Dissertations / Theses on the topic 'Vertical tail'

Enhancing the ability to predict airflow around the Vertical Tail Plane (VTP) of an aircraft is vital in the aviation industry. The size of the VTP is driven by a particular flight condition - loss of an engine during take-off and low speed climb. Nowadays, Computational Fluid Dynamics (CFD) is the main tool used by engineers to assess VTP flows. However, due to uncertainties in the prediction of VTP effectiveness, aircraft designers keep to a conservative approach, which risks oversizing of the tail plane, adding more drag. Uncertainties emerge from difficulties in predicting the massive separation that occurs on the swept tail when it is approached by a flow at high incidence. Furthermore, the deployment of the control surface (the rudder) over the tail plane and the skewed flow along the span increase the CFD challenges. Improved predictive capabilities of the flow around VTPs would enable a more optimal design approach with potential drag saving. The correct prediction of flow separation is the essence of this study. Currently, the industry uses steady Reynolds-Averaged Navier-Stokes (RANS) simulations to analyse VTPs flow. In order to assess RANS performance, the study of airflow detaching from a backward rounded ramp is performed and the results are compared to Large-Eddy Simulations (LES). The analysis shows that, even though RANS may predict the onset of flow separation correctly, they completely miss the location of flow reattachment over the ramp, and this affects the whole flow solution. Moreover, the flow features a strong anisotropy at the onset of separation, difficult to be captured by RANS. The analysis shows that RANS cannot predict production of turbulent kinetic energy in the detached flow region correctly, discouraging flow mixing, and delaying flow reattachment. A hybrid RANS/LES carried out on the same test case shows the benefits of using eddy-resolving simulations for detached flows. The prediction of the locations of the separation and reattachment points differs by only 1% from the highly-resolved simulation. The VTP investigation carried out in this thesis uses a wind tunnel model tested at Airbus. The study starts with steady RANS approaches for different turbulence models. RANS simulations produce acceptable results for the flow at low incidence levels. On the contrary, at high incidence, when flow separation occurs, RANS methods fail. The second step of the research consists of using unsteady RANS (URANS) simulations for VTP flows at high sideslip angles. The introduction of time-accuracy brings important benefits. Nevertheless, the results still show some inaccuracies (around 20% error). Finally, restarting from the flow solutions obtained by URANS simulations, higher fidelity hybrid RANS/LES techniques in the form of Delayed Detached-Eddy Simulations (DDES) are used to assess the characteristics of the separated flow around the tail plane. Results show a remarkable improvement of the flow solution. The pressure distribution matches experimental results favourably, and this translates into an improved prediction of the aerodynamic loads over the VTP. This leads towards a new strategy for the assessment of the flow over aircraft VTPs, amounting to an important contribution to the design of future aircraft.

Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, Sept. 1997.
Thesis advisors, E. Roberts Wood, D.A. Danielson, and Joshua H. Gordis. Includes bibliographical references (p. 61). Also available online.

High performance twin-tail aircraft, like the F-15 and F/A-18, encounter a condition known as tail buffet. At high angles of attack, vortices are generated at the wing fuselage interface (shoulder) or other leading edge extensions. These vortices are directed toward the twin vertical tails. When the flow interacts with the vertical tail it creates pressure variations that can oscillate the vertical tail assembly. This results in fatigue cracks in the vertical tail assembly that can decrease the fatigue life and increase maintenance costs. For many years, research has been conducted to understand this phenomenon of buffet and to reduce its adverse effects on the fatigue life of aerospace structures. Many proposed solutions to this tail buffet problem have had limited success. These include strengthening the tail, modifying the vortex flow, using an active rudder control, and leading edge extensions. Some of the proposed active controls include piezoelectric actuators. Recently, an offset piezoceramic stack actuator was used on an F-15 wind tunnel model to control buffet induced vibrations at high angles of attack. The controller was based on acceleration feedback control methods. In this thesis a procedure for designing the offset piezoceramic stack actuators is developed. This design procedure includes determining the quantity and type of piezoceramic stacks used in these actuators. The changes of stresses, in the vertical tail caused by these actuators during an active control, are investigated. In many cases, linear controllers are very effective in reducing vibrations. However, during flight, the natural frequencies of the vertical tail structural system changes as the airspeed increases. This in turn, reduces the effectiveness of a linear controller. Other causes such as the unmodeled dynamics and nonlinear effects due to debonds also reduce the effectiveness of linear controllers. In this thesis, an adaptive neural network is used to augment the linear controller to correct these effects.

