Edge Extension Research Articles

From Water Tunnel to Poststall Flight Simulation: The F/A-18 Investigation

Introduction T HE prediction of poststall maneuvers and departure characteristics of high-performance aircraft continues to be challenging,1;2 due, in particular, to the highly three-dimensional nature of the motions and aerodynamic responses. A case in point is the F/A-18 aircraft (Fig. 1), which has experienced departures from controlled  ight, typically involving large sideslip excursions with attendant high body-axes rate variations leading to high angles of attack ® (Ref. 4). The lateral–directional departure susceptibility of the F/A-18 provided part of the motivation within the NASA High-Alpha Technology Program for the improvement of high-alpha predictionsbased on ground testing. The gyrations and responsesexperiencedon departureare intrinsicallynonplanar, that is, involvingarbitraryrotationsnot alignedwith theprincipalaxesof the aircraft.3 When the  ight mechanical deŽ ciencies of an F/A-18 simulation were identiŽ ed, a Canadian programwas undertaken to enhance simulator Ž delity.6 The areas in which the airframe model could be improved included the poststall aerodynamicdatabase, the multivariabletable lookuparchitecture,and the aerodynamicmodel. The present paper focuses on the improvements to the database. The shortcomings of the poststall aerodynamic database were attributed largely to facility interference and scaling effects not accounted for and gaps in the parameter space covered. The original rotary database for F/A-18 was generated in the NASA Langley Research Center Spin Tunnel.11 The F/A-18 poststall maneuvering aerodynamics is dominated by forebody/leading edge extension (LEX) vortex interactions at moderately high angles of attack (30 55 deg). In the light of the sensitivity of the vortex interactions to sideslip angle (Ref. 12), it was deemed necessary to generate a more detailed rotary database to deŽ ne the associated relationshipsover a large sideslip range. When the advantages of the water-tunnel approachwere considered, it seemed appropriate to use this ground-testmethodology to generate supplementary data. The orbital platform rotary balance system (OPLEC) at the Institute for Aerospace Research (IAR) water tunnel, a diagnostic tool for studying support interference7;8 and unsteady wall interference, was subsequently used in highresolution tests as well as diagnostic experiments15i18 on the baseline F/A-18. A thorough understanding of scale effects on vortex

연장된 앞전을 갖는 편요된 삼각날개의 높은 받음각에서의 와류 특성에 관한 연구

높은 받음각 상태에 있는 연장된 앞전을 갖는 편요된 삼각날개 주위의 와류 유동 특성에 대하여 날개 윗면에서의 압력 측정을 통하여 연구하였다. 본 연구에서는 와류 유동의 물리적 현상, 특히 높은 받음각 상태에서 받음각과 옆미끄럼각이 날개 형상 주위의 공력 특성에 미치는 영향에 중점을 두었다. 실험 데이터로부터 LEX 와류가 날개와류에 유익한 효과를 부여함을 명확하게 알 수 있었다. 이는, 작은 옆미끄럼각 상태에서는 비교적 높은 받음각에 이르기까지 와류의 붕괴 없이 날개와류를 안정화시킴을 알 수 있다. 특정 범위의 받음각과 옆미끄럼각 상태에서는 롤링 모멘트가 역전되는 흥미로운 유동 현상을 관찰할 수 있었다. An experimental study of the vortical flow characteristics around a yawed delta wing with the leading edge extension at high incidence angle is undertaken by upper surface pressure measurements. A special emphasis has been put on analyzing the basic physics of vortical flows, concerning the effects of incidence and sideslip angle on the aerodynamic characteristics of the wing, especially under high angle of attack. The experimental data has been dearly demonstrated the beneficial effect of the LEX vortex on the wing vortex. It leads to an essential stabilization of the wing vortex against its breakdown until at much higher incidence angle under small sideslip. An interesting flow feature is occurrence of the rolling moment reversal at a certain range of angle of attack and sideslip angle.

