Research Progress of Bobsleigh Aerodynamics / 医用生物力学

The aerodynamic characteristics of bobsleigh play a very important role in the result of the race. In order to improve the performance, it is necessary to optimize the bobsleigh aerodynamics and reduce its aerodynamic drag as much as possible. Foreign scholars has mainly used computational fluid dynamics (CFD) numerical simulation, wind tunnel experiments and other methods to study the aerodynamic characteristics and optimize drag reduction method, but the relevant research has not yet been carried out in China. In order to have a clear understanding of the technical requirements of bobsleigh aerodynamic optimization and drag reduction, the research result of bobsleigh aerodynamics in recent 20 years have been systematically combed, mainly including numerical simulations and wind tunnel experiments of aerodynamic optimization of bobsleigh body shape and athletes’ positions and attitudes in the bobsleigh, and the possible future development direction of bobsleigh aerodynamics research has been put forward: the systematic study of bobsleigh aerodynamics optimization and comprehensive assessment of bobsleigh aerodynamic drag reduction effects; the study on the interaction between athlete glide control and bobsleigh aerodynamics. These studies will provide an important scientific guidance for the optimization and improvement of bobsleigh sports equipment and the daily training of athletes.

Mechanical behavior of bionic drag reduction needle during puncturing process / 医用生物力学

Objective To design a kind of bionic drag reduction needle and investigate its mechanism of painless injection. Methods Based on the analysis of mosquito's mouthpart structure, two types of bionic drag reduction injector needles, sawtooth needle and stripe needle, were designed with the painless feature as mosquito's blood-sucking action. The injection processes of normal smooth needle and two bionic drag reduction injector needles were simulated by using explicit kinetic software LS-DYNA, and analyzed the pain-relief mechanism of bionic drag reduction needles. Results Through contrast and analysis on the stress contour, internal energy curves and resistance curves of both the smooth needle and bionic needles during the puncturing process in soft tissue, the bionic needle was found to have obvious drag reduction effects. The drag reduction rate of the saw-tooth needle and stripe needle was 23.48% and 31.57%, respectively. Conclusions The bionic needles can minimize the friction resistance to achieve the painless injection by drag reduction, and its effect is determined by the structure and shape of the bionic needle.

Drag reduction by polyethylene glycol in the tail arterial bed of normotensive and hypertensive rats

This study was designed to evaluate the effect of drag reducer polymers (DRP) on arteries from normotensive (Wistar) and spontaneously hypertensive rats (SHR). Polyethylene glycol (PEG 4000 at 5000 ppm) was perfused in the tail arterial bed with (E+) and without endothelium (E-) from male, adult Wistar (N = 14) and SHR (N = 13) animals under basal conditions (constant flow at 2.5 mL/min). In these preparations, flow-pressure curves (1.5 to 10 mL/min) were constructed before and 1 h after PEG 4000 perfusion. Afterwards, the tail arterial bed was fixed and the internal diameters of the arteries were then measured by microscopy and drag reduction was assessed based on the values of wall shear stress (WSS) by computational simulation. In Wistar and SHR groups, perfusion of PEG 4000 significantly reduced pulsatile pressure (Wistar/E+: 17.5 ± 2.8; SHR/E+: 16.3 ± 2.7 percent), WSS (Wistar/E+: 36; SHR/E+: 40 percent) and the flow-pressure response. The E- reduced the effects of PEG 4000 on arteries from both groups, suggesting that endothelial damage decreased the effect of PEG 4000 as a DRP. Moreover, the effects of PEG 4000 were more pronounced in the tail arterial bed from SHR compared to Wistar rats. In conclusion, these data demonstrated for the first time that PEG 4000 was more effective in reducing the pressure-flow response as well as WSS in the tail arterial bed of hypertensive than of normotensive rats and these effects were amplified by, but not dependent on, endothelial integrity. Thus, these results show an additional mechanism of action of this polymer besides its mechanical effect through the release and/or bioavailability of endothelial factors.