Flow over a cylinder
AIM:
To simulate the flow over a cylinder for the conditions shown in the video.
- To calculate the baseline case Reynolds number.
- Re = rho*U_inlet*D/mu
- D = cylinder diameter
- mu = dynamic viscosity
- rho = density
- To run a baseline simulation and then calculate the Reynolds number. Then increase the Reynolds number by a factor of 20%, 40%, and 100% then run the transient flow simulation.
- To simulation end time should be calculated properly
- To create animations for pressure-velocity for all the three Reynolds number.
PROCEDURE:
A cylinder of the following dimensions is made
L=0.05m
D=0.08m
A computational domain of length 0.5m for external flow is created using flow wizard.
For Air
Re=1.225kg/m^3
mu=1.21x10^-3
v=15m/s
A time dependent sudy with total analysis time 0.1 sec and 0.01 sec
A cut plot is created a the midle of the cylinder parallel to the front plane.
The simulation is run and animation is created for the followiing conditions.
Animation is created byresults->animation->insert->animation wizard opens
In that time is given as 10 seconds, revolve option is left unchecked, scenario option is checked and results are plotted uniformly for a duration of 0.01s.
using the formula and dat the values of velocity for Reynolds number by a factor of 20%, 40%, and 100% are found out.
Simulation end time (T)=2(lengtgh of computational domain/velocity)
@v=15m/s ->Re=81215.46 , T=0.066
- Velocity plot
- Pressure plot
@120%Re(97458.5635)-> v=18m/s , T=0.0555
- Velocity plot
- Pressure plot
@140%Re(113701.657)-> v=21m/s , T=0.0476
- Velocity plot
- Pressure plot
@200%Re(162430.939)-> v=30m/s , T=0.0333
- Velocity plot
- Pressure plot
INFERENCE:
When air flowing through the x axis hits the surface of the cylinder a high pressure region and velocity decreases at that region.
The velocity increases and is at its maximum at the the top and bottom surface as a low pressure region is created there.
At the back region which is shielded by the cylinder the velocity is minimum