Project

Flow over a cylinder for steady and transient flow

Objective :

For Re = 100, simulate the flow over a cylinder using steady and transient mode.

Considerations:

For Re to be \'100\', Following values are considered.
density=1 kg/m3, velocity=1 m/s, Dia of cylinder=2m, viscosity=0.02 kg-s/m
Strouhal Number is given by,
St=fL/v
where, f-frequency of vortex shedding, L-Charateristic Length, v-flow velocity

Experimental Setup:

Mesh Type = Triangular, Mesh Size = 0.25m, Total no. of mesh = 40502

a) For Steady State

From the velocity contour plots, we can say that vortex shedding is clearly observed at Re=100.
By residuals and vertex average plot, we can say that flow is converged and no. of iterations taken for convergence is 450 iterations.
Strouhal number cannot be calculated from the plots as we dont have relation between flow time and vortex shedding frequency.

b) For Transient State

From the velocity contour plots, we can say that vortex shedding is clearly observed at Re=100.
From residual plot, it is observed that residuals doesnot reach to steady state and keeps on varying.
From vertex average plot, it is observed that flow has converged and time taken to reach convergence is around 110s.
Strouhal Number can be calculated in transient flow and value is,
f = 12/60 = 0.2
St = fD/v = 0.2*2/1 = 0.4

Conclusion:

Von Karman effect, i.e; vortex shedding is observed on both the approaches (steady and transient state flow) for the Reynold\'s number, Re=100.

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