Cavitation in fluid mechanics and engineering normally refers to the phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate shock waves that may damage machinery. These shock waves are strong when they are very close to the imploded bubble, but rapidly weaken as they propagate away from the implosion. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal, causing a type of wear also called "cavitation". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior: inertial cavitation and non-inertial cavitation.
In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics and hydrodynamics. Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation.
A hull is the watertight body of a ship, boat, or flying boat. The hull may open at the top, or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, derrick, or mast. The line where the hull meets the water surface is called the waterline.
A wetsuit is a garment worn to provide thermal protection while wet. It is usually made of foamed neoprene, and is worn by surfers, divers, windsurfers, canoeists, and others engaged in water sports and other activities in or on water. Its purpose is to provide thermal insulation and protection from abrasion, ultraviolet exposure, and stings from marine organisms. It also contributes extra buoyancy. The insulation properties of neoprene foam depend mainly on bubbles of gas enclosed within the material, which reduce its ability to conduct heat. The bubbles also give the wetsuit a low density, providing buoyancy in water.
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate the free-stream flow of the fluid, and the interaction of the fluid with surfaces defined by boundary conditions. With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems. Ongoing research yields software that improves the accuracy and speed of complex simulation scenarios such as transonic or turbulent flows. Initial validation of such software is typically performed using experimental apparatus such as wind tunnels. In addition, previously performed analytical or empirical analysis of a particular problem can be used for comparison. A final validation is often performed using full-scale testing, such as flight tests.
A fish ladder, also known as a fishway, fish pass, fish steps, or fish cannon is a structure on or around artificial and natural barriers to facilitate diadromous fishes' natural migration as well as movements of potamodromous species. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps into the waters on the other side. The velocity of water falling over the steps has to be great enough to attract the fish to the ladder, but it cannot be so great that it washes fish back downstream or exhausts them to the point of inability to continue their journey upriver.
A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdom, the word can also be used for a longer artificially buried watercourse.
Competitive swimwear refers to the swimsuit, clothing, equipment, and accessories used in the aquatic sports of swimming, diving, synchronized swimming, triathlon, and water polo.
High-technology swimwear, or tech suits, are scientifically advanced materials used for swimwear in competitive water sports such as swimming and triathlon. Materials of this type are normally spandex and nylon composite fabrics with features to reduce drag against the water. The fabrics include features that increase the swimmer's glide through water and reduce the absorption of water by the suit as opposed to regular swimsuits. Additionally, the suits are extremely tight, which make the swimmers body more streamlined and help reduce the buildup of lactic acid in the body.
Swash, or forewash in geography, is a turbulent layer of water that washes up on the beach after an incoming wave has broken. The swash action can move beach materials up and down the beach, which results in the cross-shore sediment exchange. The time-scale of swash motion varies from seconds to minutes depending on the type of beach. Greater swash generally occurs on flatter beaches. The swash motion plays the primary role in the formation of morphological features and their changes in the swash zone. The swash action also plays an important role as one of the instantaneous processes in wider coastal morphodynamics.
Aquashift is a high-end technical swimsuit made by American swimwear company TYR which was released in early 2004. It incorporates years of research that TYR performed with the Center for Research and Education in Special Environments (CRESE), at the University at Buffalo. The suit sports the "Tripwire", a feature unique to TYR and the Aquashift suit, that reportedly reduces drag by a very large percentage. The suits are made of a blend of 74% polyester and 26% Lycra. The line of suits offers a bodyskin for both men and women, a kneeskin for men and women, and a regular women's suit. The price range for these suits is roughly $120 for a pair of jammers to about $380 for a bodyskin.
Ducts are conduits or passages used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. The needed airflows include, for example, supply air, return air, and exhaust air. Ducts commonly also deliver ventilation air as part of the supply air. As such, air ducts are one method of ensuring acceptable indoor air quality as well as thermal comfort.
Honeycomb structures are natural or man-made structures that have the geometry of a honeycomb to allow the minimization of the amount of used material to reach minimal weight and minimal material cost. The geometry of honeycomb structures can vary widely but the common feature of all such structures is an array of hollow cells formed between thin vertical walls. The cells are often columnar and hexagonal in shape. A honeycomb-shaped structure provides a material with minimal density and relative high out-of-plane compression properties and out-of-plane shear properties.
Turbo transmissions are hydrodynamic, multi-stage drive assemblies designed for rail vehicles using internal combustion engines. The first turbo-transmission was developed in 1932 by Voith in Heidenheim, Germany. Since then, improvements to turbo-transmissions have paralleled similar advances in diesel motors and today this combination plays a leading role worldwide, second only to the use of electrical drives.
The LZR Racer is a line of competition swimsuits manufactured by Speedo using a high-technology swimwear fabric composed of woven elastane-nylon and polyurethane. The swimsuits are made in body-length; they compress the body and trap air for buoyancy. The LZR Pro and LZR Elite were launched on 13 February 2008; the higher-priced LZR Elite was replaced by the LZR Elite 2 in early 2014. The LZR X was launched in early 2015. The technology is patented in Italy, and protected worldwide.
A swim brief or racing brief is any briefs-style male swimsuit such as those worn in competitive swimming, diving and water polo. The popularity of the Australian Speedo brand racing brief has led to the use of its name in many countries around the world to refer to any racing brief, regardless of the maker. Occasionally, the speedo genericized trademark is applied to square cut swimsuits, but in general the generic term is used in reference to swimming briefs. Swim briefs are also referred to as competition briefs, swimming trunks, bathers, togs, racer bathers, posing briefs, racing briefs, and colloquially in Australia, New Zealand, and the United Kingdom as budgie smugglers.
In fluid dynamics, hydrodynamic stability is the field which analyses the stability and the onset of instability of fluid flows. The study of hydrodynamic stability aims to find out if a given flow is stable or unstable, and if so, how these instabilities will cause the development of turbulence. The foundations of hydrodynamic stability, both theoretical and experimental, were laid most notably by Helmholtz, Kelvin, Rayleigh and Reynolds during the nineteenth century. These foundations have given many useful tools to study hydrodynamic stability. These include Reynolds number, the Euler equations, and the Navier–Stokes equations. When studying flow stability it is useful to understand more simplistic systems, e.g. incompressible and inviscid fluids which can then be developed further onto more complex flows. Since the 1980s, more computational methods are being used to model and analyse the more complex flows.
The history of competitive swimwear has been dominated by concerns over public nudity in the first half of the 20th century and by efforts to reduce water drag in the second half. Those efforts initially led swimmers to reduce the early sagging one-piece swimsuits down to briefs only. With the development of new materials that tightly fit the body and offered lower resistance to water than human skin, this trend was reversed to a complete body coverage from heels to neck and wrists. FINA banned full-body suits from competition effective from 1 January 2010, stating that it "wishes to recall the main and core principle is that swimming is a sport essentially based on the physical performance of the athlete".
Hazmat diving is underwater diving in a known hazardous materials environment. The environment may be contaminated by hazardous materials, the diving medium may be inherently a hazardous material, or the environment in which the diving medium is situated may include hazardous materials with a significant risk of exposure to these materials to members of the diving team. Special precautions, equipment and procedures are associated with hazmat diving so that the risk can be reduced to an acceptable level.
Human factors in diving equipment design are the influences of the interactions between the user and equipment in the design of diving equipment and diving support equipment. The underwater diver relies on various items of diving and support equipment to stay alive, healthy and reasonably comfortable and to perform planned tasks during a dive.
