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Potential flow

In fluid dynamics, potential flow describes the velocity field as the gradient of a scalar function: the velocity potential. As a result, a potential flow is characterized by an irrotational velocity field, a valid approximation for several applications; the irrotationality of a potential flow is due to the curl of the gradient of a scalar always being equal to zero. In the case of an incompressible flow the velocity potential satisfies Laplace's equation, potential theory is applicable. However, potential flows have been used to describe compressible flows; the potential flow approach occurs in the modeling of both stationary as well as nonstationary flows. Applications of potential flow are for instance: the outer flow field for aerofoils, water waves, electroosmotic flow, groundwater flow. For flows with strong vorticity effects, the potential flow approximation is not applicable. In fluid dynamics, a potential flow is described by means of a velocity potential φ, being a function of space and time.

The flow velocity v is a vector field equal to the gradient, ∇, of the velocity potential φ: v = ∇ φ. Sometimes the definition v = −∇φ, with a minus sign, is used, but here we will use the definition above, without the minus sign. From vector calculus it is known that the curl of a gradient is equal to zero: ∇ × ∇ φ = 0, the vorticity, the curl of the velocity field v, is zero: ∇ × v = 0; this implies. This has direct consequences for the applicability of potential flow. In flow regions where vorticity is known to be important, such as wakes and boundary layers, potential flow theory is not able to provide reasonable predictions of the flow. There are large regions of a flow where the assumption of irrotationality is valid, why potential flow is used for various applications. For instance in: flow around aircraft, groundwater flow, water waves, electroosmotic flow. In case of an incompressible flow — for instance of a liquid, or a gas at low Mach numbers; as a result, the velocity potential φ has to satisfy Laplace's equation ∇ 2 φ = 0, where ∇2 = ∇ ⋅ ∇ is the Laplace operator.

In this case the flow can be determined from its kinematics: the assumptions of irrotationality and zero divergence of flow. Dynamics only have to be applied afterwards, if one is interested in computing pressures: for instance for flow around airfoils through the use of Bernoulli's principle. In two dimensions, potential flow reduces to a simple system, analyzed using complex analysis. Potential flow theory can be used to model irrotational compressible flow; the full potential equation, describing a steady flow, is given by: ∂ 2 Φ ∂ x 2 + ∂ 2 Φ ∂ y 2 + ∂ 2 Φ ∂ z 2 − 2 M x M y ∂ 2 Φ ∂ x ∂ y − 2 M y M z ∂ 2 Φ ∂ y ∂ z − 2 M z M x ∂ 2 Φ ∂ z ∂ x = 0, with Mach number components M x = 1 a ∂ Φ ∂ x, M y = 1 a ∂ Φ ∂ y, M z = 1 a ∂ Φ ∂ z, where a is the local speed of sound. The flow velocity v is again equal to ∇Φ, with Φ the velocity poten

William Maxwell (railroad executive)

William Maxwell was an American business executive and politician, president of Erie Railroad from 1842 to 1843. Guy Maxwell was the founder of the Maxwell family, he managed banks, dug canals, was adopted as a chief into a tribe of the Seneca Indians. William Maxwell, Guy Maxwell's third son, was born at Tioga Point, now Athens, February 11, 1794, his parents moved that year to Newtown Point, now Elmira. He was educated in local schools, studied law in the office of Fletcher Mathews, a distinguished member of the bar at that time. In 1822 he was the District Attorney of Tioga County, of which Chemung County was a part, he was a delegate from the county to the State Constitutional Convention of 1846. He was always prominent in the public affairs of the town and county, was connected with the formation of the Chemung Canal Bank, one of the earliest enterprises of the kind in the Southern Tier. At one time most of the land in the Third and Seventh Wards of the city of Elmira, reaching beyond for two or three miles toward Horseheads, stood in his name.

