home.md

+# PyPK
+PyPK is a collection of p-k methods for solving the flutter equation.
+
+## Install and run
+If you only want to use PyPK, you can install it using
+```bash
+python3 -m pip install . [--user]
+```
+and then run a case using
+```bash
+python3 path/to/case.py
+```
+If you need to develop in PyPK before using it, you do not need to install anything, and you can just run your case from the repo folder using
+```bash
+python3 run.py path/to/case.py
+```
+
+## Use
+PyPK is initialized through its API `init_pypk`. Examples can be found under the tests directory. A case file typically contains the following lines
+```python
+from pypk import init_pypk
+cfg = {...}
+solver = init_pypk(cfg)
+solver.set_matrices(m, k, q)
+solver.compute()
+solver.find_flutter()
+solver.save(case_name)
+solver.plot(case_name, show=True, format=fmt)
+```
+where `cfg` is a `dict` defining the configuration of the solution method, `m`, `k` and `q` are the mass, stiffness and aerodynamic force matrices provided as `numpy array`, and `case_name` and `fmt` are `str`.
+PyPK has also been interfaced with OpenMDAO for performing flutter-constrained optimization, see [OMFlut](https://gitlab.uliege.be/am-dept/omflut). Within that context, its builder must be imported using `from pypk.api_om import PypkBuilder`, then initialized with a configuration dictionary and provided to an OMFLut FlutterGroup as `FlutterGroup(..., flutter=PypkBuilder(cfg))`.
+
+The configuration dictionary contains the following entries
+```python
+'k_ref': numpy array, # reference reduced frequencies
+'l_ref': float, # reference length (usually half root chord)
+'mach': float, # freestream Mach number
+'n_modes': int, # number of modes
+'rho_ks': float, # aggregation parameter for KS
+'method': str, # method type ('pk' or 'nipk')
+'vrb': int # verbosity level
+'fluid': str, # fluid type ('unmatched' or 'matched_isa')
+# IF 'fluid' is 'unmatched'
+'rho_inf': float, # freesteam density
+'u_idx': numpy array, # velocity index range
+'mu': float, # mass ratio
+'f_ref': float, # frequency of first torsional mode
+# IF 'fluid' is 'mached_isa'
+'alt': numpy array, # altitudes range
+```
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