Flow-acoustic interactions in T-junctions

The flow-acoustic nature of sharp-edged T-junctions is investigated experimentally Tests are performed for a Reynolds number range of 54,000 < Re-D < 470,000. Four test cases are studied corresponding to: (a) T-junction with flow from the two branches; (b) T-junction with flow from one branch; (c) T-junction with flow into the two branches and (d) T-junction with flow into one branch. It is found that the separation bubble formed when the flow goes around the T-junction corner provides a source of turbulence excitation. For cases (c) and (d) the dimensionless pressure amplitudes of the acoustic modes reach a maximum at a Stroulial number which is in agreement with the broadband peak measured in the separation bubble. Cases (a) and (b) exhibit a different type of flow-acoustic coupling. In both cases, the maximum acoustic pressure is stronger than in Cases (c) and (d) and occurs at a Strouhal number which is different from that observed in the separation bubble. The results are compared to experimental and numerical studies from the literature.