2010
17
2
2
0
http://scientiairanica.sharif.edu/3250.html
Comparing Sloshing Phenomena in a Rectangular Container with and without a Porous Medium Using Explicit Nonlinear 2D BEMFDM
2
2
The sloshing phenomena in a partially lled tank can aect its stability. Modications of
tank instability due to the movement of the tank carrier, are key design points for the stability of a carrier.
Even though the sloshing phenomenon has already been investigated using the BEMFDM technique, the
research in this paper covers this phenomenon in a porous media, which is new in 2D coordinates. For
this purpose, a Laplace equation has been used for potential
ow, and kinematic and dynamic boundary
conditions have been applied to the free surface. Also, a formulation has been developed for a free surface
in porous media. BEM has been used for solving the governing equation and FDM discretization has been
used for kinematic and dynamic free surface boundary conditions and for time marching. Theoretical
results have been veried with experimental data collected in this study. The results show an acceptable
agreement between theory and experiment, and the rapid damping property in the sloshing phenomena by
using porous material in the water, as expected. Also, these results illustrate that the derived formula in
this research are applicable and true.
2
The sloshing phenomena in a partially lled tank can aect its stability. Modications of
tank instability due to the movement of the tank carrier, are key design points for the stability of a carrier.
Even though the sloshing phenomenon has already been investigated using the BEMFDM technique, the
research in this paper covers this phenomenon in a porous media, which is new in 2D coordinates. For
this purpose, a Laplace equation has been used for potential
ow, and kinematic and dynamic boundary
conditions have been applied to the free surface. Also, a formulation has been developed for a free surface
in porous media. BEM has been used for solving the governing equation and FDM discretization has been
used for kinematic and dynamic free surface boundary conditions and for time marching. Theoretical
results have been veried with experimental data collected in this study. The results show an acceptable
agreement between theory and experiment, and the rapid damping property in the sloshing phenomena by
using porous material in the water, as expected. Also, these results illustrate that the derived formula in
this research are applicable and true.
Keywords: Boundary Element Method (BEM); Finite Dierence Method (FDM); Porous media;
Potential
ow; Liquid free surface.
0
0


M.
Ghodsi Hassanabad
Department of Mechanical Engineering,Sharif University of Technology
Iran
gkueprxj@scientiaunknown.non


M.
Abbaspour
Department of Mechanical Engineering,Sharif University of Technology
Iran
mabbaspour@jamejam.net
Boundary Element Method (BEM)
Finite Dierence Method (FDM)
porous media
Potential ow
Liquid free surface
http://scientiairanica.sharif.edu/3251.html
On the Relationship Between Unsteady Forces and Shock Angles on a Pitching Airplane Model
2
2
series of supersonic visualization tests were performed on an airplane model in both
static and dynamic pitching cases. After image processing, the wave angles originating from dierent
parts of the model were carefully measured and averaged over several oscillation cycles. These ndings
were then compared with the corresponding normal force under similar conditions. The results reveal a
hysteresis loop in variations of the model shock angles with instantaneous angles of attack during upstroke
and downstroke motions. In comparison with the normal force hysteresis loop, it has been found that
there is an interesting relationship between the shape of the hysteresis loop of the shock angle and the
corresponding loop observed in the normal force data. Further, the oscillation frequency has been shown
to have similar eects on both shock angle and aerodynamic force variations with the instantaneous angle
of attack.
2
series of supersonic visualization tests were performed on an airplane model in both
static and dynamic pitching cases. After image processing, the wave angles originating from dierent
parts of the model were carefully measured and averaged over several oscillation cycles. These ndings
were then compared with the corresponding normal force under similar conditions. The results reveal a
hysteresis loop in variations of the model shock angles with instantaneous angles of attack during upstroke
and downstroke motions. In comparison with the normal force hysteresis loop, it has been found that
there is an interesting relationship between the shape of the hysteresis loop of the shock angle and the
corresponding loop observed in the normal force data. Further, the oscillation frequency has been shown
to have similar eects on both shock angle and aerodynamic force variations with the instantaneous angle
of attack.
Keywords: Hysteresis; Pitching motion; Vortex bursting; Reduced frequency; Schlieren; Upstroke.
0
0


