guido_88
Guest
I would like to set an oscillation on fluent (sinusoidal for example).I should use the custom field functions command but I can't,you know how to make examples?
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giufranco
Guest
Hi.
I don't understand what you want to do.
If, as I imagine, you intend to have a boundary condition with an oscillating magnitude (e.g. sinusoidale) you must use the udfs, which are documented very well in the fluent manual.
try to follow the directions in the guide!
Good job!
I don't understand what you want to do.
If, as I imagine, you intend to have a boundary condition with an oscillating magnitude (e.g. sinusoidale) you must use the udfs, which are documented very well in the fluent manual.
try to follow the directions in the guide!
Good job!
guido_88
Guest
practically my problem is that instead of a speed in x,y and z components I have to set a sinusoidal speed but also udf I did not find much
giufranco
Guest
Hi, I drive.
setting a variable speed profile in fluent is done through those that are the udf (user defined functions). you can change the speed module according to any size. I guess in your case, you want to change the speed over time.
The code lines below refer precisely to this case: the speed set on your boundary condition varies depending on the time (which in our case is scanned by the time step(current_time)), of course this is only possible if you are analyzing a transitory.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
#includes "udf.h"
define_profile(vel_sinusoidale, thread position,)
(')
face_t f;
real t = current_time;
begin_f_loop(f, thread)
(')
f_profile(f, thread, position) = sin(t) ;
?
end_f_loop(f, thread)
?
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
said this, follow these steps:
1) Creates a text file with the code I mentioned above
2) when you are in fluent go to define->user-defined->functions->interpreted.. .
3) at this point "browsa" the text file just created.
4) press the "interpreted" button
5) at this point in the location where the text file is located, a "udfconfig" file will be created
6) go to the boundary conditions, and at the point where you can specify the value, along with "constant", you will find the newly created sine condition.
Hello and good work!
a tip: Find what I told you on the manual, it helps you to keep an eye on where to look for things. :mixed:
setting a variable speed profile in fluent is done through those that are the udf (user defined functions). you can change the speed module according to any size. I guess in your case, you want to change the speed over time.
The code lines below refer precisely to this case: the speed set on your boundary condition varies depending on the time (which in our case is scanned by the time step(current_time)), of course this is only possible if you are analyzing a transitory.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
#includes "udf.h"
define_profile(vel_sinusoidale, thread position,)
(')
face_t f;
real t = current_time;
begin_f_loop(f, thread)
(')
f_profile(f, thread, position) = sin(t) ;
?
end_f_loop(f, thread)
?
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
said this, follow these steps:
1) Creates a text file with the code I mentioned above
2) when you are in fluent go to define->user-defined->functions->interpreted.. .
3) at this point "browsa" the text file just created.
4) press the "interpreted" button
5) at this point in the location where the text file is located, a "udfconfig" file will be created
6) go to the boundary conditions, and at the point where you can specify the value, along with "constant", you will find the newly created sine condition.
Hello and good work!
a tip: Find what I told you on the manual, it helps you to keep an eye on where to look for things. :mixed:
guido_88
Guest
Thank you very much, without your help I would not have succeeded because I am not able to write in c. at this point I take advantage of it and ask you: if besides the sinusoidal oscillation I want to set a mach of 0.3 I just have to write 102.15+ sin(t) instead of simply sin(t) in what you wrote me or have to change something else? (102.15 because the vel of the sound at the sea level
giufranco
Guest
dear guide,
I would gladly help you, but you should be a little more precise in formulating the question.
When you say:
"if besides the sinusoidal oscillation I want to set a 0.3 mach just write 102.15+ sin(t) instead of simply sin(t)"
I don't understand what you're doing. you want to set a 0.3 mach on a boundary condition, and tell me you want to write 102.15 + sin(t).... I don't understand!
However, if you want to give the value of sin(t) an offset of 102.15, you can definitely do this.
I forgot... the theory of gasdynamics says that the speed of sound is given by the formula:
(krt)^0.5
where (for the air): - K=1.4
- R=287 [J/kgK]- to=293 [K] (temperature of 20 degrees centigrade)
and I get a speed of sound c=343 [m/s] other than 102.15 (measuring unit? )
Bye!
I would gladly help you, but you should be a little more precise in formulating the question.
When you say:
"if besides the sinusoidal oscillation I want to set a 0.3 mach just write 102.15+ sin(t) instead of simply sin(t)"
I don't understand what you're doing. you want to set a 0.3 mach on a boundary condition, and tell me you want to write 102.15 + sin(t).... I don't understand!
However, if you want to give the value of sin(t) an offset of 102.15, you can definitely do this.
I forgot... the theory of gasdynamics says that the speed of sound is given by the formula:
(krt)^0.5
where (for the air): - K=1.4
- R=287 [J/kgK]- to=293 [K] (temperature of 20 degrees centigrade)
and I get a speed of sound c=343 [m/s] other than 102.15 (measuring unit? )
Bye!
guido_88
Guest
You're right. I wasn't happy. then for a t of 15° c the v of sound at sea level is 340.5 m/s that multiplied by the desired mach 0.3 gives as a result 102.15 m/s. I thank you for the explanation but I attend the cdl in aerospace engineering so something I know:wink: My problem is the settings to give to the program of which I am not an expert. My problem is basically having an oscillating flow that has a 0.3 mach