Трансүндік ағын және оның әсері

Flight condition in which airflow speeds are concurrently above and below the speed of sound

Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The issue of transonic speed (or transonic region) first appeared during World War II. Pilots found as they approached the sound barrier the airflow caused aircraft to become unsteady. Research has been done into weakening shock waves in transonic flight through the use of anti shock bodies and supercritical airfoils. Transonic airspeeds see a rapid increase in drag from about Mach 0.8, and it is the fuel costs of the drag that typically limits the airspeed. Attempts to reduce wave drag can be seen on all high speed aircraft. Most notable is the use of swept wings, but another common form is a wasp waist fuselage as a side effect of the Whitcomb area rule. Transonic speeds can also occur at the tips of rotor blades of helicopters and aircraft. This puts severe, unequal stresses on the rotor blade and may lead to accidents if it occurs. It is one of the limiting factors of the size of rotors and the forward speeds of helicopters (as this speed is added to the forward sweeping [leading] side of the rotor, possibly causing localized transonics).

Issues with aircraft flight relating to speed first appeared during the supersonic era in 1941. Ralph Virden, a test pilot, crashed in a fatal plane accident. He lost control of the plane when a shock wave caused by supersonic airflow developed over the wing, causing it to stall. The slotted wall transonic tunnel was designed by NASA and allowed researchers to test wings and different airfoils in transonic airflow to find the best wingtip shape for sonic speeds. Later on, Richard Whitcomb designed the first supercritical airfoil using similar principles. Aerodynamicists struggled during the earlier studies of transonic flow because the then current theory implied that these disturbances– and thus drag– approached infinity as local Mach number approached 1, an obviously unrealistic result which could not be remedied using known methods. Many such flows also have shocks very close to the black holes. The outflows or jets from young stellar objects or disks around black holes can also be transonic since they start subsonically and at a far distance they are invariably supersonic. Supernovae explosions are accompanied by supersonic flows and shock waves. Bow shocks formed in solar winds are a direct result of transonic winds from a star. It had been long thought that a bow shock was present around the heliosphere of our solar system, but this was found not to be the case according to IBEX data published in 2012.