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

تظهر النفاثات الحرة سلوك السوائل الموصوفة في معادلة برنولي ، حيث يخرج السائل من فوهة ويتدفق بحرية في الهواء.
يتم تحديد سرعة التدفق في الفوهة من خلال ارتفاع عمود السائل فوقها ، والذي يحول الطاقة الكامنة إلى طاقة حركية.
يتطابق ضغط خروج الطائرة مع الضغط الجوي ، وتزداد السرعة مع تدفق السائل من خزان كبير.
بسبب القصور الذاتي للسوائل ، تضيق النفاثة خارج الفوهة مباشرة ، وتشكل أصغر مساحة مقطعية. تعرف هذه الظاهرة باسم الوريد التعاقدي.
تعطي نسبة مساحة النفاثة عند الوريد ومساحة الفوهة معامل الانكماش.
تؤثر أشكال الفوهة المختلفة ، مثل تصاميم حافة السكين ، وتصميمات الحافة المستديرة جيدا ، والحواف الحادة ، وإعادة الدخول ، على نمط التدفق ومعامل الانكماش.
عند تصميم أنظمة مثل مجاري تصريف المياه والسدود ، يتم أخذ تأثير الوريد في الاعتبار لقياس التدفق بدقة.
تعتبر الطائرات الحرة ضرورية في تطبيقات الهندسة المدنية للتحكم في تدفق السوائل وتقليل التأثير الهيكلي.

النفث الحر

<div style="direction:rtl">يعبر النفث الحر عن انطلاق السائل الخارج من وعاء عبر فوهة الى الحيز الجوي دون مقاومة. يتم استنباط سرعة (V) السائل النفاث باستخدام مبدأ برنولي ويتم التعبير عنها على النحو التالي: <img alt="Equation 1" src="/files/ftp_upload/18037/18037_Equation_1.svg" style="text-align: center; height: 15px;"> حيث h هو ارتفاع السائل فوق الفوهة. تفترض هذه العلاقة الضغط جوي عند كل من سطح الوعاء ومخرج السائل النفاث. يتحكم ارتفاع عمود السائل داخل الوعاء في سرعة السائل عند الفوهة، حيث تتحول طاقة الوضع للسائل إلى طاقة حركية أثناء التدفق. تحدث ظاهرة السريان المختنق عندما يخرج السائل من خلال فوهة ذات حواف حادة، مما يؤدي الى أن يكون قطر النفث dj أصغر من قطر الفوهة. يحدث هذا لأن خطوط جريان السائل لا يمكنها التحرك بشكل مواز للحواف الحادة، مما يعمل على تقليص مساحة التدفق. معامل الاختناق هو نسبة مساحة المقطع العرضي للنفث عند خطوط النفث إلى مساحة المقطع العرضي للفوهة، وهو ما يعبر عن مقدار الاختناق. يتأثر هذا المعامل بالشكل الهمدسي للفوهة، تتولد انماط تدفق وخصائص اختناق مميزة مع التصميمات مختلفة مثل الفوهات ذات الحواف الحادة والفوهات الحادة الموجهة للخارج والفوهات المنحنية للخارج والفوهات الموجهة إلى الداخل. بالنسبة للفوهات المنحنية للخارج ، فإن معامل الاختناق يساوي Cc = 1.0، بينما بالنسبة للفوهات ذات الحواف الحادة فأن معامل الاختناق Cc يققل إلى حوالي 0.61. تقل تلك القيم بالنسبة للفوهات الموجهة إلى الداخل. تمثل خصائص التدفق وتأثيرات الاختناقات هذه اهمية بالغة الأهمية في التطبيقات الهندسية التي تتضمن تصريف السوائل، من الحاويات إلى الفوهات الصناعية.</div>

تظهر النفاثات الحرة سلوك السوائل الموصوفة في معادلة برنولي ، حيث يخرج السائل من فوهة ويتدفق بحرية في الهواء.
سرعة التدفق ...

Education

JoVE Core

Civil Engineering

الهندسة المدنية

Unit 1

الوحدة الأولى

Fluid Dynamics

ديناميكا السوائل

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الرئيسية

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

bernoulli-s-equation-for-flow-along-a-streamline

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

bernoulli-s-equation-for-flow-normal-to-a-streamline

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

A Venturi meter measures fluid flow rate in a pipeline by using pressure changes and Bernoulli's equation. In a sewage system, it can be used to determine wastewater flow rate by reading the pressure difference across the meter. The narrowed throat makes the fluid speed up, and that change in speed is linked to pressure drop. The first step is to find the cross-sectional areas of the pipe and the Venturi throat. These areas are needed to interpret the pressure difference shown on the pressure...

static, stagnation, dynamic and total pressure

static-stagnation-dynamic-and-total-pressure

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...

energy line and hydraulic gradient line

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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