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Numerical Simulation of Two-Phase Flow Around Flatwater Competition Kayak Design-Evolution Models

Vishveshwar R. Mantha, António J. Silva, Daniel A. Marinho, and Abel I. Rouboa

The aim of the current study was to analyze the hydrodynamics of three kayaks: 97-kg-class, single-rower, flatwater sports competition, full-scale design evolution models (Nelo K1 Vanquish LI, LII, and LIII) of M.A.R. Kayaks Lda., Portugal, which are among the fastest frontline kayaks. The effect of kayak design transformation on kayak hydrodynamics performance was studied by the application of computational fluid dynamics (CFD). The steady-state CFD simulations where performed by application of the k-omega turbulent model and the volume-of-fluid method to obtain two-phase flow around the kayaks. The numerical result of viscous, pressure drag, and coefficients along with wave drag at individual average race velocities was obtained. At an average velocity of 4.5 m/s, the reduction in drag was 29.4% for the design change from LI to LII and 15.4% for the change from LII to LIII, thus demonstrating and reaffirming a progressive evolution in design. In addition, the knowledge of drag hydrodynamics presented in the current study facilitates the estimation of the paddling effort required from the athlete during progression at different race velocities. This study finds an application during selection and training, where a coach can select the kayak with better hydrodynamics.

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Hydrodynamic Drag during Gliding in Swimming

Daniel A. Marinho, Victor M. Reis, Francisco B. Alves, João P. Vilas-Boas, Leandro Machado, António J. Silva, and Abel I. Rouboa

This study used a computational fluid dynamics methodology to analyze the effect of body position on the drag coefficient during submerged gliding in swimming. The k-epsilon turbulent model implemented in the commercial code Fluent and applied to the flow around a three-dimensional model of a male adult swimmer was used. Two common gliding positions were investigated: a ventral position with the arms extended at the front, and a ventral position with the arms placed along side the trunk. The simulations were applied to flow velocities of between 1.6 and 2.0 m·s−1, which are typical of elite swimmers when gliding underwater at the start and in the turns. The gliding position with the arms extended at the front produced lower drag coefficients than with the arms placed along the trunk. We therefore recommend that swimmers adopt the arms in front position rather than the arms beside the trunk position during the underwater gliding.

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Swimming Propulsion Forces Are Enhanced by a Small Finger Spread

Daniel A. Marinho, Tiago M. Barbosa, Victor M. Reis, Per L. Kjendlie, Francisco B. Alves, João P. Vilas-Boas, Leandro Machado, António J. Silva, and Abel I. Rouboa

The main aim of this study was to investigate the effect of finger spread on the propulsive force production in swimming using computational fluid dynamics. Computer tomography scans of an Olympic swimmer hand were conducted. This procedure involved three models of the hand with differing finger spreads: fingers closed together (no spread), fingers with a small (0.32 cm) spread, and fingers with large (0.64 cm) spread. Steady-state computational fluid dynamics analyses were performed using the Fluent code. The measured forces on the hand models were decomposed into drag and lift coefficients. For hand models, angles of attack of 0°, 15°, 30°, 45°, 60°, 75°, and 90°, with a sweep back angle of 0°, were used for the calculations. The results showed that the model with a small spread between fingers presented higher values of drag coefficient than did the models with fingers closed and fingers with a large spread. One can note that the drag coefficient presented the highest values for an attack angle of 90° in the three hand models. The lift coefficient resembled a sinusoidal curve across the attack angle. The values for the lift coefficient presented few differences among the three models, for a given attack angle. These results suggested that fingers slightly spread could allow the hand to create more propulsive force during swimming.

