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Standing Wave
In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect to time, and the oscillations at different points throughout the wave are in phase. The locations at which the absolute value of the amplitude is minimum are called node (physics), nodes, and the locations where the absolute value of the amplitude is maximum are called antinodes. Standing waves were first described scientifically by Michael Faraday in 1831. Faraday observed Faraday wave, standing waves on the surface of a liquid in a vibrating container. Franz Melde coined the term "standing wave" (German: ''stehende Welle'' or ''Stehwelle'') around 1860 and demonstrated the phenomenon in his classic experiment with vibrating strings. This phenomenon can occur because the medium is moving in the direction opposite to the movement of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lee Waves
In meteorology, lee waves are Earth's atmosphere, atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, :de:Hans_Deutschmann, Hans Deutschmann and Wolf Hirth, above the Giant Mountains. They are Frequency, periodic changes of atmospheric pressure, temperature and orthometric height in a Air current, current of air caused by vertical displacement, for example orographic lift when the wind blows over a mountain or mountain range. They can also be caused by the surface wind blowing over an escarpment or plateau, or even by upper winds deflected over a thermal updraft or cloud street. The vertical motion forces periodic changes in speed and Boxing the compass, direction of the air within this air current. They always occur in groups on the Windward and leeward, lee side of the terrain that triggers them. Sometimes, mountain waves can help to enhance precipitation a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harmonic
In physics, acoustics, and telecommunications, a harmonic is a sinusoidal wave with a frequency that is a positive integer multiple of the ''fundamental frequency'' of a periodic signal. The fundamental frequency is also called the ''1st harmonic''; the other harmonics are known as ''higher harmonics''. As all harmonics are periodic at the fundamental frequency, the sum of harmonics is also periodic at that frequency. The set of harmonics forms a '' harmonic series''. The term is employed in various disciplines, including music, physics, acoustics, electronic power transmission, radio technology, and other fields. For example, if the fundamental frequency is 50 Hz, a common AC power supply frequency, the frequencies of the first three higher harmonics are 100 Hz (2nd harmonic), 150 Hz (3rd harmonic), 200 Hz (4th harmonic) and any addition of waves with these frequencies is periodic at 50 Hz. In music, harmonics are used on string instruments and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fundamental Frequency
The fundamental frequency, often referred to simply as the ''fundamental'' (abbreviated as 0 or 1 ), is defined as the lowest frequency of a Periodic signal, periodic waveform. In music, the fundamental is the musical pitch (music), pitch of a note that is perceived as the lowest Harmonic series (music)#Partial, partial present. In terms of a superposition of Sine wave, sinusoids, the fundamental frequency is the lowest frequency sinusoidal in the sum of harmonically related frequencies, or the frequency of the difference between adjacent frequencies. In some contexts, the fundamental is usually abbreviated as 0, indicating the lowest frequency Zero-based numbering, counting from zero. In other contexts, it is more common to abbreviate it as 1, the first harmonic. (The second harmonic is then 2 = 2⋅1, etc.) According to Benward and Saker's ''Music: In Theory and Practice'': Explanation All sinusoidal and many non-sinusoidal waveforms repeat exactly over time – they are per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Node (physics)
A node is a point along a standing wave where the wave has minimum amplitude. For instance, in a vibrating guitar string, the ends of the string are nodes. By changing the position of the end node through frets, the guitarist changes the effective length of the vibrating string and thereby the note played. The opposite of a node is an antinode, a point where the amplitude of the standing wave is at maximum. These occur midway between the nodes. Explanation Standing waves result when two sinusoidal wave trains of the same frequency are moving in opposite directions in the same space and interfere with each other. They occur when waves are reflected at a boundary, such as sound waves reflected from a wall or electromagnetic waves reflected from the end of a transmission line, and particularly when waves are confined in a resonator at resonance, bouncing back and forth between two boundaries, such as in an organ pipe or guitar string. In a standing wave the nodes are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Surfing
River surfing is the sport of surfing either standing waves, tidal bores or upstream waves in rivers. Claims for its origins include a 1955 ride of along the tidal bore of the River Severn. River surfing on standing waves has been documented as far back as 1972 on an artificial wave created on a section of the ''Eisbach'' man-made river, a side arm of the Isar River, near Haus der Kunst in the Englischer Garten park in Munich, Germany, today offering the world's largest urban surfing spot. Standing waves In this type of river surfing, the wave is stationary on the river, caused by a high volume of water constricted by flowing over a rock and creating a wave behind. A requirement for this is a flowing water with shallow depth in which the inertia of the water overcomes its gravity due to the supercritical flow speed ( Froude number: 1.7 - 4.5, surpassing 4.5 results in direct standing wave) and is therefore neither significantly slowed down by the obstacle nor pushed to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Froude Number
