[cheap_person]

hello and namaste all,
hope you are doing well.

I am generating a performance map of a centrifugal compressor.

I have to simulate a design point, where the boundary conditions are
rpm = 5000
pr = 1.5 atm

while processing the simulation:
1. I am keep getting this notice in cfx output file.
2. I have already run tens of simulations with same boundary condition, also keep getting constant residual lines even after 500 iterations. why?

Thank you,

sending you positive vibe
cheap person

[Gert-Jan]

This has been asked many times. Therefore a FAQ has been created. Please take a look:

https://www.cfd-online.com/Wiki/Ansy...f_an_OUTLET.22

[cheap_person]

Originally Posted by Gert-Jan

This has been asked many times. Therefore a FAQ has been created. Please take a look:

https://www.cfd-online.com/Wiki/Ansy...f_an_OUTLET.22

Thank you so much Sir Gert Jan, for your reply and reminding me of this page.
I'll go through this page, if I find any doubt I will bother you again. 😁😂

[cheap_person]

Originally Posted by Gert-Jan

This has been asked many times. Therefore a FAQ has been created. Please take a look:

https://www.cfd-online.com/Wiki/Ansy...f_an_OUTLET.22

Sir Gert Jan, I've been through your profile. You are an active senior member here since 2012 and also a CFD consultant.

So that, I am feeling very confident to ask questions that I wanted to ask an expert:
PS: you can answer in very general, or you can prefer your own posts on internet.

1. How do you approach a cfd problem?
2. How do you decide accurate model for a particular problem?
3. How do you come to the boundary conditions are correct or incorrect?
4. how do you select the target for residuals for cfd problems?
5. How do you study the results and take decision over it?
6. What are those mistakes you did in your beginnings that you tell a
beginner to not to repeat?
7. what would you advise me as a beginner in my cfd journey?

Waiting for your answer! 😌

Sending positive vibes!!!
cheap person

[ghorrocks]

There are a few long term CFD experts on this forum. We are very fortunate to have all this experience available to us.

Here are my answers:
1) That is a complex question which is not feasible to answer in a forum post. Do a university CFD/fluid mechanics course and that will give you a start.
2) See FAQ https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F and https://www.cfd-online.com/Wiki/Ansy...publishable.3F
3) See point (1), but also the section in the CFX documentation on choice of boundary condition is useful.
4) A sensitivity analysis.
5) See point (1), that is what makes a CFD professional a professional.
6) Ha ha, that was along time ago and I have made many, many mistakes over the years. But be open about your mistakes, accept useful advice when it is offered and make sure you know what you are doing and why you are doing it.
7) See point (1). The main starting point is university CFD/Fluid mechanics courses, and consolidate it with post-graduate work on the topic. This Forum can help you when you have specific questions and problems.

[cheap_person]

Originally Posted by ghorrocks

There are a few long term CFD experts on this forum. We are very fortunate to have all this experience available to us.

Here are my answers:
1) That is a complex question which is not feasible to answer in a forum post. Do a university CFD/fluid mechanics course and that will give you a start.
2) See FAQ https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F and https://www.cfd-online.com/Wiki/Ansy...publishable.3F
3) See point (1), but also the section in the CFX documentation on choice of boundary condition is useful.
4) A sensitivity analysis.
5) See point (1), that is what makes a CFD professional a professional.
6) Ha ha, that was along time ago and I have made many, many mistakes over the years. But be open about your mistakes, accept useful advice when it is offered and make sure you know what you are doing and why you are doing it.
7) See point (1). The main starting point is university CFD/Fluid mechanics courses, and consolidate it with post-graduate work on the topic. This Forum can help you when you have specific questions and problems.

Hello again my dear sir Glenn!!!
Thank you so much for being here and answering. ❤️

I read your message with open my brain.
I think I've have cleared all of my doubts via your valuable message. which is super crispy and to-the-point.

But I noticed, you kept emphasizing "study fluid mechanics from university". After this, I found myself having a weak foundation in this subject. From today, I'll start working on it.

And point no 6, you made this it cherry on the top. I'll make sure consider your advice from the next simulation.

sending positive vibes!!! 😁😁✨
cheap person

[Gert-Jan]

Keep asking.
Unless asked many times, stupid questions do not exist. Stupid answers can be found everywhere.

[cheap_person]

Originally Posted by Gert-Jan

Keep asking.
Unless asked many times, stupid questions do not exist. Stupid answers can be found everywhere.

I'm sorry sir, if I made you disappointed, I had no intention anywhere.

[Gert-Jan]

No, not at all. I want to encourage you to ask questions.

I say that stupid questions don't exist. Only stupid answers exist.
Unless questions are asked multiples times and the answer is around the corner.