porespy.filters.capillary_transform#

porespy.filters.capillary_transform(im: numpy.typing.NDArray, dt: numpy.typing.NDArray = None, sigma: float = 1.0, theta: float = 180, g: float = 0.0, rho_wp: float = 0.0, rho_nwp: float = 0.0, voxel_size: float = 1.0, spacing: float = None)#

Uses the Washburn equation to convert distance transform values to a capillary transform.

Parameters:

  • im (ndarray) – A boolean image describing the porous medium with True values indicating the phase of interest.

  • dt (ndarray, optional) – The distance transform of the void phase, in voxels. If not provided it will be calculated, so some time can be saved if a pre-computed array is already available.

  • sigma (scalar (default = 1.0)) – The surface tension of the fluid-fluid interface, in N/m when using SI units.

  • theta (scalar (default = 180)) – The contact angle of the fluid-fluid-solid system, in degrees, measured through the non-wetting phase. It must be >90.

  • g (scalar (default = 0)) – The gravitational acceleration acting on the fluids, in m/s^2 when using SI units. Gravity is assumed to act toward index 0 along axis 0. To have gravity act along a different axis use np.swapaxes(im, 0, ax) where ax is the desired axis, and swap the same axes of dt if it is supplied.

  • rho_nwp (scalar) – The density of the non-wetting fluid, in kg/m^3 when using SI units.

  • rho_wp (scalar) – The density of the wetting fluid, in kg/m^3 when using SI units.

  • voxel_size (scalar (default = 1.0)) – The physical distance between adjacent voxel centers, in m when using SI units.

  • spacing (scalar (default = None)) – If a 2D image is provided, this value is used to compute the second radii of curvature. Setting it to np.inf will make the calculation truly 2D since only one radii of curvature is considered. Setting it to None will force the calculation to be 3D. If im is 3D this argument is ignored. This should be in units of physical length, not voxels.

Returns:

pc – The capillary pressure including the gravity correction, in Pa when using SI units.

Return type:

ndarray

Notes

All physical properties should be in self-consistent units, and it is strongly recommended to use SI for everything.

The gravity correction is (rho_nwp - rho_wp) * g * h, where voxel centers along axis 0 have heights h[i] = i * voxel_size. The first voxel center is the zero-height reference, so the last center is at (im.shape[0] - 1) * voxel_size. A singleton axis has zero height.

Examples

Click here to view online example.

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