CosineExpansionContraction

class hoomd.mpcd.geometry.CosineExpansionContraction(expansion_separation, contraction_separation, repeat_length, no_slip=True)

Bases: Geometry

Channel with sinusoidal expansion and contraction.

Parameters:

• expansion_separation (float) – Maximum distance between channel walls.

• contraction_separation (float) – Minimum distance between channel walls.

• repeat_length (float) – Repeat length (period) of cosine.

• no_slip (bool) – If True, surfaces have no-slip boundary condition. Otherwise, they have the slip boundary condition.

CosineExpansionContraction models a fluid confined in \(y\) between two walls described by a sinusoidal profile with equations

\[y(x) = \pm\left( \frac{H_{\rm e}-H_{\rm c}}{2} \left[1+\cos\left(\frac{2 \pi x}{L}\right)\right] + H_{\rm c} \right)\]

where \(2 H_{\rm e}\) is the expansion_separation, \(2 H_{\rm c}\) is the contraction_separation, and \(L\) is the repeat_length.

Example:

channel = hoomd.mpcd.geometry.CosineExpansionContraction(
    expansion_separation=6.0,
    contraction_separation=3.0,
    repeat_length=10.0,
)
stream = hoomd.mpcd.stream.BounceBack(period=1, geometry=channel)
simulation.operations.integrator.streaming_method = stream

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Members inherited from Geometry:

no_slip

Plates have a no-slip boundary condition when True. Read more...

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Members defined in CosineExpansionContraction:

contraction_separation

Distance between channel walls at the minimum contraction (read only).

Type:

float

expansion_separation

Distance between channel walls at the maximum expansion (read only).

Type:

float

repeat_length

Repeat length (period) of cosine. (read only).

Type:

float