This thesis is concerned with advancing the modelling of indoor air flow and internal surface convection within dynamic whole-building simulation. The path taken is the conflation of computational fluid dynamics (CFD) techniques with dynamic whole-building simulation, with an accurate treatment of the co-dependencies between these modelling domains. Two flow responsive modelling techniques were devised and implemented within the ESP-r simulation program to achieve the research objectives. The adaptive convection algorithm enhances ESP-r's thermal simulation domain by dynamically controlling the simulation of internal surface convection. Empirical methods were extracted from the literature and a new method for characterizing mixed flow convective regimes was created to provide the algorithm with a basis of 28 convection coefficient correlations. Collectively these methods can calculate convection coefficients for most flows of practical interest. Working with this suite of correlations, the algorithm assigns appropriate equations to each internal surface and adapts the selection in response to the room's evolving flow regime. The adaptive conflation controller manages all interactions between the thermal and CFD modelling domains. The controller incorporates the latest turbulence modelling advancements applicable for room air flow simulation and possesses a suite of handshaking and thermal boundary condition treatments. The job of this adaptive conflation controller is to monitor the evolving thermal and air flow conditions in the room and dynamically select an appropriate combination of modelling approaches for the prevailing conditions. The two control schemes implemented to demonstrate the controller make use of a double-pass modelling approach. Each time-step that the thermal domain handshakes with CFD, the adaptive conflation controller performs an investigative simulation to approximate the room's flow and temperature field. Using these estimates, the controller calculates dimensionless groupings to determine the nature of the flow (forced, buoyant, mixed, fully turbulent, weakly turbulent) adjacent to each internal surface. This information is used to select suitable boundary condition treatments for each surface. A second CFD simulation is then performed using the refined modelling approach to more accurately resolve the room's air flow and temperature distribution, and to predict surface convection. In order to protect the thermal domain, a two-stage screening process is used to assess (and where necessary reject) the CFD-predicted surface convection estimates. These adaptive modelling techniques advance the modelling of indoor air flow and internal surface convection within whole-building simulation.

Digitized by Kansas Correctional Industries

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The study of air and water flows induced by water level changes is important for a better understanding of water release in response to pumping in unconfined aquifers and give new insights into pumping test data analysis. To improve the unsaturated flow and air-water two-phase flow numerical modeling of unconfined aquifer pumping tests, an improved unsaturated hydraulic conductivity model and a new relative air permeability model were proposed. A synthesis of the literature on subsurface airflow induced by natural forcings was presented to provide a better understanding of the generated airflow and its importance in environmental and engineering applications. A literature review was carried out to study the naturally occurring subsurface airflow. Analytical studies were carried out to derive the improved unsaturated hydraulic conductivity model and the new relative air permeability model. Experimental studies were conducted to investigate the air and water flows induced by drainage and pumping and numerical simulations were carried out using TOUGH2 and TOUGH2-MP to interpret the experimental data. Numerical models for unconfined aquifer pumping test analysis were built with TOUGH2-MP to investigate the effect of heterogeneity on pumping test results. The study of relative permeability models found that the relative permeabilities predicted by the proposed models are in better agreement with experimental data than existing models. Experimental and numerical investigations on air and water flows induced by drainage and pumping found that significant negative air pressure can be generated in a two-layered system with a low-permeability upper layer. The negative air pressure increases very fast after the start of pumping or drainage, reaches a maximum, and then gradually recovers to atmospheric pressure. The generated negative air pressure can significantly reduce the drainage of water from the column and increase the drawdown. Numerical studies of the effects of local heterogeneity on unconfined aquifer pumping test results found that the drawdown in an unconfined aquifer with a low-permeability zone is significantly greater than that of the homogeneous aquifers but the impact of the low-permeability zone diminishes in the long-term production period. This study presents state of knowledge on naturally occurring subsurface airflow and its implications, proposes improved and new relative permeability models for unsaturated flow and multiphase flow modeling, and offers new insights into the effect of air on water release and unconfined aquifer pumping test data analysis. The present study not only has theoretical significance but also has engineering implications. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

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