Global and Local Flow Modeling and Validation Experiments for Free-running ONRT Surface Combatant Maneuvering in Waves
Abstract
This proposal is for a 3-year project for global and local flow modeling and validation experiments for free-running ONRT surface combatant maneuvering in waves. The conditions will cover low and medium Froude number; regulr (3SS 5) waves; and course keeping and turning circles and zigzag maneuvers in calm water and waves withdifferent initial headings (0IC360). The experiments will build on previous data but with a focus on lower Fr and steeper wave conditions, including propeller thrust and torque measurements, which were not previously measured. The experiments will also focus on identifying/separating trends due to the effects of wavelength and height or SS and initial heading and identify conditions for the local flow measurements in consideration of validation variables and collaborative data driven/mathematical modeling and CFD studies (CNR-INM and NATOAVT 348). The local flow measurements will use programmed towed conditions based on the selected 6DoF tests; and focus on understanding the nature of the 3D vortex cross flow separations and their interactions with the free surface/waves and influences on the forces/moments. The experiments will be performed in IIHRs 40x20x3 m wave basin with 6-plunger type wave makers for regular and irregular waves using a radio controlled ONRT 3 m model. The basins overhead carriage can be used either for tracking or programmable towing using 3DoF (heave, pitch, and roll) or 4DoF (surge, heave, pitch, and roll) mounts for calm water and waves, respectively,including a controllable release system. The ONRT has twin skeg/shaft/propeller/rudder with propeller revolution and rudder angle controller. Global flow measurements include 6DoF tracking systems (carriage, visual motion capture system on the sub-carriage, and onboard gyroscope) and a dynamometer for ONRT propeller thrust and torque. Local flow measurementsinclude wave gauges, image-based free-surface mapping, and towed volumetric time resolved particle tracking velocimetry (4DPTV). A DURIP FY2021 proposal is also submitted for acquisition of equipment to support global and local flow modeling and validation experiments for free-running ONRT surface combatant maneuvering in waves. The equipment includes: (1) load cells and amplifiers for measuring propeller side forces and rudder axial and side forces and yawmoment, and metal propellers for enhanced volumetric local flow velocity measurements; (2) 6DoF soft spring mount (surge, sway and yaw linear motor) for measuring horizontal wave drift forces (X,Y) and moment (N) during the model maneuvers; and (3) instrumentation for increased accuracy of the tracking system and the wave maker controller; and lenses for increased spatialresolution 4DPTV. The requested equipment will significantly augment the validation variables for the data driven/mathematical modeling and CFD studies. The additional information from the maneuvers of the propeller side force, rudder forces and moment and especially wave drift forces and moment are critical variables for modeling. Also, the 6DoF mount removes the current mountdeficiencies of fixed yaw effects on roll motion, which is needed for local flow measurements under towed conditions. The proposed research will expedite our physical understanding and prediction capabilities for naval combatant operations in seaways under a wide range of conditions. The research enabled by the requested equipment will support the University of Iowa initiatives innaval engineering undergraduate and graduate education via Ph.D. and M/S. degrees and undergraduate and graduate courses and certificate and curricula development programs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 15, 2021
- Source ID
- N000142112060
Entities
People
- Frederick Stern
Organizations
- Office of Naval Research
- United States Navy
- University of Iowa