Reflection of a pressure wave at the impedance change between the pipe and flexible hose

When a pressure wave travels through a pipe and encounters a change in pipe geometry or a change in pipe material, the phenomenon of reflection occurs. The reflection of the pressure wave can be explained by the principles of fluid dynamics.

  • When the pressure wave reaches the area of change (diameter, wall thickness, material properties), a portion of the wave is transmitted through, while another portion is reflected back towards the source. The reflection occurs due to the change in the acoustic impedance. The acoustic impedance is determined by the product of fluid density and sounic velocity devided by the cross sectual area.
  • The magnitude and nature of the reflection depend on various factors, such as the angle of incidence, the magnitude of the change in diameter, and the properties of the fluid.
  • In general, a sudden expansion (increase in diameter) leads to a reflection of a negative pressure wave, while a sudden contraction (decrease in diameter) causes a positive reflection.
  • The reflected wave propagates back towards the source and interacts with the incident wave. The interaction results in interference patterns, where the superposition of the incident and reflected waves leads to constructive or destructive interference. The specific interference pattern depends on the phase relationship between the incident and reflected waves.
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