On Sat, Jan 21, 2012 at 1:22 PM, Rafael Calsaverini < [email protected]> wrote:
> Hi, > > I just found out about fipy so I was giving it a try. I found out the > nomenclature of the terms in the equations quite an obstacle though. Not > being > originally from the fluid dynamics community, some terminology is obscure > to me, > and the manual didn't quite illuminate for me how to write of a simulation > for a > arbitrary PDE. > > For example, I was interested, for example, in simulating the following > equation: > > du/dt = d/dx(v(u) u) > > with Neumann boundary conditions at u(0), for example, and > > (interpret d/dt and d/dx as partial derivatives) > > How do I translate this into the terms classes? > I think this is just a ConvectionTerm. A description of the convection term schemes are given on < http://www.ctcms.nist.gov/fipy/documentation/numerical/discret.html#convection-term> and <http://www.ctcms.nist.gov/fipy/documentation/numerical/scheme.html>. The only second order scheme is the Van Leer term < http://www.ctcms.nist.gov/fipy/fipy/generated/terms.html#module-fipy.terms.vanLeerConvectionTerm >. We are currently working on better Riemann based flux calculations for convection terms for future releases. > > I understand that du/dt is equivalent to TransientTerm() and that d( v > du/dx) is > equivalent to DiffusionTerm(coeff = v). > > My questions are: > > 1) how to insert a term like d( v u)/dx > Use a convection term. > 2) how to make v to be a function of u(x,t)? > Construct v from the u(x, t). See < http://matforge.org/fipy/browser/trunk/examples/elphf/phaseDiffusion.py#L152> for an example of constructing an operator variable that is used as a convection coefficient. Unfortunately, the FiPy web page doesn't have enough highlighted convection examples. They seem to be hidden away in the examples directory. -- Daniel Wheeler
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