# Computational Fluid Dynamics Questions and Answers – Incompressible Flows – SIMPLER Algorithm

This set of Computational Fluid Dynamics Multiple Choice Questions & Answers (MCQs) focuses on “Incompressible Flows – SIMPLER Algorithm”.

1. What does the R in the SIMPLER algorithm stand for?
a) Rewritten
b) Revised
c) Republished
d) Refresh

Explanation: The SIMPLER algorithm stands for SIMPLE – Revised algorithm. This was introduced by Patankar who had worked for building the SIMPLE algorithm also. This was introduced in the year 1980.

2. What is the difference between the SIMPLE and the SIMPLER algorithms?
a) No velocity-correction equation
b) No relaxation factor
c) Pressure is directly calculated
d) No pressure-correction equation

Explanation: The SIMPLE algorithm uses a correction factor for correcting the initial guessed pressure. But, this SIMPLER algorithm does not involve any guess and correction of pressure. It has an equation which can be solved to directly get the pressure values.

3. What is the disadvantage of using the SIMPLE algorithm over the SIMPLER one?
a) The pressure field does not satisfy the momentum equation
b) The pressure field does not satisfy the continuity equation
c) The velocity field does not satisfy the continuity equation
d) The velocity field does not satisfy the momentum equation

Explanation: In the SIMPLE algorithm, the velocity field is initially guessed using the momentum equation. Then, corrections are made using the continuity equation. But, once corrected, the velocity field does not satisfy the momentum equations.

4. The equation for pressure of the SIMPLER algorithm is obtained using _________
a) continuity equation in the PDE form
b) discretized continuity equation
c) momentum equation in the PDE form
d) discretized momentum equation

Explanation: Obtaining the pressure values in the SIMPLER algorithm is simpler than in the SIMPLE algorithm. In the SIMPLER case, a discretized equation for pressure is obtained using the continuity equation. Solving this, pressure values can be obtained.

5. Which of these is correct about the SIMPLER algorithm?
a) Velocity is obtained without any correction
b) Velocity is obtained using the pressure values and the continuity equation
c) Prediction-correction is used for the velocity field
d) Velocity is obtained using the pressure values and the momentum equation

Explanation: Though the pressure field in the SIMPLER algorithm does not need any guess and correction, the velocity field still needs a prediction-correction method. It is found in a similar way as in the SIMPLE algorithm.
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6. Which of these equations is used in the SIMPLER algorithm for updating the pressure values?
a) Pressure-correction equation
b) Discretized pressure equation
c) Momentum equation
d) Continuity equation

Explanation: In the SIMPLER algorithm, the velocity field should be corrected. For this correction and updating purpose, the pressure correction equation is used as in the SIMPLE algorithm. Therefore, the momentum equations are also satisfied.

7. The source term in the pressure equation of the SIMPLER algorithm is obtained using ___________
a) velocities in the previous iteration
b) pressure in the previous iteration
c) pseudo-neighbours
d) pseudo-velocities

Explanation: The discretized pressure equation of the SIMPLER algorithm is the same as the pressure correction equation obtained for the SIMPLE algorithm. The only difference is that the source term here is obtained from the pseudo velocities.

8. The pseudo-velocities of the SIMPLER algorithm are obtained from _________
a) continuity equation in the PDE form
b) discretized momentum equation
c) discretized pressure equation
d) discretized pressure-correction equation

Explanation: The discretized momentum equation is taken. From this equation, the pseudo-velocities of the SIMPLER algorithm are obtained. The momentum equation is then written in terms of these pseudo-velocities for further use.

9. Which of these terms is not included in the pseudo-velocities?
a) Pressures in the current and previous iterations
b) Momentum sources
c) Neighbouring velocities
d) Coefficients of the current velocities

Explanation: The pseudo-velocity is given as
$$\hat{u}_{i,j}=\frac{\sum a_{nb} u_{nb}+b_{i,j}}{a_{i,j}}$$
Where,
unb → Neighbouring velocities.
bi,j → Source of momentum.
ai,j → Coefficient of the current velocity.

10. The velocity-corrections in the SIMPLER algorithm depends on ____________
a) pressure equation
b) pressure-correction equation
c) pressure corrections
d) pressure values

Explanation: There is pressure correction involved in the SIMPLER algorithm. But, this pressure correction is not used to correct the pressure values. Instead, it is used to correct the velocity values.

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