Flow over a cylinder

Aim :- Transient flow Simulation over a cylinder .

Summary :- 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 flow simulation.

• Calculate the baseline case Reynolds number.
  • Re = ρ*velocity*D/μ Here, D = cylinder diameter, μ = dynamic viscosity, ρ = density

    Diameter	0.04 m
    Initial velocity	10 m/s
    Density	1.225 kg/m3
    Dynamiv Viscosity	18.14⋅ x10−6 Nsm−2

    by Substituting the above values we get, the baseline case Reynolds number, Re = 27012.127
  • Similarly, Reynold's number at 20%, 40% and 100 % is calculated,
    At 20% Re = 32414.55
    At 40% Re = 37816.97
    At 100% Re = 54024.25

### length of Domain = 0.75 m

flow through time=0.75/10= 0.75 sec

end time = 0.75x2 = 1.5 sec

similarly

At 20% End time = 0.125 sec
At 40% End time = 0.107 sec
At 100% End time = 0.075 sec

#####Geometry Of Model :-

Procedure :-

• Cylinder of above mentioned dimensions is created.
• Set the external ow analysis in the wizard.
• Calculated end time is taken as total analysis time.
• Fluid as air is taken into consideration.
• Velocity in the X-direction is taken as calculated U-inlet.
• Set the Computational domain in X-direction as 0.75m.
• Run the Project and Finally get the Cutplots of pressure and Velocity

Result :-

• For Base Line Study:- velocity =10 m/s Re=27012.127 End time = 1.5 sec
  

Velocity Contour:-

##########After Fine Refinement of Mesh, velocity contour

Pressure Contour:-

##########After Fine Refinement of Mesh, pressure contour

• When velocity =12 m/s , Re= 32414.55, End time = 0.125 sec
  

########## Velocity Contour ########

########## Pressure Contour ########

• When velocity =14 m/s , Re= 37816.97, End time = 0.107 sec
  

########## Velocity Contour ########

########## Pressure Contour ########

• When velocity =20 m/s , Re= 54024.25, End time = 0.075 sec
  

########## Velocity Contour ########

########## Pressure Contour ########

Obseravation and Conclusion :-

• From the above observation we note that with increase of reynolds number velocity also increases and the velocity , pressure are higher near the walls of the cylinder and becomes lesser away from the walls . With increase of velocity , the pressure near cylinder walls increases.