Experiment Study on Local Scour around Four-step Inclined Artificial Reef as Incident Wave Direction

2019 ◽  
Vol 7 (1) ◽  
pp. 19-27
Author(s):  
Sung-Chul Jang ◽  
Min-Soo Kim ◽  
Han-Sam Yoon ◽  
Heon-Tae Kim
Keyword(s):  
Incident Wave ◽  
Artificial Reef ◽  
Local Scour ◽  
Wave Direction ◽  
Experiment Study ◽  
Incident Wave Direction

Hydrodynamic Analysis of Oil Storage Vessels for National Strategic Petroleum Reserve

2011 ◽  
Vol 291-294 ◽  
pp. 2541-2551
Author(s):  
Gang Jun Zhai ◽  
Yong Cheng ◽  
Wen Hua Wang ◽  
Yi Huang
Keyword(s):  
Incident Wave ◽  
Vertical Direction ◽  
Time History ◽  
Wave Force ◽  
Mooring System ◽  
Wave Direction ◽  
Storage Vessel ◽  
Oil Storage ◽  
Motion Responses ◽  
Incident Wave Direction

This paper expatiates hydrodynamic time-domain analysis on strategic oil storage vessels in free floating condition or with dolphin-fender mooring system by means of AQWA numerical software. The results indicate that motion responses of the oil storage vessel with dolphin-fender mooring have improved significantly. The time-history of wave diffraction forces in incident wave direction are basically consistent between the free floating and moored condition. However, in vertical direction of incident wave, the diffraction wave force of the oil storage vessel in free floating condition is obviously different from that with mooring system, which is the result of the coupling interaction between dolphin and vessels. Mooring forces include fender reaction and cable tension, as for which dominate, it depend on evocable motion responses about incident wave direction.

Homogeneous near-perfect invisible ground and free space cloak

2017 ◽  
Vol 31 (09) ◽  
pp. 1750059 ◽  
Author(s):  
Mohamad Fazeli ◽  
Seyyed Hassan Sedighy ◽  
Hamid Reza Hassani
Keyword(s):  
Incident Wave ◽  
Free Space ◽  
Single Step ◽  
Wave Direction ◽  
Transformation Theory ◽  
Design Flexibility ◽  
Mapping Process ◽  
Optical Transformation ◽  
Constitutive Parameters ◽  
Incident Wave Direction

A general approach to design near perfect invisible ground and free space cloaks is introduced in this paper. The proposed method which is based on the optical transformation theory, leads to homogeneous constitutive parameters for the cloaks without any singularities. Moreover, the single-step mapping process with linear relations achieves an uncomplicated designing process. Invisibility performance obtained by using this approach does not depend on the incident wave direction, also. The simplicity and design flexibility of the introduced approach with the homogeneity of extracted parameters greatly facilitate the design and fabrication processes of the both proposed ground and free space invisible cloaks. The numerical simulations prove the capability and universality of the proposed design approach.

Numerical Study of Wave Diffraction with Four Cylinders

2014 ◽  
Vol 638-640 ◽  
pp. 1758-1762
Author(s):  
Bao Lei Geng ◽  
Ci Heng Zhang
Keyword(s):  
Mathematical Model ◽  
Incident Wave ◽  
Numerical Study ◽  
Wave Force ◽  
Wave Direction ◽  
Linear Waves ◽  
The Given ◽  
Four Cylinders ◽  
Incident Wave Direction ◽  
Origin Point

By taking the 3D Laplace equation as the basic governing equation, a mathematical model with respect to the interaction between linear waves and arbitrary 3D structures was founded. With an example of wave action with four cylinders, numerical results show that when incident wave direction is 22.5°, wave force Fx on 1# cylinder and 2# cylinder is the biggest and when incident wave direction is 0°, wave force Fx on 3# cylinder and 4# cylinder is the biggest; wave force Fy and the wave height on origin point increases with incident wave direction increasing for the given layout and incident wave conditions.

scholarly journals Near Trapping Effect on Wave-Power Extraction by Linear Periodic Arrays

2019 ◽  
Vol 12 (1) ◽  
pp. 29
Author(s):  
Dezhi Ning ◽  
Zechen He ◽  
Ying Gou ◽  
Malin Göteman
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Hydrodynamic Interaction ◽  
Wave Power ◽  
Wave Direction ◽  
Power Extraction ◽  
Periodic Arrays ◽  
Wave Energy Converters ◽  
Incident Wave Direction ◽  
Energy Converters

