Mach number is a dimensionless quantity representing the ratio of the velocity of the body to the local speed of sound.
M=V/a;
here, M is the Mach number, a is the speed of sound.
The speed of sound is variable and is different at different altitude, The body’s mach number can be different for the same velocity depending on the altitude. For example, a body traveling at 250m/s at sea level has a mach number of 0.735(taking a=340m/s) but has a mach number of 0.847 at FL350 where the a is 295m/s.
If M < 0.2–0.3 and the flow is quasi-steady and isothermal, compressibility effects will be small and simplified incompressible flow equations can be used.
While the terms "subsonic" and "supersonic," in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around M = 1 where approximations of the Navier-Stokes equations used for subsonic design actually no longer apply; the simplest explanation is that the flow locally begins to exceed M = 1 even though the freestream Mach number is below this value.
The simplest classification of the flow regime depending on the Mach number is as follows,
(I) Low Subsonic-< Mach 0.3
(II) High Subsonic-0.3–0.8
(III) Transonic- 0.8–1.2
(IV) Supersonic- 1.2–5.0
(V) Hypersonic - > Mach 5.0
When it comes to the design of transonic vehicles, Mach number is of utmost significance as Shock Phenomenon comes into picture
Credit:- https://www.quora.com/What-does-a-Mach-number-signify
M=V/a;
here, M is the Mach number, a is the speed of sound.
The speed of sound is variable and is different at different altitude, The body’s mach number can be different for the same velocity depending on the altitude. For example, a body traveling at 250m/s at sea level has a mach number of 0.735(taking a=340m/s) but has a mach number of 0.847 at FL350 where the a is 295m/s.
If M < 0.2–0.3 and the flow is quasi-steady and isothermal, compressibility effects will be small and simplified incompressible flow equations can be used.
While the terms "subsonic" and "supersonic," in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around M = 1 where approximations of the Navier-Stokes equations used for subsonic design actually no longer apply; the simplest explanation is that the flow locally begins to exceed M = 1 even though the freestream Mach number is below this value.
The simplest classification of the flow regime depending on the Mach number is as follows,
(I) Low Subsonic-< Mach 0.3
(II) High Subsonic-0.3–0.8
(III) Transonic- 0.8–1.2
(IV) Supersonic- 1.2–5.0
(V) Hypersonic - > Mach 5.0
When it comes to the design of transonic vehicles, Mach number is of utmost significance as Shock Phenomenon comes into picture
Credit:- https://www.quora.com/What-does-a-Mach-number-signify
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