Flow over a cylinder
Flow over a cylinder in solid works
ABSTRACT:
In this Project, CFD analysis of a cylinder in which external ow takes place and running a baseline simulation and then calculating the Reynolds number and also the simulation end time. Then increase the Reynolds number by a factor of 20%, 40%, and 100% then run the transient ow simulation. Animations for pressure-velocity for all the three Reynolds number created.
1. INTRODUCTION:
Computational Fluid Dynamics
CFD has fascinated researchers, as it is a fast, accurate and reliable method of analyzing the variation of hydrodynamic properties of the ow over and within a body. Computational Fluid Dynamics (CFD) is a branch of uid mechanics that uses numerical methods and algorithms to solve complex problems involving fluid flow.
Reynold's Number:
Reynolds number can reveal whether the ow is laminar or turbulent. The transition from laminar to turbulent ow depends on the surface roughness, flow velocity, geometry, surface temperature, and type of fluid, among others.
The present study aims to analyze the uid ow over a cylinder and calculate Reynold's number for baseline simulation and increase the calculated Reynolds number to a factor of 20%, 40%, & 100% and perform the simulation for all the three values of Reynold's number and create an animation le for velocity-pressure.
2. GEOMETRY OF THE MODEL:
In this project, a cylinder is created in SOLIDWORKS CAD software. The design parameters are as follows:
Diameter of the cylinder = 0.06 m
Length of the cylinder = 0.1 m
3. BASELINE SIMULATION PARAMETERS:
Initially, I considered the baseline velocity of air to be 10m/s. On the basis of initial velocity, Reynolds number is calculated.
Table 1.1: Parameters
- Re = rho*U_inlet*D/mu
- D = cylinder diameter
- mu = dynamic viscosity
- rho = density
by Substituting the above values we get, the baseline case Reynolds number,
Re = 40518.19
Similarly, Reynold's number at 20, 40 and 100 % is calculated,
At 20% Re = 48621.83
At 40% Re = 56725.46
At 100% Re = 81036.38
Conducting the Baseline simulation
Table 1.2: Baseline simulation condition
4. CALCULATiNG SMULATION END TIME:
Velocity = Distance / time
Time = Distance / velocity
i.e. Time = 0.75/10 = 0.075 sec
The length of the domain along the X axis is 0.750 m
When the Velocity is 10 m/s for Re = 40518.19 then Simulation end time = 0.15 sec
Given that the end time should be 2 times the ow through time
At Baseline For V = 10 m/s , Re = 40518.19 , Simulation end time = 0.150 sec
At 20% For V = 12 m/s , Re = 48621.83 , Simulation end time = 0.125 sec
At 40% For V = 14 m/s , Re = 56725.46 , Simulation end time = 0.107 sec
At 100% For V = 20 m/s , Re = 81036.38 , Simulation end time = 0.075 sec
From this we can see that the Velocity increases the time decreases.
5. RESULTS:
Flow over a cylinder at Baseline Velocity10m/s
Cut Plot of Velocity contour
Animation videos for velocity @10 m/s and Re = 40518.19
Cut Plot for Pressure
Animation videos for Pressure @10 m/s
Now We consider the all three Reynold's number and the ow which calculated from the baseline simulation.
Case 1: Flow over a cylinder at 20% of Reynolds Number i.e. @12m/s
Cut Plot of Velocity contour
Animation videos for velocity @12 m/s and Re = 48621.83
Cut Plot of Pressure contour
Animation videos for Pressure @12 m/s
Case 2: Flow over a cylinder at 40% of Reynolds Number i.e. @14m/s
Cut Plot of Velocity contour
Animation videos for velocity @14 m/s and Re = 56725.46
Cut Plot of Pressure contour
Animation videos for Pressure @14 m/s
Case 3: Flow over a cylinder at 100% of Reynolds Number i.e. @20m/s
Cut Plot of Velocity contour
Animation videos for velocity @20 m/s and Re = 81036.38
Cut Plot of Pressure contour
Animation videos for Pressure @20 m/s
6. CONCLUSION(OBSERVATION):
- As Reynold's number increases the Velocity increases and the ow through time decreases.
- As the velocity or Renold's number increase the ow over the cylinder becomes steady and the velocity plot at 20% and 40% exhibit slight unsteady plot whereas at 100% the ow is steady and we can draw a clear understanding of the ow when velocity is increased.
- There is no signi cant change in the pressure plot and pressure is mainly acting of the frontal area of the cylinder.