wavefrompressurezcross

[Hs, Ts, Hz, Tz, Hrms, H, T, Eta, t] = wavefrompressurezcross(P, fs, h, heightfrombed, Kpmin, kCalcMethod, Rho, dispout)

Description

Calculate wave properties from water pressure by using an upward zero crossing method

Inputs

P

Water pressure time series data in (N/m^2)

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)

Kpmin=0.15;

Minimum acceptable value for a pressure response factor

If Kpmin=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;
P=Eta.*9.81.*1000.*(cosh(k*hfrombed)/cosh(k*h));
[Hs,Ts,Hz,Tz,Hrms,H,T,Eta,t]=wavefrompressurezcross(P,fs,5,4,0.15,'beji',1025,'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.