# MODFLOW 6 Angles

Video Transcript

## Detailed Description

The USGS groundwater modeling program MODFLOW 6 uses three angles to help specify three components of hydraulic conductivity. This video provides a visual explanation of these three angles.

## Details

Image Dimensions: 800 x 600

Date Taken:

Length: 00:02:55

Location Taken: US

## Transcript

The letters "USGS" and the words "Science for a Changing World" appear in green and fade to black.

This video describes the three angles

used to orient the three components of hydraulic conductivity in the XT3D option of MODFLOW 6.

On the screen you can see an ellipsoid with its three axes representing the three components of hydraulic conductivity.

When all the three angles are zero,

as they are here, K11 represents the first component hydraulic conductivity aligned with the X axis;

K22 represents the second component hydraulic conductivity aligned with the Y axis; and

K33 represents the third component hydraulic conductivity aligned with the Z axis.

In this case, the relative sizes of the three components are 2 to 1 to 0.3.

ANGLE1 rotates the ellipsoid about its K33 axis (within the x - y plane).

A positive value represents counter-clockwise rotation when viewed from any point on the positive K33 axis.

I will set ANGLE1 to 20 degrees now and you can see that the ellipsoid has rotated around the Z axis.

After ANGLE1 is specified, ANGLE2 rotates the ellipsoid about its K22 axis (out of the x - y plane).

A positive value of ANGLE2 represents clockwise rotation

when viewed from any point on the positive K22 axis, looking toward the center of the ellipsoid.

I will set ANGLE2 to 20 degrees now and you can see that the ellipsoid has rotated around its K22 axis.

After ANGLE1 and ANGLE2 are specified,

ANGLE3 rotates the ellipsoid about its K11 axis.

A positive value of ANGLE3 represents a clockwise rotation

when viewed from any point on the positive K11 axis, looking toward the center of the ellipsoid.

I will set ANGLE3 to 20 degrees now and you can see that the ellipsoid has rotated around its K11 axis.

Now I will animate the sequence so you can see that that first ANGLE1,

then ANGLE2, and finally ANGLE3 are each changed to 20 degrees.

The letters "USGS" and the words "Science for a Changing World" appear in green.