Main LASER/F physical processes, algorithms, techniques

Solar radiation

• Accurate solar position for direct solar radiation computation

• Shadows and transparency effects

• Anisotropic diffuse solar radiation: all weather sky model for clear and covered sky

• Diffuse and specular reflection according to the surface coating properties

• Solar radiation exchange from interreflection between surface elements (progressive radiosity algorithm)

• Complete access to all solar radiation components

Infrared radiation

• Isotropic atmospheric infrared radiation

• Infrared emission from urban fabric according to the surface temperature

• Infrared radiation exchange by interemission from the urban fabric (progressive radiosity algorithm)

• Complete access to all infrared radiation components

Net radiation (radiation balance)

• Complete access to all components of the radiation balance at the surface of the objects (see above)

Energy balance

• Net radiation

• Exchanges of heat from the surface to the atmosphere, according to atmospheric stability

• Sensible heat flux from all surface elements

• Latent heat flux from natural elements (grass trees, bare soil...), water elements (rivers, lakes, pools) and wet artificial coatings (roads, roofs) after a precipitation

• Ground heat flux (heat storage) for multilayer walls, roofs and natural or artificial ground surfaces

• Access to soil, wall and ground temperature profiles

• Computation of the surface temperature according to the energy balance fluxes

• Interaction between the indoor atmosphere of the buildings and the urban canopy layer via the building envelope (natural ventilation from opened windows, or mechanical ventilation are taken into account)

Water balance

• Water supply at the surface from precipitation and condensation

• Management of a thin water reservoir for horizontal waterproof materials (roofs, roads)

• Runoff

• Infiltration in natural porous soils

• Percolation  between soil layers, (recharge - discharge)

• Water uptake from roots (grass)

• Complete soil water profiles 

• Evaporation or transpiration from wet artificial surfaces and from vegetation

Atmosphere

• Simplified urban canopy scheme for faster computation: no CFD

• IMPLICIT urban canopy layer

• Atmospheric stability according to temperature gradient

• Influence of building density and surface rugosity on wind speed

• The temporal evolution is prescribed with atmospheric variables measured (or simulated by mesosccale models) at regular time intervals above the mean roof level

• Atmospheric temperature, humidity, wind speed are forecast at mid level of the urban canopy

• Possible coupling with atmospheric weather models via the boundary conditions prescribed above the roof level

Managed objects

• Buildings with heating sources, air conditioner, multiple floors, windows, indoor radiation, natural ventilation, window opening management, greenroofs

• Natural ground with or without vegetation (grass, c3, c4, bare soil...)

• Artificial ground (roads, pavements, concrete, rocks...)

• Trees with real shapes and foliage (variable volume, LAI)

• Furniture (balconies, chimneys, truncs...) for more realistic simulation scenes

• Water: river, pools, lakes

Material database

• User specified material database: the user can define his own materials

• Realistic soil types according to sand and clay content

• Variable number of wall or soil layers and the user can specify the thickness of all layers

• User specified radiative properties of surface coatings: color, reflectivity, emissivity

• User specified thermophysical properties of all materials: conductivity, density, specific heat capacity, transparency to solar radiation

Devices

Multiple dummy sensors can be introduced everywhere in the simulation domain for validation purpose or to obtain results at specific places:

• 'Radiation sensors' to obtain the component of net radiation in the 6 spatial directions

• 'UTCI sensors' to obtain outdoor thermal comfort (UTCI comfort index) according to TMRT, wind speed, air temperature and humidity

• 'Laser sensors' can simulate scintillometers (they give all the components of energy balance integrated  along a path between a start and end point)

• 'Footprint sensors' to obtain the components of  energy balance integrated  into a rectangular 2D plane

• Direct access to all physical variables and results of all elements at several scales (meshes, faces, objects, atmosphere, scene)

Other

• LCZ are automatically defined for each atmospheric grid

• Thermal comfort index (UTCI, PET, SET... ) can be simulated at specific locations with special 'devices' or can be obtained with maps at the ground surface

• Scenarios can be classified with an original intercomparison procedure with respect to the remediation of heat wave and urban heat island (UHI)