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intro:modelconept [2015/07/27 12:11] – enviadmin | intro:modelconept [2017/05/07 11:12] – [Overview in a Nutshell] enviadmin | ||
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* 3D representation of vegetation including dynamic water balance modelling of the individual species | * 3D representation of vegetation including dynamic water balance modelling of the individual species | ||
* Dispersion of gases and particles. The model supports particles (including sedimentation and deposition at leafs and surfaces), inert gases and reactive gases of the NO-NO2-Ozone reaction cycle. | * Dispersion of gases and particles. The model supports particles (including sedimentation and deposition at leafs and surfaces), inert gases and reactive gases of the NO-NO2-Ozone reaction cycle. | ||
- | * Calculation of biometeorological indices Mean Radiant Temperature, | + | * Calculation of biometeorological indices |
===== Software Versions ===== | ===== Software Versions ===== | ||
- | Like always, the basic version of ENVI-met V4 is free and comes along as a complete model including the complete simulation core. In addition to the free version (**" | + | Like always, the **basic** version of ENVI-met V4 is free and comes along as a complete model including the complete simulation core for non-commercial applications. In addition to the free version (**" |
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The wind flow is updated at given time intervals. ENVI-met also supports a real-time flow calculation which means that the flow field is treated as a normal prognostic variable and calculated each step. Due to the very small time steps needed here, this way of calculation need very powerful computers. | The wind flow is updated at given time intervals. ENVI-met also supports a real-time flow calculation which means that the flow field is treated as a normal prognostic variable and calculated each step. Due to the very small time steps needed here, this way of calculation need very powerful computers. | ||
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- | **Air temperature and humidity**\\ | + | **Air temperature and humidity** |
Air temperature and specific humidity of the air are determined by the different sources and sinks of sensible heat and vapour inside the model domain. Based on the calculated three-dimensional wind field, advection and diffusion in the air is simulated. The ground surface and vegetation leafs act as sources or sinks for both temperature and humidity in the atmosphere model. Building walls and roofs mainly act as surfaces interchanging heat with the atmosphere, but can also act as humidity sources if facade or rooftop greening is applied. | Air temperature and specific humidity of the air are determined by the different sources and sinks of sensible heat and vapour inside the model domain. Based on the calculated three-dimensional wind field, advection and diffusion in the air is simulated. The ground surface and vegetation leafs act as sources or sinks for both temperature and humidity in the atmosphere model. Building walls and roofs mainly act as surfaces interchanging heat with the atmosphere, but can also act as humidity sources if facade or rooftop greening is applied. | ||
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- | ** Turbulence **\\ | + | ** Turbulence ** |
- | Turbulence is calculated using the E-epsilon 1.5order closure ([[kb: | + | Turbulence is calculated using the E-epsilon 1.5order closure ([[kb: |
For low wind situations, the 1st order mixing length model can be used instead of the E-epsilon model (which often fails in this situations). | For low wind situations, the 1st order mixing length model can be used instead of the E-epsilon model (which often fails in this situations). | ||
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- | **Radiative fluxes**\\ | + | **Radiative fluxes** |
ENVI-met contains newly developed analysis modules to model the fluxes of shortwave and longwave radiation inside of complex environments. The scheme takes into account shading by complex geometries, reflections by different surface and building materials and the effect of vegetation on all radiative fluxes. The Expert Version introduces the new IVS method, in which each urban element is considered using its actual state (sun reflection, thermal radiation) instead of averaged fluxes. | ENVI-met contains newly developed analysis modules to model the fluxes of shortwave and longwave radiation inside of complex environments. The scheme takes into account shading by complex geometries, reflections by different surface and building materials and the effect of vegetation on all radiative fluxes. The Expert Version introduces the new IVS method, in which each urban element is considered using its actual state (sun reflection, thermal radiation) instead of averaged fluxes. | ||
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- | ** Pollutant dispersion **\\ | + | ** Pollutant dispersion ** |
The pollutant dispersion model of ENVI-met allows the synchronous release, dispersion and deposition of up to 6 different pollutants including particles, passive gases and reactive gases. Sedimentation and deposition at surfaces and vegetation is taken into account as well as the photochemical reaction between NO, NO< | The pollutant dispersion model of ENVI-met allows the synchronous release, dispersion and deposition of up to 6 different pollutants including particles, passive gases and reactive gases. Sedimentation and deposition at surfaces and vegetation is taken into account as well as the photochemical reaction between NO, NO< | ||
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- | ** Surface and soil temperature **\\ | + | ** Surface and soil temperature ** |
The surface temperature and the distribution of soil temperature is calculated for natural soils and for artificial seal materials down to a depth of -4m. For each vertical grid layer a different soil or sealing material can be chosen in order to simulate different soils structures. The heat conductivity of natural soils is calculated with respect to the actual soil water content. | The surface temperature and the distribution of soil temperature is calculated for natural soils and for artificial seal materials down to a depth of -4m. For each vertical grid layer a different soil or sealing material can be chosen in order to simulate different soils structures. The heat conductivity of natural soils is calculated with respect to the actual soil water content. | ||
