flowrate would be called something like that:
class Liquids() {
void Flowrate(int flow) {
while parts[i] == thisParticle {
parts[i].diffus = flow;
printf ("Flowrate:", flow)
} // etc etc etc diffus etc
PT_OILL { /* OILL */ /.../ , 2, /.../};
PT_Shizz{/*SHIZ*/, etcetc}
int flowRate = PT_particle[DiffusLocation]
Liquids.Flowrate(flowRate)

I estimated that diffus does the diffusation of particles, simulating viscosity.