def m_coef(h_septum):
    """
    Calculates the specific coefficient for calculation the heigth ligth layer of liquid equation.
    Parameters
    ----------
    h_septum : float
        The heigth of drain septum, [m]
    Returns
    -------
    m_coef : float
        The specific coefficient for this equation [dimensionless]
    References
    ----------
    Дытнерский, страница 239, формула 6.39
    """
    return 0.05 - h_septum*4.6