ISA Atmosphere Model
Implement International Standard Atmosphere (ISA)
Libraries:
Aerospace Blockset /
Environment /
Atmosphere
Description
The ISA Atmosphere Model block implements the mathematical representation of the International Standard Atmosphere (ISA) values for ambient temperature, pressure, density, and speed of sound for the input geopotential altitude.
The ISA Atmosphere Model, Extended ISA model, and Lapse Rate Model blocks are identical blocks. The ISA Atmosphere Model block has three implementations:
The default ISA model implements the mathematical representation of the ISA values for ambient temperature, pressure, density, and speed of sound for the input geopotential altitude between sea level (0 m) and tropopause (20000 m).
The extended ISA model implements the mathematical representation of the ISA values for ambient temperature, pressure, density, and speed of sound for the input geopotential altitude between -5000 m and mesopause (84852 m).
The Lapse rate model implements custom lapse rate atmosphere model using the input parameters.
The ISA Atmosphere Model block icon displays the input and output port labels in metric units.
Limitations
In the default model, the block limits the implementation to the geopotential altitude of 0 m (minimum) and 20000 m (maximum). In the extended model, the limits are -5000 meters (minimum) and 84852 meters (maximum). The limits are inclusive.
Density and speed of sound are calculated using a perfect gas relationship.
Ports
Input
h (m) — Geopotential height
scalar | m-by-n array
Geopotential height, specified as a scalar or m-by-n array.
Data Types: double
Output
T (K) — Temperature
scalar | m-by-n array
Temperature, returned as a scalar or m-by-n array, in K.
Data Types: double
a (m/s) — Speed of sound
scalar | m-by-n array
Speed of sound, returned as a scalar or m-by-n array, in m/s.
Data Types: double
P (Pa) — Air pressure
scalar | m-by-n array
Air pressure, returned as a scalar or m-by-n array, in Pa.
Data Types: double
ρ (kg/m3) — Densities
scalar | m-by-n array
Densities, returned as a scalar or an m-by-n array, in kg/m3.
Data Types: double
ν (m2/s) — Kinematic viscosity
scalar | m-by-n array
Kinematic viscosity, returned as a scalar or m-by-n array, in m2/s.
Dependencies
Selecting the Output kinematic and dynamic viscosity check box adds the ν (m2/s) output port.
Data Types: double
μ (N s/m2) — Dynamic viscosity
scalar | m-by-n array
Dynamic viscosity, returned as a scalar or m-by-n array, in N s/m2.
Dependencies
Selecting the Output kinematic and dynamic viscosity check box adds the μ (N s/m2) output port.
Data Types: double
Parameters
Use extended ISA model — Range of implementation
off
(default) | on
Mathematical representation of the International Standard Atmosphere model.
To implement the mathematical representation of the ISA values for ambient temperature, pressure, density, and speed of sound for the input geopotential altitude between the sea level and the tropopause, clear this checkbox. For input heights outside the limits, the output values are held constant.
To implement the mathematical representation of the ISA values for ambient temperature, pressure, density, and speed of sound for the input geopotential altitude between -5000 meters and the mesopause, select this check box. For input heights outside the limits, the output values are held constant if the out-of-range action input is set as
None
orWarning
.
Dependencies
Selecting this check box removes the Change atmospheric parameters check box.
Programmatic Use
Block Parameter:
useExtended |
Type: character vector |
Values:
'off' | 'on'
|
Default:
'off' |
S — Sutherland temperature
110.4 K (default) | scalar
Sutherland temperature in Kelvin, specified as a scalar.
Dependencies
This optional input is available when the Output kinematic and dynamic viscosity and Change atmospheric parameters are e.
Tref — Reference temperature
273.15 K (default) | scalar
Reference temperature in Kelvin, specified as a scalar.
Dependencies
This optional input is available when the Output kinematic and dynamic viscosity is selected.
Dependencies
This optional input is available when the Output kinematic and dynamic viscosity and Change atmospheric parameters are e.
μref — Reference dynamic viscosity
1.716e-5 kg/ms (default) | scalar
Reference dynamic viscosity in kilograms per meter second, specified as a scalar.
Dependencies
This optional input is available when the Output kinematic and dynamic viscosity and Change atmospheric parameters are e.
Output kinematic and dynamic viscosity — Option to output kinematic and dynamic viscosity
off
(default) | on
Option to output kinematic and dynamic viscosity.
Dependencies
Selecting this check box:
Adds the ν (m2/s) output port.
Adds the μ (N s/m2) output port.
Dependencies
If selected simultaneously with the Change atmospheric parameters checkbox, adds the Viscosity parameters tab.
Programmatic Use
Block Parameter:
viscosityOut |
Type: character vector |
Values:
'off' | 'on'
|
Default:
'off' |
Action for out-of-range input — Out-of-range block behavior
Warning
(default) | Error
| None
Out-of-range block behavior, specified as follows:
Action | Description |
---|---|
None
| No action. |
Warning
| Warning in the Diagnostic Viewer, model simulation continues. |
Error | Error in the Diagnostic Viewer, model simulation stops. |
Dependencies
To enable this parameter, select Use extended ISA model.
If this parameter is not visible, the default action is
None
.
Programmatic Use
Block Parameter:
action |
Type: character vector |
Values:
'None' | 'Warning' |
'Error' |
Default:
'Warning' |
Change atmospheric parameters — Customize parameters
off
(default) | on
Customize various atmospheric parameters to be different from the ISA values. Selecting this check box converts the block from ISA Atmosphere Model to Lapse Rate Model.
