Flow over a cylinder
Flow simulation over cylinder
OBJECTIVE:
- To analyse the fluid flow over a cylinder by calculating Reynold's number for baseline simulation
- To increase the calculated Reynolds number to a factor of 20%, 40%, & 100%.
- To perform the simulation for all values of Reynold's number and to create an animation file for velocity-pressure.
PROCEDURE:
CALCULATION AND PARAMETEERS
REYNOLDS NUMBER(Re)
Re = ρVD/μ
Where
Vm - average velocity at the inlet of a diffuser,
D - Diameter of the inlet,
ρ - Density of the test fluid
μ - Viscosity of the test fluid.
Diameter of the cylinder = 0.04m
Length of the cylinder = 0.2m
BASELINE SIMULATION PARAMETERS:
Initial assumption VELOCITY=5m/s
SIMULATION END TIME:
We know that, Velocity = Distance / time, on rearranging we get end time for the baseline simulation as:
Since the length of the domain along the X axis is 0.4 m. Then,
Time = Distance / velocity
= 0.4/5
= 0.08 s
since the end time should be 2 times the flow through time. Then Simulation End Time = 0.16 s
|
INPUT PARAMETERS |
VALUES |
|
Analysis Type |
External Flow |
|
Fluid |
Air |
|
Initial Velocity |
5 m/s |
|
Density |
1.125 kg/m^3 |
|
Diameter |
0.04 m |
|
Dynamic Viscosity |
18.14*10^-6 Ns/m^2 |
|
Time Dependent |
Total Analysis Time: 0.16 s Output time step: 0.016 s |
From the formula Reynolds number is calculated as
Re = 13,506.06
Similarly,
Reynold's number at 20%, 40 %and 100 % is been calculated below,
Reynolds number by a factor of 20%:
To perform the flow simulation over the cylinder, let us take Reynolds number factor as 20%:
{100+20=120% ~ 1.2}
Re = 13506.06* 1.2
Re = 16,207.27
Reynolds number by a factor of 40%:
To perform the flow simulation over the cylinder, let us take Reynolds number factor as 40%:
{100+40=140% ~ 1.4}
Re = 13506.06* 1.4
Re = 18,908.48
Reynolds number by a factor of 100%:
To perform the flow simulation over the cylinder, let us take Reynolds number factor as 100%:
Re = 13506.06* 2
Re = 27,012.12
|
|
Velocity |
Reynolds Number |
Simulation End Time (2 times the flow through time) |
|
Baseline |
5 m/s |
13,506.06 |
0.16 |
|
At 20% |
6 m/s |
16,207.27 |
0.133 |
|
At 40% |
7 m/s |
18,908.48 |
0.114 |
|
At 100% |
10 m/s |
27,012.12 |
0.08 |
From the above study, the Velocity increases with decrease in time.
RESULTS:
BASELINE SIMULATION
VELOCITY PLOT
PRESSURE PLOT
20% INCREASE IN REYNOLDS NUMBER
VELOCITY PLOT
PRESSURE PLOT
40% INCREASE IN REYNOLDS NUMBER
VELOCITY PLOT
PRESSURE PLOT
100% INCREASE IN REYNOLDS NUMBER
VELOCITY PLOT
PRESSURE PLOT
CONCLUSION
- As Reynold's number increases the Velocity increases and the flow through time decreases.
- As velocity increases the flow is more stready
- Pressure acts mainly in front area hence there is no significant change