Re: Problems on the Cahn Hilliard Equation Example

Hi Zhiwen,

The grid spacing and time step are both too large. Change the maximum
time step to be 1 and the grid spacing to be 0.5 and the system will
remain stable and the overshoot above 1 and below 0 will also be
reduced significantly. I'll change the example in the manual to
reflect this

Cheers
.
On Tue, May 27, 2008 at 3:31 PM, Zhiwen Liang <lzwpurdue@...> wrote:
> Hi Daniel,
> The script I tested is the one in the example folder of fipy. I just made a
> small modification to print out the largest value and the smallest value of
> the variable, as attached. I run it as "python input2D
> --numberOfElements=10000 --numberOfSteps=100000". I also tried different
> mesh size and different time step size and they do not seem to help. Maybe I
> missed something.
> Regards,
> Zhiwen
>
> On Tue, May 27, 2008 at 2:09 PM, Daniel Wheeler <daniel.wheeler2@...>
> wrote:
>>
>> Hi Zhiwen,
>>
>> Can you pass me the script that you are using?
>>
>> Thanks
>>
>> On Sun, May 25, 2008 at 4:45 PM, Zhiwen Liang <lzwpurdue@...> wrote:
>> > Hi Daniel,
>> >
>> > I have a problem running the Cahn Hilliard Equation example. Maybe you
>> > know
>> > what's going on. Thank you in advance for any suggestion.
>> >
>> > I tried printing the largest and smallest value of the variable being
>> > solved
>> > at every time step. If I run it long enough, the variable goes to very
>> > large
>> > value (greater than 1) and very negative value, which is not physical.
>> > But
>> > if I change it to one dimensional, it works fine. Already tried
>> > different
>> > solvers in fipy but got the same results. Maybe you have some idea. I
>> > would
>> > greatly appreciate your advice.
>> >
>> > Thanks,
>> > Zhiwen
>> >
>> >
>> >
>>
>>
>>
>> --
>> Daniel Wheeler
>
>

--

-- 
Daniel Wheeler