An artificial Neural Network (ANN) system has been developed that can analyse aircraft flight data to provide a reconstruction of the aerodynamic loads experienced by the aircraft during flight, including manoeuvre, buffet and distributed loading. For this research data was taken from the International Follow-On Structural Test Project (IFOSTP) F/A-18 fatigue test conducted by the Royal Australian Air Force and Canadian Forces. This fatigue test involved the simultaneous application of both manouevre and buffet loads using airbag actuators and shakers. The applied loads were representative of the actual loads experienced by an FA/18 during flight tests. Following an evaluation of different ANN types an Ellman network with three linear layers was selected. The Elman back-propagation network was tested with various parameters and structures. The network was trained using the MATLAB 'traingdx' function with is a gradient descent with momentum and adaptive learning rate back-propagation algorithm. The ANN was able to provide a good approximation of the actual manoeuvre or buffet loads at the location where the training loads data were recorded even for input values which differ from the training input values. In further tests the ability to estimate distributed loading at locations not included in the training data was also demonstrated. The ANN was then modified to incorporate various methods for the calculation and prediction of output error and reliability Used in combination and in appropriate circumstances, the addition of these capabilities significantly increase the reliability, accuracy and therefore usefulness of the ANN system's ability to estimate aircraft loading.To demonstrate the ANN system's usefulness as a fatigue monitoring tool it was combined with a formulae for crack growth analysis. Results inficate the ANN system may be a useful fatigue monitoring tool enabling real time monitoring of aircraft critical components using existing strain gauge sensors.

The tower crane is an electromechanical equipment that is used for the vertical transport of materials in a construction project and together with the two riggers form the work team to carry out this task. One of the main problems in the construction of multifamily buildings corresponds to the use of the tower crane because vertical transport causes non-contributory times, which is, dead times and waits above expectations. This research analyzes the current vertical transport process and proposes its optimization through some management tools with the aim of improving the productivity of the use of the tower crane by reducing non-contributory times. To this end, the productivity of the work team is recorded in several projects with similar characteristics, then the main problems are selected to analyze them and finally the process is optimized. The results determined that non-contributory times can be reduced by 10% if there is an orderly and continuous process.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.
Includes bibliographical references (leaves 125-128). Also available in electronic version. Access restricted to campus users.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Nowadays Brazil is self sustaining in apple. The production is located in micro regions in Southern Brazil, in Santa Catarina and Rio Grande do Sul State. The technology and innovation need to be allied of the technicians and growers, responsible for the nacional production. The decision of which training system that will be used, it is one of the decisions that needs to do at planning to plant a new orchard. Is there so many training systems around the world. The choosed system wills interfer directlly in the profitability of the orchard. Nationally, the traditional system used is central leader system, with some changes, depending on the region that it is installed. With those informations, the aim of this study was evaluate different training systems in trials that combine the two most growed cultivars, Gala and Fuji, combined with the two most used rootstocks, M.9 and Marubakaido with interstem of M.9. The training systems evaluated were Vertical Axis, Tall Spindle and Solaxe at Vacaria-RS. The study concludes that Kiku-8®‟, grafted on M.9 tends to be a bi-annual bearing in all systems, the same cultivar was more vigorous when grafted on Marubakaido‟ trained in Vertical Axis. Maxi Gala‟ showed more vigour when trained in Vertical Axis in both rootstocks. All systems did not have effect in fruit quality parameters, like total soluble solids, flesh firmness and fruit size. It is necessary more labor hours Solaxe System in the most part of the combinations.The choice of which training system is the best to use, needs to be embased with data of more years of study
O Brasil é autossustentável em maçãs. A produção está concentrada em micro regiões no Sul do Brasil, nos estados de Santa Catarina e Rio Grande do Sul. A tecnologia e inovação devem ser aliadas dos técnicos e produtores responsáveis pela produção nacional. A decisão de qual sistema de condução é um dos intens a ser planejados antes mesmo da implantação do pomar. Diversos são os sistemas de condução existentes, existindo diferentes preferências nas diversas regiões produtoras ao redor do mundo. O sistema de condução escolhido vai inferir diretamente na rentabilidade do pomar. Nacionalmente o sistema de condução tradicional é em líder central, variando sua forma conforme local e tecnologia empregada. A partir dessas considerações objetivouse nesse trabalho avaliar diferentes sistemas de condução que utilizam líder central, em experimentos combinados com as cultivares mais produzidas no país, Gala e Fuji e com dois dos portaenxertos, M.9 e Marubakaido com interenxerto de M.9. Os sistemas de condução são o Vertical Axis, Solaxe e Tall Spindle, no município de Vacaria (RS). Pode-se concluir neste estudo que Kiku-8®‟ enxertado sobre M.9 mostra tendência a alternância de produção em todos os sistemas de condução, a mesma foi mais vigorosa quando enxertada sobre Marubakaido‟ e conduzida em Vertical Axis. Para a Maxi Gala‟ também o sistema Vetical Axis foi o qu mais induziu vigor nos dois portaenxertos utilizados. Os sistemas de condução não interferem nos fatores de qualidade de frutos como teor de sólidos solúveis, firmeza de polpa e tamanho de fruto. É necessário maior número de horas de mãode- obra no sistema Solaxe na maior parte das combinaçõe. A decisão para seleção de sistemas de condução terá que ser feita com base em resultados de mais safras

