Ergh behaves strangely for certain GSD

[rcriii42]

Happens at il = 5x10**-2.

Parameters:

Dp = 0.762  #Pipe diameter
    d = 0.2/1000.
    GSD = {0.15: d / 1.5,
           0.50: d,
           0.85: d * 1.5,
           }
    epsilon = DHLLDV_constants.steel_roughness
    nu = 1.0508e-6  # DHLLDV_constants.water_viscosity[20]
    rhos = 2.65
    rhol = 1.0248103  # DHLLDV_constants.water_density[20]
    Rsd = (rhos - rhol)/rhol
    Cv = 0.10

invoked with

graded_Cvt_Erhg_list = [DHLLDV_framework.Erhg_graded(GSD, vls, Dp, epsilon, nu, rhol, rhos, Cv, Cvt_eq_Cvs=True)
                            for vls in vls_list]
im_list = [graded_Cvt_Erhg_list[i]*Rsd*Cv+il_list[i] for i in range(num_points)]

[rcriii42]

Workaround is to re-specify the GSD with a floor. Maybe a problem in how GSDs are handled?