Aerodynamic Forces and Moments (GOST)

Calculation of aerodynamic forces and moment according to GOST 20058-80.

blockType: SubSystem

Path in the library:

/Aerospace/Aerodynamics/Aerodynamic Forces and Moments (GOST)

Description

Block Aerodynamic Forces and Moments (GOST) calculates the components of the aerodynamic force and the aerodynamic moment relative to the center of gravity of the aircraft, taking into account the selected coordinate systems for the input signals, force and moment according to GOST 20058-80.

The block uses coordinate systems according to GOST 20058-80.

The components of aerodynamic force:

where

— coefficient of longitudinal (axial) force;
— lateral force coefficient;
— the coefficient of normal force;
— high-speed pressure;
— the reference area.

Components of the aerodynamic moment:

where

— coefficient of longitudinal (axial) force;
— lateral force coefficient;
— the coefficient of normal force;
— roll moment coefficient;
— the coefficient of pitch moment;
— coefficient of yaw moment;
— wingspan (reference size for roll and yaw moments);
— average aerodynamic chord (reference size for pitch moment);
, , — coordinates of the center of gravity;
, , — coordinates of the pressure center.

Conversion of coefficients and axes

The unit supports operation in connected, semi-connected, and velocity coordinate systems for input signals, aerodynamic forces, and torque. Internal transformations are performed using angles of attack and sliding and rotation matrices.

The rotation from a connected coordinate system to a semi-connected one is performed using a matrix:

The rotation from a semi-connected coordinate system to a high-speed one is carried out using a matrix:

The final turn from the associated coordinate system to the velocity one is obtained by the product of rotation matrices and :

Ports

Entrance

# Coef — aerodynamic coefficients

+ The vector is 6 by 1

Details

The coefficients of the components of the aerodynamic force and moment along the axes in the selected coordinate system, set as a vector.

Vector elements for the associated coordinate system:

— coefficient of longitudinal force.
— the coefficient of normal force.
— coefficient of lateral force.
— roll moment coefficient.
— coefficient of yaw moment.
— the coefficient of pitch moment.

Vector elements for a semi-connected coordinate system:

— drag coefficient.
— coefficient of lifting force.
— the coefficient of lateral force.
— roll moment coefficient.
— coefficient of yaw moment.
— the coefficient of pitch moment.

Vector elements for the velocity coordinate system:

— drag coefficient.
— coefficient of lifting force.
— the coefficient of lateral force.
— roll moment coefficient.
— coefficient of yaw moment.
— the coefficient of pitch moment.

Dependencies

The lower index in the port name depends on the one selected in the parameter Input axes: coordinate systems:

Body — port name Coef;
Stability — port name Coef_e;
Wind — port name Coef_a.

Data types	`Float64`
Support for complex numbers	None

# q — high- speed pressures

+ a 3-by-1 vector

Details

The velocity pressures calculated from the components of the speed of the aircraft along the axes of the associated coordinate system, set as a vector.

Data types	`Float64`
Support for complex numbers	None

# CG — coordinates of the center of gravity

+ a 3-by-1 vector

Details

Coordinates of the aircraft’s center of gravity, set as a vector. They are measured in units of length.

Data types	`Float64`
Support for complex numbers	None

# CP — coordinates of the pressure center

+ a 3-by-1 vector

Details

The coordinates of the aircraft’s pressure center, set as a vector. They are measured in units of length.

Data types	`Float64`
Support for complex numbers	None

# V — components of the speed of the aircraft

+ a 3-by-1 vector

Details

The components of the speed of the aircraft, set as a vector.

Dependencies

To use this port, set at least one of the parameters Input axes:, Force axes:, Moment axes: meaning Stability or Wind.

Data types	`Float64`
Support for complex numbers	None

Output

# XYZ — aerodynamic forces

+ a 3-by-1 vector

Details

The components of the aerodynamic force relative to the center of mass of the aircraft in the selected coordinate system, returned as a vector. Vector elements:

— longitudinal force.
— normal strength.
— lateral force.

They are measured in units of force.

Dependencies

The lower index in the port name depends on the one selected in the parameter Force axes: coordinate systems:

Body — port name XYZ;
Stability — port name X_eY_eZ_e;
Wind — port name X_aY_aZ_a.

Data types	`Float64`
Support for complex numbers	None

# M_xM_yM_z — aerodynamic moments

+ a 3-by-1 vector

Details

The components of the aerodynamic moment relative to the center of mass of the aircraft in the selected coordinate system, returned as a vector. Vector elements:

— aerodynamic roll moment.
— aerodynamic yaw moment.
— aerodynamic pitch moment.

They are measured in units of moment.

Dependencies

The lower index in the port name depends on the one selected in the parameter Moment axes: coordinate systems:

Body — port name M_xM_yM_z;
Stability — port name M_xeM_yeM_ze;
Wind — port name M_xaM_yaM_za.

Data types	`Float64`
Support for complex numbers	None

Parameters

# Input axes: — coordinate system for the input aerodynamic coefficients
Body | Stability | Wind

Details

The coordinate system for the input aerodynamic coefficients.

Dependencies

If values are set for this parameter Stability or Wind, then the input port V is used in the block.

Values	`Body` \| `Stability` \| `Wind`
Default value	`Body`
Program usage name	`inputAxes`
Tunable	No
Evaluatable	Yes

# Force axes: — coordinate system for aerodynamic force
Body | Stability | Wind

Details

The coordinate system for the aerodynamic force.

Dependencies

If values are set for this parameter Stability or Wind, then the input port V is used in the block.

Values	`Body` \| `Stability` \| `Wind`
Default value	`Body`
Program usage name	`outputForceAxes`
Tunable	No
Evaluatable	Yes

# Moment axes: — the coordinate system for the aerodynamic moment
Body | Stability | Wind

Details

The coordinate system for the aerodynamic moment.

Dependencies

If values are set for this parameter Stability or Wind, then the input port V is used in the block.

Values	`Body` \| `Stability` \| `Wind`
Default value	`Body`
Program usage name	`outputMomentAxes`
Tunable	No
Evaluatable	Yes

# Reference area — characteristic area

Details

The characteristic area of the aircraft. It is measured in units of area. For an airplane, the wing area is usually taken as the characteristic area.

Default value	`1.0`
Program usage name	`S`
Tunable	No
Evaluatable	Yes

# Reference span — the average aerodynamic chord of the wing

Details

The average aerodynamic chord of the wing. It is measured in units of length.

Default value	`1.0`
Program usage name	`b`
Tunable	No
Evaluatable	Yes

# Reference length — characteristic linear size

Details

The characteristic linear size of the aircraft. It is measured in units of length. For an aircraft, the wingspan is usually taken as the characteristic linear size.

Default value	`1.0`
Program usage name	`cbar`
Tunable	No
Evaluatable	Yes