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Miskam basics

Miskam basics. Perspective view of an urban district Source : Marton Balczó. MISKAM – Mikroskaliges Strömung-und Ausbreitungsmodell ( M i c ro scale flow and dispersion model ) Developer : Dr. J. Eichhorn , Universit ät Mainz ( 1989 ) Custom software :

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Miskam basics

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  1. Miskambasics Perspectiveview of an urbandistrict Source: Marton Balczó MISKAM – MikroskaligesStrömung-undAusbreitungsmodell(Microscale flow and dispersionmodel) Developer: Dr. J. Eichhorn,Universität Mainz (1989) Customsoftware: Urban ventilation & pollutantdispersion MeetVDI Richtlinie 3783 Blatt9german standard Validatednumericalmodel Modelsetup: RANS- equation: withk-ϵturbulencemodelclosure Dispersionequation : passivescalartransport One-waycoupling Numericalgrid Onlyhexahedral, structuredmesh max. 5 millionsgridcells Rectangularblock-structures buildings, vegetation , bridges/passages Boundaries Inlet: 1D logarithmicvelocityprofile Upperboundary: Airflow parallel tothesurface Lateralboundaries: No normalvelocitycomponent

  2. Miskambasics Gasexhauststack of István Benkő elementaryschoolin Újpest Pollutantemission modelling Pointsource (mg/s) Areasource (mg/m2/s) Line source (mg/m/s) Differentiatedby x y directions Miskam benchmark Advantages: Easymeshgeneration Low CPU demand Validatedforneutralatmosphericstratification Dispersion modelling of non-reactivepollutants Disadvantages: Inaccuratecalculationonvertical mixing No heattransportmodeling No chemicalreactions No parallel simulation Terrain modelling restrictedtoflatland No validatedmodelfor stabil stratification No velocityprofile No boundarylayerresolution Urban ventillation of city centre Millenium Modelling urban pollution dispersion by using MISKAM, 2004 Source: Márton Balczó,

  3. Guidelinefornumericalmodeling Extent of computationaldomain Alltheairflowstructuresdevelopingaroundthebuildings(e.g. wakes, vortices etc.) „5L rule” Dmin= Lb+4wm L =size of thesmalleredge of the building w = magnitude of windvelocity The height of thedomain>3H of thetallest building Numericalgridqualityrequirements The appliednumericalschemestoworkaccurately: Smoothness: max. 1.2 growthrate Aspect ratio: max. 1:2 Skewness: -> max. 0.85 forhexaelements (Miskamautomaticallyfulfilsthisrequirements)

  4. Miskamtutorial Start the program:  Start menu / WinMiskam.exe Step 1: Meshgeneration Step 2: Fit thelayoutmap Loadmap: http://www.ara.bme.hu/oktatas/tantargy/NEPTUN/ BMEGEATMW08/2012-2013-I Makecoordinatemapping Pixels-> layout Coordinates -> grid

  5. Miskamtutorial Step 3. : Digitizethebuildings Digitize/edit building Outlinethebuildingsbypolygons Mapping of buildingsonthegrid Stop theeditprocess! Step 4.: Allocatethe line source Digitize/editroad net CPM10 = 1 mg/m/s (C24h limit = 50 μg/m3) Mapping of road net onthegrid Stop theeditprocess!

  6. Miskamtutorial Saveyourmeshascampus.inp!

  7. Miskamtutorial Step 5.: Windfieldsetup Runningthe flow simulation Allocatethetargetdirectories RunMiskaminsinglemode Step 6. : Concentrationfieldsetup Runningthedispersionsimulation Step 7. : Post-processing Windvelocity and concentrationdata(read*.zwu \*.zwkfiles) Horizontal and verticalslices Pespectiveview of thedomain( readthe*.inpfile)

  8. Thankyouforyourattention!

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