Simulation of Water Wave Interaction with Large Submerged Square Obstacles

Water waves propagation over submerged obstacles is considered. The problem serves as an efficient model for modeling breakwaters. A numerical wave tank is developed to simulate the induced flow field. The model is based on multiphase viscous flow assumptions. Computations are performed adopting clustered grids and suitable initial and boundary conditions. The results are verified using the flow field particle image velocimetry (PIV) measurements. Spatial and temporal resolutions are validated. Complex flow phenomena occurring due to the presence of the relatively large sized obstacle are visualized. The effect of wave parameters on the flow structure is investigated. A brief parametric study is presented and the resultant wave forces and turning moments are provided.

A multivibrator and oscillator trainer kit for an emerging pedagogy in engineering

Implementation of a complex circuit with hardware components in a conventional way seems to be quite difficult for the students. Resultant wave-shapes may not be accurate and determined values of different parameters may not be exact. Due to inaccurate outcomes and time-consuming process in a conventional way, researchers despond to continue their approach. In this paper, a trainer kit has been developed which is just like a laboratory with necessary components and aims to implement multivibrators (Bistable, Monostable, and Astable) and RC phase shift oscillators in the laboratory. A variable power supply is constructed in the trainer kit that provides 9 V dc to the multivibrators and 15 V dc to the oscillator. Potentiometer, voltage regulator, different active and passive components such as resistors, capacitor, op-amp, transistor, and numerous jumper wires are introduced in this kit. The trainer kit ascertains an easy implementation by eliminating complexity and assures accurate wave-shapes at the oscilloscope within a short time. To validate the proposed system, a survey program has been introduced among many students and faculty members. The outcome of the survey is the demonstration of student and instructor views and opinions which acknowledges the trainer kit as an efficient and compatible working platform.

Overview of Bering and Chukchi Sea Wave States for Four Severe Storms following Common Synoptic Tracks

Strong storms occur regularly over the ocean west of Alaska. These systems often loiter, generating persistent winds that can result in fully developed marine states that can maximize damage and hazard potential. Detailed analyses of storm events in terms of the resultant wave states are uncommon. This analysis examines the wave states associated with four particular storm events over the Bering and Chukchi Seas: October 2004, September 2005, and November 2009, and a September 2011 event that exhibited north winds. For each event a brief synoptic overview is presented followed by consideration of the resultant wave state, including parameters such as wave steepness. Wave data come from NOAA’s WAVEWATCH III (WW3) operational global ocean wave model, implemented for scenario use at the Arctic Region Supercomputing Center at the University of Alaska Fairbanks. In situ data are available from several National Data Buoy Center buoys and a wave buoy located in the Bering Strait, funded by the U.S. Environmental Protection Agency and NOAA and deployed for a few months in 2011. WW3 accurately captures the timing and evolution of the observed wave action (onset, growth, peak, and decline of large, steep wind waves) for each of the storm events. As per previous climatologically oriented studies, WW3 is found to underestimate significant wave heights on the order of 0.5 m or less. Also larger discrepancies, on the order of 1–2 m, are observed during periods of peak significant wave heights (Hs). In some cases WW3 overestimated Hs, especially during periods of rapid Hs decline.

Influences of Vorticity to Vertical Motion of Two-Dimensional Moonpool under Forced Heave Motion

Potential (inviscid-irrotational) and Navier-Stokes equation-based (viscous) flows were numerically simulated around a 2D floating rectangular body with a moonpool; particular emphasis was placed on the piston mode through the use of finite volume method (FVM) and boundary element method (BEM) solvers. The resultant wave height and phase shift inside and outside the moonpool were compared with experimental results by Faltinsen et al. (2007) for various heaving frequencies. Hydrodynamic coefficients were compared for the viscous and potential solvers and sway and heave forces were discussed. The effects of the viscosity and vortex shedding were investigated by changing the gap size, corner shape, and viscosity. The viscous flow fields were thoroughly discussed to better understand the relevant physics and shed light on the detail flow structure at resonant frequency. Vortex shedding was found to account for the most of the damping. The viscous flow simulations agreed well with the experimental results, showing the actual role and contribution of viscosity compared to potential flow simulations.

AN ANALYSIS OF THE ISGUR–WISE FUNCTION AND ITS DERIVATIVES WITHIN A HEAVY–LIGHT QCD QUARK MODEL

In determining the mesonic wave function from QCD inspired potential model, if the linear confinement term is taken as parent (with Coulombic term as perturbation), Airy's function appears in the resultant wave function — which is an infinite series. In the study of Isgur–Wise function (IWF) and its derivatives with such a wave function, the infinite upper limit of integration gives rise to divergence. In this paper, we have proposed some reasonable cutoff values for the upper limit of such integrations and studied the subsequent effect on the results. We have also studied the sensitivity of the order of polynomial approximation of the infinite Airy series in calculating the derivatives of IWF.

Localized Mixing Due to an Interfacial Solitary Wave Breaking on Seabed Topography in Different Ridge Heights

Experiments were carried out in a wave flume on internal solitary wave (ISW) of depression-type propagating over a submarine ridge in triangular shape. Tests were arranged in series from combinations of submarine ridges in different height and ISW in different wave amplitudes. The resultant wave motions were found differing from that of surface gravity waves. Experimental results suggested the blockage parameter ζ can be applied to classify various degrees of ISW–ridge interaction, i.e., ζ<0.5 for weak encounter, 0.5<ζ<0.7 for moderate encounter, and 0.7<ζ for wave breaking. In addition, three categories of ISW–ridge interaction were also employed by the relationship between the degree of blocking B and dimensionless wave amplitude ai∕H2.

Hybrid Wave Models and Their Applications for Steep Ocean Waves

Bound-wave components resulting from inter-actions among free-wave components have significant effects on resultant wave properties, especially in a steep ocean wave field. Hybrid Wave Models (HWM) distinguish the bound-wave from free-wave components in the decomposition of an irregular wave field as well as the prediction of its resultant proper-ties. To ensure the convergence, the HWMs selectively use the conventional and phase modulation approaches to address the nonlinear interactions between-free-wave components of different frequency ratios. The models are able to predict resultant wave properties accurately and deterministically based on the time-series measurements at fixed points. Four examples of their applications to the prediction of wave properties and wave-structure interactions are presented, which demonstrate the usefulness of HWMs to the studies of ocean surface waves.