A.R.
Davari
Department of Aerospace Engineering,Sharif University of Technology
Iran
email@email.com


M. R.
Soltani
Department of Aerospace Engineering,Sharif University of Technology
Iran
jzufniwp@scientiaunknown.non
Hysteresis
Pitching motion
Vortex bursting
Reduced frequency
Schlieren
Upstroke
http://scientiairanica.sharif.edu/3252.html
ThreeDimensional Simulation of Turbulent Flow in 3Sub Channels of a VVER1000 Reactor
2
2
In this study, the
uid dynamics and convective heat transfer for turbulent
ows through
a 3sub channel of a rod bundle, which is representative of those used in VVER1000, are examined.
The rod bundle is constructed from parallel rods in a hexagonal array. The rods are on constant pitch
by spacer grids spaced axially along the rod bundle. The geometry details of the bundle and heat
ux
from the fuel rod are similar to that of the Iranian nuclear reactor under construction. A numerical
study using Computational Fluid Dynamics (CFD) was carried out to estimate the
ow eld, pressure
loss and heat transfer coecients in spacer grids and rod bundles. Turbulence has been modeled using the
k ???? " turbulence model. At a distance of 2Dh from the beginning of the spacer grids, in the direction of
ow, because
uid enthalpy and Nusselt numbers have maximum and minimum values, respectively, the
probability of nucleate boiling (PNB) is much higher, and a two phase
ow will occur. Predicted results
are found to be in close agreement with those of the experimental results reported in the literature.
2
In this study, the
uid dynamics and convective heat transfer for turbulent
ows through
a 3sub channel of a rod bundle, which is representative of those used in VVER1000, are examined.
The rod bundle is constructed from parallel rods in a hexagonal array. The rods are on constant pitch
by spacer grids spaced axially along the rod bundle. The geometry details of the bundle and heat
ux
from the fuel rod are similar to that of the Iranian nuclear reactor under construction. A numerical
study using Computational Fluid Dynamics (CFD) was carried out to estimate the
ow eld, pressure
loss and heat transfer coecients in spacer grids and rod bundles. Turbulence has been modeled using the
k ???? " turbulence model. At a distance of 2Dh from the beginning of the spacer grids, in the direction of
ow, because
uid enthalpy and Nusselt numbers have maximum and minimum values, respectively, the
probability of nucleate boiling (PNB) is much higher, and a two phase
ow will occur. Predicted results
are found to be in close agreement with those of the experimental results reported in the literature.
Keywords: Sub channel; Rod bundle; Spacer grid; Computational Fluid Dynamics (CFD); Turbulent
ow; Nusselt number.
0
0


B.
Firoozabadi
Department of Mechanical Engineering,Sharif University of Technology
Iran
email@email.com


H.
Ganjiani
Department of Mechanical Engineering,BUET
Iran
tvwwpuyv@scientiaunknown.non
Sub channel
Rod bundle
Spacer grid
Computational fluid dynamics (CFD)
Turbulent ow
Nusselt number
http://scientiairanica.sharif.edu/3253.html
Dynamic Response of Floating Wind Turbine
2
2
Like other oshore structures,
oating wind turbines are subjected to stochastic wave and
wind loads that cause a dynamic response in the structures. Wind turbines should be designed for dierent
conditions, such as Operational and Survival conditions. In high sea states, the response can be quite
dierent from the operational condition. The present paper deals with coupled wave and wind induced
motion in harsh conditions, up to 15 m signicant wave height and 50 m/sec average wind speed. There
are several ways to deal with the dynamic response of
oating wind turbines. The Coupled Time domain
dynamic response analysis for a moored spar wind turbine subjected to wave and wind loads is carried
out using DeepC. DeepC is well known software for calculating the coupled dynamic response of moored
oating structures. The aerodynamic forces on a parked wind turbine are calculated, based on the strip
theory, and imported to the DeepC through a MATLAB interface. At each time step, the relative wind
velocity, based on the response of the structure, is calculated.
2
Like other oshore structures,
oating wind turbines are subjected to stochastic wave and
wind loads that cause a dynamic response in the structures. Wind turbines should be designed for dierent
conditions, such as Operational and Survival conditions. In high sea states, the response can be quite
dierent from the operational condition. The present paper deals with coupled wave and wind induced
motion in harsh conditions, up to 15 m signicant wave height and 50 m/sec average wind speed. There
are several ways to deal with the dynamic response of
oating wind turbines. The Coupled Time domain
dynamic response analysis for a moored spar wind turbine subjected to wave and wind loads is carried
out using DeepC. DeepC is well known software for calculating the coupled dynamic response of moored
oating structures. The aerodynamic forces on a parked wind turbine are calculated, based on the strip
theory, and imported to the DeepC through a MATLAB interface. At each time step, the relative wind
velocity, based on the response of the structure, is calculated.
Keywords: Oshore; Floating wind turbine; Stochastic dynamic response; Aerohydroelastic.
0
0


