THEORETICAL MEAN WAVE RESISTANCE OF PRECURSOR SOLITON GENERATION IN TWO-LAYER FLOW

A new concept of pseudo mean wave resistance is introduced to find theoretical mean wave resistances of the precursor soliton generation in two-layer how over a localized topography at near-resonance in this paper. The pseudo mean wave resistance of the precursor soliton generation of two-layer how is determined in terms of the AfKdV equation. From the theoretical results it is shown that the theoretical mean wave resistance is equal to the pseudo mean wave resistance times 1/m(1), where m(1) is the coefficient of the fKdV equation. From the regional distribution of the energy of the precursor soliton generation at the resonant points, it is shown that ratios of the theoretical mean wave resistance and regional mean energy to the total mean energy are invariant constants, i.e. <(E)over circle (1)>/(E) over circle : <(E)over circle (2)>/(E) over circle: <(E)over circle (3)>(E) over circle :< D > /(E) over circle = (1/2) : (-1/2) : 1 : 1, in which <(E)over circle 1>,<(E)over circle (2)> and <(E)over circle (3)> are the mean energy of the generating regions of the precursor solitons, of the depression and of the trailing wavetrain at the resonant points respectively, (E) over circle and < D > are the total energy of the system and the theoretical mean wave resistance at the resonant points. A prediction of the theoretical mean wave resistances of two-layer how over the semicircular topography is carried out in terms of the theoretical results of the present paper. The comparison shows that the theoretical mean wave resistance is in good agreement with the numerical calculation.

Theoretical solution for wave diffraction by wedge or corner with arbitrary reflection characteristics

An exact analytic solution for wave diffraction by wedge or corner with arbitrary angle (rπ) and reflection coefficients (R0 and Rr) is presented in this paper. It is expressed in two forms-series and integral representations, corresponding recurrence relation and asymptotic expressions are also derived. The solution is simplified for some special cases of rπ. For Rr= R0,r= 1/N and Rr≠R0,r = 1/2N, the solution can be reduced to linear superpositions of incident and partially reflected waves, hence a nonlinear solution of forth order for this problem can be obtained by using the author's theory of nonlinear interaction among gravity surface waves. The given solution is related to inhomogeneous Robin boundary conditions, which include the Neumann boundary conditions usually accepted in wave diffraction theory.

A Theoretical Model for the Asymmetric Transmission of Powerful Acoustic Wave in Double-Layer Liquids

A theoretical model which couples the oscillation of cavitation bubbles with the equation of an acoustic wave is utilized to describe the sound fields in double-layer liquids, which can be used to realize the asymmetric transmission of acoustic waves. Numerical simulations show that the asymmetry is related to the properties of the host liquids and the input acoustic wave. Asymmetry can be enhanced if the maximum number density or the ambient radius of the cavitation bubbles in the low cavitation threshold liquid increases. Moreover, the direction of rectification will be reversed if the amplitude of the input acoustic wave becomes high enough.

Theoretical investigation of laser-generated guided waves in hollow cylinders

The problem of the laser-generated guided elastic waves in hollow cylinders is inves-tigated numerically by using the method of eigen-function expansion. The explicit expression of the transient waveform is given for the case of the outer surface of the hollow cylinder beat axi-symmetrically by four laser pulses with same energy. The characteristics of the transient waveform are explained based on the dispersive relations.

MEASUREMENTS AND THEORETICAL STUDY ON GROWTH RATES OF TURBULENT WIND WAVES

The spatial growth of turbulent wind waves is investigated theoretically and experimentally. Introduction of wave induced turbulent Reynolds stress, in particu- lar at the average interface, makes great improvement in the prediction of wind wave properties.

THEORETICAL ANALYSIS OF ATMOSPHERIC WAVES IN EQUATORIAL ZONE

In the equatorial zone the dynamic equations of the atmospheric motion are written inthe β-plane.These equations are linearized according to the mean atmospheric conditions.Numerical method is used to obtain a characteristic wave solution. Results obtained showthat the easterly wind shear changes the phase speed of low frequency waves more strikinglythan that of high frequency waves. The structure of the characteristic disturbances is sim-ilar to that in middle latitudes only with some exceptions in the relationship of geopo-tential field with vorticity field.

Theoretical analysis for sound wave scattering by parallel cylindrical tubes in boilers

Although the sonic soot cleaning techniques have been applied in boilers in power plants, petrochemical works and general industries world wide, most of the correlated basic problems have not been well solved yet. By using Helmholtz integral equation, sound wave scattered by heat-exchanger tubes is numerically calculated. Sound field distribution characteristics on the tube surfaces and around the tube group is obtained. The results can be applied to the development of sonic soot cleaning techniques in boilers.

Shock relations in gases of heterogeneous thermodynamic properties

Shock relations usually found in literatures are derived theoretically under the assumption of homogeneous thermodynamic properties, i.e., constant ratio of specific heats, γ. However, high temperature effects post a strong shock wave may result in thermodynamic heterogeneities and failure to the original shock relations. In this paper, the shock relations are extended to take account of high-temperature effects. Comparison indicates that the present approach is more feasible than other analytical approaches to reflect the influence of γ heterogeneity on the post-shock parameters.