He was a power in the Democratic party in those times in that region, what he said became the order of things. It was through his push and influence that the Chemung Canal was constructed, his enterprise and money helped on most of the railroad enterprises in Elmira, he early became interested in the project of the New York and Erie Railroad, was an influential delegate to several of the conventions held to adopt measures looking to the furthering of the prospects of that undertaking. It was the part he took at a convention held at Owego in the spring of 1842 that brought him into the prominence in Erie affairs that resulted in his being made president in the fall of that year, he married Zerwiah Baldwin, September 15, 1814, a daughter of William and Azubah Baldwin, pioneers of the Chemung Valley. One son died in infancy, they adopted as their daughter a niece of Azubah McQuhae. Mr. Maxwell died at Maxwell Park, November 22, 1856. An old-timer at Elmira pays this tribute to William Maxwell: I remember him since I can remember anything.

He lived in one of the most beautiful spots in the valley, a big brick house, with a great lawn, lots of trees, that must have belonged to the original forest there. He was fond of children, I have played for hours in and about his house, he was fitted by education to fill any position in the country, from President down. This article incorporates public domain material from Edward Harold Mott Between the Ocean and the Lakes: The Story of Erie. Collins, 1899. P. 461-62.

St. David, Illinois

St. David is a village in Fulton County, United States; the population was 589 at the 2010 census. St. David is located in eastern Fulton County at 40°29′30″N 90°3′7″W. Illinois Route 100 runs along the southeast edge of the village, leading southwest 10 miles to Lewistown, the county seat. Canton, the largest city in Fulton County, is 5 miles to the northeast via IL 100 and IL 78. According to the 2010 census, St. David has a total area of all land; as of the census of 2000, there were 587 people, 239 households, 163 families residing in the village. The population density was 1,982.1 people per square mile. There were 260 housing units at an average density of 877.9 per square mile. The racial makeup of the village was 0.17 % African American. There were 239 households out of which 28.0% had children under the age of 18 living with them, 54.8% were married couples living together, 9.6% had a female householder with no husband present, 31.4% were non-families. 25.1% of all households were made up of individuals and 18.0% had someone living alone, 65 years of age or older.

The average household size was 2.46 and the average family size was 2.95. In the village, the population was spread out with 24.5% under the age of 18, 7.3% from 18 to 24, 27.1% from 25 to 44, 22.0% from 45 to 64, 19.1% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 107.4 males. For every 100 females age 18 and over, there were 96.9 males. The median income for a household in the village was $30,625, the median income for a family was $37,188. Males had a median income of $34,792 versus $18,250 for females; the per capita income for the village was $14,292. About 8.2% of families and 11.1% of the population were below the poverty line, including 12.8% of those under age 18 and 5.8% of those age 65 or over. The village had one bank which closed and the brick bank building was taken over by the local water authority, one gas-station/pizzeria/convenience store, two taverns, the St. David Optimist Club, two churches; the Methodist church disbanded and the church building sold as a private residence.

The St. David U. S. Post Office branch is located on Main Street across from the Casey's General Store. There are two parks; the Village Park located on Main Street contains a ball diamond, playground area and the Village Memorial Board. 40 Acres Park contains a ball diamond. It is the location of the Village Hall. St. David is the home to garage; the township supervisor is Frank Shubert. The village government consists of a board of trustees, Village President, Village Clerk, treasurer and Zoning Officer, attorney; the village enforce the laws. Village President: Rosella Wells Village Clerk: Jason Myetich Village Board of Trustees: Michael Keithley, Steve Nebergall, David Vaughn, Terry Davis, Cheryle Mathis, Robert Crotzer Village Treasurer: Julie Russell Village Attorney: Andrewe Johnson Village Ordinance & Zoning Officer: Gary Lightle Village Street Supervisor: Bill Kumer

SZD-20X Wampir II

The SZD-20x Wampir II was a single-seat tail-less research glider designed and built in Poland from 1959. The SZD-20X Wampir II was designed to compare a flying wing designed to Standard class rules with a more conventional standard class glider. Main designer was Jan Dyrek. Based on experience with the earlier SZD-6X Nietoperz and SZD-13 Wampir tail-less gliders, the SZD-20X was an all wood flying wing, with the pilot sitting in a pod extending aft of the trailing edge on the centreline, large swept fins & rudders at approx 2/3 span on each wing; the SZD-20X was associated with the number 15, having a 15m span, aspect ratio of 15 and wing area of 15m², whether this was by design or accident is not known. Early flight trials commenced with hops towed behind a car to test control responses, followed by an aero-tow launch on 9 September 1959, piloted by Adam Zientek. Flight trials revealed a marked sensitivity to turbulence resulting in flutter, during trials at stalling speed, the SZD-20X entered a spin, which the rudders were unable to recover the aircraft from, only when the pilot shifted his weight as far forward as he could, did the SZD-20X recover from the spin.

