# NM402 Theory and Practice of Marine CFD

## Lab example two: numerical friction line

The aim here will be to reproduce the numerical friction line by fitting a curve to CFD data provided by students. The general form of the equation will be:

\[C_F=a/(\log_{10}(Re)+b)^c\]where \(Re = U\rho L/\mu\) is the Reynolds number, \(U\) is the free stream flow speed in \(m/s\), \(\rho = 997.561 kg/m^3\) is the water density, \(\mu = 8.8871\times10^{-4} Pa-s\) is the dynamic viscosity of water, and \(L = 1 m\) is the plate length. Our task will be to determine the coefficients \(a, b, c\) by using the MATLAB curve fitting toolbox. We will then decide on the name of the equation through a voting system.

Each student will use a different Reynolds number in the range \(10^5 < Re < 10^8\). The script below will provide the first layer thickness and free stream velocity for each case.