Computational Fluid Dynamics Study of Swimmer's Hand Velocity, Orientation, and Shape: Contributions to Hydrodynamics

Abstract

The aim of this paper is to determine the hydrodynamic characteristics of swimmer's scanned hand models for various combinations of both the angle of attack and the sweepback angle and shape and velocity of swimmer's hand, simulating separate underwater arm stroke phases of freestyle (front crawl) swimming. Four realistic 3D models of swimmer's hand corresponding to different combinations of separated/closed fingers positions were used to simulate different underwater front crawl phases. The fluid flow was simulated using FLUENT (ANSYS, PA, USA). Drag force and drag coefficient were calculated using (computational fluid dynamics) CFD in steady state. Results showed that the drag force and coefficient varied at the different flow velocities on all shapes of the hand and variation was observed for different hand positions corresponding to different stroke phases. The models of the hand with thumb adducted and abducted generated the highest drag forces and drag coefficients. The current study suggests that the realistic variation of both the orientation angles influenced higher values of drag, lift, and resultant coefficients and forces. To augment resultant force, which affects swimmer's propulsion, the swimmer should concentrate in effectively optimising achievable hand areas during crucial propulsive phases.

The effect of finger spreading on drag of the hand in human swimming

“…A swimmer can reach a speed of v s = 2 m/s in front crawl swimming and experiences a drag force of F D = 100 N [25,33,29,16]. Assume that the stroke frequency of a complete cycle is 0.5 s −1 (propulsive phase of one arm takes 1 s) and the backward (slip) velocity of the hand with respect to the water is v h = 2.2 m/s [2,20,7,4]. Furthermore, assume that the projected area of the hand is 0.042 m 2 and that the drag coefficient C D = 1.03.…”

“…However, the Reynolds number of their simulations is small (Re = 100), where the effect of optimal spreading (a 28% increase) appears unrealistically large. Finally, in their steady state simulations for several orientations and hand models, Bilinauskaite et al [2] did not find an increase of the drag force or drag coefficient when using slightly opened fingers. However, they conclude that the maximal values of local pressure for spread fingers indicate a higher pressure force and thus a higher drag force [13,11].…”

“…In order to study the effect of the finger spreading alone, the thumb had a fixed position. Changing the thumb abduction would have changed the projected area of the hand and would have influenced the drag and lift characteristics of the hand [21,2,26,12]. The hand and forearm were digitized with 7.5 × 10 4 triangular surface elements.…”

Individual–Environment Interactions in Swimming: The Smallest Unit for Analysing the Emergence of Coordination Dynamics in Performance?

“…To investigate the impacts of swimmer movements on fluid flows, more recent CFD/PIV studies have tested models in different configurations (i.e. manipulation of head position [70], or finger spread [71][72][73][74][75]) or in full dynamic mode (during the dolphin kick [76][77][78] or the front crawl [79]). For instance, maintaining the streamlined head position might decrease drag values by 20% at high swimming speeds during glide [70].…”

Relationship between thrust, anthropometrics, and dry-land strength in a national junior swimming team

“…The swimmers' hands might be seen as the key body part responsible for the major source of the upper limbs' thrust, since their trajectory and orientation are responsible for controlling the thrust generated by the upper-limbs [13]. Thus, it is reasonable to think that it is an important performance area for optimizing swimming thrust, which could present a positive effect on swim velocity [14,15].…”