Understanding HFSS Memory Usage

[The Rat]

hfss memory usage

Hi all,

Stumbled across this website whilst do some research into understanding the memory usage for large models in Ansoft HFSS v10. I didn't find the exact answer I'm looking for, so I thought I would register and be more specific.

Currently I am (attempting to) simulate an industrial multi-mode microwave applicator, similar to a domestic microwave oven, just considerably larger. The typical dimensions are 1460mm long by 540mm wide by ~650mm tall. The general shape of the applicator is a V-shape with a flat top, and due to the irregular structure of the 8-waveports, there are no planes of symmetry. The frequency of operation is the standard for a microwave applicator in the UK - 2.45GHz.

The Validation process in HFSS states that "Given the specified frequency and model dimensions, an extremely large mesh will be required to produce an accurate solution. Your model and/or frequency units may be set incorrectly", thus confirming my concerns.

So this leads me to ask, is there any way of understanding the memory requirements of my model within HFSS, and ways to reduce these memory requirements of my model so that I can obtain a solution to my problem? I have the HFSS v10 User Manual but this does not allow me to understand memory usage. I have surfed the web for others that have similar problems and they either do not have model problems of the size I am looking at, else they can exploit the symmetry of the problem (something which I cannot do).

My current system specs are:

Windows XP SP2 (32-bit) - the OS set-up is optimised, i.e. only essential
applications are running
Pentium 4 2.2GHz Processor
2GB RAM

However (hopefully) will soon have access to a PC of the following (approximate) spec:

Windows XP SP2 (64-bit)
Dual-core 64-bit Processor
16GB RAM

Any pointers from the HFSS experts would be appreciated. Thanks.

 

[Azulykit]

extremely large mesh hfss

The short answer is use the 64 bit machine because it has more RAM. Try to keep the details in your model to a minimum and you will probably have a reasonable shot in getting the thing to run.

 

[The Rat]

reduce memory usage hfss

Thanks for the reply. Using the 64-bit machine is my intention, however even if I have access to it I still don't know how to quantify the memory usage for my model. As an example, I wrote a TLM solver which uses between 160-200 bytes per node dependant on node-details - hence I am able to taylor my simulation space and node-details according to my memory capabilities. This is something I can't seem to find from the HFSS documentation.

 

[Azulykit]

hfss reduce memory requirements usage

Have you tried your question out on one of the Ansoft application engineers?

I have not tried to estimate the memory requirements before hand although a quick look at the volume of your problem and the number of ports suggests that it will be large. I generally base my guess on size by the number of cubic wavelengths in the model and the detail. In this case eight ports would be a big adder as well.

You might want to build a very sketchy model of your applicator and see how it goes and then add detail. That could give you a hint of if it was even possible to go forward without spending a lot of time to find out that it is too big.

 

[The Rat]

hfss memory requirement

Thanks again for your reply. Yes I have been in touch with one of the Applications Engineers at Ansoft, however as of yet they have not been in touch with me regarding this.

Like you have suggested, I have tried to omit a much detail as I can focusing on the main cavity structure, and omitting the conveyor choke features which will add both size and details. As for how this will impact on the actual simulation results I am not sure, however it maybe the case that I won't get the chance to find out. At the moment I am down to the bare minimum details with a rectangular load and it still has insufficient memory - the problem is, I have no idea how much memory I need.

From my previous dealings with Ansoft's products (Q3D Extractor) I seem to remember there being a user group on the Ansoft website - can anyone remember where this is? In addition to asking here, it may be an idea to ask there.

 

[jiths]

hfss memory

hi
Is this message a warning or cant the simln be run.
I have come across such messages but could simulate.thepoint to be noted here is that the aspect ratio is very high..that is you have avery small structure and a larger one.Since the problem is multi mode there would be a lot of slots.
What i would suggest is manually seeding the meshin in such critical areas.This would help HFSS to start from that point
To validate the model you can calculate an electrical parameter say coupling from one slot , as suggested earlier