而受脈衝流衝擊後，管道中流體流速變化的結果顯示，流體在脈衝流出口上方有加速情形，而在管道下游處有減速情形產生，且均勻流流速在3 m/s時，管道中流體速度變化情形最為明顯。當均勻流流速愈大，受脈衝流所造成的影響愈不明顯。 This thesis studied the influence of the acoustic excitation upon velocity distributions in a duct flow. A low-speed wind tunnel was used to create a laminar flow. An oscillating flow induced by sound wave from a speaker installed on the bottom wall of the test section was introduced to interact with the main flow.
Various sound wave frequencies and flow velocities were applied in the experiment. Velocity distributions, turbulent distributions were measured using Hot-Wire Anemometry. The controlling parameters included laminar flow velocity, sound wave frequency and sound wave amplitude.
The results showed that the interaction of the tunnel flow and the pulse flow was affected by the frequency of the acoustic driver. The flow velocity was increased at the entrance of the pulse flow, but was decreased at down stream. The disturbance caused by the pulse flow was not obvious when main flow velocity was increased.
