Bend radius

About: Bend radius is a research topic. Over the lifetime, 3303 publications have been published within this topic receiving 35415 citations. The topic is also known as: minimum bend radius.

Transpiration cooling for a vehicle with low radius leading edges

Abstract: A transpiration cooling system for avoiding overheating of an airfoil is provided The airfoil is provided with a plurality of apertures and a source of pressurized fluid for providing a flow of fluid through the apertures to establish an aerodynamic radius The aerodynamic radius of curvature of leading edge is sufficiently greater than the mechanical radius of curvature of the leading edge that peak heat flux is independent of the mechanical radius of curvature The mechanical radius of curvature is preferably less than 50% of the aerodynamic radius of curvature during hypersonic operation Preferably the mechanical radius of curvature is the smallest allowed by the fabrication method (ie, a knife edge), such as being less than about 002 inches, preferably less than about 001 inches The transpiration blowing rate can be adjusted so that the blowing rate and aerodynamic radius of curvature are relatively low except during periods of maximum heat flux, such as the shock-on-lip point Since the mechanical radius of curvature is effectively zero, control of the aerodynamic radius of curvature provides complete control of peak heat flux By adjusting blowing rate to the minimum necessary at any given velocity, transpiration consumption, drag and fuel injection are reduced or eliminated

The three-dimensional structure of swirl-switching in bent pipe flow

Abstract: Swirl-switching is a low-frequency oscillatory phenomenon which affects the Dean vortices in bent pipes and may cause fatigue in piping systems. Despite thirty years worth of research, the mechanism that causes these oscillations and the frequencies that characterise them remain unclear. Here we show that a three-dimensional wave-like structure is responsible for the low-frequency switching of the dominant Dean vortex. The present study, performed via direct numerical simulation, focuses on the turbulent flow through a 90 \degree pipe bend preceded and followed by straight pipe segments. A pipe with curvature 0.3 (defined as ratio between pipe radius and bend radius) is studied for a bulk Reynolds number Re = 11 700, corresponding to a friction Reynolds number Re_\tau \approx 360. Synthetic turbulence is generated at the inflow section and used instead of the classical recycling method in order to avoid the interference between recycling and swirl-switching frequencies. The flow field is analysed by three-dimensional proper orthogonal decomposition (POD) which for the first time allows the identification of the source of swirl-switching: a wave-like structure that originates in the pipe bend. Contrary to some previous studies, the flow in the upstream pipe does not show any direct influence on the swirl-switching modes. Our analysis further shows that a three- dimensional characterisation of the modes is crucial to understand the mechanism, and that reconstructions based on 2D POD modes are incomplete.

Surface plasmon polariton propagation around bends at a metal–dielectric interface

Abstract: We analyze theoretically the propagation of surface plasmon polaritons about a metallic corner with a finite bend radius, using a one-dimensional model analogous to the scattering from a finite-depth potential well. We obtain expressions for the energy reflection and transmission coefficients in the short wavelength limit, as well as an upper bound for the transmittance. In certain cases we find that propagation on nonplanar interfaces may result in lower losses than on flat surfaces, contrary to expectation. In addition, we also find that the maximum transmittance depends nonmonotonously on the bend radius, allowing increased transmission with decreasing radius.

Behavior of bent bar anchorages.

Abstract: The object of the study was to examine some of the factors which influence the anchorage capacities of bent deformed reinforcing bars. Eighty specimens containing bars bent to different geometric configurations were tested to determine the effect of bend length, angle included in the bend, inside radius of bend, and bar diameter on the deformation and strength of hooked bar anchorages. Of primary interest was the measurement of slip between the bar and the concrete at several points along the anchored bar. the load-slip curves obtained were used to compare the performances of different bar geometries. The results indicated that at a given bar stress, the longer the angle of bend or the smaller the radius of bend, the greater will be the slip. Ultimate strength of hooked bar anchorages is about the same as that of straight bars. For practical joint design detailing, the results indicate that 90 deg hooks are preferable to 180 deg hooks. To reduce slip the radius of the hook should be as large as practical. /Author/