Classical use
Basics
nsfds2 can be used from a terminal with:
nsfds2 solve|make|show|loop
solve : solves Navier-Stokes equation using default config file ~/.nsfds2/nsfds2.conf
make : makes movie or sound files from results obtained with solve subcommand
show : set of commands for simulations parameters and grid and results inspection
loop : Run simulations for a set of config files in a path
ploop : Run simulations for a set of config files in a path in parallel processes
See -h option for further help:
nsfds2 solve -h
nsfds2 make -h # 'movie' and 'sound' subcommands
nsfds2 show -h # 'parameters', 'grid', 'pgrid', 'frame', 'probes' subcommands
nsfds2 loop -h
nsfds2 ploop -h
The solve subcommand
The solve subcommand launch the solver. By default, the solver uses ~/.nsfds2/nsfds2.conf as configuration file. To target another configuration file, use the -c argument as follows:
nsfds2 solve -c my_confif_file.conf
It is possible to display timings with:
nsfds2 solve -t
or make the solver quiet with:
nsfds2 solver -q
To see other options:
nsfds2 solver -h
The make subcommand
The make subcommand can either generate movie (mp4 file), sound (wav file) from an hdf5 file or a config file template:
nsfds2 make sound
nsfds2 make movie
nsfds2 make template
Work with sounds
Sounds are generated from the probes (pressure) saved in an hdf5 file. If no probe has been set in the computation domain, no sound will be generated from nsfds2 make sound. If this command is called without any parameters, the default configuration file is used. It is also possible to call the command with a target configuration file:
nsfds2 make sound -c my_confif_file.conf
or with target data file:
nsfds2 make sound -d my_data_file.hdf5
Work with movies
Movies can be created from an hdf5 file if the save option has been selected. Then, the following variables are allowed as argument of the movie subcommand:
var |
variable |
|---|---|
p |
pressure |
rho |
density |
vx |
x component of the velocity |
vz |
z component of the velocity |
e |
energy |
vxz |
vorticity |
For instance, to create a movie with both components of velocity:
nsfds2 make movie vx vz
It is also possible to make movie from a target configuration file:
nsfds2 make movie e -c my_confif_file.conf
or from a data file:
nsfds2 make movie rho -d my_data_file.hdf5
The show subcommand
The show subcommand provides a set of commands to show simulation parameters, results, or grid configuration. The main show subcommands are:
- frame
Display an acoustic variable at a given iteration (works like movie)
- probes
Display pressure field(s) as a function of time at probe location(s)
- spectrogram
Display spectrogram(s) at probe location(s)
- pgrid
Display physical grid
- parameters
Display some simulation parameters
For instance, to display the density at iteration 100:
nsfds2 show frame rho -i 100
Config file
By default, nsfds2 create the config file ~/.nfds2/nsfds2.conf. This file contains simulation parameters that are used by the solver.
[configuration]
version = 0.13.0
timings = False # Display timing detail
quiet = False # Quiet mode
cpu = 1 # Number of cpu used by the solver
[simulation]
nt = 500 # Number of time iterations
ns = 10 # Save fields each ns iterations
cfl = 0.5 # Courant–Friedrichs–Lewy number
[thermophysic]
norm = True|False # Normalize p0, rho0, c0 and T0 (Override other values).
p0 = 101325.0 # Atmospheric pressure (Pa)
t0 = 20.0 # Ambiant temperature (°C)
gamma = 1.4 # Heat capacity ratio
prandtl = 0.7 # Prandtl number
[geometry]
mesh = regular|curvilinear|adaptative # Mesh type
file = None|path # Path to .py file (for geo/curvname)
geoname = helmholtz_double # Python function for geometry
curvname = curvz # Python function for curvilinear coordinates
only_pml = False # Adaptative only in PML
Nd = 23 # Adaptative over Nd points
Rx = 3. # Dilatation rate [adaptative mesh]
bc = PPPP # Boundary conditions. Must be a mix of AWP
nx = 256 # Number of grid points along x-axis
nz = 256 # Number of grid points along z-axis
ix0 = 0 # Origin of the grid
iz0 = 0 # Origin of the grid
dx = 1 # Spatial x-step
dz = 1 # Spatial z-step
[PML]
beta = 0.0 # Depends on pseudo mean flow profile
alpha = 4.0 # Order of the spatial repartition law
sigmax = 20|auto # Filter strength along x. Can be 'auto'
sigmaz = 20|auto # Filter strength along z. Can be 'auto'
npml = 15 # Number of points of the PML
[source]
type = None|pulse|harmonic|white|wav # Source type
ixs = 64 # Source x-location
izs = 128 # Source z-location
s0 = 1e6 # Sources strength [Pa]
b0 = 2 # Half spatial bandwidth
f0 = 60000 # Frequency [harmonic only] [Hz]
seed = None # Seed [white noise only]. Must be integer.
off = 100 # Stop source at iteration 100. nt by default.
wavfile = None|path # Path to wavfile (for wav only)
[flow]
type = None # Flow type [custom/vortex]
U0 = 5 # Flow velocity following x [m/s] [only for custom]
V0 = 5 # Flow velocity following z [m/s] [only for custom]
[eulerian fluxes]
stencil = 3|7|11 # Number of points of stencil
[filtering]
filter = True|False # Activate selective filter
stencil = 11 # Number of points of stencil used by filters
strength = 0.75 # Strength of the filter
strength_on_walls = 0.01 # Strength on the nearest point from a wall
[viscous fluxes]
viscosity = True|False # Activate viscosity
stencil = 7 # Number of points of stencil used for viscosity
[shock capture]
shock capture = True|False # Activate shock capture procedure
stencil = 7 # Number of points of stencil for capture
method = pressure|dilatation # Capture based on pressure or dilatation
[figures]
figures = True|False # Activate figures
probes = True|False # Show probes in maps
pml = True|False # Show PML in maps
bc_profiles = True # Show bc profiles
fps = 24 # Framerate for movies
[save]
resume = True|False # Resume older simulation
path = results/ # path to data file
filename = tmp # data filename
compression = None|lzf # Activate data compression
fields = True # Save fields
vorticity = False # Save vorticity
probes = [] # Probe locations. Must be list of lists
Customize geometry
To customize geometry, one can provide a set of custom obstacles to the Mesh constructor. To learn more about this, see fdgrid documentation.
Note on Wav sources
Important: When using wav source, pay attention to the spatial steps (dx, dz). To resolve frequencies until 20 kHz, dx and dz must be < 0.017 m.