Aerodynamic Components Research Articles

The Optimum Flight Speeds of Flying Animals

Conventional models of bird flight combine metabolic, mechanical, and aerodynamic components to calculate the rate of fuel consumption and power required for flight, from which we may derive the optimal speeds flying animals should use in different situations. These models contain the implicit assumption that the metabolic and mechanical components of power output are constant and show no systematic variation with speed. This assumption underlies the optimum flight speeds, optimum climb protocol, maximum endurance and maximum flight range predicted by these models. Here we consider alternatives to the assumption that power is independent of speed and show that if the aerodynamic power output from a constant rate of fuel consumption varies with flight speed, then the optima derived from current models of animal flight need to be revised. In some cases (e.g. optimum flight speeds) the current models give answers that are only quantitatively wrong, but in some cases (e.g. optimal cruising altitude) current models give answers that are qualitatively wrong.

Aerodynamic effects of the angle of attack on a rectangular prism

In the past, in-line vibration caused by low-velocity flows proved to be potentially very destructive. Therefore, in this paper, an experimental investigation concerning the aerodynamic properties of a 2×1 rectangular cross-sectional prism is presented. The 2×1 cross section was chosen specifically for the in-line vibration demonstrated by this shape in past studies. Through the use of wind tunnel tests, the aerodynamic response to various angles of attack were examined. Specifically, Strouhal numbers and vibrational response were measured at a number of different angles of attack for both two- and three-dimensional models. In addition, static aerodynamic force components and vortex formation around the prism were investigated for angles of 0° and 90°.

Behavioral response to ultrasound by the tiger beetle Cicindela marutha dow combines aerodynamic changes and sound production.

Tethered flying tiger beetles, Cicindela marutha, respond to trains of bat-like ultrasonic pulses with a short-latency, multi-component behavior. The head rolls to one side, the metathoracic legs kick to the opposite side, the elytra swing backwards towards the hindwings and pronate, the hindwings increase their stroke excursion and frequency, and the plane of the hindwing motion tilts forward. In addition, the beetles produce trains of ultrasonic clicks typically containing 100-200 clicks in response to a 1 s stimulus. The clicks average 85-90 dB SPL at 2 cm. The latencies for hindwing changes and elytra swing in response to stimuli more than 10 dB over threshold are 90-110 ms; the latency to clicking is 120-150 ms. Neither the head roll nor the leg kick appears to be directional relative to the sound source. The behavioral response is broadly tuned with greatest sensitivity at 30-60 kHz and mean behavioral thresholds of 75-80 dB SPL. Physiological audiograms from the auditory afferents show substantially greater sensitivity and sharper tuning than the behavioral response, which suggests that tiger beetles may use their hearing in other contexts as well as during flight. The combination of aerodynamic components and arctiid-month-like clicking may provide these insects with a powerful defense against attack by echolocating bats.

Development study on ATREX engine

This is the status report of the development study on ATREX engine (Air Turbo Ramjet) that is now under way in the Instutute of Space and Astronautical Science (ISAS) in cooperation with the Ishikawajima Harima Heavy Industries (IHI), the Kawasaki Heavy Industries (KHI), the Mitsubishi Heavy Industries (MHI). ATREX engine will be applied for the propulsion system of fly-back booster of TSTO space plane. ATREX is the fan-boosted ramjet producing the effective thrust from sea level static to flight Mach number 6. ATREX is worked on the expander cycle with precooling incoming air as shown in Fig.1. ATREX employs the tip turbine configuration which allows compactness and light weight of turbo machinery and the variable geometry airintake and plug nozzle which allows the wide range flight conditions. ATREX development study has been conducted with the sea level static tests since 1990. ATREX engine for tests is the scaled model designated by “ATREX-500” of which fan inlet diameter is 300 mm and overall length 2,200 mm. From 1992 have been performed the wind tunnel tests on the primary aerodynamic components such as the axisymmetric variable geometry air intakes, the precoolers and the variable geometry plug nozzles. The application study on advanced carbon-carbon composite for the tip-turbine and fan assembly has been conducted. This study status is presented in the another session of this IAF congress 1. The flight test of ATREX is now planning to verify the engine performance and functions in the practical flight conditions by using an unmanned flying test bench. In 1995 was tested ATREX-500 installing the precooler under the sea level static conditions to examine the engine performance and the icing problem on the precooler. The present paper addresses primarily the test results of precooled ATREX engine.