옆미끄럼을 갖는 LEX/삼각 날개 형상에 대한 높은 받음각 와유동의 가시화 연구

An off-surface flow visualization experiments have been performed to investigate the flow field over a delta wing with the leading edge extension(LEX). The model is a flat wing with sweepback angle. The free stream velocity is 6.2 m/s, which corresponds to Reynolds number of based on the wing root chord. The angle of attack and sideslip angle range from and , respectively. The visualization technique of using the micro water-droplet and the laser beam sheet enabled to observe the vortical flow structures, which can not be obtained by 5-hole probe measurements. With sideslip angle, the interaction and breakdown of the LEX and wing vortices was promoted in the windward side, whereas, it was suppressed in the leeward side.

논문 : 옆미끄럼이 있는 삼각 날개 / LEX 형상의 와류와 공력 특성

The vortex flow and aerodynamic load characteristics of a sweep delta wing with the leading edge extension in sideslip condition is investigated experimentally. The freestream velocity is 40 m/sec, which corresponds to a Reynolds number per meter of 1.76X based on the wing root chord. The angles of attack range from to 28{^{\circ}}, and the sideslip angles treated are 0{^{\circ}}, -10{^{\circ}}, 20{^{\circ}}. The LEX vortex of the leeward side. The LEX and wing vortics coalesce to to become a concentrated strong vortex or to break down at down at downstream position. Due to the interation of the LEX and wing vortices, a high suction pressure is maintained on the windward wing surface, and a low suction pressure is formed on the leeward wing surface.ﾖ⨀

논문 : LEX 가 델타형 날개의 표면압력분포에 미치는 영향

LEX를 가진 델타형 날개 모델을 사용한 풍동실험을 통하여 LEX가 델타형 날개 윗면의 표면압력분포에 미치는 영향에 대한 연구를 수행하였다. 풍동실험의 유속은 40m/sec, 전압과 전온도는 각각 101Pa, 278K이었으며, 단위길이당 레이놀즈 수는 <TEX>$1.76{\times}10^6$</TEX>이었다. LEX는 날개의 표면압력분포를 매우 많이 변화시키었다. LEX가 없는 경우에 비하여 표면압력의 피크치가 시위 앞부분에서는 감소하였으나 뒷부분으로 갈수록 그리고 받음각이 증가할수록 피크치도 증가하였다. 스팬방향 압력구배도 시위 앞부분에서는 완만하였으나 뒤로 갈수록 증가하였다. 또한 LEX가 있는 경우에는 모든 위치에서 받음각의 증가에 따라 표면압력 피크치도 거의 선형적으로 증가하였다. An experimental study was conducted to investigate the effects of leading edge extension(LEX) on the surface prssure distribution over a delta wing in a subsonic wind tunnel. Freestream velocity was 40m/sec and Reynolds number per meter was 1.7x<TEX>$10^6$</TEX> with total pressure of 101Pa and total temperature of 278K. LEX changed the surface pressure distribution on the wing dramatically. Comparing with the results without LEX, the peak of pressure distribution decreased on the front chordwise location but it turned to increase on the rear chordwise location with increase of the angle of attaci. The spanwise gradient of the pressure distribution also increased in the rear chordwise location. Without LEX, the peak of pressure distribution increased and decreased irregularly with increase of the angle of attack at each chordwise location, but LEX made it increased almost linearly with increase of the angle of attack at all of the chordwise locations.

Polarized basolateral cell motility underlies invagination and convergent extension of the ascidian notochord

We use 3D time-lapse analysis of living embryos and laser scanning confocal reconstructions of fixed, staged, whole-mounted embryos to describe three-dimensional patterns of cell motility, cell shape change, cell rearrangement and tissue deformation that accompany formation of the ascidian notochord. We show that notochord formation involves two simultaneous processes occurring within an initially monolayer epithelial plate: The first is invagination of the notochord plate about the axial midline to form a solid cylindrical rod. The second is mediolaterally directed intercalation of cells within the plane of the epithelial plate, and then later about the circumference of the cylindrical rod, that accompanies its extension along the anterior/posterior (AP) axis. We provide evidence that these shape changes and rearrangements are driven by active extension of interior basolateral notochord cell edges directly across the faces of their adjacent notochord neighbors in a manner analogous to leading edge extension of lamellapodia by motile cells in culture. We show further that local edge extension is polarized with respect to both the AP axis of the embryo and the apicobasal axis of the notochord plate. Our observations suggest a novel view of how active basolateral motility could drive both invagination and convergent extension of a monolayer epithelium. They further reveal deep similarities between modes of notochord morphogenesis exhibited by ascidians and other chordate embryos, suggesting that cellular mechanisms of ascidian notochord formation may operate across the chordate phylum.

