force applied on a face

Forums code_saturne usage
1

Hi,

I want to calculate the forces applied by the fluid on a faces of turbine and display it in the “fields” menu, these forces are normally written in this form: (Force = Pressure / Face Surface), with (Face surface = 1.5 m2)

In the “usproj.f90” subroutine I modefied it as, (is this reasoning is right?)

 call getfbr('201', nlelt, lstelt)
  !==========
  do ilelt = 1, nlelt
    ifac = lstelt(ilelt)
    do ii = 1, ndim
     ! xfor(ii) = xfor(ii) + ra(iforbr + (ifac-1)*ndim + ii-1)
xfor(ii) = (ipr (iphas))/1.5d0
    enddo

  enddo
  if (irangp.ge.0) then
    call parrsm(ndim,xfor)
  endif
endif

Thank’s

2

…please nobody knows how can do to display the forces calculated in the menu ‘fields’ for visualized it

3

hi,

You already have a quantity called ‘efforts’ in the postprocessing files. Anyway, if you want to have an action on the postprocessing, modify the usvpst routine.

in usproj, (see REFERENCE), use the keyword forbr to get directly the whole force (pressure, viscosity, turbulent energy) applied on your face.

As already explain in older post,

 call getfbr('12', nlelt, lstelt)
  !==========

  do ilelt = 1, nlelt

    ifac = lstelt(ilelt)

    do ii = 1, ndim
      xfor(ii) = xfor(ii) + forbr(ii, ifac)
    enddo

  enddo

here you have an example to do it,

don’t forget to look in the old forum section :wink:

4

Thank’s for your help,

Please could you explain the line in the code

xfor(ii) = xfor(ii) + forbr(ii, ifac)

is this relation represents the equivalent of (F=P/S)?

Is “xfor(ii)” represents the “effort”, what it means?

because I had written

xfor(ii) = (ipr (iphas))/1.5d0

, (ipr (iphas): pressure and 1.5 =Surface!!

Thank’s

5

Be careful with the dimension of the force. basically F=P*S

iforbr(X,Y) is an array calculated by saturne during the simulation and contain the 3 contributions explained before. It is of P*S dimension (N). X stand for the three coordinates (x,y,z). Y stands for the face number.

With the code I sent you, you simply do a sum on the forces applied on each faces of you BF(walltype). after this sum, you get :
xfor(1) = Fx
xfor(2) = Fy
xfor(3) = Fz

in

 call getfbr('201', nlelt, lstelt)

be sure 201 is the name of your wall.
:slight_smile:

6

Thank’s mercierg :slight_smile: