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This study was led in collaboration with the French Space Agency ( CNES) and the Rocket Engine Division of Snecma. The main aims were the simulations and the analyses of cavitating flows in the rocket engine turbopump inducers, where the operating fluids are LH2 and LOx under cryogenic conditions. A [rho](P, T) state law modeling the cavitation phenomenon was integrated by the laboratory LEGI in the commercial computational fluid dynamics (CFD) code FINE/TURBO[TM], developed by Numeca International. Various 3D numerical results are given for an inducer geometry and comparisons are made with experimental data (head drop curves) obtained by NASA. [DOI: 10.1115/1.4002886]

Twist optimization of a helicopter rotor in hover is presented using compressible computational fluid dynamics as the aerodynamic model. A domain-element shape parameterization method has been developed, which solves both the geometry control and the volume mesh deformation problems simultaneously, using radial basis function global interpolation. This provides direct transfer of domain-element movements into deformations of the design surface and the computational fluid dynamics volume mesh, which is deformed in a high-quality fashion. The method is independent of mesh type (structured or unstructured), and it has been linked to an advanced parallel gradient-based algorithm, for which independence from the flow solver is achieved by obtaining sensitivity information by finite differences. This has resulted in a flexible and versatile modular method of wraparound optimization. Previous fixed- wing results have shown that a large proportion of the design space is accessible with the parameterization method, and heavily constrained drag optimization demonstrated significant performance improvements. In the present work, the method is extended to a rotor blade, and this is optimized for minimum torque in hovering flight with strict constraints. Twist optimization results are presented for three tip Mach numbers, and the effects of different parameterization levels are analyzed using various combinations of two levels: global and local. Torque reductions of over 12% are shown for a fully subsonic case, and for over 24% for a transonic case, using only three global and 15 local twist parameters. DOI: 10.2514/1.C000316

A spring-loaded pressure safety valve (PSV) is a key device used to protect pressure vessels and systems. This paper developed a three-dimensional computational fluid dynamics (CFD) model in combination with a dynamics equation to study the fluid characteristics and dynamic behavior of a spring-loaded PSV. The CFD model, which includes unsteady analysis and a moving mesh technique, was developed to predict the flow field through the valve and calculate the flow force acting on the disk versus time. To overcome the limitation that the moving mesh technique in the commercial software program ANSYS CFX (Version 11.0, ANSYS, Inc., USA) cannot handle complex configurations in most applications, some novel techniques of mesh generation and modeling were used to ensure that the valve disk can move upward and downward successfully without negative mesh error. Subsequently, several constant inlet pressure loads were applied to the developed model. Response parameters, including the displacement of the disk, mass flow through the valve, and fluid force applied on the disk, were obtained and compared with the study of the behavior of the PSV under different overpressure conditions. In addition, the modeling approach could be useful for valve designers attempting to optimize spring-loaded PSVs. [DOI: 10.1115/1.4001428]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.paerosci.2010.03.001 Byline: H. Xia (a), P.G. Tucker (a), W.N. Dawes (b) Abstract: In the past two decades, the level set concept has been extensively explored. The superiority of the differential level set to other more ad hoc methods as a formal framework for directly/indirectly solving 'front-propagation' natured problems is now fully established. Nowadays, in many areas of aerospace related computational fluid dynamics, applications of level set methods can be found. This paper gives a brief review of these applications and how level sets can be useful in tackling challenging computational aerospace problems. The use of level sets in premixed turbulent combustion, aero-acoustics, geometry definition/morphing, meshing and turbulence modeling is explored in detail and other applications discussed. Author Affiliation: (a) Whittle Lab, Department of Engineering, University of Cambridge, 1 JJ Thomson Avenue, Cambridge CB3 0DY, UK (b) CFD Lab, Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK

