This model describes the onedirectional pressure driven air flow through an opening, using the equation
ṁ = k Δp^{m},
where ṁ is the mass flow rate in kg/s,
k is a flow coefficient,
Δp is the pressure difference in Pa,
and m is the flow exponent.
A similar model is also used in the CONTAM software (Dols and Walton, 2015).
Dols and Walton (2002) recommend to use for the flow exponent m=0.6 to m=0.7 if the flow exponent is not reported with the test results.
References
 ASHRAE, 1997. ASHRAE Fundamentals, American Society of Heating, Refrigeration and AirConditioning Engineers, 1997.
 Dols and Walton, 2002. W. Stuart Dols and George N. Walton, CONTAMW 2.0 User Manual, Multizone Airflow and Contaminant Transport Analysis Software, Building and Fire Research Laboratory, National Institute of Standards and Technology, Tech. Report NISTIR 6921, November, 2002. [1]
 W. S. Dols and B. J. Polidoro,2015. CONTAM User Guide and Program Documentation Version 3.2, National Institute of Standards and Technology, NIST TN 1887, Sep. 2015. doi: 10.6028/NIST.TN.1887.

February 2, 2022, by Michael Wetter:
Revised implementation.
This is for
IBPSA, #1436.

Apr 6, 2021, by Klaas De Jonge:
First Implementation. Model expecting direct input of mass flow powerlaw coefficients.
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