Research analysis indicates that hydraulic jumps may occur in places like rivers and any other fast flowing liquid channels. They occur when liquids with a high rate of kinetic energy are slowed down immediately leading to its format. These hydraulic jumps can happen in in places like waterfalls and also in fast flowing cataracts. According to Bonn 2009, a hydraulic jump occurs in open channel flows which include spillways and rivers. A high velocity of liquid discharges into a lower velocity zone and an immediate rise occurs on the surface of the fluid. An immediate slowdown of the rapidly flowing liquid occurs with an increase in the height. When the strike happens, there is the conversion of some of the initial kinetic energy of the water flow to a rise in the potential energy, and energy can get lost in the turbulence to heat (Bonn 2009, p. 68).
In an open channel flow, the hydraulic jump manifests by a fast flow and it then slows rapidly and then piles itself in a similar way to form shockwaves. If the initial fluid speed was below the critical rate for jumps to occur, then it would not happen. If the initial speed flow is not high above the critical speed, then the transition appears in the form of an undulating wave. Increase in the initial velocity flow makes the transition more abrupt and when it reaches enough high speeds, the front shift breaks and then it curls back upon itself. On the occurrence of this, several things accompany the jump that includes air entertainment, eddying, violent turbulence and also undulations or waves on the surface of the liquid involved (Bonn, 2009, p. 71).
A hydraulic jump manifests themselves into two types; the stationary hydraulic jump and the tidal bore. These two events occur differently in different formations. The tidal bore is an undulating wave that moves upstream and is on the water that is already flowing downstream. This force that acts against the water flow can happen in water cataracts. The second one is the cascade which is an undulating wave that moves downstream and then overtakes shallow water downstream. The other form is that of the stationary hydraulic jump whereby fast-flowing liquid changes to a stationary jump and then to a slowly moving water. The same can happen while pouring water into a cup and in rivers (Holland, 2002, P. 67).
Thorpe 2010, reminds that, engineers like constructing hydraulic jumps downstream so as to slow down the flow of water downstream. Once the downstream hydraulic jump develops, the kinetic energy of the water slows down. People can pass the place without any danger of being drawn away downstream by the water. Engineers can construct bridges on the downstream of hydraulic jumps. The reason is that, in case of any accident, the water below will not endanger the victims.
A current can be very dangerous when the downstream water is in the structure of the tail and is fully developed hydraulic jump to form. When fast moving water comes to meet with slowly moving water, it travels to the bottom. The water also gathers some amount of air and plunges to the bottom, and one sees bubbles ahead of the hydraulic jump. The fast bottom moving water current then moves to the top and is forced back to the drop structure creating an upstream current. Any passing canal can be quickly submerged and people inside may get entrapped in the submerged hydraulic jump and get drowned easily. Submerged hydraulic jumps can be prevented by constructing lips on a spillway so as to redirect the plunging nape velocity. The lips can stop bubbles of air from traveling along the bottom downstream and backflow current is reduced. The flip-lip can also cause swift downstream velocity for a safe passage of people (Subramanya, 1982).
According to Bush 2003, Engineers are good at locating the position of a hydraulic jump. They can look at the point where people pass and then check the speed of the water upstream and downstream. If the water upstream is moving very fast and/or has a spillway, the engineer can locate the position by creating a hydraulic jump just below the hydraulic structure. The same can happen in the passage downstream to reduce the risk of drowning on spillways by constructing a flip-lip. The friction between the flip-lips distort the fast moving water and enable it to flow on top rather than forming an underwater current (BONN 2009 p. 81). The Froude number is crucial because it relates the inertia of the fast moving water to the gravitational forces in the upstream. People make hydraulic jumps for different reasons and purposes. They can be industrial and recreational, internal hydraulic jumps which include the ones at abyssal fan formation and atmospheric hydraulic jumps. There are also shallow hydraulic jumps such as hydraulic jumps in one’s sink.
The hydraulic jumps are formed as a result of force of fast moving currents that slow down abruptly. They create in our day to day liquids like water in rivers. They can be dangerous if care and caution do not take place. People can build hydraulic jumps for several purposes such as recreation. The knowledge of the Froude number can enable to reduce dangers of hydraulic jumps and can help calculate the safe place to cross in rivers
Bibliography
Bush, J.W.M. & Aristoff, J.M. 2003, "The influence of surface tension on the circular hydraulic jump", Journal of Fluid Mechanics, vol. 489, pp. 229-238.
BONN, D., ANDERSEN, A. and BOHR, T., 2009. Hydraulic jumps in a channel. Journal of Fluid Mechanics, 618, pp. 71-87. Accessed on 2nd Dec 2014 From http://search.proquest.com/docview/210903018/A99544527B0B444APQ/13?accountid=1611
Holland, D.M., Rosales, R.R., Stefanica, D. & Tabak, E.G. 2002, "Internal hydraulic jumps and mixing in two-layer flows", Journal of Fluid Mechanics, vol. 470, pp. 63-83. Accessed on 2nd Dec 2014 From http://search.proquest.com/docview/1418437352/A99544527B0B444APQ/18?accountid=1611
THORPE, S.A. 2010, "Turbulent hydraulic jumps in a stratified shear flow", Journal of Fluid Mechanics, vol. 654, pp. 305-n/a. http://search.proquest.com/docview/502049046/A99544527B0B444APQ/20?accountid=1611
