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Dispersion V3.23 Volume 2 Airviro User’s Reference Working with the Dispersion Module How to simulate the dispersion of pollutants Working with the Dispersion Module How to simulate the dispersion of pollutants Amendments Version Date changed Cause of change Signature 3.11 Ago2007 Upgrade GS 3.12 January2009 Upgrade GS 3.13 January2009 Upgrade GS 3.20 May 2010 Upgrade GS 3.21 Dec 2010 Upgrade GS 3.21 June 2012 Review GS 3.22 April 2013 Release GS 3.23 Jan 2014 Upgrade GS 3.23 January 2014 Review GS 3.23 June 2015 Review GS Contents 2.1 Introduction..............................................................................................................7 2.1.1 Why You Need to Use Dispersion Models.........................................................7 2.1.1.1 What’s the Use of Dispersion Simulations.....................................................7 2.1.1.2 How Can Airviro Help?......................................................................................7 2.1.2 Model Assumptions..............................................................................................8 2.1.3 Brief description of the available models..........................................................9 2.1.4 How does Dispersion Module client work?.....................................................18 2.1.5 Guidance for the beginner:................................................................................18 2.1.6 Overview of the Dispersion Module Main Window.........................................19 2.1.6.1 Changing Weather Conditions – Model settings.........................................19 2.1.6.2 Specifying Emissions.....................................................................................20 2.1.6.3 Submitting a Dispersion for Calculation.......................................................20 2.1.6.4 Viewing Existing Dispersion Calculations...................................................21 2.1.6.5 Finding Local Values.......................................................................................21 2.1.6.6 Using Receptor Points....................................................................................21 2.1.6.7 Map Functions.................................................................................................21 2.1.6.8 Sub menus on the left-hand side in the Dispersion main windows..........22 2.1.6.9. What is the grid resolution of the simulation?............................................27 2.2 The Gauss Model...................................................................................................33 2.2.1 Examples Based on the Case Weather Condition..........................................33 2.2.2 Ordering a Calculation.......................................................................................34 2.2.3 Examples Based on Emission for a Specific Hour.........................................40 2.2.4 Using Scenario Weather Conditions................................................................43 2.2.5 Using the Advanced Result Options................................................................47 2.3 The Street Canyon Model.....................................................................................51 2.3.1 Street Canyon Overview....................................................................................51 2.4 The Grid Model.......................................................................................................55 2.4.1 Looking at Dispersions for a Specific Time Period........................................55 2.4.2 Looking at Dispersions for a Season...............................................................58 2.5 The Heavy Gas Model...........................................................................................60 2.5.1 Simulation of a Continuous Liquid Leak..........................................................61 2.5.2 Simulation of a Tank Burst................................................................................63 2.6 Introduction to the Receptor Model.....................................................................65 2.6.1 Where is this pollution coming from?..............................................................65 2.6.2 For proper use of the Receptor module:..........................................................66 2.6.4. Source Location.................................................................................................70 2.6.6 Emission Estimation..........................................................................................73 2.7 Aermod Model........................................................................................................77 2.8OSPM Model............................................................................................................80 2.9 MATCH Model.........................................................................................................84 Appendix 2A: The Wind Model - Calculation of the Wind Fields............................87 2A.1 Principles of Wind Field Calculations...............................................................87 2A.1.1 Wind Model Equations....................................................................................88 2A.1.2 Initialisation......................................................................................................88 2A.1.3 Stability and Turbulence Estimation - Preprocessing of Meteorological Data...............................................................................................................................89 2A.1.4 Mesoscale Interpolation..................................................................................93 2A.1.5 Procedures for Solving the Wind Model Equations.....................................95 2A.1.6 Numerical Methods..........................................................................................95 2A.1.7 Reference Literature........................................................................................96 Appendix 2B: Results from Verification Studies......................................................97 Appendix 2C: The Gauss Dispersion Model...........................................................100 2C.1 Introduction.......................................................................................................100 2C.2 When to Use the Gauss Plume Model............................................................100 2C.2.1 Source Type Definitions................................................................................102 2C.3 Plume Rise Formulation...................................................................................102 2C.4 Building Downwash..........................................................................................107 2C.5 The Gaussian Plume Model.............................................................................109 Appendix 2D: The Eulerian Advection-Diffusion Grid Model...............................111 2D.1 Introduction.......................................................................................................111 2D.2 Formulation of the Grid Model........................................................................111 2D.2.1 Numerical Methods........................................................................................112 2D.2.2 The Numerical Grid, Coordinate Transformations.....................................114 2D.2.3 The Turbulent Exchange Coefficient...........................................................114 2D.2.4 The Three-Dimensional Wind Field..............................................................118 2D.2.5 Source Initialisation.......................................................................................118 2D.3 Particle Deposition...........................................................................................119 2D.3.1 Dry Deposition of Gases and Non-Gravitating Particles...........................119 2D.3.2 Wet Deposition...............................................................................................121 2D.3.3 Particle Settling..............................................................................................121 Appendix 2E: Street Canyon Model.........................................................................123 2E.1 Model Description.............................................................................................123 Appendix 2F: The Heavy Gas Model.......................................................................126 2F.1 Continuous Release or a Leakage From a” Small” Hole...............................127 2F.2 Instantaneous Release or a Tank Rupture - Emission Only from the Liquid Phase..........................................................................................................................130 2F.3 Substances and Coefficients...........................................................................130 2F.3.1 Comments.......................................................................................................131 Appendix 2G: Scenario Calculations......................................................................132 2G.1 General Principles............................................................................................132 2G.3 General Applications Using the Scenario Feature........................................134 Appendix 2H: A Method to Locate Dominating Sources.......................................135 Appendix 2I: A Method to Estimate Emissions from Dominating Sources.........138 2.I.1
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