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Axial Fan transient simulation results mismatch with datasheet

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Old   July 20, 2020, 01:45
Default Axial Fan transient simulation results mismatch with datasheet
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Varun V P
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Hello there,
I've been trying to simulate a small axial fan working as a suction device for an air quality sensor. The mass flow rate is something that needs to be accurate, and hence I started a transient simulation of the spinning fan, housed at the end of a box where the sensors will be.
description.jpg
Inlet is the at the left, and outlet is at the right, just after the fan. I have set both of them as a pressure boundary condition, 0 Pa.

I put an inflation layer on the blades surfaces, and I have proximity meshing enabled for the thin gap between the fan blade and the wall. Note that the wall around the fan blades is stationary, and I've made sure of this in the BCs.
mesh_blade.jpg
mesh_blade_tip.jpg
The rest of the body I have meshed with MultiZone, and there is a nonconformal interface between these 2.

Now coming to the solver, I have used the SST model, with curvature correction and low reynolds number correction enabled. Please tell me if this is acceptable. I am using the sliding mesh method, and the fan is spinning at 6500 RPM.

outlet_bc.PNG
Note that I disabled the average pressure specification because the solver gave a warning. I should have also disabled the normal to boundary condition.

These are the solution methods for the initial run.
soln_methods_2.PNG

After running for 500 timesteps, each of 0.0005 s, with 20 iterations each, I get a flow rate of around 46 lpm, which is 10 lpm higher than what the manufacturer states, for an atmospherics static pressure! I am now continuing the simulation with a second order run of the variables. I will attach the image of the wall y star values in the comments, if I can. They're all around 1 on the fan blade. Can anyone tell me what I'm doing wrong, and any recommendations to increase accuracy? Has anyone got such parameters to match to the simulation?
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Old   July 20, 2020, 01:54
Default Some more images
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Varun V P
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I have attached images of the wall ystar on the fan blades, and a wireframe view of the mesh.
Attached Images
File Type: jpg flow_pathline.jpg (179.3 KB, 4 views)
File Type: jpg wall_ystar.jpg (67.8 KB, 3 views)
File Type: jpg wall_ystar_side.jpg (70.4 KB, 3 views)
File Type: jpg mesh_front_fan.jpg (132.8 KB, 1 views)
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axial fan, sliding mesh, sst kw, transient analysis

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