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Discrete Wind Gust Model

Generate discrete wind gust

  • Library:
  • Aerospace Blockset / Environment / Wind

  • Discrete Wind Gust Model block

Description

The Discrete Wind Gust Model block implements a wind gust of the standard “1-cosine” shape. This block implements the mathematical representation in the Military Specification MIL-F-8785C [1]. The gust is applied to each axis individually, or to all three axes at once. You specify the gust amplitude (the increase in wind speed generated by the gust), the gust length (length, in meters, over which the gust builds up) and the gust start time. For more information on the gust shape, see Algorithms.

The Discrete Wind Gust Model block can represent the wind speed in units of feet per second, meters per second, or knots.

Ports

Input

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Airspeed, specified as a scalar, in selected units.

Data Types: double

Output

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Wind speed, returned as a scalar, in selected units.

Data Types: double

Parameters

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Units of wind gust, 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)'

To apply a wind gust to the u-axis in the body frame, select this check box. Otherwise, clear this check box.

Programmatic Use

Block Parameter: Gx
Type: character vector
Values: 'on' | 'off'
Default: 'on'

To apply a wind gust to the v-axis in the body frame, select this check box. Otherwise, clear this check box.

Programmatic Use

Block Parameter: Gy
Type: character vector
Values: 'on' | 'off'
Default: 'on'

To apply a wind gust to the w-axis in the body frame, select this check box. Otherwise, clear this check box.

Programmatic Use

Block Parameter: Gz
Type: character vector
Values: 'on' | 'off'
Default: 'on'

Model time, specified as a scalar, at which the gust begins, in seconds.

Programmatic Use

Block Parameter: t_0
Type: character vector
Values: scalar
Default: '5'

The length, in meters or feet (depending on the choice of units), over which the gust builds up in each axis. These values must be positive.

Programmatic Use

Block Parameter: d_m
Type: character vector
Values: vector
Default: '[120 120 80]'

The magnitude of the increase in wind speed caused by the gust in each axis. These values may be positive or negative.

Programmatic Use

Block Parameter: d_m
Type: character vector
Values: vector
Default: '[3.5 3.5 3.0]'

Algorithms

This figure shows the shape of the gust with a start time of zero. The parameters that govern the gust shape are indicated on the diagram.

To assess airplane response to large wind disturbances, you can use the discrete gust singly or in multiples.

The mathematical representation of the discrete gust is:

Vwind={0x<0Vm2(1cos(πxdm))0xdmVmx>dm

where Vm is the gust amplitude, dm is the gust length, x is the distance traveled, and Vwind is the resultant wind velocity in the body axis frame.

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