Misplaced Pages

#61938

24-402: "Light truck, minivan, sport utility, and crossover vehicles represent a significant portion of the North American vehicle mix, and trailering usage of these vehicles has increased. Heavier-duty models, approaching medium-duty trucks and often intended for trailering, have become more popular as well. Some passenger cars are also rated to tow trailers. For many vehicles, trailer weight rating may be

48-414: A hydrostatic example (first figure), where the hydraulic head is constant, there is no flow. However, if there is a difference in hydraulic head from the top to bottom due to draining from the bottom (second figure), the water will flow downward, due to the difference in head, also called the hydraulic gradient . Even though it is convention to use gauge pressure in the calculation of hydraulic head, it

72-505: A vacuum from an initial velocity of 0, a mass will have reached a speed v = 2 g h {\displaystyle v={\sqrt {{2g}{h}}}} where g {\displaystyle g} is the acceleration due to gravity. Rearranged as a head : h = v 2 2 g . {\displaystyle h={\frac {v^{2}}{2g}}.} The term v 2 2 g {\displaystyle {\frac {v^{2}}{2g}}}

96-540: A construction town for workers building the dam. A road is located on the crest of the earth fill portion of the dam and a Forebay Bridge spans the Forebay. It was formerly part of Arizona State Route 68 to Nevada. In April 2004, the roadway was shut down to vehicle traffic. Pedestrian and bicycle traffic are permitted. The old roadway is now an extension of the Heritage Trail system. Barriers have been placed on

120-730: A major marketing point. As trailer weight ratings have increased, engine characteristics like horsepower and torque, thermal performance and driveline durability are no longer the only significant factors in determining trailering capability. Combination vehicle dynamics and tow-vehicle hitch/attachment structure have gained in significance. This document defines procedures and requirements to determine Gross Combination Weight Rating (GCWR) andcalculate corresponding Trailer Weight Rating (TWR) for any tow vehicle. These procedures will establish consistent rating requirements and processes so end users (customers) can reasonably compare similar class models in terms of trailering ability." The standard documents

144-465: A pump is the maximum height (pressure) it can deliver. The capability of the pump at a certain RPM can be read from its Q-H curve (flow vs. height). Head is useful in specifying centrifugal pumps because their pumping characteristics tend to be independent of the fluid's density. There are generally four types of head: After free falling through a height h {\displaystyle h} in

168-451: A set of tests a tow vehicle must pass with a specific weight to claim the capability to claim that trailer rating. Different criteria are specified for single rear wheel (SRW) and dual rear wheel (DRW) vehicles. The Davis Dam test requires the vehicle to climb the grade on Route 68 between Bullhead City and Golden Valley, Arizona , a climb of 3,500 ft (1,100 m) in 11 miles (18 km), starting at 100 °F (38 °C), with

192-639: A simplified form of the Bernoulli principle for incompressible fluids, can be expressed as: h = ψ + z {\displaystyle h=\psi +z} where In an example with a 400 m deep piezometer, with an elevation of 1000 m, and a depth to water of 100 m: z = 600 m, ψ = 300 m, and h = 900 m. The pressure head can be expressed as: ψ = P γ = P ρ g {\displaystyle \psi ={\frac {P}{\gamma }}={\frac {P}{\rho g}}} where P {\displaystyle P}

216-863: Is a vector gradient between two or more hydraulic head measurements over the length of the flow path. For groundwater , it is also called the Darcy slope , since it determines the quantity of a Darcy flux or discharge. It also has applications in open-channel flow where it is also known as stream gradient and can be used to determine whether a reach is gaining or losing energy. A dimensionless hydraulic gradient can be calculated between two points with known head values as: i = d h d l = h 2 − h 1 l e n g t h {\displaystyle i={\frac {dh}{dl}}={\frac {h_{2}-h_{1}}{\mathrm {length} }}} where The hydraulic gradient can be expressed in vector notation, using

240-402: Is a concept that relates the energy in an incompressible fluid to the height of an equivalent static column of that fluid. From Bernoulli's principle , the total energy at a given point in a fluid is the kinetic energy associated with the speed of flow of the fluid, plus energy from static pressure in the fluid, plus energy from the height of the fluid relative to an arbitrary datum . Head

264-540: Is a direct one, an increase in atmospheric pressure is an increase in load on the water in the aquifer, which increases the depth to water (lowers the water level elevation). Pascal first qualitatively observed these effects in the 17th century, and they were more rigorously described by the soil physicist Edgar Buckingham (working for the United States Department of Agriculture (USDA)) using air flow models in 1907. In any real moving fluid, energy

SECTION 10

#1732790422062

288-452: Is called the velocity head , expressed as a length measurement. In a flowing fluid, it represents the energy of the fluid due to its bulk motion. The total hydraulic head of a fluid is composed of pressure head and elevation head . The pressure head is the equivalent gauge pressure of a column of water at the base of the piezometer, and the elevation head is the relative potential energy in terms of an elevation. The head equation ,

