Aerodynamic characteristics of a large-scale, twin tilt-nacelle V/STOL model

1981 ◽  
Author(s):  
M. FALARSKI ◽  
M. DUDLEY ◽  
W. BUCHMANN ◽  
A. PISANO
Keyword(s):  
Large Scale ◽  
Aerodynamic Characteristics

Analysis of Flutter-Induced Limit Cycle Oscillations in Gas-Turbine Structures With Friction, Gap, and Other Nonlinear Contact Interfaces

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Gas Turbine ◽  
Limit Cycle ◽  
Large Scale ◽  
Direct Calculation ◽  
Aerodynamic Characteristics ◽  
Frequency Domain Method ◽  
Nonlinear Contact ◽  
Limit Cycle Flutter ◽  
Interface Parameters ◽  
First Time

A frequency-domain method has been developed to predict and comprehensively analyze the limit-cycle flutter-induced vibrations in bladed disks and other structures with nonlinear contact interfaces. The method allows, for the first time, direct calculation of the limit-cycle amplitudes and frequencies as functions of contact interface parameters and aerodynamic characteristics using realistic large-scale finite element models of structures. The effects of the parameters of nonlinear contact interfaces on limit-cycle amplitudes and frequencies have been explored for major types of nonlinearities occurring in gas-turbine structures. New mechanisms of limiting the flutter-induced vibrations have been revealed and explained.

Investigation of Wedge Probe Wall Proximity Effects: Part 2—Numerical and Analytical Modeling

1997 ◽  
Vol 119 (3) ◽  
pp. 605-611 ◽  
Author(s):  
P. D. Smout ◽  
P. C. Ivey
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Outer Wall ◽  
Aerodynamic Characteristics ◽  
Proximity Effects ◽  
Wake Flow ◽  
Scale Model ◽  
Flow Structures ◽  
Flow Features ◽  
Wall Proximity

An experimental study of wedge probe wall proximity effects is described in Part 1 of this paper. Actual size and large-scale model probes were tested to understand the mechanisms responsible for this effect, by which free-stream pressure near the outer wall of a turbomachine may be overindicated by up to 20 percent dynamic head. CFD calculations of the flow over two-dimensional wedge shapes and a three-dimensional wedge probe were made in support of the experiments, and are reported in this paper. Key flow structures in the probe wake were identified that control the pressures indicated by the probe in a given environment. It is shown that probe aerodynamic characteristics will change if the wake flow structures are modified, for example by traversing close to the wall, or by calibrating the probe in an open jet rather than in a closed section wind tunnel. A simple analytical model of the probe local flows was derived from the CFD results. It is shown by comparison with experiment that this model captures the dominant flow features.

Aerodynamic characteristics of a large-scale, twin tilt-nacelle V/STOL model

1982 ◽  
Vol 19 (8) ◽  
pp. 627-633
Author(s):  
Michael D. Falarski ◽  
Michael R. Dudley ◽  
W. Buchmann ◽  
A. Pisano
Keyword(s):  
Large Scale ◽  
Aerodynamic Characteristics

Investigation of Wedge Probe Wall Proximity Effects: Part 2 — Numerical and Analytical Modelling

1996 ◽  
Author(s):  
Peter D. Smout ◽  
Paul C. Ivey
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Outer Wall ◽  
Aerodynamic Characteristics ◽  
Proximity Effects ◽  
Wake Flow ◽  
Scale Model ◽  
Flow Structures ◽  
Flow Features ◽  
Wall Proximity

An experimental study of wedge probe wall proximity effects is described in Part 1 of this paper. Actual size and large scale model probes were tested to understand the mechanisms responsible for this effect, by which free stream pressure near the outer wall of a turbomachine may be over indicated by upto 20% dynamic head. CFD calculations of the flow over two-dimensional wedge shapes and a three-dimensional wedge probe were made in support of the experiments, and are reported in this paper. Key flow structures in the probe wake were identified which control the pressures indicated by the probe in a given environment. It is shown that probe aerodynamic characteristics will change if the wake flow structures are modified, for example by traversing close to the wall, or by calibrating the probe in an open jet rather than in a closed section wind tunnel. A simple analytical model of the probe local flows was derived from the CFD results. It is shown by comparison with experiment that this model captures the dominant flow features.

An Experimental Investigation of the Three-Dimensional Flow Within Large Scale Turbine Cascades

1986 ◽  
Author(s):  
Jaromír Jílek
Keyword(s):  
Experimental Investigation ◽  
Large Scale ◽  
Three Dimensional ◽  
Side Wall ◽  
Aerodynamic Characteristics ◽  
Flow Measurements ◽  
Wall Boundary Layer ◽  
Flow Parameters ◽  
Side Walls ◽  
Turbine Cascades

A detailed experimental investigation of the three-dimensional subsonic flow was carried out in a typical nozzle and impulse configuration of plane turbine cascades with a chord length 0.5 m. Flow parameters were measured within the passage and behind the cascade using a five-hole probe. Pressure distribution measurements and flow visualization were made on blade surfaces and side walls. Flow measurements were taken in endwall and airfoil boundary layers for both types of cascades. The influence of the aspect ratio, the inlet side wall boundary layer and the position of traversing planes on aerodynamic characteristics and losses is discussed.

