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Patro S.K.,KIIT University | Panneer Selvam R.,University of Arkansas | Bosch H.,Aerodynamics Laboratory
Engineering Structures | Year: 2013

Design of suspension bridge span is known to be very challenging, particularly considering its stability against wind flow. Traditionally, analysis of bridge section is done using wind tunnel and is very time consuming, with normal experimentation and modeling works requiring minimum 6-8. weeks. To reduce cost and time requirements of wind tunnel experiments, as an alternate approach, wind flow around bridges are investigated by application of computer modeling. One challenging aspect of computational approach is to solve the Navier-Stokes (NS) equations accurately. In the present work, automatic mesh generation technique is used to transfer the continuous fluid flow into discrete numerical data, followed by use of h-adaptive technique. The adaptive simulation is carried out using two posteriori error estimations, which are based on the velocity gradient and vorticity. The current study uses the wind flow over the Great Belt East Bridge (GBEB) as a case study. © 2012 Elsevier Ltd.

Popov A.V.,Ecole de Technologie Superieure of Montreal | Popov A.V.,Laboratory of Research in Active Controls | Grigorie L.T.,Ecole de Technologie Superieure of Montreal | Grigorie L.T.,Laboratory of Research in Active Controls | And 6 more authors.
Journal of Aircraft | Year: 2010

In this paper, wind-tunnel results of a real time optimization of a morphing wing in the wind tunnel for delaying the transition toward the trailing edge are presented. A morphing rectangular finite aspect ratio wing, having a wind tunnel experimental airfoil reference airfoil cross section, was considered, with its upper surface made of a flexible composite material and instrumented with Kulite pressure sensors and two smart memory alloys actuators. Several wind-tunnel test runs for various Mach numbers, angles of attack, and Reynolds numbers were performed in the 6' × 9' wind tunnel at the Institute for Aerospace Research at the National Research Council Canada. Unsteady pressure signals were recorded and used as feedback in real time control while the morphing wing was requested to reproduce various optimized airfoils by changing automatically the two actuators' strokes. This paper shows the optimization method implemented into the control software code that allows the morphing wing to adjust its shape to an optimum configuration under the wind-tunnel airflow conditions. Copyright © 2009.

Jones A.R.,University of Cambridge | Jones A.R.,Aerodynamics Laboratory | Babinsky H.,University of Cambridge | Babinsky H.,Aerodynamics Laboratory
Journal of Aircraft | Year: 2010

The rotating wing experiment is a fully three-dimensional simplification of the flapping-wing motion observed in nature. The spanwise velocity gradient and the wing starting and stopping acceleration that exist on an insectlike flapping wing are generated by the rotational motion of a finite-span wing. The flow development around a rotating wing at Re = 60; 000 has been studied using high-speed particle image velocimetry to capture the unsteady velocity field. Lift and drag forces have been measured for several different sets of wing kinematics and angles of attack. The lift curve shape was similar in all cases. A transient high lift peak, approximately 1.5 times the quasi-steady value, occurred in the first chord length of travel, and it was caused by the formation of a strong attached leading-edge vortex. This vortex then separated from the leading edge, resulting in a sharp drop in lift. As weaker leading-edge vortices continued to form and shed, lift values recovered to an intermediate value. The circulation of the leading-edge vortex has been measured and agrees well with the force data. Wing kinematics had only a small effect on the aerodynamic forces produced by the waving wing. In the early stages of the wing stroke, the velocity profiles with low accelerations affected the timing and the magnitude of the lift peak, but at higher accelerations, the velocity profile was insignificant. Copyright © 2010 by A. R. Jones.

Takami H.,Aerodynamics Laboratory | Kikuchi K.,Aerodynamics Laboratory
Quarterly Report of RTRI (Railway Technical Research Institute) (Japan) | Year: 2010

The authors performed laboratory experiments and field measurements to investigate low-frequency noise generated in wayside environments from high-speed train running. The results indicated the following three types of low-frequency sound sources: pressure fields around the nose and tail parts of the train, low-frequency acoustic pressure waves aerodynamically caused by the train itself, and noise radiation from vibrating concrete railway viaducts. Measurements conducted in a higher-speed section revealed that the major sound source of low-frequency noise in the far field was aerodynamically generated unsteady flow, which is analogous to a line source.

Jones A.R.,University of Cambridge | Jones A.R.,Aerodynamics Laboratory | Ford C.W.P.,University of Cambridge | Ford C.W.P.,Aerodynamics Laboratory | And 2 more authors.
Journal of Aircraft | Year: 2011

Like large insects, micro air vehicles operate at low Reynolds numbers O(1; 000 - 10; 000) in a regime characterized by separated flow and strong vortices. The leading-edge vortex has been identified as a significant source of high lift on insect wings, but the conditions required for the formation of a stably attached leading-edge vortex are not yet known. The waving wing is designed to model the translational phase of an insect wing stroke by preserving the unsteady starting and stopping motion as well as three-dimensionality in both wing geometry (via a finite-span wing) and kinematics (via wing rotation). The current study examines the effect of the spanwise velocity gradient on the development of the leading-edge vortex along the wing as well as the effects of increasing threedimensionalityby decreasing wing aspect ratio from four to two. Dye flow visualization and particle image velocimetry reveal that the leading-edge vortices that form on a sliding or waving wing have a very high aspect ratio. The structure of the flow is largely two-dimensional on both sliding and waving wings and there is minimal interaction between the leading-edge vortices and the tip vortex. Significant spanwise flow was observed on the waving wing but not on the sliding wing. Despite the increased three-dimensionality on the aspect ratio 2 waving wing, there is no evidence of an attached leading-edge vortex and the structure of the flow is very similar to that on the higher-aspect-ratio wing and sliding wing. © Copyright 2010.

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