Aircraft Wake-Vortex Decey in Ground Proximity - Physical Mechanisms and Artificial Enhancement.

Aircraft wake-vortex evolution in ground proximity is investigated numerically by means of large-eddy simulations. The simulations are performed either with a flat ground or with different modifications to the ground surface to trigger rapid vortex decay. The impact of environmental turbulence in terms of turbulent wind is taken into account, where wall-resolved and wall-modeled large-eddy simulation are performed for low- and high-Reynoldsnumber cases, respectively. To understand wake-vortex decay mechanisms in ground proximity, the interaction of primary and secondary vortices is carefully investigated. We find that vortex decay can be initiated at an earlier time and substantially accelerated with obstacles at the ground. We explain the fundamental vortex dynamics describing five characteristics of the phenomenon and quantify the decay. We demonstrate that similar effects can be achieved, employing relatively small plate lines as opposed to the original large block-shaped barriers. The obstacles trigger two kinds of so-called end effects: pressure disturbances propagating within the vortex cores and secondary vortex structures propagating along the outside of the vortex cores

Large-Eddy Simulation of Spatially Developing Aircraft Wake

Development of aircraft’s wake vortex from the roll-up until vortex decay is studied. An aircraft model and a surrounding flow field obtained from high-fidelity Reynolds Averaged Navier-Stokes simulation are swept through a ground fixed computational domain to initialize the wake. After the initialization, large-eddy simulation of the vortical wake is performed until vortex decay, i.e., 2-3 minutes after the passage of aircraft. Here, the methodology and some results from the simulations using the DLR-F6 wing-body model are presented

Effect of endurance training on excessive CO2 expiration due to lactate production in exercise

We attempted to determine the change in total excess volume of CO2 Output (CO2 excess) due to bicarbonate buffering of lactic acid produced in exercise due to endurance training for approximately 2 months and to assess the relationship between the changes of CO2 excess and distance-running performance. Six male endurance runners, aged 19–22 years, were subjects. Maximal oxygen uptake (VO2max), oxygen uptake (VO2) at anaerobic threshold (AT), CO2 excess and blood lactate concentration were measured during incremental exercise on a cycle ergometer and 12-min exhausting running performance (12-min ERP) was also measured on the track before and after endurance training. The absolute magnitudes in the improvement due to training for C02 excess per unit of body mass per unit of blood lactate accumulation (Ala−) in exercise (CO2 excess·mass−1·Δla−), 12-min ERP, VO2 at AT (AT-VO2) and VO2max on average were 0.8 ml·kg−1·l−1·mmol−1, 97.8m, 4.4 ml·kg−1· min−1 and 7.3 ml·kg−1·min−1, respectively. The percentage change in CO2 excess·mass−1·Δla− (15.7%) was almost same as those of VO2max (13.7%) and AT-VO2 (13.2%). It was found to be a high correlation between the absolute amount of change in CO2 excess·mass−1·Δla− and the absolute amount of change in AT-VO2 (r=0.94, P<0.01). Furthermore, the absolute amount of change in C02 excess·mass−1·Δla−, as well as that in AT-VO2 (r=0.92, P<0.01), was significantly related to the absolute amount of change in 12-min ERP (r=0.81, P<0.05). It was concluded that a large CO2excess·mass−1·Δla−1 of endurance runners could be an important factor for success in performance related to comparatively intense endurance exercise such as 3000–4000 m races

Vortex bursting and tracer transport of a counter-rotating vortex pair

Large-eddy simulations of a coherent counter-rotating vortex pair in different environments are performed. The environmental background is characterized by varying turbulence intensities and stable temperature stratifications. Turbulent exchange processes between the vortices, the vortex oval, and the environment, as well as the material redistribution processes along the vortex tubes are investigated employing passive tracers that are superimposed to the initial vortex flow field. It is revealed that the vortex bursting phenomenon, known from photos of aircraft contrails or smoke visualization, is caused by collisions of secondary vortical structures traveling along the vortex tube which expel material from the vortex but do not result in a sudden decay of circulation or an abrupt change of vortex core structure. In neutrally stratified and weakly turbulent conditions, vortex reconnection triggers traveling helical vorticity structures which is followed by their collision. A long-lived vortex ring links once again establishing stable double rings. Key phenomena observed in the simulations are supported by photographs of contrails. The vertical and lateral extents of the detrained passive tracer strongly depend on environmental conditions where the sensitivity of detrainment rates on initial tracer distributions appears to be low

Extracellular Water May Mask Actual Muscle Atrophy During Aging

Background.\nSkeletal muscle tissue holds a large volume of water partitioned into extracellular water (ECW) and intracellular water (ICW) fractions. As the ECW may not be related to muscle strength directly, we hypothesized that excluding ECW from muscle volume would strengthen the correlation with muscle strength.Methods.\nA total of 119 healthy men aged 20–88 years old participated in this study. Knee isometric extension strength, vertical jump, and standing from a chair were measured as indices of muscle strength and power in the lower extremities. The regional lean volume (LV), total water (TW), ICW, and ECW in the lower leg were estimated by anthropometry (skinfold and circumference measurements) and segmental multifrequency bioelectrical impedance spectroscopy (S-BIS). Then, we calculated the ECW/TW and ICW/TW ratios.Results.\nAlthough ICW and the LV index decreased significantly with age (p < .001), no significant changes in ECW were observed (p = .134). Consequently, the ECW/TW ratio increased significantly (p < .001) with age (young adult, 27.0 ± 2.9%; elderly, 34.3 ± 4.9%; advanced elderly, 37.2 ± 7.0%). Adjusting for this by including the ICW/TW ratio in our models significantly improved the correlation between the LV index and strength-related measurements and correlated with strength-related measurements independently of the LV index (p < .001).Conclusions.\nThe ECW/TW ratio increases in the lower leg with age. The results suggest that the expansion of ECW relative to ICW and the LV masked actual muscle cell atrophy with aging

Variation in ligand responses of the bitter taste receptors TAS2R1 and TAS2R4 among New World monkeys.

BACKGROUND: New World monkeys (NWMs) are unique in that they exhibit remarkable interspecific variation in color vision and feeding behavior, making them an excellent model for studying sensory ecology. However, it is largely unknown whether non-visual senses co-vary with feeding ecology, especially gustation, which is expected to be indispensable in food selection. Bitter taste, which is mediated by bitter taste receptors (TAS2Rs) in the tongue, helps organisms avoid ingesting potentially toxic substances in food. In this study, we compared the ligand sensitivities of the TAS2Rs of five species of NWMs by heterologous expression in HEK293T cells and calcium imaging. RESULTS: We found that TAS2R1 and TAS2R4 orthologs differ in sensitivity among the NWM species for colchicine and camphor, respectively. We then reconstructed the ancestral receptors of NWM TAS2R1 and TAS2R4, measured the evolutionary shift in ligand sensitivity, and identified the amino acid replacement at residue 62 as responsible for the high sensitivity of marmoset TAS2R4 to colchicine. CONCLUSIONS: Our results provide a basis for understanding the differences in feeding ecology among NWMs with respect to bitter taste