
[Sponsors] 
Can I define grids motion as a time functions 

LinkBack  Thread Tools  Search this Thread  Display Modes 
March 28, 2001, 06:22 
Can I define grids motion as a time functions

#1 
Guest
Posts: n/a

Dear all
The complete title is 'Can I define grids motion as a time functions in a command file?' In CFX4, I think it not a easy job to use USRGRD for the definition of grids motion. I saw the desk calculator mode in command file today.I wondered if it can help me define grids motion to be a time function immediately in command file. To give my comcept, I give the commmand file codes below: >>GRID MOTION PARAMETERS #CALC ALPHA = OMEGAT ** 2.0 / (4.0 * 3.41592); OMEGA = ALPHA * TIME; #ENDCALC /* THE VARIABLE 'TIME' IS TIME VALUE OF TRANSIENT FLOW FIELD */ BLOCK NAMES 'BLOCKNUMBER1','BLOCKNUMBER2' POSITION OF MATION AXIS 3 * 0.0 DIRCETION VECTOR OF MOTION AXIS 1.0 0.0 0.0 ROTATION SPEED #OMEGA >>END I make grids 'BLOCKNUMBER1' and 'BLOCKNUMBER2' rotate about the axis defined by (0,0,0) and (1,0,0). The rotation speed is a linear time function. The rotation speed is 0 at t = 0 and OMEGAT when t = T. What's more the rotation acceleration is constant. Is it all right? If it's not, pls. tell me what is not correct. Thx. P.s. Is there someone tell me how to use CALL DEF('.spch.') and CALL DEF('.indc.') 

March 28, 2001, 16:01 
Re: Can I define grids motion as a time functions

#2 
Guest
Posts: n/a

Darcy,
 My calculator says pi is equal to 3.141592654 and not 3.41592. I used the following code for rotation of block1 and 2 with  3 Hz;  360 degrees in 56 steps  total number of steps is Nstep = 672  This makes 672/56=12 rotations  12 rotations at 3 Hz is 4 seconds in the real world. #CALC PI = 4.0*ATAN(1.0); DEGREE = PI/180.0; FREQ = 3.0; OMEGA = 2.0 * PI * FREQ; /* rad/s */ ANGLE = 360/56; RSTEP = ANGLE * DEGREE; DT = RSTEP /((2.0*PI) * FREQ); NSTAP = 672; #ENDCALC . . . >>GRID MOTION PARAMETERS MOTION AROUND X AXIS ROTATION SPEED #OMEGA BLOCK NAMES 'BLOCK1' 'BLOCK2' >>TRANSIENT PARAMETERS :>FIXED TIME STEPPING TIME STEPS #NSTAP * #DT Hope this helps, GertJan 

March 29, 2001, 01:47 
Re: Can I define grids motion as a time functions

#3 
Guest
Posts: n/a

Thank you, GertJan
I forgot use atan() to determine pi and typed it by hands in command file. Additionally I gave a wrong title. This time I give a new title as 'Can I define the speed of grid motion as a time function in command file' I tried yesterday and failed to archive my goal. I hope somebody can tell me if it is possible. Darcy 

March 29, 2001, 08:34 
Re: Can I define grids motion as a time functions

#4 
Guest
Posts: n/a

Darcy,
I think it is not possible to vary the speed in the command file. You have to do this in USRGRD which is not too difficult, depending on your geometry, but you have to invest some time in it. GertJan 

March 29, 2001, 21:14 
Re: Can I define grids motion as a time functions

#5 
Guest
Posts: n/a

Yes, I think so.
Thank u. Darcy 

Thread Tools  Search this Thread 
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Multiple floating objects  CKH  OpenFOAM Running, Solving & CFD  14  February 20, 2019 09:08 
Upgraded from Karmic Koala 9.10 to Lucid Lynx10.04.3  bookie56  OpenFOAM Installation  8  August 13, 2011 04:03 
IcoFoam parallel woes  msrinath80  OpenFOAM Running, Solving & CFD  9  July 22, 2007 02:58 
AMG versus ICCG  msrinath80  OpenFOAM Running, Solving & CFD  2  November 7, 2006 15:15 
REAL GAS UDF  brian  FLUENT  6  September 11, 2006 08:23 