modelling a focused wave as free surface
 

Hi pals, I have a big headache with this question hope someone dealt with it once, I'm gonna explain as much as I can, here I go
My model is Navier Stokes solver, with a vof as treat the free surface, I tried to simulate a regular wave with a wave height, period and time lag as inputs, so far It worked :-)
Now the problem comes, I tried to simulate this time a focused wave (highly non-linear and noise from the experiment), therefore I decomposed the original signal from the experiment in its fourier coefficients using FFT, as I got bunch of insignificant coefficients (and put as my input parameters, wave height, wave period and time lag) I just used the most relevants, and then I used only 9 components instead of many I got, the outcomes looks not similar as the experiment, (see figures please), then I thought maybe I should added more fourier coefficients at the input , but then the solver just crash. Any opinion is greatly appreciate !!!