FAQ for FLUENT Users webinar【转帖】

转帖自ANSYS http://www.ansys.com/special/icem-cfd-qanda/

Hello all and thank you for coming to the Advanced Meshing for FLUENT Users webinar.

We had 200 Fluent users attend the webinar and a number more who registered but couldn’t get in. Some of you already know ANSYS ICEM CFD and others had never seen it. We got a fair number of questions which I will answer here in the order that they were asked.

Many of you asked for a copy of the presentation. We had planned to record the original attempt, but the recording didn’t work properly (no sound). As a result we just recorded it again. I think the repeat was better because I did it with your questions in mind. We will attach a link to the recording in this email.

Here are your questions and answers.

K M: Does ICEM CFD have advantages over GAMBIT?
Yes, but it would be more fair to say they were different tools. You should consider ICEM CFD if you have geometry issues in GAMBIT, or if you want to generate Hexa meshes or Hybrid meshes, or if you want to interactively edit your mesh.
Happy GAMBIT users should just stick with GAMBIT until Workbench is ready to handle all your needs. Try the latest release, GAMBIT 2.4.6, due out July 9th, 2007.
Catherine: When will FLUENT be available within ANSYS? Will it increase the cost of the ANSYS licensing?
We expect FLUENT will be available within ANSYS Workbench by our next release, mid 2008. At that point, it will probably still look very much like it does now. Hosting it within Workbench will allow you to more easily access the CAD/Pre/Post/FSI capabilities that Workbench currently brings to CFX and ANSYS users.
As for the costs, those details have not yet been worked out. It will be competitive. J
Isaac: What kind of structural solver is used?
I am not clear what is being asked, but ICEM CFD can output to a number of popular solvers such as ANSYS, ABAQUS, LS-DYNA, AUTODYN, and NASTRAN. ANSYS Workbench currently supports ANSYS directly, but it is an integration platform and at least one customer that I know of has integrated other FEA solvers into ANSYS Workbench.
For the FSI examples shown in this presentation, ANSYS was the structural solver used.
Trevor: will version 12 include batch meshing for CFX?
I think this question is asking if 12.0 will include scripting for CFX Mesh (which we did not discuss in the presentation). I have been told that scripting in general was one of the most commonly requested features for ANSYS Workbench and it was a major focus of the new platform development. However, realistically speaking, the meshing in workbench will not be able to make good use of this until at V13.0 at the soonest.
If you were asking about batch meshing in ICEM CFD for use with CFX, then yes, you can do that currently and this will not be lost at V12.
Carol: I am a current FLUENT user and my colleagues are using ANSYS Workbench. What is the recommend roadmap for me to integrate my FLUENT skill set into Workbench environment? Can I use my colleagues' ANSYS Workbench license and using Workbench as my FLUENT preprocessor front end? What modules shall I download for this integrated environment?
As I told Catherine, FLUENT will initially be hosted in ANSYS Workbench, so you can bring your current FLUENT expertise with you. We expect you will be able to move over quite smoothly. The significant differences will be on the Pre/Post end. I think you will find the differences to be improvements.
Currently, in 11.0, there is an option in ANSYS Workbench meshing to output the mesh to FLUENT. You can also output to FLUENT from ICEM CFD. We already have a number of FLUENT users taking advantage of these tools to generate mesh for FLUENT and FloWizard.
Kevin: Is O-grid feature an additional add-on license required above current HEX and TET mesher?
No, sorry I wasn’t clear enough about this. OGRID and all the Hexa blocking tools are part of ANSYS ICEM CFD HEXA. Prism would be the unstructured equivalent and it is included with ICEM CFD Tetra for CFD users.
Kevin: Can you now move nodes on a hybrid mesh?
Movement of nodes doesn’t depend on the mesh type. However, it is possible that a node may become over-constrained. For instance, moving a surface node in a shell mesh is very easy. But moving an internal node between a number of prism elements may have some restrictions to keep you from twisting the elements. We can remove some constraints, contact technical support if you have a particular problem in mind (techsupp@ansys.com).
Ross: Your presentation has left me somewhat confused as to which features are currently available, which are to be available, and furthermore which licenses are required.
