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The relationship between pressure-based and density-based algorithmsThe PISO, pressure-based algorithm, is compared with implicit time-marching systems to ascertain their similarities and differences. Both methods are expressed in vector form for comparison purposes. The vector form of the PISO method is triangular, allowing an uncoupled solution procedure, while the Euler implicit method requires the simultaneous solution of all equations. Upwind differencing is performed according to the direction of the eigenvalues in both systems, but this is the particle velocity in the PISO method and the acoustic velocity in the Euler method. Vector stability calculations show that the PISO method is conditionally stable depending on the time step, but that it provides adequate damping at small time steps to enable good convergence. Unconditional stability can be provided by retaining the energy coupling terms in the time derivative. Transforming the Euler implicit equations to the PISO variables along with a modification of the time derivatives gives the density-based method the same amplification factors at low speeds as the pressure-based method without affecting their behavior at high speeds.
Document ID
19920049038
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Merkle, Charles L.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Venkateswaran, Sankaran
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Buelow, Philip E. O.
(Pennsylvania State University University Park, United States)
Date Acquired
August 15, 2013
Publication Date
January 1, 1992
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
AIAA PAPER 92-0425
Accession Number
92A31662
Funding Number(s)
CONTRACT_GRANT: NAS8-38861
Distribution Limits
Public
Copyright
Other

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