[UDF] Relative coordinates in logarithmic velocity profile

m zahid · November 14, 2014, 20:47

hi, anybody know the difference between log and natural log in Fluent UDF. i go through many UDF , every one used log, instead of natural log (ln). if anybody know the answer please share.

thanks

pakk · November 16, 2014, 10:32

The difference is a factor 2.30258509299.
Can you be more specific with your question? If I google for "difference between log and natural log", I get many many websites which explain this difference. Doesn't that help you?

m zahid · November 16, 2014, 10:45

hi pakk, thanks for the answer. actually i want to know the difference with respect to the Fluent UDF. because i feel that,in fluent UDF, every where "log" is used instead of "ln". actually i want to make a UDF of "law of wall" given in this link below
http://en.wikipedia.org/wiki/Law_of_the_wall

that's why i was thinking that may be in fluent both are similar.
regards.

pakk · November 17, 2014, 03:14

UDFs in Fluent are written in the "c" programming language.

If you want to know what a function does in "c", you can look for example here.

From that website:

Quote:

log
double log (double x);
Compute natural logarithm
Returns the natural logarithm of x.

The natural logarithm is the base-e logarithm: the inverse of the natural exponential function (exp). For common (base-10) logarithms, see log10.

ashkan39t323 · February 23, 2015, 04:33

Hello,
I wonder if you find a solution for your work cause i have the same problem. architect and want to assign a velocity profile into the inlet.
help me please!!

tnx a lot

Fabio88 · July 13, 2017, 03:44

Hello,

I need to use a relative height for my velocity profile and I need to give this as input in my UDF. Does someone have experienced the same need and would like to share how he/she managed?

My domain is split in several sub-domains and therefore there are several face zones (patches) for inlet, ground etc..

Thanks,

Fabio

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November 14, 2014, 20:47	hi	#21
m zahid Member Qureshi M Z I Join Date: Sep 2013 Posts: 79 Rep Power: 12	hi, anybody know the difference between log and natural log in Fluent UDF. i go through many UDF , every one used log, instead of natural log (ln). if anybody know the answer please share. thanks

November 16, 2014, 10:32		#22
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	The difference is a factor 2.30258509299. Can you be more specific with your question? If I google for "difference between log and natural log", I get many many websites which explain this difference. Doesn't that help you?

November 16, 2014, 10:45	hi	#23
m zahid Member Qureshi M Z I Join Date: Sep 2013 Posts: 79 Rep Power: 12	hi pakk, thanks for the answer. actually i want to know the difference with respect to the Fluent UDF. because i feel that,in fluent UDF, every where "log" is used instead of "ln". actually i want to make a UDF of "law of wall" given in this link below http://en.wikipedia.org/wiki/Law_of_the_wall that's why i was thinking that may be in fluent both are similar. regards.

February 23, 2015, 04:33		#25
ashkan39t323 New Member achilles Join Date: Feb 2015 Location: paris Posts: 3 Rep Power: 11	Hello, I wonder if you find a solution for your work cause i have the same problem. architect and want to assign a velocity profile into the inlet. help me please!! tnx a lot

July 13, 2017, 03:44		#26
Fabio88 Member Fabio Malizia Join Date: May 2010 Location: Leuven (Belgium) Posts: 51 Rep Power: 15	Hello, I need to use a relative height for my velocity profile and I need to give this as input in my UDF. Does someone have experienced the same need and would like to share how he/she managed? My domain is split in several sub-domains and therefore there are several face zones (patches) for inlet, ground etc.. Thanks, Fabio