[meshman]

I'm studying the numerical algorithm of pisoFoam which is the basic transient solver in OpenFOAM. And I have a question for the role of momentum predictor in 'UEqns.H'.
When we think the calculation of (u1, p1) from the initial value (u0,p0),
I think that the value of momentum predictor (~ u1') calculated by using the pressure of previous time-step (~ p0) is same with the initial velocity (~u0) in the condition of not using the under-relaxation.
(In other words, I think that u1' equals with u0.)

Generally, the under-relaxation is not applied in the transient solver, so is the above conclusion right?

Thank you for reading my question