Effect Of Wave Radiation Research Articles

Analysis of seawater-sediment-bedrock interaction model under obliquely incident P-SV waves with arbitrary angles

In this study, a numerical model for the seawater-sediment-bedrock system is proposed to evaluate the seismic responses of ocean sites under obliquely incident P-SV wsaves. First, the stiffness matrix method for the soil medium with an arbitrary angle input of seismic waves is extended to evaluate the seismic responses of the seawater-sediment-bedrock system. The wave radiation effects of the far-field domain are fully considered by the exact artificial boundary conditions. Second, the proposed model is verified by degenerated models and a numerical model developed by the authors, which are inapplicable to arbitrary-angle inputs of seismic waves. Third, the effects of site properties, including the porosity and permeability of the seabed, incident angle and depth of seawater, on the peak response of the sediment layer under obliquely incident P and SV waves are analysed. The results are conducive to understanding the seismic responses of ocean sites.

Experimental validation of laser radiation with a wavelength of 445±40 nm for the use in clinical practice

In many countries of the world, many preclinical studies have been carried out to study the effect of wave radiation of navy blue (400440 nm) and blue (445480 nm) colors on living and inanimate objects. In the available foreign literature, there are both complementary discoveries and contradictory results. The article presentes the conducted studies, the results of which reveal the high potential of laser radiation with wavelenght of 44540 nm.

Dynamic interaction analysis of structure-water-soil-rock systems under obliquely incident seismic waves for layered soils

A numerical model for the structure-water-soil (layered)-rock (SWLR) system is proposed in this paper to evaluate the system dynamic response, in which the fluid-solid coupling effect is considered by the interface conditions and the wave radiation effects of far-field domain are simulated by artificial boundary conditions. Moreover, this model covers four prime respects, including the discretization of interface conditions, the absorbing boundary conditions, the equivalent earthquake loading input and the general finite element equation. It can be solved by a standard time integration algorithm such as implicit Newmark's method. Furtherly, the effectiveness of the proposed model is verified by three numerical examples. Apart from these, the dynamic stiffness matrix method (DSM) of fluid and solid adopted in present study to acquire the equivalent earthquake loading effectively accomplishes the oblique incidence of the wave in layered half-space with arbitrary angles. Based on the proposed model, the effects of dynamic water-structure interaction (WSI) and soil-water interaction (SWI) on the seismic responses of offshore structure are investigated, which is conducive to the simplified analysis of dynamic fluid-solid interaction and the design of ocean engineering.

Seismic response analysis of the reef-seawater system under obliquely incident P and SV waves

Despite the increasing focus on the seismic safety of reef engineering sites, the current studies on this topic are still based on the hypotheses of uniform seismic excitations or the vertical incidence of seismic waves. In this study, a two-dimensional seismic analysis model for the reef-seawater system under obliquely incident P and SV waves is developed, which considers the fluid-soil-interaction and the wave radiation effects of the fluid and the solid domain. The oblique input of the seismic wave into the reef-seawater model is accomplished through the boundary substructure method. A series of parametric studies are conducted, the ground motion fields on the reef sites are discussed, and the effects of several fundamental factors on the seismic response are comprehensively studied. The results show that under most circumstances, the least favorable load case for the reef site seismic response is the vertical incidence of seismic waves. However, for the horizontal ground motion of the reef site under the P wave, the least favorable incident angle is approximately 30°. In addition, the largest horizontal seismic response usually appears near the downstream side of the reef flat, and the peak velocity and acceleration ratios can reach up to 4 in this area.

Numerical Analysis of Combined Wave Radiation and Diffraction on a Floating Barge

A two-dimensional boundary element method (BEM) based on the potential flow theory is adopted to study the combined wave radiation and diffraction by a single barge. The wave-body interaction problems are simulated using a mixed Euler-Lagrangian scheme, with fully nonlinear boundary conditions. The numerical schemes are verified through comparing with existing results, which show that both the wave runups on the barge and hydrodynamic forces can be calculated with sufficient accuracy. Cases of a single barge subjected to sway motion and regular waves are studied. The real contribution of this study is the outcomes of the spectral analysis conducted for test cases when wave radiation effects are considered in addition to pure wave diffraction. The cases of sway motion with the same frequency as incident wave are simulated first. It is found that sway motion will reduce the overall horizontal force when the frequency is lower than a critical frequency. After that, the higher the frequency, the bigger the horizontal force increasing effect. When the frequency of sway motion is lower than that of incident wave, in terms of the magnitude of the horizontal force, sway motion of the body will always make the resultant force larger than that of pure diffraction case.

