4,568 research outputs found
[Affidavit In Any Fact by Warren Allen Reynolds, March 16, 1964 #1]
No full textStatement by Warren Allen Reynolds concerning a man, identified by the author as Lee Harvey Oswald, running up Jefferson Street from Tenth Street
[Affidavit In Any Fact by Warren Allen Reynolds, March 16, 1964 #2]
No full textStatement by Warren Allen Reynolds concerning a man, identified by the author as Lee Harvey Oswald, running up Jefferson Street from Tenth Street
Reynolds Price
No full text37.5 x 41/48 x 52; gold and black framePortrait of Reynolds Price, author and Duke faculty membe
Decay of turbulence at high Reynolds numbers
No full textUsing the unique capabilities of the Variable Density Turbulence Tunnel at the Max Planck Institute for Dynamics and Self-Organization, we investigated virtually homogeneous and isotropic grid turbulence over a wide range of Reynolds numbers, , between and . The choice of pressurizable Sulfur Hexafluoride as a working gas makes it possible to reach extremely high Reynolds numbers without changing boundary conditions. Indeed, the Reynolds number we reached were higher than any previous classical grid wind-tunnel experiment. In this talk, we focus on the fundamental question of how fast turbulent energy decays once it has been created, and show that the Reynolds number plays no important role in setting the decay rate if it is high enough
Numerical study on effect of Reynolds number on dynamo action
No full textWe study the kinematic dynamo problem of a two dimensional turbulent flow with the third velocity component being advected as a passive scalar (2.5D flow). Both helical and nonhelical forcing is considered. The low-dimensionality of the system allows us to study it for a wide range of parameters of the system, here specifically the Reynolds number and the magnetic Reynolds number. We show that the small scale dynamo action depends on the Reynolds number. The critical magnetic Reynolds number after which small magnetic perturbations starts to grow for the nonhelical forcing case is found to be independent of the Reynolds number
날개 유연 효과가 플래핑 날개 공력 특성에 미치는 영향에 관한 실험적 연구
No full text학위논문(박사) - 한국과학기술원 : 항공우주공학과, 2021.8,[viii, 89 p. :]In this study, the unsteady aerodynamic characteristics of a flexible flapping wing undergoing hovering flight was studied. Although a rectangular wing planform was used, the wing could exhibit similar wing deformation features as natural fliersnegative wing twist and positive camber. This wing deformation was possible by designing the wing root to have an offset angle termed the slack angle. A dynamically scaled-up robotic wing model equipped with a six-axis sensor was immersed a 3-ton water tank to measure the time-varying aerodynamic forces and moments. The digital particle image velocimetry (DPIV) technique was deployed to observe the vortical structures around the wing. The rigid wing was included throughout this study to help understand the contribution of wing deformation in unsteady aerodynamics.
First, the aerodynamic load characteristics of the flexible wing revealed that the presence of wing deformation caused the pressure forces to act in the tangential and normal directions. This effect resulted in the effective angle of attack range to be beyond the 90° for the flexible wing case. To this end, the existing aerodynamic model, which was built for the rigid wing, was revised to account for wing flexibility. The newly-extracted force coefficients were well-fitted with a cubed-sine function. The model was rigorously validated with various wing kinematics, giving a good estimation of the experimental results. The estimated error was less than 5%, 6%, and 8% for the lift, drag, and moment, respectively, considering fast to moderate wing kinematics.
Based on the revised model, the optimum angle of attack for maximum lift generation was experimentally obtained for each change in slack angle. An increase in slack angle tend to increase the optimum angle of attack for maximum lift generation. However, the practical angle of attack for application in flapping wing micro-air vehicles (FWMAVs) was found to be from 75° to 85°. Generally, the flexible wing generated less drag, consumed less power, and was more efficient than the rigid wing. This was an indication that the presence of wing flexibility requires natural fliers and FWMAVs to undertake less pitching motion in order to reduce the mechanical power and increase the efficiency of their wings. In addition, there was a conspicuous phase delay between the aerodynamic characteristics of the rigid and flexible wings. The delay was found to be very sensitive to wing kinematics.
In order unravel the effects of wing kinematics on the unsteady aerodynamic characteristics, experiments were conducted with two main wing kinematic parameters, sweep duration and timing of wing rotation. This study found that the conspicuous phase delay in the flexible wing was more sensitive to the change in sweep duration than the timing of wing rotation. The transient negative lift associated with rigid wings undergoing delayed and advanced wing rotations were observed to have totally disappeared in the flexible wing case. In general, the flexible wing with symmetric and delayed wing rotations generated the highest wing efficiency. The corresponding net force vectors were observed to be tilted in an almost vertical direction for the flexible wing in comparison to the rigid wing. The vorticity distribution at the middle of stroke revealed a slight difference in the vortical structures surrounding the rigid and flexible wings in terms of proximity to the shed trailing-edge vortices (TEVs). The linearly twisted nature of the flexible wing caused the TEVs at the outboard section of the wing to be closer to the surface of the wing. The wing twist again caused the coherent leading-edge vortex (LEV) to be stable along the wingspan, and caused the vortex lift to be sustained at the outboard section of the flexible wing regardless the aspect ratio AR. The finding in this study shows that the wing twist of natural fliers could help generate and sustain sufficient amount of lift at the outboard wing sections. Thus, the spanwise deformation of their wings could be an essential wing feature for maintaining the LEV stability across the wingspan even with high AR wing.한국과학기술원 :항공우주공학과
Sheri Reynolds, 35th Annual OD Literary Festival
No full textSheri Reynolds is the author of the novels Bitterroot Landing, The Rapture of Canaan, A Gracious Plenty, Firefly Cloak, and The Sweet In-Between. Her most recent novel The Homespun Wisdom of Myrtle T. Cribb will be released this fall. Reynolds teaches creative writing and literature classes at Old Dominion University and lives in the town of Cape Charles on Virginia\u27s eastern shore
Reynolds number dependence of the dimensionless dissipation rate in stationary magnetohydrodynamic turbulence
No full textResults on the Reynolds number dependence of the dimensionless total dissipation rate C_ε are presented, obtained from medium to high resolution direct numerical simulations (DNSs) of mechanically forced stationary homogeneous magnetohydrodynamic (MHD) turbulence in the absence of a mean magnetic field, showing that C_ε -> const with increasing Reynolds number. Furthermore, a model equation for the Reynolds number dependence of the dimensionless dissipation rate is derived from the real-space energy balance equation by asymptotic expansion in terms of Reynolds number of the second- and third-order correlation functions of the Elsässer fields z± = u ± b. At large Reynolds numbers we find that a model of the form C_ε = C_ε,∞ + C/R describes the data well, while at lower Reynolds numbers the model needs to be extended to second order in 1/R in order to obtain a good fit to the data, where R is a generalised Reynolds number with respect to the Elsässer field z-
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