
[Sponsors] 
(ask) how to create UDF for inlet velocity profile 

LinkBack  Thread Tools  Search this Thread  Display Modes 
May 29, 2013, 05:04 
salam

#41 
New Member
tehran
Join Date: May 2013
Posts: 4
Rep Power: 11 
hi amir .can i ask u about sth about b.c with udf


August 14, 2013, 12:05 
Defining TOP HAT VELOCITY profile

#42 
New Member
Yunusrulz
Join Date: Apr 2012
Posts: 10
Rep Power: 12 
I want to define a top hat velocity profile at my inlet. I dont know the code to define top hat velocity profile. does any body know it. Please answer.


January 14, 2014, 04:58 
Velocity inlet UDF in fluent

#43 
New Member
Akshay Khadse
Join Date: Sep 2013
Posts: 11
Rep Power: 10 
hi guys,
I want to use a user defined function for velocity inlet for following conditions: v_x = (2/3)*z for z = 0 to 30 v_x = 20 for z = 30 to 70 v_x = (200/3)(2/3)*z for z = 70 to 100 It is for 3D compressor cascade inlet. I do not know how to write such functions. Can anyone help me? 

July 9, 2014, 13:01 

#44 
Senior Member
Srivathsan N
Join Date: Jan 2013
Location: India
Posts: 101
Rep Power: 11 
Hello,
I have a 2D axisymmetric geometry where I want to impose a non uniform velocity field in the fluid region (not a boundary, but the internal field). I have the coordinates and the axial and radial velocity components from a previous simulation. How do I go about importing this into the current case. Also is there a better way to store the velocity value other than File > Export? Thanks in advance
__________________
Regards, Srivaths 

January 12, 2016, 10:03 
Periodic BC DDPM, UDF

#45 
Member
Rupesh Verma
Join Date: Jun 2013
Posts: 64
Rep Power: 11 
Dear Friend,
I am using, DDPM simulation using ANSYS 14.5, for a simple system. I used inlet as periodic and outlet as shadow in ANSYS for making it periodic but after making periodic I have no control on the inlet (I am unable to specify mass flow rate inlet), it is showing option to specify pressure gradient. Thanks for helping in advance!!! 

April 25, 2016, 18:41 
UDF for inlet y velocity 2D

#46 
New Member
Keyu Dhingani
Join Date: Dec 2015
Location: San Diego, CA
Posts: 3
Rep Power: 8 
Hi,
I have seen and used UDFs for the inlet x velocity, but what do I do to make a UDF for inlet y velocity. Here is the UDF that I used for inlet x velocity. [ #include "udf.h" #define umean 10.0 #define R 0.0005 DEFINE_PROFILE(inletxvelocity,t,i) { real x[ND_ND]; real y; face_t f; begin_f_loop(f,t) { F_CENTROID(x,f,t); y = x[1]; F_PROFILE(f,t,i) = (3./2.)*umean*(1pow((yR)/R,2)); } end_f_loop(f,t) } ] I tried replacing x with y and vice versa to hopefully get the ydirection velocity, but unsuccessful. Any suggestions here will be useful. Thanks, Keyu 

April 26, 2016, 04:58 

#47  
Senior Member
Bruno Machado
Join Date: May 2014
Posts: 271
Rep Power: 11 
Quote:
y = x[1]; If you want a velocity profile normal to the Y direction, you need to use the variation of the position in the X direction if 2D and X and/or Z direction if 3D. 

April 27, 2016, 11:09 

#48 
Member
Rupesh Verma
Join Date: Jun 2013
Posts: 64
Rep Power: 11 
Dear
u r right.. 

October 24, 2016, 04:51 
UDF for inlet temperature

#49 
New Member
mm
Join Date: May 2016
Posts: 24
Rep Power: 7 
Dear all
I have following UDF for inlet temperature, untill 1300s it takes correct values according to equation, but after 1300s values are higher and not accorrding to equation, like at 1301s it should have value of 405C but in simulation inlet temperature is 621C. I could not find the error in my UDF after lot of try. please check this and guide me #include"udf.h" DEFINE_PROFILE(inlet_temperature,thread,position ) { face_t f; begin_f_loop(f,thread) { real t = RP_Get_Real("flowtime"); if (t <=1300.0 ) { F_PROFILE(f,thread,position) = 379.13 + 0.0005*t; } else if (1300.0 < t && t <= 1500.0 ) { F_PROFILE(f,thread,position)= 1.04289036878969*pow(10,10)*pow(t,6.0)+ 8.86126436853789*pow(10,7)*pow(t,5.0)3.13621260398811*pow(10,3)*pow(t,4.0)+5.91804640375908*pow(t,3.0)6.27969461279651*pow(10,3)*pow(t,2.0)+ 3.55273415252714*pow(10,6)*t  8.37223405676245*pow(10,8); } else { F_PROFILE(f,thread,position) = 9.51538261322402*pow(10,23)*pow(t,6) + 8.26192751387975*pow(10,18)*pow(t,5)2.85237398505875*pow(10,13)*pow(t,4)+4.97518353700886*pow(10,9)*pow(t,3)4.58733775886876*pow(10,5)*pow(t,2)+ 2.10251137071757*pow(10,1)*t +3.57252192344954*pow(10,2); } } end_f_loop(f,thread) } 

