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SIMULATION OF TREE STEM INJURY, AIR FLOW AND HEAT DISPERSION IN FORESTS FOR PREDICTION OF FIRE EFFECTS

Chatziefstratiou, Efthalia
http://rave.ohiolink.edu/etdc/view?acc_num=osu1420644169

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Environmental Science.
This work presents two computational tools, Firestem2D and the fire module of Regional Atmospheric Modelling System (RAMS)-based Forest Large Eddy Simulation (RAFLES), which will help to make predictions of fire effects on trees and the atmosphere. FireStem2D is a software tool for predicting tree stem heating and injury in forest fires. It is a physically-based, two-dimensional model of stem thermodynamics that results from heating at the bark surface. It builds on an earlier one-dimensional model (FireStem) and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by resolving stem moisture loss, temperatures through the stem, degree of bark charring, and necrotic depth around the stem. The results of numerical parameterization and model evaluation experiments for FireStem2D that simulate laboratory stem-heating experiments of 52 tree sections from 25 trees are presented. A set of virtual sensitivity analysis experiments were also conducted to test the effects of unevenness of heating around the stem and with above ground height using data from two studies: a low-intensity surface fire and a more intense crown fire. The model allows for improved understanding and prediction of the effects of wildland fire on injury and mortality of trees of different species and sizes. Further, a study of the effects of particular properties of a high-resolution canopy resolving large eddy simulation (RAFLES) was conducted. RAFLES was later used to simulate the dispersion of heat and smoke inside and above forest canopies during low-intensity prescribed surface fires. RAFLES is the only large eddy simulation model that can resolve the effects of the volume of the trees in the canopy. All other models neglect the volume effects and only allow the flow to interact with the forest through a prescribed drag term. As a preliminary study for the heat dispersion simulations, the effects of resolving the tree volumes on air flow inside and around semi porous barriers, such as forests and cities were evaluated. The effects of the numerical representation of volume restriction, independent of the effects of the leaf drag were explicitly tested by comparing drag-only simulations, where neither volume nor aperture restrictions to the flow were prescribed, restriction-only simulations, where no drag was prescribed, and control simulations, where both drag and volume plus aperture restrictions were included. Finally, RAFLES was used to investigate how different canopy structures interact with augmented surface heat flux, simulating a low-intensity surface fire and how these interactions influence turbulence and heat exchange between canopy and atmosphere. A simplified, low-intensity fire event was simulated by directly prescribing heat flux to the bottom three grid layers of the simulation, below the canopy top. The effect of canopy structure on heat accumulation in the canopy and heat dispersion in and above canopy was tested. Furthermore, for each canopy structure, homogeneous and heterogeneous fire patterns were prescribed to contrast the effect of heterogeneity of the fire pattern with that of the canopy structure.
Gil Bohrer, Prof. (Advisor)
137 p.
Civil Engineering; Environmental Engineering; Environmental Science; Fluid Dynamics
heat transfer, atmospheric modeling, fire, turbulence, heat flux, air flow, fire effects, tree stem injury, smoke dispersion, large eddy simulations, computational fluid dynamics

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Citations

  • Chatziefstratiou, E. (2015). SIMULATION OF TREE STEM INJURY, AIR FLOW AND HEAT DISPERSION IN FORESTS FOR PREDICTION OF FIRE EFFECTS [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1420644169

    APA Style (7th edition)

  • Chatziefstratiou, Efthalia. SIMULATION OF TREE STEM INJURY, AIR FLOW AND HEAT DISPERSION IN FORESTS FOR PREDICTION OF FIRE EFFECTS. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1420644169.

    MLA Style (8th edition)

  • Chatziefstratiou, Efthalia. "SIMULATION OF TREE STEM INJURY, AIR FLOW AND HEAT DISPERSION IN FORESTS FOR PREDICTION OF FIRE EFFECTS." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1420644169

    Chicago Manual of Style (17th edition)

osu1420644169
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© 2015, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.