Introduction to uDALES post-processing with MATLAB¶
This tutorial describes how to read and process facet data of the LES code uDALES using MATLAB. This tutorial introduces the udbase post-processing class. There are separate tutorials for processing field files and facet files.
The udbase post-processing class reads in most important input parameters, and contains a number of methods to load field and facet data.
Field data:
- load_stat_xyt. This method load the 1D slab- and time-averaged statistics from the file
xytdump.expnr.nc. Several time-intervals may be present in the data. - load_stat_t. This method loads the 3D time-averaged statistics from the file
tdump.expnr.nc. Several time-intervals may be present in the data. - load_field. This method loads instantaneous 3D data from the file
fielddump.expnr.nc. Several output times may be present in the data. - load_slice. This method loads instantaneous 2D slices of instantaneous 3D data from the file
Xslicedump.expnr.nc. Several output times may be present in the data.
Facet data:
- calculate_frontal_properties. This method calculates the skylines, frontal areas and blockage ratios in the x- and y-direction.
- plot_fac_type. This method displays the type of surface for each facet.
- assign_prop_to_fac. This method assigns a property of the facet type to each of the facets, so it can be used for calculation and visualisation
- plot_fac. This method displays a surface variable on the mesh.
- load_fac_momentum. This method loads instantaneous momentum surface data from
fac.expnr.nc. The first index is the facet id and second index is time. - load_fac_eb. This method loads instantaneous surface energy balance data from
facEB.expnr.nc. The first index is the facet id and second index is time. - load_seb. This method loads all instantaneous surface energy balance terms. The first index is the facet id and second index is time.
- load_fac_temperature. This method loads instantaneous facet temperature data
facT.expnr.nc. The first index is the facet id, the second is the layer index and the third index is time. - area_average_seb. This method calculates the area-averaged surface energy balance from the facet surface energy balances obtained using
load_seb. - area_average_fac. This method performs area-averaging over (a selection of) the facets. The facet index is assumed to be the first index of the array.
- time_average. This method performs time-averaging on an array; where time is assumed to be the last index of the array.
- convert_fac_to_field. This method converts a facet variable to a density in a 3D field, so it can be used for post-processing (e.g. calculating distributed drag).
The live matlab file of this tutorial can be found in the repository in the folder /docs/tutorial_mlx.
Initialising udbase¶
The starting point of this tutorial is that you have run a simulation and have merged the output files. If the simulations were performed on a HPC system, we assume that you have copied the output directory to your own workstation. Some of the netCDF (*.nc) files may be very large and you may only want to copy these if you plan to analyse the data.
The uDALES postprocessing class is called udbase. Typically, you will create a post-processing script in the output directory on your workstation, but it is also possible to have the output directory located in another directory. This is particularly useful if you are comparing several different simulations at the same time. Here, we will show how to use data from simulation 065 (expnr=065)that is located in a different directory from the one you are working in.
Note that the uDALES/tools/matlab path must be added via the Set Path button in order to use the udbase class. Alternatively, it can be added using the addpath function inside the script (done here).
% preamble
clear variables
close all
% add the uDALES matlab path
addpath('../matlab')
% create an instance of the udbase class
expnr = 065;
expdir = '../experiments/065';
sim = udbase(expnr, expdir);
The constructor can have a number of input parameters:
help udbase.udbase
Class constructor.
udbase(expnr, dapath, load_preprocdata)
expnr: experiment number
dapath (optional): path to the experiment
Example:
obj = udbase(expnr, '/path/experiments/../100');
Documentation for udbase/udbase
The constructor of the udbase class reads in the following files:
namoptions.expnr. Contains the simulation input parameters.xxx.stl.Contains the urban geometry used for the simulation [optional].
Provided that load_preprocdata is not set to false, the constructor of the udbase class additionally reads the following files:
solid_(u,v,w,c).txt.Contains the indices of the (u,v,w,c)-volumes occupied by buildings.facets.inp. Contains information about the facet wall type and surface normal.factypes.inp. Contains information about the properties of the wall types.facetarea.inp. Contains information about the facet areas.fluid_boundary_(u,v,w,c).txt. Contains information about the fluid cells associated with facet sections.facet_sections_(u,v,w,c).txt. Information about facet section area, distance and flux point.
Accessing simulation properties¶
To view all simulation input parameters, simply type
sim
sim =
udbase with properties:
expnr: '065'
geom: [1x1 udgeom.udgeom]
xm: [64x1 double]
ym: [64x1 double]
zm: [64x1 double]
xt: [64x1 double]
yt: [64x1 double]
zt: [64x1 double]
dx: 1
dy: 1
dzm: [64x1 double]
dzt: [64x1 double]
Su: [64x64x64 logical]
Sv: [64x64x64 logical]
Sw: [64x64x64 logical]
Sc: [64x64x64 logical]
facs: [1x1 struct]
factypes: [1x1 struct]
facsec: [1x1 struct]
nbndpts_w: 5164
fieldvars: ''v0,th,qt,u0,w0''
ladaptive: 1
sinkbase: 32
ltdump: 0
trestart: 51000
igrw_damp: 0
stl_ground: 1
facT: 301
iwalltemp: 2
nfctsecs_v: 12010
z0h: 6.7000e-05
thl0: 301
lconstW: 1
uflowrate: 5
nbndpts_v: 5208
fraction: 0.5000
wwilt: 172
dtEB: 1
runtime: 10000
nfaclyrs: 5
ipoiss: 0
vflowrate: 0
xlen: 64
nprocy: 4
lvreman: 1
libm: 1
tsample: 1
randu: 0.0100
ps: 101300
I: 814
lBImin_c: 0
nsolpts_u: 3856
irandom: 43
GRLAI: 2.1000
lBImin_v: 0
lEB: 1
lxytdump: 1
ktot: 64
dtmax: 5
lBImin_u: 0
z0: 0.0100
wtsurf: 0
min_vf: 0.0100
dtfac: 10
lrandomize: 1
solarazimuth: 135
iadv_qt: 2
nsolpts_c: 3488
ltempeq: 1
diag_neighbs: 0
nsolpts_w: 7584
nfcts: 2658
ylen: 64
tfielddump: 11
skyLW: 395
lbuoyancy: 1
jtot: 64
wgrmax: 451
lperiodicEBcorr: 1
nnz: 909975
nfctsecs_c: 7940
nprocx: 8
Dsky: 107.2000
nbndpts_c: 5164
solarzenith: 45
lvfsparse: 1
lflat: 1
nbndpts_u: 5208
qt0: 0.0100
flrT: 298
lvoutflowr: 0
lwriteEBfiles: 1
nfctsecs_w: 2817
lfielddump: 0
luvolflowr: 1
stl_file: 'geom.065.stl'
zsize: 64
wsoil: 250
wfc: 314
nfctsecs_u: 11214
lBImin_w: 0
iadv_thl: 2
tstatsdump: 5
maxD: 64
bldT: 298
wqsurf: 0
itot: 64
lwritefac: 1
rsmin: 200
u0: 2
nsolpts_v: 3696
iwallmoist: 2
lmoist: 1
iexpnr: 65
For a complete list of parameters and their meaning, please consult the pre-processing documentation. Some commonly used parameters are
xlen,ylenandzsizethat represent the domain sizeitot,jtotandktotthat represent the total number of grid cells
To access a parameter directly, use the syntax object.prop. To access the domain length in x-direction, use
sim.xlen
ans = 64
The geometry stored in the STL file, if present, has been also loaded, which can be visualised using the method below. This method will produce an error if STL file does not exist or been loaded.
sim.geom.show();