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- | ** Soil water content **\\ | + | ** Soil water content ** |
Simulating the water balance of the surface and the soil is a crucial aspect in urban microclimatology. While humid soils can act as cooling devices, dry soils are often hotter than asphalt. In addition, the cooling effect, and -on a longer time perspective- the vitality of vegetation depends on available soil water. ENVI-met dynamically solves the soil hydraulic state of the soil based on [[wp> | Simulating the water balance of the surface and the soil is a crucial aspect in urban microclimatology. While humid soils can act as cooling devices, dry soils are often hotter than asphalt. In addition, the cooling effect, and -on a longer time perspective- the vitality of vegetation depends on available soil water. ENVI-met dynamically solves the soil hydraulic state of the soil based on [[wp> | ||
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- | ** Vegetation water supply **\\ | + | ** Vegetation water supply ** |
Plants are living organisms and will only contribute in positive way to the local microclimate, | Plants are living organisms and will only contribute in positive way to the local microclimate, | ||
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- | ** Water bodies and pounds**\\ | + | ** Water bodies and pounds** |
Water bodies are represented as a special type of soil. The calculated processes inside the water include the transmission and absorption of shortwave radiation inside the water. | Water bodies are represented as a special type of soil. The calculated processes inside the water include the transmission and absorption of shortwave radiation inside the water. | ||
No second energy balance is used for the ground surface of the water pool, so that heating of shallow systems is lower than under real conditions where the main source of energy is the convection from the water ground surface rather than the absorption of radiation. | No second energy balance is used for the ground surface of the water pool, so that heating of shallow systems is lower than under real conditions where the main source of energy is the convection from the water ground surface rather than the absorption of radiation. | ||
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- | ** 3D Plant Geometry**\\ | + | ** 3D Plant Geometry** |
ENVI-met supports simple vertical plants such as grass or corn, but also allows complex 3D vegetation geometries like large trees. All plants are treated as individual species with an integrated water balance control and heat and water stress reaction concept. | ENVI-met supports simple vertical plants such as grass or corn, but also allows complex 3D vegetation geometries like large trees. All plants are treated as individual species with an integrated water balance control and heat and water stress reaction concept. | ||
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- | ** Foliage temperature**\\ | + | ** Foliage temperature** |
The temperature of the leafs is calculated by solving the energy balance of the leaf surface with respect to the actual meteorological and plant physiological conditions for each grid box of the plant canopy. The health status of the plant and the water supply by the soil regulate, beside other factors, the plants transpiration rate and thereby the leaf temperature. | The temperature of the leafs is calculated by solving the energy balance of the leaf surface with respect to the actual meteorological and plant physiological conditions for each grid box of the plant canopy. The health status of the plant and the water supply by the soil regulate, beside other factors, the plants transpiration rate and thereby the leaf temperature. | ||
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- | ** Exchange processes with the environment**\\ | + | ** Exchange processes with the environment** |
Vegetation interacts in various ways with the environment: | Vegetation interacts in various ways with the environment: | ||
A complex raytracing algorithm is used to analyse the plants impact of solar radiation (shadow casting) and on longwave radiation exchange (thermal shielding). | A complex raytracing algorithm is used to analyse the plants impact of solar radiation (shadow casting) and on longwave radiation exchange (thermal shielding). | ||
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- | **Vegetation health assessment/ TreePass/ Wind Risk Assessment**\\ | + | **Vegetation health assessment/ TreePass/ Wind Risk Assessment** |
The impact of vegetation on the microclimate is only one side of the story. To grow and live, plants also need adequate local climate conditions fitting to their individual demand profile. Too much or too little sun, to heavy wind loads on the trees or stagnating air: Many aspects of the microclimate can interfere with the plants requirements and hinder a healthy and robust growth. Using our TreePass technology, the local growing conditions and the plants profiles can be matched to provide an optimal placement. Our wind risk assessment simulates the tree mechanics in order to assess the risk of wind and storm damage depending on the crown structure and the tree location. (Consulting only). | The impact of vegetation on the microclimate is only one side of the story. To grow and live, plants also need adequate local climate conditions fitting to their individual demand profile. Too much or too little sun, to heavy wind loads on the trees or stagnating air: Many aspects of the microclimate can interfere with the plants requirements and hinder a healthy and robust growth. Using our TreePass technology, the local growing conditions and the plants profiles can be matched to provide an optimal placement. Our wind risk assessment simulates the tree mechanics in order to assess the risk of wind and storm damage depending on the crown structure and the tree location. (Consulting only). | ||
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- | ** Full 3D building geometry & Single walls**\\ | + | ** Full 3D building geometry & Single walls** |