Everything I showed is currently available in the 11.0 release except for TGrid with advancing front refinement. Only TGrid with skewness based refinement was included in the 11.0 release, but you will need the 11.0.1 service pack to use TGrid with advancing front refinement. If you get the service pack, you will find a number of other improvements also.
Licenses are a bigger discussion. Inside ANSYS Workbench (which doesn’t require a license), I showed ANSYS DesignModeler which requires a license, I also showed ANSYS Workbench meshing which often comes with a solver key (the same way GAMBIT and TGrid come with FLUENT), or can be purchased in a bundle with ANSYS DesignModeler and ICEM CFD Tetra/Prism as “CAD2Mesh”. ICEM CFD is also licensed separately. You can get a configured key which gives you all the modules or your can buy Hexa, Tetra/Prism, BFCart, Quad, or Visual 3 as add on modules. For more detail and prices, please contact your sales representative.
Leon: I would describe this as more of a sales pitch than Advanced ICEM CFD training.
It was intended to introduce you to the ICEM CFD meshing tools. The actual Hexa training takes a full day, Tetra Prism takes another day. I could never cover that much material in an hour and a half long webinar. Instead I just spent a few minutes here and there on things like Octree subdivision and the Hexa blocking process so you could gain a better understanding of how things actually worked.
I tried not to be salesy. My apologies if it came across that way. We just had a lot to cover in a short time. If you want more info on any particular aspect that we covered, we can spend more time on that at a later point. Please contact me and we can talk or schedule a meeting.
Stephen: Will ICEM incorporate Polyhedral meshing in the future that is available in FLUENT?
ICEM CFD can currently display the mesh as polyhedral (The Mesh Dual), but we still output to FLUENT as normal tetra/prism/hexa/pyramid mesh. The mesh can then be converted again in FLUENT.
Down the road, there is talk of directly generating Polyhedral mesh, but no dates are set.
K M: Are tutorials available to download?
They are built into the software. Look under Help within the ICEM CFD GUI.
Try the Website www.ansys.com/demoroom/ to see virtual demos, some of which include quite a bit of detail and are useful as tutorials.
Ali: Can ICEM generate high aspect ratio triangles using TETRA?
We have several Tetra meshing algorithms. I assume you are referring to Octree patch independent tetra. No, Octree Tetra doesn’t do this.
If you mean thin tetras for boundary layers, we usually just convert prisms to tetras for solvers that can’t handle prisms.
We also have several surface meshing algorithms that can generate high aspect ratio quads. These methods can be used on the full model or can be easily combined with a dominantly Octree tri mesh. The resulting surface mesh with high aspect ratio triangles can then be used with prism and then Delaunay, Advancing Front or TGRID to generate the high aspect ratio tetras in ICEM CFD.
For external aero applications, I think MultiZone mesh is the best way to put high aspect ratio elements along a wing.
Ajit: Is ICEM is going to replace GAMBIT?
No. Longer term, geometry and meshing technology from both tools is being consolidated and integrated into the Workbench meshing application.
In the mean time, the next release of GAMBIT, V 2.4.6, is due out July 9th, 2007.
For ANSYS 12.0, we are working to ensure that the WB-based geometry and meshing functionality will be a suitable replacement for GAMBIT for most users. ANSYS DesignModeler (the WB-based geometry handling solution) is being enhanced to include GAMBIT-like virtual geometry operations. The ANSYS Workbench meshing application is being extended to include meshing technology from TGrid and ICEM CFD.
GAMBIT will maintained for a suitable overlap period to allow users to transition to Workbench-based meshing when it is most appropriate for them.
You might consider upgrading to ICEM CFD if you have trouble with your geometry or want to generate hexa meshes more easily/parametrically. See question 1.
Randy: When a model changes, how do you track the geometric settings from one geometry to the next?
For unstructured mesh, there are several layers of parameters; Global, “By Parts”, and “By Entities.” The parameter assignment to particular entity names is taken care of behind the scenes. When the model is parametrically changed and updated within ICEM CFD, those entity names remain the same and the associated entity parameters are maintained. If the change is more than parametric, and the entity names are lost, then at least the part or surface component names are often consistent so those parameters are maintained. For instance, maybe I wanted finer mesh on the part called “valve”. The new valve may have different entities, but at least the parameters and boundary conditions associated with “valve” will be transferred.
