Vertical force acting on partly submerged spindly cylinders

Zhang, Xinbin; Yan, Jihong; Zhao, Jie; Wang, Yanan; Pan, Qinmin

doi:10.1063/1.4871695

Cited by 13 publications

(12 citation statements)

References 28 publications

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“…As shown by Arslan et al (2013), Zhang et al (2014) and by Arrighi et al (2015), lift force can also play a significant role for partly submerged objects. The average density of the human body (ρ P = 1062 kg m −3 ) is generally assumed equal to the density of muddy water; thus, ρ P is substituted with ρ in Eq.…”

Section: Dimensionless Mobility Parametersmentioning

confidence: 99%

Hydrodynamics of pedestrians' instability in floodwaters

Arrighi

Oumeraci

Castelli

2017

Hydrol. Earth Syst. Sci.

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Abstract. People's safety is the first objective to be fulfilled by flood risk mitigation measures, and according to existing reports on the causes of casualties, most of the fatalities are due to inappropriate behaviour such as walking or driving in floodwaters. Currently available experimental data on people instability in floodwaters suffer from a large dispersion primarily depending on the large variability of the physical characteristics of the subjects. This paper introduces a dimensionless mobility parameter θ P for people partly immersed in flood flows, which accounts for both flood and subject characteristics. The parameter θ P is capable of identifying a unique threshold of instability depending on a Froude number, thus reducing the scatter of existing experimental data. Moreover, a three-dimensional (3-D) numerical model describing the detailed geometry of a human body and reproducing a selection of critical pairs of water depth and velocity is presented. The numerical results in terms of hydrodynamic forces and force coefficients are analysed and discussed. Both the mobility parameter θ P and the numerical results hint at the crucial role of the Froude number and relative submergence as the most relevant dimensionless numbers to interpret the loss of stability. Finally, the mobility parameter θ P is compared with an analogous dimensionless parameter for vehicles' instability in floodwaters, providing a new contribution to support flood risk management and educating people.

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Section: Dimensionless Mobility Parametersmentioning

confidence: 99%

Hydrodynamics of pedestrians' instability in floodwaters

Arrighi

Oumeraci

Castelli

2017

Hydrol. Earth Syst. Sci.

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“…Previous studies showed that decreasing the leg center distance will decrease the maximum lift force [13]. We have numerically discussed how leg center distance affects the lift force in [12], and found that for the legs used in this work, the effect is negligible when the leg center distance is larger than 10 mm. The lifting force obtained by the supporting legs will be discussed in Section 3.…”

Section: A Supporting Mechanismmentioning

confidence: 59%

“…7 (a). Considering that the leg center distance has little effect on the lifting force when it is larger than 10 mm [12], this problem can be treated as a single-leg one and thus the lifting force Fvl is calculable by solving Young-Laplace equation [5]. Fig.…”

Section: Force Modelingmentioning

confidence: 99%

“…Water strider, a very common insect that lives on water, has attracted attention of researchers from many fields, such as biology, material, physics and engineering due to its superhydrophobic skin and agile water-surface locomotion [1], [2]. At present, relevant research mainly focuses on the following four aspects: (1) water strider's superhydrophobicity and water-surface locomotion [3], [4], (2) biomimetic superhydrophobic materials [5]- [8], (3) fluid dynamics at the air-water interface [9]- [12], and (4) water strider-inspired water-walking robots [5], [13]- [20]. Among them, miniature/micro water-walking robots have become an active area of study because of their potential to carry out various aquatic tasks such as water quality monitoring, aquatic search and rescue.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A miniature surface tension-driven robot mimicking the water-surface locomotion of water strider

Zhang

Yan

Zhao

et al. 2015

2015 IEEE International Conference on Robotics and Automation (ICRA)

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Aiming at mimicking water strider's water-surface locomotion, this study proposes a new miniature surface tension-driven robot. A key feature of this robot is that its actuating legs possess ellipse-like spatial trajectories like water strider by using a cam-link mechanism, and never pierces water surface when rowing. A set of simple models and equations are proposed to analyze the interaction forces between leg and water as well as the critical condition for a leg penetrating a water surface. The final fabricated robot weights about 3.9 g with a load capacity of 5.6 g. By controlling the motions of actuating legs, the robot can freely and stably walk on water with different gaits. The maximum forward and turning speeds of the robot are measured as 16 cm/s and 23 °/s, respectively. Moreover, a similarity analysis with Bond Number and Weber Number reveals that the locomotion of this robot is quite analogous to that of a water strider: surface tension force dominates the lifting force and plays a major role in the propulsion.

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“…where C D and C l are the drag and lift coefficient respectively. As shown by Arslan et al (2013), Zhang et al (2014) and by Arrighi et al (2015), lift force can also play a significant role for partly submerged objects. The average density of the human body (ρ P = 1062 kg m −3 ) is generally assumed equal to the density of muddy water; thus, ρ P is substituted with ρ in Eq.…”

Section: Arrighi Et Al: Hydrodynamics Of Pedestrians' Instabilitymentioning

confidence: 91%

Hydrodynamics of pedestrians' instability in floodwaters

Arrighi¹,

Oumeraci²,

Castelli³

2016

Preprint

View full text Add to dashboard Cite

Abstract. People safety is the first objective to be fulfilled by flood risk mitigation measures and according to existing reports on the causes of casualties, most of the fatalities is due to inappropriate behaviors like walking or driving in floodwaters. Currently available experimental data on people instability in floodwaters suffer of a large scatter primarily depending on the large variability of physical characteristics of the subjects. This paper introduces a dimensionless mobility parameter θP for people partly immersed in flood flows, which accounts for both flood and subject characteristics. The parameter θP is capable of identifying a unique threshold of instability depending on Froude number thus overcoming the scatter of existing experimental data. Moreover, a 3D numerical model describing a detailed geometry of a human body and reproducing a selection of critical pairs of water depth and velocity is presented. The numerical results in terms of hydrodynamic forces and force coefficients are analyzed and discussed. Both the mobility parameter θP and the numerical results hint the crucial role of Froude number and relative submergence as the most relevant dimensionless numbers to interpret the loss of stability. Finally, the mobility parameter θP is compared with an analogous dimensionless parameter for vehicles instability in floodwaters, providing a new contribution to support flood risk management and people education.

show abstract

Vertical force acting on partly submerged spindly cylinders

Cited by 13 publications

References 28 publications

Hydrodynamics of pedestrians' instability in floodwaters

Hydrodynamics of pedestrians' instability in floodwaters

A miniature surface tension-driven robot mimicking the water-surface locomotion of water strider

Hydrodynamics of pedestrians' instability in floodwaters

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