Flying in the SZD-20X continued until 6 October 1959, when turbulence-induced flutter tore the aircraft apart, the pilot escaping with parachute. Data from The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du Monde Volume IIGeneral characteristics Crew: 1 Length: 6.2 m Wingspan: 15 m Height: 1.7 m Wing area: 15 m2 Aspect ratio: 15 Airfoil: NACA 23112 Empty weight: 171 kg equipped Gross weight: 268 kg Performance Stall speed: 50 km/h Never exceed speed: 200 km/h Aerotow speed: 120 km/h g limits: +4.5 -2 at 91 km/h Maximum glide ratio: 24.4 at 82 km/h Rate of sink: 0.84 m/s at 72 km/h Wing loading: 17.8 kg/m2 Aircraft of comparable role and era Horten H. IV SZD-6X Nietoperz Related lists List of J. H. Jane's Encyclopedia of Aviation. Studio Editions: London. P. 29

Rock Express

Rock Express was a Serbian music magazine. Rock Express was founded in 1997; the magazine's Editor-in-Chief was Branko Rogošić. The first issue was released in October 1997, the last, 42nd issue was released in December 2004. In January 1999, Rock Express started to publish Metal Express, dedicated to heavy metal music. Metal Express was released as a supplement for Rock Express, but appeared as an independent publication; the last, 15th issue of Metal Express was released in April 2004. In 1997, Rock Express started Rock Express Records; the label was heavy metal-oriented. Some of the artists that have been signed to Rock Express Records include: Draconic Kraljevski Apartman May ResultThe label reissued albums by former Yugoslav heavy metal acts, most notably Gordi and Heller, issued albums by foreign acts like Strapping Young Lad and Brujeria for the Serbian market. Rock Express Records at Discogs Rock Express Top 100 Yugoslav Rock Songs of All Times

Odd Is on Our Side

Odd Is on Our Side is the second graphic novel featuring Dean Koontz's character Odd Thomas. It was released in October 2010, it is written with illustrations by Queenie Chan in a manga style. It is Halloween in Pico Mundo and there is a whiff of something wicked in the autumn air. While the town prepares for its annual festivities, young fry cook Odd Thomas cannot shake the feeling that make-believe goblins and ghouls are not the only things on the prowl, and he should know. But his frequent visitor, the specter of Elvis Presley, cannot seem to point Odd in the right direction. With the help of his gun-toting girlfriend, Odd is out to uncover the terrible truth. Is something sinister afoot in the remote barn guarded by devilish masked men? Has All Hallows Eve mischief taken a malevolent turn? Or is the pleading ghost of a trick-or-treater a frightening omen of doom? Odd Thomas is the protagonist of the Odd Thomas series, he is a short-order cook at the Pico Mundo grill. He uses this ability to try and bring peace to the ghosts he encounters, so that they can move on to the next life.

Traumatic childhood experiences left him uncomfortable with guns, so he relies on his resourcefulness to escape the sometimes hostile situations in which he finds himself. Stormy Llewellyn is Odd's soulmate, she grew up in an orphanage, except for a six-month stint in which she was adopted by a family, only to be sexually abused. Stormy intends to marry Odd, she does not share Odd's fear of guns, carries a pistol with which she provides backup for Odd on his adventures. Wyatt Porter is the Chief of Police in Pico Mundo, serves as a father figure to Odd, he is one of the few people who are aware of Odd's abilities, has sometimes been able to catch elusive criminals with Odd's paranormal help. This graphic novel contradicts events in future novels, such as mentioning a Nintendo Wii, released four years after the first novel and Stormy's death. Odd Is on Our Side title listing at the Internet Speculative Fiction Database Douresseaux, Leroy. "Dean Koontz and Queenie Chan's Odd is on Our Side".

Retrieved February 4, 2012