Question

The PISO algorithm for the transient problem is _________

(a) iterative

(b) non-iterative

(c) never converging

(d) fast converging

This question was addressed to me in homework.

My question is based upon Transient SIMPLE and PISO Algorithms topic in section Transient Flows of Computational Fluid Dynamics

Answer 1

The correct answer is:

(a) iterative

Explanation:

The PISO (Pressure Implicit with Splitting of Operators) algorithm is an iterative method used for solving transient problems in computational fluid dynamics (CFD). It is designed to improve the accuracy of pressure-velocity coupling in transient simulations, particularly for incompressible flow.

In the PISO algorithm, multiple pressure corrections are performed within a time step to ensure better convergence of the pressure field and velocity field. This iterative approach helps in achieving a more accurate solution for the velocity and pressure fields at each time step, especially in problems with rapid changes in flow.

Why not the other options?

• (b) non-iterative: The PISO algorithm is explicitly iterative, meaning it requires multiple passes to solve for the pressure and velocity fields at each time step.

• (c) never converging: This is incorrect because, when implemented correctly, the PISO algorithm converges iteratively and is used to improve convergence in transient flows.

• (d) fast converging: While the PISO algorithm can lead to better convergence compared to simpler methods like SIMPLE (especially in transient flows), whether it is "fast" depends on the specific problem and implementation. It is primarily considered an iterative method, not necessarily "fast converging."

Correct Answer: (a) iterative