topic Re: Need help in creating QH curve for centrifugal pump. in CFD Forum

Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Thu, 02 Nov 2017 05:22:31 GMT

Dear All,

I have run one iteration of centrifugal pump assly with impeller successfully by creating surface groups 'Inlet' and 'Outlet'.

I then followed this webinar to plot QH curve using pump automation tool.

But I am getting an error Section 'Outlet 2' missing(Please find attached screenshot). Could you please help me out with it ? I would really appreciate for the help.

Re: Need help in creating QH curve for centrifugal pump.

Amal.C — Thu, 02 Nov 2017 08:10:53 GMT

Hi,

Thanks for reaching out to our CFD forum 🙂

I see that you created a group named Outlet2 where you did not assign any surface to it. Can you please delete "Outlet2" by keeping only the two groups "Outlet" and "Inlet" and try launching the automation tool again?

Thanks,
Amal

Re: Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Fri, 03 Nov 2017 04:08:15 GMT

Hi Amal,

Thanks for quick response. I tried again by keeping only two surfaces 'Inlet' and 'Outlet'. But still its showing same error. Please find the attached screen shot. Request you to help what's going wrong with it.

Re: Need help in creating QH curve for centrifugal pump.

Amal.C — Fri, 03 Nov 2017 08:48:38 GMT

Hi @vyas.harsh.d,

Thanks for your feedback!

After removing "Outlet2" from the Goups tree:

did you make sure to delete all the previously automatically generated scenarios and start over the process from only one scenario?
Did you re-start the CFD program?

If yes, then I suggest that you share with me your support file so that I check for you where the issue is?

Thanks,

Amal

Re: Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Mon, 06 Nov 2017 13:47:39 GMT

Hi @Amal.C ,

Yes I created the simulation from scratch again. Today I again tried with the tutorial file provided. But I am facing the same problem again. I am attaching the support file for your review. I really appreciate your response. Will be awaiting for the solution.

Regarding the first result that I had run, The pressure is increasing upto 50 time step during ramp up. But it then drops for some iterations and then becomes stable.(I am not able to understand why its happening Please find attached screenshot for your reference)

Re: Need help in creating QH curve for centrifugal pump.

Amal.C — Mon, 06 Nov 2017 19:20:04 GMT

Hi @vyas.harsh.d,

I will take a look at your file and let you know 😉

Thanks for sharing it with me!

Amal

Re: Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Fri, 10 Nov 2017 09:44:33 GMT

Hi @Amal.C,

Did you get chance to review the file which I submitted ?

Please let me know if you require any furthur information related to it.

Re: Need help in creating QH curve for centrifugal pump.

David.Short. — Fri, 10 Nov 2017 10:37:22 GMT

Hello @vyas.harsh.d,

I am attempting to recreate your issue however the tutorial based scenario that you sent runs fine on my machine.

To clarify, are you receiving the same "Section 'Outlet 2' does not exist" error when running the tutorial based simulation?

Also, which CFD version are you using?

Regarding your query over the pressure residuals plot, it looks fairly characteristic of a ramp up and settle out.

Thanks,

David

Re: Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Fri, 10 Nov 2017 11:14:57 GMT

Hi @David.Short.,

Thank you for the response. One scenario runs fine with me too. But I am getting error when I am trying to generate Q-H curve using addin.

Yes I am getting the same error "Section 'Outlet 2' does not exist" while running the simulation in tutorial file. I am using AUTODESK CFD 2017 version.

Also could you explain what does this error mean?
"Section 'Outlet 2' does not exist"

Re: Need help in creating QH curve for centrifugal pump.

David.Short. — Fri, 10 Nov 2017 13:33:35 GMT

Hi @vyas.harsh.d,

Firstly when using the pump addin don't apply boundary conditions as the addin will take care of this for you.

Here is the documentation regarding usage of the pump simulation tool.

I am fairly sure that the error you are receiving is still due to some dependents created when you made the 'Outlet 2' group by accident. Please try closing CFD and then import the geometry again and see if the error persists.

I hope this helps.

All the best,

David

Re: Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Tue, 14 Nov 2017 05:26:56 GMT

Hi @David.Short.,

Don't apply boundary conditions ? But before using addin you need to run one case successfully for addin to work.

The link of the document is not working properly. Could you please share the link to document again ?

I did the above simulation from scratch i.e. new from beginning (Using native CAD file) discarding the older one. I didn't add surface 'Outlet 2' group in the file which I have submitted above for your review.

Adding to above points I tried again without adding any groups to the simulation. the first one ran successfully but the addin is showing same error for other 10 results which are run. (please find attached image screenshot for details)

I would like to ask are you able to plot Q-H curve using addin ?

