Large eddy simulation of transitional separated flow over a low Reynolds number cambered airfoil

Published by the ASMEThe accurate simulation of the aerodynamic behavior of low Reynolds number (Re) cambered airfoils requires the ability to capture the transitional separated boundary layer (BL) that occurs naturally on the surface of the airfoil. In this study, simulations are performed using a modern cambered airfoil designed for use in low Re applications, which are an advancement from previous studies using flat plate geometries or symmetric NACA airfoils. The cambered SD 7037 airfoil is simulated using wall-resolved large eddy simulation (LES) at a modest Re of 4.1×10⁴ and at 1 deg, 5 deg, and 7 deg angles of attack (AOAs), with results validated against experimental data. Simulated predictions of pressure and skin friction coefficients clearly capture the correct location of the laminar separated bubble (LSB) which forms during the natural BL transition process. Sensitivity to elevated inflow turbulence is found to cause early BL reattachment at higher AOAs without impacting the location of BL separation. An integral BL analysis verifies the accuracy of the simulated velocity profiles against experimental values. The scale of horseshoe structures visualized in the transitional BL is larger in comparison to airfoil chord length than what is seen in previous simulations at Re of the order of 10⁵, which highlights the importance of investigating cambered airfoils at a modest Re.Natural Sciences and Engineering Research Council of Canada, Award No. RGPIN-03974-2017 || Natural Sciences and Engineering Research Council of Canada, CGS-D || Ontario Graduate Scholarship Progra

Predicting the probability of falls in community-dwelling elderly individuals using the trail-walking test

Background Falling is a common problem in the fast-growing elderly population. Multitasking or engaging in two or more activities at the same time is common in daily living. Objective To determine the usefulness of the trail-walking test (TWT) for predicting a fall in community-dwelling elderly individuals. Methods This was a prospective study in which the TWT was used to evaluate the risk of falling among a group of community-dwelling elderly individuals (n = 171) with a mean age of 80.5 ± 5.6 years. The following tests were conducted: TWT, trail-making test (TMT), timed-up-and-go test (TUG), functional reach (FR) test, one-leg standing (OLS) test, and 10-m walking time test. Test–retest reliability was assessed by repeating the TWT within 2 weeks of the first trial, and there was a 1-year follow-up. Stepwise logistic regression analysis was used to analyze whether the TWT, TMT, TUG, FR, OLS, or 10-m walking tests predicted falling. Results The test–retest reliability of TWT was high (intraclass correlation coefficient 0.945, p < 0.001). Fifty-nine participants (34.5%) had reported a fall during the year preceding the 1-year follow-up. The stepwise logistic regression analysis revealed that only the TWT was significantly related to falling (odds ratio 1.160, 95% confidence interval 1.107–1.214; p < 0.001). In total, 77.8% of cases were correctly classified. Conclusion When reliability and validity were considered, the TWT was most useful test of those evaluated for assessing the risk of fall among our elderly cohort