1. Flow Around A Corner
A particle at (x0,y) will descend at speed U until y=x0.
Ignore gravity
Then it finds itself in a horizontal fluid flow.
Drag force on particle takes more general form:
FD = -(v-u)/B
Solve for particle trajectory in x and y directions.

2. Approaching Drift Velocity
Here we consider the trajectory of a charged particle in a constant electric field
The force on a charged particle is the charge on the particle times the electric field at its location
e is the elementary unit of charge, and –e is the charge on a single electron. Assume the aerosol particle has a single extra electron.
The electric field is calculated as E = -V, where V is the electric potential (voltage)
Parallel plates at different voltages produce a nearly constant field between them. Let V2 > V1. The distance between them is h.
Now consider the generalized force equation for the particle,
Equations of this form have the solution,
Memory of original velocity decays away
A “drift velocity” takes over on same timescale

3. Approaching Drift Velocity
Now that we have solved for velocity, we need to integrate to get trajectory
Assume particle starts at rest, vD = 1 cm/s, t = 10s
z=vDt z
zoffset
The result is that the particle initially accelerates until it approaches a path parallel to the constant drift path.
The offset between these paths asymptotes to