import numpy as np
from input.user_input import *


def Cd_model(fr, re, a_top):
    k_cd = 19.8
    k1 = 1.50 * 10 ** 7
    k2 = 0.86 * 10 ** (-7)
    a_top0 = np.pi / 4 * 1.383 * V_design ** (2/3)  # a_top0 for zero-pressure shape

    value = 0.2 * k_cd/fr * (k1/re + k2 * re) * a_top / (a_top0 ** (3/2))

    if value > 1.6:
        value = 1.6

    return value


c_d = 0.8  # 0.47


def drag(c_d, rho_air, A_proj, v):
    return 0.5 * c_d * rho_air * A_proj * v ** 2