Compressible aerodynamics library.
Project description
compflow
The compflow library contains functions to convert back and forth between Mach number and other non-dimensional groups in compressible flows. By using a NumPy--Fortran interface, the code is vectorised and lightning-fast, yielding a speed-up of up to two orders of magnitude.
Full documentation is available online.
Features
- Evaluation of ten non-dimensional flow quantities as explicit functions of Mach number;
- Iteration with Newton's method to invert explicit relations and solve for Mach number;
- Creation and caching of lookup tables to speed up inversions;
- Fortran-accelerated, fully-vectorised in both directions.
Basic usage
compflow is available on the Python Package Index, so installation is as simple as,
python3 -m pip install compflow
Note: as the library uses Fortran subroutines behind the scenes, you will need a working Fortran compiler for the installation to complete successfully.
We can now start doing some calculations. First, an explicit evaluation of stagnation pressure ratio given a Mach number,
>>> import compflow
>>> ga = 1.4
>>> compflow.Po_P_from_Ma(0.3, ga)
1.0644302861529382
Second, an inversion of flow function where iterative solution for Mach number is required,
>>> compflow.Ma_from_mcpTo_APo(0.8, ga)
0.39659360325173604
The names and symbols of non-dimensional quantities are fairly self-explanatory, but a full list is given in the Nomenclature. All functions and the equations used for the calculations are documented in the API.
Numpy arrays are also accepted as inputs,
>>> import numpy
>>> Ma1 = numpy.array([0., 0.5, 1., 2.])
>>> compflow.To_T_from_Ma(Ma1, ga)
array([1. , 1.05, 1.2 , 1.8 ])
>>> Ma2 = numpy.array([[0.1, 0.2], [0.3, 0.4], [0.5, 0.6]])
>>> compflow.To_T_from_Ma(Ma2, ga)
array([[1.002, 1.008],
[1.018, 1.032],
[1.05 , 1.072]])
When solving for Mach number at a given normalised mass flow, it is assumed
that we are on the subsonic branch of the curve unless a flag is specified.
Where no solution is possible, i.e. if the flow would choke, NaN
is
returned,
>>> capacity = [0.6, 2.]
>>> compflow.Ma_from_mcpTo_APo(capacity, ga)
array([0.28442265, nan])
>>> compflow.Ma_from_mcpTo_APo(capacity, ga, sup=True)
array([2.27028708, nan])
TODO
- Make tolerance on Mach number for iterative inversions modifiable via a module-level attribute.
- Refactor and properly document the lookup table functionality.
- Add flag to solve for supersonic branch of A/A_crit.
- Add test for invalid values of Mach number.
- Add test for invalid values of inversion quantities.
- Add test for compatibility of output shape.
James Brind Feb 2021
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