円柱翼に作用する縦渦による揚力の評価と発生機構の解明

国立大学法人長岡技術科学大

縦渦により駆動される円柱翼風車の開発

国立大学法人長岡技術科学大

An engineering method for modeling the interaction of circular bodies and very low aspect ratio cruciform wings at supersonic speeds

An engineering method using a 2D unsteady potential formulation (called the free vortex model or FVM) has been developed to predict the normal force, centre-of-pressure and vortex position for cruciform wing-body combinations in the “plus” orientation, at supersonic speeds and cross flow Mach numbers less than or equal to 0.55 up to anglesof attack 20◦. The wings are of very low aspect ratio ( ≤ 0.1), have taper ratios greater than 0.85 (or significant side edges) and have low span to body diameter ratios ( ≤ 1.5). The method predicts the position and subsequent loads imposed by the vortex along the length on the wing-body combination by determining the shed vorticity using Jorgensen’s modified Newtonian impact method. The vortex position is well predicted for angles ofattack from 4◦ until symmetric vortex shedding occurs, whilst the normal force is well predicted from 0◦. The centre-of-pressure is predicted further aft at the low angles and further forward at the high angles of attack. If this method is used in combination with the single concentrated vortex of Bryson applied to cruciform wing-body combinations the vortex positions prediction limitations at angles of attack less than 4◦ can be overcome. An investigation of the lee side flow field of cruciform wing-body configurations was also performed, and revealed that the vortex position is dependent upon the lee side secondary vortex separation characteristics. Other features revealed that symmetric vortex shedding occurs when both the region of flow outside the shed vortex sheet and reverse flow region are supersonic and a termination shock exists. The thesis also investigated the applica-tion of the discrete vortex model (DVM) method to cruciform wing-body combinations and found that the potential only formulation overpredicts the normal force, whilst the inclusion of boundary layer separation (and therefore modeling the secondary separation vortex) predicted the normal force very well. The application of the concentrated vortex method of Bryson was also investigated and found to be only applicable at low angles of attack (< 4◦)

An engineering method for modeling the interaction of circular bodies and very low aspect ratio cruciform wings at supersonic speeds

An engineering method using a 2D unsteady potential formulation (called the free vortex model or FVM) has been developed to predict the normal force, centre-of-pressure and vortex position for cruciform wing-body combinations in the “plus” orientation, at supersonic speeds and cross flow Mach numbers less than or equal to 0.55 up to angles of attack 20◦. The wings are of very low aspect ratio ( ≤ 0.1), have taper ratios greater than 0.85 (or significant side edges) and have low span to body diameter ratios ( ≤ 1.5). The method predicts the position and subsequent loads imposed by the vortex along the length on the wing-body combination by determining the shed vorticity using Jorgensen’s modified Newtonian impact method. The vortex position is well predicted for angles of attack from 4◦ until symmetric vortex shedding occurs, whilst the normal force is well predicted from 0◦. The centre-of-pressure is predicted further aft at the low angles and further forward at the high angles of attack. If this method is used in combination with the single concentrated vortex of Bryson applied to cruciform wing-body combinations the vortex positions prediction limitations at angles of attack less than 4◦ can be overcome. An investigation of the lee side flow field of cruciform wing-body configurations was also performed, and revealed that the vortex position is dependent upon the lee side secondary vortex separation characteristics. Other features revealed that symmetric vortex shedding occurs when both the region of flow outside the shed vortex sheet and reverse flow region are supersonic and a termination shock exists. The thesis also investigated the applica- tion of the discrete vortex model (DVM) method to cruciform wing-body combinations and found that the potential only formulation overpredicts the normal force, whilst the inclusion of boundary layer separation (and therefore modeling the secondary separation vortex) predicted the normal force very well. The application of the concentrated vortex method of Bryson was also investigated and found to be only applicable at low angles of attack (< 4◦).EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Aeronautical Engineering: A special bibliography with indexes, supplement 67, February 1976

This bibliography lists 341 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1976

Aeronautical engineering: A continuing bibliography with indexes (supplement 293)

This bibliography lists 476 reports, articles, and other documents introduced into the NASA scientific and technical information system in July, 1992. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical Engineering: A special bibliography with indexes, supplement 55

This bibliography lists 260 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1975

