Outlet Fluid Speed

When simulating inlet/outlet cases, it is quite common that the inlet fluid speed is known but outlet fluid speed is unknown. Is that possible to solve this kind of problems in DSPH? What is the correct configation of xml files for this kind problem?


  • I advise you to look through some of the examples for "inlet/outlet". What you request is possible, you have to use setting "2" and has been showcased in the examples, see for example "CurrentHull".

    Kind regards

  • <imposevelocity mode="2" comment="Imposed velocity 0:fixed value, 1:variable value, 2:Extrapolated velocity, 3:Interpolated velocity (default=0)"> </imposevelocity>

    do you mean that if the velocity is unknown, I should set the velocity mode as extrapolated velocity?

    I am simulating a pressure flow. the inlet velocity is known, and the outlet is a free outflow with the velocity and free surface unknown. so how to set the velocity, rhop and zsurf at the inlet/outlet respectively.

    if I don't add the outlet buffer zone and just let the particles run out of the calculation domain, would it affect the calculation, like the calculation speed and accuracy?

    kind regards

  • Normally one would specify an inlet velocity and a outlet pressure, and then the CFD simulation will figure out what the inlet pressure has to be to accomodate this inlet velocity and outlet pressure. I have never heard as such one specifying only velocities, since pressure differences is what drives the flow. It is in some software though possible to have inlet velocity, outlet pressure and then also velocity constraint on outlet - don't know if DualSPHysics allows for this.

    Hope it helps a bit

    Kind regards

  • thanks very much @Asalih3d

    you mean that I should specify inlet velocity and outlet free surface to simulate a pressure flow

    kind regards

  • My advice is to try some different options out and see how things go :-)

    CFD is pretty tough, the best way is simply to keep on trying and noting what one does etc.

    Kind regards

Sign In or Register to comment.