pc_curve#

pc_curve(im, sizes=None, pc=None, seq=None, sigma=0.072, theta=180, voxel_size=1)[source]#

Produces a Pc-Snwp curve given a map of meniscus radii or capillary pressures at which each voxel was invaded

Parameters:

  • im (ndarray) – The voxel image of the porous media with True values indicating the void space

  • sizes (ndarray, optional) – An image containing the sphere radii at which each voxel was invaded during an invasion experiment.

  • pc (ndarray, optional) – An image containing the capillary pressures at which each voxel was invaded during an invasion experiment.

  • seq (ndarray, optional) – An image containing invasion sequence values, such as that returned from the ibip function.

  • sigma (float, optional) – The surface tension of the fluid-fluid system of interest. This argument is ignored if pc are specified, otherwise it is used in the Washburn equation to convert sizes to capillary pc.

  • theta (float) – The contact angle measured through the invading phase in degrees. This argument is ignored if pc are specified, otherwise it is used in the Washburn equation to convert sizes to capillary pressures.

  • voxel_size (float) – The voxel resolution of the image. This argument is ignored if pc are specified, otherwise it is used in the Washburn equation to convert sizes to capillary pressures.

Returns:

pc_curve – A custom object with the following data added as named attributes:

Attribute

Description

pc

The capillary pressure, either as given in pc or computed from sizes (see Notes).

snwp

The fraction of void space filled by non-wetting phase at each pressure in pc

Return type:

Results object

Notes

If sizes is provided, then the Washburn equation is used to convert the radii to capillary pressures, using the given sigma and theta values, along with the voxel_size if the values are in voxel radii. For more control over how capillary pressure model, it can be computed by hand, for example:

$$ pc = frac{-2*0.072*np.cos(np.deg2rad(180))}{sizes cdot voxel_size} $$

then passed in as the pc argument.

Examples

Click here to view online example.