Re: euler without d/dt? time-independent conservation law.




"Helmut Jarausch" <jarausch@xxxxxxxxxxxxxxxxxxx> wrote in message
news:54qj34F2237qnU1@xxxxxxxxxxxxxxxx
Phil Scadden wrote:
Looking to solve time-independent conservation law.
[f(u)]_x + [g(u)]_y =0

with initial condtions u(x_0(t),y_0(t))=u_0

and boundary conditions u(x_0),y) and u(x,y_0)

snip
let's rewrite your equation to
(*) fp(u)*u_x + gp(u)*u_y=0 where fp(u) is the derivate of f at
u(x,y).

Now make the ansatz (characteristic) y= y(x), then

(**) d/dx (u(x,y(x))= u_x + u_y*yp where yp= d/dx y .
I'm having trouble with the notation. Can you describe further what you
mean with "characteristic?" "Ansatz" makes more sense.

'u_x' I think wants to be "u sub x" but I can't divine what 'u_y*yp' might
be. Gruss, LS


.



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