Simplified direct forcing approach for dynamic modeling of building natural ventilation.


W. Wu, J. M.* Han, and A. Malkawi. 6/15/2020. “Simplified direct forcing approach for dynamic modeling of building natural ventilation.” Building and Environment, 188, 107509.


Natural ventilation is a promising approach to provide passive cooling in highly energy efficient buildings. A
widely applied method to evaluate the performance of natural ventilation is computational fluid dynamics (CFD).
However, dynamic modeling of natural ventilation from 1 h to the next is very challenging because state-of-theart
CFD simulations treat windows as fixed wall boundary surfaces. The objective of this study is to propose a
direct forcing approach to implement dynamic window operations in CFD simulations. The direct forcing
approach marks a band of computational cells according to window positions, and adds an ad-hoc body force to
the momentum equations and turbulence production term to the kinetic energy equation. The direct forcing
approach shows a high level of performance when predicting volume flow rates through window apertures. The
relative deviation was found to vary between 2.2% and 14%, depending on the reference wind speeds. Direct
forcing also showed good performance when predicting the height of the neutral plane when the wind incident
angle was less than 135◦. The direct forcing approach can be applied to study the dynamic daily or weekly CO2
variations in naturally ventilated buildings with predefined control algorithms. Future work will consider the
influence of wall shear stresses and zero normal velocity to improve the accuracy of the direct forcing approach
as applied to wind incident angles larger than 135◦.
Last updated on 09/11/2021