Calculation for air flow through crack

[SakuraOno]

Hello,

I have a question regarding the way MacroFlo calculates the crack flow. On page 15 of the documentation "Calculation Methods", under heading 4.1, equation (7) shows that q=CL(ρref/ρ)^0.5 (∆P ^0.6).

I understand that this equation is based on an experimental-data-best-fit done by the AVIC. the only difference between this IES equation an the AVIC equation is that in the IES equation the (ρref/ρ)^0.5 term has been introduced. I was wondering why introduce this new term (dependence on air density)?

I was wondering if this is done by IES so that the air flow can then be dependent on the temperature as well (since simulation is by time step and the temperature obviously changes from time to time)? I suspect as such because by reading the AVIC document, I know that they assume an uniform air temperature of 20C, which has an air density of 1.21 (which is the value for ρref in the IES equation), therefore I just want to confirm if the introduction of the density dependence term is to account for the change in temperature. But if so, why square root it?

thanks very much for your explanation!

[SakuraOno]

Hello,

I have a question regarding the way MacroFlo calculates the crack flow. On page 15 of the documentation "Calculation Methods", under heading 4.1, equation (7) shows that q=CL(ρref/ρ)^0.5 (∆P ^0.6).

I understand that this equation is based on an experimental-data-best-fit done by the AVIC. the only difference between this IES equation an the AVIC equation is that in the IES equation the (ρref/ρ)^0.5 term has been introduced. I was wondering why introduce this new term (dependence on air density)?

I was wondering if this is done by IES so that the air flow can then be dependent on the temperature as well (since simulation is by time step and the temperature obviously changes from time to time)? I suspect as such because by reading the AVIC document, I know that they assume an uniform air temperature of 20C, which has an air density of 1.21 (which is the value for ρref in the IES equation), therefore I just want to confirm if the introduction of the density dependence term is to account for the change in temperature. But if so, why square root it?

thanks very much for your explanation!

Just wondering if anyone has an answer to this question?
Thanks very much!

[weishennba]

I have a further question on the equation calculating the flow rate of a crack. How to define the temperature difference between indoors and outdoors? May be a combination from wind pressure and buoyancy pressure? Can you provide particular equations for that?

Thanks!