Steady State Natural Convection in Vertical Heated Rectangular Channel between Two Vertical Parallel MTR-Type Fuel Plates

**Authors:**
Djalal Hamed

**Abstract:**

**Keywords:**
Buoyancy force,
friction force,
friction factor,
MTR-type fuel,
natural convection,
vertical heated rectangular channel.

##### 16 Numerical Solution of Transient Natural Convection in Vertical Heated Rectangular Channel between Two Vertical Parallel MTR-Type Fuel Plates

**Authors:**
Djalal Hamed

**Abstract:**

The aim of this paper is to perform, by mean of the finite volume method, a numerical solution of the transient natural convection in a narrow rectangular channel between two vertical parallel Material Testing Reactor (MTR)-type fuel plates, imposed under a heat flux with a cosine shape to determine the margin of the nuclear core power at which the natural convection cooling mode can ensure a safe core cooling, where the cladding temperature should not reach a specific safety limits (90 °C). For this purpose, a computer program is developed to determine the principal parameters related to the nuclear core safety, such as the temperature distribution in the fuel plate and in the coolant (light water) as a function of the reactor core power. Throughout the obtained results, we noticed that the core power should not reach 400 kW, to ensure a safe passive residual heat removing from the nuclear core by the upward natural convection cooling mode.

**Keywords:**
Buoyancy force,
friction force,
friction factor,
finite volume method,
transient natural convection,
thermal hydraulic analysis,
vertical heated rectangular channel.

##### 15 MHD Mixed Convection in a Vertical Porous Channel

**Authors:**
B. Fersadou,
H. Kahalerras

**Abstract:**

**Keywords:**
Heat sources,
magnetic field,
mixed convection,
porous channel.

##### 14 Modeling and Simulation of Underwater Flexible Manipulator as Raleigh Beam Using Bond Graph

**Authors:**
Sumit Kumar,
Sunil Kumar,
Chandan Deep Singh

**Abstract:**

**Keywords:**
Bond graph modeling,
dynamics. modeling,
Rayleigh beam,
underwater robot.

##### 13 Investigation of Bubble Growth during Nucleate Boiling Using CFD

**Authors:**
K. Jagannath,
Akhilesh Kotian,
S. S. Sharma,
Achutha Kini U.,
P. R. Prabhu

**Abstract:**

**Keywords:**
Bubble growth,
computational fluid dynamics,
detachment diameter,
terminal velocity.

##### 12 New Insight into Fluid Mechanics of Lorenz Equations

**Authors:**
Yu-Kai Ting,
Jia-Ying Tu,
Chung-Chun Hsiao

**Abstract:**

New physical insights into the nonlinear Lorenz equations related to flow resistance is discussed in this work. The chaotic dynamics related to Lorenz equations has been studied in many papers, which is due to the sensitivity of Lorenz equations to initial conditions and parameter uncertainties. However, the physical implication arising from Lorenz equations about convectional motion attracts little attention in the relevant literature. Therefore, as a first step to understand the related fluid mechanics of convectional motion, this paper derives the Lorenz equations again with different forced conditions in the model. Simulation work of the modified Lorenz equations without the viscosity or buoyancy force is discussed. The time-domain simulation results may imply that the states of the Lorenz equations are related to certain flow speed and flow resistance. The flow speed of the underlying fluid system increases as the flow resistance reduces. This observation would be helpful to analyze the coupling effects of different fluid parameters in a convectional model in future work.

**Keywords:**
Galerkin method,
Lorenz equations,
Navier-Stokes
equations.

##### 11 Numerical Investigation of Nanofluid Based Thermosyphon System

**Authors:**
Kiran Kumar K,
Ramesh Babu Bejjam,
Atul Najan

**Abstract:**

A thermosyphon system is a heat transfer loop which operates on the basis of gravity and buoyancy forces. It guarantees a good reliability and low maintenance cost as it does not involve any mechanical pump. Therefore, it can be used in many industrial applications such as refrigeration and air conditioning, electronic cooling, nuclear reactors, geothermal heat extraction, etc. But flow instabilities and loop configuration are the major problems in this system. Several previous researchers studied that stabilities can be suppressed by using nanofluids as loop fluid. In the present study a rectangular thermosyphon loop with end heat exchangers are considered for the study. This configuration is more appropriate for many practical applications such as solar water heater, geothermal heat extraction, etc. In the present work, steady-state analysis is carried out on thermosyphon loop with parallel flow coaxial heat exchangers at heat source and heat sink. In this loop nanofluid is considered as the loop fluid and water is considered as the external fluid in both hot and cold heat exchangers. For this analysis onedimensional homogeneous model is developed. In this model, conservation equations like conservation of mass, momentum, energy are discretized using finite difference method. A computer code is written in MATLAB to simulate the flow in thermosyphon loop. A comparison in terms of heat transfer is made between water and nanofluid as working fluids in the loop.

