def LimiterG2forRSU(r):
    """Return the limiter for Roe-Sweby Upwind TVD limiter function.

    This limited is further used to calculate the flux limiter
    function given by Equation 6-137.
    Calculated using Equation 6-139 in CFD Vol. 1 by Hoffmann.
    """
    # Equation 6-139
    G = (r + abs(r))/(1.0 + r)

    return G