Slices (scalar, vector)

[andrej_f]

I have two questions regarding the scalar and vector calculations in
the FDS and their representation in the Smokeview.

1) I understand that Smokeview represents scalar slices as the values
of the particular sell, e.g. the temperature in one cell is uniform
throughout. It is not important where in the cell the slice is
located; the scalar value is always the same.
The Smokeview shows the slice at the nearest cell boundary. Let’s say
z cell boundaries are at z=1, 2, 3, etc and the slice is at z=1.4. The
smokview would represent this as the z slice at z=1 showing the values
of cells between z=1 and z=2.
1a) Is my explanation above correct?
1b) What is the temperature when the slice is placed between two
cells; is the temperature the average of the two neighbouring cells?

2) When looking at the vector slices it seems that the velocity of
each cell is described with 8 different velocities (one on each corner
of the cell). I was wondering how these velocities are calculated; are
they the average of the four neighbouring cells?
I always thought that the velocity is calculated at the faces of two
cells and not the corners of four cells as it appears on the
Smokeview?

I would really appreciate any comments or alternatively the reference
to the literature where I can find the explanation.

Andrej

[Kevin]

In FDS, the temperature, and all other scalars, are represented at
cell centers. The velocity components are represented at the
appropriate cell face. For example, the u component of velocity lies
at the forward and backward facing faces in the x direction. However,
smokeview wants all data to be interpolated to cell corners. That is
why when you look at flow vectors with "g" for grid turned on in
Smokeview, you see the vectors pinned to the cell corners. The three
velocity components are averaged using the 4 adjacent cell faces. The
scalar value uses 8 adjacent cell centers.

[Randy McDermott]

FYI...

There is a new option to view cell-centered SCALAR data in SMV (use
latest FDS and SMV).

First, on the SLCF line add CELL_CENTERED=.TRUE., for example,

&SLCF PBY=0, QUANTITY='TEMPERATURE', CELL_CENTERED=.TRUE./

Then, in SMV, Alt-Y toggles between uniform cell and interpolated cell
view.

[Apollo]

May I know if this command applies to Plot3D as well?

> > > Andrej- Hide quoted text -
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[Randy McDermott]

Apollo:

At the moment it only works for non-vector SLCF files.

Cheers,
Randy