Name: irrigation canal gate flow control
Uploaded: 2025-03-26T15:05:33.000Z
Duration: 1 min 30 s
Channel: JoVE

في قنوات الري ، تستخدم بوابات التدفق السفلي لتنظيم تدفق المياه في نقاط محددة. الأنواع الثلاثة الرئيسية هي البوابات الرأسية والشعاعية والأسطوانة.  تخلق البوابات العمودية نفاثة تتدفق بحرية من خلال التحرك لأعلى ولأسفل. تدور البوابات الشعاعية ، وتدور بوابات الأسطوانة للتحكم الدقيق. يعتمد التدفق عبر هذه البوابات على ظروف المصب ، مما يؤدي إلى تدفق حر أو غارق. يحدث التدفق الحر عندما يخرج الماء كنفاثة فوق الحرجة معرضة للغلاف الجوي. يعتمد معدل التدفق على ارتفاع فتح البوابة والسرعة المرجعية ، ويتم ضبطها بواسطة معامل التفريغ. عندما تتحكم عقبة في اتجاه مجرى النهر في العمق ، فإن كتلة مائية مضطربة تغطي الطائرة ، مما يؤدي إلى تدفق غارق. يتم ضبط معدل التدفق في التدفق الغارق عن طريق تعديل معامل التفريغ. تمثل سلسلة من المنحنيات السفلية على المخطط قيما نموذجية للتدفق الخارج. عندما يساوي y3 y1 ، لا يوجد فرق في الارتفاع يدفع التدفق ، مما يتسبب في انخفاض معامل التفريغ إلى الصفر ، مما يوقف التدفق. بالنسبة لنسبة y3 / a معينة ، يزداد معامل التفريغ مع زيادة عمق المنبع حتى يصل إلى الحد الأقصى. ينخفض هذا الحد الأقصى مع انخفاض نسبة y3/a.

بوابات التدفق السفلي

تعتبر بوابات التدفق السفلي حيوية للتحكم في تدفق المياه في قنوات الري. تخدم الأنواع الثلاثة الرئيسية لبوابات التدفق السفلي - البوابات الرأسية والشعاعية والأسطوانية - أغراضا مختلفة مع ضمان إدارة التدفق الفعالة. تتحرك البوابات العمودية لأعلى ولأسفل ، مما يولد نفاثة مائية تتدفق بحرية. تدور البوابات الشعاعية لتنظيم التدفق ؛ وتدور بوابات الأسطوانة لإجراء تعديلات دقيقة. يتأثر التدفق عبر هذه البوابات بظروف المصب ، مما يؤدي إلى تدفق حر أو غارق. التدفق الحر والغارق في ظروف التدفق الحر ، يخرج الماء كنفاثة فوق الحرجة معرضة للغلاف الجوي. يعتمد معدل التدفق في هذا النظام على ارتفاع فتحة البوابة والسرعة المرجعية ، وكلاهما يتم ضبطه بواسطة معامل التفريغ. يفسر هذا المعامل تأثيرات هندسة البوابة وديناميكيات السوائل ، ويلعب دورا مهما في تحديد سلوك التدفق. يحدث التدفق الغارق عندما ترفع ظروف المصب ، مثل العائق ، عمق الماء ، مما يخلق كتلة مائية مضطربة فوق النفاثة. يقلل هذا الغمر من الرأس الفعال ويتطلب معامل تفريغ معدل ليعكس ظروف التدفق الجديدة. يتم تصوير خصائص التدفق للتدفق الخارج الغارق على أنها منحنيات أقل على مخططات معامل التصريف ، والتي تمثل القيم التشغيلية النموذجية للتدفق المغمور. يوفر التدفق الغارق تصريفا محكما في ظل ظروف مجرى النهر المتغيرة ، مما يقلل من سرعة النفاثة ، ويقلل من التآكل ، ويثبت مستويات المياه ، ويمنع التهوية المفرطة. إنه مفيد لتبديد الطاقة ، وتنظيم التدفق ، والحفاظ على الظروف الهيدروليكية المستقرة في أنظمة الري والتحكم في الفيضانات. تأثير نسب العمق على التدفق العلاقة بين أعماق المياه في المنبع والمصب أمر بالغ الأهمية لفهم التدفق عبر بوابات التدفق. عندما يساوي عمق المصب (y3) عمق المنبع (y1) ، لا يوجد رأس فعال لدفع التدفق ، مما يتسبب في انخفاض معامل التفريغ إلى الصفر وتوقف التدفق. مع انخفاض نسبة y 3 / a (عمق المصب بالنسبة إلى البعد المرجعي) لعمق معين في المنبع ، يزداد معامل التفريغ حتى يصل إلى القيمة القصوى ، مما يعكس ظروف التدفق المثلى. تسلط هذه الديناميكيات الضوء على أهمية تشغيل البوابة بدقة في تنظيم تدفق المياه بكفاءة.

