Free flowing simulation

Hi Everyone, hope you’re doing good.
Kindly please provide support for a flow simulation I’m trying to do.

project support

I’m not an expert with flow simulations. The link that I had attached has a “Y-like” pipe with 1 inlet and 2 outlets, one diverging upwards and one downwards. The fluid medium is water.
I didn’t assign any pressure and run the simulation with 10 m/s at inlet, after the simulation, I could see 5 m/s at both the outlets.
Here’s what I want to know/do :slight_smile:

  1. There is a velocity increase just before the diversion in the pipe, why ?

  2. I want to do a simulation with no continuous flow, for example, If you feed/pour/splash water inside a pipe and leave, in real experiment, the water coming out from the lower end of the pipe should be faster since it would face gravitational force and the water that diverged and went upwards should face negative gravitational force and slow down, so the velocity of the fluid coming out from one end should be faster and the other end should be slower. How do I apply gravitational force to act on the fluid flowing throughout the pipe. Kindly, please help me with what parameters I have to input to run a simulation like this. (if possible, please provide a tutorial link if possible).
    Thanks in advance

Hi, and thanks for reaching out!

To answer your questions:

  1. The inlet BC applies a constant flow speed across the whole face, while in reality the flow profile in a pipe is a parabola. The velocity change you see is a transition from the artificial constant profile to the real ‘developed’ profile downstream. Also, back-pressure from the split can affect the inlet flow. This is why it is always recommended to extend the inlets several diameters in length, to allow for the flow to develop the correct profile.

  2. There is no gravity effect in the Incompressible model.

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Thanks very much for the information