For structured mesh, things are a little bit different. The blocking is “associated” with the geometry entities. For instance a particular vertex may be 28% of the way along a particular named curve. Again, this is all done in the back ground so it is easy for the user. Sizes are part of the blocking file (Edge distributions), etc. so changing the length of a curve may trigger a parametric change in the length of the blocking edge which would then be remeshed according to the set parameters, adjusting for the length change. For parametric changes, there are commands to automatically update all the blocking to the geometry. For changes that are more than parametric, the user can interactively associate the blocking to the new geometry and further modify the blocking topology as desired.
A third way this is done is through scripting. For instance, the user may just create a script that could measure the length between two entities and divide that by a number and use the result as the mesh size. The script could then setup the other parameters, etc. generate the mesh, run mesh improvement cycles, set up boundary conditions and output to solver. This is typically all done in batch without even opening the software.
John: Can you repeat the part about importing Gridgen files? and output to another format
This actually works for any structured mesh format (TruGRID, GRIDGEN, GAMBIT, GridPro, etc), if you have the mesh in a format that ICEM CFD can read such as CGNS or FLUENT MSH, you can import it into ICEM CFD. You can extract geometry from this mesh or associate the mesh with the imported geometry using Build Mesh Topology. Then use the option under File => Blocking to “Load a Blocking from an Existing Mesh”. This converts the imported hexa into a blocking file. Depending on the complexity of the model, you may need to spend some time grouping curves and such to get the association correct. At that point you can toss out the original mesh and work with it as if you had done all the blocking inside ICEM HEXA. You can smooth, modify the blocking, fit it to a new geometry, etc. You can output the multi-block mesh or convert it to unstructured mesh and output to the solver of your choice.
If you have any questions about how to do this exactly, please contact tech support at techsupp@ansys.com.
Amit: UGI for GAMBIT and TGrid will remain same or clubed with ICEM
I am guessing that UGI is an acronym for “user graphical interface”, or GUI or UI.
No, GAMBIT and TGrid will not become like ICEM CFD. Let’s be careful and separate the product names from the technology. Products come and go; the technology is what is important. The technology doesn’t need to be confined to the product. For instance, the TGrid tetra meshing technology is now also in ICEM CFD. However, the TGrid shrink wrapper will likely never come into ICEM CFD, we will just skip that step and move it directly into ANSYS Workbench Meshing. As a product, neither GAMBIT, nor TGrid nor ICEM CFD will go into Workbench (natively), but their technology will.
There are no major GUI changes planed for GAMBIT, TGrid or ICEM CFD.
Scott: Do you anticipate the TCL scripting will remain the standard after all the CFX/GAMBIT/ICEM CFD capabilities are merged?
No, I don’t think so. TCL has a number of limitations that we would like to avoid in the new application. They have already moved to a more flexible and powerful language for the new interface, and I expect that when the scripting is implemented, it will also be enhanced.
We do not make these changes lightly; the benefits will be significant enough to justify rewriting scripts. If you have some fully automated scripts build on ICEM CFD technology, those will continue to run on ICEM CFD until the advantages of Workbench Meshing lure you over.
Emad: is the ICE3M will be in the Workbench
Perhaps. They are still working on the details, but the basic philosophy is that vertical applications like IC3M will be put into ANSYS Workbench if it makes sense to do so. Certainly, the platform is designed to incorporate things like this. Most vertical apps will not be added until after 12.0 is released.
I can also note that at the next release, the plan is that IC3M will be linked with Fluent and Fluent will be in Workbench.
