### 15.5.3. areaInt

The `areaInt` function integrates a variable over the specified 2D location. To perform the integration over the total face area, select the `None` option from the Axis drop-down menu. If a direction is selected, the result is an integration over the projected area of each face onto a plane normal to that direction. Each point on a location has an associated area that is stored as a vector and therefore has direction. By selecting a direction in the function calculator, you are using only a single component of the vector in the area-weighting function. Because these components can be positive or negative, depending on the direction of the normal on the location, it is possible for areas to cancel out. An example of this would be on a closed surface where the projected area will always be zero (the results returned will not in general be exactly zero because the variable values differ over the closed surface). On a flat surface, the normal vectors always point in the same direction and never cancel out.

    areaInt[_<Axis>[_<Coord Frame>] ](<Variable|Expression>)@<Location>

where:

- `<Axis>` is x, y, or z.

  Axis is optional; if not specified the integration is performed over the total face area. If axis is specified, then the integration is performed over the projected face area. A function description is available.

- `<Coord Frame>` is the coordinate frame.

- `<Variable|Expression>` is a variable or expression.

- `<Location>` is any 2D region (such as a boundary or interface). An error is raised if the location specified is not a 2D object.

`areaInt_y_Frame2(Pressure)@boundary1` calculates the pressure force acting in the Y direction of the coordinate frame `Frame2` on the locator `boundary1`. This differs from a calculation using the force function, which calculates the total force on a wall boundary (that is, viscous forces on the boundary are included).

#### 15.5.3.1. Tools > Command Editor Example

    >calculate areaInt, <Expression>, <Location>, [<Axis>]

Axis is optional. If it is not specified, the value held in the object will be used. To perform the integration over the total face area, the axis specification should be blank (that is, type a comma after the location name). A function description is available in areaInt.

#### 15.5.3.2. Tools > Function Calculator Examples

- This example integrates `Pressure` over `Plane 1`. The returned result is the total pressure force acting on `Plane 1`. The magnitude of each area vector is used and so the direction of the vectors is not considered.

  Function: `areaInt`, Location: `Plane 1`, Variable: `Pressure`, Direction: `None`

- This example integrates `Pressure` over the projected area of `Plane 1` onto a plane normal to the X axis. The result is the pressure force acting in the X direction on `Plane 1`. This differs slightly from using the force function to calculate the X-directional force on `Plane 1`. The force function includes forces due to the advection of momentum when calculating the force on an internal arbitrary plane or a non-wall boundary (inlets, and so on).

  Function: areaInt, Location: `Plane 1`, Variable: `Pressure`, Direction: `Global X`.

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