M.
Karimirad
Department of Mechanical Engineering,University of Wales Cardiff
Iran
komsfmqe@scientiaunknown.non
Oshore
Floating wind turbine
Stochastic dynamic response
Aerohydroelastic
http://scientiairanica.sharif.edu/3254.html
Maximum Dynamic Load Determination of Mobile Manipulators via Nonlinear Optimal Feedback
2
2
In this paper, a nonlinear optimal feedback control law is designed to nd the maximum
load carrying capacity of mobile manipulators for a given trajectory task. The optimal state feedback
law is given by the solution to the nonlinear HamiltonJacobiBellman (HJB) equation. An iterative
procedure is used to nd a sequence of approximate solutions of the HJB equation. This is done by solving
a sequence of Generalized HJB (GHJB) dierential equations. The Galerkin procedure is applied to nd
a numerical solution to the GHJB equation. Using this method, a nonlinear feedback is designed for
the mobile manipulator and, then, an algorithm is developed to nd the maximum payload. In mobile
base manipulators, the maximum allowable load is limited by their joint actuator capacity constraints,
nonholonomic constraints and redundancy that arise from base mobility and increased Dofs. To solve the
extra Dofs of the system, an extended Jacobian matrix and additional kinematic constraints are used. The
validity of the methodology is demonstrated via simulation for a twolink wheeled mobile manipulator and
linear tracked Puma arm and the results are discussed.
2
In this paper, a nonlinear optimal feedback control law is designed to nd the maximum
load carrying capacity of mobile manipulators for a given trajectory task. The optimal state feedback
law is given by the solution to the nonlinear HamiltonJacobiBellman (HJB) equation. An iterative
procedure is used to nd a sequence of approximate solutions of the HJB equation. This is done by solving
a sequence of Generalized HJB (GHJB) dierential equations. The Galerkin procedure is applied to nd
a numerical solution to the GHJB equation. Using this method, a nonlinear feedback is designed for
the mobile manipulator and, then, an algorithm is developed to nd the maximum payload. In mobile
base manipulators, the maximum allowable load is limited by their joint actuator capacity constraints,
nonholonomic constraints and redundancy that arise from base mobility and increased Dofs. To solve the
extra Dofs of the system, an extended Jacobian matrix and additional kinematic constraints are used. The
validity of the methodology is demonstrated via simulation for a twolink wheeled mobile manipulator and
linear tracked Puma arm and the results are discussed.
Keywords: Maximum payload; Manipulator; Optimal control; Closed loop controller; HJB.
0
0


