Name: liquid speed from reservoir outlets
Uploaded: 2026-01-30T03:08:28.000Z
Duration: 1 min 14 s
Channel: JoVE

Свободные струи демонстрируют поведение жидкости, описываемое уравнением Бернулли, когда жидкость выходит из сопла и свободно течет в воздух.
Скорость потока в сопле определяется высотой столба жидкости над ним, который преобразует потенциальную энергию в кинетическую.
Давление на выходе струи соответствует атмосферному давлению, а скорость увеличивается по мере того, как жидкость вытекает из большого резервуара.
Из-за инерции жидкости струя сужается сразу за пределами сопла, образуя наименьшую площадь поперечного сечения. Это явление известно как контрактная полая вена.
Отношение площади струи в области контрактной вены и площади сопла дает коэффициент сжатия.
Различные формы сопел, такие как остроконечные, хорошо закругленные, с острыми краями и ре-входящие, влияют на характер потока и коэффициент сжатия.
При проектировании таких систем, как водосбросы и водосливы, для точного измерения расхода учитывается эффект вены контракта.
Свободные форсунки имеют решающее значение в гражданском строительстве для управления потоком жидкости и минимизации структурных воздействий.

Свободная струя

Свободные струи описывают поток жидкости, выходящий из резервуара через отверстие в атмосферу без сопротивления. Скорость (V) струи жидкости выводится с использованием принципа Бернулли и выражается как:

<img alt="Equation 1" src="/files/ftp_upload/18037/18037_Equation_1.svg" style="text-align: center; height: 15px;">

 Где h — высота жидкости над отверстием. Это соотношение предполагает атмосферное давление как на поверхности резервуара, так и на выходе струи. Высота столба текучего вещества определяет скорость текучего вещества на выходе из сопла резервуара, где потенциальная энергия текучего вещества преобразуется в кинетическую энергию во время течения.

 Явление vena contracta возникает, когда жидкость выходит через отверстие с острым краем, в результате чего диаметр струи d_j становится меньше диаметра сопла d_o. Это происходит из-за того, что линии тока жидкости не могут следовать за резкими краями, создавая суженную область течения. Коэффициент сжатия — это отношение площади поперечного сечения струи в vena contracta к площади поперечного сечения сопла, и он количественно определяет степень сжатия струи. Этот параметр зависит от геометрии сопла, при этом различные конструкции, такие как разделительные сопла, сопла с острой кромкой, хорошо закругленные и возвратные сопла, создают различные схемы течения и характеристики сжатия. Для хорошо закругленного сопла C_c = 1,0, в то время как острые или разделительные отверстия уменьшают C_c примерно до 0,61. Возвратные сопла демонстрируют еще более низкие значения.

 Эти характеристики потока и эффекты сжатия имеют решающее значение в инженерных приложениях, связанных с выбросом жидкости, от резервуаров до промышленных сопел.

Свободные струи демонстрируют поведение жидкости, описываемое уравнением Бернулли, когда жидкость выходит из сопла и свободно течет в воздух.
Скорость потока ...

Education

JoVE Core

Civil Engineering

Unit 1

Раздел 1

Fluid Dynamics

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

Free Jet

liquid speed from reservoir outlets

Free jets show how liquid moves after leaving a reservoir through an opening and flowing into the air without resistance. The jet speed is found with Bernoulli’s principle, and it depends on the height of liquid above the opening. This relationship assumes atmospheric pressure at both the reservoir surface and the jet exit.

The liquid column’s height controls the speed at the nozzle because the fluid’s potential energy changes into kinetic energy during flow. As the liquid leaves the reservoir, its motion reflects this energy conversion. This is why a deeper liquid level can produce a faster jet.

A sharp-edged orifice can also cause vena contracta, which is the narrowed region where the jet becomes smaller than the nozzle opening. This happens because the streamlines cannot follow the abrupt edge smoothly. The contraction coefficient measures this narrowing by comparing the jet area at vena contracta with the nozzle area.