A major concern in drilling operations is the proper determination of frictional pressure loss in order to select a mud pump and avoid any serious problems. In this study, a mechanistic model is proposed for predicting the frictional pressure losses of light drilling fluid, which can be used for concentric annuli. The experimental data that were available in the literature and conducted at the Middle East Technical University-Petroleum Engineering (METU-PETE) flow loop as well as computational fluid dynamics (CFD) software are used to verify the results from the proposed mechanistic model. The results showed that the proposed model can estimate frictional pressure losses within a [+ or -] 10% error interval when compared with the experimental data. Additionally, the effect of the pipe eccentricity on frictional pressure loss and tangential velocity using CFD for laminar and turbulent flow is also examined. It has been observed that pipe eccentricity drastically increases the tangential velocity inside the annulus; especially, the flow regime is turbulent and frictional pressure loss decreases as the pipe eccentricity increases. [DOI: 10.1115/1.4002243] Keywords: light drilling fluid, frictional pressure loss, concentric, eccentric, CFD, annulus, finite difference approximation

Detached-eddy simulations for the M219 experimental cavity geometry and the 1303 uninhabited combat air vehicle cavity geometry are presented. First, results from three computations are presented with the aim of studying the effect of imposing synthetic velocity fluctuations at the inflow boundary. Both methods employed (synthetic-eddy method and fluctuations from a precursor large-eddy simulation) increased the high-frequency content in the boundary layer upstream of the cavity. Averaged profiles showed little change in the streamwise velocity; however, the profiles of normal velocity were noticeably different. The influence of the upstream boundary layer on the cavity flowfield means that the full aircraft geometry needed to be modeled. Consequently, advanced multiblock topologies had to be used to properly represent the planform of the uninhabited combat air vehicle and all the details of the cavity, including doors and hinges, while sliding meshes were needed to insert the store into the uninhabited combat air vehicle configuration. Results with an empty cavity were encouraging for such complex configurations. Visualizations using the Q criteria revealed the added turbulent content due to the door leading edges and the door hinges. The addition of a store in between the doors had little effect close to the front wall. However, averaged flowfields showed that the proximity of the shear layer to the apex of the store deflected it downward into the cavity and restricted its growth. Outside the cavity, shedding was observed from the sting and force balance. DOI: 10.2514/1.C000218

Contrary to a midtropospheric warming trend detected from Microwave Sounding Unit (MSU) measurements, High-Resolution Infrared Radiation Sounder (HIRS) temperature (15 [micro]m) channels, sensitive to the thermal emission from the troposphere, produce distinct cooling trends for the period 1980-99. This apparent discrepancy in the tropospheric temperature trend is investigated through radiative transfer simulations using Geophysical Fluid Dynamics Laboratory climate model output and the profiles of the standard model atmospheres. Radiative simulations with time-invariant carbon dioxide concentration throughout the entire analysis period produce trends that are qualitatively similar to that obtained from the MSU observations, implying that the observed cooling trends of the HIRS temperature channels are attributable to increased carbon dioxide concentration over the 20-yr period. Additional simulations with the observed time-varying concentration of carbon dioxide confirm this basic result. Whereas temperature fluctuations dominate variability on monthly to interannual time scales, carbon dioxide changes dominate the decadal trends in both the observations and model simulations. Further simulations examined the sensitivity of the brightness temperature change with respect to the changes in tropospheric and stratospheric temperature. These calculations indicate that the influences of stratospheric temperature on the measured radiances are greater for the HIRS temperature channels relative to the MSU midtropospheric channel. These results highlight the contributions of time-varying carbon dioxide concentrations and stratospheric temperature to the HIRS 15-[micro]m (temperature channel) radiance record and underscore the importance of accurately accounting for these changes when using HIRS measurements for long-term monitoring. DOI: 10.1175/2010JAMC2486.1