96/03876 ABB electrical equipment on board the luxury liner ‘MV Oriana’

One critical task in any wind power interconnection study involves the modelling of wind turbines. This paper provides the most basic yet comprehensive time–domain wind turbine model upon which more sophisticated models along with their power and speed control mechanisms, can be developed. For this reason, this paper concentrates on the modelling of a fixed-speed wind turbine. The model includes turbine's aerodynamic, mechanical, and electrical components. Data for the rotor, drive-train, and electrical generator are given to allow replication of the model in its entirety. Each of the component-blocks of the wind turbine is modelled separately so that one can easily expand the model to simulate variable-speed wind turbines or customise the model to suit their needs. Then, an aggregate wind turbine model, or wind farm, is developed. This is followed by four case studies to demonstrate how the models can be used to study wind turbine operation and power grid integration issues. Results obtained from the case studies show that the models perform as expected.

96/03880 Application of fuel cell technology to health care institutions in rural and urban environments

One critical task in any wind power interconnection study involves the modelling of wind turbines. This paper provides the most basic yet comprehensive time–domain wind turbine model upon which more sophisticated models along with their power and speed control mechanisms, can be developed. For this reason, this paper concentrates on the modelling of a fixed-speed wind turbine. The model includes turbine's aerodynamic, mechanical, and electrical components. Data for the rotor, drive-train, and electrical generator are given to allow replication of the model in its entirety. Each of the component-blocks of the wind turbine is modelled separately so that one can easily expand the model to simulate variable-speed wind turbines or customise the model to suit their needs. Then, an aggregate wind turbine model, or wind farm, is developed. This is followed by four case studies to demonstrate how the models can be used to study wind turbine operation and power grid integration issues. Results obtained from the case studies show that the models perform as expected.

ONERA three-dimensional icing model

A three-dimensional icing model has been developed at ONERA to calculate ice accretion shapes for aerodynamic components that can not be predicted using conventional two-dimensional codes. It is described, emphasizing the original parts with respect to the two-dimensional existing models. The model includes Euler inviscid flow calculation. Droplet trajectories are calculated in a three-dimensional grid. The remesh on the leading edge is adapted to follow aerodynamics singularities. The boundary layer is calculated using a mixing length formulation to model the wall roughness influence on convective heat transfer. Runback paths are integrated. The heat balance is calculated in a grid created along the runback paths. The domain of validity of the three-dimensional icing code is described; compared with the two-dimensional model this domain is wider, especially for high speeds. The three-dimensional model is shown to simulate well a uniform ice deposit on a three-dimensional rotor blade tip. Then, a comparison of the three- and two-dimensional codes on an infinite swept wing shows that the corrected two-dimensional code predicts the catch efficiency but not the ice shape. Finally, it is shown that the continuum flux hypothesis prevents the three-dimensional model from simulating correctly the lobster tail ice shape (nonuniform ice deposit).

Performance prediction for Olympic kayaks.

This paper sets out the effects of the various factors which determine the speed of racing kayaks and canoes, with the aim of identifying the areas most likely to lead to improvements. The friction, wave and aerodynamic components of hull drag are first described in terms of the hull parameters, in order to provide accurate predictions of propulsive power as a function of hull speed. The generation of thrust by paddling is described via the mechanics of vortex-ring wakes, in order to determine the propulsive efficiency in terms of the parameters describing the blade and stroke. Equating the thrust and drag then leads to reliable estimates of the mechanical power actually delivered by a canoeist. The earlier analysis then leads to a predictive model for hull speed in terms of all the parameters describing the hull and blade performance. This is used to determine the sensitivity of hull speed to small changes in each parameter, enabling the most important factors to be identified. The paper concludes with a discussion of the various improvements to kayaks that have actually appeared in recent years, and uses the earlier analysis to explain and predict the resulting speed changes.

ULTRA LIGHT ELECTRIC VEHICLES (EV)

While this project reviewed the status of EV propulsion worldwide, and included European, American, and Japanese electric vehicles and the new Zebra sodium nickel chloride battery introduced by AEG of Daimler Benz at the September 1993 Frankfurt IAA motor show, and the November 1993 Tokyo motor show, this paper is limited in scope to showing results of a mathematical comparison which permits comparative assessment of 1993 EV automotive acceleration performance and the effects of vehicle configuration on the aerodynamic skin friction component of the total aerodynamic drag coefficient. Conclusions are: the major automobile manufacturers have been responsive, creative, and synergistic in developing and demonstrating significant improvements in acceleration performance and vehicle styling configuration strategies which may permit early deployment of ultralight electric vehicles with increased range. Consequently, the battery "Electric Vehicle" now has a brighter future.

