# RhoCentralFoam detail

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 November 5, 2015, 04:55 #41 Member   Xinguang Wang Join Date: Feb 2015 Posts: 45 Rep Power: 11 Dear Luca I ran a supersonic flat plate flow with turbulence, but when I change different limiter of: reconstruct(rho) Minmod; reconstruct(U) Minmod; reconstruct(T) Minmod; such as Minmod, vanLeer, and superBee, the skin friction is quite differnt from each other, the minmod gave the highest value, while the superBee gave the lowest. As for a supersonic flat plate, there is no shock in the boundary layer, i do not know why there is so much difference, when I look into the U file alone y direction, near the wall the limiters influence it. Do you noticed that when you did some simulation? regards, Jason

August 3, 2016, 09:10
#42
New Member

Aaron
Join Date: Apr 2016
Posts: 24
Rep Power: 10
Hi, foamers,
when I search the "neg", the officical document show this:
Quote:
 neg Foam::dimensionSet::neg() Foam::neg(const dimensionedScalar &ds) Foam::neg(const dimensionSet &) Foam::neg(const label s) Foam::neg(const Scalar s) negate negIndexFoam::BiIndirectList negListFoam::BiIndirectList negPart negSumDiag
where is the function using field?

January 25, 2024, 04:05
#43
New Member

Carmelo Baronetto
Join Date: Dec 2023
Posts: 29
Rep Power: 2
Quote:
 Originally Posted by david_h Alberto, I agree with the above statements, if the "face area vectors" point outward from cell i,j. If all the "face area vectors" are pointed either toward the right or to the top, then: on face the between i-1 and i (i-1/2), "pos" would return rho[i-1] "neg" would return rho[i] on face the between i and i+1 (i+1/2), "pos" would return rho[i] "neg" would return rho[i+1] The above is for zero-order reconstruction. For "cell-based" higher order reconstruction (e.g. limited-linear), the face values would take the form: rho_pos[i+1/2] = rho[i] + drho[i]*(x[i+1/2] - x[i]) rho_neg[i+1/2] = rho[i] + drho[i]*(x[i+1/2] - x[i+1]) where drho[i] is limited gradient of rho at cell "i" Dave

Good morning,
sorry to reopen this old thread, but I'm studying rhoCentraFoam and I would like to understand better how this solver works.

I can't understand when David writes:
Quote:
 rho_neg[i+1/2] = rho[i] + drho[i]*(x[i+1/2] - x[i+1])
I think "negative interpolation" interpolates from x[i+1], so that:
rho_neg[i+1/2] = rho[i+1] + drho[i+1]*(x[i+1/2] - x[i+1])
Is it corret, or am I missing something?

In general, refers to the article:
"Implementation of semi-discrete, non-staggered central schemes in a colocated, polyhedral, finite volume framework, for high-speed viscous flows" by C.J. Greenshields et Al.
it is explained how to compute positive interpolation of a general quantity:

where:

However I can't understand how to compute .
I hope someone can help me.
Thank you