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Lecture

Bed Shapes and Flow Resistance

In course

ENV-418: River eco-morphodynamics and bioengineering

The course deals with the interactions between hydraulics, solid transport by hauling and the watercourse space at the origin of the morphology and richness of habitats. Regime theory is presented and the quality of a stream's habitat is assessed. ...

Description

This lecture covers the influence of bed shapes on flow resistance in rivers, focusing on the characteristics of different forms such as dunes, ripples, and benches. It explains the concept of relative traction force and the critical values of friction tension. The lecture also delves into the dimensionless variables used to describe bi-phasic flow and the Shields diagram for sediment transport. Additionally, it discusses the impact of background shapes on flow dynamics, the formation of vortices, and the geometric features of various bed forms. The instructor emphasizes the relationship between water level and flow, the determination of resistance coefficients, and the effects of background shapes on flow patterns.

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Related concepts (32)

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The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with mechanical friction. The SI unit of electrical resistance is the ohm (Ω), while electrical conductance is measured in siemens (S) (formerly called the 'mho' and then represented by ℧). The resistance of an object depends in large part on the material it is made of.

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The term contact resistance refers to the contribution to the total resistance of a system which can be attributed to the contacting interfaces of electrical leads and connections as opposed to the intrinsic resistance. This effect is described by the term electrical contact resistance (ECR) and arises as the result of the limited areas of true contact at an interface and the presence of resistive surface films or oxide layers. ECR may vary with time, most often decreasing, in a process known as resistance creep.

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Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems where the particles are clastic rocks (sand, gravel, boulders, etc.), mud, or clay; the fluid is air, water, or ice; and the force of gravity acts to move the particles along the sloping surface on which they are resting.

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Fluvial processes

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