[ruchit@15847]

Pls find the necessary pics of velocity an total pressure in stationary frame.

Inlet BC : 2.4 bar total pressure in stationary frame
Outlet BC : Mass flow

After simulation:
Inlet Total Pressure :67.86 bar
Outlet Total Pressure : 9.51 bar

[Gert-Jan]

I asked velocity in stationary frame. Not Velocity. So please plot the Velocity in Stationary frame. And not as vectors but as contours. Also, add small black vectors (on top of it) of velocity in stationay frame (1000 vectors, equally spaced, projected tangential)

Also calculate the total pressure drops in stationary frame.

And remove the blue background. Blue vectors on a blue background is a very bad idea. Don't you think?

[ruchit@15847]

Pls find the updated pic of velocity in stationary frame.

I am not getting which total pressure drop u r asking.

[Gert-Jan]

You mentioned:

After simulation:
Inlet Total Pressure :67.86 bar
Outlet Total Pressure : 9.51 bar

If you want to evaluate pressure drop, then you need to evaluate the values in stationary frame.

[ruchit@15847]

Yes..This values are evaluated in stationary frame.

[Gert-Jan]

Regarding your first velocity vector plot, what do you think of the direction of the vectors?

[ruchit@15847]

R u asking why the direction of vector is towards inward ??

Let me know u I am rotating domain in -40000 RPM (i.e. direction of rotation is negative Z direction). Stationary coordinate system is such that positive Z is coming out of the plane for all pics I have uploaded.

Are u thinking that the sense of rotation of domain is wrong?

[Gert-Jan]

I don't know how everything is orientated since your axis is invisible. Neither do I know if your origin is in the center. Please check.
Anyway, the rotation direction is wrong. Don't you think, based on the vectors you plot?

[ruchit@15847]

Ok. I will check the direction of rotation. But, Is it necessary that the axis about which the pump is rotating should pass through the origin of the pump? Like I have shown in attached fig.

[Gert-Jan]

No, it is not necessary to rotate around the origin. You can rotate around any axis you like. As long as it is in the middle of your rotor. Better check this!

Nevertheless, the rotor should push the fluid towards the outlet (since you say it is a pump....). So if you look to your geometry, then the rotation direction is clear, isn't it?

You could argue about the rotor itself. Isn't it inverted?

[ruchit@15847]

Yes. I cheeked. The rotational axis and central(middle) axis of the pump was not matching. Now I corrected and running the simulation. I will let u update.

But one more question : Since I am running at such a high RPM of 40000, should I increase the RPM in simulation gradually or should I run the simulation directly at 40000 RPM ?

[Gert-Jan]

That depends. It could be that CFX survives a start from scratch. If not, then ramp it in 3 steps. Should be enough.


BTW, why do you remove the pictures?

[ruchit@15847]

Now, I matched the rotational axis of pump with central axis which also solved the direction issue of vectors in Impeller blades which u can see in attached figure.

Inlet BC : 2.4 bar (Total Pressure in Stationary Frame)
Outlet BC : 4.89 kg/s

After Simulation:
Total Pressure in Stationary Frame at Inlet: 2.4 bar (Now it is coming)
Total Pressure in Stationary Frame at Outlet: -13 bar

Total Pressure in Stationary Frame at Interface between Impeller and Volute = 44.081 bar which is less than Total pressure in Stationary Frame at Outlet. I don't know why it is reducing ?

Direction of Rotation : -40000 RPM (Direction of axis of rotation in negative Z direction)

Pls find the attached figure of Contour of Total Pressure an Velocity (both in Stationary Frame). In Figure, Positive Z axis is coming out of the Plane.

I had to delete the pics due to confidential.

[Gert-Jan]

As mentioned before, your impeller needs to be inverted. It looks like you have chosen a turbine geometry and use it as a pump. This can't work at all.

[ruchit@15847]

My impeller is inverted means sense of rotation of impeller is wrong. Right??

I am also running one more simulation with opposite rotation as compared to previous one. Still Simulation is running but here I am getting Good result. I will update once it will finish.

[Gert-Jan]

Impeller geometry is not a pump but a turbine. You can't pump with it.
Rotation direction is right.

[ruchit@15847]

How r u judging my impeller geometry is not pump but turbine? Are u judging based on the higher inlet pressure than outlet pressure?? May be I am missing somewhere else in setup in simulation ??

[ruchit@15847]

I did two simulation with same Geometry with same case setup except direction of rotation of rotor.

For both simulation, I gave following BC :

Inlet BC : 2.4 bar (Total Pressure in Stationary Frame)
Outlet BC : 4.89 kg/s

Simulation 1: With -40000 RPM (axis in negative Z direction)
Total Pressure in Stationary Frame at Inlet: 2.4 bar
Total Pressure in Stationary Frame at Outlet: -13 bar

Simulation 2: With 40000 RPM (axis in positive Z direction)
Total Pressure in Stationary Frame at Inlet: 4.1 bar
Total Pressure in Stationary Frame at Outlet: 165 bar

[vivjk94]

Hi, my question is related to the post. i doing centrifugal pump simulation in 2.5D using steady frozen rotor approach in fluent. I would like to know how to calculate the meridional velociity?
what do i need to do to calculate the discharge coefficient, hydraulic efficiency and other parameters?
please help me

[ghorrocks]

What do you mean 2.5D? I use 2.5D to mean where the flow domain is 2 dimensional, but you are modelling 3 velocity directions - so you are including out of plane velocities. This is usually done with a periodic boundary.

I cannot see how you can model a centrifugal pump in 2.5D, as I understand it.

Also - this is the CFX forum, for questions about Fluent try the fluent forum. But your question seems to be more about post processing anyway.