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flow simulation on blade design is different from real life result

Question asked by Kai Chan on Aug 3, 2018
Latest reply on Aug 15, 2018 by Stephen Endersby

I am trying to create flow simulation of existing fan design. I have real-life lab test that I like to compare the accuracy of this simulation, but the result is far different from real-life test. Below is my summery of test:

 

Objective:

  1. Visialize air flow in 1.8m in front of fan blades, width 1.5m
  2. Find target wind speed at 75cm in front of fan blade, (done same things in real lab test, so I can compare them)

 

Problem on simulation result:

  1. The wind flow pic (trajectories) look different from different refinement level. I think my cell on solid-fluid, small gap, and the blade itselt is fine enough. But, I cant tell if this is refect to reality, I cant tell which/where the refinement is need in order to optimize the result that is close to real situation.
  2. Whatever resolution (or refinement level or cell) that I have set, the wind speed at 75cm location is far different from real lab test. (the lab result is around 1.3-1.6m/s, but simulation is only around 0.1-0.5m/s) At this point, I don’t quite believe on the trajectories result becauase the wind speed is dfifneret from real-life lab test

 

Setting highlight:

I have different set of refinement setting, and only keep all atmosphere pressure and density the same, rotation at fan blade is 800rpm, and all the goals is about velocity and z velocity in average + bulk. But all goals I set not to ‘use for convergence control’ because I don’t the calculation stop at any point so that I can visialize the whole air flow)

 

 

My question:

  1. Why with differnet refinement level setting, the wind speed result is still far different from real-lifel ab test?
  2. Could anyone suggest a right strategy on setting refinement level, so I know everytime when I update the cell, I can tell the new one is always better then old one, and my experiement is always a step closer to the reality. 
  3. Is anything other than cell/refinement level I set it wrong so that my wind speed result is different? Such as atmosphere pressure or density or anything?

 

attached pic are all my setting and result of final-try:

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