This work extends and improves a one-dimensional shallow flow model to two-dimensional (2D) for real-world flood simulations. The model solves a prebalanced formulation of the fully 2D shallow water equations, including friction source terms using a finite volume Godunov-type numerical scheme. A reconstruction method ensuring nonnegative depth is used along with a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored for calculation of interface fluxes. A local bed modification method is proposed to maintain the well-balanced property of the algorithm for simulations involving wetting and drying. Second-order accurate scheme is achieved by using the slope limited linear reconstruction together with a Runge-Kutta time integration method. The model is applicable to calculate different types of flood wave ranging from slow-varying inundations to extreme and violent floods, propagating over complex domains including natural terrains and dense urban areas. After validating against an analytical case of flow sloshing in a domain with a parabolic bed profile, the model is applied to simulate an inundation event in a 36 [km.sup.2] floodplain in Thamesmead near London. The numerical predictions are compared with analytical solutions and alternative numerical results. DOI: 10.1061/(ASCE)HY.1943-7900.0000219 CE Database subject headings: Floods; Simulation; Shallow water; Friction; Topography; Hydraulic models. Author keywords: Flood simulation; Shallow water equations; Well-balanced scheme; Riemann solver; Friction terms; Complex topography.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.06.010 Byline: A. Hasan (a), S.J. McCormack (b), M.J. Huang (c), B. Norton (a) Keywords: Phase change materials (PCM); Building integrated photovoltaics (BIPV); Thermal regulation enhancement Abbreviations: PCM, phase change material; PV, photovoltaics; BIPV, building integrated photovoltaics; CFD, computational fluid dynamics; PV/T, photovoltaic thermal; DSC, differential scanning calorimetry; RT20, commercial paraffin based phase change material; SP22, commercial blend of salt hydrate and paraffin phase change material; CL, eutectic mixture of capric lauric acid; CP, eutectic mixture of capric-palmitic acid; CaCl.sub.2, calcium chloride hexa hydrate Abstract: Regulating the temperature of building integrated photovoltaics (BIPV) using phase change materials (PCMs) reduces the loss of temperature dependent photovoltaic (PV) efficiency. Five PCMs were selected for evaluation all with melting temperatures [approximately equal to]25[+ or -]4[degrees]C and heat of fusion between 140 and 213kJ/kg. Experiments were conducted at three insolation intensities to evaluate the performance of each PCM in four different PV/PCM systems. The effect on thermal regulation of PV was determined by changing the (i) mass of PCM and (ii) thermal conductivities of the PCM and PV/PCM system. A maximum temperature reduction of 18[degrees]C was achieved for 30min while 10[degrees]C temperature reduction was maintained for 5h at -1000W/m.sup.2 insolation. Author Affiliation: (a) Dublin Energy Lab., Focas Institute, School of Physics, Dublin Institute of Technology, Kevin St., Dublin 8, Ireland (b) Department of Civil, Structure and Environmental Engineering, Trinity College Dublin, Dublin 1, Ireland (c) Centre for Sustainable Technologies, University of Ulster, Newtownabbey, N. Ireland, BT370QB, UK Article History: Received 22 September 2009; Revised 20 May 2010; Accepted 21 June 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Harvey Bryan

Nonrandom seed release is an important determinant of how far seeds disperse, but the mechanisms that promote wind-related seed release under varying atmospheric conditions are poorly understood. We explored the use of particle image velocimetry (PIV) to gain a better mechanistic understanding of seed release by visualizing the flow velocities and vorticity in a two-dimensional slice of air around inflorescences. Pilot data taken in a wind tunnel show gradients in air velocity at the top of Carduus nutans capitula that may contribute to lift generation. Additionally, von Karman vortex streets (vortices of opposite spin that are shed from the wake of an object) were observed shedding from capitula, which cause lateral forces on capitula and increase turbulence downwind at other locations. Avenues for further research include using PIV to examine the mechanisms of seed release and dispersal in wind tunnels and in the field. We found PIV to be a promising method to further explore the mechanisms behind seed release in wind dispersed plants, and a technique rich with opportunities for collaborations between plant dispersal ecologists and fluid dynamics specialists. Key words: Carduus nutans; lift; particle image velocimetry; seed release; turbulence; von Karman vortex streets; wind dispersal.

The problem of optimal control in hydrodynamics has attracted the attention of many authors (see, e.g., (24), (44), (48) and the bibliography therein). Most of these works consider fluids described [...]

