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May 29, 2013, 05:04 
salam

#41 
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tehran
Join Date: May 2013
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hi amir .can i ask u about sth about b.c with udf


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

#42 
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Yunusrulz
Join Date: Apr 2012
Posts: 10
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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, 05:58 
Velocity inlet UDF in fluent

#43 
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Akshay Khadse
Join Date: Sep 2013
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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 
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Srivathsan N
Join Date: Jan 2013
Location: India
Posts: 101
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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, 11:03 
Periodic BC DDPM, UDF

#45 
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Rupesh Verma
Join Date: Jun 2013
Posts: 64
Rep Power: 6 
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 
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Keyu Dhingani
Join Date: Dec 2015
Location: San Diego, CA
Posts: 3
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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
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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 
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Rupesh Verma
Join Date: Jun 2013
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Dear
u r right.. 

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

#49 
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mm
Join Date: May 2016
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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 
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Code:
else if (1300.0 < t && t <= 1500.0 ) Code:
else if ((1300.0 < t) && (t <= 1500.0 )) 

January 25, 2017, 03:16 
Sinus velocity

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

January 25, 2017, 03:47 

#52 
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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, 23:39 
Sinus velocity

#53 
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milad
Join Date: Jan 2017
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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, 03:56 

#54 
Senior Member
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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, 13:11 
how to use data from .csv file as inlet boundry condition

#55 
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hemant mittal
Join Date: Feb 2016
Posts: 19
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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, 05:08 
radial_velocity

#56  
New Member
SAIF MASOOD
Join Date: Sep 2016
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Quote:
fluentp1102000.jpg t.jpg 

February 11, 2017, 10:54 
Error message : output pipe has been closed

#57 
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Thomas henderson
Join Date: Feb 2017
Posts: 3
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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, 05:29 

#58 
Senior Member
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Which one is "this UDF"?


February 13, 2017, 05:50 
Udf

#59 
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Thomas henderson
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February 14, 2017, 12:45 
Syntax error

#60 
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Thomas henderson
Join Date: Feb 2017
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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? 

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