Full-scale two-phase flow measurements on Athena research vessel

Johansen, James Paul; Castro, Alejandro; Carrica, Pablo M.

doi:10.1016/j.ijmultiphaseflow.2010.05.002

Cited by 39 publications

(59 citation statements)

References 17 publications

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“…Air entrainment induced by free surface turbulence is modeled as in [39] with a calibration constant S ℓ0 = 0.026 adjusted to match available experimental data for the research vessel Athena [39]. Because the model does not predict size distribution, this is an input currently taken from the experimental campaign on board of the same Athena R/V [40]. Initially, the simulation is run for 7.5 ship lengths until the heave approaches a nearly steady state.…”

Section: Bubbly Flow Around a Flat-bottom Boatmentioning

confidence: 99%

A pressure–velocity coupling approach for high void fraction free surface bubbly flows in overset curvilinear grids

Castro

Carrica

2015

Numerical Methods in Fluids

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Summary A methodology for improved robustness in the simulation of high void fraction free surface polydisperse bubbly flows in curvilinear overset grids is presented. The method is fully two‐way coupled in the sense that the bubbly field affects the continuous fluid and vice versa. A hybrid projection approach is used in which staggered contravariant velocities at cell faces are computed for transport and pressure–velocity coupling while the momentum equation is solved on a collocated grid arrangement. Conservation of mass is formulated such that a strong coupling between void fraction, pressure, and velocity is achieved within a partitioned approach, solving each field separately. A pressure–velocity projection solver is iterated together with a predictor stage for the void fraction to achieve a robust coupling. The implementation is described for general curvilinear grids detailing particulars in the neighborhood to overset interfaces or a free surface. A balanced forced method to avoid the generation of spurious currents is extended for curvilinear grids. The overall methodology allows simulation of high void fraction flows and is stable even when strong packing forces accounting for bubble collisions are included. Convergence and stability in one‐dimensional (1D) and two‐dimensional (2D) configurations is evaluated. Finally, a full‐scale simulation of the bubbly flow around a flat‐bottom boat is performed demonstrating the applicability of the methodology to complex problems of engineering interest. Copyright © 2015 John Wiley & Sons, Ltd.

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Section: Bubbly Flow Around a Flat-bottom Boatmentioning

confidence: 99%

A pressure–velocity coupling approach for high void fraction free surface bubbly flows in overset curvilinear grids

Castro

Carrica

2015

Numerical Methods in Fluids

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“…This phenomenon has affected the acoustic surveys for many years [Dalen et al (1981)] and is still a significant issue , Shabangu et al (2014)]. The reason is that neither towing tank trials nor numerical simulations [Moraga et al (2008)] are able to properly address this phenomenon [Johansen (2010)]. The experimental characterization of bubble generation by the breaking bow waves of a ship are scarse.…”

Section: Introductionmentioning

confidence: 99%

A 3D study of the bubble sweep-down phenomenon around a 1/30 scale ship model

Mallat

Germain

Billard

et al. 2018

European Journal of Mechanics - B/Fluids

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The bubble sweep-down phenomenon around oceanographic research vessels generates acoustic disturbances. A specific experimental protocol in a wave and current circulating tank is used to study this phenomenon around a 1/30 scale ship model in a configuration with current, waves and ship motions. 3D visualizations of the bubble clouds and Stereo-PIV (Particle Image Velocimetry) measurements results, both obtained in the bow vicinity of the ship model, are presented in this paper. The behaviour of the breaking wave with bubble generation is studied and the spatial evolution of the bubble clouds is investigated. It is demonstrated that the bubble cloud generation is mainly conditioned by the ascending vertical velocity of the flow near the bow. It is observed that the bubble clouds are propagated in the flow direction with a horizontal expansion which is non negligeable, reaching a close position to the hull. The overall results provide new elements for the study and the understanding of the phenomenon compared with previous 2D studies. Highlights ► Air entrainment is studied around a 1/30 Scale Ship Model. ► 3D bubble cloud characteristics are determined. ► PIV measurements and POD analysis allow to study the air bubble generation.

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“…In Athena R/V, measurements by Terrill et al (2005) and Johansen et al (2010) show large numbers of bubbles well below 100 in diameter coming from below the hull at the stern. For the Kann boat used in this work, advancing at 18 knots, the dissipation rate obtained from numerical simulations is shown in Fig.…”

Section: Turbulent Breakupmentioning

confidence: 93%

“…The fiber tips are made using an abrasive manufacturing technique that was pioneered by Johansen et. al.…”

Section: Details Of Probe Manufacturingmentioning

confidence: 99%

“…Limited studies have been performed in the near field of a ship, where the bubble sources are, and none within the boundary layer at full scale. Johansen et al (2010) performed experimental measurements of the bubbly flow on the full scale research vessel Athena II. The authors focused on two-phase quantities aft of the breaking bow wave, the starboard masker and at the stern.…”

Section: Introductionmentioning

confidence: 99%

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Local optical phase detection probes with an application to a high speed boundary layer

Perret¹

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This thesis presents the continued development of micro optical phase detection instrumentation capable of measuring void fraction, interfacial area density, interfacial velocity and bubble sizes and their application to measurements in a high speed boundary layer. The instrumentation consists of micro sized sapphire tipped probes tailored to measure in the twophase flow of air bubbles in water. Probe tips with geometries intended to maximize field life while minimizing intrusiveness were designed, fabricated and characterized. The characterization revealed that the active region of a probe tip can go beyond the highly sensitive 45 degree tip. Controlling the active length of the tips can be achieved through a combination of taper angles and 45 degree tip size, with larger tips having shorter active lengths. The full scale bubbly flow measurements were performed on a 6 flat bottom survey boat. The aforementioned quantities were measured on bubbles naturally entrained at the bow of the boat. Probes were positioned at the bow of the boat, near the entrainment region and at the stern where the bubbles exit after having interacted with the high shear turbulent boundary layer. Experiments were conducted in fresh water, at the Coralville Lake, IA, and salt water, at the St. Andrews Bay and Gulf Coast near Panama City, FL. The results indicate that the bubbles interact significantly with the boundary layer. At low speeds, in fresh water, bubble accumulation and coalescence is evident by the presence of large bubbles at the stern. At high speeds, in both fresh and salt water, bubble breakup dominates and very small bubbles are produced near the hull of the boat. It was observed that salt water inhibits coalescence, even at low boat speeds. Void fraction was seen to increase with boat speeds above 10 knots and peaks near the wall. Bubble velocities show slip with the wall at all speeds and exhibit large RMS fluctuations, increasing near the wall.

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Full-scale two-phase flow measurements on Athena research vessel

Cited by 39 publications

References 17 publications

A pressure–velocity coupling approach for high void fraction free surface bubbly flows in overset curvilinear grids

A pressure–velocity coupling approach for high void fraction free surface bubbly flows in overset curvilinear grids

A 3D study of the bubble sweep-down phenomenon around a 1/30 scale ship model

Local optical phase detection probes with an application to a high speed boundary layer

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