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Related Concept Videos

Gradually Varying Flow01:29

Gradually Varying Flow

341
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...
341
Rapidly Varying Flow01:24

Rapidly Varying Flow

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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...
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Steady Flow of a Fluid Stream01:27

Steady Flow of a Fluid Stream

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Consider a control volume, such as a pipe with solid boundaries, through which fluid flows and changes direction due to the impulse exerted by the resulting force from the pipe walls. In steady flow, the mass of fluid entering the control volume at a given time, t, with velocity v1, is equal to the mass leaving after infinitesimal time dt, with velocity v2.
During this process, the momentum of the fluid within the control volume remains constant over the time interval dt. By applying the...
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Uniform Depth Channel Flow01:27

Uniform Depth Channel Flow

481
Uniform depth channel flow keeps fluid depth consistent along channels such as irrigation canals. In natural channels, such as rivers, approximate uniform flow is often assumed. This condition occurs when the channel’s bottom slope matches the energy slope, balancing potential energy lost from gravity with head loss due to shear stress. This balance prevents depth changes along the channel length, resulting in a steady, uniform flow.Uniform flow in open channels with a constant cross-section...
481
General External Flow Characteristics01:26

General External Flow Characteristics

475
The study of external flow is essential for creating structures and objects that interact efficiently and safely with moving fluids, such as air or water. When a body is immersed in a flowing fluid, it experiences two primary forces: drag, which opposes motion along the flow direction, and lift, which acts perpendicular to the flow. The shape, size, and orientation of the object influence these forces.Streamlined and Blunt Bodies in External FlowObjects in fluid flow are classified as...
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Stream Function01:20

Stream Function

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In two-dimensional incompressible fluid flow, the continuity equation is essential for ensuring mass conservation, meaning that any change in fluid entering or exiting a region is balanced by a corresponding change elsewhere. For incompressible flow, where density remains constant, this requirement simplifies to the condition that the divergence of the velocity field must be zero. Mathematically, this is expressed as,
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Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses
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A global streamflow reanalysis for 1980-2018.

Lorenzo Alfieri1, Valerio Lorini1, Feyera A Hirpa2

  • 1European Commission, Joint Research Centre (JRC), Ispra, Italy.

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|February 7, 2020
PubMed
Summary
This summary is machine-generated.

This study developed a new global hydrological model, improving streamflow simulations for water management and climate studies. The enhanced model shows better accuracy and reduced bias compared to previous versions.

Keywords:
Distributed modellingGlobal Flood Awareness System (GloFAS)Global hydrologyHydrological reanalysisModel calibration

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Area of Science:

  • Hydrology
  • Earth System Science
  • Environmental Modeling

Background:

  • Global hydrological reanalysis datasets are crucial for water management, climate change studies, and hazard assessment.
  • Previous datasets had limitations in resolution, uncertainty, bias, and spatial-temporal extent, restricting their use to qualitative assessments.
  • Advancements in atmospheric reanalysis data and computational power enable the development of more robust hydrological models.

Purpose of the Study:

  • To establish a gridded hydrological model with quasi-global coverage for seamless 39-year streamflow simulations.
  • To calibrate and validate the model using extensive river discharge observations and advanced atmospheric reanalysis data.
  • To improve the accuracy and reduce the bias of hydrological simulations for enhanced water resource applications.

Main Methods:

  • Development of a gridded hydrological model with quasi-global coverage.
  • Calibration of the model at 1226 river sections across 66 countries using ERA5 atmospheric reanalysis data.
  • Performance assessment by comparing simulated streamflow with observed discharge data.

Main Results:

  • The new model demonstrates significant improvements in streamflow simulation accuracy, with median Kling-Gupta Efficiency (KGE) of 0.67 and correlation (r) of 0.8.
  • Simulation bias was substantially reduced, with over 60% of stations exhibiting a percent bias within ±20%.
  • Regional variations in performance highlight areas needing further hydrological process investigation, such as parts of Africa and South Asia.

Conclusions:

  • The newly calibrated hydrological model offers a substantial advancement for global streamflow reanalysis.
  • High-quality observed discharge data are essential for achieving skillful hydrological model outputs.
  • The improved model will be integrated into the Copernicus - Global Flood Awareness System (GloFAS) operational runs.