Changes between Version 3 and Version 4 of doc/tec/usm

Timestamp:

Feb 25, 2019 12:14:52 PM (6 years ago)

Author:

rvtils

Comment:

--

doc/tec/usm

@@ -8 +8 @@
 The wall heat and green heat model consist of prognostic equations for the bare, window and soil temperature and the volumetric soil moisture which are solved for multiple layers. The models only take transport into account that is orthogonal to the urban surface layer orientation and no ice phase is considered. By default, the wall heat model and the green heat soil model consists of four layers each (see Fig. 1 below), in which the orthogonal heat and water transport inside the soil is modelled.
 
+The energy balance is calculated for each urban surface tile individually and the three radiation surface temperatures are combined together.
+The parametrisation of the sensible heat flux, latent heat flux and ground heat flux of the wall/ window/ soil is equivalent to the Land Surface Model (LSM).
+
+The physical properties of the urban surfaces and wall, window and green soil elements can be set using values from a building database where different types of buildings are defined. The insulation value of windows are there only characterized by the U-value and and the heat capacity and heat conductivity is evenly distributed (no real glas or gas layers are taken into account.
+
+The absorption of shortwave radiation inside the window layers is calculated using an logarithmic absorption function and the absorption coefficient is calculated using the overal window transmissivity value. The heat that is absorpted within each window layer is taken into account by the wall heat model.
+
+The green heat model calculates the transport of soil moisture but neglects the extraction of water from the respective soil layers.
+
+
+Boundary Conditions
+Neumann boundary conditions are used for the transport of heat at the upper boundary (surface). The values are given by the energy balance. At the bottom boundary either a fixed temperature of the inner wall and winow layers is set or the ground heat flux from the inner wall and window surface is used that is calculated by the indoor model (Dirichlet conditions).
+
+
 [[Image(urban_surfaces.png,600px, border=1)]]