Experimental and Computational Studies of Twin-Vertical-Tail Buffet

Characteristics and mechanism of twin-vertical-tail buffet response on airplane configuration with wing root leading edge extension (LEX) were studied by both experiment and computation. Low-speed wind tunnel experiments were carried out to measure the root bending moment and tip acceleration of vertical tail. Vortical flow patterns were visualized via laser light sheet technique. Three-dimensional computation was performed to solve the unsteady Euler equations on rigid model. The results indicate that (1) bursting of vortices emanating from LEX is the main source of twin-vertical-tail buffet; (2) the Euler equations is able to predict the general characteristics of vertical-tail buffet response reasonably.

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Numerical Analysis of Three-Dimensional Bjo¨rk–Shiley Valvular Flow in an Aorta

Journal of Biomechanical Engineering ◽

10.1115/1.2796063 ◽

1997 ◽

Vol 119 (1) ◽

pp. 45-51 ◽

Cited By ~ 25

Author(s):

E.-B. Shim ◽

K.-S. Chang

Keyword(s):

Shear Stress ◽

Stokes Equations ◽

Three Dimensional ◽

Leading Edge ◽

Vortical Flow ◽

Navier Stokes ◽

Jet Flows ◽

Computational Results ◽

Navier Stokes Equations ◽

Disk Valve

Laminar vortical flow around a fully opened Bjo¨rk–Shiley valve in an aorta is obtained by solving the three-dimensional incompressible Navier–Stokes equations. Used is a noniterative implicit finite-element Navier–Stokes code developed by the authors, which makes use of the well-known finite difference algorithm PISO. The code utilizes segregated formulation and efficient iterative matrix solvers such as PCGS and ICCG. Computational results show that the three-dimensional vortical flow is recirculating with large shear in the sinus region of the valve chamber. Passing through the valve, the flow is split into major upper and lower jet flows. The spiral vortices generated by the disk are advected in the wake and attenuated rapidly downstream by diffusion. It is shown also that the shear stress becomes maximum near the leading edge of the disk valve.

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Analysis of Vortical Flow Field in a Propeller Fan by LDV Measurements and LES—Part I: Three-Dimensional Vortical Flow Structures

Journal of Fluids Engineering ◽

10.1115/1.1412565 ◽

2001 ◽

Vol 123 (4) ◽

pp. 748-754 ◽

Cited By ~ 41

Author(s):

Choon-Man Jang ◽

Masato Furukawa ◽

Masahiro Inoue

Keyword(s):

Flow Field ◽

Three Dimensional ◽

Leading Edge ◽

Tip Vortex ◽

Vortical Flow ◽

Axial Fan ◽

Suction Surface ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Edge Separation

Three-dimensional structures of the vortical flow field in a propeller fan with a shroud covering only the rear region of its rotor tip have been investigated by experimental analysis using laser Doppler velocimetry (LDV) measurements and by numerical analysis using a large eddy simulation (LES) in Part I of the present study. The propeller fan has a very complicated vortical flow field near the rotor tip compared with axial fan and compressor rotors. It is found that three vortex structures are formed near the rotor tip: the tip vortex, the leading edge separation vortex, and the tip leakage vortex. The tip vortex is so strong that it dominates the flow field near the tip. Its formation starts from the blade tip suction side near the midchord. Even at the design condition the tip vortex convects nearly in the tangential direction, thus impinging on the pressure surface of the adjacent blade. The leading edge separation vortex develops close along the tip suction surface and disappears in the rear region of the rotor passage. The tip leakage vortex is so weak that it does not affect the flow field in the rotor.

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Numerical Flow Simulation in a Centrifugal Pump at Design and Off-Design Conditions

International Journal of Rotating Machinery ◽

10.1155/2007/83641 ◽

2007 ◽

Vol 2007 ◽

pp. 1-8 ◽

Cited By ~ 37

Author(s):

K. W. Cheah ◽

T. S. Lee ◽

S. H. Winoto ◽

Z. M. Zhao

Keyword(s):

Centrifugal Pump ◽

Three Dimensional ◽

Flow Simulation ◽

Internal Flow ◽

Leading Edge ◽

Design Flow ◽

Vortical Flow ◽

Navier Stokes ◽

Pump Impeller ◽

Rate Condition

The current investigation is aimed to simulate the complex internal flow in a centrifugal pump impeller with six twisted blades by using a three-dimensional Navier-Stokes code with a standardk-εtwo-equation turbulence model. Different flow rates were specified at inlet boundary to predict the characteristics of the pump. A detailed analysis of the results at design load,Qdesign, and off-design conditions, Q = 0.43Qdesignand Q = 1.45Qdesign, is presented. From the numerical simulation, it shows that the impeller passage flow at design point is quite smooth and follows the curvature of the blade. However, flow separation is observed at the leading edge due to nontangential inflow condition. The flow pattern changed significantly inside the volute as well, with double vortical flow structures formed at cutwater and slowly evolved into a single vortical structure at the volute diffuser. For the pressure distribution, the pressure increases gradually along streamwise direction in the impeller passages. When the centrifugal pump is operating under off-design flow rate condition, unsteady flow developed in the impeller passage and the volute casing.