Lucy: I have FLUENT license......will I need different license to use these tools?
Yes; see the answer I gave Ross for question 8
We still need to work out the finer points for 12.0, but we are looking at ways to unify our capabilities and develop attractive bundled pricing options for Fluent users.
Rodrigo: How helpful can ICEM be compared to the tools included in STAR-CD for meshing?
Many STAR-CD users use ICEM CFD to generate their mesh. The thing I hear most is that ICEM CFD is much easier to use than ProAM, even with the Navigator. But there are also technology reasons. Pro-AM has nothing that competes with ICEM CFD Hexa and they have no patch-independent meshing solution. On the other hand, ICEM CFD can not generate a polyhedral mesh or SAM cells, but you don’t really need these for StarCD.
Phone me for more info about how we compare with Pro-AM. 734 213 1217
jaewook: have you compared the computational cost between 32 bit and 64bit?
No, I don’t know of any official comparisons.
I am guessing that you are referring to problems some 32 Bit codes have with 64 bit due to swollen pointers and possibly other issues due to the 64 bit architecture occupying slightly more space in memory? I have not heard of computational cost with ICEM CFD, perhaps this is because it is intentionally compiled for 64 bit with the specific platform in mind.
I can say that 64 bit certainly increases the model size you can handle. With 32 bit windows, you are essentially limited to 2Gig or about 7 to 12 million Tetras generated in ICEM CFD. With 64 bit, you are limited by your computers memory. We have had users report generating 250 million tetras with 64 bit.
Consider that the range of integer values that can be stored in 32 bits is 0 thru 2^32 (4,294,967,295), therefore a processor with 32-bit memory addresses can directly access ~4.2 GiB of byte-addressable memory. There are operating system losses, etc. that reduce it down to 2GiB. Then consider that a 64 bit system has a range from 0 to 2^64 (~1.8 x10^19). This means the theoretical range for 64 bit can be about 4.2 billion times as big as a 32 bit system can handle. Therefore the bottleneck is only your available hardware (memory and CPU) and the number of CPU seconds you can wait (your life time).
Feng: So you mean if we have the license of FLUENT, we can freely upgrade to the Workbench?
At the current release, there is no reason to “upgrade” to Workbench. At the release of ANSYS 12.0 in 2008, Fluent will be integrated in ANSYS Workbench.
If you have Workbench due to other ANSYS products in your company, you can use Workbench meshing to generate mesh for FLUENT with the current version.
Feng: I am curious on the different between TGrid and ICEM CFD
Yes, since I had to rerecord the webinar anyway, I’ve made sure to include a lot more comparative information. I guess the first pass thru I was just meaning to inform, not contrast. You may want to listen to the recording again.
Some differences from TGrid
ICEM CFD has Geometry handling
ICEM CFD has Surface Meshing
ICEM CFD has more flexible Prism meshing
ICEM CFD has advanced Hexa/Hybrid meshing
ICEM CFD has a more modern, icon-based graphical user interface with model details organized in a tree structure and presented in a single window.
TGRID shrink-wrap has more control
TGRID Hexa Core has some advantages for FLUENT users
While we are at it, here are some differences from GAMBIT
ICEM CFD has more robust meshing (geometry independence)
ICEM CFD has interactive mesh editing
ICEM CFD has rapid parametric Hexa blocking, Hexa dominant and Body Fitted Hexa meshing.
GAMBIT has more advanced sweeping (“Cooper” tool)
GAMBIT patch based surface meshing is smoother for CFD (hooked up to sizing functions), ICEM CFD can only use sizing functions for patch independent surface meshing, so patch based meshing takes more interactive work to get the same effect.
Some users have been using tools in concert for many years. For example, I know of some advanced users that use GAMBIT to get the surface mesh and then take the mesh to ICEM CFD for Prism and Tetra. Other users with more challenging geometry used ICEM CFD patch independent surface mesh and then filled with a coarse TGRID tetra fill; now that TGRID tetra is inside ICEM CFD, this can be done with one click.
John: Is this web cast going to be repeated? Had difficulty connecting.
We had a number of people who had trouble getting in or had trouble with the phones.
We don’t plan to just repeat it, but I did record it and you can listen to that at your convenience. Sorry the first few slides of the recording were truncated some how so you didn’t hear my explanation that the original recording was lost, but at least I got to redo it with your questions in mind. I think the do-over was better than the original.