Neuronal migration

Like other motile cells, neurons migrate in three schematic steps, namely leading edge extension, nuclear translocation or nucleokinesis, and retraction of the trailing process. In addition, neurons are ordered into architectonic patterns at the end of migration. Leading edge extension can proceed at the extremity of the axon, by growth cone formation, or from the dendrites, by formation of dendritic tips. Among both categories of leading edges, variation seems to be related to the rate of extension of the leading process. Leading edge extension is directed by microfilament polymerization following integration of extracellular cues and is regulated by Rho-type small GTPases. In humans, mutations of filamin, an actin-associated protein, result in heterotopic neurons, probably due to defective leading edge extension. The second event in neuron migration is nucleokinesis, a process which is critically dependent on the microtubule network, as shown in many cell types, from slime molds to vertebrates. In humans, mutations in the PAFAH1B1 gene (more commonly called LIS1) or in the doublecortin (DCX) gene result in type 1 lissencephalies that are most probably due to defective nucleokinesis. Both the Lis1 and doublecortin proteins interact with microtubules, and two Lis1-interacting proteins, Nudel and mammalian NudE, are components of the dynein motor complex and of microtubule organizing centers. In mice, mutations of Cdk5 or of its activators p35 and p39 result in a migration phenotype compatible with defective nucleokinesis, although an effect on leading edge formation is also likely. The formation of architectonic patterns at the end of migration requires the integrity of the Reelin signalling pathway. Other known components of the pathway include members of the lipoprotein receptor family, the intracellular adaptor Dab1, and possibly integrin alpha 3 beta 1. Defective Reelin leads to poor lamination and, in humans, to a lissencephaly phenotype different from type 1 lissencephaly. Although the action of Reelin is unknown, it may trigger some recognition-adhesion among target neurons. Finally, pattern formation requires the integrity of the external limiting membrane, defects of which lead to overmigration of neurons in meninges and to human type 2 lissencephaly.

Improved Method for the Prediction of Resonance Frequency of Triangular Microstrip Antennas

An improved method is presented to predict the resonance frequency of the equilateral triangular microstrip antenna, which takes into account the frequency dependency of the effective dielectric constant and edge extension. The simulated results are in very good agreement with the reported and measured results.

Periodical Cicada (Homoptera: Cicadidae) Life-Cycle Variations, the Historical Emergence Record, and the Geographic Stability of Brood Distributions

The complex biogeography of the 13- and 17-yr periodical cicadas offers important opportunities for testing hypotheses of Magicicada evolution and ecology. However, misinterpretation of stragglers as on-schedule emergences, combined with systematic biases in search effort and the use of cross-generational brood maps, likely results in erroneous edge extension of adjacent broods and the appearance of sympatric shadow broods in published maps. Substantial recent changes in brood distributions have been inferred from the Magicicada historical record, the most significant being the decline and extinction of 17-yr brood X in the midwestern United States, the widespread expansion and contraction of 17-yr brood VI and 13-yr brood XXIII, and the displacement of brood XIII 17-yr cicadas in Illinois by 13-yr brood XIX in Illinois. Reanalysis of the historical data with an awareness of straggler-induced error suggests instead that brood distributions in these cases have remained stable.

Analytical method for a circularly polarised rectangular microstrip antenna

The paper proposes a formulation method for the wall admittance of an arbitrarily shaped microstrip antenna using spectral domain analysis. In the paper, the wall admittance of the circularly polarised rectangular microstrip antenna is calculated. The circularly polarised rectangular microstrip antenna is analysed using the cavity model. The electromagnetic fields within the antenna cavity are expanded in terms of the eigenfunctions in the cavity with sides extended by the edge extension length. The edge extension length is determined so that the eigenfunctions satisfy the Helmholtz equation at all frequencies. Their expansion coefficients are determined by the impedance boundary condition at the aperture. The calculated input impedance and axial ratio of the antenna agree fairly well with the measured data.

Determination of the resonant frequency of microstrip antennas

A generalized method is proposed to determine the effective dielectric constant and edge extension for predicting the resonant frequency of various microstrip antennas (MSAs) by equating their area with that of the equivalent rectangular microstrip antenna (RMSA). The theoretical frequency obtained using the present method is in very good agreement with the reported/measured frequencies. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 114–117, 1999.

Xenopus nonmuscle myosin heavy chain isoforms have different subcellular localizations and enzymatic activities.

There are two isoforms of the vertebrate nonmuscle myosin heavy chain, MHC-A and MHC-B, that are encoded by two separate genes. We compared the enzymatic activities as well as the subcellular localizations of these isoforms in Xenopus cells. MHC-A and MHC-B were purified from cells by immunoprecipitation with isoform-specific peptide antibodies followed by elution with their cognate peptides. Using an in vitro motility assay, we found that the velocity of movement of actin filaments by MHC-A was 3.3-fold faster than that by MHC-B. Likewise, the Vmax of the actin-activated Mg(2+)-ATPase activity of MHC-A was 2.6-fold greater than that of MHC-B. Immunofluorescence microscopy demonstrated distinct localizations for MHC-A and MHC-B. In interphase cells, MHC-B was present in the cell cortex and diffusely arranged in the cytoplasm. In highly polarized, rapidly migrating interphase cells, the lamellipodium was dramatically enriched for MHC-B suggesting a possible involvement of MHC-B based contractions in leading edge extension and/or retraction. In contrast, MHC-A was absent from the cell periphery and was arranged in a fibrillar staining pattern in the cytoplasm. The two myosin heavy chain isoforms also had distinct localizations throughout mitosis. During prophase, the MHC-B redistributed to the nuclear membrane, and then resumed its interphase localization by metaphase. MHC-A, while diffuse within the cytoplasm at all stages of mitosis, also localized to the mitotic spindle in two different cultured cell lines as well as in Xenopus blastomeres. During telophase both isoforms colocalized to the contractile ring. The different subcellular localizations of MHC-A and MHC-B, together with the data demonstrating that these myosins have markedly different enzymatic activities, strongly suggests that they have different functions.

Installed F/A-18 inlet flow calculations at a high angle of attack

One of the goals of the high alpha technology program (HATP) is to accurately predict the inlet performance for aircraft operating at extreme attitudes (a = 60 deg, /8 = 10 deg). In this article, the numerical results for three cases are presented. The cases studied are full scale, 19.78% model scale at design mass flow, and model scale at a reduced mass flow. The effects of Reynolds number on the predicted flowfleld is demonstrated with the model and full scale calculations. The inlet mass flow is reduced 25% to investigate the effect mass flow rate has on the flow entering the inlet and on the inlet duct performance. All cases are at 30-deg angle of attack and 0-deg yaw. Surface static pressures along the forebody and under the leading edge extension (LEX) agreed well with the data for all three cases. The predicted inlet recoveries obtained for full scale and model scale Reynolds numbers were very similar. The predicted inlet recoveries were lower than data. This discrepancy may be partly due to poor inlet lip definition and grid resolution. The predicted inlet recovery for the reduced mass flow rate case was significantly higher than the design mass flow case. The reduction of inlet mass flow rate had a small effect on the external flowfleld. The choice of the turbulence model length scale has a significant impact on the position of the windward side LEX vortex.

Vortex flow control using fillets on a double-delta wing

This article presents results from a subsonic numerical investigation on the effects of geometry modifications at the junction of the leading edge extension (LEX) and wing of a flat-plate cropped double-delta wing at moderate to high angles of attack. The baseline planform of the double-delta wing configuration consisted of a strake with a 76-deg leading-edge sweep and a wing with a 40-deg leading-edge sweep with sharp, beveled leading edges. The geometry modifications included various fillet shapes with planform areas equal to 1% of the baseline wing reference area. A hyperbolic grid generation method was developed and used in conjunction with an existing interactive grid generation system to create high quality C-O type multiblock grids about the configurations studied. The Euler and Reynolds averaged Navier-Stokes (RANS) equations were solved numerically using two finite-volume production flow solvers. The baseline configuration numerical results correlated well with existing published experimental data. Grid refinement using the RANS revealed vortex sheet tearing on the wing. Fillets enhanced the lift by 14% at low angle of attack, and 18% at high angle of attack with a slight improvement in lift-to-drag ratio. The fillets may be good candidates for roll control devices.

A new edge extension expression for the resonant frequency of electrically thick rectangular microstrip antennas

A new fringing field extension expression is presented for the resonant frequency of electrically thick rectangular microstrip antennas. The theoretical resonant frequency results obtained by using this new fringing field extension expression are in very good agreement with the experimental results available in the literature.

A VLSI pyramid chip for multiresolution image analysis

Advanced techniques in image processing and computer vision increasingly require that image data be represented at multiple resolutions and at multiple sample rates. Application areas for such pyramid image representations include image compression, image enhancement, motion analysis, and object recognition. We have developed a VLSI chip, called PYR, to perform the standard filter and resampling operations required in pyramid and inverse pyramid transforms for these applications. The PYR chip processes image samples sequentially, in raster scan format, so is suited for pipeline architectures. The user can choose from a set of standard filters, through software control, to construct Gaussian, Laplacian, Subband, and related pyramid structures. A unique feature of the design is that it includes timing signals that are passed with the image data. These signals coordinate successive processing steps in a pipeline system as image sizes and sample rates change. The chip also includes circuits for edge extension and image addition, and it can be run in “spread tap” mode to provide twice the standard sample density. The PYR chip is implemented in standard cell technology. At a clock rate of 15 MHz, a single chip can simultaneously construct a Gaussian and a Laplacian pyramid from a 512 by 480 image in 22.7 msec (44 frame/second).

Experimental studies on the mechanism and control of secondary flow losses in turbine cascades

This paper summarizes the results of the authors’ 4 year experimental studies on the secondary flow losses in turbine cascades. Cascade wind tunnel experiments were carried out concerning the influence of aspect ratios, incidence, turning angles and outer endwall divergent angles in order to unveil the evolution mechanism of secondary flow losses in turbine cascades without end clearance. Some methods for controlling the secondary flows are investigated including the blade leaning, blade cambering, endwall convergence and leading edge extension at two ends of the blade.

Improved cavity model parameters for calculation of resonant frequency of rectangular microstrip antennas

Models for the resonant frequency proposed by other authors are shown to produce misleading results for frequencies greater than about 3 GHz. However, a cavity model with a novel empirically determined edge extension parameter provides calculated frequencies within 2% of measurements for antennas operating between 600MHz and 5 GHz.

Nondifferentiable reverse convex programs and facetial convexity cuts via a disjunctive characterization

Disjunctive Programs can often be transcribed as reverse convex constrained problems with nondifferentiable constraints and unbounded feasible regions. We consider this general class of nonconvex programs, called Reverse Convex Programs (RCP), and show that under quite general conditions, the closure of the convex hull of the feasible region is polyhedral. This development is then pursued from a more constructive standpoint, in that, for certain special reverse convex sets, we specify a finite linear disjunction whose closed convex hull coincides with that of the special reverse convex set. When interpreted in the context of convexity/intersection cuts, this provides the capability of generating any (negative edge extension) facet cut. Although this characterization is more clarifying than computationally oriented, our development shows that if certain bounds are available, then convexity/intersection cuts can be strengthened relatively inexpensively.

An attached flow design of a noninterfering leading-edge extension to a thick delta wing

The analytical procedure presented for leading edge extension (LEE) determination, in keeping with such design criteria as noninterference at the wing design point, is applied to thick delta wings. The LEE device thus defined is to be mounted on a wing along a dividing stream surface that is associated with an attached flow design lift coefficient greater than zero. The delta wing in question is of twisted and cambered type. It is demonstrated that span reductions for the candidate LEEs has the most detrimental effect on overall aerodynamic efficiency, irrespective of area or shape.