Study on the Characteristics of Pressure Fluctuations and Aerodynamic Sound of the Vortex Systems Generated around the Leading Edge of Delta Wings

SummarySolutions to the problem of separated flow past slender delta wings for moderate values of a suitably defined incidence parameter have been calculated by Smith, using a vortex sheet model. By increasing the accuracy of the finite-difference technique, and by replacing Smith’s original nested iteration procedure, to solve the non-linear simultaneous equations that arise, by a Newton’s method, it is possible to extend the range of the incidence parameter over which solutions can be obtained. Furthermore for sufficiently small values of the incidence parameter, new and unexpected results in the form of vortex systems that originate inboard from the leading edge have been discovered. These new solutions are the only solutions, to the author’s knowledge, of a vortex sheet leaving a smooth surface.Interest has centred upon the shape of the finite vortex sheet, the position of the isolated vortex, and the lift, and variations of these quantities are shown as functions of the incidence parameter. Although no experimental evidence is available, comparisons are made with the simpler Brown and Michael model in which all the vorticity is assumed to be concentrated onto an isolated line vortex. Agreement between these two models becomes very close as the value of the incidence parameter is reduced.

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1405 Study on Vortical Structures and Aerodynamic Sound of Longitudinal Vortex System Generated around the Leading Edge of Delta Wings

The Proceedings of Conference of Chugoku-Shikoku Branch ◽

10.1299/jsmecs.2016.54._1405-1_ ◽

2016 ◽

Vol 2016.54 (0) ◽

pp. _1405-1_-_1405-3_

Author(s):

Jumpei TAKEDA ◽

Shigeru OGAWA ◽

Keita YANO

Keyword(s):

Leading Edge ◽

Longitudinal Vortex ◽

Vortex System ◽

Delta Wings ◽

Vortical Structures ◽

Aerodynamic Sound

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Investigations on the Blade Vibration of a Radial Inflow Micro Gas Turbine Wheel

International Journal of Rotating Machinery ◽

10.1155/2007/29270 ◽

2007 ◽

Vol 2007 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Shijie Guo

Keyword(s):

Gas Turbine ◽

Young’S Modulus ◽

Young's Modulus ◽

Turbine Blades ◽

Pressure Fluctuations ◽

Leading Edge ◽

Coupled Modes ◽

Blade Vibration ◽

Turbine Wheel ◽

Micro Gas Turbine

This paper demonstrates the investigations on the blade vibration of a radial inflow micro gas turbine wheel. Firstly, the dependence of Young's modulus on temperature was measured since it is a major concern in structure analysis. It is demonstrated that Young's modulus depends on temperature greatly and the dependence should be considered in vibration analysis, but the temperature gradient from the leading edge to the trailing edge of a blade can be ignored by applying the mean temperature. Secondly, turbine blades suffer many excitations during operation, such as pressure fluctuations (unsteady aerodynamic forces), torque fluctuations, and so forth. Meanwhile, they have many kinds of vibration modes, typical ones being blade-hub (disk) coupled modes and blade-shaft (torsional, longitudinal) coupled modes. Model experiments and FEM analysis were conducted to study the coupled vibrations and to identify the modes which are more likely to be excited. The results show that torque fluctuations and uniform pressure fluctuations are more likely to excite resonance of blade-shaft (torsional, longitudinal) coupled modes. Impact excitations and propagating pressure fluctuations are more likely to excite blade-hub (disk) coupled modes.

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Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/99-gt-198 ◽

1999 ◽

Author(s):

Dieter E. Bohn ◽

Karsten A. Kusterer

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Gas Turbines ◽

Leading Edge ◽

Suction Side ◽

Pressure Side ◽

Blade Surface ◽

Cooling Fluid ◽

Flow Phenomena ◽

Vortex Systems

A leading edge cooling configuration is investigated numerically by application of a 3-D conjugate fluid flow and heat transfer solver, CHT-Flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multi-block technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row is on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45°. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical domain includes the internal cooling fluid supply, the radially inclined holes and the complete external flow field of the turbine vane in a high resolution grid. Periodic boundary conditions have been used in the radial direction. Thus, end wall effects have been excluded. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three dimensional and asymmetric jet flow field. Within a secondary flow analysis it can be shown that complex vortex systems are formed in the ejection holes and in the cooling fluid jets. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a good agreement concerning the vortex development. The phenomena on the suction side and the pressure side are principally the same. It can be found that the jets are barely touching the blade surface as the dominating vortex transports hot gas under the jets. Thus, the cooling efficiency is reduced.

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On the Breakdown at High Incidences of the Leading Edge Vortices on Delta Wings

Journal of the Royal Aeronautical Society ◽

10.1017/s0368393100073314 ◽

1960 ◽

Vol 64 (596) ◽

pp. 491-493 ◽

Cited By ~ 19

Author(s):

B. J. Elle

Keyword(s):

High Speed ◽

An investigation of asymmetric vortical flows over delta wings with tangential leading-edge blowing at high angles of attack

10.2514/6.1990-103 ◽

1990 ◽

Cited By ~ 4

Author(s):

ZEKI CELIK ◽

LEONARD ROBERTS ◽

N. WOOD

Keyword(s):

Leading Edge ◽

Delta Wings ◽

Vortical Flows ◽

High Angles Of Attack

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A Note on the Vorticity Distribution on the Surface of Slender Delta Wings with Leading Edge Separation

Journal of the Royal Aeronautical Society ◽

10.1017/s0001924000093520 ◽

1961 ◽

Vol 65 (603) ◽

pp. 195-198 ◽

Cited By ~ 5

Author(s):

B. J. Elle ◽

J. P. Jones

Keyword(s):

Experimental Evidence ◽

Delta Wing ◽

Leading Edge ◽

Water Tunnel ◽

Delta Wings ◽

Vorticity Distribution ◽

Edge Separation

A description is given of the distribution of vorticity in the surface of thin wings with large leading edge sweep. Although the delta wing is chosen as the basic plan form the deductions are general and applicable to other types of wing. The conclusions are illustrated with experimental evidence from a water tunnel.

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