Experimental and numerical investigation of ventilated cavitating flow structures with special emphasis on vortex shedding dynamics
TL;DR: In this article, the authors investigate ventilated cavitating flow structures with special emphasis on vortex shedding dynamics via combining experimental and numerical methods, and the results show that the flow patterns can be classified into two principally different categories: structures mainly with vortex shedding (namely Benard-Karman vortex street; Benard Karman vortex Street with vortex filaments and Aligned vortices) and relatively stable structures (such as Aligned Vortices with Re-entrant jet; Re-enterrant jet and Stable supercavity).
About: This article is published in International Journal of Multiphase Flow.The article was published on 2018-01-01. It has received 70 citations till now. The article focuses on the topics: Vortex shedding & Vortex ring.
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TL;DR: In this paper, the authors have carried out numerical simulations of a tip leakage cavitating flow, generated by a straight NACA0009 hydrofoil, using Lagrangian coherent structures (LCSs) combined with Schnerr-Sauer cavitation model.
205 citations
TL;DR: In this paper, the research status and development of bubble dynamics in terms of theory, numerical simulation and experimental technique are reviewed, which cover the underwater explosion bubble, airgun bubble, spark bubble, laser bubble, rising bubble, propeller cavitation bubble, water entry/exit cavityitation bubble and bubble dynamic in other fields such as shipbuilding engineering, ocean engineering, mechanical engineering, environmental engineering, chemical engineering, medical science and so on.
Abstract: Bubbles have very important applications in many fields such as shipbuilding engineering, ocean engineering, mechanical engineering, environmental engineering, chemical engineering, medical science and so on. In this paper, the research status and the development of the bubble dynamics in terms of theory, numerical simulation and experimental technique are reviewed, which cover the underwater explosion bubble, airgun bubble, spark bubble, laser bubble, rising bubble, propeller cavitation bubble, water entry/exit cavitation bubble and bubble dynamics in other fields. Former researchers have done a lot of researches on bubble dynamics and gained fruitful achievements. However, due to the complexity of the bubble motion, many tough mechanical problems remain to be solved. Based on the research progress of bubble dynamics, this paper gives the future research direction of bubble dynamics, aiming to provide references for researches related to bubble dynamics.
95 citations
TL;DR: In this paper, the authors used the k-ω SST turbulence model with the turbulence viscosity correction and the Zwart cavitation model to simulate the cavitating flow around a propeller in a non-uniform wake.
64 citations
TL;DR: In this paper, the authors reviewed the flow structure and the unsteady mechanism of the unstaidy cavitating flow in different cavitation regime, for the attached cavitation and the vortical cavitation, with both the visualization and the quantitative information.
Abstract: The flow structure and the unsteady mechanism of the unsteady cavitating flow are reviewed in this paper. The flow patterns and structures in different cavitation regime, for the attached cavitation and the vortical cavitation, are shown with both the visualization and the quantitative information. The attached cavitating flow around the Clark-Y hydrofoil and the vortical cavitating flow around the Tulin hydrofoil are considered. In particular, the phenomena such as the large-scale vortex structure and the re-entrant flow associated with the cloud cavitation, and the cavitating vortex street’s forming and crumbling are described. The evolution of the cavitation structure in the transient sheet/cloud cavity forming, along with the cavity collapse induced by the re-entrant flow and the shock wave propagation are discussed. The perspective future research of higher fidelity simulations, and the accurate identifications of the cavitating vortex structure is commented.
60 citations
TL;DR: In this paper, an experimental investigation on the internal flow of a ventilated supercavity using fog flow visualization and particle image velocimetry (PIV) measurements is presented.
Abstract: This study presents an experimental investigation on the internal flow of a ventilated supercavity using fog flow visualization and particle image velocimetry (PIV) measurements. The ventilated supercavity is generated on a backward-facing cavitator and studied in the high-speed water tunnel at St. Anthony Falls Laboratory. Fog particles are introduced into the supercavity through the ventilation line, and then illuminated by a laser sheet for flow visualizations and PIV measurements. The experiments are performed on the supercavities with two closure types, i.e. the re-entrant jet (RJ) and the twin vortex (TV), under the same water tunnel flow condition but different ventilation rates. The flow visualization revealed three distinct regions within the supercavity, including the ventilation influence region near the cavitator, the extended internal boundary layer along the liquid–gas interface and the reverse flow region occupying a large centre portion of the supercavity. The streamwise and vertical extent of the ventilation influence region, the streamwise growth of the internal boundary layer and the reverse flow within the supercavity are then quantified through PIV flow measurements. Compared to the RJ case, the results indicate that the TV supercavity yields a longer vertical extent of the ventilation influence region, a thinner internal boundary layer and a stronger reverse flow. The internal flow results suggest that at the upstream of the location of the maximum cavity diameter, the gas enters the forward flow (including the internal boundary layer and the forward moving portion of the ventilation influence region) from the reverse flow, while at the downstream of that location, the gas is stripped from the internal boundary layer and enters the reverse flow due to the increasing adverse pressure gradient in the streamwise direction. The above results are combined with visualization results of the supercavity geometry and closure patterns to further explain the influence of gas leakage mechanisms on cavity growth and closure transition. Specifically, visualization of the cavity geometry change during the RJ to TV supercavity transition indicates external flow separation associated with a critical incline angle of the bottom liquid–gas interface at the closure contributes to the onset of RJ closure. The closure visualization shows the coexistence of the toroidal vortex and twin-vortex tubes for the RJ supercavity leads to two gas leakage mechanisms: one associated with the shedding of toroidal vortices ( associated with the widening of the twin-vortex tubes, and therefore, no appreciable elongation of cavity length is observed.