312-498: Is dissipated due to friction ; turbulence dissipates even more energy for high Reynolds number flows. This dissipation, called head loss , is divided into two main categories, "major losses" associated with energy loss per length of pipe, and "minor losses" associated with bends, fittings, valves, etc. The most common equation used to calculate major head losses is the Darcy–Weisbach equation . Older, more empirical approaches are

336-408: Is expressed in units of distance such as meters or feet. The force per unit volume on a fluid in a gravitational field is equal to ρg where ρ is the density of the fluid, and g is the gravitational acceleration . On Earth, additional height of fresh water adds a static pressure of about 9.8 kPa per meter (0.098 bar/m) or 0.433 psi per foot of water column height. The static head of

360-508: Is more correct to use absolute pressure (gauge pressure + atmospheric pressure ), since this is truly what drives groundwater flow. Often detailed observations of barometric pressure are not available at each well through time, so this is often disregarded (contributing to large errors at locations where hydraulic gradients are low or the angle between wells is acute.) The effects of changes in atmospheric pressure upon water levels observed in wells has been known for many years. The effect

384-527: Is the gauge pressure (Force per unit area, often Pa or psi), The pressure head is dependent on the density of water, which can vary depending on both the temperature and chemical composition ( salinity , in particular). This means that the hydraulic head calculation is dependent on the density of the water within the piezometer. If one or more hydraulic head measurements are to be compared, they need to be standardized, usually to their fresh water head , which can be calculated as: where The hydraulic gradient

408-983: The del operator . This requires a hydraulic head field , which can be practically obtained only from numerical models, such as MODFLOW for groundwater or standard step or HEC-RAS for open channels. In Cartesian coordinates , this can be expressed as: ∇ h = ( ∂ h ∂ x , ∂ h ∂ y , ∂ h ∂ z ) = ∂ h ∂ x i + ∂ h ∂ y j + ∂ h ∂ z k {\displaystyle \nabla h=\left({\frac {\partial h}{\partial x}},{\frac {\partial h}{\partial y}},{\frac {\partial h}{\partial z}}\right)={\frac {\partial h}{\partial x}}\mathbf {i} +{\frac {\partial h}{\partial y}}\mathbf {j} +{\frac {\partial h}{\partial z}}\mathbf {k} } This vector describes

432-400: The spillway . The hydroelectric power plant is beside the inlet. The dam's purpose is to re-regulate releases from Hoover Dam upstream, and facilitate the delivery of Colorado River water to Mexico . Bullhead City, Arizona , and Laughlin, Nevada , are located just below the dam along the river. Davis Camp is also nearby, operated as a park by Mohave County. Bullhead City was originally

456-503: The air-conditioning on full. Davis Dam Davis Dam is a dam on the Colorado River about 70 miles (110 km) downstream from Hoover Dam . It stretches across the border between Arizona and Nevada . Originally called Bullhead Dam, Davis Dam was renamed after Arthur Powell Davis , who was the director of the U.S. Bureau of Reclamation from 1914 to 1923. The United States Bureau of Reclamation owns and operates

480-602: The dam, which was completed in 1951. Davis Dam impounds the Colorado River and forms Lake Mohave . Davis Dam is a zoned earth-fill dam with a concrete spillway, 1,600 ft (490 m) in length at the crest, and 200 ft (61 m) high. The earth fill dam begins on the Nevada side, but it does not extend to the Arizona side on the east. Instead, there is an inlet formed by earth and concrete, that includes

504-440: The depth to water in a piezometric well (a specialized water well ), and given information of the piezometer's elevation and screen depth. Hydraulic head can similarly be measured in a column of water using a standpipe piezometer by measuring the height of the water surface in the tube relative to a common datum. The hydraulic head can be used to determine a hydraulic gradient between two or more points. In fluid dynamics , head

SECTION 20

#1732790422062

528-503: The direction of the groundwater flow, where negative values indicate flow along the dimension, and zero indicates 'no flow'. As with any other example in physics, energy must flow from high to low, which is why the flow is in the negative gradient. This vector can be used in conjunction with Darcy's law and a tensor of hydraulic conductivity to determine the flux of water in three dimensions. The distribution of hydraulic head through an aquifer determines where groundwater will flow. In

552-423: The former road at each end of the earthen dam. The facility is heavily patrolled by security forces who strictly enforce parking regulations. The Davis Dam Power Plant is a hydroelectric power plant located on the Arizona side of the dam, beside the inlet. The hydroelectric plant generates between 1 and 2 terawatt-hours of electricity annually. The plant has a capacity of 251  MW (337,000  hp ) and

576-440: The tops of its five Francis turbines are visible from outside the plant. The plant's head is 136 ft (41 m). Head (hydraulic) Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum . It is usually measured as a liquid surface elevation, expressed in units of length, at the entrance (or bottom) of a piezometer . In an aquifer , it can be calculated from

#61938