SPARTADSMC软件包的公共开发项目httpsparta.sandia.gov___下载.zip

"Previous Section"_Section_commands.html - "SPARTA WWW Site"_sws - "SPARTA Documentation"_sd - "SPARTA Commands"_sc - "Next Section"_Section_example.html :c :link(sws,http://sparta.sandia.gov) :link(sd,Manual.html) :link(sc,Section_commands.html#comm) :line 6. How-to discussions :h3 The following sections describe how to perform common tasks using SPARTA, as well as provide some techinical details about how SPARTA works. 6.1 "2d simulations"_#howto_1 6.2 "Axisymmetric simulations"_#howto_2 6.3 "Running multiple simulations from one input script"_#howto_3 6.4 "Output from SPARTA (stats, dumps, computes, fixes, variables)"_#howto_4 6.5 "Visualizing SPARTA snapshots"_#howto_5 6.6 "Library interface to SPARTA"_#howto_6 6.7 "Coupling SPARTA to other codes"_#howto_7 6.8 "Details of grid geometry in SPARTA"_#howto_8 6.9 "Details of surfaces in SPARTA"_#howto_9 6.10 "Restarting a simulation"_#howto_10 6.11 "Using the ambipolar approximation"_#howto_11 6.12 "Using multiple vibrational energy levels"_#howto_12 6.13 "Surface elements: explicit, implicit, distributed"_#howto_13 6.14 "Implicit surface ablation"_#howto_14 6.15 "Transparent surface elements"_#howto_15 6.15 "Visualizing SPARTA output with ParaView"_#howto_16 :all(b) The example input scripts included in the SPARTA distribution and highlighted in "Section 5"_Section_example.html of the manual also show how to setup and run various kinds of simulations. :line :line 6.1 2d simulations :link(howto_1),h4 In SPARTA, as in other DSMC codes, a 2d simulation means that particles move only in the xy plane, but still have all 3 xyz components of velocity. Only the xy components of velocity are used to advect the particles, so that they stay in the xy plane, but all 3 components are used to compute collision parameters, temperatures, etc. Here are the steps to take in an input script to setup a 2d model. Use the "dimension"_dimension.html command to specify a 2d simulation. :ulb,l Make the simulation box periodic in z via the "boundary"_boundary.html command. This is the default. :l Using the "create box"_create_box.html command, set the z boundaries of the box to values that straddle the z = 0.0 plane. I.e. zlo < 0.0 and zhi > 0.0. Typical values are -0.5 and 0.5, but regardless of the actual values, SPARTA computes the "volume" of 2d grid cells as if their z-dimension length is 1.0, in whatever "units"_units.html are defined. This volume is used with the "global nrho"_global.html setting to calculate numbers of particles to create or insert. It is also used to compute collision frequencies. :l If surfaces are defined via the "read_surf"_read_surf.html command, use 2d objects defined by line segements. :l,ule Many of the example input scripts included in the SPARTA distribution are for 2d models. :line 6.2 Axisymmetric simulations :link(howto_2),h4 In SPARTA, an axi-symmetric model is a 2d model. An example input script is provided in the examples/axisymm directory. An axi-symmetric problem can be setup using the following commands: Set dimension = 2 via the "dimension"_dimension.html command. Set the y-dimension lower boundary to "a" via the "boundary"_boundary.html command. The y-dimension upper boundary can be anything except "a" or "p" for periodic. Use the "create_box"_create_box.html command to define a 2d simulation box with ylo = 0.0. :ul If desired, grid cell weighting can be enabled via the "global weight"_global.html command. The {volume} or {radial} setting can be used for axi-symmetric models. Grid cell weighting affects how many particles per grid cell are created when using the "create_particles"_create_particles.html and "fix emit"_fix_emit_face.html command variants. During a run, it also triggers particle cloning and destruction as particles move from grid cell to grid cell. This can be important for inducing every grid cell to contain roughly the same number of particles, even if cells are of varying volume, as they often are in axi-symmetric models. Note that the effective volume of an axi-symmetric grid cell is the volume its 2d area sweeps out when rotated around the y=0 axis of symmetry. :line 6.3 Running multiple simulations from one input script :link(howto_3),h4 This can be done in several ways. See the documentation for individual commands for more details on how these examples work. If "multiple simulations" means continue a previous simulation for more timesteps, then you simply use the "run"_run.html command multiple times. For example, this script read_grid data.grid create_particles 1000000 run 10000 run 10000 run 10000 run 10000 run 10000 :pre would run 5 successive simulations of the same system for a total of 50,000 timesteps. If you wish to run totally different simulations, one after the other, the "clear"_clear.html command can be used in between them to re-initialize SPARTA. For example, this script read_grid data.grid create_particles 1000000 run 10000 clear read_grid data.grid2 create_particles 500000 run 10000 :pre would run 2 independent simulations, one after the other. For large numbers of independent simulations, you can use "variables"_variable.html and the "next"_next.html and "jump"_jump.html commands to loop over the same input script multiple times with different settings. For example, this script, named in.flow variable d index run1 run2 run3 run4 run5 run6 run7 run8 shell cd $d read_grid data.grid create_particles 1000000 run 10000 shell cd .. clear next d jump in.flow :pre would run 8 simulations in different directories, using a data.grid file in each directory. The same concept could be used to run the same system at 8 different gas densities, using a density variable and storing the output in different log and dump files, for example variable a loop 8 variable rho index 1.0e18 4.0e18 1.0e19 4.0e19 1.0e20 4.0e20 1.0e21 4.0e21 log log.$a read data.grid global nrho $\{rho\} ... compute myGrid grid all all n temp dump 1 grid all 1000 dump.$a id c_myGrid run 100000 clear next rho next a jump in.flow :pre All of the above examples work whether you are running on 1 or multiple processors, but assumed you are running SPARTA on a single partition of processors. SPARTA can be run on multiple partitions via the "-partition" command-line switch as described in "Section 2.5"_Section_start.html#start_6 of the manual. In the last 2 examples, if SPARTA were run on 3 partitions, the same scripts could be used if the "index" and "loop" variables were replaced with {universe}-style variables, as described in the "variable"_variable.html command. Also, the "next rho" and "next a" commands would need to be replaced with a single "next a rho" command. With these modifications, the 8 simulations of each script would run on the 3 partitions one after the other until all were finished. Initially, 3 simulations would be started simultaneously, one on each partition. When one finished, that partition would then start the 4th simulation, and so forth, until all 8 were completed. :line 6.4 Output from SPARTA (stats, dumps, computes, fixes, variables) :link(howto_4),h4 There are four basic kinds of SPARTA output: "Statistical output"_stats_style.html, which is a list of quantities printed every few timesteps to the screen and logfile. :ulb,l "Dump files"_dump.html, which contain snapshots of particle, grid cell, or surface element quantities and are written at a specified frequency. :l Certain fixes can output user-specified quantities directly to files: "fix ave/time"_fix_ave_time.html for time averaging, and "fix print"_fix_print.html for single-line output of "variables"_variable.html. Fix print can also output to the screen. :l "Restart files"_restart.html. :l,ule A simulation prints one set of statistical output and (optionally) restart files. It can generate any number of dump files and fix output files, depending on what "dump"_dump.html and "fix"_fix.html commands you specify. As discussed below, SPARTA giv