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use_api

Last edited by Adrien Crovato

APIs

Users wanting to use SDPM for standard computations, or interface it with external software should use one of the available APIs or write their own. The following APIs are available:

  • Core
  • OMFlut

Note the different APIs automate the creation of the mesh, the problem and the solvers, and provide methods for performing specific tasks. These APIs are available under api and share a common base: core.

Core

The core API is the common base of all APIs. It simply consists in a init_sdpm method which will return all the C++ objects wrapped in python required to run SDPM. If a new API is created, it should initialize itself by calling this method.

SDPM is initialized by using a dictionary of parameters, and the type of scenario and task. The different parameters are listed hereunder:

cfg = {
  # Model (geometry or mesh)
  'File': str, # input Gmsh file
  'Pars': dict, # parameters for Gmsh file (optional)
  # Markers
  'Wing': str, # name of the marker defining the lifting body (wing)
  'Te': str, # name of the marker defining the trailing edge of the lifting body
  # Freestream
  'Mach': float, # Mach number (optional)
  'AoA': float, # angle of attack (optional)
  'AoS': float, # angle of side slip (optional)
  # Unsteady motion
  'Num_wake_div': int, # number of cells per chord length in the wake
  'Frequencies': array[float], # list of reduced frequencies
  'Modes': str, # input file containing the modes (optional)
  'Num_modes': int, # number of modes
  # Transonic correction
  'Transonic_pressure_grad': str, # input file containing the pressure derivative (optional)
  # Geometry
  'Symmetry': bool, # whether only half (symmetric) model is provided
  's_ref': float, # reference surface area
  'c_ref': float, # reference chord length
  'x_ref': float, # reference point for moment computation (x)
  'y_ref': float, # reference point for moment computation (y)
  'z_ref': float # reference point for moment computation (z)
}

Once the parameters have been defined, SDPM can simply be initialized by calling,

from sdpm.api.core import init_sdpm
_sdpm = init_sdpm(cfg)

where _sdpm is a dictionary containing the following objects (named after their key):

  • n_f is the number of reference reduced frequencies
  • n_m is the number of modes
  • msh is the mesh
  • wrt is the utility to write mesh/results on disk
  • pbl is the formulation of the problem
  • bdy is the body of interest
  • sol is the direct solver
  • grd is the gradient calculator

OMFlut

SDPM has been interfaced with OMFlut, which is built on top of OpenMDAO, in order to calculate flutter. SDPM must be initialized inside an OpenMDAO group using a builder which will latter be reused by OMFlut.

from omflut import FlutterGroup
from sdpm.api.om import SdpmBuilder
import openmdao.api as om 
class Flutter(om.Group):
  # ...
  sdpm = SdpmBuilder(cfg)
  self.add_subsystem('flutter', FlutterGroup(struct=..., xfer=..., aero=sdpm, flutter=...))