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  • FLUENT - Unsteady Flow Past a Cylinder - Step 7

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Using method taught in Step 6, calculate the Strouhal Number for time steps size of 0.2 and 0.1. Following table summarized the result.

Time Step Size (s)

0.1

0.2

0.4

Strouhal Number

0.1878

0.182

0.172

Difference (%)

3

6

0

As can be seen, the Strouhal number difference get smaller as we move to a smaller time steps. We can conclude that time steps size of 0.1s will give us a fairly accurate representation of physical flow in term of time parameter.

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Do note that with time step size of 0.1s, we have exceeded the experimental Strouhal value of 0.183. However, we have only investigated the time parameter. We will have to investigate other parameters such as grid convergence, residual convergence, unsteady formulation, etc, before we can conclude on the accuracy of our model.

Reference

Anchor
ref1
ref1
C.H.K Williamson and G.L. Brown, A Series in to representat the Strouhal-Reynolds number relationship of the cylinder wake, J. Fluids Struc. 12,1073 (1998).

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