In continuum mechanics, the Froude number (, after William Froude, ) is a dimensionless number defined as the ratio of the flow inertia to the external force field (the latter in many applications simply due to gravity). The Froude number is based on the speed–length ratio which he defined as: \mathrm = \frac where is the local flow velocity (in m/s), is the local gravity field (in m/s2), and is a characteristic length (in m). The Froude number has some analogy with the Mach number. In theoretical fluid dynamics the Froude number is not frequently considered since usually the equations are considered in the high Froude limit of negligible external field, leading to homogeneous equations that preserve the mathematical aspects. For example, homogeneous Euler equations are conservation equations. However, in naval architecture the Froude number is a significant figure used to determine the resistance of a partially submerged object moving through water. Origins In open c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supercritical Flow
A supercritical flow is a flow whose velocity is larger than the wave velocity. The analogous condition in gas dynamics is supersonic speed. According to the website Civil Engineering Terms, supercritical flow is defined as follows: The flow at which depth of the channel is less than critical depth, velocity of flow is greater than critical velocity and slope of the channel is also greater than the critical slope is known as supercritical flow. Information travels at the wave velocity. This is the velocity at which waves travel outwards from a pebble thrown into a lake. The flow velocity is the velocity at which a leaf in the flow travels. If a pebble is thrown into a supercritical flow then the ripples will all move down stream whereas in a subcritical flow some would travel up stream and some would travel down stream. It is only in supercritical flows that hydraulic jumps ( bores) can occur. In fluid dynamics, the change from one behaviour to the other is often describ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity
In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force between objects and the Earth. This force is dominated by the combined gravitational interactions of particles but also includes effect of the Earth's rotation. Gravity gives weight to physical objects and is essential to understanding the mechanisms responsible for surface water waves and lunar tides. Gravity also has many important biological functions, helping to guide the growth of plants through the process of gravitropism and influencing the circulation of fluids in multicellular organisms. The gravitational attraction between primordial hydrogen and clumps of dark matter in the early universe caused the hydrogen gas to coalesce, eventually condensing and fusing to form stars. At larger scales this results in galaxies and clust ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inertia
Inertia is the natural tendency of objects in motion to stay in motion and objects at rest to stay at rest, unless a force causes the velocity to change. It is one of the fundamental principles in classical physics, and described by Isaac Newton in his Newton%27s_laws_of_motion#First, first law of motion (also known as The Principle of Inertia). It is one of the primary manifestations of mass, one of the core quantitative properties of physical systems. Newton writes: In his 1687 work ''Philosophiæ Naturalis Principia Mathematica'', Newton defined inertia as a property: History and development Early understanding of inertial motion Joseph NeedhamProfessor John H. Lienhard points out the Mozi (book), Mozi – based on a Chinese text from the Warring States period (475–221 BCE) – as having given the first description of inertia. Before the European Renaissance, the prevailing theory of motion in western philosophy was that of Aristotle (384–322 BCE). On the surface ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whirlpool
A whirlpool is a body of rotating water produced by opposing currents or a current running into an obstacle. Small whirlpools form when a bath or a sink is draining. More powerful ones formed in seas or oceans may be called maelstroms ( ). ''Vortex'' is the proper term for a whirlpool that has a downdraft. In narrow ocean straits with fast flowing water, whirlpools are often caused by tides. Many stories tell of ships being sucked into a maelstrom, although only smaller craft are actually in danger. Smaller whirlpools appear at Rapids, river rapids and can be observed downstream of artificial structures such as weirs and dams. Large waterfall, cataracts, such as Niagara Falls, produce strong whirlpools. Notable whirlpools Saltstraumen Saltstraumen is a narrow strait located close to the Arctic Circle, south-east of the city of Bodø (town), Bodø, Norway. It has one of the strongest tidal currents in the world. Whirlpools up to in diameter and in depth are formed when ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saltstraumen
or is a small strait with one of the strongest Tide, tidal currents in the world. It is located in Bodø Municipality in Nordland county, Norway. It is located about southeast of the Bodø (town), town of Bodø. The narrow channel connects the outer Saltfjorden to the large Skjerstad Fjord between the islands of Straumøya and Knaplundsøya. The Saltstraumen Bridge on Norwegian County Road 17 crosses Saltstraumen. Current Saltstraumen has one of the strongest tidal currents in the world. Up to of seawater forces its way through a long and wide strait every six hours. Vortex, Vortices known as whirlpools or Maelstrom (whirlpool), maelstroms up to in diameter and in depth are formed when the current is at its strongest. At this point, one source claims that the tidal current can reach . Saltstraumen has existed for about two to three thousand years. Before that, the area was different due to post-glacial rebound. The current is created when the tide tries to fill Skjers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
