NENZF1d Reference Manual
NENZF1D is a program for estimating flow conditions in reflected-shock tunnels, when the test gas reaches temperatures high enough for chemical reactions to occur and when nonequilibrium chemistry effects are expected to be important. The calculation proceeds in two parts. Assuming thermochemical-equilibrium, a state-to-state calculation is done for the shock-tunnel processing of the test gas until it reaches sonic conditions at the nozzle throat. Then a calculation with finite-rate chemical reactions is made of the supersonic flow of the gas through the nozzle expansion.
1. Getting started
The nenzf1d program is built upon the core gas model and flow modules
of our gas-dynamics tool kit.
General getting started notes can be found at
https://gdtk.uqcloud.net/docs/getting-started/prerequisites .
There, you will see how to get a copy of the source code,
a list of what other software you will need to build and install the tool kit,
and a collection of environment variables that need to be set.
To install the nenzf1d program, move to its source directory
and use the make utility.
cd dgd/src/nenzf1d make install
This will also install files associated with the gas models.
Note that you will need a compiled version of the NASA Lewis cea2 program
installed in a location that the gas models module can find it.
2. Getting command help
When run as an application, this program accepts a single command line argument that specifies an input file with the detailed calculation parameters.
To see what other command-line options are available, start the program as:
nenzf1d --help
3. Example shock-tunnel calculation
Let’s consider shot 10559 for the T4 shock tunnel. This particular run of the wind tunnel was part of Wilson Chan’s PhD studies and used air as the test gas, with the Mach 6 nozzle providing expansion of the air to test-flow conditions.
To start, you are going to need a set of consistent gas model files in your working directory. There is a guide (https://gdtk.uqcloud.net/pdfs/gas-user-guide.pdf) to the gas-model module that is worth reading but, for the moment, let’s set up a 5-species model of air by copying the gas-model files from the samples in the source code repository.
cp ${DGD_REPO}/src/gas/sample-data/cea-air5species-gas-model.lua .
cp ${DGD_REPO}/examples/kinetics/air-chemistry-1T/air-5sp-1T.inp .
cp ${DGD_REPO}/examples/kinetics/air-chemistry-1T/GuptaEtAl-air-reactions.lua .
prep-gas air-5sp-1T.inp air-5sp-1T.lua
prep-chem air-5sp-1T.lua GuptaEtAl-air-reactions.lua air-5sp-1T-reactions.lua
3.1. Input file
# Sample input file for nenzf1d is a YAML 1.1 file.
# t4m6-air.yaml
# Data for T4 shot 10559 obtained from Wilson Chan's PhD thesis, Table D.1, page 158.
# PJ 2020-10-17
#
title: "T4 shot 10559 with Mach 6 nozzle." # Any string will do.
species: ['N2', 'O2', 'N', 'O', 'NO'] # List
molef: {'N2': 0.79, 'O2': 0.21} # Map of nonzero values will suffice.
# Gas model and reactions files need to be consistent with the species above.
# Gas model 1 is usually a CEAGas model file.
# Gas model 2 is a thermally-perfect gas model for the finite-rate chemistry.
gas-model-1: cea-air5species-gas-model.lua
gas-model-2: air-5sp-1T.lua
reactions: air-5sp-1T-reactions.lua
# Observed parameter values for shock-tube operation.
T1: 300 # K
p1: 130.0e3 # Pa
Vs: 2434.0 # m/s
pe: 34.07e6 # Pa
ar: 127.0 # Mach 6 nozzle
# Define the expanding part of the nozzle as a schedule of diameters with position.
xi: [0.0, 0.150, 0.280, 0.468, 0.671, 0.984] # axial-distance metres
di: [1.0, 4.0, 6.232, 8.44, 9.92, 11.268] # diameter (may be normalized)
# Optionally, we can adjust the stepping parameters for the supersonic expansion.
# x_end: 1.0
# t_final: 1.0e-3
# t_inc: 1.0e-10
# t_inc_factor: 1.0001
# t_inc_max: 1.0e-7
3.2. Results
Run nenzf1d with the command:
nenzf1d t4m6-air.yaml
to get the result
NENZF1D: shock-tunnel with nonequilibrium nozzle flow. T4 shot 10559 with Mach 6 nozzle. Initial gas in shock tube (state 1). pressure 130 kPa density 1.5036 kg/m^3 temperature 300 K H1 0.00187216 MJ/kg Incident-shock process to state 2. V2 0.362529 km/s Vg 2.07147 km/s pressure 7711.1 kPa density 10.0951 kg/m^3 temperature 2648.54 K Reflected-shock process to state 5. Isentropic relaxation to state 5s. entropy 8483.2 J/kg/K H5s 5.4437 MJ/kg H5s-H1 5.44183 MJ/kg pressure 34070 kPa density 27.947 kg/m^3 temperature 4147.1 K Isentropic flow to throat to state 6 (Mach 1). V6 1155.62 km/s mflux6 20077.8 pressure 19158.3 kPa density 17.374 kg/m^3 temperature 3775.48 K Isentropic expansion to nozzle exit of given area (state 7). area_ratio 127 V7 3.15445 km/s pressure 10.7819 kPa density 0.050117 kg/m^3 temperature 746.49 K mflux7 20077.7 pitot7 479.342 kPa End of part A: shock-tube and frozen/eq nozzle analysis. Begin part B: supersonic expansion with finite-rate chemistry. Throat condition: velocity 1.1908 km/s sound-speed 1.18961 km/s (v-V6)/V6 0.0304407 pressure 19158.3 kPa density 17.3739 kg/m^3 temperature 3775.48 K massf[N2] 0.726242 massf[O2] 0.17141 massf[N] 2.27571e-05 massf[O] 0.014889 massf[NO] 0.0874362 Exit condition: x 0.98406 m area-ratio 126.968 velocity 3.10966 km/s Mach 6.04831 p_pitot 506.509 kPa pressure 10.1286 kPa density 0.0523794 kg/m^3 temperature 669.499 K massf[N2] 0.732318 massf[O2] 0.190771 massf[N] 5.02429e-17 massf[O] 0.00244285 massf[NO] 0.0744683 Expansion error-indicators: relerr-mass 0.000390353 relerr-H 8.22724e-06 End.
4. Setting up the optional Python interface
The core NENZF1D machinery can also be accessed from Python code using a custom-built interface. This requires building the core code into a dynamic library, and then installing it somewhere that your Python interpreter can find it.
To build the library, invoke the following commands.
cd dgd/src/nenzf1d make libnenzf1d.so make install
This will copy the libnenzf1d.so file into dgdinst/lib. You will then need
to add this directory to Python’s path list, by adding the following lines to
your .bashrc, if they are not there already.
export PYTHONPATH=${PYTHONPATH}:${DGD}/lib
export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:${DGD}/lib
Check out the python examples in dgd/examples/nenzf1d/ for further
information on the API.