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Flapping is an energy-demanding mode of fast animal locomotion that requires physiology, wing kinematics, and unsteady mechanics to work in unison. The trailing flow or wake is a signature of flapping mechanics, which makes it a popular candidate for visualization and analysis. While there are multiple ways to analyze wakes, we need a general framework to ensure utility of the analysis in bio-inspired flapping flight. In this article, we develop a theoretical framework to analyze the transport phenomena of wakes. To illustrate, we apply the theory to a two-dimensional modeled hovering flight comprising engineered rigid flapping plates, which vary in aspect ratio, wingbeat frequency, and the use of winglet. The results potentially explain certain observations in natural flight. [ABSTRACT FROM AUTHOR]

This document is an erratum for an article titled "On dissecting the wakes of flapping wings" published in the journal Physics of Fluids. The erratum addresses updates that need to be made to the affiliation and acknowledgments in the original publication. Specifically, the affiliation of the second author, Srikanth Goli, needs to be modified to the Applied Research Center for Metrology, Standards, and Testing (ARC-MST), Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. Additionally, an update is needed in the acknowledgments to express gratitude to the Indian Institute of Technology Kharagpur for research support. The authors of the original article are Priyam Chakraborty, Srikanth Goli, and Arnab Roy. [Extracted from the article]

In the present study, flow field around rigid flat plate wings executing main flapping motion has been studied using phaselocked two-dimensional particle image velocimetry measurements. Experiments have been conducted in water as a fluid medium for an asymmetric upper-lower stroke single degree of freedom main flapping motion. Two different aspect ratio (1.5 and 1.0) rectangular wings at 1.5 and 2.0 Hz flapping frequency in hovering flight mode (advance ratio, J=0), zero wing pitch angle, and chord-based Reynolds number of the order of 104 have been studied. Velocity field and vorticity field with λ2 criterion information have been obtained for the complete stroke in great detail to reveal the minute aspects of flow dynamics. The flow features during the downstroke and upstroke have been observed to be consistent for all four cases investigated. The predominant characteristic of the flow during downstroke and upstroke has been referred to as vortex filamentation and fragmentation phenomena. Quantities such as circulation, rate of strain, rate of rotation, and enstrophy have been studied to identity the effect of minor change in aspect ratio and flapping frequency. It is found that for higher aspect ratio wing hyperbolic behavior is predominant except for end of downstroke and beginning of upstroke where elliptic behavior is observed. For lower aspect ratio, wing elliptic behavior is predominant except for end of upstroke and beginning of downstroke where hyperbolic behavior is seen. The hyperbolic behavior became stronger at higher frequency. From enstrophy distribution it is evident that higher frequencies play a more dominant role than aspect ratio in determining the budget. [ABSTRACT FROM AUTHOR]

Abstract: Overweight is an inflammatory disease, and today''s overweight university students will be tomorrow''s overweight employees and parents; however, few studies have focused on the link between overweight and inflammation in university students. We hypothesized that students at higher body mass index (BMI) and percent body fat (BF%) would have higher blood concentrations of lipids and inflammatory biomarkers. A cross-sectional study including 110 university students was conducted at Texas Tech University. Overweight was determined by BMI using measured height and weight, and BF% was determined using bioelectric impedance analysis. Serum triglyceride and cholesterol concentrations were measured using enzymatic methods. Plasma concentrations of leptin, adiponectin, C-reactive protein (CRP), interleukin-6, and tumor necrosis factor α were measured using an enzyme-linked immunosorbent assay. Our results showed that higher BMI was associated with increased blood concentrations of CRP, leptin, and triglyceride (only in male subjects) and decreased blood adiponectin concentrations in university students. In addition, BF% was significantly correlated with blood concentrations of leptin and CRP. Female students had significantly higher blood concentrations of leptin, adiponectin, and CRP than did male students. In conclusion, blood inflammatory biomarkers, especially leptin and CRP, provide a more sensitive and accurate assessment than blood cholesterol and triglyceride for overweight individuals in this population. Leptin, adiponectin, and CRP are sex-dependent inflammatory biomarkers. [Copyright &y& Elsevier]

The objectives of this study were to examine the prevalence of assistive technology (AT) use, type of assistance used for each activity of daily living (ADL) limitation, and correlates of AT use among Native Indian aged 55 and older. Data were collected as part of a cross-sectional study of disability with 505 members of a federally recognized tribe using in-person interviewer administered surveys. Participants who reported difficulty with ADLs, including bathing, dressing, eating, transferring, walking, toileting, grooming, and getting outside, were asked about AT use. Other measures were demographics, living arrangements, receipt of personal care, Medicare and Medicaid beneficiary status, number of chronic conditions, lower body function, and personal mastery. Results indicated that 22.3% of participants aged 55 and older and 26.0% aged 65 and older reported AT use. Toileting had the largest percentage of participants who relied on AT only and getting outside had the largest percentage of participants relying on a combination of AT and personal care. Multiple variable logistic regression analysis identified receipt of personal care, having more chronic conditions, and poorer lower body function as significantly associated with higher odds of AT use. The results suggest that there is greater AT use in this sample than in same-aged adults in national samples. This greater use may be reflective of a combination of higher disability rates, cultural factors, and greater access to AT. Clinicians can use this information to identify the activities with which their patients are experiencing the most difficulty and which ones can be addressed with AT versus personal care. [ABSTRACT FROM AUTHOR]

The wake dynamics behind a sinusoidally pitching custom designed symmetrical airfoil is analyzed computationally. The effect of pitching frequency and pitching amplitude is investigated independently at a constant Reynolds number. The wake patterns are found to exhibit a transition from von Karman to reverse von Karman vortex street and from symmetric reverse von Karman vortex street to asymmetric deflected wake as established. For laminar flow under investigation, the contours of time-varying velocity fluctuations are presented. The mean profiles of velocity and the fluctuations at different locations in the wake show that the thrust wakes are generated at the expense of energy of the surrounding fluid. The temporal behavior of the flow field is analyzed using the phase plot. The time series plots of force coefficients show a periodic loading on the airfoil. Proper orthogonal decomposition (POD) analysis of drag, neutral and thrust wakes displayed the evolution of coherent structures in the flow field. The evolution of these structures portray the transitions in the wake of the airfoil. The merging of coherent structures in an asymmetric deflected wake turns out to be an efficient way of identifying the location of deflection. • The vortex pairing mechanism is identified for the deflected wake. • The time average of fluctuating quantities are evaluated to quantify flow field. • The chaotic behavior of the flow field is identified using the u − v phase plot. • Time series analysis shows the effect of frequency is more prominent on force coefficients. • The coherent structures are identified using Proper orthogonal decomposition. [ABSTRACT FROM AUTHOR]