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BC's for external flow (flow past a cylinder) |
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March 5, 2018, 11:40 |
BC's for external flow (flow past a cylinder)
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#1 |
New Member
Arthur Piquet
Join Date: Mar 2013
Posts: 18
Rep Power: 13 |
Hello everyone,
I am currently testing some BC's with Fluent 17. I'm using a simple test case for now (2D). My current case is a cylinder D=0.1 in 2D with an outflow at U=1 (fluid is water). Here's a picture of it: https://imgur.com/RoFIcfr I'm having trouble to find the correct BC to apply for this simple external flow. At the inlet (left BC), I use Velocity-inlet with ux=1. At the outlet (right BC), I use pressure-outlet. My problem is for the top and bottom BC. I tested 2 method but it doesn't give me the same result. 1. Top and Bottom BC are velocity inlet at ux=1. 2. Top and Bottom BC are slip wall (I use a moving wall at ux=1). If I look at the velocity field, it seems to be the same. But my pressure field is different: 1. https://imgur.com/bvr9Rqq 2. https://imgur.com/B71fqJX If I look at the drag coefficient Cd1=47 Cd2=50 Which method is the right one? pressure inlet perhaps? Thank you |
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March 6, 2018, 06:00 |
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#2 |
New Member
Join Date: Feb 2016
Posts: 2
Rep Power: 0 |
My approach would be a standard "no-slip" Wall BC for top and bottom. Just make sure the boundarys are far enough from your cylinder.
Moving wall (ux=1) should also work and give the same results for your cylinder flow. The BC shouldn't have an influence on the flow around the cylinder. Velocity-In wouldn't be correct because there is no mass entering the domain here. How did you specify the drag? Did you plot the variable over iterations? Correct me if I'm wrong! Edit: Your drag seems a bit high. Your Re-number should be: 0,1m*1m/s*1000kg/m^3/0,001Pa*s=100000. Drag should be ~1 Last edited by ICEMgod; March 6, 2018 at 08:05. |
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