how to fit a correlation to meassured data in excel
how to fit a correlation to meassured data in excel
(OP)
In the attached excel sheet (interpolation.xls) measured friction factor data are shown as a function of Reynolds. The data are for different packing densities. 30 = lowest packing 80 = highest packing.
As it can be seen the values are strongly decreasing with higher Reynolds number.
Applying the excel trend lines does not give a good fit.
The power function fits well until a Reynolds number of 100 but for higher values I can not find a suitable fit.
Can anyone propose a software package which is able to apply trendlines for such kind of curves.
What kind of mathematical equation would fit the data?
Ideally a two dimensial function which gives
f = f(reynolds; packing density)
Any sugestion apreciated
As it can be seen the values are strongly decreasing with higher Reynolds number.
Applying the excel trend lines does not give a good fit.
The power function fits well until a Reynolds number of 100 but for higher values I can not find a suitable fit.
Can anyone propose a software package which is able to apply trendlines for such kind of curves.
What kind of mathematical equation would fit the data?
Ideally a two dimensial function which gives
f = f(reynolds; packing density)
Any sugestion apreciated
RE: how to fit a correlation to meassured data in excel
RE: how to fit a correlation to meassured data in excel
Having said that I rather think your difficulty is not so much in getting the shape vs Re, your packing density effect looks far more non linear on the log-log curve.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: how to fit a correlation to meassured data in excel
Orenda
RE: how to fit a correlation to meassured data in excel
corus
RE: how to fit a correlation to meassured data in excel
As Corus says a quadratic of log(Re) seems to be a reasonable fit.
However the error plot of what I have left is extremely complex, are those real data points?
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.