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相关概念视频

Plane Potential Flows01:23

Plane Potential Flows

Plane potential flows simplify fluid motion by assuming the fluid to be irrotational and incompressible. These characteristics allow these flows to be described by a velocity potential function, ϕ, representing the flow speed in a given direction, and a stream function, ψ, that visualizes the flow path, both governed by Laplace's equation. These parameters help in estimating flow patterns, velocity distributions, and pressure fields around various hydraulic structures.
Uniform Flow
Uniform flow...
Gradually Varying Flow01:29

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 slope, channel shape variations, or obstructions. This flow type occurs when the depth adjusts gradually to balance gravitational forces, shear forces, and energy requirements, resulting in a low rate of depth change.Characteristics of Gradually Varying FlowGVF is commonly observed in natural streams, rivers, and canals, where flow depth...
Rapidly Varying Flow01:24

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.Key Features of Rapidly Varying FlowRVF is commonly observed in scenarios involving...
Plotting of Topographic Maps01:29

Plotting of Topographic Maps

Topographic maps represent the Earth's surface features using contour lines, which connect points of equal elevation to create a two-dimensional representation of three-dimensional terrain. Creating a topographic map requires a systematic approach.Begin by plotting a scaled grid and marking intersections corresponding to the survey's elevation data points. Assign elevation values at these intersections to build the base map. Next, determine contour levels using a consistent contour interval,...
Design Example: Analyzing Capacity Contours for Flood Risk Assessment01:17

Design Example: Analyzing Capacity Contours for Flood Risk Assessment

Flood risk assessment involves careful planning and analysis to ensure the safety of communities near water retention structures. Capacity contours are a vital tool in this process, as they illustrate the potential spread of water at specific levels in a given area. In the context of building a bund across a small valley, these contours play a critical role in evaluating the safety of nearby residential areas.In this example, the bund is intended to store stormwater in the valley. The engineers...
Vector Forms of Green’s Theorem01:26

Vector Forms of Green’s Theorem

The study of fluid motion often involves understanding how local rotational behavior relates to global circulation. In the context of a pond with pollutants, direct measurement of water movement along an irregular shoreline can be impractical. Green’s Theorem in vector form provides an alternative by relating the circulation around a closed boundary to properties of the flow within the enclosed region.Measurements of water velocity at different points define a continuous vector field that...

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相关实验视频

Updated: Jun 25, 2026

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation
09:49

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Published on: November 18, 2015

绘制世界自由流动的河流

G Grill1, B Lehner2, M Thieme3

  • 1Department of Geography, McGill University, Montreal, Québec, Canada. guenther.grill@mail.mcgill.ca.

Nature
|May 10, 2019
PubMed
概括

在全球范围内,只有37%的长河仍在自由流动,基础设施建设正在分裂重要的河流生态系统. 这项研究绘制了剩余的自由流动河流 (FFR),以帮助保护工作.

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Watershed Planning within a Quantitative Scenario Analysis Framework
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相关实验视频

Last Updated: Jun 25, 2026

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation
09:49

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Published on: November 18, 2015

Watershed Planning within a Quantitative Scenario Analysis Framework
12:44

Watershed Planning within a Quantitative Scenario Analysis Framework

Published on: July 24, 2016

Continuous Instream Monitoring of Nutrients and Sediment in Agricultural Watersheds
12:50

Continuous Instream Monitoring of Nutrients and Sediment in Agricultural Watersheds

Published on: September 26, 2017

科学领域:

  • 生态学
  • 水文学
  • 保护科学

背景情况:

  • 自由流动的河流是支持生物多样性和提供基本服务的关键全球生态系统.
  • 基础设施发展,特别是水,对河流连接,生态系统过程和生物多样性构成重大威胁.

研究的目的:

  • 评估河流的全球连接状况,并确定剩余的自由流动河流.
  • 提供旨在维护或恢复河流连接的全球和国家战略的基础.

主要方法:

  • 应用了一种新方法来量化全球1200万公里的河流连接.
  • 绘制地图确定了FFR,并评估了它们不间断地流向海洋的情况.

主要成果:

  • 只有37%的长度超过1000公里的河流在整个长度上保持自由流动.
  • 只有23%的河流不间断地流向海洋.
  • 其余的FFR主要位于偏远的北极,亚马逊和刚果盆地地区,只有少数人口密地区.

结论:

  • 水和水库是导致河流碎片化和连通性丧失的主要原因.
  • 迫切需要全球和国家战略来维护和恢复自由流动的河流及其相关生态系统.