[hitzhwan]

How can we choose the residuals for the transient flow？ should 1e-3 enough or not? should we choose 1e-6? I see different people have different ideas. what is the difference between the absolute convergence criterion and relative convergence criterion？

[cfd2020]

Case in case for transient flows, in some type of transient flows the residuals never get small enough,for example :flow cross the cylinder

Originally Posted by hitzhwan

How can we choose the residuals for the transient flow？ should 1e-3 enough or not? should we choose 1e-6? I see different people have different ideas. what is the difference between the absolute convergence criterion and relative convergence criterion？

[hitzhwan]

Originally Posted by cfd2020

Case in case for transient flows, in some type of transient flows the residuals never get small enough,for example :flow cross the cylinder

What is the reason？ How can I solve it？ If I only set it as 1e-3， whether the results are reasonable?

[vinerm]

You can reduce the residuals but do note that the reduction in residuals do not directly translate to more accurate solutions. Therefore, you should not worry that much about residuals. Use monitors. Read Chapter 2, especially page 8 from the

https://books.google.nl/books?id=uSM...torial&f=false

[hitzhwan]

Originally Posted by vinerm

You can reduce the residuals but do note that the reduction in residuals do not directly translate to more accurate solutions. Therefore, you should not worry that much about residuals. Use monitors. Read Chapter 2, especially page 8 from the

https://books.google.nl/books?id=uSM...torial&f=false

I cannot understand its explanation in the book? Could you explain it easily for me which I can understand ? Thank you for sharing with the book? Could I download it？

[vinerm]

You don't need to understand much from the book. Don't start reading whole of it, only the content within the box on page 8. Rest is not important as of now. What you need to understand is that residuals are not always good indicators of the accuracy. All it talks about is that there are two systems of linear equations and both have same exact solution, u1 = 1, u2 = 2. However, when another solution is assumed, i.e., u1 = -0.95 and u2 = -1, it shows large residual for second case, which is good but small residual for first system. Though the solution is pretty bad yet the residual is small. In other words, small residuals don't translate to more accurate solutions.

No, you cannot download the book.