# [ANSYS Meshing] Concept of conformal and non-conformal interface

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 LinkBack Thread Tools Display Modes
 August 11, 2012, 11:42 Concept of conformal and non-conformal interface #1 Senior Member     Meimei Wang Join Date: Jul 2012 Posts: 494 Rep Power: 7 Hi Could you tell me what's the concept of conformal and non-conformal interface? I tried to search for it online, but I didn't find any good answer. Thanks! __________________ Best regards, Meimei

 August 11, 2012, 14:15 #2 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,258 Blog Entries: 6 Rep Power: 43 Both are interfaces and there is averaging of data on both sides before transferring to other side. Conformal interface : An interface with equal no of nodes on both sides. Non Conformal interface : An interface which does not have equal no of nodes on both sides

 August 13, 2012, 02:49 #3 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,230 Rep Power: 22 Just a minor correction here: A conformal interface is not defined by an equal number of nodes on both sides. Instead, the meshes on both sides of the interface have to be conformal, which means that every node on one side of the interface can be matched with a node on the other side of the interface with a very low tolerance. The advantage is that there is no (additional) interpolation necessary at a conformal interface. This makes the computation faster and more accurate. Consequently, a non-conformal interface can be set at two faces with the same number of nodes. Last edited by flotus1; August 13, 2012 at 05:55.

 May 7, 2015, 10:17 non conformal interface #4 New Member   sagar Join Date: Jan 2014 Location: pune,india Posts: 5 Rep Power: 4 Since data across non conformal interface is averaged and transferred is there significant loss in accuracy due to interpolation error?If error is large then which approach is better 1.domain divided in structured meshes joined with non conformal interface.or, 2.unstructured mesh in whole domain without need of interface I am using multiblock method for horizontal axis wind turbine mesh which is separated in 3 multiblocks and merged Aohnia likes this.

May 7, 2015, 11:52
#5
Senior Member

Daniele
Join Date: Oct 2010
Location: Italy
Posts: 992
Rep Power: 16
Quote:
 Originally Posted by flotus1 Just a minor correction here: A conformal interface is not defined by an equal number of nodes on both sides. Instead, the meshes on both sides of the interface have to be conformal, which means that every node on one side of the interface can be matched with a node on the other side of the interface with a very low tolerance. The advantage is that there is no (additional) interpolation necessary at a conformal interface. This makes the computation faster and more accurate. Consequently, a non-conformal interface can be set at two faces with the same number of nodes.
So, by your definition, if I have an interface which splits a moving from a static zone, even if I have the two adjacent surfaces with the same number of nodes and at the same distance, this is a non-conformal interface, as when sliding the nodes will not overlap.
So, a conformal interface can be obtained only for an interface which connects 2 static zones?

Thanks
__________________
Google is your friend and the same for the search button!

 March 11, 2016, 10:04 #6 New Member   Join Date: Nov 2015 Posts: 4 Rep Power: 2 Sagarmore's question is very interesting, it's a pity that no one seemed to answer it. Did you manage to get an answer ?

 March 12, 2016, 01:36 unstructured vs. non conformal mesh approach #7 New Member   sagar Join Date: Jan 2014 Location: pune,india Posts: 5 Rep Power: 4 No I couldn't get answer.I prefer non conformal mesh approach though. Aohnia likes this.

