Flow over a cylinder

Objectives:-

To Simulate the flow over a cylinder for different Reynolds number.

Inputs :-

• Diameter of cylinder = 15mm
• Length of cylinder = 50mm
• Length of the Domain = 270mm
• Fluid flow over the cylinder is Air

Reynolds Number (Re):-

The Reynolds number is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar flow, while at high Reynolds numbers turbulence results from differences in the fluid\'s speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow.

• Density = 1.2 kg/m^3
• Dynamic viscosity = 1.81*10^-5 kg/m.s

Assumption:-

• Surface Roughness is not considered.
• Temperature is at Initial or Room Temerature.
• Gravity is not considered.
• Pressure is atmospheric Pressure.

Calculation :-

1. For Reynolds number 20

Velocity = 0.0201 m/s

End Time = 27 sec

2. For Reynolds number 40

Velocity = 0.0402 m/s

End Time = 13.5 sec

3. For Reynolds number 100

Velocity = 0.101 m/s

End Time = 5.5 sec

Calculation of End time:-

velocity = 0.0201 m/s

Computational Domain length in X direction is 0.270 m

Flow through time i equal to the domain length to the velocity.

so, Flow throuh time is comes out o 13.432~13.5 sec

End time is 2 times the flow through time.

So, End time is 27 sec

Observation:-

For Reynolds number 20:-

Animation For velocity distribution over the cylinder within total Analysis time:-

Click here for Animation

Animation For Reative pressure distribution over the cylinder within total Analysis time:-

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Fig:- Velocity cut plot profile with Different Level of Initial Mesh (2, 3, 4, 5)

Fig:- Relative Pressure cut plot profile with Different Level of Initial Mesh (2, 3, 4, 5)

For Reynolds number 40:-

Animation For velocity distribution over the cylinder within total Analysis time:-

Click here for Animation

Animation For Reative pressure distribution over the cylinder within total Analysis time:-

Click here for Animation

Fig:- Velocity cut plot profile with Different Level of Initial Mesh (2, 3, 4, 5)

Fig:- Relative Pressure cut plot profile with Different Level of Initial Mesh (2, 3, 4, 5)

For Reynolds number 100:-

Animation For velocity distribution over the cylinder within total Analysis time:-

Click here for Animation

Animation For Reative pressure distribution over the cylinder within total Analysis time:-

Click here for Animation

Fig:- Velocity cut plot profile with Different Level of Initial Mesh (2, 3, 4, 5)

Fig:- Relative Pressure cut plot profile with Different Level of Initial Mesh (2, 3, 4, 5)

Conclusion:-

• After observing all the Calculation, we can observe that when the Reynolds number increases the velocity of air over the cylinder increases. But the flow through time is decreases.
• After observing all the plot, we can observe that when the level of initial mesh size increases the plot shows narrower and clear velocity and Relative pressure profile.
• If the velocity increases then the area of high velocity (dark red area) decreases but the area of velocity behind the front surface(area which is direct contact with air) is increase(show by blue region, velocity approximately equal to zero).
• When the reynolds number is small then the blue Region(zero velocity region) in the velocity profile is observe like a flame but by increasing the reynolds number the profile will be changed and show that the flame cut from the front in an arc.
• In the Relative pressure profile, it shows that the pressure creation is maximum at the front face of the cylinder which is shown by red region and minimum at the top and bottom of the cylinder which is shown by blue region in the relative pressure cut plot figure.

References:-

• www.wikipedia.com
• projects.skill-lync.com
• www.google.com
• www.youtube.com