Dependencies
Selecting this check box enables the Atmospheric parameters tab with these parameters:
Acceleration due to gravity (m/s^2)
Ratio of specific heats
Characteristic gas constant (J/Kg/K)
Lapse rate (K/m)
Height of troposphere (m)
Height of tropopause (m)
Air density at mean sea level (Kg/m^3)
Ambient pressure at mean sea level (N/m^2)
Lowest altitude (m)
Selecting in conjunction with Output kinematic and dynamic viscosity enables the Viscosity parameters tab with these parameters:
S
Tref
μref
Selecting this check box removes the Use extended ISA model check box.
Programmatic Use
Block Parameter:
custom |
Type: character vector |
Values:
'off' | 'on'
|
Default:
'off' |
Acceleration due to gravity (m/s^2) — Acceleration
9.80665
(default) | scalar
Acceleration from gravity (g). in m/s2, specified as double scalar.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
g |
Type: character vector |
Values: double scalar |
Default:
9.80665 |
Ratio of specific heats — Ratio of heats
1.4
(default) | scalar
Ratio of specific heats γ, specified as a double value.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
gamma |
Type: character vector |
Values: double scalar |
Default:
1.4 |
Characteristic gas constant (J/Kg/K) — Gas constant
287.0531
(default) | scalar
Characteristic gas constant (R), specified as double scalar, in J/Kg/K.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter: R |
Type: character vector |
Values: double scalar |
Default: 287.0531 |
Lapse rate (K/m) — Lapse rate
0.0065
(default) | scalar
Lapse rate of the troposphere, specified as double scalar, in K/m.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
L |
Type: character vector |
Values: double scalar |
Default: 0.0065 |
Height of troposphere (m) — Troposphere height
11000
(default) | scalar
Height of the troposphere (range of decreasing temperatures), specified as double scalar, in m.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
h_trop |
Type: character vector |
Values: double scalar |
Default:
11000 |
Height of tropopause (m) — Tropopause height
20000
(default) | scalar
Height of the tropopause (range of constant temperature), specified as double scalar, in m.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
h_strat |
Type: character vector |
Values: double scalar |
Default:
20000 |
Air density at mean sea level (Kg/m^3) — Air density
1.225
(default) | scalar
Air density at mean sea level, specified as double scalar, in Kg/m3.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
rho0 |
Type: character vector |
Values: double scalar |
Default:
1.225 |
Ambient pressure at mean sea level (N/m^2) — Ambient pressure
101325
(default) | scalar
Ambient pressure at mean sea level, specified as double scalar, in N/m2.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
P0 |
Type: character vector |
Values: double scalar |
Default:
101325 |
Ambient temperature at mean sea level (K) — Ambient temperature
288.15
(default) | scalar
Ambient temperature at mean sea level (T0), specified as double scalar, in K.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
K |
Type: character vector |
Values: double scalar |
Default:
101325 |
Lowest altitude (m) — Lowest altitude
0
(default) | scalar
Lowest altitude above which temperature and pressure lapse, specified as double scalar, in m. Lowest altitude (m) must be below Height of tropopause.
Dependencies
This parameter is enabled when the Change atmospheric parameters check box is selected.
Programmatic Use
Block Parameter:
h0 |
Type: character vector |
Values: double scalar |
Default:
0 |
Algorithms
The dynamic viscosity is computed using [1]:
The kinematic viscosity is computed using [1]:
where:
β — A constant dependent on the reference temperature and dynamic viscosity.
T — Kelvin kinetic temperature.
S — Sutherland constant.
ρ — Mass density of air.
References
[1] U.S. Standard Atmosphere., Washington, D.C.: U.S. Government Printing Office, 1976.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.
Version History
Introduced before R2006aR2024a: ISA Atmosphere Model Block Changes
Use the Output kinematic and dynamic viscosity checkbox and edit the Viscosity parameters values to compute the viscosity of any gas in the ISA Atmosphere Model block.
R2023b: ISA Atmosphere Model Block Changes
The ISA Atmosphere Model block now supports geopotential altitude inputs between and including -5000 meters and the mesopause, 84,852 meters. In previous releases, ISA Atmosphere Model supported geopotential altitudes between and including sea level and the tropopause, 20,000 meters.
To support the new capability, the block has these changes:
Use extended ISA model parameter:
To implement the mathematical representation of the International Standard Atmosphere values for ambient temperature, pressure, density, and speed of sound for the input geopotential altitude between the sea level and the tropopause, clear this check box.
To implement the mathematical representation of the International Standard Atmosphere values for ambient temperature, pressure, density, and speed of sound for the input geopotential altitude between -5000 meters and the mesopause, select this check box.
Action for out-of-range input parameter, which lets you specify the action for out-of-range input when the Use extended ISA model check box is selected.
Output kinematic and dynamic viscosity parameter:
To return a numeric array of m-by-n values of kinematic viscosities, in m2/s, in the ν output port.
To return a numeric array of m-by-n values of dynamic viscosities, in N s/m2, in the μ output port.
MATLAB 命令
您点击的链接对应于以下 MATLAB 命令:
请在 MATLAB 命令行窗口中直接输入以执行命令。Web 浏览器不支持 MATLAB 命令。
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .
You can also select a web site from the following list:
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
Europe
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)