Howdy all,

I just started programming some 1 days ago, I have the program complete except for the following problem-- iteration. I consider myself pretty engineering savy when it comes to Excel and have created a spreadsheet to calculate this already, but I would like to create a simple program to do it as well.

Just as a reference my Excel formula (modified for my C++ names instead of cells)is:

Code:

=IF(re>4000,(1/(-2*LOG(rrough/3.7 + 2.51/(rnum*SQRT(**SAMECELL**+1E-300))))^2),"0")
This code uses iteration and circular references within Excel to get a value to 1-E6 accuracy or 1000 iterations.

For those unfamiliar, the equation deals with friction loss through a pipe and outputs a friction factor to then be used in a pressure drop calculation. All of the required values are already either inputted or calculated. The problem is the same factor on both sides of the equation (f), see below.

The original equation is:

Code:

1/sqrt(f) = -2 * log10((e/3.7D) + ((2.51/Re*sqrt(f))))

Since my experience in C++ is lacking I was looking for someone to "show me the way," I am not used to doing math the way C++ handles it. I currently have most of the pieces defined, __but I know I do not have this setup correctly__.

Code:

//TURBULENT
if (rnum > 4000) {
t1 = 1
t2 = -2
t3 = log
t4 = rrough
t5 = 3.7
t6 = 2.51
t7 = rnum
t8 =
t9 =
tpfc =
cout<< "TURBULENT (RE > 4000)\n";
cout<<"\n";
cout<< "PIPE FRICTION COEFFICIENT (F=): \n";
cout<< tpfc << endl;
}

I think I would limit the program to 500 iterations and/or 1-E6 accuracy. If I can provide anymore detail I will.

Regards,

McJ