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GasTranSim.jl Documentation

Calling the simulator

We shall illustrate the simplest call to invoke the simulator and then explain the various input arguments with reference to the simple case of a single pipe. The input files are contained in the directory examples/data/1-pipe-fast-transients/

The initialization function for the simulator has the definition initialize_simulator(data_folder::AbstractString;case_name::AbstractString="", case_types::Vector{Symbol}=Symbol[], kwargs...)

From Julia REPL, the simplest call is:

folder = "examples/data/1-pipe-fast-transients/"
ts = initialize_simulator(folder)
# equivalent to the call
ts = initialize_simulator(folder; eos = :ideal, case_name="", case_types=[:params, :network, :bc, :ic])

The minimal function call implicitly looks for all input files in the path folder. It assumes the equation of the state for the natural gas to be that given by the ideal gas equation, and that the case_name is an empty string. Thus it looks for input files params.json, network.json, bc.json, ic.json.

However, suppose one wanted to use the same network, parameters and initial conditions with different boundary conditions in say the file bc_new_case.json, and with the CNGA equation of state. Then one would use the call:

folder = "examples/data/1-pipe-fast-transients/"
ts = initialize_simulator(folder; eos = :simple_cnga, case_name="new_case", case_types=[:bc])

If the initial conditions are also different, and stored in ic_new_case.json, then the call would be modified to

folder = "examples/data/1-pipe-fast-transients/"
ts = initialize_simulator(folder; eos = :simple_cnga, case_name="new_case", case_types=[:bc, :ic])

Once the simulator is initialized, it is run by invoking

run_simulator!(ts)

Saving output

At the end of the simulation, there are two types of output we are interested in.

  1. A record of pressures/density at every node (junction) of the network, and the inflows/outflows into each pipe of the network at a frequency (Output dt) specified in the input file params.json.
  2. The state of the network at the end of the simulation, i.e., the values of the pressure/density and the mass flux along the pipes throughout the network are recorded following the spatial resolution (Output dx) set in the input file params.json. This information is stored in the same format as ic.json so that a new simulation can use the final state as the new initial condition and move forward in time.

Both of these tasks are accomplished as follows:

folder = "examples/data/1-pipe-fast-transients/"
ts = initialize_simulator(folder)
run_simulator!(ts)
write_output(ts; output_path = folder, 
	output_file = "output_time_history.json", final_state_file = "ic_restart.json")

Note that the flag for Save final state in params.json must be set to 1 in order to enable saving the output.

The file test/sim_restart.jl demonstrates that one run of the simulator from 0 to 24 hours is equivalent to two successive runs, one from 0 to 12 hours, and then the next one from 12 - 24 hours.