BSA Flow Software Installation and User's Guide - CSI

Trajectory dependent detection area (X-Y)
Figure 7-81: Transit time versus particle size. (2D plot)
In making size, concentration or mass flux measurements, the number of
particles detected and measured is always with respect to a reference crosssectional
area. For particle trajectories in the X- or Y-direction, these
reference areas, A x and A y are given in the previous section. If however, the
particle has a different trajectory within the XY-plane, the effective area over
which particle detection takes place will be altered. This is illustrated in
Figure 7-82 for the reference area normal to the X-coordinate. The effective
area becomes:
A'
x
Ax Ls de
= = ∗
cosγ sin φ cosγ
for all particles which just pass through the detection limit defined by d e .
Particle
Trajectory
d e
d /cos γ
e
dv t
Figure 7-82: Effective detection area normal to the X-axis.
Similarly, the area normal to the Y-direction will be altered according to:
A'
Flux and concentration
y
A L d π d
= = ∗ +
sin γ sin φ sin γ 4 sin
2
y s e e
2
cot φ
γ
The angle γ is just given by the measured velocity components of the
particle:
γ =
−
tan 1 v
u
The volume flux can be computed for each vector component. The
appropriate expressions for a 2D system are:
f
vx
n 3
π Di
cosγ
i
= ∑ 6∆t
A ( D )
i=
1
x k
BSA Flow Software:Reference guide 7-119
γ
Y