Since OPENFOAM does not work with 2D geometry hence to make a 2D analysis the side walls is taken as empty for 2D case

Since OPENFOAM does not work with 2D geometry
hence to make a 2D analysis the side walls is taken as
empty for 2D case. The inlet velocity for both the cases
are taken as uniform 24.5 i.e, fully developed velocity
profile is considered. The Reynolds number is calculated
based on the height of the cube and hence ReH is
considered as 65000.
For RANS simulation PIMPLEFOAM solver is used.
The turbulence model used is RAS using k-epsilon 2
equation unsteady model. The delta T is taken as 0.00001
and the solver ran for end time 0.1. For a Pentium III
processor with 4 GB RAM it took 26 hours to complete.
For LES simulation PISOFOAM solver is used. The
turbulence model used is LES with smagorinsky using
filter as cube root delta. The delta T is taken as 0.0001
and the solver ran for end time 0.7. For a Pentium III
processor with 4 GB RAM it took 70-72 hours to
complete.
At the end of the simulation all the results with respect to
various parameters are captured and they are compared
with each other for the prediction of turbulence. The
study is inclined to find the parameters like drag & lift
coefficients, energy spectrum and comparing with the
standard curves, velocity and pressure at various time
throughout the simulation, velocity and pressure contour,
q criteria etc.
The detailed results are put in the section III with various
graphs and their significance.
Fig 3 to 7 show the velocity profile for RANS model
at different points of x=0,0.04,-0.1,0.1&0.02 where
x=0 and x=0.04 give the front face of the cube and
the back face of the cube respectively Where as point
0.02 gives the mid of the top face of the resistance
and -0.1 and 0.01 give the upstream and downstream
respectively. From the first two plots it is quite
visible that initially the value is zero since the cube
face is given as wall and the no slip condition is
imposed and after the profile is changed with high
gradients and as it moves further in the direction of y
the gradient decreases and at last again moved to zero
at the top boundary. Because of the cube interference
this two shows this type of behaviour. For the
upstream point since there is no interference the
velocity profile is fully developed as in the inlet but
in the downstream though the point is far away
because of some kind of interference the profile is
not fully developed and hence it can be said that even
after some distance from the resistance the fluid
experience effect of obstacles before it goes fully
developed. For x=0.02 which is the point at the top of
the cube face it can be observed that the velocity
profile is almost developed but not from the bottom
of the domain rather from above the cube.
Fig 8 to 10 show the pressure profile in all three faces
of the cube for RANS. Fig 8 gives pressure profile
for front face of the resistance. The plot shows the
maximum pressure is nearly 575 m^2/s^2 and dthis
value is at the bottom of the cube and at the top
corner of the cube the value is almost negligible
.Also it can be seen that the the plot is initially at
constant value of 575 for almost 2/3rd of the cube
height and after that the value decreases and this is
because the stagnation point is almost upto a height
of 2/3rd of cube height from the base. Also in the
back face and at the top face a negative pressure
prevails which can be seen from the rest of the two
graphs which is because of creation of vortex and
eddies because of change in energy
3) Kinetic energy profile
Fig. 11. Kinetic energy at x=0
Fig. 12. Kinetic energy at x=0.04
Fig. 13. Kinetic energy at x=-0.1
Fig. 14. Kinetic energy at x=0.1