In the present, a steady laminar of two dimensional and incompressible fluid flow induces from wall injection in a circular chamber has been studied experimentally and numerically. The water is injected from injection system into the chamber through the wall jets. The centerline static pressure variation with the distance along the chamber length is measured and calculated at different Reynolds numbers and inlet flow angles. The average heat transfer with Reynolds number at different values of the inlet flow angle is obtained. The velocity vectors are presented and Reynolds number is varied between 433 and 910 with inlet flow angle of 0 deg, 15 deg, 30 deg, 45 deg, and 60 deg. The results indicate that the pressure recovery coefficient decreases as both Reynolds number and flow angle increase. The average heat transfer coefficient increases with increasing both Reynolds number and flow angle. The results showed that two recirculation zones occur in the sides of centerline of the chamber behind the step. The size of these recirculation zones decreases by increasing the inlet flow angle. At high value of the inlet flow angle, other recirculation zone occurs on the wall chamber. [DOI: 10.1115/1.4001394] Keywords: annular injection, laminar flow, two dimensional, pressure coefficient, heat transfer

In this work, the effect of the second-order term to the velocity-slip/temperature-jump boundary conditions on the solution of four cases in which the driving force is fluctuating harmonically was studied. The study aims to establish criteria that secure the use of the first order velocity-slip/temperature-jump model boundary conditions instead of the second-order ones. The four cases studied were the transient Couette flow, the pulsating Poiseuille flow, Stoke's second problem, and the transient natural convection flow. It was found that at any given Kn number, increasing the driving force frequency, increases the difference between the first and second-order models. Assuming that a difference between the two models of over 5% is significant enough to justify the use of the more complex second-order model the critical frequencies for the four different cases were found. For the cases for which the flow is induced by the fluctuating wall as in cases 1 and 3, we found that critical frequency at Kn=0.1 to be [omega]=8. For the cases of flow driven by a fluctuating pressure gradient as in case 2, this frequency was found to be [omega]=1, at the same Kn number. In case 4, for the temperature-jump model the critical frequency was found to be [omega]=7 and for the velocity-slip model the critical frequency at the same Kn number was found to be [omega]=1.35. [DOI: 10.1115/1.4001970]

Accurate drag estimation is critical in making computational design studies. Drag may be estimated thousands of times during a multidisciplinary design optimization, and computational fluid dynamics is not yet possible in these studies. The current model has been developed as part of an air-vehicle conceptual-design multidisciplinary design optimization framework. Its use for subsonic and transonic aircraft configurations is presented and validated. We present our parametric geometry definition, followed by the drag model description. The drag model includes induced, friction, wave, and interference drag. The model is compared with subsonic and transonic isolated wings, and a wing/body configuration used previously in drag prediction workshops. The agreement between the predictions of the drag model and test data is good, but lessens at high lift coefficients and high transonic Mach numbers. In some cases the accuracy of this drag estimation method exceeds much more elaborate analyses. DOI: 10.2514/1.47557

Flight testing for aeroservoelastic clearance is an expensive and time consuming process. Large degree-of-freedom high-fidelity nonlinear aircraft models using computational fluid dynamics coupled with finite element models can be used for accurately predicting aeroelastic phenomena in all flight regimes including subsonic, supersonic, and transonic. With the incorporation of an active feedback control system, these high-fidelity models can be used to reduce the flight-test time needed for aeroservoelastic clearance. Accurate computational fluid dynamics/finite element models are computationally complex, rendering their runtime ill suited for adequate flight control system design. In this work, a complex, large-degree-of-freedom, transonic, inviscid computational fluid dynamics/finite element model of a fighter aircraft is fitted with a flight control system for aeroelastic oscillation reduction. A linear reduced-order model of the complete aeroelastic aircraft dynamic system is produced directly from the high-order nonlinear computational fluid dynamics/finite element model. This rapid runtime reduced-order model is used for the design of the flight control system, which includes models of the actuators and common nonlinearities in the form of rate limiting and saturation. The oscillation reduction controller is successfully demonstrated via a simulated flight test using the high-fidelity nonlinear computational fluid dynamics/finite element/flight control system model. DOI: 10.2514/1.47119

