Learning Forum

[luke]

Hi,

 

I am experimenting with pressure drop across a pipe in discovery live and I am getting extremely high values. My method consists of a mass flow rate at the inlet and a 0 pressure at the outlet, then a mean face pressure probe at the inlet. Velocities in this particular application go up to 15-20 m/s to give you an idea of the mass flow.

 

The pipe is about 1m in length and approximately 1inch diameter and the pressure drop I am getting is way above 10bar on some occasions. The expected result should be somewhere between 2-6.

 

Can someone let me know the process in measuring pressure drop in the software to ensure I am doing it right, and also provide insight on the absurdly large results?

 

Additionally if someone could let me know if there is a way to include surface roughness?

 

Thank you,

 

Luke

[Brian Bueno]

LukePJCP

Are you able to share the model?  If not, can you tell me the thickness of the pipe and any other important details so I can try to reproduce the issue locally?

Have you tried increasing the fidelity setting to the maximum?

[luke]

I have attached the volume of the pipe, in this particular case it is circular with a wall thickness of around 12mm (but can be thicker at points of its height). 

 

Another pipe which is more of a duct with 10mm wall thickness also has the same problem.

 

I did change the fidelity slider to full fidelity and although it substantially reduced the pressure drop on both pipes, they were still extremely high.

🛈 This post originally contained file attachments which have been removed in compliance with the updated Ansys Learning Forum Terms & Conditions

[Subashni Ravichandran]

Hi  LukePJCP BBueno_ANSYS is currently unable to attend to your question so here's my two cents. I simulated the model that you shared with the boundary conditions that you have mentioned in your post. On my PC with NVIDIA  Quadro P5000 16Gb graphics card, at full fidelity, I got about 0.8bar pressure drop. (Refer image and file attached.) In Discovery Live the graphics card plays an important role in achieving better results. So, can you please share your Graphics card details?  

🛈 This post originally contained file attachments which have been removed in compliance with the updated Ansys Learning Forum Terms & Conditions

[luke]

NVIDIA Quadro P4000 is my graphics card, your pressure drop seemed more reasonable at first but you only have a 0.02 kg/s mass flow. I use ~8 kg/s, converted from the volumetric flow rate of 30 m3/h.

[Subashni Ravichandran]

Hi LukePJCP 

I recreated the simulation with 0.02kg/s flow rate to match your description of inlet velocity of 15-20m/s. At 8kg/s flow rate and the flow velocity at inlet is ~7500m/s which is too high and impractical to simulate in Discovery Live.

[devicechief]

Subashni Overall, I feel this is DL's biggest issue. Many users in the design world will not know offhand what reasonable limits are. Limits exist, but they are not enumerated. 

[luke]

I noticed you are using air, sorry I didn't mention it uses water not air. 

[Subashni Ravichandran]

LukePJCP We will check with the development team and get back to you.