Schedules permitting, we could organize a more personal webex with you or your company during which we could more interactively discuss your needs and how we can work with you. Anyone who wants to set up such a meeting should just email me.
Santha: can we use the mesh created in ANSYS in FLUENT?
Yes, in the current release you can output a msh file to FLUENT from the Workbench meshing app or ICEM CFD.
Santha: what is Tgrid?
TGrid is a FLUENT meshing and mesh editing tool. It doesn’t really have a GUI, it has a “TUI” (Text User Interface) and it can generate principally tetra/prism meshes quite automatically. It also has a good set of diagnostic and mesh editing features. It has no geometry capability, so it generally requires you to input a surface mesh, but it can also take an STL file (still mesh really). More recent developments include Shrinkwrap and CutCell Cartesian technology.
TGRID is generally included (along with GAMBIT) with your FLUENT license at no extra cost.
Jamie: When do you anticipate V12 coming out?
ANSYS V12.0 is currently scheduled for release mid-2008.
Scott: What is your estimate for when GAMBIT will no longer be supported?
As development is focused on moving the GAMBIT technology into the new mesher, those resources are taken from the development of GAMBIT. Remember how we are separating the technology from the products… The transition plans are highly dependent on how quickly the developers can migrate all the tools. Development alone will probably need a year or two before most users will want to trade in their Gambit keys. Then the users can begin to transition, this will also take time. The product it’s self will likely be supported as long as there are sufficient Gambit users to justify support. Our next release of GAMBIT, V 2.4.6, is due out July 9th, 2007.
Bruce: Will FSI with ABAQUS require third-party data transfer software when using FLUENT or CFX for the thermal/fluid solution?
The improvements are on the Workbench platform, so unless ABAQUS is integrated, my guess is that the FSI with ABAQUS will continue to work just as it does right now.
As you should expect, FSI with FLUENT and ANSYS will be much more closely coupled and offer many advantages, but I don’t think there are any plans to abandon MpCCI-based coupling with ABAQUS.
Kevin: Can ICEM work with iSIGHT Optimization software? I presume yes because as I understand correctly everything in ICEM and Workbench can be done via scripts. Is this correct?
Yes, it is all scriptable and can be optimized with ANSYS tools or 3rd party tools like iSIGHT.
Santha: I bought the FLUENT student version. Can I be able to access ANSYS through FLUENT or can I be able to download ANSYS.
Student licensing is different, and they are still working out the details for merging in FLUENT student licensing. I can generally say that Workbench comes free with ANSYS ED, you can learn more about this ANSYS student product at http://www.ansys.com/products/ed.asp
Ultimately, we intend for the student version to be workbench integrated; but historically student versions lag a version behind the commercial version, so it may not be available with the first release of V12.
Catherine: How does ICEM compared to HyperMesh?
ICEM CFD is a competitor with HyperMesh.
HyperMesh has really good Mesh Morphing technology and a pretty mature connection to FEA solvers.
ICEM CFD and HyperMesh have comparable CAD imports, geometry repair, patch based surface meshing, bottom up tetra and FEA connectors.
ICEM CFD has strong advantages in scripting, parametrics and persistence, patch independent shells and tetra, Hexa and Hybrid meshing, body fitted Cartesian and prism meshing, mesh editing, contact detection, etc.
We have a number of testimonials from people who turned weeks of work into hours just by switching from Hyper-mesh to ICEM CFD.
In summary, for FEA shell meshing, it is a toss up. For CFD volume meshing, ICEM CFD has the clear advantage.
If anyone wants a much more detailed comparison, or wants to discuss this further, you can phone me at 734 213 1217.
Santha: what r the software’s in which we can create the mesh other than GAMBIT, ProE
I really don’t understand this question. Please try again.
Santha: is there any Workbench available in FLUENT
Not at the current release, but for the next release we are planning on releasing Fluent hosted within the ANSYS Workbench.

Best regards,

Simon Pereira
ANSYS ICEM CFD Product Manager
734 213 1217


变色龙Linux:SLE11 发布

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