test_liftingline.py

import numpy as np
from wingstructure.aero.liftingline import multhopp

def test_multhopp_schlichting():
    Λ = 6 # aspect ratio of wing
    
    b = 15 # m span width
    cs = np.array([b/Λ]*2) # depth of wing
    ys = np.array([0,b/2]) # section positions

    αs = np.array([1]*2) # angle of attack
    dcls = np.array([2*np.pi]*2)

    # reference result
    ηs_ref = np.array([0,0.3827,0.7071,0.9239,1])
    γs_ref = np.array([0.4320,0.4192,0.3710,0.2485,0])

    # coarse calculation
    M = 7

    res = multhopp(αs, cs, ys, dcls, M = M, mode='gamma')

    assert np.isclose(res[0][M//2:]/b*2, ηs_ref[:-1], atol=1e-4).all()
    assert np.isclose(res[1][M//2:], γs_ref[:-1], atol=1e-4).all()

def test_multhopp_dcls_nan():
    Λ = 6 # aspect ratio of wing
    
    b = 15 # m span width
    cs = np.array([b/Λ]*2) # depth of wing
    ys = np.array([0,b/2]) # section positions

    αs = np.array([1]*2) # angle of attack
    dcls = np.nan

    # reference result
    ηs_ref = np.array([0,0.3827,0.7071,0.9239,1])
    γs_ref = np.array([0.4320,0.4192,0.3710,0.2485,0])

    # coarse calculation
    M = 7

    res = multhopp(αs, cs, ys, dcls, M = M, mode='gamma')

    assert np.isclose(res[0][M//2:]/b*2, ηs_ref[:-1], atol=1e-4).all()
    assert np.isclose(res[1][M//2:], γs_ref[:-1], atol=1e-4).all()

def test_multhopp_coefficients():
    
    Λ = 6 # aspect ratio of wing
    
    b = 15 # m span width
    cs = [b/Λ]*2 # depth of wing
    ys = [0,b/2] # section positions

    αs = [np.radians(1)]*2 # angle of attack
    dcls = [2*np.pi]*2

    res = multhopp(αs, cs, ys, dcls, M = 91)

    A = b * cs[0]

    C_L = np.trapz(res.c_ls, res.ys)/b

    # ensure lift coefficient matches local lift coefficents
    assert np.isclose(C_L, res.C_L, rtol=1e-3)

def test_multhopp_coefficients2():
    
    Λ = 6 # aspect ratio of wing
    
    b = 15 # m span width
    cs = [b/Λ]*3 # depth of wing
    ys = [-b/2, 0, b/2] # section positions

    αs = [np.radians(1)]*3 # angle of attack
    dcls = [2*np.pi]*3

    res = multhopp(αs, cs, ys, dcls, M = 91)

    A = b * cs[0]

    C_L = np.trapz(res.c_ls, res.ys)/b

    # ensure lift coefficient matches local lift coefficents
    assert np.isclose(C_L, res.C_L, rtol=1e-3)