Abstract: Hypersonic flows around spatial vehicles during their reentry phase in planetary atmospheres are characterized by intense aerothermodynamics phenomena. The aim of this work is to analyze high temperature flows around an axisymmetric blunt body taking into account chemical and vibrational non-equilibrium for air mixture species and the no slip condition at the wall. For this purpose, the Navier-Stokes equations system is resolved by the finite volume methodology to determine the flow parameters around the axisymmetric blunt body especially at the stagnation point and in the boundary layer along the wall of the blunt body. The code allows the capture of shock wave before a blunt body placed in hypersonic free stream. The numerical technique uses the Flux Vector Splitting method of Van Leer. CFL coefficient and mesh size level are selected to ensure the numerical convergence.
Abstract: The paper aims at investigating influence of medium
capacity on linear adsorbed solute dispersion into chemically
heterogeneous fixed beds. A discrete chemical heterogeneity
distribution is considered in the one-dimensional advectivedispersive
equation. The partial differential equation is solved using
finite volumes method based on the Adam-Bashforth algorithm.
Increased dispersion is estimated by comparing breakthrough curves
second order moments and keeping identical hydrodynamic
properties. As a result, dispersion increase due to chemical
heterogeneity depends on the column size and surprisingly on the
solid capacity. The more intense capacity is, the more important
solute dispersion is. Medium length which is known to favour this
effect vanishing according to the linear adsorption in fixed bed seems
to create nonmonotonous variation of dispersion because of the
heterogeneity. This nonmonotonous behaviour is also favoured by
high capacities.
Abstract: In this paper, a two-dimensional (2D) numerical
model for the tidal currents simulation in Persian Gulf is presented.
The model is based on the depth averaged equations of shallow water
which consider hydrostatic pressure distribution. The continuity
equation and two momentum equations including the effects of bed
friction, the Coriolis effects and wind stress have been solved. To
integrate the 2D equations, the Alternative Direction Implicit (ADI)
technique has been used. The base of equations discritization was
finite volume method applied on rectangular mesh. To evaluate the
model validation, a dam break case study including analytical
solution is selected and the comparison is done. After that, the
capability of the model in simulation of tidal current in a real field is
represented by modeling the current behavior in Persian Gulf. The
tidal fluctuations in Hormuz Strait have caused the tidal currents in
the area of study. Therefore, the water surface oscillations data at
Hengam Island on Hormoz Strait are used as the model input data.
The check point of the model is measured water surface elevations at
Assaluye port. The comparison between the results and the
acceptable agreement of them showed the model ability for modeling
marine hydrodynamic.
Abstract: In mechanical and environmental engineering, mixed
convection is a frequently encountered thermal fluid phenomenon
which exists in atmospheric environment, urban canopy flows, ocean
currents, gas turbines, heat exchangers, and computer chip cooling
systems etc... . This paper deals with a numerical investigation of
mixed convection in a vertical heated channel. This flow results from
the mixing of the up-going fluid along walls of the channel with the
one issued from a flat nozzle located in its entry section. The fluiddynamic
and heat-transfer characteristics of vented vertical channels
are investigated for constant heat-flux boundary conditions, a
Rayleigh number equal to 2.57 1010, for two jet Reynolds number
Re=3 103 and 2104 and the aspect ratio in the 8-20 range. The system
of governing equations is solved with a finite volumes method and an
implicit scheme. The obtained results show that the turbulence and
the jet-wall interaction activate the heat transfer, as does the drive of
ambient air by the jet. For low Reynolds number Re=3 103, the
increase of the aspect Ratio enhances the heat transfer of about 3%,
however; for Re=2 104, the heat transfer enhancement is of about
12%. The numerical velocity, pressure and temperature fields are
post-processed to compute the quantities of engineering interest such
as the induced mass flow rate, and average Nusselt number, in terms
of Rayleigh, Reynolds numbers and dimensionless geometric
parameters are presented.
Abstract: Hypersonic flows around spatial vehicles during their
reentry phase in planetary atmospheres are characterized by intense
aerothermal phenomena. The aim of this work is to analyze high
temperature flows around an axisymmetric blunt body taking into
account chemical and vibrational non-equilibrium for air mixture
species. For this purpose, a finite volume methodology is employed
to determine the supersonic flow parameters around the axisymmetric
blunt body, especially at the stagnation point and along the wall of
spacecraft for several altitudes. This allows the capture shock wave
before a blunt body placed in supersonic free stream. The numerical
technique uses the Flux Vector Splitting method of Van Leer. Here,
adequate time stepping parameter, along with CFL coefficient and
mesh size level are selected to ensure numerical convergence, sought
with an order of 10-8
Abstract: Numerical study of a plane jet occurring in a vertical
heated channel is carried out. The aim is to explore the influence of
the forced flow, issued from a flat nozzle located in the entry section
of a channel, on the up-going fluid along the channel walls. The
Reynolds number based on the nozzle width and the jet velocity
ranges between 3 103 and 2.104; whereas, the Grashof number based
on the channel length and the wall temperature difference is 2.57
1010. Computations are established for a symmetrically heated
channel and various nozzle positions. The system of governing
equations is solved with a finite volumes method. The obtained
results show that the jet-wall interactions activate the heat transfer,
the position variation modifies the heat transfer especially for low
Reynolds numbers: the heat transfer is enhanced for the adjacent
wall; however it is decreased for the opposite one. The numerical
velocity and temperature fields are post-processed to compute the
quantities of engineering interest such as the induced mass flow rate,
and the Nusselt number along the plates.