Flow over cylinder

Aim:

• CFD analysis of a cylinder in which external flow takes place and running a baseline simulation and then calculating the Reynolds number and also the simulation end time.
• Reynold’s number increased by a factor of 20%, 40% and 100% and then run the transient flow simulation.
• Create pressure and velocity animation for four different Reynold’s number

Theory:

1. Reynold’s number:

The Reynolds number (Re) is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations.

The present study aims to analyse the fluid flow 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 file for velocity-pressure.

2. Geometry of the model:

The model of a solid cylinder was created in SOLIDWORKS 2017, The dimensions are as follows:

Diameter of the cylinder: 0.06m

Length of the cylinder: 0.01m

Procedure:

• First, the wizard option is selected inflow simulation feature of SOLIDWORKS 2017 and necessary conditions were set.
• The necessary conditions were: Setting the flow simulation to external, Taking the simulation fluid as air, Taking the animation time of 1 sec with a step count of 0.1 sec, Taking the velocity along x-axis as 10 m/s.
• Calculating Reynolds number using formula given above with density of air=1.225 kg/m^3, velocity = 10m/s, diameter of the cylinder = 0.06m, dynamic viscosity = 18.14 * 10^-6 Ns/m^2 which came out to be 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
• The global mesh label was set to 3.
• Then a parameterised study was set up with inlet velocity corresponding to these Reynold’s number i.e. 12m/s, 14m/s, 20m/s and the simulation was started.
• Then the respective pressure-velocity animation were created at different given velocities.

Calculation of simulation end time:

Velocity = Distance / time

Time = Distance / velocity i.e. Time = 1.8/10 = 0.18 sec

The length of the domain along the X-axis is 1.8 m

When the Velocity is 10 m/s for Re = 40518.19 then Simulation end time = 0.18 sec

Given that the end time should be 2 times the flow-through time

At Baseline for V = 10 m/s, Re = 40518.19, Simulation end time = 0.18 sec

At 20% For V = 12 m/s, Re = 48621.83, Simulation end time = 0.144sec

At 40% For V = 14 m/s, Re = 56725.46, Simulation end time = 0.108 sec

At 100% For V = 20 m/s, Re = 81036.38, Simulation end time = 0.09 sec

From this, we can see that the Velocity increases the time decreases.

Outputs:

Flow over a cylinder at Baseline Velocity 10m/s:

Cut Plot of Velocity contour:

Animation videos for velocity @10 m/s and Re = 40518.19:

https://drive.google.com/file/d/1H2SUI8KBJCi_9kMORAmYWXO8lnCG2jYX/view?usp=sharing

Cut Plot for Pressure:

Animation videos for Pressure @10 m/s:

https://drive.google.com/file/d/1EA6XucR_lX-PKSenN3x25wAITxvjh_TN/view?usp=sharing

Flow over a cylinder at Baseline Velocity 12m/s:

Cut Plot of Velocity contour:

Animation videos for velocity @12 m/s and Re = 48621.83:

https://drive.google.com/file/d/15cDuDc-oMqRoGZhbE2FAyUfcSXhDVUN-/view?usp=sharing

Cut Plot for Pressure:

Animation videos for Pressure @12 m/s:

https://drive.google.com/file/d/1KD17xKRP2mWEdhiQQzbHou68jPjLXk73/view?usp=sharing

Flow over a cylinder at Baseline Velocity 14m/s:

Cut Plot of Velocity contour:

Animation videos for velocity @14 m/s and Re = 56725.46:

https://drive.google.com/file/d/1ozD5weI9kRYH5TE1sQym2A6a36LL8tJI/view?usp=sharing

Cut Plot for Pressure:

Animation videos for Pressure @14 m/s:

https://drive.google.com/file/d/1UeteQQKlPEnBJX0ZSnhic83BcrbHmhsM/view?usp=sharing

Flow over a cylinder at Baseline Velocity 20m/s:

Cut Plot of Velocity contour:

Animation videos for velocity @20 m/s and Re = 81036.38:

https://drive.google.com/file/d/1REPDBpRgLTvuquDhzf88sVI9gmf35PEg/view?usp=sharing

Cut Plot for Pressure:

Animation videos for Pressure @20 m/s:

https://drive.google.com/file/d/15MXKNSbZ_e3CvGbd-cLfwUB9SSjSBx8k/view?usp=sharing