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[Murtazo Nazarov <question103034@xxxxxxxxxxxxxxxxxxxxx>]

Question #103034 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/103034

Murtazo Nazarov posted a new comment:
Anders Logg wrote:
> Your question #103034 on DOLFIN changed:
> https://answers.launchpad.net/dolfin/+question/103034
>
> Anders Logg posted a new comment:
> On Sun, Mar 14, 2010 at 11:48:21PM -0000, Murtazo Nazarov wrote:
>   
>> Question #103034 on DOLFIN changed:
>> https://answers.launchpad.net/dolfin/+question/103034
>>
>> Murtazo Nazarov posted a new comment:
>> Murtazo Nazarov wrote:
>>     
>>> Your question #103034 on DOLFIN changed:
>>> https://answers.launchpad.net/dolfin/+question/103034
>>>
>>>     Status: Answered => Open
>>>
>>> You are still having a problem:
>>> Anders Logg wrote:
>>>
>>>       
>>>> Question #103034 on DOLFIN changed:
>>>> https://answers.launchpad.net/dolfin/+question/103034
>>>>
>>>>     Status: Open => Answered
>>>>
>>>> Anders Logg proposed the following answer:
>>>> On Wed, Mar 03, 2010 at 02:36:59AM -0000, Murtazo Nazarov wrote:
>>>>
>>>>
>>>>         
>>>>> New question #103034 on DOLFIN:
>>>>> https://answers.launchpad.net/dolfin/+question/103034
>>>>>
>>>>> Hi,
>>>>>
>>>>> I am wondering how to compute an L1-norm, and L_inf norm of a functional on the cell. For instance how to compute
>>>>>
>>>>> 1. ||\div(Pu)||_{L_\infty} ?
>>>>>
>>>>>
>>>>>           
>>>> Try projecting div(Pu) onto piecewise constants and then pick the
>>>> largest absolute value in the vector.
>>>>
>>>>
>>>>
>>>>         
>>> I need L_inf norm on the cell. With this way, doesn't give the L_inf for
>>> the entire domain?
>>>
>>> murtazo
>>>
>>>
>>>       
>> Instead of projecting div(Pu) onto piecewise constants, I projected it
>> into dG(1), with this way I get three values on each cell, which I can
>> then pick up the largest of them. That gives me then L_inf_K, where K is
>> a cell. Now, I cannot figured out how is the numbering done for the
>> dG(1) elements.
>>
>> If N is a total number of cells, then my projected vector Pdg has 3*N
>> elements. How can I pick up elements of Pdg in the cell K?
>>
>> Thanks,
>> murtazo
>>     
>
> Why do you use DG(1) instead of DG(0)? If you use DG(0), the numbering
> is easier.
>
>   

DG(0) gives me an average of the function I have on the cell, however 
the values can be large on the vertices especially in the places where 
shocks exist.

murtazo

> --
> Anders
>
>
>   
>>>>> 2. ||\div(Pu)||_{L_1} ?
>>>>>
>>>>>
>>>>>           
>>>> Try
>>>>
>>>> M = abs(div(Pu))*dx
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>         
>>>>> where u is velocity (vector) and P is pressure (scalar). L2 norm is obvious to do.
>>>>>
>>>>> I use C++ interface
>>>>>
>>>>>
>>>>>
>>>>>           
>>>       
>
>

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