Definition of an Aerodynamic Mesh Interface File (AMIF)

Flightloads > Aero Mesh Interface File Format > Definition of an Aerodynamic Mesh Interface File (AMIF)

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To use “external” aerodynamic codes within MSC.FlightLoads and Dynamics the aerodynamic mesh has to be known. The mesh is needed for different purposes:

1. Mesh geometry has to be known to do any aeroelastic analysis.

2. Mesh geometry is needed for splining.

3. Mesh geometry (external node and element IDs) is used to display results and verify the splines.

To serve all these needs, a simple interface file has been defined. There is a minimum set of information needed to do most of this:

1. Aerodynamic grid points

2. Aerodynamic panels (boxes, elements, or whatever you want to call them)

This minimum set of information will be sufficient to make the aerodynamic mesh known to MSC.FlightLoads and Dynamics and is sufficient to do interactive splining and spline verification in MSC FLD. The following tables describe all entries of an AMIF designed to do all functions described above.

General Rules

1. All fields are separated by one or more spaces (not tabs).

2. The entry name must be upper case and must start in the first column.

3. The order is not important.

Entry: Comment

Comment line which will be ignored by the AMIF reader.


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#

Example:

# This file was created by the XYZ Euler Code.

Entry: SGROUP (Required)

Supergroup name for MSC FLD


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SGROUP	SNAME


SGROUP	lann_1


Field	Contents
SNAME	Supergroup name. The length of the name is limited to 8 characters. Please do not use any blanks or hyphens in the name, use underscores instead.

Entry: AGROUP

Aerodynamic group name which becomes a subgroup of the Supergroup.


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AGROUP	AGID	ANAME


AGROUP	47	Wing_Top


Field	Contents
AGID	Aerodynamic Group ID
ANAME	Name of the of the aerodynamic group. The group name is limited to 31 characters. Please do not use any blanks or hyphens in the name, use underscores instead. These groups are very useful to separate the aerodynamic model into functional components. It is important to split the model into groups to use the splining later on. It is strongly recommended that you split the model into parts like: Left_Wing_Top, Left_Wing_bot, Fuselage_Left, Fuselage_Right and so on. MSC Patran groups will be created automatically from these groups

Entry: ADOF (Required)

DOFs for the aerodynamic grids.


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ADOF	ADOFS


ADOF	123


Field	Contents
ADOFS	The list of degrees of freedom the aerodynamic grids possess. Note that only 125 is currently supported. Nonetheless, this entry is required.

Entry: ACORD

Coordinate frame for aero groups or grids. The coordinate frame definition is based upon the global (MSC Patran) or basic (MSC Nastran) coordinate system.


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ACORD	ACID	XOR	YOR	ZOR	XZA	YZA	ZZA
XXZ	YXZ	ZXZ


ACORD	1	0.0	0.0	0.0	0.0	0.0	1.0
1.0	0.0	0.0


Field	Contents
ACID	Aero coordinate frame ID
XOR	X-location of the origin
YOR	Y-location of the origin
ZOR	Z-location of the origin
XZA	X-location of a point on the z-axis
YZA	Y-location of a point on the z-axis
ZZA	Z-location of a point on the z-axis
XXZ	X-location of a point in the xz plane
YXZ	Y-location of a point in the xz plane
ZXZ	Z-location of a point in the xz plane


Note:	Despite being a free field, this entry must be broken into two records as shown.

Entry: AECORD

Defining the aerodynamic reference coordinate frame. This entry is allowed to appear only once in a AMIF file. If this entry is not in the file the global (MSC Patran) or basic (MSC Nastran) coordinate system will be used as default.


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AECORD	ACID


AECORD	1


Field	Contents
ACID	Aero coordinate frame ID which will be used as aerodynamic reference frame.

Entry: AGRID

Aerodynamic grid point.


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AGRID	GID	X	Y	Z	ACID


AGRID	781	10.456	27.678	1.938	1


Field	Contents
GID	The ID of the aerodynamic grid point
X	X-location of the grid point
Y	Y-location of the grid point
Z	Z-location of the grid point
ACID	Aero coordinate frame ID which is the reference for the grid location. If the ID is 0 or blank the global (MSC Patran) or basic (MSC Nastran) coordinate system will be used for reference.

Entry: EIDSTART

Starting element ID and element ID offset values.


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EIDSTART	SEID	OFFSET


EIDSTART	2000001	10000


Field	Contents
SEID	Starting element ID. This value is of type integer.
OFFSET	Offset to be used when updating the starting element ID. This value is of type integer.


Note:	These data are used to override the equivalent values in the MSC.FlightLoads and Dynamics Options menu.

Entry: AQUAD

Aerodynamic quadrilateral panel.


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AQUAD	APID	G1	G2	G3	G4	AGID


AQUAD	123	12	13	46	45	47


Field	Contents
APID	Aerodynamic panel ID
Gi	Aerodynamic grid point IDs of the connection points. Must be unique.
AGID	Aerodynamic Group ID the panel belongs to.

Remark:

The connection of G1 to G4 is not arbitrary. There are two boundary conditions to observe. The panel normal is defined by the connection grids (see sketch below). The normal of the panel as to point at any place from the structure into the fluid. Second the connection of G1 and G2 has to point roughly into the direction of the x-axis of the aerodynamic coordinate system.

Entry: ATRIA

Aerodynamic triangular panel.


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ATRIA	APID	G1	G2	G3	AGID


ATRIA	123	12	13	46	1234


Field	Contents
APID	Aerodynamic panel ID
Gi	Aerodynamic grid point IDs of the connection points. Must be unique.
AGID	Aerodynamic Group ID the panel belongs to.

Remark:

The connection of G1 to G3 is not arbitrary. The panel normal is defined by the connection grids (see sketch below).