Experimental Characterization of the Coolant Film Issuing From a Cooling Tile

2004 ◽  
Author(s):  
K. H. Chua ◽  
J. Carrotte ◽  
P. Denman ◽  
A. Spencer
Keyword(s):  
Large Scale ◽  
Subsequent Development ◽  
Aerodynamic Characteristics ◽  
Linear Increase ◽  
Wall Film ◽  
Surface Data ◽  
Mainstream Flow ◽  
Conventional Cooling ◽  
Hot Surface ◽  
Tile Surface

In modern, low emission, gas turbine combustion systems the amount of air available for cooling of the flame tube liner is limited. This has led to the development of more complex systems, such as cooling tiles, as opposed to the use of more conventional cooling slots. Within a cooling tile the flow passes around a large number of pedestals located between 2 skins that promote the removal of heat from the hot surface. This flow is then discharged from a slot at the rear of the tile to form the coolant film. This paper characterises the flow passing through a tile and, in particular, the coolant film that is formed along the tile surface. Data is presented for both a standard tile geometry and one in which the coolant film is enhanced by effusion cooling. A large-scale facility incorporating a 10 times full size cooling tile has been developed. The aerodynamic characteristics of the coolant film have been defined using pneumatic probes, hot wire anemometry and PIV instrumentation, while gas tracing is used to indicate mixing of the coolant film with the mainstream flow. For low mainstream turbulence the results show that the initial condition of the cooling film dominates the subsequent development and mixing of the film along the tile length. Relative to this configuration, high mainstream turbulence levels with large turbulent scales were introduced by placing a cylinder upstream of the tile. The turbulent mainstream flow quickly penetrates the coolant film and a more rapid break up of the coolant film is observed. This includes an almost linear increase in thickness of the coolant film together with a linear reduction in wall film effectiveness along the tile length. Relative to this conventional tile the use of effusion cooling was shown to restore the film effectiveness along the rear of the tile. In addition to the time averaged characteristics the time dependent behaviour of the coolant film was also investigated. In particular, unsteadiness associated with vortex shedding within the mainstream flow was observed within the coolant film and adjacent to the tile surface.

scholarly journals Aerodynamics of High-Sided Vehicles on Truss Girder Considering Sheltering Effect by Wind Tunnel Tests

2020 ◽  
Vol 15 (2) ◽  
pp. 66-88
Author(s):  
Jingyu Zhang ◽  
Mingjin Zhang ◽  
Yongle Li ◽  
Xu Huang ◽  
Zhong Zheng
Keyword(s):  
Large Scale ◽  
Sudden Change ◽  
Aerodynamic Characteristics ◽  
Leeward Side ◽  
Aerodynamic Coefficients ◽  
Test Vehicle ◽  
Aerodynamic Coefficient ◽  
Running Safety ◽  
Sheltering Effect ◽  
Bridge Tower

Aerodynamic characteristics of vehicles are directly related to their running safety, especially for the high-sided vehicles. In order to study the aerodynamic characteristics under multiple sheltering conditions, a complex large scale (1:20.4) truss model and three high-sided vehicles including articulated lorry, travelling bus and commercial van models with the same scale were built. The aerodynamic coefficients under various sheltering effects of wind barriers with different heights and porosities, bridge tower and the vehicle on the adjacent lane were measured. According to the results, wind barriers can effectively reduce wind speed behind them, thus decreasing the wind load acting on the vehicle, which causes the decrease of the aerodynamic response of all three vehicles. However, the influence at the leeward side is limited due to installation of central stabilizers. When the vehicle passes through the bridge tower, a sudden change occurs, the aerodynamic coefficients decrease and fluctuate in varying degrees, especially for the commercial van. When the vehicle moves in different lanes behind the bridge tower, the sheltering effect of the tower on the aerodynamic coefficient in Lane 1 is much greater than that in Lane 2. With regard to the interference between two vehicles on the adjacent lanes, the relative windward area between the test vehicle and the interference vehicle greatly affects the aerodynamics of the test vehicle.

scholarly journals Flexible Flaps Inspired by Avian Feathers Can Enhance Aerodynamic Robustness in low Reynolds Number Airfoils

2021 ◽  
Vol 9 ◽  
Author(s):  
Yuta Murayama ◽  
Toshiyuki Nakata ◽  
Hao Liu
Keyword(s):  
Large Scale ◽  
Aerodynamic Characteristics ◽  
Small Scale ◽  
Vortex Generation ◽  
Force Measurements ◽  
Large Scale Vortex ◽  
Oscillating Plate ◽  
Low Speed Wind Tunnel ◽  
Strong Vortex ◽  
Rigid Rotors

Unlike rigid rotors of drones, bird wings are composed of flexible feathers that can passively deform while achieving remarkable aerodynamic robustness in response to wind gusts. In this study, we conduct an experimental study on the effects of the flexible flaps inspired by the covert of bird wings on aerodynamic characteristics of fixed-wings in disturbances. Through force measurements and flow visualization in a low-speed wind tunnel, it is found that the flexible flaps can suppress the large-scale vortex shedding and hence reduce the fluctuations of aerodynamic forces in a disturbed flow behind an oscillating plate. Our results demonstrate that the stiffness of the flaps strongly affects the aerodynamic performance, and the force fluctuations are observed to be reduced when the deformation synchronizes with the strong vortex generation. The results point out that the simple attachment of the flexible flaps on the upper surface of the wing is an effective method, providing a novel biomimetic design to improve the aerodynamic robustness of small-scale drones with fixed-wings operating in unpredictable aerial environments.

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