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-   -   High Resolution (CFX) vs 2nd Order Upwind (Fluent) (http://www.cfd-online.com/Forums/ansys/75938-high-resolution-cfx-vs-2nd-order-upwind-fluent.html)

gravis May 10, 2010 07:11

High Resolution (CFX) vs 2nd Order Upwind (Fluent)
 
Hi all,

I am wondering about the similarities between the advection schemes "High Resolution" and "Second Order Upwind" in CFX and Fluent, respectively. As I understand it, the principles behind the schemes are the same;

CFX: \phi_{ip}=\phi_{up}+\beta\nabla\phi\bullet\bar{r}
Fluent: \phi_{f,SOU}=\phi+\nabla\phi\bullet\bar{r}

In CFX, \beta is limited to prevent under/overshoots. In Fluent, the gradient is limited to prevent under/overshoots.

In the CFX documentation, it is decribed how \beta is calculated at each integration point/control volume surface while in Fluent it is not. Does this mean that in Fluent, basically a value corresponding to \beta in CFX is calculated to limit the gradient, and that the Fluent scheme is also bounded? If it is so, is this value calculated similarly to how \beta is calculated in CFX?

Thanks in advance.

Best regards,
Reine

gravis May 10, 2010 10:13

Wrong...
 
I realized my mistake: the details of the limiter in Fluent are actually described in the documentation. It seems that the limiter used in the High Resolution scheme corresponds to the "Standard Limiter" for Second Order Upwind in Fluent; both are based on principles by Barth and Jespersen.

gravis May 11, 2010 02:35

Additional question
 
In CFX-Post, there are variables with names "-beta" that indicate the value of the limiter \beta in each control volume.

Does anyone know if there are corresponding variables available in Fluent, and what their names are? I have not found any variables that I think match. In the Fluent documentation, the scalar that limits the gradient is denoted \psi.

lzw2003 March 24, 2011 03:43

about upwind node
 
i just read the cfx theory , and find its high resolution schemes. as a comment question, i want to know how the wpwind node is found? just mathmatic method or other method?


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