#!/usr/bin/env python
#
# pyLOM - Python Low Order Modeling.
#
# Global aerodynamic calculation routines.
#
# Last rev: 22/05/2025
import torch
from ..utils.errors import raiseError
[docs]
def global_coeff(
CoefPressure: torch.Tensor,
SRef: float,
MomentCenter: torch.Tensor,
cRef: float,
CoefSkinFriction: torch.Tensor = None,
alpha: torch.Tensor = 0,
coordinates: torch.Tensor = None,
normals: torch.Tensor = None,
components: set[str] = {"CL", "CD", "CM"},
) -> dict[str, torch.Tensor]:
r"""
Calculate selected aerodynamic coefficients (CL, CD, CM) from pressure and skin friction coefficients.
Args:
CoefPressure (torch.Tensor): Tensor of shape (n,) or (n,1) with the pressure coefficients of the surface.
SRef (float): Reference area.
MomentCenter (torch.Tensor): Tensor of shape (3,) with the moment center coordinates.
cRef (float): Reference chord length.
CoefSkinFriction (torch.Tensor, optional): Tensor of shape (n,3) with the skin friction coefficients of the surface (default: `None).
alpha (torch.Tensor): Angle of attack in deg.
coordinates (torch.Tensor): Tensor of shape (n,3) with the coordinates of the surface points.
normals (torch.Tensor): Tensor of shape (n,3) with the normal vectors of the surface.
components (set[str]): Set containing any combination of "CL", "CD", "CM" indicating what to compute.
Returns:
set[torch.Tensor]: A set of tensors containing the requested aerodynamic coefficients.
"""
if normals.ndimension() == 1 or normals.shape[1] == 1:
normals = normals.view(-1, 3)
if normals.shape[1] != 3:
raiseError(f"Normals must have shape (n,3).")
if coordinates.ndimension() == 1 or coordinates.shape[1] == 1:
coordinates = coordinates.view(-1, 3)
if coordinates.shape[1] != 3:
raiseError(f"Coordinates must have shape (n,3).")
alpha = alpha*torch.pi/180
r = coordinates - MomentCenter.view(1, 3)
results = {}
# Pressure contribution
ForcePressure = torch.zeros_like(coordinates)
if CoefPressure is not None:
if CoefPressure.ndimension() == 1 or CoefPressure.shape[1] == 1:
ForcePressure = -CoefPressure.view(-1, 1) * normals
else:
raiseError(f"CoefPressure must have shape (n,) or (n,1).")
# Friction contribution
ForceFriction = torch.zeros_like(coordinates)
if CoefSkinFriction is not None:
if CoefSkinFriction.ndimension() == 1:
CoefSkinFriction = CoefSkinFriction.view(-1, 3)
elif CoefSkinFriction.shape[1] != 3:
raiseError(f"CoefSkinFriction must have shape (n,3).")
Si = torch.norm(normals, dim=1).view(-1, 1)
ForceFriction = CoefSkinFriction * Si
if CoefPressure is None and CoefSkinFriction is None:
raiseError("At least one of CoefPressure or CoefSkinFriction must be provided.")
# Compute only requested components
if "CL" in components:
CLp = torch.sum(ForcePressure[:, 2] * torch.cos(alpha) - ForcePressure[:, 0] * torch.sin(alpha)) if CoefPressure is not None else 0
CLf = torch.sum(ForceFriction[:, 2] * torch.cos(alpha) - ForceFriction[:, 0] * torch.sin(alpha)) if CoefSkinFriction is not None else 0
results["CL"] = (CLp + CLf) / SRef
if "CD" in components:
CDp = torch.sum(ForcePressure[:, 2] * torch.sin(alpha) + ForcePressure[:, 0] * torch.cos(alpha)) if CoefPressure is not None else 0
CDf = torch.sum(ForceFriction[:, 2] * torch.sin(alpha) + ForceFriction[:, 0] * torch.cos(alpha)) if CoefSkinFriction is not None else 0
results["CD"] = (CDp + CDf) / SRef
if "CM" in components:
Mp = torch.sum(torch.linalg.cross(r, ForcePressure)[:, 1]) if CoefPressure is not None else 0
Mf = torch.sum(torch.linalg.cross(r, ForceFriction)[:, 1]) if CoefSkinFriction is not None else 0
results["CM"] = (Mp + Mf) / (SRef * cRef)
return tuple(results[key] for key in components)
[docs]
def jacobians_pressure(
SRef: float,
MomentCenter: torch.Tensor,
cRef: float,
alpha: torch.Tensor = 0,
coordinates: torch.Tensor = None,
normals: torch.Tensor = None,
components: set[str] = {"CL", "CD", "CM"},
) -> dict[str, torch.Tensor]:
r"""
Calculate the Jacobians of selected aerodynamic coefficients (CL, CD, CM)
Args:
SRef (float): Reference area.
MomentCenter (torch.Tensor): Tensor of shape (3,) with the moment center coordinates.
cRef (float): Reference chord length.
alpha (torch.Tensor): Angle of attack in deg.
coordinates (torch.Tensor): Tensor of shape (n,3) with the coordinates of the surface points.
normals (torch.Tensor): Tensor of shape (n,3) with the normal vectors of the surface.
components (set[str]): Set containing any combination of "CL", "CD", "CM" indicating what to compute.
Returns:
set[torch.Tensor]: A set of tensors containing the requested aerodynamic coefficient Jacobians.
"""
if normals.ndimension() == 1 or normals.shape[1] == 1:
normals = normals.view(-1, 3)
if normals.shape[1] != 3:
raiseError(f"Normals must have shape (n,3).")
if coordinates.ndimension() == 1 or coordinates.shape[1] == 1:
coordinates = coordinates.view(-1, 3)
if coordinates.shape[1] != 3:
raiseError(f"Coordinates must have shape (n,3).")
alpha = alpha*torch.pi/180
r = coordinates - MomentCenter.view(1, 3)
results = {}
# Compute only requested components
if "CL" in components:
results["CL"] = (1.0 / SRef) * (normals[:, 0] * torch.sin(alpha) - normals[:, 2] * torch.cos(alpha))
if "CD" in components:
results["CD"] = (1.0 / SRef) * (-normals[:, 0] * torch.cos(alpha) - normals[:, 2] * torch.sin(alpha))
if "CM" in components:
results["CM"] = (1.0 / (SRef * cRef)) * (r[:, 0] * normals[:, 2] - r[:, 2] * normals[:, 0])
return tuple(results[key] for key in components)
