Download College of Engineering

Republic of Iraq
Ministry of Higher Education
and Scientific Research
Babylon University
College of Engineering
Dept. of Mech. Eng.
Numerical Analysis Of Heat
Transfer And Fluid Flow Over A
Rigidly Vibrating Cylinder In
Cross Flow
A THESIS SUBMITTED TO THE COLLEGE OF ENGINEERING OF
THE UNIVERSITY OF BABYLON IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE
DEGREE OF MASTER OF
SCIENCE IN MECHANICAL
ENGINEERING
By
MOHSEN GAWY HAMZA AL-GUBOURY
B.Sc., 2003
2007 A.D.
1428 Hijry
Abstract
A numerical simulation is performed to predict the flow structures and heat
transfer characteristics of a heated oscillating cylinder in across flow and air
forced convection. The variations of the flow and thermal fields classified into a
class of moving boundary problems. The fluid is assumed to be incompressible,
viscous, two dimensional, laminar unsteady flow. The cylinder have constant
wall temperature condition.
The Body Fitted Coordinate system(B.F.C) has been used with the time
dependent grid generation technique because of the complexity of physical shape
and moving boundary with time of this study since this method enable us to solve
the flow equations around the complex bodies without the need to approximate
or interpolate at the outside limits of the body, then an internal grid has been
generated by solving two elliptic differential equations.
Vorticity-Stream function model has been used in this study. In this model,
the governing equations consist of parabolic vorticity and energy equations which
are solved by time marching (explicit) method and elliptic stream function
equation which is solved by the relaxation method. These equations are solved by
using finite difference discretization.
The moving interfaces between the fluid and cylinder have been considered.
In fact, to overcome the effect of moving boundary, due to the cylinder
oscillation, update the grid at each time step with a new locations and entering a
new terms to the vorticity and the energy transport equations, these terms are
treating the effects of this movement of the grid on the computational domain.
The study covers the range of Reynolds numbers (80 to 600), reduced
frequency (0.0 to 0.7) and amplitude ratio(0.0 to 0.9). Single value of Prandtl
number(0.7) and three types of oscillation, transverse, inline and orbital, and also
stationary (fixed) cylinder are used.
Heat transfer is greatly affected by the oscillation of the cylinder. It was found
that the average of local Nusselt number in some cases are enhanced by
(37%,57% and 64%) for the
transverse, inline and the orbital oscillation
respectively. The maximum local Nusselt number for the same cases above are
enhanced by (64%, 71% and 78%) for the transverse, inline and the orbital
oscillation respectively.
On the other hand, the oscillation significantly affected the heat and
momentum transfer characteristics of the air flow over the cylinder. The
oscillation affects on density of stream line, isotherm and number of vortex
shedding per cycle. The local skin friction coefficient is enhanced in some cases
by (63%,52% and 75%) for the
transverse, inline and orbital oscillation
respectively. The numerical predictions have been compared with existing data,
and good agreement has been found.