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The secret of supersonic flight: Why do pilots pay so much attention to Mach number?
In the world of flight, Mach number is a key indicator, representing the ratio between flight speed and the local speed of sound. For pilots, the importance of understanding this number cannot be underestimated as it affects not only flight performance but also numerous factors related to flight safety and operations.
Mach number is a dimensionless physical quantity in fluid dynamics that reflects the relationship between the speed of fluid flowing across the boundary and the local speed of sound.
What is Mach number?
Mach number (M) is a dimensionless quantity in fluid dynamics, the formula is M = u / c, where u represents the speed of the flow and c is the speed of sound. The name of Mach number not only honors the achievements of Austrian physicist Ernst Mach, but also highlights the characteristics of fluids traveling at supersonic speeds.
Categories of Mach numbers
According to the Mach number, flight can be divided into several stages:
Subsonic(subsonic): M < 1, indicating that the flight speed is lower than the speed of sound.Transonic(Transonic): M ≈ 1, indicating that the flight is close to the speed of sound. The flow characteristics at this stage are extremely complex.Supersonic(Supersonic): M > 1, indicating flight above the speed of sound, which will cause significant pressure differences and oscillations.Hysonic(Hypersonic): M ≥ 5, the flow characteristics at this stage are extremely special, usually involving high temperatures and strong compression effects.
The impact of Mach number on flight
Pilots must always monitor the Mach number when operating an aircraft, because different Mach numbers will affect the aerodynamic performance, fuel efficiency and safety of the aircraft.
At Mach numbers that are too high or too low, pilots face a series of challenges, including control difficulties and potential mechanical failures.
Technical challenges of supersonic flight
As the flight speed increases, positive shock waves will be generated in the flow field. These waves are especially obvious during supersonic flight. When an aircraft breaks the sound barrier, a strong shock wave will appear. This is why supersonic flight emits a "sonic boom."
Mach number calculation in flight
Pilots can calculate Mach number through speed sensors and air pressure. Using certain air pressure and flow velocity data, pilots can professionally and effectively calculate the current Mach number to ensure flying within a safe range.
The formula for calculating Mach number is M = u / c, which allows pilots to quickly judge their flight status.
Future supersonic flight
With the continuous advancement of technology, the plan of supersonic flight is gradually becoming a reality. From the new generation of passenger aircraft to military fighter jets, the understanding of Mach number will become an integral part of design and control.
Between the astonishing speed and power, pilots must remain highly sensitive to the Mach number to avoid loss of control or other dangers. As future flight technology becomes more and more mature, how will the meaning of Mach number change?