Flutter prediction as currently practiced is almost always deterministic in nature, based on a single structural model that is assumed to represent a fleet of aircraft. However, it is also recognized that there can be significant structural variability, even for different flights of the same aircraft. The safety factor used for flutter clearance is in part meant to account for this variability. Simulation tools can, however, represent the consequences of structural variability in the flutter predictions, providing extra information that could be useful in planning physical tests and assessing risk. The main problem arising for this type of calculation when using high-fidelity tools based on computational fluid dynamics is the computational cost. The current paper uses an eigenvalue-based stability method together with Euler-level aerodynamics and different methods for propagating structural variability to stability predictions. The propagation methods are Monte Carlo, perturbation, and interval analysis. The feasibility of this type of analysis is demonstrated. Results are presented for the Goland wing and a generic lighter configuration. DOI: 10.2514/1.46971

Predators often have large effects on community structure, but these effects can be minimized in habitats subjected to intense physical stress. For example, predators exert large effects on rocky intertidal communities on wave-protected shores but are usually absent from wave-swept shores where hydrodynamic forces prevent them from foraging effectively. The physical environment also can affect predation levels when stressors are not severe enough to be physically risky. In these situations, environmental conditions may constrain a predator's ability to locate prey and alleviate predation pressure. Yet, stress models of community structure have rarely considered the implications of such sensory or behavioral stressors, particularly when the sensory abilities of both predators and prey are affected by the same types of environmental conditions. Ecologists may classify certain environmental conditions as refuges if they impede predator foraging, but these conditions may not actually decrease predation levels if they simultaneously increase prey vulnerability to consumers. Using blue crabs (Callinectes sapidus) and hard clams (Mercenaria mercenaria) as a model system, we investigated the relationship between predation intensity and environmental stress in the form of hydrodynamics (i.e., flow velocity and turbulence). Blue crabs and hard clams are less responsive to each other in faster, more turbulent flows, but studies exploring how flow modulates the outcomes of crab--clam interactions in the field are lacking. We manipulated turbulence within field sites and compared predation levels within and between sites that differed in flow velocity and turbulence. Our results suggest that blue crabs are most effective foragers in flows with intermediate velocities and turbulence levels. Although these conditions are not ideal for blue crabs, lab studies indicate that they also compromise the ability of clams to detect and react to approaching crabs and, thereby, increase clam vulnerability to predators. Our results suggest that environmental stresses on perception (sensory stressors) may not cause a steady decay in predation rates when they simultaneously affect the behaviors of both predators and prey. Moreover, the relative contribution of lethal vs. nonlethal predator effects in communities also may be influenced by environmental forces that enhance the predator-avoidance abilities of prey or the foraging efficiency of predators. Key words: blue crab; Callinectes sapidus; chemosensation; clam; flow; fluid dynamics; Mercenaria mercenaria; predator--prey interaction; sensory ecology; turbulence; Wassaw Sound, Georgia, USA.

For dynamic production aeroelastic analysis in the transonic speed range, a computational fluid dynamics method based on the small disturbance Navier--Stokes equations can serve as a reasonable alternative to one realizing the Reynolds-averaged Navier--Stokes equations' time-domain solution. Its dynamically linear approach promises a significantly decreased computation cost in the prediction of unsteady aerodynamic loading while retaining the latter's fidelity to a high degree. In this regard, research conducted at the Technical University of Munich has resulted in the computational fluid dynamics method FLM-SD.NS. Further substantiating its application readiness, harmonic pitching oscillations of the NASA clipped delta wing are investigated. Test cases are characterized by shocks of varying strengths and ranges of motion, as well as leading-edge vortex formation. Overall, results are in good agreement with dynamically fully nonlinear solutions provided by the comparative Reynolds-averaged Navier--Stokes solver FLM-NS, as well as available experimental data. Reductions in computation time, up to an order of magnitude, in relation to FLM-NS are observed. Limitations of the small disturbance approach, however, become apparent for the leading-edge vortex case, in which higher-order harmonics are far less negligible in the flow's response to the excitation. DOI: 10.2514/1.45233