Could you please share your detailed process while using addin ? (Using screenshots ?)

This would help me more where I am making mistakes.

Re: Need help in creating QH curve for centrifugal pump.

David.Short. — Tue, 14 Nov 2017 08:07:44 GMT

Hi @vyas.harsh.d,

Really sorry about the faulty link. Here it is again.

Or here: https://apps.autodesk.com/SCFD/en/Detail/HelpDoc?appId=3576057998749906699&appLang=en&os=Win32_64

The "Outlet 2" error is certainly a strange one. I will do some digging!

Thanks,

David

Re: Need help in creating QH curve for centrifugal pump.

David.Short. — Thu, 16 Nov 2017 08:32:51 GMT

Hi @vyas.harsh.d,

How are you getting on with your project?

I am unfortunately still none the wiser regarding your "outlet 2" error but I am almost sure it must be due to dependents remaining (maybe linked to the API) from when you accidentally created two outlet groups. Are you sure that you've started completely from fresh with the design study?

Thanks a lot,

David

Re: Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Fri, 17 Nov 2017 04:59:49 GMT

Good Day @David.Short.,

I am attaching a file which shows detailed information of what steps I am following. Today I started the simulation from scratch with loading up new CAD tutorial assembly. Request you to look into it and let me know on which step I am missing out.

Re: Need help in creating QH curve for centrifugal pump.

David.Short. — Fri, 17 Nov 2017 13:57:20 GMT

Good afternoon @vyas.harsh.d,

Thanks a lot for giving such clear instructions such that i could follow your workflow!

I repeated your process and got the same error to my surprise, so sorry for doubting you, it was just a crazy coincidence that you had created an "outlet 2" previously!!

I think I have also found the cause. When creating your groups you must deselect all after creating your inlet as if you don't you assign the outlet to the inlet again (hope that makes sense). You then have two surfaces as outlet hence the error. Please try creating your groups again ensuring only one surface per group.

Thanks,

David

Re: Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Fri, 17 Nov 2017 14:29:59 GMT

Hi @David.Short.,

Thank you for your response.

I had noticed that in my previous simulation trials. But I did took care of it since then. In this file you can see in point no. 10 and no. 11 Screenshots. I have defined only single surface for each 'Inlet' and 'Outlet'. I took utmost care that two surface are not selected in a single group.

Request you to re look at it.

Also could you post a workflow of yours in which Q-H Curve is plotted at the end using the addin tool ? So I might get idea where I am making the mistake ?

Again Thank you very much for your efforts.

Re: Need help in creating QH curve for centrifugal pump.

David.Short. — Fri, 17 Nov 2017 16:14:06 GMT

Hi @vyas.harsh.d,

Ok I see you have created groups correctly. I have followed suit and like you get the same "Outlet 2" error.

Here is how to avoid it (hopefully):

Don't run scenario 1 until you have setup the other scenarios with the Pump API.

Don't assign boundary conditions to your scenario one. As I have said in previous posts the Pump API creates them for you. Set the GPM value (Gallons per minute mass flow rate) to equal your intended mass flow rate BC (60kg/min =~ 16GPM).

Don't touch the time step or number of steps as again the Pump API will handle it using your specified number of blades, degree increments and desired revolutions.

I have attached a screenshot of the values I have used in the pump API and a .cfz file with a setup which should result in a pump curve after each scenario has been solved and the "Process data" function has been used.

I hope this solves your issue.

All the best and have a good weekend,

David

Re: Need help in creating QH curve for centrifugal pump.

vyas.harsh.d — Mon, 20 Nov 2017 12:05:19 GMT

Dear @David.Short.,

Thank you so much for digging out the error. I think now its working. I missed the point about ' not defining the boundary conditions in the beginning". I am currently running the simulations . Lets see how it goes.

By the way if we are not defining the boundary conditions then how does it take the direction of the flow rate at the outlet ?

Again thank you very much for the help. It made sense a lot. Will come back to you if there is any issue further.

Re: Need help in creating QH curve for centrifugal pump.

David.Short. — Mon, 20 Nov 2017 12:54:52 GMT

Hi @vyas.harsh.d,

I'm glad that you are now making some progress. The outlet flow direction will be defined by the direction of rotation of the impeller.

Thanks a lot,

David

Re: Need help in creating QH curve for centrifugal pump.

David.Short. — Thu, 23 Nov 2017 13:28:59 GMT

Hi @vyas.harsh.d,

I would like to follow up on this thread.

If you think that I or another contributor have answered your question / solved your problem please can you mark the relevant post as an accepted solution, alternatively you can allow me to mark it as such. This will help others to benefit from the discussion and easily find the solution if they have a similar issue.

Thanks a lot,

David