Hi all,
I am going to use either Ansys CFX or Ansys Fluent solver to simulate flow past a semi-submerged rectangular cylinder, as shown in Fig. 1. The main goal here is to achieve an accurate prediction of pressure distribution over the cylinder, which seems to be particularly reliant on the capability of the CFD model to predict the separation and the reattachment of the flow correctly. I would appreciate any tips regarding the following questions.
Q1. How important is the choice of the turbulence model? Which models are superior? Could the flow be modelled as being laminar at all?
Q2. How important is the approach to the free surface? Could the free surface be modelled as a free-slip wall to reduce computational costs? Is it necessary to precisely track the free surface using the VOF model for this study?
Q3. What are the most appropriate boundary conditions for the simulation?
Q4. Which is more suitable for this problem? CFX or Fluent?
1) Use the k-omega turbulence model to predict flows involving adverse pressure gradients.
2) You can use no-slip. Using a wall as a no-slip won't have much effect on computational time.
3) You can make a rectangular domain of height h. And in the upstream face of the rectangle, you can give a flow velocity inlet of U.
4) Ansys FLUENT
CFD software and Finite Element Method software shall be used for
the flow path simulation over a cylinder.
Finite Element software such as Ansys Fluent, CATIA shall be used for
flow field simulation and for calculating the pressure,velocity, stress distribution of a flat plate or a circular body.
I'm no expert on Fluent etc, but if the velocity is low and the flow is laminar these turbulence-intensity based models will not be appropriate and a "creeping-flow" based mode would seem better. High water velocities under a raft seem unlikely to me!
If the size t is less than 8-12 distances to the bottom surface, the drag force will be determined, among other things, by the added masses of the liquid reflected from the bottom surface. If this is not important, then in the model you need to specify a distance of more than 12.
The number of wall layers is enough 5.
From above on a free surface, the wind has a speed and direction?
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