**Keywords:**
Heat exchanger,
Heat transfer,
Nanofluid,
Thermosyphon loop.

##### 10 Thermophoresis Particle Precipitate on Heated Surfaces

**Authors:**
Rebhi A. Damseh,
H. M. Duwairi,
Benbella A. Shannak

**Abstract:**

This work deals with heat and mass transfer by steady laminar boundary layer flow of a Newtonian, viscous fluid over a vertical flat plate with variable surface heat flux embedded in a fluid saturated porous medium in the presence of thermophoresis particle deposition effect. The governing partial differential equations are transformed into no-similar form by using special transformation and solved numerically by using an implicit finite difference method. Many results are obtained and a representative set is displaced graphically to illustrate the influence of the various physical parameters on the wall thermophoresis deposition velocity and concentration profiles. It is found that the increasing of thermophoresis constant or temperature differences enhances heat transfer rates from vertical surfaces and increase wall thermophoresis velocities; this is due to favorable temperature gradients or buoyancy forces. It is also found that the effect of thermophoresis phenomena is more pronounced near pure natural convection heat transfer limit; because this phenomenon is directly a temperature gradient or buoyancy forces dependent. Comparisons with previously published work in the limits are performed and the results are found to be in excellent agreement.

**Keywords:**
Thermophoresis,
porous medium,
variable surface heat flux.

##### 9 Numerical Study of Laminar Mixed Convection Heat Transfer of a Nanofluid in a Concentric Annular Tube Using Two-Phase Mixture Model

**Authors:**
Roghayyeh Motallebzadeh,
Shahin Hajizadeh,
Mohammad Reza Ghasemi

**Abstract:**

Laminar mixed Convection heat transfer of a nanofluid with prescribed constant heat flux on the inner wall of horizontal annular tube has been studied numerically based on two-phase mixture model in different Rayleigh Numbers and Azimuth angles. Effects of applying of different volume fractions of Al_{2}O_{3} nanoparticles in water as a base fluid on hydrodynamic and thermal behaviors of the fluid flow such as axial velocity, secondary flow, temperature, heat transfer coefficient and friction coefficient at the inner and outer wall region, has been investigated. Conservation equations in elliptical form has been utilized and solved in three dimensions for a steady flow. It is observed that, there is a good agreement between results in this work and previously published experimental and numerical works on mixed convection in horizontal annulus. These particles cause to increase convection heat transfer coefficient of the fluid, meanwhile there is no considerable effect on friction coefficient.

**Keywords:**
Buoyancy force,
Laminar mixed convection,
Mixture model,
Nanofluid,
Two-phase.

##### 8 Sliding Mode Control of Autonomous Underwater Vehicles

**Authors:**
Ahmad Forouzan Tabar,
Mohammad Azadi,
Alireza Alesaadi

**Abstract:**

This paper describes a sliding mode controller for autonomous underwater vehicles (AUVs). The dynamic of AUV model is highly nonlinear because of many factors, such as hydrodynamic drag, damping, and lift forces, Coriolis and centripetal forces, gravity and buoyancy forces, as well as forces from thruster. To address these difficulties, a nonlinear sliding mode controller is designed to approximate the nonlinear dynamics of AUV and improve trajectory tracking. Moreover, the proposed controller can profoundly attenuate the effects of uncertainties and external disturbances in the closed-loop system. Using the Lyapunov theory the boundedness of AUV tracking errors and the stability of the proposed control system are also guaranteed. Numerical simulation studies of an AUV are included to illustrate the effectiveness of the presented approach.

