Wind Shear Model

Calculate wind shear conditions

• 

Libraries:
Aerospace Blockset / Environment / Wind

Description

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].

Ports

Input

h — Altitude

scalar

Altitude, specified as a scalar in specified units.

Data Types: double

DCM — Direction cosine matrix

3-by-3 matrix

Direction cosine matrix, specified as a 3-by-3 matrix representing the flat Earth coordinates to body-fixed axis coordinates.

Data Types: double

Output

V_wind — Mean wind speed

three-element vector

Mean wind speed, returned as a three-element vector in the same body coordinate reference as the DCM input, in specified units.

Data Types: double

Parameters

Units — Wind shear units

Metric (MKS) (default) | English (Velocity in ft/s) | English (Velocity in kts)

Wind shear units, specified as:

Units	Wind	Altitude
Metric (MKS)	Meters/second	Meters
English (Velocity in ft/s)	Feet/second	Feet
English (Velocity in kts)	Knots	Feet

Programmatic Use

Block Parameter: units

Type: character vector

Values: 'Metric (MKS)' | 'English (Velocity in ft/s)' | 'English (Velocity in kts)'

Default: 'Metric (MKS)'

Flight phase — Flight phase

Category C - Terminal Flight Phase (default) | Other

Flight phase, specified as:

• Category C - Terminal Flight Phase, as specified by Military Specification MIL-F-8785C.

• Other

Programmatic Use

Block Parameter: phase

Type: character vector

Values: 'Category C - Terminal Flight Phase' | 'Other'

Default: 'Category C - Terminal Flight Phase'

Wind speed at 20 ft altitude (kts) — Wind speed

15 (default) | scalar

Measured wind speed at a height of 6 m (20 ft) above the ground, specified as a scalar.

Programmatic Use

Block Parameter: W_20

Type: character vector

Values: scalar

Default: '15'

Wind direction at 20 ft altitude (degrees clockwise from north) — Wind direction

0 (default) | scalar

Wind direction at a height of 6 m (20 ft) above the ground, specified as a scalar, in degrees clockwise from the direction of the Earth x-axis (north). The wind direction is defined as the direction from which the wind is coming.

Programmatic Use

Block Parameter: Wdeg

Type: character vector

Values: scalar

Default: '0'

Algorithms

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.

$$u_w=W_{20}\frac{\ln \left(\frac{h}{z_0}\right)}{\ln \left(\frac{20}{z_0}\right)},3ft<h<1000ft$$

where u_w is the mean wind speed, W₂₀ is the measured wind speed at an altitude of 20 feet, h is the altitude, and z₀ is a constant equal to 0.15 feet for Category C flight phases and 2.0 feet for all other flight phases. Category C flight phases are defined in reference [1] to be terminal flight phases, which include takeoff, approach, and landing.

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.

References

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

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a