Error in CFD online course Elbow duct.

Hi Rishi,

please note: This is "just" a warning and not an error. The message means that simulation reached the number of iteration without meeting the specified convergence criterion (see the screen shot below where you can specifiy these settings). In our everyday CFD projects we have this quite often and in most of the cases (if carefully cheked) the results are very reliable.

Having said this, the case of challenge 2 should meet the convergence criterion. So it is very likely a setting in your setup differs from the values in the hand-out. So I would advise you to go through all the settings (once again). Please also check your mesh settings. Make in particular sure that the visous layers are only activated on the wall. Viscous layers should not be activated on inlet and outlet.

Best regards
Manuel

Thank you for the information, I get to know that my simulation result gets converges when i increased the iterartions otherwise the convergence criteria. so can you give some information on what we should change wheather it ts convergence criteria or iterations, Also one thing to add upon when i increased iterations it takes me much more time to compute so is there any way to accelerate the computation.

Hi,

I had same issue, I re-checked all the values 3 times. Then I noticed I entered the Inlet velocity as 10 m/s and not 10.0 m/s

I therefore used 10.0 and it converged... I also used a CFL of 1.5 instead of 1

Could it be that the inputting an integer number causes convergence troubles? I'm pretty sure all the rest was set properly

Hi,

I had same issue, I re-checked all the values 3 times. Then I noticed I entered the Inlet velocity as 10 m/s and not 10.0 m/s

I therefore used 10.0 and it converged... I also used a CFL of 1.5 instead of 1

Could it be that the inputting an integer number causes convergence troubles? I'm pretty sure all the rest was set properly

Hi Commodaro,

this should actually make no difference. I always enter the value without decimals (if not needed). Please try the following: enter 10 and the click with the mouse into another field. It should be then expressed as 10.0. To understand where the problem is coming from, may I ask you to do the same as Rishi above please. Could you please provide me screen shots of the following:

• The generate grid. Please choose a similar view as in the hand-out
• Properties of:
  • Domain: Physics - standard settings
  • Domain: Initial solution - standard settings
  • Domain: Numerics - standard settings
  • Boundary condition: duct wall - standard settings
  • Boundary condition: inlet - standard settings
  • Boundary condition: outlet - standard settings

Best regards
Manuel