Solving the Navier-Stokes equation

[Kaat]

Hi all,
My first post.

I am not sure how does Chorin's Projection method for coupling pressure-velocity differ from the Issa's method of of Pressure Implicit with Splitting of Operators (PISO)?

Franckly speaking both the methods look to solve the poisson equation for pressure and update a conservative flux field. But going to the meat of the matter, where and how do they differ?
Did not find a CFD platform so, asking her;

Kaat

 

[Achy47]

je,

Thank you for your post and welcome to the forum!

To answer your question, the main difference between Chorin's Projection method and Issa's PISO method lies in the way they handle the coupling between pressure and velocity.

In Chorin's method, the pressure and velocity are decoupled in the time-stepping process. First, an intermediate velocity field is calculated using a predictor step, and then the pressure equation is solved to correct the velocity field. This decoupling allows for a simpler and more stable numerical solution, but it may introduce some error in the velocity field.

On the other hand, PISO method uses a semi-implicit approach, where the pressure and velocity equations are solved simultaneously using a fractional step method. This allows for a more accurate solution of the velocity field, but it can also lead to some stability issues and requires a more complex numerical implementation.

In summary, the main difference between Chorin's Projection method and PISO method lies in the way they handle the coupling between pressure and velocity, with Chorin's method being simpler and more stable, while PISO method allows for a more accurate solution but may be more challenging to implement. I hope this helps to clarify the differences between the two methods.