Underflow gates are vital for controlling water flow in irrigation canals. The three main types of underflow gates — vertical, radial, and drum gates ...

Education

JoVE Core

Civil Engineering

الهندسة المدنية

Unit 1

الوحدة الأولى

Open Channel Flow

الجريان في القنوات المفتوحة

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

Underflow Gates

irrigation canal gate flow control

Underflow gates control water flow in irrigation canals. They help manage discharge so water moves where and when it is needed. The main underflow gate types are vertical gates, radial gates, and drum gates.

Vertical gates move up and down. They create a free-flowing water jet. Radial gates pivot to regulate flow, and drum gates rotate for fine adjustments. Each design supports effective flow management in different canal settings.

Downstream conditions change how water passes through an underflow gate. These conditions can produce free outflow or drowned outflow. In free outflow, water leaves as a supercritical jet that is exposed to the air. The flow rate depends on the gate opening height and a reference velocity. A discharge coefficient adjusts this value to account for gate shape and fluid effects.

Drowned outflow happens when downstream water depth rises, often because of an obstacle. The water then covers the jet and forms a turbulent mass over it. This submergence lowers the effective head, so the discharge coefficient must be adjusted for the new flow condition. On discharge coefficient plots, drowned outflow appears as the lower set of curves for submerged flow.

Drowned outflow can be useful in irrigation and flood control systems. It helps reduce jet velocity, limit erosion, stabilize water levels, and prevent too much aeration. It also supports energy dissipation and steadier hydraulic conditions when downstream water levels vary.

The depth ratio between upstream and downstream water is also important. When downstream depth y3 equals upstream depth y1, there is no effective head to drive flow. The discharge coefficient then drops to zero, and flow stops. As the ratio y3/a decreases for a given upstream depth, the discharge coefficient rises until it reaches a maximum value. These relationships show why accurate gate operation matters for efficient water control.

Irrigation Canal Gate Flow Control

energy considerations in open channel flow

energy-considerations-in-open-channel-flow

Flow Depth and Energy in Open Channels

Open channel flow involves water moving with a free surface exposed to the air. Rivers, canals, and artificial channels are common examples. In these systems, gravity and surface effects shape the flow more than the behavior seen in closed pipes. Energy analysis helps explain how depth, velocity, and slope work together. Specific energy combines the potential energy from water depth and the kinetic energy from flow speed. For a given discharge, or flow rate, there are often two possible depths...

uniform depth channel flow

Channel Slope and Flow Balance

Uniform depth channel flow keeps the water depth steady along an open channel. This idea is often used for irrigation canals and is also a useful approximation for rivers. The channel bottom slope must match the energy slope. That balance offsets the gravity energy lost to shear stress at the boundary, so the depth does not change along the channel length. In a constant cross-section channel, uniform flow means the depth and velocity stay consistent. Two key measures are the flow area and the...

uniform depth channel flow: problem solving

uniform-depth-channel-flow-problem-solving

Calculating Trapezoidal Channel Flow Rate

Calculating trapezoidal channel flow rate starts with the channel shape and the depth of flow. For a trapezoidal channel, identify the bottom width, side slope, and flow depth first. These values define the cross-section used in the calculation. Next, find the cross-sectional area for the flowing water. Use the depth of flow, the bottom width, and the side slope angle to determine area. Then calculate the wetted perimeter, which includes the bottom width and the sloped side lengths that touch...

