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Effect of the type of mesh on a Pipe flow problem

Tania Alam

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Before you dive into the problem, let's have an easy poll.  

3 members have voted

  1. 1. Which one will capture the physics of the flow better - the coarse mesh or the fine mesh? Please select an option and let others know what you think?

    • coarse mesh
      0
    • fine mesh
    • depends on the given problem

58c0e1facf9a1_EffectofthetypeofmeshonaPipeflowproblem.thumb.jpg.1fdd8a463decca9320342da21a339a2f.jpg
 
 
The project explains how the type of mesh can influence the results obtained for the mixing of flow in a pipe. The simulation is done on a cloud-based CAE platform called SimScale. The link to the project is here. This project is a part of the SimScale Professional Training on CFD (Computational Fluid Dynamics).
 
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The pipe flow geometry, originally uploaded by the SimScale Staff, available in the public projects.
 
For this internal flow problem, a Hex-dominant parametric mesh is used. Two types of meshes are created for the problem - a coarse mesh ( which accommodates all the features of the geometry) and a fine mesh ( by increasing the fineness).
 
d54ec048061159.588d8513e5e65.jpg
Coarse mesh ( Fineness: 1-Very coarse)
 
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Fine mesh ( Fineness : 4-Fine)
 
The same type of analysis is performed for both the meshes (Fluid dynamics: Incompressible). Same boundary conditions and simulation controls are defined for both the meshes.
 
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Simulation run: Coarse mesh
 
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Simulation run: Fine mesh
 
The simulation results are post-processed (clip filter is used) to get the contour plot of the velocity flow field.
 
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Post-processor screenshot for coarse mesh
 
d8894448061159.588d8513e8008.jpg
Post-processor screenshot for fine mesh
 
As revealed by the results the fines mesh captures specific physics (like flow separation and vorticities) more accurately. Isn't that expected? Well, not always!
 
 
 
This blog was previously posted on Behance.

 

 

 

 

 

 

 



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Yes, that is expected. In most cases, a finer mesh will more accurately capture the physics at the expense of more computer cost (resources, run time). There may be cases where this is not true, but they are not the norm.

DrD

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I might add that this is an example of using a specific case to attempt to address a general problem. The results of the specific case can never be taken to PROVE the nature of the general problem. It may suggest what the answer is, but proof is not possible in this approach. It would take an infinite number of specific examples to even approach a proof, and that is clearly out of the question.

As Tania says, it appears that in this example, the finer mesh captures more details. But can we be sure that is true? It agrees with what we expect, and it seems reasonable. But until we truly know what is happening (by direct observation without disturbing the flow in any way), we cannot really be certain.

DrD

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