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Wind Shear Model

Calculate wind shear conditions

  • Library:
  • Aerospace Blockset / Environment / Wind

  • Wind Shear Model block

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

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Altitude, specified as a scalar in specified units.

Data Types: double

Direction cosine matrix, specified as a 3-by-3 matrix.

Data Types: double

Output

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Mean wind speed in the body axes frame, returned as a 3-by-1 vector in the selected units.

Data Types: double

Parameters

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Wind shear units, specified as:

UnitsWindAltitude
Metric (MKS) Meters/secondMeters
English (Velocity in ft/s) Feet/secondFeet

English (Velocity in kts)

KnotsFeet

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, 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'

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 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.

uw=W20ln(hz0)ln(20z0), 3ft<h<1000ft

where uw 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™.

Introduced before R2006a