gradually varying flow

Open Channel Depth Changes in GVF

Gradually varying flow in open channels describes water depth that changes slowly along a channel. The depth adjusts over distance as gravity, shear forces, and energy needs stay in balance. This creates a low rate of change in the water surface. Gradually varying flow is common in natural streams, rivers, and canals. In these settings, the depth shifts little by little over long distances. The slope of the channel bed, compared with the energy slope, helps determine how the flow behaves. A...

 rapidly varying flow

Hydraulic Jumps in Open Channels

Rapidly varying flow in open channels describes a sudden change in water depth over a short distance. The depth can change so quickly that the rate of change with distance is close to one. These flows are difficult to analyze exactly because they are transient and multi-dimensional. Approximate solutions with simplified models still give useful insight into how they behave. A common example is the hydraulic jump. In a hydraulic jump, fast and shallow water changes quickly into slower, deeper...

hydraulic jump

Flow Regimes and Energy in Hydraulic Jumps

Hydraulic jumps happen in open channels when fast, shallow water changes into slower, deeper water. This sudden rise in depth depends on the upstream Froude number, which compares flow speed to wave speed. A hydraulic jump can form only when the upstream flow is supercritical, with Fr greater than 1. If Fr is less than 1, the flow is already subcritical, and a jump cannot form. That is because the jump would require a negative head loss, which is not possible under thermodynamic principles.

hydraulic jump: problem solving

Hydraulic Jump in a Rectangular Channel

Hydraulic jump in a rectangular channel shows how flow speed and water depth change when a gate closes downstream. The jump travels upstream at 2 meters per second, so that wave speed is part of the calculation. The initial channel flow speed is 6 meters per second. To find the water depths on each side of the jump, first calculate the effective upstream velocity. This combines the flow moving through the channel with the upstream-moving wave. Next, identify the flow velocities before and...

weir

Weir Flow Measurement and Control

A weir is a hydraulic structure that partly blocks an open channel and helps control water flow. It also makes it possible to measure discharge, which is the amount of water moving past a point in a given time. Because of this, weirs are important in water resource management. Weirs are used in river flow regulation, irrigation systems, and flood control channels. They guide water to flow over or through the structure, which lets engineers estimate flow rates more accurately. This makes them...

weir: problem solving

Weir Flow Rates and Channel Depth

Weirs are hydraulic structures used to measure water flow in open channels. In a rectangular channel, they help calculate discharge, or the volume of water passing a point each second. The weir head is held at a fixed height above the channel bottom, which makes the math easier and lets students compare depth with flow rate. Three weir types are used in this setting: rectangular sharp-crested, triangular sharp-crested, and broad-crested. The rectangular sharp-crested weir depends on the weir...

underflow gates

Underflow gates control water flow in irrigation canals. They help manage discharge so water moves where and when it is needed. The main underflow gate types are vertical gates, radial gates, and drum gates. Vertical gates move up and down. They create a free-flowing water jet. Radial gates pivot to regulate flow, and drum gates rotate for fine adjustments. Each design supports effective flow management in different canal settings. Downstream conditions change how water passes through an...

design example: design of an irrigation channel

design-example-design-of-an-irrigation-channel

Designing Trapezoidal Irrigation Channels

Trapezoidal irrigation channels are a common choice for moving water in farms and other water systems. Their flat bottom and sloping sides make them stable and easier to build than many other channel shapes. They are also cost-effective and efficient for carrying water. The channel size depends on the needed flow capacity and the site conditions. Designers choose the bottom width and the side slope ratio to match those demands. For unlined channels, the side slope is kept gentle to help...

key terms and concepts

Learn how underflow gates regulate irrigation canal flow, including vertical, radial, and drum gates, plus free and drowned outflow behavior.

Irrigation Canal Gate Flow Control | 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

Irrigation Canal Gate Flow Control

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