function [k, lambda] = linwavNum( T,d )
%LINWAVNUM finds the wave number of a wave with given period, T based on
%linear wave dispersion
%Input:
% d=h - [m] water depth (good to separate h from capital H if converting to other code language)
% T   - [s] wave period
%Output:
% k      - [-] wave number
% lambda - [m] wave length

g=9.81;
% Manual version how you do it by hand
% -wave dispersion to get wave number:
    omega=2*pi.*1./T;
    lambda=10; %first guess of wavelength, 10m
    k0=2*pi./lambda; %initial wave no., k
    conv=1; %initial value of convergence criterion (i.e. not met)
    while conv>0.001
        k=omega.^2./(g.*tanh(k0.*d));
        conv=abs(k-k0);
        k0=k; %update initial guess of k
        lambda=2*pi./k;
    end
end

% How to do it with function:
%f=@(lambda)g/2/pi*T^2*tanh(2*pi*h/lambda)-lambda;
%lambda=fzero(f,50);
%k=2*pi/lambda