57 citations
References
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5,359 citations
Book•
01 Jan 1996TL;DR: In this article, the authors present a review of rigor properties of low-dimensional models and their applications in the field of fluid mechanics. But they do not consider the effects of random perturbation on models.
Abstract: Preface Part I. Turbulence: 1. Introduction 2. Coherent structures 3. Proper orthogonal decomposition 4. Galerkin projection Part II. Dynamical Systems: 5. Qualitative theory 6. Symmetry 7. One-dimensional 'turbulence' 8. Randomly perturbed systems Part III. 9. Low-dimensional Models: 10. Behaviour of the models Part IV. Other Applications and Related Work: 11. Some other fluid problems 12. Review: prospects for rigor Bibliography.
2,920 citations
TL;DR: In this paper, a subgrid scale model is proposed for large eddy simulations in complex geometries, which accounts for the effects of both the strain and the rotation rate of the smallest resolved turbulent fluctuations.
Abstract: A new subgrid scale model is proposed for Large Eddy Simulations in complex geometries. This model which is based on the square of the velocity gradient tensor accounts for the effects of both the strain and the rotation rate of the smallest resolved turbulent fluctuations. Moreover it recovers the proper y
3 near-wall scaling for the eddy viscosity without requiring dynamic procedure. It is also shown from a periodic turbulent pipe flow computation that the model can handle transition.
2,855 citations
Book•
14 Jul 2004
TL;DR: Kato et al. as mentioned in this paper studied the dynamics of cavitation in real liquid flows and proposed a steady potential flow theory to model the cavity flow dynamics of a liquid/vapor mixture with phase change.
Abstract: -Foreword Hiroharu Kato. -Preface. Symbols. -1: Introduction - The main features of cavitating flows. 1.1. The physical phenomenon. 1.2. Cavitation in real liquid flows. 1.3. Specific features of cavitating flow. 1.4. Non-dimensional parameters. 1.5. Some historical aspects. -2: Nuclei and cavitation. 2.1. Introduction. 2.2. Equilibrium of a nucleus. 2.3. Heat and mass diffusion. 2.4. Nucleus population. References. -3: The dynamics of spherical bubbles. 3.1. Basic equations. 3.2. The collapse of a vapor bubble. 3.3. The explosion of a nucleus. 3.4. The effect of viscosity. 3.5. Non-linear oscillations of a bubble. 3.6. Scaling considerations. 3.7. Stability of a spherical interface. References. -4: Bubbles in a non-symmetrical environment. 4.1. Introduction. 4.2. Motion of a spherical bubble in a liquid at rest. 4.3. Non-spherical bubble evolution. 4.4. The path of a spherical bubble. References. Appendix to Section 4.3.3. -5: Further insights into bubble physics. 5.1. The effect of compressibility. 5.2. Bubble noise. 5.3. Some thermal aspects. 5.4. A typical numerical solution. References. Appendix to Section 5.1.3. -6: Supercavitation. 6.1. Physical aspects of supercavities. 6.2. Supercavity flow modeling using steady potential flow theory. 6.3. Typical results. 6.4. Axisymmetric cavities. 6.5. Specific problems. References. Appendix: singular behavior at detachment. -7: Partial cavities. 7.1. Partial cavities on two-dimensional foils. 7.2. Partial cavities in internal flows. 7.3. The cloud cavitation instability. 7.4. Wakes of partial cavities. 7.5. Thermal effects in partial cavitation. References. Appendix: sonic velocity in a liquid/vapor mixture with phase change. -8: Bubbles and cavities on two-dimensional foils. 8.1. Attached cavitation. 8.2. Traveling bubble cavitation. 8.3. Interaction between bubbles and cavities. 8.4. Roughness and cavitation inception. References. -9: Ventilated supercavities. 9.1. Two-dimensional ventilated supercavities. 9.2. Axisymmetric ventilated supercavities. 9.3. Analysis of pulsating ventilated supercavities. References. -10: Vortex cavitation. 10.1. Theoretical results. 10.2. The non-cavitating tip vortex. 10.3. Cavitation in a tip vortex. References. -11: Shear cavitation. 11.1. Jet cavitation. 11.2. Wake cavitation. References. -12: Cavitation erosion. 12.1. Empirical methods. 12.2. Some global results. 12.3. Basic hydrodynamic mechanisms of energy concentration. 12.4. Aggressiveness of a cavitating flow. 12.5. Insight into the material response. References. Index.
641 citations
TL;DR: In this paper, a high-order accurate numerical method based on B-splines and compared with previous upwindbiased and central finite-difference simulations and with the existing experimental data is presented.
Abstract: Flow over a circular cylinder at Reynolds number 3900 is studied numerically using the technique of large eddy simulation. The computations are carried out with a high-order accurate numerical method based on B-splines and compared with previous upwind-biased and central finite-difference simulations and with the existing experimental data. In the very near wake, all three simulations are in agreement with each other. Farther downstream, the results of the B-spline computations are in better agreement with the hot-wire experiment of Ong and Wallace [Exp. Fluids 20, 441–453 (1996)] than those obtained in the finite-difference simulations. In particular, the power spectra of velocity fluctuations are in excellent agreement with the experimental data. The impact of numerical resolution on the shear layer transition is investigated.
641 citations