/IMPVEL

Block Format Keyword Defines imposed velocities on a group of nodes.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)
/IMPVEL/`impvel_ID`/`unit_ID`
`impvel_title`
`fct_ID`_T	`Dir`	`Skew_ID`	`sens_ID`	`grnd_ID`	`frame_ID`	`icoor`
`Ascale`_x		`Fscale`_Y		`T`_start		`T`_stop

Definitions

Field	Contents	SI Unit Example
`impvel_ID`	Imposed velocity block identifier. (Integer, maximum 10 digits)
`unit_ID`	Unit Identifier (Integer, maximum 10 digits)
`impvel_title`	Imposed velocity block title. (Character, maximum 100 characters)
`fct_ID`_T	Time function identifier. (Integer)
`Dir`	Direction: X, Y, and Z in translation; XX, YY, and ZZ in rotation. (Text)
`Skew_ID`	Skew identifier. ≠ 0 The imposed velocity is computed in the global frame and projected onto the local skew. (Integer)
`sens_ID`	Sensor identifier. ≠ 0 (sensor activated) The imposed velocity is applied after sensor activation. The time function is shifted by the sensor activation time. (Integer)
`grnd_ID`	Node group on which the imposed velocity is applied. (Integer)
`frame_ID`	Frame identifier. ≠ 0 The imposed velocity is computed and applied in the local frame. (Integer)
`icoor`	Coordinate system usage type. = 0 Cartesian coordinates. = 1 Cylindrical coordinates. (Integer)
`Ascale`_x	Abscissa (time) scale factor for `fct_ID`_T. Default = 1.0 (Real)	$[s]$
`Fscale`_Y	Ordinate (velocity) scale factor for `fct_ID`_T. Default = 1.0 (Real)	$[\frac{m}{s}]$ or $[\frac{rad}{s}]$
`T`_start	Start time (Real)	$[s]$
`T`_stop	Stop time Default = 10³⁰ (Real)	$[s]$

Comments

The velocity direction must be right justified in the ten characters of field number 2.
If a velocity is imposed in a frame (frame_ID ≠ 0), the frame nodes must not have an imposed velocity themselves.
If T_start and T_stop are specified, the velocity is imposed between these times, but the time vs. velocity function is not shifted to begin at T_start.
When a sensor is defined sens_ID, the imposed velocity is applied at the time of sensor activation and the function is shifted by the sensor activation time.
When a sensor sens_ID is used with T_start and T_stop, the imposed velocity will only occur if the sensor activation time occurs between T_start and T_stop.
The Ascale_X and Fscale_Y are used to scale the abscissa (time) and ordinate (translational or angular velocity).
The actual load function value is calculated as:(1)
$F (t) = F s c a l e_{y} \cdot f_{T} (\frac{t}{A s c a l e_{x}})$

Where, $f_{T}$ is the function of fct_ID_T.
SKEW and FRAME cannot be defined together. This is SKEW or FRAME.
If icoor=1, the directions X, Y, and Z (resp. XX, YY, and ZZ) refer to translations along (resp. rotations around) the radial direction (r), azimuthal angular direction ( $θ$ ) and longitudinal direction (Z) (refer to /SKEW/FIX and /FRAME/FIX).

Figure 1.
If icoor=1 when imposing the translational velocity in the radial, resp. the azimuthal direction, the velocity of the node is set so that:(2)
$\dot{r} = F s c a l e_{y} \cdot f_{T} (\frac{t}{A s c a l e_{x}})$
(3)
$r e s p . \dot{θ} = F s c a l e_{y} \cdot f_{T} (\frac{t}{A s c a l e_{x}})$

with $v = \dot{r} e_{r} r + r \dot{θ} e_{_{θ}} + \dot{z} e_{z}$