 March 12, 2016, 18:39 #8 Senior Member     Alex Pasic Join Date: Aug 2011 Location: Croatia Posts: 184 Rep Power: 7 I'll take a stab at this... Since hexa meshes are usually of far superior quality compared to tetra meshes (at least in cases where flow direction is aligned with direction of elements), I've always opted for an option to use hexa (conformal structured or non-conformal with interfaces) instead of tetra. My typical usage was to create a structured hexa wind tunnel and then create hexacore meshes for volumes containing vehicles (race cars). Now, as far as non-conformal interfaces go ANSYS said the following: interfaces work without any problems, in fact they're used in such complex cases involving heat transfer and enthalpy and other crap with turbomachinery examples (where interfaces are common place) that I've never worried about "lack of accuracy". However, user's guide and other documentation says that large jumps in element sizing on the interfaces can lead to more time needed for the interpolation and some errors.. so, to deal with this I've usually tried to match element sizes on both sides of the interface. Even though I could usually match this so that it looks as if it could be a completely conformal mesh from a far, I couldn't actually merge the meshes (fuse) because the number of nodes didn't really exactly match (hexacore had that 1 layer of tetras to transition from a floor prism layer to the hexa volume - which screwed up the node count on those faces). All in all, any loss in accuracy over the interface was never a concern for me, especially when you take into consideration the huge leaps in accuracy obtained by using a hexa mesh for the whole wind tunnel. The wake effects were really well captured even meters behind the vehicle while tetra meshes looked all smudged and diffused even very close to the car (and let's not even talk about levels of refinement needed to get a good wake resolution with a tetra mesh). My \$0.02 = hex meshes + interfaces for the win. sagarmore and Aohnia like this. __________________ If you're in need of some free quality CFD video tutorials - check out SiriusCFD @ YouTube

 April 27, 2016, 05:52 #9 Member   Fabio Malizia Join Date: May 2010 Location: Leuven (Belgium) Posts: 35 Rep Power: 8 Hi, I am also dealing with interfaces for the first time. My case is a wheel study. I have created my wheel and outside it a cylindrical interface to allow the definition of a moving reference frame. I was using now tet mesh, but do you think is better to use hexacore + hex outside it? Thanks a lot, Fabio

 April 28, 2016, 04:59 #10 Senior Member     Alex Pasic Join Date: Aug 2011 Location: Croatia Posts: 184 Rep Power: 7 If you could post a picture/screenshot things might be clearer. Anyway.. if your wheel is sitting on the ground and you want it to "rotate" and are conducting an unsteady simulation then it'd be enough to just separate the volume inside the rim (including the spider) so it can rotate freely - the rest of the wheel (tire & rim part) which don't really affect the rotation can just be given rotating wall boundary conditions without using the MRF & moving mesh. As far as hex/hexacore goes.. yes. This case is no different, maybe just keep the inside volume of the rim & spider pure prism + tetra since flow in there is not really going to be aligned with the hex element direction, but the rest of the domain can be hexacore for sure. Same principle applies if you want the whole tunnel to be pure hexa (to avoid floor prisms & triangles), you just add more interfaces for the two rectangular domains (wheel domain and tunnel domain). Fabio88 likes this. __________________ If you're in need of some free quality CFD video tutorials - check out SiriusCFD @ YouTube

April 29, 2016, 04:03
#11
Member

Fabio Malizia
Join Date: May 2010
Location: Leuven (Belgium)
Posts: 35
Rep Power: 8
Hi Scipy,

thanks for replying.
I am actually evaluating two wheels, one disc wheel and one with spokes.

My first idea, as you can see in the picture, was to create a displacement between the wheel+interface and the floor, and using the MRF on the interface.
Later I will create another cylindrical interface to allow investigation of different yaw angles.

My first mesh attempt, was using tetra+prism. Now I started to watch some tutorial about hexcore to understand how to use them.

Your method, splitting the inner volume from rim/wheel, sounds also very interesting. I just need to figure out how to split in two parts the wheel: I do not know if it is better to do at CAD level (PTC Creo) or when I import it in design modeler. Do you have any suggestion?

Thanks a lot for the help.

Fabio
Attached Images
 WheelZippSub9_interface_geom_2.jpg (43.9 KB, 10 views)

 April 29, 2016, 06:39 #12 Senior Member     Alex Pasic Join Date: Aug 2011 Location: Croatia Posts: 184 Rep Power: 7 Yeah.. you don't need all of this for a pure disk wheel. You just need a wall boundary condition of "rotating wall" and can run this in a simple steady state case. Also, the wheel needs to be touching/intersecting the ground Once you go for a spoked wheel, you just need to separate the inner volume and have that rotate, the rest stays the same. __________________ If you're in need of some free quality CFD video tutorials - check out SiriusCFD @ YouTube

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

All times are GMT -4. The time now is 17:32.

 Contact Us - CFD Online - Top