Numerical investigation of fish exploiting vortices based on the Kármán gaiting model

Li, Chao; Yang, Wenjing; Xu, Xinhai; Wang, Jinyu; Miao, Wang; Xu, Liyang

doi:10.1016/j.oceaneng.2017.05.011

Cited by 31 publications

(14 citation statements)

References 31 publications

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“…It can be seen from Figure 9 that the simulation at the 200 MW load condition tends to be stable after 0.12 s, and the dominate frequency of the dynamic pressure is 139.72 Hz. The second method is based on the following empirical equation, which is commonly used to estimate the vortex shedding frequency in practical operation [34].…”

Section: Cfd Simulationsmentioning

confidence: 99%

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An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

et al. 2017

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Abstract:In this paper, a new methodology is proposed to reduce the vortex-induced vibration (VIV) and improve the performance of the stay vane in a 200-MW Francis turbine. The process can be divided into two parts. Firstly, a diagnosis method for stay vane vibration based on field experiments and a finite element method (FEM) is presented. It is found that the resonance between the Kármán vortex and the stay vane is the main cause for the undesired vibration. Then, we focus on establishing an intelligent optimization model of the stay vane's trailing edge profile. To this end, an approach combining factorial experiments, extreme learning machine (ELM) and particle swarm optimization (PSO) is implemented. Three kinds of improved profiles of the stay vane are proposed and compared. Finally, the profile with a Donaldson trailing edge is adopted as the best solution for the stay vane, and verifications such as computational fluid dynamics (CFD) simulations, structural analysis and fatigue analysis are performed to validate the optimized geometry.

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Section: Cfd Simulationsmentioning

confidence: 99%

“…The comparison results are shown in Table 4. It can be found that the SST model was not able to The second method is based on the following empirical equation, which is commonly used to estimate the vortex shedding frequency in practical operation [34].…”

Section: Cfd Simulationsmentioning

confidence: 99%

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

et al. 2017

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“…Understanding the energy‐saving strategy of fish in unsteady flow is important, with many potential applications across the fields of fisheries science, ecology and fluid dynamics (Duguay et al, 2018; Hockley, Wilson, Brew, & Cable, 2014; Li et al, 2017). Here, we have demonstrated that a combination of obstacles and flow velocity may be beneficial for fish swimming in unstable flow.…”

Section: Discussionmentioning

confidence: 99%

Effects of obstacles and flow velocity on locomotory behavior in juvenile, silver carp,Hypophthalmichthys molitrix

Shi

Tan

et al. 2020

River Research & Apps

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We currently have only a minimal understanding of energy‐saving strategies of fish in unsteady flows. In this study, we found that obstacle shape can affect swimming ability of fish: our results suggested that a half cylinder improved critical swimming speed of silver carp (Hypophthalmichthys molitrix) compared with swimming downstream of a full cylinder, square tube or for free‐flow conditions. We also discovered how silver carp alter their locomotory behavior in response to turbulent flow caused by varying flow velocities around obstacles. At a flow velocity of 1 BL/s (body length per second), the fish spent similar percentages of time between holding station and moving forward behind the half cylinder: their motions resembled freestream swimming behavior. The greatest percentage of time spent downstream of the half cylinder occurred at a flow velocity of 5 BL/s. Fish were unstable and displayed irregular body motions with large lateral displacement at 5 BL/s. However, the fish held station for a long time and moved forward steadily behind the half cylinder at 3 BL/s. In holding station behind the half cylinder, fish maintained constant tail‐beat frequency and tail‐ beat amplitude when flow velocity was increased from 1 to 3 BL/s. In moving forward behind the half cylinder, fish increased tail‐beat frequency and tail‐beat amplitude while maintaining constant ground swimming speed, swimming acceleration and ground stride when flow velocity was increased from 3 to 5 BL/s. Moreover, fish positioned their snouts in a small area approximately 1–3 BL downstream from the half cylinder at 3 BL/s. These behaviors support the hypothesis that turbulence behind a half cylinder was a suitable location for fish to conserve energy at 3 BL/s. Our results indicate that the combined effect of obstacles and flow velocity influence fish locomotory behavior, and some combinations may be beneficial to fish energy expenditure swimming in unsteady flow.

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“…OpenFOAM is a free, open source platform that not only provides us with a rich set of application solvers but also allows users to write custom solvers for specific applications based on their original solvers. It is often used to study the fluid dynamics of polymer solutions [ 35 , 36 ]. OpenFOAM is written in C++ and provides user interfaces that can describe partial differential equations in a natural language-like way, which makes it easy to extend the theoretical models of existing solvers.…”

Section: Bcfsolver Implementationmentioning

confidence: 99%

Exploring the Molecular Distributions in Dilute Polymer Solutions Using a Multi-Scale Numerical Solver

Liu

Yang

et al. 2018

Polymers

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Simulating the rheological behaviors of polymer solutions is intrinsically a multi-scale problem. To study the macroscopic and microscopic characteristics in the fluid flow of dilute polymer solutions, we designed a multi-scale solver, which couples the Brownian Configuration Fields with the macroscopic hydrodynamic governing equations. Numerical simulation results using the multi-scale solver exhibited good accordance with the macroscopic only approach. Through a scalar field D we also quantitatively studied the flow behaviours in 2D planar channels, and analyzed the correlation between the molecular distribution and the macroscopic fluid flow in polymer solutions. Our results verified the correctness of the solver, which could provide valuable guidance for multi-scale simulations of complex fluids based on OpenFOAM.

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Numerical investigation of fish exploiting vortices based on the Kármán gaiting model

Cited by 31 publications

References 31 publications

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

Effects of obstacles and flow velocity on locomotory behavior in juvenile, silver carp,Hypophthalmichthys molitrix

Exploring the Molecular Distributions in Dilute Polymer Solutions Using a Multi-Scale Numerical Solver

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