Waves

Jul 16, 2009 3 Comments by

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Greetings yachties,

This thread is all about waves, how they are formed, how they travel and how they destroy.

Enjoy

 

What is a wave?

We use the word wave in everyday conversation to refer to ocean, light, sound, or earthquake waves. But what do all of these seemingly different phenomena have in common, and why is it important to understand the nature of waves? Let’s explore these topics.

Waves transmit the energy that topples buildings during an earthquake, energy that allows us to communicate in the modern world, and energy that allows for life on earth at all. Our observations of the earth from space are also dependent on waves, those that are received by satellites. Thus, waves are a basic feature of the natural world and our ability to understand waves has resulted in many useful devices, cell phones, garage door openers, and microwave ovens, to name a few. With such a variety, what do all waves have in common? Ocean, light, sound, and earthquake waves share the characteristics contained in the scientific definition of wave.

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Wavelength

Wavelength is the distance between two consecutive and equivalent points on a wave. Wavelength can be quantified by measuring the distance between two equivalent and consecutive points, such as the distance between two peaks or two troughs. The scientific symbol for wavelength is a Greek letter called lambda.

Amplitude

Amplitude is a measurement of the vertical distance of the wave from the average. The wave axis is the average height of the wave over one cycle, and is usually considered to be zero. Heights above and below the average are given positive and negative values, respectively.

Frequency

Frequency is a measurement of how often a recurring event such as a wave occurs in a measured amount of time. One completion of the repeating pattern is called a cycle. Only moving waves which vary their positions with respect to time possess frequency. Frequency is one way to define how fast a wave moves.

lots more here

Greetings Yachties,

A little collection about waves and how they work and what they do.

Enjoy

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Hurricanes:

Increased Technology Offers Better Ways For Officials And Public To See The Storm Ahead

ScienceDaily (June 25, 2009) — Louisiana State University’s WAVCIS, or Wave-Current-Surge Information System for Coastal Louisiana, has a few new tricks up its sleeve in preparation for the 2009 hurricane season.
See also:
Earth & Climate

Drawing from a pool of scientific talent at the university, across the nation and Europe, WAVCIS now offers graphic, easy-to-understand model outputs projecting wave height, current depths and tracks, salinity ratios and water temperature measurements that not only provide state-of-the-art guidance to emergency management officials, but also give federal and state agencies such as the United States Navy, National Oceanic and Atmospheric Administration, the National Weather Service, National Hurricane Center and Louisiana Department of National Resources new and improved ways to test their own modeling accuracy.

“I believe WAVCIS is likely the most comprehensive program in the entire nation,” said Gregory Stone, director of both the WAVCIS program and the Coastal Studies Institute and also the James P. Morgan Distinguished Professor at LSU. “We now have 60 to 84 hour advance forecasting capabilities due to our satellite link-ups with NOAA and our supercomputing capabilities. Because of these advancements, we are in much better shape for the 2009 hurricane season to provide valuable information than we were in the past.”

WAVCIS operates by deploying equipment in the depths of the Gulf of Mexico. Currently, they have sensors attached to numerous oil platforms. Instruments are attached to towers on the platforms and allow meteorological measurements – air temperature, wind speed and direction, visibility – to be made; state-of-the-art oceanog

made here

The modern study of ocean surface waves started with a pioneer study by Sverdrup and Munk (1947). More than half a century has passed since then and the study of ocean surface waves has greatly advanced. The current numerical wave models, supported by many fundamental studies, enable us to compute ocean surface waves on a global scale with sufficient accuracy for practical purposes. However, physical process controlling the energy balance of ocean surface waves is still not completely understood.

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The picture below was taken on the oil freighter Esso Languedoc outside the coast of Durban (1980). The man who took it, Philippe Lijour, estimated the mean wave height when this occurred to be about 5-10 m. The mast on the starboard side is 25 m above the mean sea level. The wave approached from behind and broke over deck, but caused only minor damage.

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In areas where waves from storms in the open ocean approach shallower waters (e.g. several locations along the Norwegian coast), the waves will be refracted and diffracted as shown in the picture below (Aerial photo of an area near Kiberg on the coast of Finnmark, taken 12 June 1976 by Fjellanger Widerøe A.S.)

Company seeks to study ocean waves’ potential to

produce electricity

By SCOTT HADLY

SCRIPPS HOWARD NEWS SERVICE

A Washington state company has asked federal regulators for a permit to study the potential of producing electricity from ocean waves off the California, Hawaii and Atlantic coasts.

Grays Harbor Ocean Energy applied for the permit in October from the Federal Energy Regulatory Commission, a first step in what would be a multiyear process.

The company asked for permits in seven locations on both the Pacific and Atlantic coasts, he said. Those sites include areas off San Francisco and Ventura County in California, as well as sites off Hawaii, Massachusetts, Rhode Island, New York and New Jersey.

According to company officials, if all seven sites are developed, they could produce up to 7,700 megawatts of power, enough for 2 million homes.

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seasafe

Mechanical waves propagate because of differential interaction between kinetic and potential energy. Despite differences in the mass, force and motion of their constituent materials, both sound waves and ocean waves propagate energy such that distinct sources can be resolved by a distant observer. In this work I take observations collected at the sea surface by buoy and transform them so that they can be rendered as stereophonic sound. The transformation is primarily one of time scaling, converting days to seconds, but also includes projection from three dimensions into two and filtering to balance spectral response. I conclude with a subjective description of the sounds produced and directions for reproducing the same sounds on a personal computer.

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The interaction between water waves, a submerged breakwater, a vertical wall and a sandy seabed is studied experimentally. Laboratory experiments were conducted to record the water surface elevation and the pore pressures inside the seabed foundations. The previous analytical solution without submerged breakwater proposed by the first author [Jeng, D.-S. (1997). Wave-Induced Seabed Response in Front of a Breakwater, PhD Thesis, The University of Western Australia] was only valid in the region near the seabed surface.

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How does a wave work in deep water?

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While the nature of most ocean waves has long been known and their basic physics understood since the nineteenth century, intense study of ocean waves during the second half of the twentieth century has taken the subject from the realm of mathematical exercises to that of practical engineering. Modern understanding of the generation, propagation and interactions of ocean waves with each other and with oceanic features has advanced to a quantitative level offering predictive capacity. This paper presents a brief qualitative review of advances in knowledge of sound waves, wind waves, tsunamis, tides, internal waves and long-period vorticity waves. The review is aimed at non-specialists who may benefit from an overview of the current state of the subject and access to a bibliography of general-interest references.

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A preliminary study of ocean waves in the Hawaiian area

by Francis P. Ho

Published in 1969, Institute of Geophysics, University of Hawaii ([Honolulu, Hawaii])

here

Long-Period Seismic Waves from Nuclear Explosions in

Various Environments

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3 Responses to “Waves”

  1. Yachting News 4th January 2010 says:

    [...] more yachtyakka waves here [...]

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