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(ask) how to create UDF for inlet velocity profile |
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#41 |
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tehran
Join Date: May 2013
Posts: 4
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hi amir .can i ask u about sth about b.c with udf
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#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.
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#43 |
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Akshay Khadse
Join Date: Sep 2013
Posts: 11
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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? |
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#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
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Regards, Srivaths |
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#45 |
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Rupesh Verma
Join Date: Jun 2013
Posts: 64
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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!!! |
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#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(inlet-x-velocity,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*(1-pow((y-R)/R,2)); } end_f_loop(f,t) } ] I tried replacing x with y and vice versa to hopefully get the y-direction velocity, but unsuccessful. Any suggestions here will be useful. Thanks, Keyu |
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#47 | |
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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. |
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#48 |
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Rupesh Verma
Join Date: Jun 2013
Posts: 64
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Dear
u r right.. |
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#49 |
New Member
mm
Join Date: May 2016
Posts: 24
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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("flow-time"); 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) } |
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#50 |
Senior Member
Join Date: Nov 2013
Posts: 1,965
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Code:
else if (1300.0 < t && t <= 1500.0 ) Code:
else if ((1300.0 < t) && (t <= 1500.0 )) |
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#51 |
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milad
Join Date: Jan 2017
Posts: 4
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Hello
I have a question How write( V=Asinwt) in fluent(udf) Please help me Thank you |
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#52 |
Senior Member
Join Date: Nov 2013
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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); |
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#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 |
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#54 |
Senior Member
Join Date: Nov 2013
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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! |
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#55 |
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hemant mittal
Join Date: Feb 2016
Posts: 21
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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 |
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#56 | |
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SAIF MASOOD
Join Date: Sep 2016
Posts: 2
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Quote:
fluentp1-1-02000.jpg t.jpg |
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#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? |
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#58 |
Senior Member
Join Date: Nov 2013
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Which one is "this UDF"?
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#59 |
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Thomas henderson
Join Date: Feb 2017
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#60 |
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Thomas henderson
Join Date: Feb 2017
Posts: 3
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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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