BSA Flow Software Installation and User's Guide - CSI

5.15 Transform
5.15.1 Co-ordinate transformation of individual velocity samples
The object Transform will perform a coordinate transformation of the
measured velocity-components based on a transformation matrix provided
by the user. The velocity-samples used must be coincident. Other data
(position, analog inputs, particle diameter etc.) are passed through the
Transform object unchanged.
It is possible to apply more than one transform. For example, with 3D optics
it may be practical to have a fundamental transform for the optical system,
followed by one ore more transforms referring to the pan and tilt position of
the optics. In this way, only the pan or tilt-related transform needs to be
modified if the orientation of the optics is changed.
With velocity channels in the same group, velocity samples are coincident.
If the velocity channels are in separate groups, a Coincidence-object should
be applied prior to the Transform object.
Note It is possible to create the Transform-object as a direct child-object of a
data-source object (BSA F/PApplication or Import Velocity file). This
should only be attempted if you are sure that velocity-samples supplied by
the data-source are indeed coincident, since coordinate transformation is
otherwise impossible, and an error message will be generated.
Normally co-ordinate transformation is used, when limited optical access or
other physical restraints have forced velocities to be measured along
directions not coinciding with the co-ordinate directions otherwise used in
the model and in calculations. In such cases orthogonal velocity-components
u, v and w can be calculated from “skew” components u1, u2 and u3
according to the matrix calculation:
⎡ u ⎤ ⎡C
C C
⎢ ⎥ ⎢
⎢ v ⎥ = ⎢C
C C
⎢ ⎥ ⎢
⎣⎢
w⎦⎥
⎣⎢
C C C
11 12 13
21 22 23
31 32 33
⎤ ⎡u
1 ⎤
⎥ ⎢ ⎥
⎥ ⎢u
2 ⎥
⎥ ⎢ ⎥
⎦⎥
⎣⎢
u ⎦⎥
3
By default velocity component u1 is assumed to come from the first
processor channel, u2 from the second and u3 from the third. It will be
assumed by default that LDA1 supplies u1, LDA2 supplies u2 and LDA3
supplies u3, but if necessary this can be changed editing the general
properties of the transform object:
5-78 BSA Flow Software: Project explorer objects