# Problem with solve two differential equations.

1. Jul 21, 2011

### hoomanya

Hi,

I am trying to solve the two equations cited below but not sure if it is possible to solve them...

∂(yv)/∂t=f(y,v,t)
where v is velocity = dx/dt, and y is a material property.

∂v/∂x = constant

Any hints would be appreciated.

Many Thanks!

2. Jul 21, 2011

### coelho

Well... i would like to help, but there are some things i could not understand.

Is y a constant, or it is a function of v, t, or some other variable?

Is f(y,v,t) a given (known) function? (like f(y,v,t)=sin(y+v*t) for example)

And what are the variables you are trying to solve for?

3. Jul 22, 2011

### hoomanya

Hi,
y is a variable , say density and changes with time.
v is mesh velocity and and x is displacement. When I said ∂v/∂x = constant, I meant ∂v/∂h = constant, where h could be thought of as an element length in finite element. I'm not sure if that would make a difference.
I am trying to solve for y and v at each time step.
Thank you very much.