Hi everybody,
Can anybody suggest me the best type of tria mesh( right angled tria or equilateral triangle) to be used when meshing the part in HM? Does the tria type impact the results? if so how does it affect?
thanks
kamesh
Solved! Go to Solution.
Solved by madhukeshwart. Go to Solution.
Hi Kamesh,
Ideally, triangles should be equilateral.
Shoudong Xu
Moldflow Meshing Team
thank you for the reply, i wouldlike to know the reason and how does it affect the accuracy of the results.
thanks,
kamesh
Kamesh,
It is theoretically proven Equilateral Trai is better than Right angle triangle
refer following discussions
Hello Kamesh,
If you are meshing your part in HM for Moldflow analysis always use Equilateral triangle mesh which will give you better results than Right angle trias. Correction & geometrical capturing would be quite difficult but u will get better end results.
We tried this for our understsnding & observed the difference in results.
Thank you
Regards
Sabarinathan. S
Moldflow Analyst
L&T Technology Services
Chennai, India.
Hi everybody,
thanks for all the replies, i would like to know if the same tria and equi tria mesh when converted to a 3D tet mesh, produce different results? which gives closer result to reality? has any body tried? i observed 5-10% difference in the results.
Hello Kamesh,
Yes we have tried with equi tria mesh in DD & convert the same to 3D, the results are quite closer to the reality.
There was a slight difference in some results due to poor capturing of some critical regions with equi tria.
In that case what my advice is to use R-trias in the critical regions & perform the analysis you will get much closer results to the reality.
In some critical cases we need to club both R-tria & equi tria meshes if your performing an 3D analysis for the better result capturing.
please find the attached image for your reference.
Hope this will helps your query.
Regards
Sabarinathan. S
It has been discussed many times over user forums. summarising the same here.
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A possible reason is due to the method which Mold flow uses to fill the product.
you can see that it starts from one point and fills to adjacent points.
When equilateral triangles are used the distance between the adjacent points and the starting point are more favorable and in the case of an aspect ratio of 1:1 it's the same distance.
When right angled triangular elements are used you always have a side which is longer than the other 2 which may be less favorable.
In right angled triangles, With the longest side in the direction of flow, the end node of high aspect ratio elements will add an excessive resistance factor to flow front calculations.
The aspect ratio of mesh elements can affect analysis performance. High aspect ratios can cause a slower analysis, and affect results.
we need to avoid very high aspect ratio triangles, which have their longest side in the direction of flow. If very high aspect ratios cannot be avoided, the longest side should, if possible, be at right angles to the flow direction.
Warpage is a structural mechanics problem, while the primary calculation methodology that MOLDFLOW follows is a fluids flow-volume control domain problem. Similar mesh discretization differences occur when comparing CFD vs. Structural FEA grid modeling. Being that MOLDFLOW is a volume controlled domain problem, equilateral elements have a similar distance (ie., volume potential) to fill in each node-to-node direction [in above picture from NODE 1 to all other adjacent nodes]. This means there is the same potential for the flow to move in any direction and so take less solver iterations to reach equilibrium (i.e. converging on the correct fill condition prediction).
With this in mind, then Right-angled triangles in the flow or cross-flow direction that have an ASPECT Ratio >1.0 to very high, thus differing distances (i.e., control volume increments) make it computationally more difficult to predict the correct flow direction and filling condition.
A mesh of Right angled triangles will cause some error in each element as the distance between nodes is not the same. This error is generally not a problem. However, if there are large aspect ratio, right angled triangles, the error may be significant.
Right angle triangle mesh will take more time to solve fill analysis & warpage may be results will be different.
So It is recommended aspect ratio < 6, use Equilateral triangles as much as possible, preferably in Base wall.
Some percentage of right angled triangles are is ok in B-side feature like rib, boss, which contributes much for results.