A potential-flow, deformable-body model for fluid-structure interactions with compact vorticity: application to animal swimming measurements

Peng, Jifeng; Dabiri, John O.

doi:10.1007/978-3-642-11633-9_2

Cited by 1 publication

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“…They have found out that the appearance of a new LCS is indicative of the initiation of a vortex pinch-off. Wilson et al [36] explored the utility of the LCS in low Reynolds number biological locomotion and studied the swimming model of a self-propelling jellyfish [37] via this method. They have reported that in low Reynolds number locomotion (O(1)-O(100)), the viscous diffusion rapidly smears the vorticity in the wake.…”

Section: Introductionmentioning

confidence: 99%

Lagrangian-based investigation of multiphase flows by finite-time Lyapunov exponents

2012

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Multiphase flows are ubiquitous in our daily life and engineering applications. It is important to investigate the flow structures to predict their dynamical behaviors effectively. Lagrangian coherent structures (LCS) defined by the ridges of the finite-time Lyapunov exponent (FTLE) is utilized in this study to elucidate the multiphase interactions in gaseous jets injected into water and time-dependent turbulent cavitation under the framework of Navier-Stokes flow computations.For the gaseous jets injected into water, the highlighted phenomena of the jet transportation can be observed by the LCS method, including expansion, bulge, necking/breaking, and back-attack. Besides, the observation of the LCS reveals that the back-attack phenomenon arises from the fact that the injected gas has difficulties to move toward downstream region after the necking/breaking. For the turbulent cavitating flow, the ridge of the FTLE field can form a LCS to capture the front and boundary of the re-entraint jet when the adverse pressure gradient is strong enough. It represents a barrier between particles trapped inside the circulation region and those moving downstream. The results indicate that the FTLE field has the potential to identify the structures of multiphase flows, and the LCS can capture the interface/barrier or the vortex/circulation region. Nomenclature d eDiameter of nozzle exit d s Diameter of cross-section of propulsion system d t Diameter of nozzle throat E g Total energy of gas E w Total energy of water k eff Effective thermal conductivity, k eff = k + k t k g Thermal conductivity of gas k t Turbulent thermal conductivity k w Thermal conductivity of water m + , m − Source and sink terms in the cavitation model p 0 Stagnation pressure p a Ambient pressure p e Pressure at nozzle exit Q Vortex definition criterion, Q = 1/2(|Ω| 2 −|S| 2 ) SThe rate-of strain tensor t Time t 0 Initial time t ∞ Reference time scale t * Normalized time scale, t * = t/t ∞

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Section: Introductionmentioning

confidence: 99%