Fire in buildings can have a severe impact in terms of both human safety and potential economic loss. This is especially true in the case of fires of such severity that the building structure is damaged. Concrete buildings are traditionally regarded as safe in a fire situation as concrete is non-flammable and exhibits highly insulating material properties. The majority of current research relating to the impact of fire on structures examines other forms of construction. Research of concrete in fire is generally limited to investigation and testing of individual members in order to understand the often complex interactions exhibited by concrete as a material at high temperatures. This research seeks to redress the balance by using a systematic approach to examine effects of fire on a holistic concrete structure in simplified but realistic temperature exposures. The research utilises evidence and structural information from the Windsor Tower in Madrid, which suffered a major fire in February 2005 with partial collapse in some areas of the structure. The fire spread throughout the building, travelling both upwards and downwards. Computer modelling was used extensively. Computational Fluid Dynamics (CFD) analysis was used to explore likely fire temperature and duration in localised areas. Structural Finite Element Modelling (FEM) was used to develop a hierarchy of models, beginning with simple structural forms and progressing logically to more detailed structures. This produced a systematic and comprehensive analysis of the reaction of the structure to fire for comparison to the real, observable damage to the building and assessment of generic failure behaviours. The structural model produced was used with a number of variations in support condition, fire spread rate and extent, and fire protection. It was found that for a structure of this type, structural stiffness of the concrete floors was insufficient to compensate for the loss of strength in heated steel members where there was no alternative load redistribution path. It was also found that in the case where an alternative load path exists, but involves steel members which have previously heated during the multiple-floor spread of the fire, the rate of fire spread has a critical effect on the structural stability.

