def __dowson_hamrock_parameters(r_eff, param_g, param_u, param_w):
    """

     Calculate the EHD-parameter for Dowson-Hamrock film thickness calculations.
     The name EHD-parameter is used within the tribology package to refer to
     what is calculated below; this parameter is not officially defined by
     Dowson-Hamrock.

    Parameters
    ----------
    r_eff: scalar
        The effective radius of the contact problem.
    param_g: scalar
        The elasticity parameter of the contact problem.
    param_u: scalar
        The velocity parameter of the contact problem.
    param_w: scalar
        The load parameter of the contact problem.

    Returns
    -------
    param_ehd: scalar
        The EHD parameter of the contact problem.

    """
    param_ehd = r_eff * param_g ** 0.53 * param_u ** 0.67 * param_w ** -0.067
    return param_ehd