Near trapping is a kind of strong hydrodynamic interaction phenomenon in a regular array under specific incident wave conditions, which causes the excitation force on the structures in the array to change suddenly. In this paper, based on linear potential flow theory, the effects of near trapping on the hydrodynamic interaction and wave-power extraction characteristics of linear periodic arrays composed of the oscillating float type wave energy converters are studied by using the higher-order boundary element method in a frequency domain. The parameters considered include the separation spacing, number of devices, and incident wave direction. It is found that the near trapping significantly reduces the overall wave-power extraction, especially for the cases with a large number of devices, and changes the trend of the power distribution. The occurrence of the near trapping phenomenon depends on the ratio of the separation spacing to the wavelength and the incident wave direction. The results highlight the effective layout of linear arrays under the influence of near trapping, which not only ensures the total production power, but also reduces the power difference among wave energy converters.

scholarly journals PREDICTION OF DEVELOPMENT OF SAND SPITS AND CUSPATE FORELANDS WITH RHYTHMIC SHAPES CAUSED BY SHORELINE INSTABILITY USING BG MODEL

2012 ◽  
Vol 1 (33) ◽  
pp. 35 ◽  
Author(s):  
Masumi Serizawa ◽  
Takaaki Uda ◽  
Shiho Miyahara
Keyword(s):  
Probability Distribution ◽  
Incident Wave ◽  
Three Dimensional ◽  
High Angle ◽  
Dimensional Model ◽  
Wave Direction ◽  
Three Dimensional Model ◽  
Wave Instability ◽  
Shoreline Evolution ◽  
Incident Wave Direction

The BG model (a three-dimensional model for predicting beach changes based on Bagnold’s concept) was used to simulate the shoreline evolution caused by the high-angle wave instability discussed by Ashton et al. Three calculations were carried out: the wave direction was assumed to be obliquely incident from 60˚ counterclockwise (Case 1) or from the directions of ±60˚ with probabilities of 0.5:0.5 (Case 2) and 0.65:0.35 (Case 3), while determining the incident wave direction from the probability distribution at each step. The three-dimensional development of multiple sand spits and cuspate forelands with rhythmic shapes was successfully explained using the BG model. The results of the previous study conducted by Ashton et al. were reconfirmed and reinforced.

RESEARCH ON THE WAVE-INDUCED SHIP MOTIONS IN FRONT OF DIFFERENT TYPES OF WHARF

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1731-1734
Author(s):  
YAN BAO LI ◽  
XUE LIAN JIANG
Keyword(s):  
Wave Height ◽  
Incident Wave ◽  
Ship Motions ◽  
Design Codes ◽  
Wave Direction ◽  
Green Function Method ◽  
Frequency Wave ◽  
Different Types ◽  
Current Design ◽  
Wave Induced

One important function of the port is to protect ship or some other facilities from wave attack so as to stably handle cargoes. In current design codes, there are mainly two expressions of the tranquility standard of harbor basin: one is the acceptable wave height in front of wharf; the other is the tolerable amplitude of ship motion. However, ship motions are affected by some more factors simultaneously, such as wave frequency, wave height, incident wave direction, ship properties and wharf type. This paper presents some computed results of the wave-induced ship motions on the basis of a port case in China. First, the Simple Green Function method is employed to solve and compare the 2-dimension hydrodynamic coefficients in front of open or bulkhead wharf. The results show a great difference between them. Then, this paper computes and discusses the ship motions in front of open wharf at different wave frequencies and incident wave directions.

scholarly journals WAVE BREAKING AND WAVE SETUP OF ARTIFICIAL REEF WITH INCLINED CROWN

2011 ◽  
Vol 1 (32) ◽  
pp. 18
Author(s):  
Keisuke Murakami ◽  
Daisuke Maki
Keyword(s):  
Cross Section ◽  
Wave Height ◽  
Energy Flux ◽  
Incident Wave ◽  
Wave Energy ◽  
Wave Breaking ◽  
Artificial Reef ◽  
The Other ◽  
Wave Setup ◽  
Other Hand

