Internal API
The internal API is meant for users wanting to run a standard computational procedure on a classic lifting configuration. The procedures that are currently implemented can be found under api/internal:
- a polar analysis, to compute the aerodynamic coefficients for various angles of attack,
- a trim analysis, to find the angle of attack to produce a desired lift coefficient. Sample cases making use of the internal API can be found under cases.
1. Defining the parameters
In practise, all the classes implementing a computational procedure inherit from Config, which setups the solver. The first step thus consists in instantiating the desired class and passing it the parameters as a python dictionary. The different parameters are listed hereunder.
Common parameters (used in Config class):
p = {}
# I/O
p['Dim'] = int # dimension of the problem (2 or 3)
p['Format'] = str # output format ('gmsh' or 'vtk')
p['File'] = str # path to the geometry/mesh file
p['Pars'] = dict # keys/values of parameters or options to be passed to gmsh (can be empty)
# Groups...
p['Fluid'] = str # bame of mesh group containing the fluid
p['Farfield'] = list of str # names of mesh groups containing the farfield boundaries (downstream boundary should be last element)
# ... only for 2D
p['Wing'] = str # name of mesh group containing the airfoil boundary
p['Wake'] = str # name of mesh group containing the wake
p['Te'] = str # name of mesh group containing the trailing edge
# ... only for 3D
p['Wings'] = list of str # names of mesh groups containing the lifting surface boundary
p['Wakes'] = list of str # names of mesh groups containing the wake
p['WakeTips'] = list of str # names of mesh groups containing the edge of the wakes
p['TeTips'] = list of str # names of mesh groups containing the edge of the wakes and the trailing edges
# Freestream and reference values
p['M_inf'] = float # freestream Mach number
p['S_ref'] = float # reference surface length (= c_ref for 2D)
p['c_ref'] = float # reference chord length
p['x_ref'] = float # x-coordinate of reference point for moment computation
p['y_ref'] = float # y-coordinate of reference point for moment computation
p['z_ref'] = float # z-coordinate of reference point for moment computation
# Linear solver...
p['LSolver'] = str # linear solver type (Pardiso, GMRES, MUMPS or SparseLU)
# ... only for GMRES
p['G_fill'] = int # fill-in factor for GMRES ILU preconditioner
p['G_tol'] = float # tolerance for GMRES solver
p['G_restart'] = int # number of restart for GMRES solver
# Nonlinear solver...
p['NSolver'] = str # nonlinear solver type (Picard or Newton)
p['Rel_tol'] = float # relative tolerance on solver residual
p['Abs_tol'] = float # absolute tolerance on solver residual
p['Max_it'] = int # solver maximum number of iterations
# ... only for Picard
p['Relaxation'] = float # relaxation parameter (preffered value: 0.7)
# ... only for Newton
p['LS_tol'] = float # tolerance on line search residual (preffered value: 1e-6)
p['Max_it_LS'] = int # line search maximum number of iterations (preffered value: 10)
p['AV_thrsh'] = float # residual threshold below which the artificial viscosity is decreased (preffered value: 1e-2)
# Various optional parameters
p['Slice'] = list of float # y-coordinates of cutting planes to extract slices on the geometry
p['TagId'] = int # id of physical group to be sliced (id can be obtained through gmsh)
p['Symmetry'] = str # name of the mesh group containing the symmetry boundary
p['AoS'] = float # angle of sideslip [degrees]Additional parameters specific to Polar class:
p['AoA_begin'] = float # first value of the angle of attack [degrees]
p['AoA_end'] = float # last value of the angle of attack [degrees]
p['AoA_step'] = float # step in the angle of attack [degrees]Additional parameters specific to Trim class:
p['CL'] = float # target lift coefficient
p['AoA'] = float # guess (first) angle of attack
p['dCL'] = float # guess (first) slope of CL w.r.t AoA [1/rad]2. Using the solver
After the parameters have been defined, the solver can be set up automatically by instantiating the object as,
import dart.api.internal.polar as pol
polar = pol.Polar(p)
# or
import dart.api.internal.trim as trm
trim = trm.Trim(p)The script can then be run by calling,
polar.run()
# or
trim.run()Finally, the results can be displayed using,
polar.disp()
# or
trim.disp()