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Defining Ansys Superelement SUB File Manually

Photo by  James Owen  on  Unsplash A surprisingly popular blog-post written here is Exporting Stiffness Matrix from Ansys . A sensible follow up question is what can one do with the exported stiffness matrix? In a recent Xansys Forum post, a question was raised on how we can edit the stiffness matrix of a superelement and use it for our model.  An approach presented below is to first create a superelement that has the same number of DOF and nodal location that will serve as a template. An APDL script can then be written to edit the stiffness matrix entries as desired before exporting to a new superelement *.SUB file for use in future models. The self-contained script below demonstrates this.  /prep7 et ,1, 185 mp , ex, 1, 200e3 mp , prxy, 1, 0.33 w = 0.1 ! single element (note nodal locations) n , 1, w, -w, -w n , 2, w, w, -w n , 3, -w, w, -w n , 4, -w, -w, -w n , 5, w, -w, w n , 6, w, w, w n , 7, -w, w, w n , 8, -w, -w, w e , 1, 2, 3, 4, 5, 6, 7, 8 /solu antype , substr     ! analy

Ansys Student in the Cloud

Cloud Computing*?

Cloud computing is all the rage now for good reason. It is tempting to own a low cost computer and remote-desktop to a supercomputer. One could, in theory, run Ansys on Chromebook with internet connection by connecting to a Cloud Computing Providers Virtual Machine. I took a quick look and have the following to report.

Setting Up Windows Virtual Machine (VM) : Quick Start
Google Compute: YouTube 
Micosoft Azure: YouTube1 & YouTube2

Patience is key. After starting up the Virtual Machine for the first time, one has to wait a bit (15 minutes?) before the virtual machine really starts for one to remote login. I fiddled around with the "source IP ranges", setting it to and even my own IP address. It was unclear if that was useful or waiting alone did the trick.

Once logged in, one has to override the strict security set by the Internet Explorer to allow download of the free Ansys Student.

Finally, remember to Shut Down from the remote desktop and "Stop" the Virtual Machine once you are done to stop the usage-clock.

Google Cloud Platform
Google was the first Cloud VM I tried because it offered always-free option of a tiny vCPU and a generous 12 month use of $300. Unfortunately the instances offered by Google today are all vCPU. It means they are hyper-threaded. Ansys balked immediately with a Fatal Error. One could still solve by specifying 1 core. In short, Google Cloud is not a great choice.

Google Cloud Fatal Error with 2 Cores Requested

Microsoft Azure
I then looked at Microsoft Azure and Amazon Web Services, only Microsoft has some listed as "cores" instead of "vCPU". Here is their pricing. I picked Windows Server 2016 Datacenter Micosoft, Standard DS11 v2 (2 vcpus, 14 GB memory) and 128 GiB Premium SSD persistent storage for testing.

Azure sample estimated total cost :
$0.243/hour Virtual Machine 
( $17.92/month SSD 
   $5.89/month HDD )

Note that Azure allows for 200 bucks free credit for 30 days. To give an idea of how much it will take after the free trial, the running bill for VM and storage was ~$1.12 for my usage thus far for the installation of Ansys & a simple linear model solution while playing with it for the last 2 days.

From a time perspective, after clicking on "start" on the console, spin up time before usage could be 5-10 minutes before it would be instantiated. The response of the remote desktop is however quite speedy.

Competition Pricing
For commercial use, licensing could be tricky as Ansys has an approved partner list. When looking at pricing, here's how comparable hardware stacks up between Nimbix and Azure.

8 cores, 64GB RAM & 1TB storage
Nimbix   $1.25/hour + $80/month [pricing]
Azure     $0.90/hour + $40.96/month  [E8s v3  & S30]

While Nimbix is a tad more expensive, established expertise and experience in optimizing Ansys for the cloud may be worth every penny. 

First impression of running Ansys on VM looks promising. It might just work for specific use cases (e.g. students/hobbyist).


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