# HydroGeoSphere/Saturated Flow

## Pressure head input

Causes all heads which are input to be treated as pressure heads instead of hydraulic heads.

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## Freshwater pressure head

Causes all heads which are input and output to be treated as freshwater pressure heads instead of hydraulic heads.

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## Fluid pressure

Causes all heads which are input and output to be treated as fluid pressures instead of hydraulic heads.

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## No fluid mass balance

This instruction suppresses the calculation of fluid mass balance information which is, by default, computed at each time step.

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## Flow time weighting

1. tw Time-weighting factor for the flow solution.

Assigns a new value for the time-weighting factor for the flow solution, which defaults to 1.0. Values must be greater than 0.0 and less than or equal to 1.0.

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## Flow solver maximum iterations

1. maxfit Maximum number of flow solver iterations.

Assigns a new value for the maximum number of flow solver iterations, which defaults to 2000.

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## Flow solver convergence criteria

1. restol Flow solver convergence criteria.

Assigns a new value for the flow solver convergence criteria, which defaults to 1 × 10−10.

Convergence is obtained when this criteria is less than the absolute maximum value of the residual (error) of the latest flow solution. For the matrix equation:

${\displaystyle [A]x=b}$

where ${\displaystyle [A]}$  is the coefficient matrix, ${\displaystyle x}$  the vector of unknowns and ${\displaystyle b}$  the vector of knowns, we can calculate the residual ${\displaystyle r}$ , given a solution for ${\displaystyle x}$  as:

${\displaystyle r=b-[A]x}$

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## Flow solver detail

1. isolv_info Flow solver detail level.

Assigns a new value for the flow solver detail level, which defaults to 0. This value controls the level of detail of solver performance information printed to the screen and listing file, and can have values of 0 (no information) or 1 (full information).

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