A computational study, a wind-tunnel analysis, and a flight test on the T-38 Talon demonstrated that approach-to-stall characteristics may be improved by the addition of a wing fence. Fences were placed at the location of a preexisting seam, at [+ or -]0.825 semispan, and were compared with the T-38 without fences. Reynolds-averaged Navier--Stokes simulations were conducted using the computational fluid dynamics air vehicles unstructured solver to examine the flow around the T-38 at typical full-flap landing conditions (Re = 4.66 x [10.sup.6] per unit length). Solutions were computed over a range of angles of attack from 2 to 15 deg. The fence was found to increase [C.sub.L max] by 7% and delay the attainment of [C.sub.L max] from a 12 to a 13 deg angle of attack. This effect was achieved through the formation of a discrete streamwise vortex outboard of the fence, which prevented flow separation in the tip region, which (in turn) delayed flow separation over the remainder of the wing, resulting in the higher computed lift. Wind-tunnel results, by and large, were based on aircraft instrumentation and flow visualization for Mach numbers up to 0.65 ([Re.sub.mac] ~ [10.sup.7]). The flight-test data showed an increase in [C.sub.L] of approximately 2% in the angle-of-attack range of 12-14.5 deg when the wing fence was in place. Onboard accelerometer data suggest the fence reduced the roll-off tendency and the wing-rock amplitude during approaches to stall. Flow visualization on the aircraft wing in both the wind-tunnel study and the flight test suggested that the fence reduced spanwise and separated flow outboard the fence, which agreed with the computational fluid dynamics results. DOI: 10.2514/1.46122

This paper studies a computational fluid dynamics validation study of wake-capturing capability for unsteady flow characteristics. The computational fluid dynamics code used in this study is based on the Cartesian grid system with octree mesh refinement and uses a weighted essentially nonoscillatory numerical scheme to achieve higher-order accuracy to preserve unsteady flow characteristics. Flow properties in the flat-plate wake flowfield, such as mean velocity, root mean square of perturbation velocity, and frequency wise power spectrum of flow velocity, were chosen to validate the computational fluid dynamics code. The comparison between computational fluid dynamics results and experimental data showed good agreement for mean velocity and low-frequency fluctuations. DOI: 10.2514/1.33502

This paper discusses a study on the local flows in the vicinity of aircraft landing gear. Local flows for various aircraft types at various operation conditions are extracted from a computational fluid dynamics database and analyzed to reveal parametric trends of the local flows. It is shown that, for wing-mounted gear, the circulation around the high-lift wing induces a flow under the wing in the opposite direction to the freestream flow and, hence, makes the local flow velocity lower than the freestream velocity. For fuselage-mounted gear, the trends are opposite; the local flow velocity for nose gear is usually slightly higher than the freestream. For all gear, it is shown that the local flow velocity is a decreasing function of the aircraft angle of attack. Based on these features, a simple reduced-order model is developed, which correlates the local flow velocity to the freestream velocity, the aircraft angle of attack, the maximum aircraft takeoff weight, and the distance from the aircraft. All these parameters are readily available in practical applications, rendering the simple model suitable for landing gear noise prediction. Discussions are given on the effects of the local flow features on landing gear noise analysis and prediction with practical examples. DOI: 10.2514/1.43615

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.12.011 Byline: S.V. Karmare (a)(c), A.N. Tikekar (b)(c) Keywords: Roughness; Metal rib grit; Solar air heater; Heat transfer Abstract: This paper presents the study of fluid flow and heat transfer in a solar air heater by using Computational Fluid Dynamics (CFD) which reduces time and cost. Lower side of collector plate is made rough with metal ribs of circular, square and triangular cross-section, having 60[degrees] inclinations to the air flow. The grit rib elements are fixed on the surface in staggered manner to form defined grid. The system and operating parameters studied are: e/D.sub.h =0.044, p/e =17.5 and l/s =1.72, for the Reynolds number range 3600-17,000. To validate CFD results, experimental investigations were carried out in the laboratory. It is found that experimental and CFD analysis results give the good agreement. The optimization of rib geometry and its angle of attack is also done. The square cross-section ribs with 58[degrees] angle of attack give maximum heat transfer. The percentage enhancement in the heat transfer for square plate over smooth surface is 30%. Author Affiliation: (a) Department of Mechanical Engineering, Government College Engineering, Karad 415 124, Maharashtra, India (b) Department of Mechanical Engineering, Walchand College of Engineering, Sangli, India (c) Shivaji University, Kolhapur, Maharashtra, India Article History: Received 24 September 2009; Revised 11 December 2009; Accepted 15 December 2009 Article Note: (miscellaneous) Communicated by: Associate Editor G.N. Tiwari