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The civil construction management has been taken more attention of civil construction companies in aim alternatives to enhancing theirs management process, main that work with building construction because the growing competition and the exigency of their invest. In this set, the strategic planning is fundamental for the development and success of business because generates data that will guide the balance between the production planning expectation and the necessary costs for concluding a project. The supply of planning data and performances of building construction is get to divide of the simulation of the production strategy. The planning production represents the strategies because its products are some information: schedules, graphs and reports to arrive the execution efficiency. This research presents analyze the conduct of two different construction systems variables of three construction strategies. The construction systems studied were traditional construction system and the external walls in reinforced concrete construction system. The production strategies simulated concentrated in analyse only the tower and were without inversion of services; with partial inversion of services; and with total inversion of services. Like product of this research to claim develop a systematization to value and choose the production strategies to attend by the tall building construction companies.
O gerenciamento em obras de construção civil vem recebendo atenção por parte das empresas na busca de alternativas para melhorar seus processos de gestão da produção. Isso ocorre principalmente em empresas que trabalham com construção de edifícios para o mercado imobiliário, face à competitividade e exigências estabelecidas por seus investidores. Neste contexto, as estratégias de execução são fundamentais para o desenvolvimento e sucesso do negócio , pois delas decorrem a forma de como serão aproveitados os recursos físicos e financeiros disponibilizados. Através de simulações de estratégias de execução são fornecidos diversos dados de planejamento ao subsetor edificações. Tais estratégias são representadas pelo planejamento da produção através da geração de informações: cronogramas, gráficos e relatórios. Dessa forma, este trabalho analisa o comportamento das variáveis de produção de dois sistemas construtivos através da proposição de três diferentes estratégias de execução. Os sistemas estudados foram o sistema construtivo tradicional e o sistema construtivo com paredes externas em concreto moldado in loco . As estratégias de execução simuladas concentraram-se na análise dos serviços da torre do edifício vertical, sendo propostas as seguintes seqüências: sem inversão dos serviços, com inversão total dos serviços e com inversão parcial dos serviços. Os principais resultados desta pesquisa são apresentados na forma de parâmetros e gráficos que facilitam a avaliação e seleção de estratégias de execução a serem seguidas pelas empresas que executam edifícios verticais.

Venus' nightside ionosphere may be characterized by two general magnetic field geometries. Most of the ionosphere is characterized by largely horizontal fields carried over across the terminator from the dayside. However, regions of mostly vertical fields, associated with the nightside ionospheric 'holes' and connected to regions in the ionosheath where there are strong tailward fields, are also present. A magnetic potential model has been developed to describe the interface of the ionosphere, represented as an infinite slab bounded by two magnetically impermeable planes, with the tail lobes idealized as semi-infinite solenoids terminating at the ionopause. From this model, ionospheric boundary currents are generated to confine all field lines in either the flat ionosphere or the vertical tail lobe, and the field geometries are explored. Techniques for mapping this solution to a sphere and approximating it at long ranges from the transition region are discussed, and a preliminary global nightside model is offered.

Dissertação de mestrado integrado em Arquitectura, Universidade Lusíada de Lisboa, 2016
Exame público realizado em 3 de Março de 2017
Se a arquitectura é a expressão do seu tempo, então o arranha-céus é expressão vertical da poética do capitalismo, construindo o fantástico através da escala do monumental e da cidade vertical, num manifesto triunfo do físico sobre o meta-físico. O presente estudo pretende fornecer uma compreensão dos factores simbólicos, históricos, tecnológicos e socioeconómico responsáveis pela promoção do crescimento em altura, com ênfase na relação interdependente entre as torres e a dinâmica da micro e macroeconómica. Acrescenta-se a especificidade do paradigma da sustentabilidade, na vertente da problemática da escassez dos recursos ambientais, num contexto de crescimento exponencial da população urbana e consequente expansão dos limites da cidade. Questiona-se ainda acerca do potencial do arranha-céus, tipologia ao serviço do capital, transcender o seu papel egocêntrico, para dar resposta aos atuais desafios da cidade. Neste sentido a metodologia adoptada nesta pesquisa é baseada na investigação bibliográfica, na análise de bases de dados dedicadas, na pesquisa fotográfica in loco e também orientada sob pressupostos de uma perspectiva histórico-crítica comparativa, com o objectivo de identificar de padrões, mecanismos e dinâmicas que expliquem o processo complexo do fenómeno da construção em altura. A análise dos argumentos sugerem uma íntima relação interdependente, entre esta tipologia, o mercado imobiliário, a dinâmica capitalista e o conjunto de valores a estes associados. Finalmente, identifica-se o potencial da orgânica das oportunidades intrínsecas à economia de meios da cidade vertical tanto para a urgente necessidade de redução do consumo energético como para a contenção do urban sprawl.

