Vortices are formed when 2 fluids moving in different velocities interact (OR/AND) a fluid in motion interacts a solid object. Vortices are usually formed due to flow separation and indicate that the flow is turbulent. Â
Vortices are visible in various natural phenomenon like tornados, whirlpools, etc. This article focuses on vortices in man-made machines.
Wingtip vortices form on airplanes due to the finite length of their wings. In general, lift on the wings results from low-pressure, high-velocity air moving over the top of the wing and high-pressure, low-velocity air moving below the wing. Near the wingtips, the high-pressure air is able to slip around the edge to the top of the wing, generating a vortex that then trails behind the airplane.
Over time, these counter-rotating vortices will sink downward and break up due to viscosity and instabilities induced by their proximity.
These vortices are associated both with the production of lift on the wing and with unavoidable induced drag
They can be hazardous to other (lighter) aircraft. They also contribute to downwash that decreases the effective lift of a wing. The larger an aircraft, the stronger and longer lasting its vortices; this can be a source of danger for smaller aircraft passing through the wake. If a pilot crosses one wingtip vortex and overreacts to compensate, crossing the second counter-rotating vortex can cause even greater damage.
Vortices should not be confused with engine exhaust!
Image: Wing-tip vortices mark the path of Space Shuttle Discovery as she makes her final landing.(her engine is off!)
Though not always visible, these vortices are generated by any lifting body planform and can be a major source of induced drag on the craft. Here the vortices are visible because the low pressure in the core of the vortex caused a local temperature drop below the dew point, thus causing condensation. Such vortices persist for significant lengths of time in the wake of aircraft; they are a major source of wake turbulence, which limits how frequently aircraft can take-off or land on a single runway.
Fan blade vortices in the wind turbine:
Like air plane wings, wind turbine blades generate a vortex in their wake, and the vortices from each blade can interact downstream. These intricate wakes complicate wind turbine placement for wind farms. A turbine located downstream of one of its fellows not only has a decreased power output but also has higher fatigue loads than the upstream neighbor. In other words, the downstream turbine produces less power and will wear out sooner. Researchers visualize, measure, and simulate turbine wakes and their interactions to find ways of maximizing the wind power generated.
Smoke released from the end of a test blade shows the helical pattern of a tip vortex from a horizontal-axis wind turbine. (US National Renewable Energy Laboratory testing)
Cavitation occurs in moving liquids when the local pressureâin this case, at the tip of the propellerâdrops below the vapor pressure. The fast-moving fluid transitions to a gas phase, creating a tip vortex of water vapor even though the propeller is completely submerged.
How to get rid of vortices?
Even though vortices look beautiful, they just indicate the aerodynamic inefficiency.
While the vortices in the nature cannot be controlled (as of now, and they are growing strong day by day due to global warming), vortices formed in machines can be controlled by simple modifications in the design (and operation) of the machinesâŠ..see my doodleâŠâŠ
The next generation wind turbine by Altaeros Energies.
Induced Vortices: Ever look out an airplaneâs window and wondered why a row of little fins runs along the upper side of the wing? These vortex generators help prevent a wing from stalling at high angle of attack by keeping flow attached to the surface. Airflow over the vanes creates a tip vortex that transports the higher-momentum fluid from the freestream closer to the wingâs surface, increasing the momentum in the boundary layer. As a result of this momentum exchange, the boundary layer remains attached over a greater chordwise distance. This also increases the effectiveness of trailing-edge control surfaces, like ailerons, on the wing.
In the natural world, Geese use the vortices to their advantage when flying in a V-formation, this reduces fatigue when they migrate. Some snakes use it to glide. As usual nature is the best engineer!
Vortices in the 4th state of matter!ââ
The main challenge from the beginning of magnetic fusion research has been confining the plasma long enough to keep it hot.Â
Small reactors loose heat quickly and scaling up the reactor will be costly! Therefore it is very important that we accurately predict the rate of heat transport across the confining magnetic field lines to the wall of the tokamak. This is the forefront of the ongoing fusion research. If scientists can predict the temperature at the reactor's edge, they will be able to easily predict the core temperature.
This is not a easy task. The blame goes to "Plasma turbulence" or simply call it "PLASMA VORTICES"
Turbulence in magnetized plasmas has small eddy motions, not only in the plasma "fluid" itself, but also in the electric and magnetic fields. Understanding turbulent plasma transport in tokamaks is critical to designing a full-scale commercial reactor in the future.â
Image:Â Plasma Vortices are formed in the Tokamak devices used for nuclear fusion (or creating a star on earth!)
Images and info from the blogs:Â @fuckyeahfluiddynamics and others.