Presto!

Raymond_1981 · June 22, 2020, 07:51

Hi guys,

I have some difficulties understanding how the PRESTO! scheme works.

The theory guide says: "The PRESTO! (PREssure STaggering Option) scheme uses the discrete continuity balance for a “staggered” control volume about the face to compute the “staggered” (that is, face) pressure. This procedure is similar in spirit to the staggered-grid schemes used with structured meshes [365] (p. 795)."

Does this mean that the pressure is seperatly calculated at the cell faces and stored there? Does anybody know how this is calculated?

I cannot find a paper or book where the PRESTO! scheme is explained in detail.

Cheers!

vinerm · June 22, 2020, 08:20

It is same the method described in Patankar's book, with modifications to suit unstructured meshes.

Raymond_1981 · June 22, 2020, 11:26

Hi vinerm,

Thanks for your response. I have read the chapter about staggered grids in Patankar's book. To summarize (check if I have understood correctly), the pressure is calculated and stored on a staggered grid where the locations of the nodes is determined by some sort of algorithm in Fluent. Interpolation of the pressure is therefore no longer required, since it is stored at the correct location.

Does the part "discrete continuity balance" mean that they have rewritten the discrete continuity equation to incorporate the pressure term, like the pressure Poisson equation?

June 22, 2020, 07:51	Presto!	#1
Raymond_1981 New Member Join Date: Jun 2020 Posts: 6 Rep Power: 5	Hi guys, I have some difficulties understanding how the PRESTO! scheme works. The theory guide says: "The PRESTO! (PREssure STaggering Option) scheme uses the discrete continuity balance for a “staggered” control volume about the face to compute the “staggered” (that is, face) pressure. This procedure is similar in spirit to the staggered-grid schemes used with structured meshes [365] (p. 795)." Does this mean that the pressure is seperatly calculated at the cell faces and stored there? Does anybody know how this is calculated? I cannot find a paper or book where the PRESTO! scheme is explained in detail. Cheers!

June 22, 2020, 08:20	Presto	#2
vinerm Senior Member Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 35	It is same the method described in Patankar's book, with modifications to suit unstructured meshes. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

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June 22, 2020, 11:26		#3
Raymond_1981 New Member Join Date: Jun 2020 Posts: 6 Rep Power: 5	Hi vinerm, Thanks for your response. I have read the chapter about staggered grids in Patankar's book. To summarize (check if I have understood correctly), the pressure is calculated and stored on a staggered grid where the locations of the nodes is determined by some sort of algorithm in Fluent. Interpolation of the pressure is therefore no longer required, since it is stored at the correct location. Does the part "discrete continuity balance" mean that they have rewritten the discrete continuity equation to incorporate the pressure term, like the pressure Poisson equation?