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Transonic Blade to Blade Calculations in an Axial, Radial or Mixed Flow Cascade Equipped With Splitter Blades

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

10.1115/85-gt-86 ◽

1985 ◽

Author(s):

Fernand Bertheau ◽

Yves Ribaud ◽

Valérie Millour

Keyword(s):

Boundary Conditions ◽

Numerical Method ◽

Euler Equations ◽

Three Dimensional ◽

Computation Time ◽

Leading Edge ◽

Computer Code ◽

Mixed Flow ◽

Three Dimensional Flow ◽

General Computer

A general computer code for pseudo-unsteady Euler equations integration in turbomachinery cascades has been developed. A quasi-three-dimensional flow hypothesis is assumed and only blade to blade calculation is considered here. Cascades may be axial, radial or mixed flow type. First the computerized quasi-orthogonal network is shown. This network takes into account splitters and is designed to reduce the computation time. Then, the numerical method is described and the major difficulties of this problem, which are boundary conditions, leading edge and trailing edge treatments, are presented. Finally, examples of calculations on turbines and compressors are given with emphasis on graphic representation.

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The Suppression of Single-Fin Buffeting Using Tangential Leading Edge Blowing on a Delta Wing

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1243/pime_proc_1992_206_246_02 ◽

1992 ◽

Vol 206 (2) ◽

pp. 93-104

Author(s):

D E Bean ◽

N J Wood ◽

D G Mabey

Keyword(s):

Flow Visualization ◽

Delta Wing ◽

Leading Edge ◽

Light Sheet ◽

Vortical Flow ◽

Delta Wings ◽

Pressure Transducers ◽

Buffeting Response ◽

Flexible Fin ◽

The University

The application of tangential leading edge blowing to reduce levels of single-fin buffeting has been studied. The tests were performed at the University of Bath in the 2.1 m × 1.5 m wind tunnel using two cropped 60° delta wings. To measure the buffet excitation, a rigid fin instrumented with miniature differential pressure transducers was used. A flexible fin of similar planform and size was used to measure the buffeting response. Steady state static pressure data and laser light sheet flow visualization were employed to aid interpretation of the vortical flow over the wings, and hence identify the causes of the buffeting. The profiles of the buffet excitation and response were found to match each other very closely. It was observed that the leading edge blowing modified the leading edge vortices by reducing the ‘effective angle of attack’ of the vortex. Blowing at a constant rate shifted the buffet excitation and response to higher angles of attack. Flow visualization confirmed that the mechanism at peak buffeting had not changed, but had been merely shifted. It has been shown that the use of an optimum blowing programme could completely suppress the buffeting response.

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Vortex interaction on a LEX configuration

Journal of Visualization ◽

10.1007/s12650-021-00764-0 ◽

2021 ◽

Author(s):

Moo-Ting Chou ◽

Jiun-Jih Miau ◽

Li-Yu Chen

Keyword(s):

Reynolds Number ◽

Water Channel ◽

Three Dimensional ◽

Leading Edge ◽

Quantitative Information ◽

Extension Model ◽

Image Velocimetry ◽

Visualization Experiments ◽

Low Speed Wind Tunnel ◽

Edge Extension

AbstractFlow visualization experiments were conducted in a water channel and a low-speed wind tunnel at Reynolds number of 1.54 $$\times$$ × 104 to 1.2 $$\times$$ × 105 for a leading-edge extension model, which is referred to as a NASA TP-1803 model in this study. In addition, particle image velocimetry velocity measurements were taken in the water channel to obtain the quantitative information about the three-dimensional velocity field over the strake and wing surfaces. The results obtained at low, medium and high angles of attacks represent three distinct cases of interaction between the strake and wing vortices. Namely, at α = 5o and 10° the strake and wing vortices were developed over the wing surface without significant interaction noticed; at α = 20°, the strake vortex strongly interacted with the wing vortex in an intertwining manner, which was sensitive to Reynolds number; at α = 30°, the breakdown of the strake vortex took place close to the junction of the strake and the wing; thus, the interaction of the strake and the wing vortices appeared to be less significant than the case of α = 20°. Graphic abstract

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