Nozzle shape changes the flow pattern and the amount of contraction. Knife-edge, sharp-edge, well-rounded, and re-entrant nozzles each produce different results. For a well-rounded nozzle, the contraction coefficient is 1.0, while sharp or knife-edged openings reduce it to about 0.61, and re-entrant nozzles produce even lower values. These effects matter in engineering systems that discharge liquid from reservoirs and industrial nozzles.

Liquid Speed from Reservoir Outlets

bernoulli's equation for flow along a streamline

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Pressure and Speed in Bernoulli's Equation

Bernoulli's equation links pressure, speed, and height in a moving fluid along a streamline. It is used for incompressible, inviscid fluids under steady flow. The idea comes from applying Newton's second law to a small fluid element. That element feels forces from pressure differences, gravity, and changes in velocity. The resulting equation shows how fluid energy is shared. In the equation, P is pressure, ρ is fluid density, v is velocity, g is the acceleration due to gravity, and h is...

bernoulli's equation for flow normal to a streamline

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Pressure Changes Across Curved Streamlines

Bernoulli's equation for flow normal to a streamline describes how pressure changes across curved streamlines. When a fluid follows a curved path, the outer side of the curve experiences centrifugal force, which pushes the fluid outward. The pressure is therefore higher on the inner side, near the center of curvature, and lower farther out. The size of this pressure difference depends on the fluid's velocity and the radius of curvature. In flows with nearly straight streamlines, the pressure...

bernoulli's equation: problem solving

Venturi Meter Flow Rate from Pressure

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static, stagnation, dynamic and total pressure

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Pitot-Static Measurement in Bernoulli Flow

Static pressure, dynamic pressure, stagnation pressure, and total pressure are key ideas in fluid dynamics. They are often explained with Bernoulli's equation. In that equation, p is static pressure, 1/2ρV^2 is dynamic pressure, γz is hydrostatic pressure or potential energy pressure, and pT is total pressure. For incompressible flow, the total pressure stays constant along a streamline. Static pressure is the pressure a fluid exerts when it is at rest, or when flowing fluid is brought to rest...

free jet

Free jets show how liquid moves after leaving a reservoir through an opening and flowing into the air without resistance. The jet speed is found with Bernoulli’s principle, and it depends on the height of liquid above the opening. This relationship assumes atmospheric pressure at both the reservoir surface and the jet exit. The liquid column’s height controls the speed at the nozzle because the fluid’s potential energy changes into kinetic energy during flow. As the liquid leaves the...

continuity equation

Fluid Flow and Area Changes

Fluid flow and area changes are linked by the continuity equation. For a steady flow of an incompressible fluid in a confined system, the mass flow rate stays constant. This idea is useful in nozzles, syringes, and pipes where the cross-sectional area changes. The mass flow rate is written as an equation that connects density, area, and velocity. For incompressible flow, the density stays the same, so the equation becomes simpler. When the area gets smaller, the fluid speed must increase. When...

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Fluid Head Profiles in Pipes and Channels

Fluid head profiles in pipes and channels show how pressure, speed, and height change in a flowing fluid. These profiles come from Bernoulli's equation for steady, incompressible, inviscid flow. In that equation, total head includes pressure head, velocity head, and elevation head. The energy line (EL) shows the total head available in the flow. It sits above the datum and includes all three energy parts. Under ideal conditions, the EL stays horizontal because the total energy does not change...

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Water Slide Speed and Bernoulli's Principle

Water slide speed is controlled by Bernoulli's principle and the height of the slide. Engineers use these ideas to keep the ride exciting while making sure the water stays safe for riders. As water moves downhill, gravity makes it speed up. The water at the bottom depends on the height it starts from. A taller slide gives the water more potential energy at the top. That energy changes into kinetic energy as the water descends, so the flow becomes faster. Bernoulli's principle helps describe...

key terms and concepts

Learn how liquid speed from a reservoir depends on height, Bernoulli’s principle, and nozzle shape, including vena contracta and contraction coefficient.

Liquid Speed from Reservoir Outlets | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Liquid Speed from Reservoir Outlets

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