Seismic response analysis of the reef-seawater system under incident SV wave

The seismic response analysis of a reef engineering site is the foundation for the seismic design of artificial islands and other upper constructions. This study proposes a two-dimensional seismic analysis model for the reef-seawater system, where the fluid-solid coupling effect is considered and the wave radiation effects of infinite fluid and solid domains are simulated by corresponding artificial boundary conditions. Meanwhile, the seismic wave input method based on the substructure of artificial boundaries is modified to accomplish the process of inputting the seismic waves with arbitrary incident angles into the calculation region. The accuracy of the proposed model is verified by numerical examples. Afterwards, we conduct the parametric studies and the seismic analysis of a series of practical layered reef models. The results indicate that the least favorable slope gradient for the seismic response is generally at approximately 30°, and the feature of wave velocity reduction along the vertical direction significantly magnifies the seismic response on the reef flat. The peak acceleration ratio near the edges of the reef flat distributes between 3 and 4. While in the middle area, it is usually between 1.5 and 2.5, and can reach up to 4 when the width of reef flat decreases.

Numerical prediction of wave added resistance using a Rankine Panel method

Based on a time domain Rankine panel method, a computer code was developed to predict wave added resistance. The unknown variables of the discretized flow field boundaries were represented using the quadratic B-spline basis function; the temporal derivative of the free surface conditions were approximated using an Euler scheme. The added resistance was computed via a near-field method. Three numerical approaches were introduced, namely, choosing the boundary end condition, neglecting the second order derivative of the disturbed potential, and computing the water line integral. Numerical computations were conducted in short and long waves for a Wigley hull, the S-175 container ship, and the KVLCC2 tanker. The double-body linearization and the Neumann–Kelvin linearization were tested, and numerical results were compared to published experimental measurements and numerical data. Fairly good agreement was found between the results of double-body linearization and the published data. Effects of wave radiation and diffraction on added resistance were analyzed, demonstrating that the interaction between radiation and diffraction should not be omitted in long waves.

Investigation of a semi-submersible floating wind turbine in surge decay using CFD

ABSTRACTThe hydrodynamic damping estimation of the surge motion and the flow characteristics of a moored semi-submersible floating offshore wind turbine is the focus of this paper. The numerical surge decay tests were investigated using a Reynolds-Averaged Navier–Stokes solver. Solution verification on the numerical simulations was performed by estimation of the numerical errors and uncertainties. A linear stiffness matrix and a non-linear quasi-static mooring model were used in the equations of motion. Several surge decay simulations were performed to understand the effects of wave radiation, coupled motions and non-linear moorings on the hydrodynamic damping and the flow field around the floater. The numerical results were compared with experimental data. The free surface had major effects on the hydrodynamic damping and the flow field.

Numerical study of forced roll oscillation of FPSO with bilge keel

This work shows a study about the bilge keel and its influence, width and form, on the roll damping of FPSO sections. A computational code was developed to simulate forced roll oscillation of a middle section of FPSO with different bilge keels types. The computational code calculates the solution of the Navier-Stokes equations in 2D, using the finite volume method and the upwind TVD scheme of Roe-Sweby. The effect of wave radiation is neglected. This work shows how the generated vortices influence the pressure distribution around the middle section of FPSO. The numerical results are compared with experimental results to validate the computational code. New bilge keel configurations were studied to improve the roll damping of FPSO.

Wave-to-wire simulation of a floating oscillating water column wave energy converter

A comprehensive time domain numerical simulation has been built for a moored, floating Oscillating Water Column (OWC) Wave Energy Converter (WEC), in order to provide accurate predictions of WEC power production. This novel simulation incorporates fully coupled simulations of the WEC dynamics, mooring lines, hydrodynamics, air chamber thermodynamics, air turbine dynamics and generator. It includes the forces and moments created by incoming irregular waves, moorings, buoyancy, wave radiation effects, viscous drag, and the differential pressure on the OWC hull and water column. The thermodynamics of the air chamber and the nonlinear biradial air turbine are fully coupled within the simulation.Using a biradial air turbine with a radius and angular velocities designed to maximize mechanical power, the rated power of the PTO’s Variable Frequency Drive (VFD) and generator are optimized to maximize annual energy production. Simulations of 36 differing sea states, constituting 71% of the annual wave energy transport for a Canadian Pacific location, provide an annual power production of 530 MWhr, with an overall wave-to-wire efficiency of 11.6%. Simulation variants with no external viscous drag and linearized moorings resulted in a 42% and 16% change in energy recovered while excluding air compressibility and internal viscous drag had limited influence.

