A two-zone model for natural cross-ventilation. (July 2015) - Carrilho da Graça, G.
Abstract: Cross-ventilation flows (CV) are characterized by significant inflow momentum conservation as fluid flows across an enclosed rectangular volume as a confined jet. When the inflow area is smaller than the volume cross-sectional area the CV flow has distinct jet and recirculation flow regions. The simplified model presented in this paper characterizes the CV flow as the result of a confined axisymmetric jet driving one or two recirculation regions, each of which is a lid-driven cavity flow. The model consists of calibrated analytical scaling laws that predict characteristic velocities in the jet and recirculation flow regions using as inputs the inflow velocity, and relevant geometry parameters. The proposed model can deal with impinging flow angle effects and multiple inflow opening configurations. Comparison between the model predictions and validated computational fluid dynamics (CFD) simulations show adequate agreement for simplified prediction of characteristic flow velocities in cross-ventilated spaces. Graphical abstract: Highlights: Simplified model for CV flow with recirculation regions (rooms with A in / A RM << 0.5). CV flow is a jet that drives the recirculation regions as lid-driven cavity flows. We propose scaling laws to predict indoor flow with up to 20% error. Indoor velocities are proportional to ( A in / A RM ) 1/2 and A in 1 2 / D . The model works for non-normal wind and rooms with multiple openings.