- **CFX**
(*http://www.cfd-online.com/Forums/cfx/*)

- - **how to plot relative velocity on a plane in POST CFX**
(*http://www.cfd-online.com/Forums/cfx/66002-how-plot-relative-velocity-plane-post-cfx.html*)

how to plot relative velocity on a plane in POST CFXHi,
In my case, a water filled cylindrical domain and its surrounding surface was setup as wall, which rotates at a certain speed, my question is how I can plot the velocity profile(radial, tangential, axial component) relative to the wall in the chart viewer. Can anyone help me with it please?thanks. Harry |

Hi,
I assume you did not use a rotating frame of reference - if you did you will have variables in both the stationary and rotating frame of reference in the output file by default. If it is a stationary frame of reference simulation you will have to generate the rotating frame of reference by generating a vector field (in the variables tab) which is the velocity in the stationary frame of reference plus the component to convert it to the rotating frame. This should be simply r x omega (where "x" means the vector cross product) Glenn Horrocks |

HI, Glenn,
Thanks for your reply. Could you please tell me how to specify a rotating frame of reference in Pre-CFX? I tried to find it in tutorial, but it didn't help me a lot.Thanks in advance. |

Hi Glenn,
Do you use domain motion in the basic setting tab of domain details in PRE CFX to specify rotating frame of reference(RFR)? I tried it, but I didn't find the variables of velocity in both stationary and rotating frame of reference in the variable tab in POST CFX. Could you please help me with it? Thanks. |

Hi,
Do the rotor/stator example in the tutorials. It uses a RFR. Also note RFR is a license option which is not included in the basic CFX package. If you can't see it then you might not have that license option. Glenn Horrocks |

Hi Glenn,
Thanks, I got it. By the way, do you know how to express vector cross product in CFX? Thanks. Harry |

In what context? The CEL has a cross product function (I think) or you can write it out in full as a CEL expression. Is this what you mean?
Glenn Horrocks |

Hi Glenn,
Yes, that's it. But I didn't find vector cross product function in CEL, maybe it doesn't support vector arithmetic. I gotta to write it out. I'm trying to generate the rotating frame of reference by generating a vector field using my current simulations with stationary frame of reference. And this requires to use cross product. Do I need fortran to write it, any good suggestions? thanks. |

Hi,
CEL does not support vector variables, so make 3 CEL variables representing each component of the vector variable and then write out the cross product in terms of the components. A little messy but still pretty easy. Glenn Horrocks |

All times are GMT -4. The time now is 05:52. |