HydroGeoSphere/Specified Mass Flux

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This is also known as a second-type, Neumann, or constant mass flux boundary condition. It is a distributed property so you should first choose the subset of faces for which you want to apply the condition.

If the node was assigned a specified concentration or third-type concentration by a previous instruction then it will not be modified by further specified mass flux instructions.

If the node was assigned a specified mass flux value by a previous instruction then mass fluxes assigned in by subsequent instructions will be cumulative. This is because mass fluxes are applied to faces, and any node common to two such faces requires a contribution from each face.

Specified mass flux

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  1. npanel Number of panels in the time-variable mass flux function. For each panel, enter the following:
(a) ton_val,toff_val,(bc_val(j),j=1,nspeciesmob) Time on [T], time off [T], and specified mass flux [M T−1] of each species.

Chosen nodes in the currently active media (see Section 5.8.1) are assigned a time-variable mass flux value. This is a passive injection of solute mass which has no effect on the flow solution. If a node was previously assigned a first or third-type concentration, it will remain in effect.

A panel is a point in time at which the specified mass flux is set to a new value. The first panel would normally start at time zero. The mass flux given for the last panel will be maintained until the end of the simulation. You can assign a static mass flux for the duration of the simulation by setting npanel to 1, ton_val to 0.0 and toff_val to a large number.

Note that if nspeciesmob is greater than 1, additional values of bc_val should be included.

Note that the mass flux values are per unit time and the total mass which will be injected for a given timestep can be calculated by multiplying the value given here by the timestep length and the number of chosen nodes.

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Interpolate mass flux

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This command causes time-varying mass fluxes to be interpolated between panel values. This results in a smoother application of the mass flux function.

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