October 24, 2016, 10:36 

#50 
Senior Member
Join Date: Nov 2013
Posts: 1,965
Rep Power: 24 
Code:
else if (1300.0 < t && t <= 1500.0 ) Code:
else if ((1300.0 < t) && (t <= 1500.0 )) 

January 25, 2017, 02:16 
Sinus velocity

#51 
New Member
milad
Join Date: Jan 2017
Posts: 4
Rep Power: 7 
Hello
I have a question How write( V=Asinwt) in fluent(udf) Please help me Thank you 

January 25, 2017, 02:47 

#52 
Senior Member
Join Date: Nov 2013
Posts: 1,965
Rep Power: 24 
If you use this UDF:
Code:
Message("V=Asinwt"); This is almost surely not what you want, but I can not guess what you really want. You should explain better what you want the UDF to do. Edit: let me be a little bit more helpful, after drinking coffee. If A, w and t are defined variables, and you want to put the result in V, the way to put that in a UDF is: Code:
V = A*sin(w*t); 

January 25, 2017, 22:39 
Sinus velocity

#53 
New Member
milad
Join Date: Jan 2017
Posts: 4
Rep Power: 7 
Thank you for the answers you have given me. I want to examine the impact of heat transfer in an oscillating jet, for sinusoidal input speed jet was
u = Asinwt The A (Initial velocity), w (period), t (time) But I do not know how to code the program is written udf 

January 26, 2017, 02:56 

#54 
Senior Member
Join Date: Nov 2013
Posts: 1,965
Rep Power: 24 
Look for a UDF that does something similar, and change it.
There are UDFs mentioned in the messages above that do something similar... Read them! 

January 28, 2017, 12:11 
how to use data from .csv file as inlet boundry condition

#55 
New Member
hemant mittal
Join Date: Feb 2016
Posts: 21
Rep Power: 8 
hello every one
i have data file generated from matlab program which contains fluctuating velocity for atmospheric boundary layer so please guide me how can i use this file as inlet boundary condition thanks and regards 

January 30, 2017, 04:08 
radial_velocity

#56  
New Member
SAIF MASOOD
Join Date: Sep 2016
Posts: 2
Rep Power: 0 
Quote:
fluentp1102000.jpg t.jpg 

February 11, 2017, 09:54 
Error message : output pipe has been closed

#57 
New Member
Thomas henderson
Join Date: Feb 2017
Posts: 3
Rep Power: 7 
Hi there,
I have tried to implement this UDF in ansys fluent however it is resulting in an error stating : " output pipe has been closed " Any ideas why this might be? 

February 13, 2017, 04:29 

#58 
Senior Member
Join Date: Nov 2013
Posts: 1,965
Rep Power: 24 
Which one is "this UDF"?


February 13, 2017, 04:50 
Udf

#59 
New Member
Thomas henderson
Join Date: Feb 2017
Posts: 3
Rep Power: 7 

February 14, 2017, 11:45 
Syntax error

#60 
New Member
Thomas henderson
Join Date: Feb 2017
Posts: 3
Rep Power: 7 
There is a syntax error in the line :
DEFINE_PROFILE(unsteady_velocity, thread, position) However this is similar to other examples I have seen. Any ideas why this may be? 

Thread Tools  Search this Thread 
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
UDF problems  velocity profile  Oli  Fluent UDF and Scheme Programming  6  October 24, 2016 10:38 
How to create nonuniform velocity profile in FLUENT?  pankaj  FLUENT  7  October 24, 2016 04:52 
udf for velocity profile in a geometry having two inlets  shubham208011  Fluent UDF and Scheme Programming  0  April 6, 2009 15:13 
UDF velocity and temperature  Raj  FLUENT  3  February 1, 2009 18:29 
UDF velocity profile at nodes  Emad  FLUENT  2  January 29, 2009 06:35 