×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Pressure coefficients

Pressure coefficients

Pressure coefficients

(OP)
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


RE: Pressure coefficients

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

RE: Pressure coefficients

(OP)
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

RE: Pressure coefficients

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:

CODE

FLDA,OUTP,PCOE,T

Regards
Alex

RE: Pressure coefficients

(OP)
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

RE: Pressure coefficients

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:

CODE

/graphics,full

or in the ansys GUI:

Utility Menu>PlotCtrls>Style>Hidden-Line Options

Regards
Alex



RE: Pressure coefficients

(OP)
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


RE: Pressure coefficients

Try this:

CODE

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

I hope it works...

RE: Pressure coefficients

(OP)
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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources