The Interaction of Downwind Sails

2006 ◽  
Author(s):  
William C. Lasher
Keyword(s):  
Driving Force ◽  
Angle Of Attack ◽  
The Other ◽  
Surprising Result ◽  
Cfd Analysis ◽  
Projected Area ◽  
General Direction ◽  
Optimum Angle

When a sailboat is sailing in the general direction of the wind, it is known as downwind sailing. Under these conditions boats generally carry two sails — a mainsail and a spinnaker. The flow over these sails is complicated and poorly understood. An issue of importance to sailors is how the adjustment of one sail affects the aerodynamics of the other sail and the total driving force. In the present work a CFD analysis was performed on two different sailboat rigs, with an emphasis on the interactions between the main and spinnaker. The results show that the optimum angle of attack of the mainsail is generally 60° to 70°, depending on the direction of the wind relative to the boat. The correct setting for a mainsail has been a point of debate amongst sailors, and the present analysis supports the theory of easing the mainsail until it luffs (or flaps), then pulling it in. A surprising result is that when the wind is directly behind the boat, the mainsail should not be set to maximize projected area, but eased out past 90°. This is difficult to accomplish in practice due to restrictions of the rig, but raise some interesting questions.

Experimental and numerical study of an overlay composite absorber plate material for a solar air heater

2021 ◽  
Vol 63 (7) ◽  
pp. 681-686
Author(s):  
Duraisamy Jagadeesh ◽  
Ramasamy Venkatachalam ◽  
Gurusamy Nallakumarasamy
Keyword(s):  
Numerical Study ◽  
The Other ◽  
Solar Air Heater ◽  
Outlet Temperature ◽  
Cfd Analysis ◽  
Plate Material ◽  
Absorber Plate ◽  
Air Heater ◽  
Margin Of Error ◽  
Computational Processes

Abstract The research in this paper is a sequel of an earlier work by the author in which experimental and CFD results were compared for an absorber plate made of iron with and without fins for two flow rates. The research yielded a good comparative result between the experimental and computational process for an optimized flow rate and the effect of the fins. The objective of this paper is to verify the effect of the overlay composite absorber plate material on a solar air heater through experimental and computational fluid dynamics. The experimental setup consists of an absorber plate as an overlay composite of aluminum and copper for enhanced heat transfer. Experiments and CFD analysis were done in three configurations. In configuration one, only the aluminum absorber plate with fins was considered. In configuration two, the overlay composite was considered with copper on the top and aluminum at the bottom as fins, and in configuration three, the overlay composite was considered with aluminum at the top and copper at the bottom as fins. A transient 8 hours CFD analysis was carried out using these configurations. While validating the results it was found that the overlay absorber plate Cu-Al was capable of generating a high outlet temperature Max of 88 °C and capable of generating 83 °C air for 5 hours and had good thermal efficiency when compared to the other materials in the other two configuration. It was found that experimental and computational analysis were in very close agreement, and the margin of error between the experimental and computational processes was less than 8 %.

scholarly journals CONTEMPORARY BIOECONOMICAL PROBLEMS FACING OF THE COMPANIES IN THE TOURISM INDUSTRY

2019 ◽  
Vol 17 (Suppl.1) ◽  
pp. 284-288
Author(s):  
Nikolai Ivanov
Keyword(s):  
Practical Knowledge ◽  
Tourism Industry ◽  
The Other ◽  
Effective Management ◽  
General Direction ◽  
Other Hand ◽  
Tourism Sector

Bulgarian economy is a part of the ongoing worldwide processes of globalization. Of the other part, the importance of the tourism sector of Bulgarian economy is essential. Changing the theoretical and practical knowledge in every field of science should follow the general direction of development. The same goes for accounting. Accountability is related to the effective management of the enterprise. On the other hand, accounting is a "conservative science" but "revolutionary" changed in recent years. This article aims to show the contemporary bioeconomical problems in tourism.

