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P. Liu
From the tangent momentum equation
V t m − V
t m = 0
From the normal momentum equation
ρV n dV n = −dp
Solving jointly, we get
V n = a, V t = V
t
It is shown that the normal velocity component in front of the
Mach wave is sound velocity, and the tangential velocity through the
Mach wave is constant.
3. Expansion wave
In compressible flow, the change in density cannot be ignored. The process
of pressure and density increasing is called compression process, and the
process of pressure and density decreasing is called expansion process.
In high subsonic flow, although there are compression and expansion
processes, there is no disturbance boundary, and the disturbance can
spread to the whole flow field. In supersonic flow, both compression
and expansion processes have disturbed boundary, which is similar to the
Mach wave. This disturbed boundary is called wave front. As shown in
Fig. 2.64, for supersonic flow around the expansion angle of the wall
outside fold dδ. At the O-point, the wall is turned outward at a small
angle dδ, which enlarges the flow area. Then the O-point is a small disturbance source, and the propagation range of the disturbance is downstream
Fig. 2.64 Supersonic flow bypasses the expansion angle of microelements
P. Liu
From the tangent momentum equation
V t m − V
t m = 0
From the normal momentum equation
ρV n dV n = −dp
Solving jointly, we get
V n = a, V t = V
t
It is shown that the normal velocity component in front of the
Mach wave is sound velocity, and the tangential velocity through the
Mach wave is constant.
3. Expansion wave
In compressible flow, the change in density cannot be ignored. The process
of pressure and density increasing is called compression process, and the
process of pressure and density decreasing is called expansion process.
In high subsonic flow, although there are compression and expansion
processes, there is no disturbance boundary, and the disturbance can
spread to the whole flow field. In supersonic flow, both compression
and expansion processes have disturbed boundary, which is similar to the
Mach wave. This disturbed boundary is called wave front. As shown in
Fig. 2.64, for supersonic flow around the expansion angle of the wall
outside fold dδ. At the O-point, the wall is turned outward at a small
angle dδ, which enlarges the flow area. Then the O-point is a small disturbance source, and the propagation range of the disturbance is downstream
Fig. 2.64 Supersonic flow bypasses the expansion angle of microelements