Ship Velocity Fields

Longo, Joe; Gui, Lichuan; Stern, Fred

doi:10.1142/9789812796615_0004

Cited by 3 publications

(2 citation statements)

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“…Noteworthy is the use of integrated experiments and computations whereby the simulations guide the experiments, experiments validate the simulations, and once validated the simulations fill in the sparse experimental data for physics diagnostics and explication. Longo et al (2004) first reviewed PIV for ship velocity fields. The 26 th and 27 th ITTC Specialist Committee on Detailed Flow Measurements (ITTC, 2011 and 2014) provided a comprehensive overview of measurements for ship propulsion and maneuvering and LDV, PIV and wave-elevation measurement systems and uncertainty analysis.…”

Section: Introductionmentioning

confidence: 99%

Benchmark CFD validation data for surface combatant 5415 in PMM maneuvers – Part II: Phase-averaged stereoscopic PIV flow field measurements

et al. 2015

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Part II of this two-part paper presents CFD benchmark local flow field measurements for a surface combatant in dynamic planar-motion-mechanism (PMM) maneuvers. Phase-averaged stereoscopic particle-image-velocimetry (PIV) measurements are performed for pure sway and pure yaw maneuvers. The geometry is DTMB model 5512, a 3.048 m geosim of DTMB model 5415. The experiments aredone in a 100 m × 3 m × 3 m towing tank. The measurement system is a custom-designed towingtank maneuvering test flow-mapping system, which features a PMM for captive model testing with an integrated stereoscopic PIV. Statistical convergence error is defined and monitored by using the confidence intervalsof the mean and variance. The quality of data is also assessed by following standard uncertainty assessmentprocedures.The present experimental dataare cross-referenced with computational simulations for identification of the major vortices in the flow. The core locations and trajectories of the major vortices are traced and the flow variables at the core locationsare analyzed.The tests of both Parts I and II are sufficiently documented and detailed to be useful as experimental benchmark data for validation of computational fluid dynamicscodes.Part I presents the force/moment/motion measurements.

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Section: Introductionmentioning

confidence: 99%

Benchmark CFD validation data for surface combatant 5415 in PMM maneuvers – Part II: Phase-averaged stereoscopic PIV flow field measurements

et al. 2015

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“…According to publications on the particle image velocimetry (PIV), i.e. an image pattern tracking technique for fluid flow measurements, the uncertainties for determining the displacement of image pattern of 3232 pixels may be less than 0.1 pixels [3][4][5][6][7] that ensures the high accuracy of determining the insect body part motion. In addition, by using a high-speed imaging system, thousands of image frames can be consecutively captured with a constant time interval between frames, so that a temporal analysis of the inset body motion can be conducted.…”

Section: Introductionmentioning

confidence: 99%

An Image Pattern Tracking Algorithm for Time-resolved Measurement of Mini- and Micro-scale Motion of Complex Object

Gui

Seiner

2009

Algorithms

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An image pattern tracking algorithm is described in this paper for time-resolved measurements of mini-and micro-scale movements of complex objects. This algorithm works with a high-speed digital imaging system, which records thousands of successive image frames in a short time period. The image pattern of the observed object is tracked among successively recorded image frames with a correlation-based algorithm, so that the time histories of the position and displacement of the investigated object in the camera focus plane are determined with high accuracy. The speed, acceleration and harmonic content of the investigated motion are obtained by post processing the position and displacement time histories. The described image pattern tracking algorithm is tested with synthetic image patterns and verified with tests on live insects.

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Phase-Averaged PIV for the Nominal Wake of a Surface Ship in Regular Head Waves

Longo

Shao

Irvine

et al. 2006

Journal of Fluids Engineering

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Phase-averaged organized oscillation velocities (U,V,W) and random fluctuation Reynolds stresses (uu¯,vv¯,ww¯,uv¯,uw¯) are presented for the nominal wake of a surface ship advancing in regular head (incident) waves, but restrained from body motions, i.e., the forward-speed diffraction problem. A 3.048×3.048×100m towing tank, plunger wave maker, and towed, 2D particle-image velocimetry (PIV) and servo mechanism wave-probe measurement systems are used. The geometry is DTMB model 5415 (L=3.048m, 1∕46.6 scale), which is an international benchmark for ship hydrodynamics. The conditions are Froude number Fr=0.28, wave steepness Ak=0.025, wavelength λ∕L=1.5, wave frequency f=0.584Hz, and encounter frequency fe=0.922Hz. Innovative data acquisition, reduction, and uncertainty analysis procedures are developed for the phase-averaged PIV. The unsteady nominal wake is explained by interactions between the hull boundary layer and axial vortices and incident wave. There are three primary wave-induced effects: pressure gradients 4%Uc, orbital velocity transport 15%Uc, and unsteady sonar dome lifting wake. In the outer region, the uniform flow, incident wave velocities are recovered within the experimental uncertainties. In the inner, viscous-flow region, the boundary layer undergoes significant time-varying upward contraction and downward expansion in phase with the incident wave crests and troughs, respectively. The zeroth harmonic exceeds the steady-flow amplitudes by 5–20% and 70% for the velocities and Reynolds stresses, respectively. The first-harmonic amplitudes are large and in phase with the incident wave in the bulge region (axial velocity), damped by the hull and boundary layer and mostly in phase with the incident wave (vertical velocity), and small except near the free surface-hull shoulder (transverse velocity). Reynolds stress amplitudes are an order-of-magnitude smaller than for the velocity components showing large values in the thin boundary layer and bulge regions and mostly in phase with the incident wave.

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Ship Velocity Fields

Cited by 3 publications

References 0 publications

Benchmark CFD validation data for surface combatant 5415 in PMM maneuvers – Part II: Phase-averaged stereoscopic PIV flow field measurements

Benchmark CFD validation data for surface combatant 5415 in PMM maneuvers – Part II: Phase-averaged stereoscopic PIV flow field measurements

An Image Pattern Tracking Algorithm for Time-resolved Measurement of Mini- and Micro-scale Motion of Complex Object

Phase-Averaged PIV for the Nominal Wake of a Surface Ship in Regular Head Waves

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