Incorporating aerodynamic and laryngealcomponents into task dynamics

Aerodynamic and laryngeal components were added to the task-dynamic model to make it a more complete model of speech production. New tract variables included were subglottal pressure, transglottal pressure, and a quantity giving fundamental frequency in sonorant conditions. New articulators included total force on the lungs, generalized laryngeal tension, and supralaryngeal volume. Simulations of /VCV/ sequences, where C was either a voiced or a voiceless aspirated stop, demonstrated the usefulness of these additions.

再突入物体まわりの遷音速流れ

Surface and back pressures, and three aerodynamic force components for two models of reentry vehicle: the cocoon type and the pan type, were measured at three transonic flow speeds: Mach number of 0.6, 0.7 and 0.8. Schlieren photographs were also taken to visualize the flow pattern. Comparing the results of force measurement with those calculated from measured pressure distributions, reasonable agreement was obtained. The Euler equations were also solved for a case with attack angle of 0 deg and Mach number of 0.8. In spite of good agreement on pressure distribution along the forward part of model, there was some discrepancy in back pressure between numerical calculation and experiment, which produced difference in drag coefficient. When the back pressure was then replaced by the experimental data, reasonable agreement of drag coefficient was obtained between them. As a result, it turned out that the pan type was more appropriate as a reentry vehicle than the cocoon type.

Apparatus for cooling and cleaning raw gases from coal gasifiers

This is the status report of the development study on ATREX engine (Air Turbo Ramjet) that is now under way in the Instutute of Space and Astronautical Science (ISAS) in cooperation with the Ishikawajima Harima Heavy Industries (IHI), the Kawasaki Heavy Industries (KHI), the Mitsubishi Heavy Industries (MHI). ATREX engine will be applied for the propulsion system of fly-back booster of TSTO space plane. ATREX is the fan-boosted ramjet producing the effective thrust from sea level static to flight Mach number 6. ATREX is worked on the expander cycle with precooling incoming air as shown in Fig.1. ATREX employs the tip turbine configuration which allows compactness and light weight of turbo machinery and the variable geometry airintake and plug nozzle which allows the wide range flight conditions.ATREX development study has been conducted with the sea level static tests since 1990. ATREX engine for tests is the scaled model designated by “ATREX-500” of which fan inlet diameter is 300 mm and overall length 2,200 mm. From 1992 have been performed the wind tunnel tests on the primary aerodynamic components such as the axisymmetric variable geometry air intakes, the precoolers and the variable geometry plug nozzles. The application study on advanced carbon-carbon composite for the tip-turbine and fan assembly has been conducted. This study status is presented in the another session of this IAF congress1.The flight test of ATREX is now planning to verify the engine performance and functions in the practical flight conditions by using an unmanned flying test bench. In 1995 was tested ATREX-500 installing the precooler under the sea level static conditions to examine the engine performance and the icing problem on the precooler.The present paper addresses primarily the test results of precooled ATREX engine.

Progress in high-lift aerodynamic calculations

The current work presents progress in the effort to numerically simulate the flow over high-lift aerodynamic components, namely, multi-element airfoils and wings in either a take-off or a landing configuration. The computational approach utilizes an incompressible flow solver and an overlaid chimera grid approach. A detailed grid resolution study is presented for flow over a three-element airfoil. Two turbulence models, a one-equation Baldwin-Barth model and a two equation k-omega model are compared. Excellent agreement with experiment is obtained for the lift coefficient at all angles of attack, including the prediction of maximum lift when using the two-equation model. Results for two other flap riggings are shown. Three-dimensional results are presented for a wing with a square wing-tip as a validation case. Grid generation and topology is discussed for computing the flow over a T-39 Sabreliner wing with flap deployed and the initial calculations for this geometry are presented.

Aeroelastic response of composite rotor blades considering transverse shear and structural damping

The effects of transverse shear deformations and structural damping on the flutter phenomena of a composite rotor blade in hover have been investigated using the finite element method. First-order shear deformation theory with rotary inertia effects and a damped element model of composite laminates are employed for the structural formulation. A quasisteady aerodynamic theory with a dynamic inflow model is used. Torsion-related out-of-plane warping and noncirculatory aerodynamic components are also incorporated in the formulation. Using these structural and aerodynamic tools, several numerical studies are carried out, first to validate the current approach and second to show the effects of transverse shear deformations and structural damping on the aeroelastic stability of a composite rotor as a function of fiber orientation. The predictions derived by the frequency analysis of this model are found to be more accurate than those given by an alternative approach compared with experimental data. It is shown that the transverse shear flexibility tends to lower the frequency of the rotor, and generally has a destabilizing effect on the lag mode and a stabilizing effect on the flap mode. It is also presented that the magnitude of structural damping can be controlled by changing ply orientation angle. CT cd c, EA

Three-Dimensional Navier-Stokes Analysis of Tip Clearance Flow in Linear Turbine Cascades

A three-dimensional viscous flow code was used to study the tip clearance flow in linear turbine cascades. Two test cases with detailed measurements were used for validation. The flow properties inside the tip gap, such as static pressure, velocity, and angle, were compared with the data. The blade loading at different span locations and the downstream flowfield properties, such as loss and angle, were also compared with the data. The clearance flow phenomena, such as leakage vortex, changing of loss distribution, and flow underturning, were predicted by the numerical code. This code not only can be used as an analysis tool to study tip clearance effects in real turbine blade rows but also can be used as a design tool to design the turbine components. HE effort expended to develop a modern gas turbine engine is substantial. A significant portion of this effort is devoted to the preliminary design of aerodynamic components and subsequent modification by iteration to achieve the final design that meets the required engine performance goals. With the rapid growth in computer technology, computational fluid dynamics (CFD) codes are used as an analysis tool to help engineers understand the flow features in turbine components. Use of CFD codes that can accurately predict operation char- acteristics of turbomachiner y components will result in con- siderable reduction of development effort and provide in- creased performance. The validation of a CFD code is necessary to use it as a design tool. To evaluate the performance of the CFD code, reliable experimental data are needed. The data should provide detailed information for flow features in turbine components. Unshrouded turbine rotors operate with a tip clearance between the blade tip and the casing. The fluid that leaks between the blade tip and casing causes large efficiency losses. The tip leakage flow also changes the loss distribution, exit flow angle, and loading. Therefore, it is important for the turbomachinery designer to understand and predict the tip clearance flow phenomena. Hah,1 Pouagare and Delaney,2 and Dawes3 predicted tip clearance flow using a three-dimensional Navier-Stokes code; however, all compressor blade rows are calculated with the assumption of zero thickness on the blade tip. They used one grid line and periodic conditions for the flow inside the tip clearance region. This model is satisfactory for very thin air- foils, such as those found at the tip of a transonic compressor rotor. However, thick airfoils, found in turbine blades, re- quire the full flowfield resolution in the tip gap region. Moore and Moore4 predicted the tip clearance flow in a linear turbine cascade with the three-dimensional incompressible Navier- Stokes code. However, the flow in turbomachiner y compo- nents is usually compressible. In this study, a numerical code that solves three-dimensional, compressible Navier-Stokes

Commercial turbofan engine exhaust nozzle flow analyses

The recently developed three-dimensional code is able to perform a computational investigation of complex aircraft aerodynamic components. This code was developed for solving the simplified Reynolds-averaged NavierStokes equations in a three-dimensional multiblock/mul tizone structured mesh domain. The present analysis was applied to commercial turbofan exhaust flow systems. Solution sensitivity to grid density is presented. Laminar flow solutions were developed for all grids, and two-equation k-£ solutions were developed for selected grids. Static pressure distributions, mass flow, and thrust quantities were calculated for on-design engine operating conditions. Good agreement between predicted surface static pressures and experimental data was observed at different locations. Mass flow was predicted within 0.2% of experimental data. Thrust forces were typically within 0.6% of experimental data.

Double linearization theory of three-dimensional cascades with vibrating blades under spanwise-nonuniform mean loading, II: Supersonic flow

The double linearization theory is extended to a supersonic straight cascade placed between parallel plane end walls, and the effect of spanwise-nonuniform mean loading upon the unsteady aerodynamic force for vibrating blades is studied. The three-dimensional version of the theory takes account of the unsteady spanwise aerodynamic force component due to spanwise nonuniformities of the mean blade loading and the vibration amplitude. The unsteady shock displacement effect on the unsteady aerodynamic force is found to be quasi-two-dimensional. Numerical examples are presented to demonstrate several features of the unsteady aerodynamic response ascribable to the effects of the spanwise-nonuniform angle of attack, camber and thickness of blades. The effect of nonuniformity of camber or thickness is larger than that of angle of attack. To attain a large steady loading on the stability boundary of the first mode bending vibration, it is advantageous to design blades with the angle of attack decreasing and the chamber and thickness increasing from hub to tip.

