Measurement of the acoustic velocity characteristics in a standing-wave tube using out of phase PIV

The velocity fields of an acoustic standing wave in a rectangular channel are investigated. A new approach is used to measure the velocity fields using PIV. In this approach, the velocity fields are sampled at different phases in a given experimental run without synchronizing the PIV system with the excitation signal. The results show that the RMS velocities measured from this approach are in excellent agreement with the theoretical values, indicating that this new and simple approach accurately measures the RMS velocities. At the velocity antinode, the difference between the RMS measured and theoretical velocities is less than 2.4%. The results also show that this approach can be used to measure velocity fields of a standing wave in different small segments at different times and to reconstruct the entire waveform. That is, the basic statistical properties of the entire standing wave can be obtained without synchronizing PIV with the acoustic signal.