DEPARTMENT OF FLUID DYNAMICS CFD SIMULATION OF FLOW OVER A MOCK URBAN SETTING USING OPENFOAM

Transcription

1 DEPARTMENT OF FLUID DYNAMICS Budapest University of Technology and Economics CFD SIMULATION OF FLOW OVER A MOCK URBAN SETTING USING OPENFOAM Anikó Rákai Gergely Kristóf, Ph. D. 5th OpenFOAM Workshop Gothenburg

2 Overview Geometry Boundary Conditions 3. Profile Comparison Validation Metrics 4. Future plans 2 5th OpenFOAM Workshop Rákai Anikó

3 1. Why urban? Thesis project: modelling of urban ventilation and dispersion 3 5th OpenFOAM Workshop

4 1. Why urban? Thesis project: modelling of urban ventilation and dispersion Why mock urban? COST 732 Framework: Quality Assurance and Improvement of Microscale Meteorological Models 1. Mock Urban Setting Test (MUST) 2. Joint Urban Test (Oklahoma) 4 th Rákai AnikóSetup Model 5 OpenFOAM Workshop Future Plans Anikó Rákai

5 1. Why urban? Thesis project: modelling of urban ventilation and dispersion Why mock urban? COST 732 Framework: Quality Assurance and Improvement of Microscale Meteorological Models 1. Mock Urban Setting Test (MUST) 2. Joint Urban Test (Oklahoma) Why OpenFOAM? Flexible, not used in COST th Rákai AnikóSetup Model 5 OpenFOAM Workshop Future Plans Anikó Rákai

6 2.1. Geometry and Bounday conditions 0 degree run: flow field Meshes: from Fluent 45 degree run: flow field dispersion 6 th Rákai AnikóSetup Model 5 OpenFOAM Workshop Future Plans Anikó Rákai

7 Settings Boundary conditions: INLET: from wind tunnel measurements U, k, ω, ε profiles OUTLET: zerogradient LEFT, RIGHT, TOP: symmetry WALLS: standard or rough wall function Solver: SimpleFoam for flow field turbulent scalartransportfoam for dispersion (fvm::ddt(c) + fvm::div(phi, C) - fvm::laplacian(nut, C) == source) Turbulence models: k-ε realizable k- ε k-ω SST 7 5th OpenFOAM Workshop

8 degree case Approach flow and 1st profile 8 th Rákai AnikóSetup Model 5 OpenFOAM Workshop Future Plans Anikó Rákai

9 degree case Street canyon velocity profiles at the end Vertical 9 5th OpenFOAM Workshop Horizontal

10 degree case Wake of the building velocity profiles at the end Vertical 10 5th OpenFOAM Workshop Horizontal

11 degree case Scatter plots of vertical velocity component Street canyon profiles All profiles [1] J.C.Chang, S.R. Hanna Air quality model performance evaluation, Meteorology and Atmospheric Physics 87, (2004) 11 5th OpenFOAM Workshop

12 degree case 12 5th OpenFOAM Workshop Absolute m/s Relative 25% U WT FL Hit rate OF_R_RKE 0.79 OF_S_RKE 0.73 OF_R_KE 0.78 OF_S_KE 0.72 MI 0.74

13 degree case Horizontal 13 5th OpenFOAM Workshop Vertical

14 degree case 14 5th OpenFOAM Workshop

15 degree case Hit rate U/Uref k-ε 0.72 Realizable k-ε 0.73 k-ω SST 0.74 With VDI treshold (absolute deviation = 0.05 m/s) W/Uref C* 0.42 German VDI guideline accepts hit rate th OpenFOAM Workshop

16 3.1. Conclusions Flow field: Similar results to other CFD codes Vertical component is problematic Acceptable according to VDI guideline Dispersion: Only first steps are in good order of magnitude OpenFOAM can be used for this kind of problem but dispersion needs further investigations 16 5th OpenFOAM Workshop

17 6. Dispersion problems Link between flow field and dispersion Refinement of transport equation (non isotropic) Urban problems: Geometry: mesh generation, elevation Planning: effect of buildings on pollutant dispersion Sensitivity: use of GIS data (population etc.) Figure from M. Balczó th 17 5 Rákai Anikó Model Setup OpenFOAM Workshop Future Plans Anikó Rákai

18 Thank you for your attention! 18