Wave radiation of a cycloidal wave energy converter

Numerical results from a three-dimensional radiation model are presented where a cycloidal wave energy converter (WEC) is interacting with an incoming straight crested airy wave. The radiation model was developed in response to experimental observations from 1:10 scale experiments which were conducted in the Texas A&M Offshore Technology Research center wave basin. These experiments were the first investigations involving a WEC where three dimensional wave radiation effects were present due to the fact that the span of the WEC was much smaller than the width of the basin. The radiation model predicted the observed surface wave patterns in the experiment well, and showed that radiation induced wave focusing increased the recoverable wave power beyond the two-dimensional predictions for small WEC spans, while approaching the two-dimensional limit for very large spans. The numerical model was subsequently used to investigate the sensitivity of the WEC to misalignment between the incoming waves and the WEC shaft as well as the impact of a gap in the blade setup of a double WEC. For misalignment, the loss in efficiency was found to be strongly dependent on the ratio between WEC span and incoming wavelength, where short spans (on the order of one wavelength or less) which are realistic for actual ocean deployment showed only minor reductions in efficiency, while very long spans were found to be more sensitive to misalignment. The blade gap in a double WEC setup was found to have a relatively minor effect (up to 30%) on efficiency. Efficiency was found to either increase or decrease depending on the size of the gap.

Comparison of Ultrasonic Wave Radiation Effects on Asphaltene Aggregation in Toluene–Pentane Mixture Between Heavy and Extra Heavy Crude Oils

In this study, it is aimed to compare the efficiency of ultrasonic wave technology on asphaltene flocculation inhibition of crude oils with different American Petroleum Institute (API) gravities. A set of confocal microscopy test is performed and a series of statistical analysis is done. According to the results of this study, there is an optimum radiation time for both crudes at which the viscosity and the flocculation rate of asphaltenic crude oils reduces to its minimum. This optimum appears at later times of radiation for extra heavy oil. Also, it is shown that the rate of changes in the properties measured in this study is sharper for extra heavy crude oil. It could be concluded that the alternations caused by this technology is more significant for Kouh-e-Mond, which is heavier oil than Sarvak crude oil. Derjaguin–Ladau–Verwey–Overbeek (DLVO) kinetic model was also studied and it was understood that this model cannot be a validate model for radiated samples.

Single-well S-wave imaging using multicomponent dipole acoustic-log data

Single-well S-wave imaging has several attractive features because of its directional sensitivity and usefulness for fracture characterization. To provide a method for single-well acoustic imaging, we analyzed the effects of wave radiation, reflection, and borehole acoustic response on S-wave reflection measurements from a multicomponent dipole acoustic tool. A study of S-wave radiation from a dipole source and the wave’s reflection from a formation boundary shows that the S-waves generated by a dipole source in a borehole have a wide radiation pattern that allows imaging of reflectors at various dip angles crossing the borehole. More importantly, the azimuthal variation of the S-waves, in connection with the multicomponent nature of a cross-dipole tool, can determine the strike of the reflector. We used our theoretical foundation for borehole S-wave imaging to formulate an inversion procedure for field data processing. Application to field data validates the theoretical results and demonstrates the advantages of S-wave imaging. Application to near-borehole fracture imaging clearly demonstrates S-wave azimuthal sensitivity to fracture orientation.

Error field penetration in the presence of diamagnetic effects

The penetration of the magnetic field in a rotating inhomogeneous plasma is investigated with direct numerical simulations. The main focus of this work is to test the linear, singular-layer models when diamagnetic and finite Larmor radius effects are included. Our results confirm the existing analytical prediction when the plasma velocity at the resonant surface is outside the drift band, which is the band bounded by the electric drift velocity and the electron diamagnetic velocity. In the drift band, however, a revision of the theory is required. In this regime of velocity, the magnetic island radiates drift waves which can affect the dynamics of the system. Our results show that the penetration of the magnetic field occurs more easily than predicted by the theoretical models, which commonly neglect drift wave radiation effects.

An analytical theory of distributed axisymmetric barotropic vortices on the β-plane

An analytical theory of barotropic β-plane vortices is presented in the form of an asymptotic series based on the inverse of vortex nonlinearity. In particular, a solution of the initial value problem is given, in which the vortex is idealized as a radially symmetric function of arbitrary structure. Motion of the vortex is initiated by its interaction with the so-called ‘β-gyres’ which, in turn, are generated by the vortex circulation. Comparisons of analytical and numerical predictions for vortex motion are presented and demonstrate the utility of the present theory for times comparable to the ‘wave’ timescale. The latter exceeds the temporal limit derived from formal considerations. The properties of the far-field planetary wave radiation are also computed.This theory differs from previous calculations by considering more general initial vortex profiles and by obtaining a more complete solution for the perturbation fields. Vortex trajectory predictions accrue error systematically by integrating vortex propagation rates which are too strong. This appears to be connected to higher-order planetary wave radiation effects.