Learning Forum

[ghassan.abusultanah]

I am trying to run simulation for laminar flow using perforated plate, When I used default setting I get good result without achieve the target velocity. Once I change the values to calculated values as per attached the results looks 0 fps in the space . what is the right way to simulate the thin perforated plates as pours media and get right results ? the calculated K values and   Viscous resistance coefficient (C1) f Forcheimer Coefficient attached too . 

[Charudatta Bandgar]

Hello Ghassan. AbuSultanah ,

 

I will need to investigate this further, and I will get back to you regarding it with my findings, as soon as possible

[Charudatta Bandgar]

Hello Ghassan. AbuSultanah ,

Can you please share the archived simulation file (.wbpz) as well as the calculation sheet for better understanding? I will get in touch with the fluid experts to understand your issue correctly and provide you with a solution. I have sent you an email with secure transfer link, where you can share your files.

Regards.

[ghassan.abusultanah]

Charudatta Bandgar  Any update on this? I sent the model couple of days ago. 

[Charudatta Bandgar]

Hello Ghassan. AbuSultanah ,

 

Sorry for the delayed response. Upon reviewing your calculations and simulations I have noticed some discrepancies, which could be my misunderstanding or incorrect assessment. Please feel free to address them, if necessary.

The calculation sheet mentions k-factor which is used to calculate the analytical pressure drop values for given velocities. I was not sure what this k-factor is, the formula used to calculate this k factor is    Where e is the porosity of the medium, this k-factor does not have any unit. It is then used to calculate pressure drop for a given velocity and uses a quadratic formula as   , which means that k is the unitless entity called inertial loss factor, which is used to calculate the inertial resistance C2.  Again the pressure calculated with the quadratic formulation is curve fitted with a trendline with power 2, and it gives zero as the linear S term, which would mean zero viscous losses. This seems to be incorrect for laminar flow.

This same k seems to be also divided by the thickness to calculate C1 (viscous resistance), which actually should be C2 (inertial resistance). 

Since it is said that the flow is laminar and you have considered C2 to be zero, the calculations are still done for C2 or inertial resistance. The calculations are required to be done for Viscous losses, and for which you will need to calculate the permeability factor (α).

The values calculated in the excel sheet and the ones used in the simulation, also do not match up. Unless the calculations and input values are correct the results will not be of any significance. Please refer to the Fluent documentation on porous media to understand which formulae and equations to use.

Another small suggestion would be to cross-check the unit conversion or use the same units in the calculation as well as simulation, to avoid unnecessary confusion.

 

Regards.

[ghassan.abusultanah]

Can I compounded multiple layers for Porous Media by adding the C and alpha values ? 

[Charudatta Bandgar]

Hello, Ghassan. AbuSultanah 

I don't think for multiple layers you can just add the C and alpha values numerically since the relations are complex in nature.

To simulate porous media with multiple layers, you will have to get the pressure drop vs velocity for those multiple layers and extract the equivalent C and alpha values by the usual method you can find in the related literature or AIM documentation.

Regards.