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Numerical Streamline Patterns at Swimmer’s Surface Using RANS Equations

Ahlem Arfaoui, Catalin Viorel Popa, Redha Taïar, Guillaume Polidori, and Stéphane Fohanno

The objective of this article is to perform a numerical modeling on the flow dynamics around a competitive female swimmer during the underwater swimming phase for a velocity of 2.2 m/s corresponding to national swimming levels. Flow around the swimmer is assumed turbulent and simulated with a computational fluid dynamics method based on a volume control approach. The 3D numerical simulations have been carried out with the code ANSYS FLUENT and are presented using the standard k-ω turbulence model for a Reynolds number of 6.4 × 106. To validate the streamline patterns produced by the simulation, experiments were performed in the swimming pools of the National Institute of Sports and Physical Education in Paris (INSEP) by using the tufts method.

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The Role of Mechanoreceptive Information in the Stability of Human Upright Posture: A Theoretical Consideration

Ge Wu and Weifeng Zhao

This study examined the role of feedback from cutaneous mechanoreceptors in the stability of human upright posture. A two-link, one degree of freedom, inverted pendulum model was constructed for the human body with ankle joint torque proportional to the delayed outputs from muscle receptors, joint receptors, and cutaneous mechanoreceptors in the foot. Theoretical analysis and numerical simulations indicated that the use of mechanoreceptive information reduced the frequency range and the maximum peak-peak value of the dynamic response of the system. However, without the use of muscle receptors, the mechanoreceptive feedback could not stabilize the system. In addition, body movement of human subjects was measured when their balanced upright posture was disturbed by a transient, forward/backward movement of a supporting platform. The loss of or change in cutaneous mechanoreceptive sense in their feet was induced by (a) having healthy subjects stand on a soft surface and (b) testing neuropathic patients with loss of vibratory sensation in their feet. The results showed significant increases in frequency range and maximum peak-peak value of ankle rotation and velocity for subjects standing on a soft (vs. hard) surface and for neuropathic patients (vs. age- and gender-matched healthy subjects).

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The Effects of Filter Cutoff Frequency on Musculoskeletal Simulations of High-Impact Movements

Stefan Sebastian Tomescu, Ryan Bakker, Tyson A.C. Beach, and Naveen Chandrashekar

. 2013 ; 38 ( 4 ): 653 – 657 . PubMed ID: 23540768 doi:10.1016/j.gaitpost.2013.02.015 23540768 10.1016/j.gaitpost.2013.02.015 22. Kar J , Quesada PM . A numerical simulation approach to studying anterior cruciate ligament strains and internal forces among young recreational women performing valgus

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The Influence of Neck Stiffness on Head Kinematics and Maximum Principal Strain Associated With Youth American Football Collisions

Janie Cournoyer, David Koncan, Michael D. Gilchrist, and T. Blaine Hoshizaki

Impacts ; 2018 : 326 – 333 . 31555774 19. Post A , Clark JM , Robertson DGE , Hoshizaki TB , Gilchrist MD . The effect of acceleration signal processing for head impact numeric simulations . Sports Eng . 2016 ; 20 ( 2 ): 111 – 119 . 10.1007/s12283-016-0219-5 20. Nelhaus G . Head

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Modeling Human Suboptimal Control: A Review

Alex Bersani, Giorgio Davico, and Marco Viceconti

MG , Whalen RT . Application of high-performance computing to numerical simulation of human movement . J Biomech Eng . 1995 ; 117 ( 1 ): 155 – 157 . PubMed ID: 7609481 doi:10.1115/1.2792264 7609481 51. Anderson FC , Pandy MG . Static and dynamic optimization solutions for gait are

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Tai Chi Is Safe and Effective for the Hip Joint: A Biomechanical Perspective

Jianwei Duan, Kuan Wang, Tongbo Chang, Lejun Wang, Shengnian Zhang, and Wenxin Niu

, M. , Tarnita , D.N. , Ionovici , N. , & Dita , R. ( 2010 ). Numerical simulations of the 3D virtual model of the human hip joint, using finite element method . Romanian Journal of Morphology and Embryology, 51 ( 1 ), 151 – 155 . PubMed ID: 20191136 doi:10.1071/RD10084 Griffin , T