Learning Forum

[pankaj]

Hi everyone

I am trying to simulate drone fluid simulation in ANSYS fluent but not getting correct flow. What is the reason I am not able to identify.

There are two types of flow I was trying to  simulate one in linear direction also the rotation four rotors. But not getting exact  solution.

Can anyone guide me what is possible reasons for this problem.

 

 

 

[peteroznewman]

I expect you will get several more comments, here is my first observation: you need a much larger domain for the air. Try an enclosure that is at least 5 rotor diameters above the rotor and at least 10 rotor diameters below the rotor. Also make the sides of the enclosure at least 5 rotor diameters away.  The CFD experts may provide better guidance on these dimensions, but you can at least try that and see if it improves the result.

What boundary condition do you have on the six faces of the enclosure?  If any of the six faces are walls, that would be a mistake.

[pankaj]

thanks sir i will

Yes you are right I have defined boundary as wall what boundary should I used.

Now I am realising what mistakes I have done.

The boundary defined by  ANSYS Fluent by default is correct for flow simulation.

 

 

[Rob]

As Peter says the domain is far too small, and you also need to check the boundary between the rotors & main domain.  There are a few guidelines for how big the domain should be taken from the old wind tunnel best practice. Very roughly, use the outer domain as a guide and add one "box" upstream, 3 downstream, 2 above & 2 below plus 1 each side to start with (and fill in the corners so you've got a cuboid domain): if the rotors are running expect to need at least 4-5 boxes top & bottom. 

The above may also be difficult with the 512k cells you have in Student or Academic so you may want to review the meshing.

Outer boundary choice will depend on the way in which you're moving the drone. Assuming it's flying then upstream will be a velocity boundary and downstream a pressure outlet. Sides/top will be either symmetry or pressure outlet depending on whether the rotors are running: ie do you expect to suck/blow air out of the sides/top/bottom?