Hydrodynamic Control of a Submarine Close to the Sea Surface

To understand the behaviour of a submarine under the influence of surface waves at the early stages of design, the impact on whole boat design, from the perspective of the hydrodynamic shape of the hull, internal arrangements, performance requirements of ballast tanks and pumps and the requirements of control surfaces, a suitable design tool and analysis process is required. The thesis includes outcomes from different engineering disciplines; principally, naval architecture (particularly the specialised areas of submarine hydrodynamics and ocean engineering) and control engineering. The thesis particularly draws upon research from the area of ocean engineering, specifically in the methods of quantifying second order effects, to bring insights into control system design for the problem of submarine control under waves. This is achieved by providing a potential approach for developing control system specifications in reflection of the available assessment methods

Effects of the secondary iterations of square fractal grids on continuous and synthetic jets

The Nile river, the Italian coastline, the snowflakes, the tree branches, mountains, clouds, seashells all belong to a class of objects known as fractals. Fractals are neverending patterns, widely diffused in nature, which repeat themselves over and over, at different length scales. Abstract fractals can be also generated by a computer calculating a simple equation over and over. Fractals have more and more applications in science modelling, as they very often describe the real world better than traditional mathematics and physics. Moreover, fractal-shaped elements have been successfully applied to many industrial fields such as the mixing, aeronautical, automotive, power generation and wind energy industries. Among the other, Cafiero et al. (2014, 2015, 2016, 2017) proposed the use of fractal grids to increase the mixing and heat transfer features of turbulent jets, typically used for cooling of turbine blades and of electronic components, for paper and film drying, for glass annealing and tempering, etc. Their results showed that fractal turbulators significantly increase the heat transfer properties of round turbulent jets or jet equipped with regular grids having the same blockage ratio of the fractal ones (Cafiero et al.,2014). Subsequent 2D and 3D flow fields measurements (Cafiero et al., 2014; Cafiero et al., 2015) showed that the main factors which are responsible for this increase are the higher turbulence intensity levels due to the fractal pattern and the ability of the fractal turbulator in producing streamwise vorticity. Following these works, this thesis focuses on the effects of the secondary iterations bars on turbulent jets equipped with square-fractal inserts. The obtained results are organised in four different chapters. In Chapter 4, the effects due to the introduction of the secondary iterations on continuous turbulent jets equipped with square-fractal inserts are analysed by introducing either a single square grid or a 3-iterations square-fractal grid at the exit section of short pipe nozzle. Measurements are carried out at fixed Reynolds number, Re≈6,700, by means of planar Particle Image Velocimetry. A double-camera configuration is used to simultaneously analyse the effects of the grids’ bars and the interaction between the grid-generated turbulence and the jet shear layer. The flow fields are investigated both in terms of first and second order statistics. In order to assess the effects of the smallest bars of the fractal insert on the wake generated by the largest bars, the Proper Orthogonal Decomposition snapshot method is applied to a small measurement volume past the 1st iteration bars. In Chapter 5, the same single square grid and fractal square grid analysed in Chapter 4 are inserted at the exit section of a synthetic jet device. Measurements are carried out, for three different device actuation frequencies, at a fixed Reynolds number Re≈6,700. The results are investigated both in terms of time-averaged and phase-averaged flow fields. The generation and the evolution of the coherent vortical structures are analysed by means of the Q-criterion. The effects of the secondary iterations introduction and of their thickness in turbulent continuous jets equipped with fractal-square grids are discussed both in terms of heat transfer properties (Chapter 6) and flow field measurements (Chapter 7). In particular, in Chapter 6, IR Thermography measurements, combined with the heated-thin-foil heat flux sensor, are performed to compare, under the same power input, several fractal and single square grids in terms of both spatial averaged and local convective heat transfer. Moreover, the effect of the grid geometry onto the convective heat transfer uniformity is investigated. Finally, the jet flow developed downstream of each of the grids analysed in Chapter 6 is investigated, at a fixed Reynolds number Re≈16,000. The jet flow due to the introduction of a regular grid characterised by the same blockage ratio of the fractal one is also investigated. Finally, the axisymmetric turbulent jet evaluated at the same Reynolds number is reported as reference. Results are analysed both in terms of first and second order statistics. Moreover, the effects of the grid geometry on the large-scale isotropy and on the spatial-averaged velocity power spectra are discussed