README.md

pybem

Blade Element Method implementation for propeller calculations.

Installation

To run it as a user, simply invoke pip:

pip install .

For developers

If you want to contribute to the library, or tweak it to your own needs, install it in developer mode, including the development libraries:

pip install -e . --requirement requirements-dev.txt

Quickstart

Running the code consists of easy and uncoupled steps:

1. Declare the airfoil sections with their corresponding geometrical definition.
2. Create a propeller by putting together the sections and the number of blades.
3. Create a solver by putting together the propeller and a advance ratio.
4. Solve the flow.
5. Compute the force and torque coefficients.

Here is an example with an airfoil defined by an analytical lift and drag polars.

from pybem.models import Propeller, Section, BaseAirfoil
from pybem.bem import BladeElementMethod

# Define known sections
sections = [
    Section(
        name="Hub",
        r=0.3,
        beta=60,
        chord=0.4,
        airfoil=BaseAirfoil(cl_coeff=1.0, cd_coeff=1e-2),
    ),
    Section(
        name="Middle",
        r=0.6,
        beta=45,
        chord=0.35,
        airfoil=BaseAirfoil(cl_coeff=0.85, cd_coeff=1e-3),
    ),
    Section(
        name="Tip",
        r=1.2,
        beta=30,
        chord=0.2,
        airfoil=BaseAirfoil(cl_coeff=0.5, cd_coeff=1e-3),
    ),
]

# Define propeller
B = 6
propeller = Propeller(B=B, sections=sections)

# Define flow conditions and BEM method
J = 0.2
bem = BladeElementMethod(J=J, propeller=propeller, tip_loss=False, hub_loss=False)

# Solve
bem.solve()

# Compute forces
CT, CQ = bem.integrate_forces()