A new principle for a short-duration six component balance

The presented principle of a sting balance applying semiconductor strain gauges bears a number of advantages in comparison with classical strain gauge balances. Simultaneous, highly time resolved measurement of all six aerodynamic force components is possible. The manufacturing is comparatively easy, a milling machine is sufficient to achieve reasonable accuracy. The balance needs only little space, which makes it suitable for small and especially for short models. The disadvantages of semiconductor strain gauges like zero drift and temperature effects do not play a significant role during the test time of five milliseconds. However, they have to be taken into account during the long lasting calibration process. The attachment of the model to the cross is critical with regard to preloadings and hysteresis. Therefore a connecting part is used between balance and model, which should not be removed once the balance is calibrated. The model should be attached to the balance so that the centre of mass is located at the origin of the coordinate system shown in Fig. 2. Then, the moment of inertia with respect to the balance fixed coordinate system is minimal, whereas the natural frequencies of the rotating degrees of freedom are maximized. If the flow over a model is studied the coordinate system only has to be rotated to obtain the aerodynamic forces. Furthermore, gauging and wiring of the strain gauges is uncomplicated, all locations of the gauges are easy to reach. As the construction is compact and of high stiffness it may withstand high loads. The existing balance has a design load of 1,000 N. Strain gauges with a gauge factor of k=130 were used. With an amplification factor of 10,000 even forces below 1 N can be observed, using an appropriate amplifier (e.g. “2311 Signal Conditioning Amplifier”, Vishay Measurements Group). The accuracy of the measurement mainly depends on the efforts invested in the calibration and data processing. With a suitable algorithm as proposed by Schnabl (1987), an accuracy in the order of one percent should be possible. So far the balance has not been applied for measurements on a model, but a number of tests is being made to investigate the natural frequencies and short time response. The results of these tests will lead to the final geometry of the balance and its attachment to the model. It is hoped to have the next prototype manufactured, gauged and calibrated by the end of this year. First results of the investigation of a model with the balance might be presented in 1990.

Radiated sound-pressure levels and sound source locations on the German ICE high-speed train

The German ICE high-speed train demonstrated on 1 May 1988 that speeds up to 406 km/h can be attained using conventional wheel/rail technology. High-speed railway vehicles such as the ICE generate strong aerodynamic sound sources that overwhelm the noise contribution produced by wheel/rail interaction, particularly when the wheels have been acoustically treated. If radiated noise levels are to be held to a minimum, the aerodynamic characteristics of such vehicles have to be optimized. The ICE has been designed in this way. Sound-source location measurements were carried out using a line array of 15 microphones positioned along the wayside. The first results of this study will be discussed in the present paper for train speeds up to 300 km/h. Wayside noise measurements made during the record-breaking run on 1 May 1988, when a speed of 406.9 km/h was attained, are also presented. The aerodynamic component of radiated noise is separated from that due to wheel/rail interactions, and the resulting analysis is shown to be also applicable to maglev vehicles. Also at Technische Universität Berlin, Inst. füt Techn. Akustik.

EXPERIMENTAL INVESTIGATION OF NONLINEAR AERODYNAMIC DAMPING OF PARTIAL AIRPLANE ASSEMBLY

Low speed wind tunnel testing of partial assemblies of aircraft fuselage and its horizontal tail surfaces are performed using a special dynamic stability balance. Experiments were aimed for investigating the effects of airplane aerodynamic components on the nonlinear behaviour of pitch damping in a range of moderate angles of attack. The function of balance is based on the method of forced pitch oscillations of geometrically similar model in straight parallel air flow. Damping coefficients are determined from analysis of motion records. Measurements are performed in range of flow velocities at different oscillation frequencies. Obtai-ned results proved linear dependence of damping derivative on flow velo-city, and independence of the nondimensional damping in pitch derivate on the oscillations nondimensional frequency. Strong nonlinearity in the dependence with angle of attack is observed, which is related to the creation and seperation of vortices on fuselage sides. The research pro-ved strong favourable contribution of quasi-slender fuselages to the nonlinear character of aerodynamic forces of their aircraft assemblies.