**Keywords:**
Lyapunov stability,
autonomous underwater vehicle (AUV),
sliding mode controller,
electronics engineering.

##### 7 Effect of Buoyancy Ratio on Non-Darcy Mixed Convection in a Vertical Channel: A Thermal Non-equilibrium Approach

**Authors:**
Manish K. Khandelwal,
P. Bera,
A. Chakrabarti

**Abstract:**

**Keywords:**
buoyancy ratio,
mixed convection,
non-Darcy model,
thermal non-equilibrium

##### 6 Adaptive Neural Network Control of Autonomous Underwater Vehicles

**Authors:**
Ahmad Forouzantabar,
Babak Gholami,
Mohammad Azadi

**Abstract:**

**Keywords:**
Autonomous Underwater Vehicle (AUV),
Neural
Network Controller,
Composite Adaptation.

##### 5 Perfect Plastic Deformation of a Circular Thin Bronze Plate due to the Growth and Collapse of a Vapour Bubble

**Authors:**
M.T. Shervani-Tabar,
M. Rezaee,
E. Madadi Kandjani

**Abstract:**

Dynamics of a vapour bubble generated due to a high local energy input near a circular thin bronze plate in the absence of the buoyancy forces is numerically investigated in this paper. The bubble is generated near a thin bronze plate and during the growth and collapse of the bubble, it deforms the nearby plate. The Boundary Integral Equation Method is employed for numerical simulation of the problem. The fluid is assumed to be incompressible, irrotational and inviscid and the surface tension on the bubble boundary is neglected. Therefore the fluid flow around the vapour bubble can be assumed as a potential flow. Furthermore, the thin bronze plate is assumed to have perfectly plastic behaviour. Results show that the displacement of the circular thin bronze plate has considerable effect on the dynamics of its nearby vapour bubble. It is found that by decreasing the thickness of the thin bronze plate, the growth and collapse rate of the bubble becomes higher and consequently the lifetime of the bubble becomes shorter.

**Keywords:**
Vapour Bubble,
Thin Bronze Plate,
Boundary Integral
Equation Method.

##### 4 Simulation of Fluid Flow and Heat Transfer in Inclined Cavity using Lattice Boltzmann Method

**Authors:**
Arash Karimipour,
A. Hossein Nezhad,
E. Shirani,
A. Safaei

**Abstract:**

In this paper, Lattice Boltzmann Method (LBM) is used to study laminar flow with mixed convection heat transfer inside a two-dimensional inclined lid-driven rectangular cavity with aspect ratio AR = 3. Bottom wall of the cavity is maintained at lower temperature than the top lid, and its vertical walls are assumed insulated. Top lid motion results in fluid motion inside the cavity. Inclination of the cavity causes horizontal and vertical components of velocity to be affected by buoyancy force. To include this effect, calculation procedure of macroscopic properties by LBM is changed and collision term of Boltzmann equation is modified. A computer program is developed to simulate this problem using BGK model of lattice Boltzmann method. The effects of the variations of Richardson number and inclination angle on the thermal and flow behavior of the fluid inside the cavity are investigated. The results are presented as velocity and temperature profiles, stream function contours and isotherms. It is concluded that LBM has good potential to simulate mixed convection heat transfer problems.

**Keywords:**
gravity,
inclined lid driven cavity,
lattice Boltzmannmethod,
mixed convection.

##### 3 Dynamics of a Vapour Bubble inside a Vertical Rigid Cylinder with a Deposit Rib

**Authors:**
S. Mehran,
S. Rouhi,
F.Rouzbahani,
E. Haghgoo

**Abstract:**

**Keywords:**
Vapour bubble,
Vertical rigid cylinder,
Boundaryelement method.

##### 2 Dynamics of a Vapour Bubble inside a Vertical Rigid Cylinder in the Absence of Buoyancy Forces

**Authors:**
S. Mehran,
S. Rouhi,
F.Rouzbahani,
E. Haghgoo

**Abstract:**

**Keywords:**
Vapour bubble,
Vertical rigid cylinder,
Boundaryelement method,
Finite difference method,
Buoyancy forces.

##### 1 Numerical Study of Vertical Wall Jets: Influence of the Prandtl Number

**Authors:**
Amèni Mokni,
Hatem Mhiri,
Georges Le Palec,
Philippe Bournot

**Abstract:**

**Keywords:**
Forced convection,
Mixed convection,
Prandtl
number,
Wall jet.