Volumetric 3D PTV for Simultaneous Flow and Deformation Measurements in a Flexible Nozzle

Fluid-Structure interactions (FSI) in internal compliant flows are complex, demanding simultaneous measurement of flow and structural dynamics. Past experimental FSI studies on compliant internal flows were typically limited to planar PIV flow measurements or isolated structural measurements, lacking the ability to capture both fluid and solid motion simultaneously in 3D. We developed an experimental platform integrating volumetric, high-speed 3D particle tracking velocimetry (PTV) to capture internal flow fields and nozzle deformations concurrently. A top-hat velocity profile with low turbulence intensity (<3%) is achieved using a flow stabilizer system made using a 9:1 contraction section, honeycomb flow straightener and round hole perforated mesh arrangement to emulate ducted flow inlet conditions. 3D mapping of deformation and fluid flow using different types of beads enables the measurement of fluid structure interaction. This integrated setup enables volumetric, time-resolved tracking of nozzle deformation, and fluid motion. At increasing Reynolds numbers and decreasing structural stiffness, the system exhibits distinct self-oscillatory behavior, revealing key FSI modes. It insights into compliant nozzle behavior in underwater ducted flows & this platform serves as a high-fidelity experimental benchmark for validating future fluid–structure simulation frameworks.