Nonlinear Dynamic Aalysis of Natural Ventilation in a Two-Zone Building: Part B—CFD Simulations

Abstract

Computational fluid dynamics (CFD) is a widely accepted design and analysis tool for building ventilation. This paper presents a simple method using commercial CFD software to obtain the solution multiplicity characteristics of laminar and turbulent indoor airflows. The method is known as the two-way continuation simulation, which has been developed for identifying multiple solutions in computational fluid dynamics. We consider airflows in a simple two-zone building with four openings, where one of the zones has a constant heat source, modeling the heat or pollutant generation and spread in buildings governed by natural stack forces. Using the new two-way continuation simulation method, we describe the flow variation and physical mechanisms at different heights in the two zones for different Rayleigh numbers. The results show that two steady solutions with the same boundary conditions and building geometry can be obtained step-by-step in the simulation process. Flow multiplicity can also be found as the height ratio of the two zones increases or decreases. As an important physical parameter, the Rayleigh number can also have some significant influences on the flow bifurcation or variation. Compared with conventional CFD simulation, the two-way continuation simulation method can effectively identify the possible existence of multiple solutions of indoor airflows and pollutant spread with different initial conditions. One shortcoming of the two-way method is that it cannot identify unstable solutions.

CFD and ventilation research

“…(2002). Although the existence of multiple solutions was not identified by CFD, CFD has provided a powerful tool to understand solution multiplicity phenomena in buildings, in addition to experimental studies (Heiselberg et al., 2004; Li et al., 2006; Yang et al., 2006).…”

Nonlinear Dynamic Analysis of Solution Multiplicity of Buoyancy Ventilation in Two Vertically Connected Open Cavities with Unequal Heights

“…Zheng et al investigated the nonlinear equations for ventilation flows in an enclosure with a single opening [34]. Yang et al carried out theoretical and computational nonlinear dynamic analysis on natural ventilation of two-zone buildings [35,36]. Van Schijndel carried out a numerical study on the chaotic behavior of airflow in a normally ventilated room [37].…”

A Four-Zone Model and Nonlinear Dynamic Analysis of Solution Multiplicity of Buoyancy Ventilation in Underground Building

“…For example, Durrani et al [28] researched the multiple solutions in a typical aboveground building with one zone and three openings by CFD simulations; through theoretical analysis, Chen and Li [29] researched the buoyancy ventilation of a single-zone building with three horizontal openings. e third kind research is about the solution multiplicity of two-zone buildings [30][31][32][33]. For example, Yang et al [30,31] analyzed in detail multiple steady states in a two-zone building by theoretical analyses and CFD simulations; Li et al [32] studied the buoyancy ventilation in a two-story building with two heat sources and three openings by establishing a mathematical model of nonlinear ordinary differential equation; Yang et al [33] analyzed the smoke exhaust spread of the three entrance tunnel in the fire scenarios and obtained six possible equilibrium states.…”

“…e third kind research is about the solution multiplicity of two-zone buildings [30][31][32][33]. For example, Yang et al [30,31] analyzed in detail multiple steady states in a two-zone building by theoretical analyses and CFD simulations; Li et al [32] studied the buoyancy ventilation in a two-story building with two heat sources and three openings by establishing a mathematical model of nonlinear ordinary differential equation; Yang et al [33] analyzed the smoke exhaust spread of the three entrance tunnel in the fire scenarios and obtained six possible equilibrium states.…”