Learning Forum

[abhishek.srivastava2]

Hello everyone,

I have a pipe flow as shown in the image. The air enters the pipe through an orifice (supposed to be a hole in actual pipe). I created a regiuon around the orifice to create a real flow situation from all around the pipe. The air is being sucked from outlet using a negative pressure generated by fan. Please let me know what can i improve in the design (what i think is the problem) to improve the flow. Please find attached images. BC (0 Pa pressure inlet, -100Pa pressure outlet, can't change bc to velocity inlet, this is the correct bc). SIMPLE scheme, steady state. the area around the orifce is given 0Pa (inlet). 

[Rob]

What's the operating pressure? Please show the mesh in the orifice. 

[abhishek.srivastava2]

Please find the mesh images. Operating pressure is default (101325 Pa). 

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[Rob]

Please plot on a plane down the middle. 

[abhishek.srivastava2]

Hello,

Apologies for the delay. Please find the new mesh images and velcoity at the orifice edge and let me know the feedback. 

 

 

 

 

 

[Rob]

The mesh doesn't look too bad. How many iterations have you done? With 100Pa loss against ambient, can you not use a velocity boundary and find the domain dP? I'm assuming ambient is STP?

[abhishek.srivastava2]

The BC conditions need to be maintained. It's a fan the end of pipe which sucks the air into pipe throiugh the orifice. So, i can only control the fan speed (outlet pressure). Previously i had the environent box in the shape of a big cylinder around the orifice to get air from the two side and front of the orifice, and that design worked perfectly but i was getting an error of more than 10% in required velcocity. So, i changed the cylinder box design and extended it more towards the side wall of the pipe to have more air into the pipe (and more close to real scenario) but seems this design is causing sudden fluctuations and solver is not able to capture the entrance velocity correctly. I'll try to refine the mesh little bitmore to see if it improves anything. 

[Rob]

Run with a velocity boundary and see how the flow behaves. How is the convergence looking?