[yaseen wsu]

hello every one, I simulate free surface flow using transient simulation, but it need initial conditions like velocity, pressure ....., my direction of inlet flow is opposite to X,Y, so it is required to enter velocity in negative (like gravity) as shown in attached image.
thanks

http://www.cfd-online.com/Forums/att...1&d=1458157947

[ghorrocks]

I do not understand your question. But if you cannot define a good initial condition then starting from a zero flow initial condition usually works.

[yaseen wsu]

thanks, (actually I know initial condition only I have problem in sign) my question about direction of velocity, for example, when enter gravity acceleration we always put in negative (-9,806) when opposite to the vertical direction. for velocity, is the same thing when velocity opposite to the X or Y direction.

[ghorrocks]

Yes, if you want a velocity in the opposite direction to the axis definition this means the velocity is negative. This is how all vector quantities work, so it applies to displacements, velocities and accelerations and any other vector variable you need to define.

[yaseen wsu]

Thanks a lot