Changes between Version 3 and Version 4 of palm4u

Timestamp:

Dec 7, 2017 9:49:33 AM (7 years ago)

Author:

maronga

Comment:

--

palm4u

@@ -14 +14 @@
  2. the obstacles are fixed (not moving).
 
-With revision -r2232, the topography implementation is completely revised. 
-Starting from this revision, overhanging structures as for example bridges, ceilings, or tunnels, are allowed, i.e. topography does not necessarily be surface-mounted. 
-If no overhanging structures are present, the 3-D obstacle dimension reduces to a 2.5-D topography format, which is conform to the Digital Elevation Model (DEM) format (DEMs of city morphologies have become increasingly available worldwide due to advances in remote sensing technologies).
+Topography is realized in 3-D, e.g., overhanging structures as for example bridges, ceilings, or tunnels, are allowed, i.e. topography does not necessarily be surface-mounted. If no overhanging structures are present, the 3-D obstacle dimension reduces to a 2.5-D topography format, which is conform to the Digital Elevation Model (DEM) format (DEMs of city morphologies have become increasingly available worldwide due to advances in remote sensing technologies).
 In case of overhanging structures, however, 3-D topography information is required to mask obstacles and their faces in PALM. 
 
-The model domain is then separated into three subdomains (see Fig. 3):
+The model domain is then separated into three subdomains:
 
  A. grid points in free fluid without adjacent surfaces, where the standard PALM code is executed,
@@ -27 +25 @@
  C. grid points within obstacles, where the standard PALM code is executed but multiplied by zero. 
 
-[[Image(mask_method.png,600px,border=1)]]
-
-Figure 4: Sketch of the topography implementation using the mask method (here for ''w''). The yellow line represent the region where the prognostic terms for scalars and the ''w''-component are masked, while the red line indicates the region where special surface-bounded code is masked.
-Additional surface-bounded code is executed at grid points in between the yellow and the red line (see [wiki:doc/tec/topography topography implementation]).
-
 Additional topography code is executed in grid volumes of subdomain B. The faces of the obstacles are always located where the
-respective surface-normal velocity components ''u'', ''v'', and ''w'' are defined (cf. Fig. 1 in Sect. [wiki:doc/tec/discret discretization]) so that the impermeability boundary condition can be implemented by setting the respective surface-normal velocity component to zero.
+respective surface-normal velocity components ''u'', ''v'', and ''w'' are defined so that the impermeability boundary condition can be implemented by setting the respective surface-normal velocity component to zero.
 
 In case of 5th-order advection scheme, the numerical stencil at grid points adjacent to obstacles would require data which is located within the obstacle. 
 In order to avoid this, the order of the advection scheme is successively degraded at respective grid volumes adjacent to obstacles, i.e., from the 5th-order to 3rd-order at the second grid point above/beside an obstacle and from 3rd-order to 1st-order at grid points directly adjacent to an obstacle.
 
-Surfaces in PALM can be aligned horizontally upward facing (e.g. bottom surface or rooftop), horizontally downward facing (e.g. undersurface of bridges), or vertically (facing north, east, south or west direction). 
-At horizontal surfaces, PALM allows to either specify the surface values (''θ, q,,v,,, s'') or to prescribe their respective surface fluxes. 
-The latter is the only option for vertically oriented surfaces. 
 Simulations with topography require the application of MOST between each surface and the first computational grid point outside of the topography. 
-For vertical and horizontal downward-facing surfaces, neutral stratification is assumed for MOST, even if MOST is strictly speaking derived only for upward-facing horizontal surfaces. 
-This is simply attributed to the lack of knowledge in the literature about the best practice in this matter. \\\\
-The topography implementation has been validated by [#letzel2008 Letzel et al. (2008)] and [#kanda2013 Kanda et al. (2013)]. 
-[#park2013 Park and Baik (2013)] have recently extended the vertical wall boundary conditions for non-neutral
-stratifications and validated their results against wind tunnel data. Up to now, however, these modifications are not included in PALM 4.0. Figure 4 shows exemplarily the development of turbulence structures induced by a densely built-up artificial island off the coast of Macau, China (see also animation in [#knoop2014 Knoop et al., 2014]). The approaching flow above the sea exhibits relatively weak turbulence due to the smooth water surface. Within the building areas, strong turbulence is generated by additional wind shear (due to the walls of isolated buildings) and due to a general increase in surface roughness.
+For vertical and horizontal downward-facing surfaces, neutral stratification is assumed for MOST, even if MOST is strictly speaking derived only for upward-facing horizontal surfaces. This is simply attributed to the lack of knowledge in the literature about the best practice in this matter. \\\\
 
-[[Image(05.png,600px,border=1)]]
-
-Figure 5: Snapshot of the absolute value of the 3-D rotation vector of the velocity field (red to white colors) for a simulation of the city of Macau, including a newly built-up artificial island (left). Buildings are displayed in blue. A neutrally-stratified flow was simulated with the mean flow direction from the upper-left to the bottom-right, i.e. coming from the open sea and flowing from the artificial island to the city of Macau. The figure shows only a subregion of the simulation domain that spanned a horizontal model domain of about ''6.1x2.0x1 km^3^'', and with an equidistant grid spacing of ''8''m}$. The copyright for the underlying satellite image is held by Cnes / Spot Image, Digitalglobe. For more details, see associated animation [#knoop2014 Knoop et al. (2014)].
+Missing:
+* Coupling to LSM and USM
+* Terrain height and topography
 
 The technical realization of the topography and treatment of surface-bounded grid cells will be outlined in Sect. [wiki:doc/tec/topography topography implementation].