INTRODUCION The beach protection facilities are required in some situations to harmonize with coastal environments and utilizations(National Association of Sea Coast,2004). This study investigates some hydraulic functions of proposed multipurpose artificial reef which has an inclined reef crown. The reef is expected to protect beaches against storm waves, and also facilitates the surfing activities under mild wave conditions. The forced wave breaking on the reef sometimes causes a mass transport and wave setup. This study focuses on the following hydraulic characters to clear the efficiencies of proposed artificial reef with inclined crown. 1) Wave energy dissipation by the reef, 2) Generation of suitable wave breakers for surfing, 3) Wave setup behind the reef. HYDRAULIC EXPERIMENT SETUP A series of hydraulic experiments were carried out with using a two-dimensional wave flume. The model scale was assumed 1/30. Three kinds of cross sections were employed as the model of artificial reef (Fig.-1). Both Case-A and Case-B have the inclined crown. The cross section of Case-C, which has a flat crown, is set as a typical cross section of conventional artificial reef. The reef length of Case-A is the same as that of Case-C, and Case-B is double the length of Case-A. Two different submerged depths of crown, hc=2cm and 5cm, were set in the experiments. In Case-A and Case-B, their submerged depth of crown, hc, were defined as the minimum depth at the onshore edge of the crown. The incident wave heights were changed at 1cm intervals from 4cm to 9cm, and the periods were also chanced at 1 sec. intervals from 1 sec. to 2.4 sec. for each wave height. SUMMARY OF RESULTS The energy flux ratio of transmitted waves in Case-B shows similar values in Case-C under the stormy wave conditions in the case of hc=2cm. The longer reef shows favorable characters in dissipating wave energy as well as in maintaining a wider breaker zone on its crown. On the other hand, the transmitted energy flux in Case-A become slightly higher than that in Case-C. The inclined shape of the reef crown closely relates to both the type of wave breakers and the generation of higher order waves. Wave breakers observed in Case-A and Case-B are almost Plunging breaker or Collapsing breaker, and these breakers are suitable for surfing(Walker, et.al.,1972). In Case-C, on the other hand, most incident waves break at the offshore edge of the crown with backwash(Fig.-2). This means that the slope on the reef crown play an important roll in generating suitable breakers for surfing. Type of wave breakers on the inclined reef were summarized by surf similarity parameter(Battjes,1974). Fig.-3 shows the normalized wave setup behind each reef. The wave setup differs depending the reef sections. Case-A and Case-B check the wave setup effectively in comparison with Case-C. This excellent checking effect can be observed in the wide range of incident wave height and wave period. Through a series of hydraulic experiments, it is cleared that the difference of wave setup observed behind the reefs relates to the wave breaker type and wave breaker point on the reefs.

scholarly journals Conceptual-based design of an ultrabroadband microwave metamaterial absorber

2021 ◽  
Vol 118 (36) ◽  
pp. e2110490118
Author(s):  
Sichao Qu ◽  
Yuxiao Hou ◽  
Ping Sheng
Keyword(s):  
Incident Wave ◽  
Impedance Matching ◽  
Hierarchical Structures ◽  
Normal Incidence ◽  
Metamaterial Absorber ◽  
Wave Direction ◽  
Minimum Thickness ◽  
Lateral Plane ◽  
Metallic Ring ◽  
Microwave Regime

By introducing metallic ring structural dipole resonances in the microwave regime, we have designed and realized a metamaterial absorber with hierarchical structures that can display an averaged −19.4 dB reflection loss (∼99% absorption) from 3 to 40 GHz. The measured performance is independent of the polarizations of the incident wave at normal incidence, while absorption at oblique incidence remains considerably effective up to 45°. We provide a conceptual basis for our absorber design based on the capacitive-coupled electrical dipole resonances in the lateral plane, coupled to the standing wave along the incident wave direction. To realize broadband impedance matching, resistive dissipation of the metallic ring is optimally tuned by using the approach of dispersion engineering. To further extend the absorption spectrum to an ultrabroadband range, we employ a double-layer self-similar structure in conjunction with the absorption of the diffracted waves at the higher end of the frequency spectrum. The overall thickness of the final sample is 14.2 mm, only 5% over the theoretical minimum thickness dictated by the causality limit.

Wave Interaction With a Rectangular Pit

1991 ◽  
Vol 113 (3) ◽  
pp. 193-198 ◽  
Author(s):  
A. N. Williams ◽  
J. Vazquez
Keyword(s):  
Integral Equation ◽  
Green Function ◽  
Wave Interaction ◽  
Interior Solution ◽  
Wave Direction ◽  
Constant Depth ◽  
Interior Region ◽  
Exterior Region ◽  
Green Function Approach ◽  
Incident Wave Direction

A Green function approach is utilized to investigate wave interaction with a rectangular pit of finite dimensions in water of otherwise constant depth. The fluid domain is divided into two regions: an interior region which is finite in extent and represents the pit itself, and an exterior region consisting of the remainder of the fluid domain. An integral equation solution utilizing an appropriate Green function in the exterior region is linked to an interior solution in the form of a Fourier expansion containing unknown potential coefficients through matching conditions at the imaginary interface between the two regions. Discretizing the integral equation leads to a matrix system for these potential coefficients which may be solved using standard matrix techniques. Numerical results are presented for several example geometries which illustrate the effect of pit characteristics and incident wave direction on the water surface elevation.

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