Smoke Dispersion from Stacks on Pitched-Roof Buildings: Model Calculations Using MISKAM in Comparison with Wind Tunnel Results Konstantinos E. Kakosimos 1 Marc J. Assael 1 Matthias Ketzel 2 Matthias Ketzel 2 Helge Rørdam Olesen 2 Ruwim Berkowicz 2 1 Aristotle University of Thessaloniki Chemical Engineering Department Laboratory of Thermophysical Properties & Environmental Processes 2 National Environmental Research Institute, Aarhus University Department of Atmospheric Environment 1 /16
[1/1] [1/1] � Scope of the current work outline outline � The methodology to reproduce the wind tunnel experiments in WinMiskam v6 & the employed case studies scope scope � The results for a representative case study and the additional sensitivity tests the additional sensitivity tests � Conclusions and discussion method method Part of this work was funded by the COST Office under the COST action results results ES0602 "Towards a European Network on Chemical Weather Forecasting and Information Systems (ENCWF)" discussion discussion 2 /16
[1/2] Study of the Phenomena Study of the Phenomena Study of the dispersion from Stacks: outline outline � Increasing oil prices domestic increased significantly the use of wood combustion � Residential wood combustion is a very significant source of scope scope particle pollution (Bari et al. , 2009). � In Denmark this source is responsible for to more than half of the direct PM 2.5 particle emission in the country (Glasius et of the direct PM particle emission in the country (Glasius et method method al. , 2008) results results question: Selection of the appropriate stack height/ position discussion discussion 3 /16
[2/2] Use of CFD models in the ABL Use of CFD models in the ABL � Pollution modelling for urban air quality applications outline outline has been based mainly on operational models of an integral nature. � Use of CFD models to address the same problems is increasing rapidly. scope scope � Among available CFD models the Reynolds averaged Navier–Stokes (RANS) equation models are increasingly used. increasingly used. method method � A number of studies supports the application of CFD tools � An equal number of studies raises significant issues results results question: are CFD tools appropriate for this type of studies? is MISKAM a reliable/ accurate tool for this type of discussion discussion studies? 4 /16
[1/ [1/5] tools & data tools & data � Wind tunnel experiments from: outline outline Jensen A.B., “Røgspredning i områder med lav bebyggelse”, Laboratoriet for varme - og klimateknik, DTH, 1984 (draft report). o Variable stack height scope scope o variable roof slope � Computational Programs: � Computational Programs: WinMiskam (Miskam v5 and v6), method method Ingenieurbüro Lohmeyer GmbH & Co. KG o k- ε turbulence model o Finite differences (structured Cartesian mesh) results results o Advection-diffusion equation for passive gases Ansys Inc. Fluent & CFX , o k- ε turbulence model o Finite Volume discussion discussion 5 /16
[2/5 2/5] geometry geometry Three different types of buildings outline outline stack height (H s ) varied from 0.0 m up to 8.0 m scope scope method method results results Παθητικός συλλέκτης LTPEP flat roof 30º roof 45º roof discussion discussion stack at the center stack at the side stack at the center 6 /16
[3/5] geometry geometry Computational mesh outline outline � Domain size length: 100 m, width: 90 m, height: 70 m scope scope � Coarse Resolution (mesh size) � Coarse Resolution (mesh size) building & near building: 0.5 m method method expansion ratio: <1.2 � Fine Resolution (mesh size) results results building & near building: 0.1 m expansion ratio: <1.2 discussion discussion 7 /16
[4/5] geometry geometry Representation of the building and the roof outline outline is limited by the mesh resolution floating source or physical stack scope scope 0.5m method method 3.5m 3m flat roof 30º roof 45º roof results results Roof extents sideways 0.5m discussion discussion 8 /16
[5/5] input data input data Wind tunnel measurements/data outline outline u * A = 0.19 m/s ; u * Wind profile: B = 0.28 m/s z o = 0.13 m scope scope Roughness: ground 0.10 m walls 0.01 m method method results results discussion discussion Comparison of profiles @the inlet Calculated profiles @ various x positions 9 /16
[1/ [1/5] graphs outline graphs outline outline outline Float source Physical stack Miskam v6 scope scope • physical stack • float source • 0 m < Hs < 8 m • 0 m < Hs < 8 m • each case normalized to max method method concentration of all Hs C = C norm results results C max|all Stack Height (Hs+5.8 m) Stack Height (Hs+5.8 m) Vertical profile of concentration 15 m downwind from the stack discussion discussion 10 /16
[2/5] 30deg;Miskam v6;Float 30deg;Miskam v6;Float vs vs Physical Physical Float source Physical stack outline outline scope scope method method results results discussion discussion each case normalized to max concentration of all Hs 11 /16
[3/5] 30deg; 30deg; Miskam Miskam v6 v6 vs vs CFX CFX Miskam v6 outline outline CFX scope scope method method results results discussion discussion each case normalized to max concentration of all Hs 12 /16
[4/5] Miskam v6 turbulence; 30deg roof Miskam v6 turbulence; 30deg roof Contour plots @ vertical along wind cut Contour plots @ vertical along wind cut outline outline Physical stack Physical stack Floating source Floating source wind wind scope scope Turbulent Kinetic Energy Turbulent Kinetic Energy method method Physical stack Physical stack Floating source Floating source wind wind results results discussion discussion Turbulent Eddy Dissipation Turbulent Eddy Dissipation 13 /16
[5/5] turbulence; 30deg roof turbulence; 30deg roof Stack Stack TKE TKE Base case: outline outline building without stack scope scope the “k- ε syndrome” (R. Berkowicz) ε ε Is more profound in Miskam & also influences K turb method method Horizontal cross-line @8.0 m K turb turb results results discussion discussion stack @ x:47.5 m - 48 m 14 /16
[1/2] [1/2] discussion discussion Question 1: outline outline Selection of the appropriate stack height/ position Relation of stack height and roof-slope scope scope on the dispersion of smoke from woodstoves � Wood firing guide – toolbox � Wood firing guide – toolbox � Chimney height: rules and recomendations method method � Sample collection of input � For more details please contact results results Helge Olesen, NERI, DK discussion discussion 15 /16
[2/2] /2] discussion discussion Question 2: Is MISKAM (either CFD) appropriate for this type of studies (i.e outline outline regulatory) � The inlet wind profile is adequately simulated and maintained along the domain scope scope � a physical stack represented in the model demonstrates an unexpected large influence on the results PROBABLY: o o the MISKAM (k – ε ) approach to calculate the diffusion the MISKAM (k – ε ) approach to calculate the diffusion coefficient, method method o the incorrect employment of the boundary conditions by MISKAM, (e.g. roughness of the vertical walls) o the lack of sufficient wind tunnel data to examine MISKAM performance on the simulation of turbulent kinetic energy, results results dissipation and dispersion � CFD tools are useful air pollution tools and reliable when are employed by experienced personnel and after validation discussion discussion ���������� 16 /16
[1/7] [1/7] concentration; 30deg roof concentration; 30deg roof outline outline scope scope method method Miskam v5, results results stack or w/o coarse mesh discussion discussion Each case normalized to max concentration st@3.0 17 /16
[6/7] /7] turbulence; 30deg roof turbulence; 30deg roof outline outline scope scope method method Turbulent Diffusivity Miskam v6 results results discussion discussion 18 /16
Recommend
More recommend
