Mean wave period

A procedure for empirical computation of significant wave height, mean wave period and wavelength, and an empirical energy spectrum of wind waves is introduced. 

Mean wave period (Tm) is average wave period. In many cases it is identical to... 

P °- /cot a for surging waves ( rn > 2.5), is the Iribarren number based on mean wave period and P is the notional structure permeability. Later, van der Meer and Janssen provided a simpler expression for the runup distribution at dikes the shape parameter is constant k2 = 2, i.e., the distribution is Rayleighian, and the location parameter is proportional to incident wave height k = 0.81 7 /f /f3 min(76 op, 2) Hgi. The Rayleigh distribution fits in any case rather well the distribution of runup. 

Percentage of occurrence of wave height (m) in rows versus mean wave period (s) in columns... 

In the ripple method a series of ripples is caused to travel over the surface of the liquid, the ripples being formed by means of an an electrically driven tuning fork dipping into the liquid. If viewed by means of intermittent illumination conveniently arranged by periodic interception of the light by interposition of a screen attached to one limb of the fork, apparently stationary waves may be observed and the mean wave length readily determined. 

In these equations, Ej represents the electrode potential during the yth half period, 5 the fraction of the square-wave half period at which the current is measured, / is the square-wave frequency (equal to the inverse of the square-wave period), and the other symbols have their customary meaning. As long as the square-wave amplitude, Esw, is lower than 0.5RT jnF—a condition easily accomplished under the usual experimental conditions—the differential sum of the currents flowing during the anodic and cathodic half cycles can be represented by an expression such as [184]... 

The authors of [50] regarded the eddies as manifestations of Rossby waves modified by the bottom topography. The parameters of similar waves obtained from the data of altimeter observations (see Sect. 2.4), except for the period, are close to the model values. The annual wave period, which prevails in the observations, is absent in the model this is related to the forcing of the model BSGC by a constant mean annual wind field. 

It is apparent that as the momentum p increases, the finite difference spectrum deviates more and more from the correct value. It is usually assumed that acceptable accuracy with the FD method is obtained when at least 10 points are used per wave period. This means also using 10 points per unit volume in phase space. The finite difference algorithms are based on a local polynomial approximation of the wave function and therefore the convergence of the method follows a power law of the form (Aq)n, where n is the order of the finite difference approximation. This semilocal description leads to a poor spectral representation of the kinetic energy operator, which will be true as well, for other banded representations of the kinetic energy operator such as the... 

The wave energy is relatively large in summer, the peak value of frequency spectrum is 1.00 mVHz, peak-period corresponds to 8 s, and it means the wave has the characteristic of big wave height and short wave period. 

The frequency spectrum peak value in spring, autumn and winter are all below 0.02 mV Hz, corresponding spectrum peak period between 11 13 s, and it means the wave has the characteristic of small wave height and long wave period. 

SWV is characterized by four parameters square wave period, t, pulse width, tp = r/2, step height, AEg, and pulse height, AEsw The pulse width is related to the square wave frequency, / = ll 2tp) and as the staircase step at the beginning of each cycle is AEg, it means that the effective scan rate is u = A s/2fp = fAEg. 

In calculating the maximum wave periods a value of 1.2 times the significant wave period is normally used for deep water for calculation of the minimum wave period, the limitation of wave steepness in shallow water is appropriate. The significant wave period may be taken to be approximately the same as the average wave period. The peak period of the waves in shallow water can be up to twice the mean period. 

Standard terminology defines the water level in the absence of wave effects as still water level, whereas wave setup will cause a departure from the still water level and this water level including the effects of the waves is the mean water level. As implied, the mean water level is determined as the average of the fluctuating water level over a suitable time frame usually taken as a number of multiples of the short wave period, say the spectral peak. In considering wave setup, often the location of interest is that of the maximum wave setup at the shoreline. This raises the question of whether wave setup is defined at elevations above the maximum rundown, say on the beach face where the water is present over only a portion of the wave period. Since wave setup is defined as the mean water level, over what period should the water surface be averaged on the beach face which is wetted over only a portion of the wave period If the time average is over only the portion of the period that water is present, in the upper limit, the maximum setup will be the maximum runup. For purposes here, wave setup will usually be defined only for conditions where water is present over a full wave period. 

The input parameters are wave height, wave period (either spectral period Tm-1,0 or peak period Tp), wave obliquity, water level (with respect to the same level as used for the structure geometry), and finally, number of waves (derived from the storm duration and mean period) for the calculation of overtopping volumes, etc. Fig. 14.16 gives the input file. 

The passage sea state IS characterized, in deepwater, by a narrow band Jonswap spectrum with significant wave height Hg = 3.8 m, peak period Tp = 9 s, and shape factor 7 = 3.3. The mean sea state duration is = 1.8 h. As Tc [Pg.945]

Climate dataset generation The climate dataset for simulation comprises of a synthetic wind speed, significant wave height and wave period time series. These are generated using a Multivariate Auto-Regressive (MAR) model, shown in Equation 1, normalised by the mean of the data p where is the simulated wind speed at time-step t, n is the number of variables, is a variable state vector, is a matrix of the MAR model coefficients and is a noise vector with mean zero and covariance matrix of the data, order p (Box and Jenkins, 1970). 

Fig.l2.15a-c. Vibrational motion of the I2 molecule, (a) Potential curve of the ground state, the excited state reached by the pump laser and higher excited state of I2 populated by the probe laser. The probe laser-induced fluorescence is used to monitor the vibratinal motion of the I2 molecule in the state depicted by the probability. (R) in a superpositional vibrational levels v. (b) Probe-laser-induced fluorescence intensity as a function of the delay time between probe pulse and pump pulse, showing the oscillation of the wave packet. The short period gives the mean vibrational period, the long one represents the recurrence time, (c) Fourier spectrum of (b) [12.55]... 

In this discussion we define the x direction to be the direction of propagation of the light waves. This means that the yz plane contains the oscillating electrical and magnetic fields which carry the energy of the radiation. Only the electric field concerns us in scattering. Since the oscillation is periodic in both time t and location x, the electric field can be represented by the equation... 

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