pressure2surfaceelevzcross

[Eta, t] = pressure2surfaceelevzcross(P, fs, h, heightfrombed, Kpmin, kCalcMethod, Rho, dispout)

Description

Calculate water surface elevation time series from water pressure time series 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

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));
[Eta,t]=pressure2surfaceelevzcross(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.