def eq_10_virtual_origin(D: float, Q_dot_kW: float):
    """Equation 10 in Section 8.3.1 PD 7974-1:2019 calculates virtual fire origin.

    :param D: in m, fire diameter.
    :param Q_dot_kW: in kW, fire heat release rate.
    :return z_0: in m, fire's virtual origin.
    """

    z_0 = -1.02 * D + 0.083 * Q_dot_kW ** (2 / 5)

    return z_0