Complex buildings and other structures can be constructed in full 3D with no limitations in complexity as far as the cubic base structure allows. This allows the simulation of semi-open spaces such as the soccer stadium shown in the icon and in this example. Moreover, ENVI-met Expert allows the usage of single thin walls that can be applied to any grid which can be used to represent spaces wich are enclosed by walls but do not behave like a building e.g. bus stop shelters, shading structures... | Complex buildings and other structures can be constructed in full 3D with no limitations in complexity as far as the cubic base structure allows. This allows the simulation of semi-open spaces such as the soccer stadium shown in the icon and in this example. Moreover, ENVI-met Expert allows the usage of single thin walls that can be applied to any grid which can be used to represent spaces wich are enclosed by walls but do not behave like a building e.g. bus stop shelters, shading structures... | ||
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- | ** Detailed building materials **\\ | + | ** Detailed building materials ** |
In Detailed Design Mode, ENVI-met allows to assign individual wall types to each wall and roof surface. The wall types can be composed out of 3 layers of different materials with individual physical properties such as solar radiation transmission, | In Detailed Design Mode, ENVI-met allows to assign individual wall types to each wall and roof surface. The wall types can be composed out of 3 layers of different materials with individual physical properties such as solar radiation transmission, | ||
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- | ** High resolution building physics**\\ | + | ** High resolution building physics** |
Each wall and roof segment in ENVI-met is represented by its own thermodynamical model consisting of 7 prognostic calculation nodes. The temperature of the outside node is updated continuously with respect to the meteorological variables at the facade and the thermal state of the buildings and other objects within the view range of the facade/roof element considered. The thermal state of the inner wall nodes is calculated from the physical properties assigned to the wall/roof based on [[wp> | Each wall and roof segment in ENVI-met is represented by its own thermodynamical model consisting of 7 prognostic calculation nodes. The temperature of the outside node is updated continuously with respect to the meteorological variables at the facade and the thermal state of the buildings and other objects within the view range of the facade/roof element considered. The thermal state of the inner wall nodes is calculated from the physical properties assigned to the wall/roof based on [[wp> | ||
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- | ** Building energy performance **\\ | + | ** Building energy performance ** |
ENVI-met dynamically calculates the development of the building indoor temperature as a result of the incoming and outgoing fluxes through the associated wall and roof segments. This building energy simulation is executed parallel to the outdoor microclimate simulation for each building in the model domain so that a constant feedback between the outdoor and indoor climate conditions and of the interactions between buildings is provided. The recent version allows an initial zoning model to define building sections and thermal zones. | ENVI-met dynamically calculates the development of the building indoor temperature as a result of the incoming and outgoing fluxes through the associated wall and roof segments. This building energy simulation is executed parallel to the outdoor microclimate simulation for each building in the model domain so that a constant feedback between the outdoor and indoor climate conditions and of the interactions between buildings is provided. The recent version allows an initial zoning model to define building sections and thermal zones. | ||
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- | ** Green Wall and Roof Systems**\\ | + | ** Green Wall and Roof Systems** |
ENVI-met Expert allows a detailed simulation of the energy and vapour exchange processes take place at green walls and green roof tops. The //Green Wall System// (GWS) integrates seamlessly into the dynamic calculation of the building energy performance and the facade/ wall temperature and supports a wide range of different systems from simple climbing plants up to living wall systems. | ENVI-met Expert allows a detailed simulation of the energy and vapour exchange processes take place at green walls and green roof tops. The //Green Wall System// (GWS) integrates seamlessly into the dynamic calculation of the building energy performance and the facade/ wall temperature and supports a wide range of different systems from simple climbing plants up to living wall systems. | ||
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- | ** Numerical discretisation scheme**\\ | + | ** Numerical discretisation scheme** |
ENVI-met uses an orthogonal [[wp> | ENVI-met uses an orthogonal [[wp> | ||
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- | ** Numerical methods**\\ | + | ** Numerical methods** |
ENVI-met uses the [[wp> | ENVI-met uses the [[wp> | ||
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- | ** Programming language **\\ | + | ** Programming language ** |
20 years ago, the choice of the programming language was a holy war. In these days, most models have been coded in FORTRAN, some of them in C. Today, the program languages are pretty much the same and their capabilities mainly depend on the libraries they load. ENVI-met is coded in Object Pascal, for WINDOWS using DELPHI. There is also a complete version in C++, but it showed no benefits so we returned to Object Pascal to minimize language confusions. Switching the core code from one language to another is about 3 days of work, which is less the work you have once a new FORTRAN compiler was released... So, for now we stick with Object Pascal until we are convinced to obtain benefits from changing. | 20 years ago, the choice of the programming language was a holy war. In these days, most models have been coded in FORTRAN, some of them in C. Today, the program languages are pretty much the same and their capabilities mainly depend on the libraries they load. ENVI-met is coded in Object Pascal, for WINDOWS using DELPHI. There is also a complete version in C++, but it showed no benefits so we returned to Object Pascal to minimize language confusions. Switching the core code from one language to another is about 3 days of work, which is less the work you have once a new FORTRAN compiler was released... So, for now we stick with Object Pascal until we are convinced to obtain benefits from changing. | ||
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