Pressure coefficients 1

[Robert000]

Hi all,

I´m modelling a simple cube with edge 0.5 in
Flotran. The boundary is a cube too with edge 2.0.
The small cube is situated in the center of the
boundary. In the inlet side one velocity is given,
other velocities are 0,outlet side pressure is zero.
In the solution I get succesfully the velocity of
air. Element what I use is Fluid 142.

But with this form of solution it isn´t
possible to get pressure coefficient, or pressure
in directions X,Y,Z. How can I get them?

Our buiding standards establish pressure coefficient
0,8 from the pressure side, 0,6 from the opposite side.

So I would like to reach these values.

Thanks,

Robert

 

[meshparts]

Hi Robert,

what are the pressure coefficients?

The pressure is a scalar (a number) so what do you mean by pressure in x,y, anz directions??

Regards
Alex

 

[Robert000]

The pressure coefficient is a relative number, which
we get by dividing the wind velocity in the selected
area with the dynamic wind velocity (which is
determined as 0.5*density*velocity^2).

Acing of wind force on area will generate these pressures.

The pressure on the front side of the cube
is not only the wind force on the front area, but the part
of the friction force on the top area is added.
If I can get these pressures, I can add or substract pressures (*area=forces)
in the same direction, and manually I can determine the
wind pressure coefficients.

I saw this item in the postprocessing-plot results-contour plot-DOF
solution - other fluid ...- pressure coefficients.

Maybe Ansys can determine these values, but I don´t know the way
how can I determine them.

The pressures in x,y,z directions were here too, but I´m not sure.

Robert

 

[meshparts]

Hi Robert,

thank you for your explanation!

The computation of the pressure coeficients must be in Ansys requested befor solving. You can do this by issuing:

FLDA,OUTP,PCOE,T

Regards
Alex

 

[Robert000]

YES, it works!

Could you tell me the interactive form of this command.

One more thing. I need to get forces in direcions X,Y,Z on elements.

Interactive form, where i find this:
Plot results - Contour plot - Element solution - Fluid
Force - X, Y ,Z directions

But I get Ansys warning:
Element forces are not avaliable to display.
The PLESOL command is ignored.

I think exist a method to activate this.

Thanks,

Robert

 

[meshparts]

Hi Robert,

There are many ways to activate the computation of pressure coeficients in the Ansys GUI:

Main Menu>Preprocessor>FLOTRAN Set Up>Additional Out>Print Controls
Main Menu>Preprocessor>FLOTRAN Set Up>Additional Out>Residual File
Main Menu>Preprocessor>FLOTRAN Set Up>Additional Out>RFL Out Derived
Main Menu>Preprocessor>FLOTRAN Set Up>Additional Out>RFL Prop Based
Main Menu>Preprocessor>FLOTRAN Set Up>Execution Ctrl
Main Menu>Solution>FLOTRAN Set Up>Additional Out>Print Controls
Main Menu>Solution>FLOTRAN Set Up>Additional Out>Residual File
Main Menu>Solution>FLOTRAN Set Up>Additional Out>RFL Out Derived
Main Menu>Solution>FLOTRAN Set Up>Additional Out>RFL Prop Based
Main Menu>Solution>FLOTRAN Set Up>Execution Ctrl

Regarding the plot of fluid "force": some items are not supported by PowerGraphics, so you must issue:

/graphics,full

or in the ansys GUI:

Utility Menu>PlotCtrls>Style>Hidden-Line Options

Regards
Alex

 

[Robert000]

Thanks Alex.

I know that the element solution is not
suported by PowerGraphics, but after turning
off I don´t get the solution of forces on elements.

Here are my Hidden line options:
-window 1
-Q-slice Zbuffer
-working plane
-gouraud
-displayed
-full model
-replot.


Main Menu>Preprocessor>FLOTRAN Set Up>Additional Out>RFL Out Derived -----> all checked
Main Menu>Preprocessor>FLOTRAN Set Up>Additional Out>RFL Prop Based -----> all checked

I think the problem might be in preprocessing, because
Ansys doesn´t solve forces on elements.

Robert

 

[meshparts]

Try this:

/post1
/graphics,full
esel,all
etab,fluidforcex,vf,x
pletab,fluidforcex

I hope it works...

 

[Robert000]

WARNINGS:

No element item tables are avaliable.
The PLETAB command is ignored.

Element forces are not avaliable.
The PLETAB command is ignored.

The velocity in preprocessor is given on areas.
ELIST works, ETlist - fluid142, nodal solution OK

Robert