VTORQUE
The VTORQUE statement defines a vector torque that consists of three orthogonal components. You can define the VTORQUE statement through user-specified function expressions in the Adams Solver (C++) dataset or through user-written subroutines.
Format
Arguments
FUNCTION=USER(r1[,...,r30]) | Specifies up to thirty user-defined constants used to compute the torque components in an externally-defined subroutine VTOSUB. |
I=id | Specifies the marker on the part to which Adams Solver (C++) applies the action torque. You must ensure that the I marker is a fixed marker and on a different part than the JFLOAT marker. |
JFLOAT=id | Specifies the marker on the part to which Adams Solver (C++) applies the reaction torque. You must ensure that the JFLOAT marker is a floating marker and on a different part than the I marker. Adams Solver (C++) moves the JFLOAT marker to keep it superimposed on the I marker. Adams Solver (C++) does not calculate reaction forces when the JFLOAT marker is on the ground part. |
RM=id | Specifies the marker which determines the orientation of the torque components. You must ensure that RM is a fixed marker. RM may be the same as I and on any part in the system. |
ROUTINE=libname::subname | Specifies an alternative library and name for the user subroutine VTOSUB. Learn more about the ROUTINE Argument. |
TXYZ=e3d | Specifies the 3D vector expression for the VTORQUE torque relative to the RM marker. |
TX=e | Specifies the magnitude and sign of the x component of the torque exerted by the VTORQUE element. The direction of this torque component is parallel to the x-axis of the RM marker in the sense of the right-hand rule (that is, a positive torque causes a counterclockwise rotation). |
TY=e | Specifies the magnitude and sign of the y component of the torque exerted by the VTORQUE element. The direction of this torque component is parallel to the y-axis of the RM marker in the sense of the right-hand rule (that is, a positive torque causes a counterclockwise rotation). |
TZ=e | Specifies the magnitude and sign of the z component of the torque exerted by the VTORQUE element. The direction of this torque component is parallel to the z-axis of the RM marker in the sense of the right-hand rule (that is, a positive torque causes a counterclockwise rotation). |
Extended Definition
The VTORQUE statement creates an Adams Solver (C++) rotational force element, that applies a vector torque between two parts of the system. The element applies an action to the part to which the I marker belongs and a corresponding reaction to the part to which the JFLOAT marker belongs. The VTORQUE statement establishes the position of the JFLOAT marker. As the system moves, Adams Solver (C++) moves the JFLOAT marker on its part to keep the JFLOAT and I markers superimposed. Thus, Adams Solver (C++) applies the reaction torque to the JFLOAT marker’s part.
The components of the torque depend on expressions or subroutines that you supply. The magnitude of the torque is the square root of the sum of the squares of the magnitudes of the three mutually orthogonal torque components. You can specify these functions using function expressions (see C++ Functions) or user-written FORTRAN subroutines (see User-Written Subroutines).
The direction of the torque action is determined by the resultant vector formed by the three component torque you defined along the RM marker axes. The reaction is equal and opposite to the action.
Formulation
Action
Applied to: I marker
Values:
Values:
where:
■Ta is the action applied to the I marker
■TX is the user-defined function defining the magnitude and sign of the x-component according to the right-hand rule
■TY is the user-defined function defining the magnitude and sign of the y-component according to the right-hand rule
■TZ is the user-defined function defining the magnitude and sign of the z-component according to the right-hand rule
■
is a unit vector along the + x-direction of the RM marker
is a unit vector along the + x-direction of the RM marker ■
is a unit vector along the + y-direction of the RM marker
is a unit vector along the + y-direction of the RM marker ■
is a unit vector along the + z-direction of the RM marker
is a unit vector along the + z-direction of the RM marker Reaction
Applied to: JFLOAT marker
Values:
Tr = -Ta
where Tr is the reaction applied to the JFLOAT marker.
Tip: | Depending on the nature of the desired torque relationship, the RM marker may belong to the same part as the I marker or the JFLOAT marker, or to a third, unrelated part. |
Caution: | The user-defined functions TX, TY, and TZ should be smooth, continuous, and single-valued. These conditions make the solution process very effective. |
Examples 1
VTORQUE/3, I=310, JFLOAT=9911, RM=310,
, TX = -6.*WX(310,9900,310)\
, TY = -6.*WY(310,9900,310)\
, TZ = -6.*WZ(310,9900,310)
, TX = -6.*WX(310,9900,310)\
, TY = -6.*WY(310,9900,310)\
, TZ = -6.*WZ(310,9900,310)
This VTORQUE statement defines a vector torque acting between fixed Marker 310 and floating Marker 9911. Expressions TX, TY, and TZ define the magnitude and sign of the torque components about the x, y, and z axes of the reference marker, which is also Marker 310. Adams Solver (C++) superimposes floating Marker 9911 on Marker 310, and apply the reaction force at that point.
Example 2
VTORQUE/3, I=310, JFLOAT=9911, RM=310,
, TXYZ = -6.*WXYZ(310,9900,310) + [0, SIN(TIME), 0]
Applications
The VTORQUE statement is particularly useful when you need to define a vector torque whose point of application and/or direction is most easily formulated in a coordinate system which moves or is on a different part.
For example, the VTORQUE statement could be used to represent the yaw, pitch, and rolling moments on a flight vehicle (see the figure below). In this instance, the RM marker would be fixed to the vehicle at its aero-dynamic center. You can use a VFORCE statement (see VFORCE) to supply the remaining translational forces, or the GFORCE statement (see GFORCE) to provide all six forces using a single entity. In any event, you can use the reference marker to resolve the aircraft inertial velocity onto aircraft axes for subsequent calculation of aerodynamic forces.
Yaw, Pitch, and Rolling Moments on a Flight Vehicle
Another application where a VTORQUE would significantly simplify modeling and analysis is in consideration of gravitational torques exerted on Earth-orbiting satellites. In this case the RM marker would not be fixed in the satellite or the Earth, but would move with the rotating line segment extending between the satellite and the Earth.
When compared with the SFORCE statement (see SFORCE), the VTORQUE statement offers the advantage that the resultant torque direction (with respect to the RM marker) can vary.
See other Forces available.