cape.pycart.tri: Cart3D Triangulation Module

This module provides the utilities for interacting with Cart3D triangulations, including annotated triangulations (including .triq files). Triangulations can also be read from the UH3D format (which is similar to the Cart3D .tri format but with face names for component IDs).

Triangulations can be read from a variety of formats, which are tabulated below.

Extension

Description

.tri

Cart3D tri format, can be ASCII, Fortran unformatted (big- or little-endian), or C-style stream

.triq

Annotated Cart3D tri format, any format. This format contains a number of state variables at each point in addition to the geometry information

.uh3d

UH3D format, similar to .tri but names for faces

.surf

AFLR3 surface mesh; can include quads

.unv

IDEAS format; very strange

In addition to the main functions inherited from cape.tri.TriBase, the pyCart.tri.Triq class has a few methods that are particular to the state variables saved in Cart3D.

Cart3D also utilizes the GMP format to associate names with the faces of component ID numbers. This is an XML format (standard name for the file is Config.xml) that associates a name for each of the component IDs in a triangulation. In addition, groups of component IDs can be given a name by defining “Parent” components in the XML file. Reading a triangulation with such a configuration can be done with the following commands.

import cape.pycart.tri
tri = pyCart.tri.Tri("Components.i.tri", c="Config.xml")

Note that Cart3D’s interpretation of the XML file is very strict. There cannot be any component IDs mentioned in the XML file that are not present in the TRI file. In addition, there is no way for a component to have multiple parents. For example, it is not possible to have a group that contains fins 1 and 2 while another group contains fins 1 and 3.

The module consists of individual classes that are built off of a base triangulation class cape.tri.TriBase. Methods that are written for the TriBase class apply to all other classes as well.

See Also:
class cape.pycart.tri.Tri(fname=None, c=None, **kw)
class cape.pycart.tri.Triq(fname=None, n=1, nNode=None, Nodes=None, c=None, nTri=None, Tris=None, CompID=None, nq=None, q=None)
ApplyAngularVelocity(xcg, w, Lref=1.0, M=None)

Perturb surface pressures with a normalized rotation rate

This is based on a method from Stalnaker:

  • Stalnaker, J. F. “Rapid Computation of Dynamic Stability Derivatives.” 42nd AIAA Aerospace Sciences Meeting and Exhibit. 2004. AIAA Paper 2004-210. doi:10.2514/6.2004-210

Call:
>>> triq.ApplyAngularVelocity(xcg, w, Lref=1.0, M=None)
Inputs:
triq: pyCart.tri.Triq

Triangulation instance

xcg: np.ndarray | list

Center of gravity or point about which body rotates

w: np.ndarray | list

Angular velocity divided by Lref times freestream soundspeed

Lref: float

Reference length used for reduced angular velocity

M: float

Freestream Mach number for updating Cp

Versions:

  • 2016-01-23 @ddalle: First version

ApplyAngularVelocityLinear(xcg, w, Lref=1.0, M=None)

Perturb surface pressures with a normalized rotation rate

This is based on a method from Stalnaker:

  • Stalnaker, J. F. “Rapid Computation of Dynamic Stability Derivatives.” 42nd AIAA Aerospace Sciences Meeting and Exhibit. 2004. AIAA Paper 2004-210. doi:10.2514/6.2004-210

Call:
>>> triq.ApplyAngularVelocityLinear(xcg, w, Lref=1.0, M=None)
Inputs:
triq: pyCart.tri.Triq

Triangulation instance

xcg: np.ndarray | list

Center of gravity or point about which body rotates

w: np.ndarray | list

Angular velocity divided by Lref times freestream soundspeed

Lref: float

Reference length used for reduced angular velocity

M: float

Freestream Mach number for updating Cp

Versions:

  • 2016-01-23 @ddalle: First version