M.
Irani
Research Center,Sharif University of Technology
Iran
yzmgiyud@scientiaunknown.non


M. H.
Korayem
Department of Mechanical Engineering,Iran University of Science and Technology
Iran
hkorayem@iust.ac.ir
Maximum payload
Manipulator
Optimal control
Closed loop controller
HJB
http://scientiairanica.sharif.edu/3255.html
Numerical Modeling of Transient Turbulent Gas Flow in a Pipe Following a Rupture
2
2
The transient
ow of a compressible gas generated in a pipeline after an accidental rupture
is studied numerically. The numerical simulation is performed by solving the conservation equations of an
axisymmetric, transient, viscous, subsonic
ow in a circular pipe including the breakpoint. The numerical
technique is a combined nite elementnite volume method applied on the unstructured grid. A modified
???? " model with a twolayer equation for the near wall region and compressibility correction is used to
predict the turbulent viscosity. The results show that, for example, after a time period of 0.16 seconds,
the pressure at a distance of 61.5 m upstream of the breakpoint reduces about 8%, while this value for
the downstream pressure located at the same distance from the rupture is about 14% at the same time.
Also, the mass
ow rate released from the rupture point will reach 2.4 times its initial value and become
constant when the sonic condition occurs at this point after 0.16 seconds. Also, the average pressure of
the rupture reduced to 60% of its initial value and remained constant at the same time and under the
same condition. The results are compared with available experimental and numerical studies for steady
compressible pipe
ow.
2
The transient
ow of a compressible gas generated in a pipeline after an accidental rupture
is studied numerically. The numerical simulation is performed by solving the conservation equations of an
axisymmetric, transient, viscous, subsonic
ow in a circular pipe including the breakpoint. The numerical
technique is a combined nite elementnite volume method applied on the unstructured grid. A modified
???? " model with a twolayer equation for the near wall region and compressibility correction is used to
predict the turbulent viscosity. The results show that, for example, after a time period of 0.16 seconds,
the pressure at a distance of 61.5 m upstream of the breakpoint reduces about 8%, while this value for
the downstream pressure located at the same distance from the rupture is about 14% at the same time.
Also, the mass
ow rate released from the rupture point will reach 2.4 times its initial value and become
constant when the sonic condition occurs at this point after 0.16 seconds. Also, the average pressure of
the rupture reduced to 60% of its initial value and remained constant at the same time and under the
same condition. The results are compared with available experimental and numerical studies for steady
compressible pipe
ow.
Keywords: Transient compressible
ow; Gas pipeline; Numerical modeling; Sudden rupture; Combined
nite elementnite volume method.
0
0


A.
NouriBorujerdi
Department of Mechanical Engineering,Sharif University of Technology
Iran
anouri@sharif.edu


M.
ZiaeiRad
Department of Mechanical Engineering,Sharif University of Technology
Iran
dluxnvie@scientiaunknown.non
Transient compressible ow
Gas pipeline
Numerical Modeling
Sudden rupture
Combined nite elementnite volume method
http://scientiairanica.sharif.edu/3256.html
Eects of Canard Position on Wing Surface Pressure
2
2
A series of wind tunnel tests were performed to study the eects of a canard and its
position on the downstream
oweld over the wing surface. The wing surface pressure was measured
for both canardo and canardon congurations. In addition, the canard position eects on the wing
were investigated at dierent angles of attack. The canard was installed at three vertical positions and
at two dierent horizontal distances from the wing apex. The results show a remarkable increase in the
wing suction peak for the canardon congurations. At low to moderate angles of attack, among the
various congurations examined in the present experiments, the midcanard conguration developed a
higher suction on the wing while, at high angles of attack, the uppercanard was found to induce the most
favorable
ow eld on the wing. In addition, higher suctions were achieved on the wing at moderate to
high angles of attack, as the wingcanard distance was increased.
2
A series of wind tunnel tests were performed to study the eects of a canard and its
position on the downstream
oweld over the wing surface. The wing surface pressure was measured
for both canardo and canardon congurations. In addition, the canard position eects on the wing
were investigated at dierent angles of attack. The canard was installed at three vertical positions and
at two dierent horizontal distances from the wing apex. The results show a remarkable increase in the
wing suction peak for the canardon congurations. At low to moderate angles of attack, among the
various congurations examined in the present experiments, the midcanard conguration developed a
higher suction on the wing while, at high angles of attack, the uppercanard was found to induce the most
favorable
ow eld on the wing. In addition, higher suctions were achieved on the wing at moderate to
high angles of attack, as the wingcanard distance was increased.
Keywords: Canard; Delta wing; Downwash; Leading edge vortex.
0
0


A.R.
Davari
Department of Aerospace Engineering,Sharif University of Technology
Iran
email@email.com


M. R.
Soltani
Department of Aerospace Engineering,Sharif University of Technology
Iran
jzufniwp@scientiaunknown.non


F.
Askari
Department of Aerospace Engineering,Sharif University of Technology
Iran
xheorpck@scientiaunknown.non


A.
Nayebzadeh
Department of Aerospace Engineering,Sharif University of Technology
Iran
abyjhith@scientiaunknown.non
Canard
Delta wing
Downwash
Leading edge vortex