博士
國立成功大學
機械工程學系
87
The present investigation consists of numerical prediction and/or experimental visualization on the transition of natural convection of cold water in vertical enclosures. Using a finite difference method, numerical simulations of the transient natural convection of cold water contained in vertical enclosures of height/width ratio 8 (cylindrical annulus or rectangular enclosure) have been performed by increasing the Rayleigh number step by step under two different values of the density inversion parameter of 0.4 and 0.5, respectively. The range of the Rayleigh number considered is from to . The radius ratio of the cylindrical annulus is fixed at 2. The three dimensional numerical simulation focus on the natural convection of cold water in the rectangular enclosure under the density inversion parameter of 0.5 to explore the effect of the depth/width ratio of the enclosure on the instability mechanism. The range of the Rayleigh number considered for the three-dimensional simulations is from to . The evolutions of fluid flow structure and temperature distribution of cold water in the enclosures are visualized numerically by means of contour maps of streamline and/or velocity vector field and isotherm. Furthermore, the instability mechanism responsible for the transition to unsteady natural convection of cold water and its spatial distribution within the enclosures are illustrated by means of the contour maps of fluctuation magnitude of flow variables or compositions of the fluctuating kinetic energy. The experimental work in the present study mainly focuses on the flow and temperature visualizations, by means of a thermochromic liquid crystal, in a test cell, which was designed and constructed to mimic the physical configuration considered in the numerical simulations. The results of numerical simulation clearly reveal that the value of density inversion parameter predominantly determines the profile of maximum density contour, which demarcates the two contra-rotating circulation flow structures of cold water prevailed in the enclosure. The instability mechanism appears to initiate by the Kelvin-Helmholtz instability due to shear imbalance along the sinking jet flow structure emanating from the ceiling of enclosure, which results in wavy distortion of the maximum density contour of cold water. As a result of the wavy maximum density contour, unstable density stratification (the Rayleigh-Benard instability) is induced. The vertical boundary layer flows along the vertical walls are thereby perturbed and the Tollmien-Schlichting instability arises accordingly. The laminar transition to self-sustained oscillatory convection has a strong bearing with the density inversion phenomenon of cold water. The results of two- or three-dimensional numerical simulations reveal similar mechanism for the unsteadiness of cold water in the rectangular enclosure. The production of fluctuating kinetic energy is completely contributed by the buoyancy. The results of experimental visualization show that growing, merging and upward-drifting of the secondary vortex is accompanied wavy movement with the maximum density contour. Comparison between the numerical prediction and the experimental visualization reveals a fair agreement.

碩士
臺北巿立體育學院
運動器材研究所
99
Purpose: To investigate the effect of 8-weeks Tai Chi-Vibration complex training on vertical jump, tactile acuity, muscular control and peripheral nerve adaptation. Methods: Sixty-four healthy college students were divided into a Tai Chi Chuan with vibration group (TAV), a Tai Chi Chuan group (TAI), a vibration group (VB), and a control group (CON) for 8 weeks training period with 3 times per week. The vertical jump, tactile acuity of the midfoot, muscular control of quadriceps muscle, H-reflex and M-wave of gastrocnemius muscle were measured at pre- and post-training. The two-way ANOVA with mixed design were used for statistic analysis. Results: The results showed that the vertical jump significantly increased in both TAV and VB groups (p< .05). The VB group was significant higher the change rate of second vertical jump than that of TAI and CON groups (p< .05). The Tactile acuity significantly improved in both TAV and TAI groups (p< .05). The muscular control ability of TAI group significantly increased, and its changing rate was significant higher than that of CON group (p< .05). The Hmax/Mmax ratio of VB group significantly decreased (p< .05). The T/Mmax ratio significantly increased in TAV group, but decreased in VB group (P< .05). The changing rate of TAV group was significant greater than that of VB group (p< .05). Conclusion: The TAV training can be used to improve vertical jump, tactile acuity, and the excitability of γ-reflex arc. The TAI training can be used to enhance the abilities of tactile acuity and muscular control. The VB group can be used to increase vertical jump, tactile acuity, and the resting excitability of α-motorneuron pool. Therefore, the Tai Chi-Vibration complex training as combined the Tai Chi Chuan and vibration stimulus makes positive training benefit.