Flow over a cylinder
Aim : 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.
Introduction :
Flow simulation is a form of computational fluid dynamics which digitally replicates flows in surface water or collection systems. Performing flow simulation allows for the prediction and analysis of how a flow might be impacted by complex geometry in an operational environment.
Basic theory on the simulation:
The Reynolds number is defined as the product of density times velocity times length divided by the viscosity coefficient. This is proportional to the ratio of inertial forces and viscous forces (forces resistant to change and heavy and gluey forces) in a fluid flow.
Entire case setup:
Model the cylinder of 0.02m diameter and 0.05 m length.
Creating a Project ,Click Flow Simulation, Project, Wizard. The project wizard guides you through the definition of a new SolidWorks Flow Simulation project.
Use all Defaults option. Take Air as Fluid and select external flow.
Creating a cut plot for velocity and pressure.
Creating the mesh and changing the global mesh as per requirements.
Run the study.
First creating a Baseline Simulation at Velocity = 1 m/s
Calculation of Reynolds number :
Taking , Density =1.2047 kg/m^3
Diameter = 0.02m
Dynamic viscosity =1.8205 kg/ms at 20 degree Celsius
So,Reynolds Number =1323.(For Baseline Study)
As Describe in the challenge that to increase the Reynolds number as factor of 20%,40%and 100%
|
|
Baseline Reynolds Number |
increase the Reynolds number as factor of |
New Reynolds number |
velocity |
Flow through time |
End Time |
|
Study1 |
1323 |
20% |
1587.6 |
1.21 |
0.14 |
0.29 |
|
Study2 |
1323 |
40% |
1852.2 |
1.4 |
0.125 |
0.25 |
|
Study3 |
1323 |
100% |
2546 |
2 |
0.09 |
0.18 |
Results :
Baseline Simulation :
Velocity Cut plot:
Pressure Cut plot :
Study1 Simulation :
Velocity Cut plot:
Pressure Cut plot :
Study2 Simulation :
Velocity Cut plot:
Pressure Cut plot :
Study3 Simulation :
Velocity Cut plot:
Pressure Cut plot :
Animation for Study1:
Velocity Cut plot: https://youtu.be/Ty47f2lEPKM
Pressure Cut plot :https://youtu.be/5ItkjgH2LAc
Observation and Conclusion :
- Inlet velocity in x direction increases with the increase in reynolds number, thus increasing the flow of air over the cylinder.
- It is observed that the high pressure is created on the surface facing the inlet velocity.
- The velocity variation in the above animations has different velocity profiles, when the velocity is larger the velocity profile is longer behind the cylinder surface.
- Velocity is approximately zero nearer to the cylinder surface .
- For higher values of the velocity waves are created behind the cylinder.