Coordinated righting behaviour in locusts

2001 ◽  
Vol 204 (4) ◽  
pp. 637-648 ◽  
Author(s):  
A.A. Faisal ◽  
T. Matheson
Keyword(s):  
Driving Force ◽  
Flat Surface ◽  
Longitudinal Axis ◽  
Upright Position ◽  
The Body ◽  
The Other ◽  
Legged Robots ◽  
Naturally Occurring ◽  
Key Features ◽  
Low Levels

A locust placed upside down on a flat surface uses a predictable sequence of leg movements to right itself. To analyse this behaviour, we made use of a naturally occurring state of quiescence (thanatosis) to position locusts in a standardised upside-down position from which they spontaneously right themselves. Locusts grasped around the pronotum enter a state of thanatosis during which the limbs can be manipulated into particular postures, where they remain, and the animal can be placed upside down on the ground. When released, thanatosis lasts 4–456 s (mean 73 s) before the animal suddenly becomes active again and rights itself within a further 600 ms. Thanatosis is characterised by very low levels of leg motor activity. During righting, one hind leg provides most of the downward force against the ground that rolls the body around a longitudinal axis towards the other side. The driving force is produced by femoral levation (relative to the body) at the trochanter and by tibial extension. As the animal rolls over, the hind leg on the other side is also levated at the trochanter, so that it does not obstruct the movement. The forelegs and middle legs are not required for successful righting but they can help initially to tip the locust to one side, and at the end of the movement they help stop the roll as the animal turns upright. Individual locusts have a preferred righting direction but can, nevertheless, roll to either side. Locusts falling upside down through the air use both passive and active mechanisms to right themselves before they land. Without active movements, falling locusts tend to rotate into an upright position, but most locusts extend their hind leg tibiae and/or spread their wings, which increases the success of mid-air righting from 28 to 49 % when falling from 30 cm. The rapid and reliable righting behaviour of locusts reduces the time spent in a vulnerable upside-down position. Their narrow body geometry, large hind legs, which can generate substantial dorsally directed force, and the particular patterns of coordinated movements of the legs on both sides of the body are the key features that permit locusts to right themselves effectively. The reliability of autonomous multi-legged robots may be enhanced by incorporating these features into their design.

E-Portals in Dubai and the United Arab Emirates

2011 ◽  
pp. 364-367
Author(s):  
Ian Michael
Keyword(s):  
United Arab Emirates ◽  
Driving Force ◽  
The Other ◽  
Abu Dhabi ◽  
The Government

Technology is seen as a key driving force in the economy within all of the seven emirates that make up the United Arab Emirates (UAE) nation; the seven are Abu Dhabi, Dubai, Sharjah, Ajman, Umm al-Qaiwain, Ras al- Khaimah, and Fujairah. The government of Dubai leads the other emirates in terms of commerce activity, and has taken a strategic view of creating and promoting government portals to achieve this vision. Recently Dubai’s Municipality portal won an award for best content among all other UAE portals.

Measuring Firms' Financial Constraints

2020 ◽  
pp. 276-298
Author(s):  
Carlos Carreira ◽  
João Eira ◽  
Filipe Silva
Keyword(s):  
Financial Constraints ◽  
The Other ◽  
Empirical Literature ◽  
Surprising Result ◽  
Firm Level ◽  
Advantages And Disadvantages ◽  
Indirect Measures ◽  
Large Panel ◽  
Over Time

Measuring firms' financial constraints can prove to be a difficult task for researchers because it is not possible to directly observe whether a firm is financially constrained. This chapter surveys the existing methodologies to measure such constraints at firm level, discussing the advantages and disadvantages of each one. In doing so, firstly, the authors review the direct and indirect measures of firms' financial constraints. Then they test the validity of the most commonly used indices using a large panel of (unlisted) Portuguese firms (2010-2017). The FCP index seems to outperform the other indices in capturing financial constraints of unlisted SMEs. This is not a surprising result, as most of the existing empirical literature on the field deals with listed (US) firms. It is not reasonable to expect that the coefficients of indices remain unchanged across countries and over time. Therefore, the authors propose their (re)estimation to apply them to different economies.

FEM/CFD analysis of wings at different angle of attack

2020 ◽  
Vol 26 ◽  
pp. 1638-1643 ◽  
Author(s):  
Arnav Kulshreshtha ◽  
Sanjeev Kumar Gupta ◽  
Piyush Singhal
Keyword(s):  
Angle Of Attack ◽  
Cfd Analysis

Control of Aeroplanes at Low Speeds

1923 ◽  
Vol 27 (154) ◽  
pp. 473-487
Keyword(s):  
Experimental Work ◽  
The Other ◽  
Research Committee ◽  
General Direction ◽  
Private Person ◽  
Other Hand ◽  
Low Speeds ◽  
Combined Work ◽  
The Way

I must begin by explaining how I come to be giving this lecture. The experimental work with which I shall deal has, for the most part, been done at the N.P.L. and the R.A.E., under the general direction of the Aeronautical Research Committee. The way in which I come to be connected with the work is that I am a member of this Committee and am Chairman of a small panel that was created, some three years ago, by the Committee, to deal with this and other work relating to control and stability. The experiments that I shall describe and the methods of dealing with the results that I shall employ are, therefore, the results of the combined work of a considerable number of people. I can thus claim no special ownership of any of the ideas that I shall use, except in so far as I belong to the panel that has been working upon them. On the other hand I am giving the lecture as a private person, so that any views I express are personal ones and in no sense official.

Towards more effective strategy execution

2020 ◽  
Vol 36 (5) ◽  
pp. 19-21
Keyword(s):  
Driving Force ◽  
Design Methodology ◽  
Reading Time ◽  
The Other ◽  
Effective Strategy ◽  
Strategy Execution ◽  
Content Type ◽  
Pertinent Information ◽  
Overall Performance ◽  
Practical Implications

Purpose This paper aims to review the latest management developments across the globe and pinpoint practical implications from cutting-edge research and case studies. Design/methodology/approach This briefing is prepared by an independent writer who adds their own impartial comments and places the articles in context. Findings Efficiency in both planning and implementation impact on the overall performance of any strategy. Execution is often below standard though, particularly where public sector firms are concerned. But strong leadership can provide the necessary guidance and serve as a driving force to effectively align all the other key components and significantly improve the outcome as a result. Originality/value The briefing saves busy executives and researchers hours of reading time by selecting only the very best, most pertinent information and presenting it in a condensed and easy-to-digest format.

scholarly journals SMEs Managers – A Need for Competence

2014 ◽  
Vol 4 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Katarzyna Szczepańska-Woszczyna
Keyword(s):  
Driving Force ◽  
Formal Education ◽  
Corporate Strategy ◽  
Developed Countries ◽  
Educational Process ◽  
The Other ◽  
Managerial Competencies ◽  
Knowledge And Skills ◽  
Management Staff ◽  
School Curricula

AbstractThe issue of managerial competencies is important due to the fact that it is the management staff who are responsible for developing a corporate strategy, especially as far as SMEs are concerned. A process of competence development in SMEs is worth being investigated as it proceeds differently than in big organizations, the experience of which is used in the presented research. SMEs are the driving force of economy in well developed countries. Their competitiveness is largely determined by their managers’ competencies. They are inextricably linked with the process of education. Education systems and school curricula equip young people with knowledge and skills that are the basis for the later development of professional competencies and the ability to learn throughout one’s life. They are complemented by the process of lifelong learning, various forms of non-formal education and self-education. On the other hand, knowledge of competencies necessary for a given position (in this case managerial) is a source of knowledge for the development of an educational process fulfilling the needs of the labour market. The presented study covers the findings of a test survey, purpose of which was to identify the importance of key managerial competencies, competencies needed by managers in SMEs, and to define a set of competencies that managers wish to develop.

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