[_Ennui]

Hello all,

I have been attempting to calculate Cd for a cylinder in sea water using a 2D case.

Diameter = 5m
Nu = 1.35e-6
U = 1 m/s
Re = 3.7e+6
Rho = 1026.9 (Although this is never requested or used, seemingly...)

I'm using SimpleFoam solver with Realisable k-e as the turbulence model.

In the documentation I am using for comparison/validation, the value of Cd listed for a smooth cylinder is 0.65 in steady-state flow situation.

The value I calculated for Cd were 0.159 and 0.113 for time steps of 1e-2 and 1e-3, respectively. Both of which are far lower than they should be.


My questions:

1. My mesh is limited to 100k nodes, is this too coarse to generate an accurate result? (see attached)

2. Why is the result seemingly independent of the fluid density? (it is never required as an input)

3. Why is there lift measured for the smaller of the two time steps?

My requests:

1. General advice on calculation of drag coefficients for high Re

2. Any helpful advice would be greatly appreciated


Attached are pictures of my mesh, and residuals & results for each run.

mesh.PNG fcoeffs_biggerDELt_1e02.PNGfcoeffs_littlerDELt_1e03.PNG resids_biggerDELt_1e02.PNG
resids_littlerDELt_1e03.PNG

I hope someone can help - I feel like this is a simple problem but I am really struggling with it.

Thank you very much!