Flow Geometry & Flow Reversal
The  effect of flow reversal through a tortuous flow channel of lab-on-valve (LOV) conduit is difficult to imagine and it would be truly valuable, if even an approximate modeling of this process would be attempted.

The sample/reagent zone passes, within LOV module (A) through the following components:

Port inlet (a),
valve rotor (b) and
tube connector (c).

The flow reversal in a straight tube
can be imagined to form a multilayer
structure (B) within which sample and
reagent penetrate while the reaction
product is being formed (Ch 2.2.8).
During the subsequent tortuous passage
of the LOV module the radial mixing is
Enhanced. In absence of theory, or modeling,
we must be content with the information that can be gleaned from the dye tracer experiments.