def wind_friction_velocity(wind_speed, n, height = 10):
    """
    Return the friction velocity [m/s]
    source : ALOHA

    Parameters
    ----------
    wind_speed : Speed of the wind [m/s] at the height
    n : Valaue of the exponent for Pasquill stability classes
    height : Height of wind measure, the default is 10 [m]


    """
    return wind_speed * 0.03 * (10/height)**n