Name: hydraulic jumps in open channels
Uploaded: 2025-03-26T15:04:26.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Earth Science

ES.8

ES.8.d

 Rapidly Varying Flow

&nbsp;In open channels, rapidly varying flow, or RVF, occurs when flow depth changes significantly over a short distance, with the rate of change of depth with distance reaching close to 1.This flow type is complex and challenging to analyze, but approximate solutions are often possible using simplified models.One well-known example is the hydraulic jump, where water shifts abruptly from a high-speed, shallow state to a deep, low-speed state over a small area.This phenomenon dissipates energy and prevents erosion downstream.Rapidly varying flows can also occur due to sudden changes in channel shape, leading to regions of flow separation, reversal, and surface oscillations.These flows may involve complex patterns and may demand in-depth, multi-dimensional modeling, especially for predicting issues like erosion near bridge piers, where simplified models are inadequate.RVF principles are used in devices like weirs, flumes, and sluice gates to measure flow in open channels. These devices create controlled RVF zones for accurate flow measurement, which is essential for effective water resource management in rivers, irrigation, and drainage systems.

 rapidly varying flow

Rapidly varying flow (RVF) in open channels is characterized by abrupt changes in flow depth over a short distance, with the rate of depth change relative to distance often approaching unity. These flows are inherently complex due to their transient and multi-dimensional nature, making exact analysis difficult. However, approximate solutions using simplified models provide valuable insights into their behavior.<h3 style="margin-left:0cm;">Key Features of Rapidly Varying Flow</h3>RVF is commonly observed in scenarios involving sudden transitions in flow conditions or channel geometry. One prominent example is the hydraulic jump, where water transitions rapidly from a fast, shallow flow to a slower, deeper state within a small area. This phenomenon is critical in energy dissipation, reducing the risk of downstream erosion. Additionally, RVF can occur at abrupt expansions, contractions, or obstructions in a channel, creating localized flow separation, reversal zones, and oscillatory surface patterns.<h3 style="margin-left:0cm;">Applications in Flow Measurement and Channel Design</h3>Devices such as weirs, flumes, and sluice gates utilize controlled RVF zones to measure flow in open channels accurately. By inducing predictable flow changes, these structures enable precise calculation of discharge rates, supporting effective water management. RVF principles are also applied to channel design for irrigation and drainage systems, ensuring controlled transitions and mitigating flow-induced damage.<h3 style="margin-left:0cm;">Challenges and Advanced Modeling</h3>While simplified models are useful for fundamental analysis, RVF often involves highly irregular patterns that require detailed computational or experimental modeling. For example, predicting erosion near bridge piers, where RVF causes turbulent vortices and sediment displacement, demands multi-dimensional simulations. Advanced modeling of RVF helps address these challenges, ensuring the stability and functionality of hydraulic structures in dynamic flow environments.

Rapidly varying flow (RVF) in open channels is characterized by abrupt changes in flow depth over a short distance, with the rate of depth change relative ...

Education

JoVE Core

Civil Engineering

Unit 1

Open Channel Flow

KEY TERMS AND CONCEPTS

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 water within a small region. This change helps dissipate energy, which can reduce downstream erosion. Rapidly varying flow can also appear at abrupt expansions, contractions, or obstructions in a channel. In those cases, the flow may separate, reverse locally, or form oscillating surface patterns.

Engineers use controlled rapidly varying flow in devices such as weirs, flumes, and sluice gates. These structures create predictable changes in water depth so discharge can be measured accurately in open channels. The same idea supports water management by improving flow calculations. Rapidly varying flow principles also help with channel design for irrigation and drainage systems, where controlled transitions can limit flow damage.

Because many rapidly varying flows are irregular, simplified analysis is not always enough. Predicting erosion near bridge piers is one example. There, rapidly varying flow can create turbulent vortices and move sediment. Detailed computational or experimental models are often needed to study these cases and support stable hydraulic structure design.

Hydraulic Jumps in Open Channels

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 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

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...

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 rapidly varying flow creates hydraulic jumps, affects erosion, and helps measure discharge with weirs, flumes, and sluice gates.

Hydraulic Jumps in Open Channels | JoVE K12

JoVE Core Civil Engineering offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

The Soil Ecosystem

Plants obtain inorganic minerals and water from the soil, which acts as a natural medium for land plants. The composition and quality of soil depend not ...

jenatron-an-experimental-approach-to-study-effects-plant-history-soil

JenaTron - An Experimental Approach to Study the Effects of Plant History and Soil History on Grassland Ecosystem Functioning

The global loss of biodiversity has motivated many studies that experimentally vary plant species richness and examine the consequences for ecosystem ...

The Water Cycle

The Earth&rsquo;s hydrosphere includes all of the areas where the storage and movement of water occurs. Since water is the basis of all living processes, ...

The Carbon Cycle

Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among ...

What are Biogeochemical Cycles?

The most common elements in organic molecules, carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus, are only available in the ecosystem in limited ...

The student will investigate and understand that freshwater resources influence and are influenced by geologic processes and human activity. Key ideas include water influences geologic processes including soil development and karst topography;

ES.8.a

Sustainable Development

As the human population continues to grow and use resources, we must be mindful of our planet&rsquo;s natural limits. Sustainable development provides a ...

Nutrients in Aquatic Ecosystems

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
Nitrogen and phosphorus are essential plant nutrients found in aquatic ...

Community Diversity

Populations do not live in isolation; thus, every population interacts with others in certain ways. These interactions give rise to a network of ...

What is an Ecosystem?

Overview

An ecosystem is the interaction between all abiotic and biotic factors in an environment and can be classified as terrestrial or aquatic. ...

The student will investigate and understand that freshwater resources influence and are influenced by geologic processes and human activity. Key ideas includeThe student will investigate and understand that freshwater resources influence and are influenced by geologic processes and human activity. Key ideas include the nature of materials in the subsurface affect the water table and future availability of fresh water;

ES.8.b

The student will investigate and understand that freshwater resources influence and are influenced by geologic processes and human activity. Key ideas include weather and human usage affect freshwater resources, including water locations, quality, and supply; and

ES.8.c

States of Water

Water exists in any one of the three classical states: solid (ice), liquid (water), and gas (steam or water vapor). The state of water depends on i) the ...

Hydraulic Jumps

Source: Alexander S Rattner and Mahdi Nabil; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
When ...

Gradually Varying Flow

Gradually varying flow (GVF) in open channels describes situations where water depth changes slowly along the channel due to factors like non-uniform bed ...

Design Example: Design of an Irrigation Channel

Trapezoidal channels are widely used in irrigation systems due to their cost-effectiveness and efficiency in conveying water. Trapezoidal channels feature ...

The student will investigate and understand that freshwater resources influence and are influenced by geologic processes and human activity. Key ideas include stream processes and dynamics affect the major watershed systems in Virginia, including the Chesapeake Bay and its tributaries.

Hydraulic Jumps in Open Channels

Description

Transcript

Tags

More videos by Standards