Help with DEFINE_GRID

Help with DEFINE_GRID_MOTION UDF

- December 20, 2019 at 4:09 pm
  
  kfouladi
  Subscriber
  
  Hi,
  
  I like to put a short flexible tube (initially in straight horizontal position) in to a wavy motion. I have been told the best way to do this is to use DEFINE_GRID_MOTION UDF and dynamic mesh. I have seen examples of such UDF but I am having a hard time to get started. I can use some help or a tutorial or a video. Any suggestions would be great. Thanks.
- December 20, 2019 at 4:49 pm
  
  Rob
  Ansys Employee
  
  There may be something on the Customer Portal (you should have access), there may also be videos with the 2019Rx online help. Otherwise it's the manual, and potentially YouTube.
- December 20, 2019 at 4:59 pm
  
  Konstantin
  Ansys Employee
  
  I'd like to add that Fluent documentation has a DEFINE_GRID_MOTION example which you can use as a template for your own implementation. Please Refer to Sec. 2.6.4. DEFINE_GRID_MOTION of Fluent's Customization manual - Creating and Using User Defined Functions.
- December 20, 2019 at 9:34 pm
  
  kfouladi
  Subscriber
  
  That's the problem. I can't find anything on the portal or internet to walk me through one. All I find is a few UDF examples.
- December 20, 2019 at 9:36 pm
  
  kfouladi
  Subscriber
  
  I could not find the Fluent's Customization manual - Creating and Using User Defined Functions either in the portal or outside. Do you have a link? I have a copy of Fluent 6.1 UDF manual.
- December 23, 2019 at 11:59 am
  
  Rob
  Ansys Employee
  
  If you click on "Help" in Fluent it'll take you to the manuals in R19 & 2019R versions: from there you can navigate to the Customisation Manual.
- December 23, 2019 at 4:37 pm
  
  kfouladi
  Subscriber
  
  Thanks. I just went there and unfortunately there is nothing new there. It is the same thing that was in Fluent 6.1 manual. I have several questions regarding the UDF example and I can't find anybody to ask specifically. For example,
  
  why is there "-5.0" in the sign equation sign = -5.0 * sin (26.178 * time); ?
  
  why is the origin at origin, =, 0.0, 0.0, 0.152
  
  I have a few more questions.
- December 24, 2019 at 11:04 am
  
  Rob
  Ansys Employee
  
  We can't be too specific on here given the rules we have to work to.
  
  The -5.0 will be related to motion/speed or the like. Origin will be dependent on the model.
- December 24, 2019 at 10:08 pm
  
  kfouladi
  Subscriber
  
  I think I figured it out the mystery behind -5.0. In the example given, there is -10.4 in the "Wx equation". In the UDF, -10.4 is replaced by -5.0 in the "sign equation" and 1/(square root (0.230)) in "omega equation". I am not sure why it has been split as such.

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