Vibration and Damping of Hydrofoils in Uniform Flow
Open Access
- Author:
- Reese, Marc Christian
- Graduate Program:
- Acoustics
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 19, 2010
- Committee Members:
- Stephen A Hambric, Thesis Advisor/Co-Advisor
Stephen A Hambric, Thesis Advisor/Co-Advisor - Keywords:
- fluid-structure interaction
structural vibration
acoustics
cantilever plate
fluid loading
added mass
hydrodynamic damping
hydrodynamic stiffness
flow visualization
water tunnel - Abstract:
- The vibration of a cantilever lifting body at low Mach number flows in water has been measured in the ARL-Penn State 12” water tunnel. Previous studies by Blake have been modified and expanded to include effects of angle of attack as well as improved modal parameter extraction from non-contact measurement capabilities for a NACA 66 aluminum hydrofoil. Fluid loaded mass, hydrodynamic stiffness and hydrodynamic damping parameters for the first two bending and torsional modes of the cantilever blade are extracted from coupled-structure Single Input, Single Output (SISO) modal analysis. The phenomenon of lock-in (which can lead to vibration amplitudes several orders of magnitude greater than normal) was measured for bending and torsional modes for several angles of attack. Flow-induced hydrodynamic stiffness was found to have a frequency dependent relationship, independent of the static lift of the blade, and increasing linearly with flow speed. Hydrodynamic damping measurements generally agree with previously derived 2-dimensional theory at flow velocities greater than the lock-in velocity.The damping of the blade throughout the measurement range remains primarily controlled by trailing edge vortex shedding. The effect of vibration on cavitation is also investigated through high-speed imagery and found to have no measurable effect for the limited number of test cases. The hydrodynamic characteristics of the blade are qualitatively examined through the use of a new surface shear-sensitive film (S3F), designed by Innovative Scientific Solutions, Incorporated (ISSI). These results are used alongside the extracted modal data to determine parameters of the hydrodynamic flow field. It is found that transition to stall has some effect on modal stiffness but little effect on damping.