Note: This page has been translated by MathWorks. Please click here

To view all translated materals including this page, select Japan from the country navigator on the bottom of this page.

To view all translated materals including this page, select Japan from the country navigator on the bottom of this page.

Calculate wind shear conditions

Environment/Wind

The Wind Shear Model block adds wind shear to the aerospace model. This implementation is based on the mathematical representation in the Military Specification MIL-F-8785C [1]. The magnitude of the wind shear is given by the following equation for the mean wind profile as a function of altitude and the measured wind speed at 20 feet (6 m) above the ground.

$${u}_{w}={W}_{20}\frac{\mathrm{ln}\left(\frac{h}{{z}_{0}}\right)}{\mathrm{ln}\left(\frac{20}{{z}_{0}}\right)},\text{}3fth1000ft$$

where * u_{w}* is the mean
wind speed,

The resultant mean wind speed in the flat Earth axis frame is changed to body-fixed axis coordinates by multiplying by the direction cosine matrix (DCM) input to the block. The block output is the mean wind speed in the body-fixed axis.

**Units**Define the units of wind shear.

Units Wind Altitude `Metric (MKS)`

Meters/second Meters `English (Velocity in ft/s)`

Feet/second Feet `English (Velocity in kts)`

Knots Feet **Flight phase**Select flight phase:

`Category C`

—`Terminal Flight Phases`

`Other`

**Wind speed at 6 m (20 feet) altitude (m/s, f/s, or knots)**The measured wind speed at an altitude of 20 feet (6 m) above the ground.

**Wind direction at 6 m (20 feet) altitude (degrees clockwise from north)**The direction of the wind at an altitude of 20 feet (6 m), measured in degrees clockwise from the direction of the Earth

-axis (north). The wind direction is defined as the direction from which the wind is coming.*x*

Input | Dimension Type | Description |
---|---|---|

First | Contains the altitude in units selected. | |

Second | 3-by-3 direction cosine matrix |

Output | Dimension Type | Description |
---|---|---|

First | 3-by-1 vector | Contains the mean wind speed in the body axes frame, in the selected units. |

See ```
Wind
Shear Model
```

in `aeroblk_HL20`

for
an example of this block.

U.S. Military Specification MIL-F-8785C, 5 November 1980.

Was this topic helpful?