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Negative x-force result for a flat plate simulation |
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#1 |
New Member
Constantin
Join Date: Feb 2019
Posts: 2
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Hello smart people out there,
for my Bachelor dissertation among other things, I simulate a flat plate (3D to capture the effect of the edge vortex) at AoAs from -2deg to +14deg with the following dimensions: - chord: 470mm - span: 107mm - thickness: 16mm - an elliptical leading edge - a triangular (tapered) trailing edge During the post processing of my first set of simulations I discovered, that the highest x-force and thus the drag force appears at 0deg AoA and decreases for both positive and negative AoAs. Actually the x-force reaches 0 at about 10deg AoA and even becomes negative for angles above 10deg. Due to the fact that the mesh I used for this set, was not very fine and my setting not that thoughtful, I created several meshes with drastically better quality (about 5 times more nodes, very fine sizings around the plate and an inflation layer to reach a y+ value of 1). In addition to that I've read a lot about the setup and adjusted it accordingly. I even tried to define the plate as rough wall with a fitting Sand Grain Roughness. Unfortunately this steps didn't bring the wished effect - the x-forces only changed very little and remained negative for the corresponding angles. Maybe one of you can help me, to get a solution to this problem or at least explain this effect. |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,816
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Please post an image of what you are modelling and your output file.
Also this FAQ gives general advice: https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F
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Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum. |
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#3 |
New Member
Constantin
Join Date: Feb 2019
Posts: 2
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I got it:
The equation for drag needs to be: Fx*cos(alfa)+Fy*sin(alfa). I forgot the Fy part. |
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Tags |
3d simulation, negative drag force |
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