wavefromvelocityzcross#

[Hs, Ts, Hz, Tz, Hrms, H, T, Eta, t] = wavefromvelocityzcross(Ux, Uy, fs, h, heightfrombed, Kuvmin, kCalcMethod, dispout)

Description#

Calculate wave properties from wave orbital velocity by using an upward zero crossing method

Inputs#

Ux

Wave horizontal orbital velocity data in x direction in (m/s)

Uy

Wave horizontal orbital velocity data in y direction in (m/s)

fs

Sampling frequency that data collected at in (Hz)

h

Water depth in (m)

heightfrombed=0;

Height from bed that data collected at in (m)

Kuvmin=0.15;
Minimum acceptable value for an orbital velocity converstion factor
If Kuvmin=0.15, it avoid wave amplification larger than 6 times (1/0.15)
kCalcMethod=’beji’;
Wave number calculation method
‘hunt’: Hunt (1979), ‘beji’: Beji (2013), ‘vatankhah’: Vatankhah and Aghashariatmadari (2013)
‘goda’: Goda (2010), ‘exact’: calculate exact value
Rho=1000;

Water density (kg/m^3)

dispout=’no’;

Define to display outputs or not (‘yes’: display, ‘no’: not display)

Outputs#

Hs

Significant Wave Height (m)

Ts

Significant Wave Period (second)

Hz

Zero Crossing Mean Wave Height (m)

Tz

Zero Crossing Mean Wave Period (second)

Hrms

Root Mean Square Wave Height (m)

H

Wave Height Data Series array (m)

T

Wave Period Data Series array (second)

Eta

Water surface elevation time series in (m)

t

Time (s)

Examples#

fs=2; %Sampling frequency
duration=1024; %Duration of the data
N=fs*duration; %Total number of points
df=fs/N; %Frequency difference
dt=1/fs; %Time difference, dt=1/fs
t(:,1)=linspace(0,duration-dt,N); %Time
Eta(:,1)=detrend(0.5.*cos(2*pi*0.2*t)+(-0.1+(0.1-(-0.1))).*rand(N,1));
hfrombed=4;
h=5;
k=0.2;
Ux=(pi/5).*(2.*Eta).*(cosh(k*hfrombed)/sinh(k*h));
Uy=0.2.*Ux;
[Hs,Ts,Hz,Tz,Hrms,H,T,Eta,t]=wavefromvelocityzcross(Ux,Uy,fs,5,4,0.15,'beji','yes');

References#

Beji, S. (2013). Improved explicit approximation of linear dispersion relationship for gravity waves. Coastal Engineering, 73, 11-12.

Goda, Y. (2010). Random seas and design of maritime structures. World scientific.

Hunt, J. N. (1979). Direct solution of wave dispersion equation. Journal of the Waterway Port Coastal and Ocean Division, 105(4), 457-459.

Vatankhah, A. R., & Aghashariatmadari, Z. (2013). Improved explicit approximation of linear dispersion relationship for gravity waves: A discussion. Coastal engineering, 78, 21-22.