page_title: Hydraulic jumps in rectangular channels
section_title: About hydraulic jumps
hierarchical_section_title: Hydraulic jumps in rectangular channels / About hydraulic jumps
caption_attribution_description: English: This is a schematic of a hydraulic jump
context_page_description: Hydraulic jump in a rectangular channel, also known as classical jump, is a natural phenomenon that occurs whenever flow changes from supercritical to subcritical flow. In this transition, the water surface rises abruptly, surface rollers are formed, intense mixing occurs, air is entrained, and often a large amount of energy is dissipated. In other words, a hydraulic jump happens when a higher velocity, v₁, supercritical flow upstream is met by a subcritical downstream flow with a decreased velocity, v₂, and sufficient depth. Numeric models created using the standard step method or HEC-RAS are used to track supercritical and subcritical flows to determine where in a specific reach a hydraulic jump will form.
  There are common hydraulic jumps that occur in everyday situations such as during the use of a household sink. There are also man-made hydraulic jumps created by devices like weirs or sluice gates. In general, a hydraulic jump may be used to dissipate energy, to mix chemicals, or to act as an aeration device.
  To produce equations describing the jump, since there is an unknown energy loss, there is a need to apply conservation of momentum.
context_section_description: The depth of supercritical flow, y₁, ‘jumps’ up to its subcritical conjugate depth, y₂, and the result of this abrupt change in flow conditions is considerable turbulence and Energy Loss, EL.  Figure 1 shows a schematic of typical jump characteristics where E₁ is the energy of the upstream flow,  E₂ is the energy of the downstream flow and Lⱼ is the length of the hydraulic jump.  A series of small surface rollers are formed in a standing wave like the one shown in Figure 1.
  Figure 1. Hydraulic Jump Overall Schematic
caption: Hydraulic Jump Schematic1
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