This paper experimentally investigates the feasibility of an adaptive passive control system, which consists of a magnetorheological (MR) fluid damper and an electromagnetic induction (EMI) part, for suppressing vibration of building structures subjected to ground accelerations. In the adaptive passive control system, the EMI part composed of a permanent magnet and a coil convert the kinetic energy of the relative motion between a building and a damper into the electric energy, which is used for a change in damping characteristics of the MR fluid damper. Since the EMI part can be used as a controller, which determines the command voltage input according to structural responses as well as a power source, the adaptive passive system can be much more compact, convenient, and economic than a conventional active/semiactive system that needs a power supply, a controller, and sensors. To experimentally verify the feasibility of the adaptive passive control system, a shaking table test of a small-scale building model employing the MR fluid damper with the EMI part is conducted. The performance of the adaptive passive control system is compared with that of passively operated MR fluid damper-based semiactive control systems. DOI: 10.1061/(ASCE)0733-9399(2010)136:2(254) CE Database subject headings: Passive control; Control systems; Damping; Seismic effects; Shake table tests. Author keywords: Adaptive passive control; MR fluid damper; Electromagnetic induction; Seismic protection; Shaking table test.

A comparison of velocity(-derived) quantities is made in the slipstream of a turboprop-equipped transport aircraft between phase-locked experimental Particle Image Velocimetry data and unsteady Reynolds averaged Navier-Stokes calculations. Velocity results indicate a high level of agreement between the numerical and experimental results. In addition to velocity vector data, other derived quantities, such as vorticity, allow a verification and validation of the modeling in Computational Fluid Dynamics. Although a good agreement is achieved, future needs for the comparison and validation of computational (Computational Fluid Dynamics) and experimental (Particle Image Velocimetry) data are highlighted. DOI: 10.2514/1.45961

Three-dimensional fully viscous turbulent aero-icing flow simulation remains too computationally intensive when broad parametric studies are needed, such as during a certification process. In addition, the introduction of realistic icing effects for training pilots in simulators clearly lags behind in terms of taking advantage of computational fluid dynamics. To make such simulations more practical, this work presents a reduced-order modeling, based on the proper orthogonal decomposition method, that predicts a wide swath of approximate flowfields and ice shapes based on a limited number of 'snapshots' obtained from high-fidelity computations. Modes are extracted from these snapshots and used to reconstruct the computational fluid dynamics field, and/or the aerodynamic coefficients, and/ or the ice shapes for other conditions within the range. This reduces calculation times by two to three orders of magnitude from the full three-dimensional ones, enabling a more complete map of the performance of an iced aircraft over a wide range of flight and weather conditions to be used in its certification and pilot training. DOI: 10.2514/1.44077

Flush air data sensing systems have been widely applied to large (manned) aircraft, where pressure orifices are typically located at the nosetip. This paper investigates the feasibility of a flush air data sensing system designed to estimate the air data states of a small unmanned air vehicle flown at speeds as low as Mach 0.07. Furthermore, due to the presence of a nose propeller, the pressure orifices are located at the wing leading edge. The motivation behind this project is the fact that traditional air data booms are physically impractical for small unmanned air vehicles. Overall, an 80 and 97% reduction in instrumentation weight and cost, respectively, were achieved. Both parametric and multilayer pereeptron neural network models have been previously applied in the literature to model the aerodynamic relationship between aircraft surface pressure and the air data states. In this paper, an extended minimum resource allocating network radial basis function neural network is used as the flush air data sensing system model, due to its good generalization capabilities and compact structure. Computational fluid dynamic simulations are implemented to identify the ideal pressure port locations, and wind-tunnel tests are carried out to train and test the extended minimum resource allocating network radial basis function neural network. DOI: 10.2514/1.44157