Flow over cylinder
Aim:
To made time dependent flow simulation on flow over cylinder by varying the inlet velocities by increasing the reynolds number.
Objectives:
- To model a cylinder in solid works.
- To made a baseline time dependent simulation and find the reynolds number value.
- To made different simulations by increasing the reynolds number value by 20%,40% and 100%.
- To calculate the flow through time and end time of all the three cases.
- To analyse the velocity and pressure plot of all the three cases.
Cylinder modelling:
The cylinder is modelled with the diameter of 0.05m and with the length of 0.1m.
Baseline simulation:
The baseline simulation is made with the velocity of 10m/s through x-direction. By using the formula, the reynolds number value for 10m/s was found.
Re = rho*U_inlet*D/mu
where, D = cylinder diameter
mu = dynamic viscosity
rho = density.
The time is set for 0.01s and the output time is stepped by 10 and the output time value is 0.1s. The pressure and velocity over the cylinder was analysed.
The average mesh is made for the simulation.
The cutplot was made to visulaize the velocity and the pressure results over the cylinder.
Velocity plot:
Pressure plot:
Calculations:
1) Reynolds number calculation:
Re = rho*U_inlet*D/mu
rho = 1.225kg/m^3 (air).
U_inlet = 10m/s.
D = 0.05m.
mu = 1.81*10^-5kg/ms.
Re = (1.225*10*0.05)/1.81*10^-5
Re = 33839.779.
2) Re calculation for various cases:
Case 1 - Re is increased by 20%
Re = 33839.779+(33839.779*0.2)
Re = 40607.7348
Case 2 - Re is increased by 40%
Re = 33839.779+(33839.779*0.4)
Re = 47375.6906
Case 3 - Re is increased by 100%
Re = 33839.779*2
Re = 67679.558
3) Inlet velocity calculation for different Re values:
Case 1 - Re is increased by 20%
Re = 40607.7348
V = 12m/s.
Case 2 - Re is increased by 40%
Re = 47375.6906
V = 14m/s.
Case 3 - Re is increased by 100%
Re = 67679.558
V = 20m/s.
Case 1:
The flow simulation is made with the inlet velocity of 12m/s. The velocity and the pressure plots are analysed.
Simulation end time calculation:
Flow through time = length of domain/velocity
length = 1m
Flow through time = 1/12
= 0.0833s
end time = flow through time * 2
= 0.1667s.
Velocity plot:
Pressure plot:
Case 2:
The flow simulation is made with the inlet velocity of 14m/s. The velocity and the pressure plots are analysed.
Simulation end time calculation:
Flow through time = length of domain/velocity
length = 1m
Flow through time = 1/14
= 0.0714s
end time = flow through time * 2
= 0.1429s.
Velocity plot:
Pressure plot:
Case 3:
The flow simulation is made with the inlet velocity of 20m/s. The velocity and the pressure plots are analysed.
Simulation end time calculation:
Flow through time = length of domain/velocity
length = 1m
Flow through time = 1/20
= 0.05s
end time = flow through time * 2
= 0.1s.
Velocity plot:
Pressure plot:
Results and discussions:
The various observations can be made from the analysis of the flow over cylinder in different cases.
- The velocity and the pressue plot doesnot differ much in all the three cases.
- The maximum velocity and pressure value increased with increasing the velocity of the fluid.
- The velocity value is maximum at the two end of the cylinder.
- The pressure value is maximum at the fluid hitting side of the cylinder.
- Based on the results obtained the changes in velocity and pressure due to the flow of fluid is obtained.
Conclusion:
Thus, the flow simulation is made with varying the reynolds number. The velocity and pressure characteristics plots of all the cases were analysed.