Variants of SIMPLE

Variants of SIMPLE - Extra Material Variants of SIMPLE:...

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1 Extra Material Variants of SIMPLE: SIMPLER & SIMPLEC
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SIMPLER Algorithm: Motivation The SIMPLE algorithm has been used widely but suffers from a drawback Dropping the terms produces too-large pressure corrections, needing under- relaxation when correcting pressure Under-relaxation factors are problem-dependent Velocity corrections are good though » Are configured to guarantee velocity fields are continuity-satisfying every iteration '' , nb nb nb nb nb nb a u a v 
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Motivation (Cont’d) Idea is to use pressure-correction to correct velocities but not pressure Create a separate equation for pressure computation
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Another Take… Let’s say we start with a good guess of velocity but a bad guess of pressure First step in SIMPLE algorithm is to solve for u*,v* using bad guess p* Even if velocity guess is good, bad p* destroys good velocity guess right away Rest of the iterative procedure is basically trying to recover the good velocity field Need to compute a good pressure field from good velocity guess instead of having to guess it.
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SIMPLER Semi-Implicit Method for Pressure-Linked Equations (Revised) Creates a separate equation for pressure (rather than using p’ equation) Uses p’ equation only to correct velocity
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Pressure Equation Discrete momentum equations: Find velocities
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Pressure Equation (Cont’d) Define hat velocities Momentum equations:
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Pressure Equation (Cont’d) Multiplying hat velocities by density and area: Similarly, from the momentum equations:
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Variants of SIMPLE - Extra Material Variants of SIMPLE:...

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