Flow over a cylinder
AIM: to carry out fluid flow simulation over the cylinder.
Objective:
To analyse the fluid flow, providing different conditions.
To get acknowledge about the Transient simulation(time dependent).
Given Data:
The Cylinder dimensions are given as follows:
- The Diameter of cylinder = 0.01 m
- The length of cylinder =0.05 m
- The fluid velocity = 10 m/s flowing at positive x-axis.
- The total time for simulation = 0.1s
- The step in simulation = 0.01s
- The Fluid used for simulation = Air
- The density of air = 1.255 kg/'m^3'
- The viscosity of air = 1.81 × 10-5 kg/(m·s)
Modelling:
- To model the cylinder we start drawing a circle in the front plane, assign the diameter = 0.04 m or radius = 0.02 m.
- Then extrude it upto 0.05 m.
- Here, we have completed the modelling.
Simulation:
- To have a simulation we will use the wizard option, then add Air as fluid and put initial condition velocity at x axis =10m/s.
- Then create a global mesh, put the mesh option in automatic mode and mesh refinement equal to 3.
- Here, we are good to run the simulation.
- To know what we have obtain by running simulation add a cut plot.
- Add a cut plot in the result option, align the cut plot to the central plane of the cylinder manually.
- Also in the cut plot option, we will select the velocity.
- After clicking tick mark, we will get the fluid flow.
The Total Cells for this mesh found to be 40,876.
The Iterations that the simulation has performed is 79.
It has taken 1:44 sec to complete the simulation.
For the Fluid flow, the velocity obtained would be similar to this:
For the Fluid flow, the pressure plot obtained would be similar to this:
This is the our first simulation, so we have named this as a baseline simulation.
We would carry out the parametric study and compare it with this baseline simulation.
We will increase the reynolds number for the parametric study, therby we will increase the fluid velocity.
Before, carrying out the parametric study, we need to calculate the reynolds number for the baseline simulation & we have to increase it by 20, 40 & 100 times for the parametric study.
Calculation of Reynolds Number:
For this baseline simulation,
We have inlet velocity is 10 m/s & the fluid is taken as air.
So, according to reynolds number formula (Re) = 1.225*10*0.04 / 1.81 × 10-5
Therefore, the Reynolds number is found to be equal to 27072.
Now, we will increase the reynolds number by 20%, 40% & 100% for our parametric study.
Therefore,
(Re1) = 32486
(Re2) = 34901
(Re3) = 54144
Therefore, solving inlet velocity to the corresponding Reynolds number, we get:
(V1) = 12 m/s
(V2) = 12.89 m/s = 13 m/s
(V3) = 20.001 m/s = 20 m/s
Parametric Study of the Fluid Flow:
To do a parametric analysis, right click on the project & select new parametric study.
It will popup a screen at bottom.
In this window, we will add the input conditions, variables such as the dicrete values of velocity as we have calculated earlier V1, V2 & V3.
In the scenario, we will add the cut plots of velocity & pressure.
But here I'm not using the parametric study.
I'm using new project on the same model & changing the inlet velocity & plotting new velocity & Pressure plot in the plane middle of the cyinder.
Case:1 When the fluid velocity V1 is 12 m/s
The Velocity Plot for the fluid Velocity V1 would be look like this;
Similarly, the pressure plot for the fluid velocity V1 would look similar to this:
Case:2 When the inlet velocity is 13 m/s.
The Velocity Plot for the fluid Velocity V1 would be look like this;
Similarly, the pressure plot for the fluid velocity V2 would look similar to this:
Case:3 When the inlet velocity is 20 m/s
The Velocity Plot for the fluid Velocity V3 would be look like this;
Similarly, the pressure plot for the fluid velocity V3 would look similar to this:
Results:
The velocity boundary layer form at velocities V1 & V3 are much similar in manner.
The Pressure increases with the increase in the velocity.
Conclusion:
We have obtained the velocity & pressure plot for three different Fluid velocity, for a fluid flowing over a cylinder.
Animation Link for the fluid flowing over the Cylinder:
The Velocity Plot Animation:
The Pressure Plot Animation: