...Research on Aerodynamic Drag Reduction by Vortex Generators Masaru KOIKE* Tsunehisa NAGAYOSHI* Naoki HAMAMOTO* Abstract One of the main causes of aerodynamic drag for sedan vehicles is the separation of flow near the vehicle’s rear end. To delay flow separation, bump-shaped vortex generators are tested for application to the roof end of a sedan. Commonly used on aircraft to prevent flow separation, vortex generators themselves create drag, but they also reduce drag by preventing flow separation at downstream. The overall effect of vortex generators can be calculated by totaling the positive and negative effects. Since this effect depends on the shape and size of vortex generators, those on the vehicle roof are optimized. This paper presents the optimization result, the effect of vortex generators in the flow field and the mechanism by which these effects take place. Key words: Body, Aerodynamics, Aerodynamic Devices, Flow Visualization, Computational Fluid Dynamics (CFD) 1. Introduction To save energy and to protect the global environment, fuel consumption reduction is primary concern of automotive development. In vehicle body development, reduction of drag is essential for improving fuel consumption and driving performance, and if an aerodynamically refined body is also aesthetically attractive, it will contribute much to increase the vehicle’s appeal to potential customers. However, as the passenger car must have enough capacity to accommodate passengers and baggage...
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...objects. A wind tunnel consists of a closed tubular passage with the object under test mounted in the middle. A powerful fan system moves air past the object; the fan must have straightening vanes to smooth the airflow. The test object is instrumented with a sensitive balance to measure the forces generated by airflow; or, the airflow may have smoke or other substances injected to make the flow lines around the object visible. Full-scale aircraft or vehicles are sometimes tested in large wind tunnels, but these facilities are expensive to operate and some of their functions have been taken over by computer modelling. In addition to vehicles, wind tunnels are used to study the airflow around large structures such as bridges or office buildings. The earliest enclosed wind tunnels were invented in 1871; large wind tunnels were built during the Second World War. Contents • 1 Theory of operation • 2 Measurement of aerodynamic forces • 3 History o 3.1 Origins o 3.2 World War Two o 3.3 Post World War Two • 4 How it works o 4.1 Pressure measurements o 4.2 Force and moment measurements • 5 Flow visualization o 5.1 Qualitative methods • 6 Classification o 6.1 Aeronautical wind tunnels 6.1.1 High Reynolds number tunnels 6.1.2 V/STOL tunnels 6.1.3 Spin tunnels o 6.2 Automobile tunnels o 6.3 Aeroacoustic tunnels • 7 List of wind tunnels o 7.1 Aquadynamic flume o 7.2 Low-speed oversize liquid testing o 7.3 Fan testing o 7.4 Wind engineering testing • 8 See also ...
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...modular structural, finite difference groundwater flow model • Most widely used groundwater model • Steady state or transient saturated flow • Currently MODFLOW 2000, 2005 available Mathematical model 3D groundwater flow in the saturated heterogeneous and anisotropic porous media h h h h K xx K yy K zz W Ss x x y y z z t where: Kxx, Kyy, Kzz = values of hydraulic conductivity along xyz axes (LT-1) h = total head (L) W = Sources and sinks (T-1) Ss = Specific storage (L-1) t = time (T) Finite Difference Model Model grid: • Rows, columns, layers • Count from the upper left corner Finite Difference Model Model grid: • Cell-Centered • Horizontal grid: rectangular cell varies with size Finite Difference Model Model grid: • Cell-Centered • Vertical layers: thickness varies MODFLOW Packages • Basic • Flow Package – BCF – LPF – HUF • River • Drain • Well • Recharge • Evapotranspiration • Changing Head Boundary • General Head Boundary • Horizontal Flow Barrier • Stream-Aquifer Interaction • Solvers • Output Control MODFLOW Basic Package (BAS) Functions: • Discretization of model domain; • Selection of major options and the designation of their input unit numbers; • Specifying initial and boundary conditions, and • Discretization of time. MODFLOW Basic Package (BAS) Definition of model grids and boundaries • Number of rows, columns and layers • Cells outside model domain are marked as...
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...Queen Mary University of London School of Engineering and Materials Science Laboratory Report DEN5242 - Aerothermodynamics of Fluid Flows Flow Around a Cylinder Rehad Islam Choudhury Student Number: 120100288 20th November 2014 Abstract A cylinder is placed inside a closed circuit wind tunnel to observe the effects of flow around it. The cylinder is tested for smooth (i.e. laminar) and turbulent flow. The cylinder has pressure tappings around its centre which are connected to an inclined multi-tube methylated spirit manometer. Pressure readings are taken all around the cylinder for both flow conditions and graphs of pressure coefficient, Cpϕ relative to angular degrees, ϕ° as well as a graph to approximate the coefficient of drag, CD is also produced. The report highlights the similarities and difference between the two different flows as well comparing them to a theoretical flow. Various calculations are done to work out variables like the tunnel calibration constant, K, the free stream velocity, V∞ and the Reynolds number of each flow. In the discussion, the errors of the experiment are outlined and comments are made for improvements. Contents Abstract 2 1. Introduction 3 2. Apparatus 3 3. Experimental Procedure 3 4. Results & Calculations 4 5. Discussion 9 5.1 Results & Comparison 9 5.2 Calculations & Further Comparison 9 5.3 Errors & Improvements 10 6. Conclusion 10 7. Reference 10 1. Introduction An experiment...
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...slides laterally past another, so no vertical displacement takes place E) As oceanic plates spread apart at mid oceanic ridges, they must slide past other plates, along transform faults 3. What is the lithosphere and asthenosphere? (defined by strength) The lithosphere is a zone of strength, where if you apply enough stress, it will break causing an earthquake. The lithosphere is 0-100 km thick between oceans, and 100-150 km thick between continents. The lithosphere consists of the crust plus the uppermost part of the mantle. The asthenosphere is a zone of weakness, where if you apply enough stress, the asthenosphere will flow. It is 200 km thick and occurs beneath the lithosphere. Lithospheric plates move on top of asthenosphere. The asthenosphere is the portion of the mantle in which rock can flow. 4. What are the internal chemical layers in the Earth and how are they defined? Crust- there are two basic types of crust. The oceanic crust is...
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...greater in the middle of the day than at morning or night and is greater in winter than in summer. In fine weather, the potential increases with altitude at about 30 volts per foot (100 V/m). The atmospheric medium, by which we are surrounded, contains not only combined electricity, like every other form of matter, but also a considerable quantity in a free and uncombined state; sometimes of one kind, sometimes of the other; but as a general rule it is always of an opposite kind to that of the Earth. Different layers, or strata, of the atmosphere, located at only small distances from each other, are frequently found to be in different electric states. The phenomena of atmospheric electricity are of three kinds. There are the electrical phenomena of thunderstorms and there are the phenomena of continual electrification in the air. The phenomena of the polar auroras constitute a third branch of the subject. The measurements of atmospheric electricity can be seen as measurements of difference of potential between a point of the Earth's surface, and a point somewhere in the air above...
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...Abstract – Atherosclerotic plaque is the major cause of coronary heart artery diseases. Heart artery plaque layer analysis is one of the most important and challenging problem, which can be determined by using Intravascular Ultrasound (IVUS) Cross Sectional images, which is an excellent ultrasound study system for extracting and to easily identifying the plaque layer by using the shape parameter measurements. This paper presents and elucidates the new approach to find out the coronary artery plaque with the help of the artery cross sectional layers determination, which are adventitia, media, intima and lumen layers. This system measures the layer’s performance to make the clear way to identifying the plaque layer, which proposes a new method...
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...physical aspects of shock wave/boundary layer interactions Jean Délery · Jean-Paul Dussauge Received: 9 February 2009 / Accepted: 29 June 2009 / Published online: 26 July 2009 © Springer-Verlag 2009 Abstract When the flow past a vehicle flying at high velocity becomes supersonic, shock waves form, caused either by a change in the slope of a surface, a downstream obstacle or a back pressure constraining the flow to become subsonic. In modern aerodynamics, one can cite a large number of circumstances where shock waves are present. The encounter of a shock wave with a boundary layer results in complex phenomena because of the rapid retardation of the boundary layer flow and the propagation of the shock in a multilayered structure. The consequence of shock wave/ boundary layer interaction (SWBLI) are multiple and often critical for the vehicle or machine performance. The shock submits the boundary layer to an adverse pressure gradient which may strongly distort its velocity profile. At the same time, in turbulent flows, turbulence production is enhanced which amplifies the viscous dissipation leading to aggravated performance losses. In addition, shock-induced separation most often results in large unsteadiness which can damage the vehicle structure or, at least, severely limit its performance. The article first presents basic and well-established results on the physics of SWBLI corresponding to a description in terms of an average two-dimensional steady flow. Such a description allows...
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...in airships with varied applications in the field of advertisement, cargo transport, surveillance, communication systems, extending Internet access in remote areas is the primary motivation for this study. The estimation of aerodynamic characteristics is important for the design of control and propulsion systems of the airship. Airship analysis has traditionally been done using inviscid potential flow methods coupled with boundary layer corrections based on integral momentum methods have been used to estimate the drag coefficient of airships [1-4]. However, the application of these methods is strictly restricted to non-separating flows and flows at zero or small angles of attack. In real-life applications, the airship does encounter flow separation at large angles of attack, both of which have critical influence on the aerodynamic characteristics of the airship. Though some attempts have been made earlier to develop advanced boundary-layer methods, which can capture some flow separation effects [5], their success has been limited to merely capturing some qualitative features of the flow. Previous work carried out by Suman et al. [6]...
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...UNIVERSITY OF AUCKLAND DEPARTMENT OF ENGINEERING ENCI790 RESEARCH PROPOSAL: “An evaluation and survey of methods available for converting biomass into fuels” Candidate: Surya Sappa Supervisors: Professor John Chen Doctor Robert Kirkpatrick ABSTRACT Biofuel technologies have become more and more prominent in addressing the need for a continuous supply of fuels. Biofuels are fuels that are produced through the biological process of converting biomass/biowaste into a fuel source to reduce the negative impacts faced by fossil fuels combustion (reduction in greenhouse gasses) and availability of supply. Biofuels can be derived from a wide variety of biomass, and are categorised into four generations: First generation biofuels are made from sugars, starches, oil, and animal fats that are converted into fuel using already-known processes or technologies. These fuels include biodiesel, bioalcohols, ethanol, and biogases, like methane captured from landfill decomposition. Second generation biofuels are made from non-food crops or agricultural waste, especially ligno-cellulosic biomass like switch-grass, willow, or wood chips. Third generation biofuels are made from algae or other quickly growing biomass sources. Fourth generation biofuels are made from specially engineered plants or biomass that may have higher energy yields or lower barriers to cellulosic breakdown or are able to be grown on non-agricultural land or bodies of water...
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...Table of Contents Abstract 2 Introduction 2 The Fire Problem 2 Methodology 5 Results and discussion 6 Processes of flame spread 7 Diffusion flame spread 8 Thermal Model 8 Transition to Turbulence 10 References 13 Abstract The fires problem is one of the hazard pose a threat to life and property. Flames behave differently under various conditions which include: the oxygen available, combustible material, orientation of surfaces, etc. this a complex phenomena which is influenced by multiple factors that includes ignition, heat release rate, flame spread and the generation of different products of combustion like carbon IV oxide and carbon II oxide. The research was performed by studying various sources in the library and in the internet and also performing experiments to simulate a real life situation. Introduction The Fire Problem The flammability of a material is a complex event which is influenced by multiple factors that includes ignition, heat release rate, flame spread and the generation of different products of combustion like carbon IV oxide and carbon II oxide. In order to better protect the people and property from risk posed by the unwanted fires, it become necessary to understands all these factors under different conditions. Babrauskas and Vytenis 1992 suggested that heat release rate is the main variable in fire hazard; but Kashiwagi and Ito argued effectively that, the flame spread over the surface...
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...of gas pressure and flow rate parameters on fuel cell performance. The fuel cell was operated at various pressure and flow rates that were regulated by mass flow controllers placed upstream of the stack. In this study, four types of control factors considered were: pressures of the fuel and oxidant and the flow rates of the fuel and oxidant to select optimize condition for fuel cell operation. Each factor has two levels, leading to a full factorial design requiring 24 experiments leading to a 16 experiments and fractional factorial experiments, 24-1, leading to 8 experiments. The experimental data collected were analysed by statistical sensitivity analysis by checking the...
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...ES8005 – Chapter 1 A system is any portion of the universe that can be isolated for the purpose of observing & measuring changes A system must have a boundary that sets it apart from its surroundings 3 basic types of systems 1. Isolated system * Boundary prevents the system from exchanging BOTH matter & energy with its surroundings. * Both matter and energy within the system are fixed & finite because none can enter and none can leave the system. * Imaginary – impossible for any real boundary to be so perfectly insulated that energy can neither enter or escape. 2. Closed system * Boundary permits the exchange of energy, but not matter within its surroundings * Matter within the system is finite but energy is exchangeable in and out of the system 3. Open system * Boundary permits exchange of both energy and matter * Ie. Island. * Open systems are more difficult to study because they have more potential for uncontrolled variation Box model * A model is a representation of something. * A box model can show the essential features of a system. i. The process by which matter enters & leaves the system and the rates at which they do so ii. The process which matter moves among the various parts of the system internally & the rates at which this happens iii. The amount of matter (or energy) in the system at a given time and its distribution within the system * The amount of matter...
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...12,756 km (7,972 mi). The Earth's interior consists of rock and metal. It is made up of four main layers: 1) the inner core: a solid metal core made up of nickel and iron (2440 km diameter) 2) the outer core: a liquid molten core of nickel and iron 3) the mantle: dense and mostly solid silicate rock 4) the crust: thin silicate rock material The temperature in the core is hotter than the Sun's surface. This intense heat from the inner core causes material in the outer core and mantle to move around. The movement of material deep within the Earth may cause largeplates made of the crust and upper mantle to move slowly over the Earth’s surface. It is also possible that the movements generate the Earth's magnetic field, called the magnetosphere. ------------------------------------------------- Hotspot (geology) From Wikipedia, the free encyclopedia Diagram showing a cross section though the Earth'slithosphere (in yellow) withmagma rising from the mantle(in red) In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. They may be on, near to, or far from tectonic plate boundaries. Currently, there are two hypotheses that attempt to explain their origins. One suggests that they are due to hot mantle plumes that rise as thermal diapirs from the core-mantle boundary.[1] An alternative hypothesis postulates that it is not high temperature that causes the volcanism...
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...Attack and lift 5 The Flow of Fluids 6 Lift 6 Resulting Lifting Force 7 Pressure Distribution 7 Center of Pressure 8 Calculations & Results 8 Discussion 13 Conclusion 13 References 13 Introduction Aerodynamics is a branch of mechanics concerned with the motion of a fluid continuum the action of applied forces. The motion and general behaviour of a fluid is governed by the fundamental laws of classical mechanics and thermodynamics and plays an important role in such diverse fields as biology, meteorology, chemical engineering, and aerospace engineering. An introductory text on fluid mechanics, such as , surveys the basic concepts of fluid dynamics and the various mathematical models used to describe fluid flow under different restrictive assumptions. The objectives of this experiment are to investigate the way in which the static pressure varies on the surface of an aerofoil in low speed flow, and to deduce the lift force acting on the aerofoil. An aerofoil with a symmetrical section is used for the experiment, which is conducted in a wind tunnel at a wind speed low enough for the flow to be treated as incompressible. From the measured distribution of surface pressure around the aerofoil at a small angle of incidence, the lift will be calculated by numerical integration, and compared with the predictions of inviscid flow theory. The measured chord wise load distribution will also be compared with the results given for inviscid flow by thin aerofoil theory...
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