A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift (force generated perpendicular to the fluid flow) is substantially larger than the drag (force generated parallel to the fluid flow). If the fluid is a gas, the foil is called an airfoil or aerofoil, and if the fluid is water the foil is called a hydrofoil.
___Fin_q.jpg)
>>>PUT SHARE BUTTONS HERE<<<
👉 Foil (fluid mechanics) in the context of Fin
A fin is a thin appendage or component attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fins are also used to increase surface areas for heat transfer purposes, or simply as ornamentation.
Fins first evolved on fish as a means of locomotion. Fish fins are used to generate thrust and control the subsequent motion. Fish and other aquatic animals, such as cetaceans, actively propel and steer themselves with pectoral and tail fins. As they swim, they use other fins, such as dorsal and anal fins, to achieve stability and refine their maneuvering.
In this Dossier
Foil (fluid mechanics) in the context of Wing
A wing is a type of fin that produces both lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform. Wing efficiency is expressed as lift-to-drag ratio, which compares the benefit of lift with the air resistance of a given wing shape, as it flies. Aerodynamics includes the study of wing performance in air.
Equivalent foils that move through water are found on hydrofoil power vessels and foiling sailboats that lift out of the water at speed and on submarines that use diving planes to point the boat upwards or downwards, while running submerged. The study of foil performance in water is a subfield of Hydrodynamics.
Foil (fluid mechanics) in the context of Airfoil
An airfoil (American English) or aerofoil (British English) is a streamlined body that is capable of generating significantly more lift than drag. Wings, sails and propeller blades are examples of airfoils. Foils of similar function designed with water as the working fluid are called hydrofoils.
When oriented at a suitable angle, a solid body moving through a fluid deflects the oncoming fluid (for fixed-wing aircraft, a downward force), resulting in a force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force and can be resolved into two components: lift (perpendicular to the remote freestream velocity) and drag (parallel to the freestream velocity).
Foil (fluid mechanics) in the context of Hydroplane (boat)
A hydroplane (or hydro, or thunderboat) is a fast motorboat, where the hull shape is such that at speed, the weight of the boat is supported by planing forces, rather than simple buoyancy.
A key aspect of hydroplanes is that they use the water they are on for lift rather than buoyancy, as well as for propulsion and steering: when travelling at high speed water is forced downwards by the bottom of the boat's hull. The water therefore exerts an equal and opposite force upwards, lifting the vast majority of the hull out of the water. This process, happening at the surface of the water, is known as 'foiling'.
Foil (fluid mechanics) in the context of Hydrofoil
A hydrofoil is a lifting surface, or foil, that operates in water. They are similar in appearance and purpose to aerofoils used by aeroplanes. Boats that use hydrofoil technology are also simply termed hydrofoils. As a hydrofoil craft gains speed, the hydrofoils lift the boat's hull out of the water, decreasing drag and allowing greater speeds.