Dissertations / Theses: 'High angle of attack'

1

Atesoglu, Ozgur Mustafa. "High Angle Of Attack Maneuvering And Stabilization Control Of Aircraft." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608575/index.pdf.

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In this study, the implementation of modern control techniques, that can be used both for the stable recovery of the aircraft from the undesired high angle of attack flight state (stall) and the agile maneuvering of the aircraft in various air combat or defense missions, are performed. In order to accomplish this task, the thrust vectoring control (TVC) actuation is blended with the conventional aerodynamic controls. The controller design is based on the nonlinear dynamic inversion (NDI) control methodologies and the stability and robustness analyses are done by using robust performance (RP) analysis techniques. The control architecture is designed to serve both for the recovery from the undesired stall condition (the stabilization controller) and to perform desired agile maneuvering (the attitude controller). The detailed modeling of the aircraft dynamics, aerodynamics, engines and thrust vectoring paddles, as well as the flight environment of the aircraft and the on-board sensors is performed. Within the control loop the human pilot model is included and the design of a fly-by-wire controller is also investigated. The performance of the designed stabilization and attitude controllers are simulated using the custom built 6 DoF aircraft flight simulation tool. As for the stabilization controller, a forced deep-stall flight condition is generated and the aircraft is recovered to stable and pilot controllable flight regimes from that undesired flight state. The performance of the attitude controller is investigated under various high angle of attack agile maneuvering conditions. Finally, the performances of the proposed controller schemes are discussed and the conclusions are made.

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2

Walter, Daniel James, and Daniel james walter@gmail com. "Study of aerofoils at high angle of attack in ground effect." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080110.145138.

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Aerodynamic devices, such as wings, are used in higher levels of motorsport (Formula-1 etc.) to increase the contact force between the road and tyres (i.e. to generate downforce). This in turn increases the performance envelope of the race car. However the extra downforce increases aerodynamic drag which (apart from when braking) is generally detrimental to lap-times. The drag acts to slow the vehicle, and hinders the effect of available drive power and reduces fuel economy. Wings, in automotive use, are not constrained by the same parameters as aircraft, and thus higher angles of attack can be safely reached, although at a higher cost in drag. Variable geometry aerodynamic devices have been used in many forms of motorsport in the past offering the ability to change the relative values of downforce and drag. These have invariably been banned, generally due to safety reasons. The use of active aerodynamics is currently legal in both Formula SAE (engineering compet ition for university students to design, build and race an open-wheel race car) and production vehicles. A number of passenger car companies are beginning to incorporate active aerodynamic devices in their designs. In this research the effect of ground proximity on the lift, drag and moment coefficients of inverted, two-dimensional aerofoils was investigated. The purpose of the study was to examine the effect ground proximity on aerofoils post stall, in an effort to evaluate the use of active aerodynamics to increase the performance of a race car. The aerofoils were tested at angles of attack ranging from 0° - 135°. The tests were performed at a Reynolds number of 2.16 x 105 based on chord length. Forces were calculated via the use of pressure taps along the centreline of the aerofoils. The RMIT Industrial Wind Tunnel (IWT) was used for the testing. Normally 3m wide and 2m high, an extra contraction was installed and the section was reduced to form a width of 295mm. The wing was mounted between walls to simulate 2-D flow. The IWT was chosen as it would allow enough height to reduce blockage effect caused by the aerofoils when at high angles of incidence. The walls of the tunnel were pressure tapped to allow monitoring of the pressure gradient along the tunnel. The results show a delay in the stall of the aerofoils tested with reduced ground clearance. Two of the aerofoils tested showed a decrease in Cl with decreasing ground clearance; the third showed an increase. The Cd of the aerofoils post-stall decreased with reduced ground clearance. Decreasing ground clearance was found to reduce pitch moment variation of the aerofoils with varied angle of attack. The results were used in a simulation of a typical Formula SAE race car.

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3

Petterson, Kristian. "The aerodynamics of slender aircraft forebodies at high angle of attack." Thesis, Cranfield University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392234.

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4

Mohmad, Rouyan Nurhana. "Model simulation suitable for an aircraft at high angle of attack." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/9722.

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Simulation of a dynamic system is known to be sensitive to various factors and one of them could be the precision of model parameters. While the sensitivity of flight dynamic simulation to small changes in aerodynamic coefficients is typically not studied, the simulation of aircraft required to operate in nonlinear flight regimes usually at high angles of attack can be very sensitive to such small differences. Determining the significance and impact of the differences in aerodynamic characteristics is critical for understanding the flight dynamics and designing suitable flight control laws. This thesis uses this concept to study the effect of the differences in aerodynamic data for different aerodynamic models provided for a same aircraft which is F-18 HARV combat aircraft. The aircraft was used as a prototype for the high angles of attack technology program. However modeling an aircraft at high angles of attack requires an extensive aerodynamic data which are usually di cult to access. All aerodynamic models were collected from open literature and implemented within a nonlinear six degree of freedom aircraft model. Inspection of aerodynamic data set for these models has shown mismatches for certain aerodynamic derivatives, especially at higher angles of attack where nonlinear dynamics are known to exist. Nonlinear simulations are used to analyse three different types of flight dynamic models that use look-up-tables, arc-tangent formulation and polynomial functions to represent aerodynamic data that are suitable for high angles of attack application. To achieve this, a nonlinear six degree of freedom Simulink model was developed to accommodate these aerodynamic models separately. The trim conditions were obtained for different combinations of angles of attack and airspeed and the models were linearized in each case. Properties of the resulting state matrices such as eigenvalues and eigenvectors were studied to determine the dynamic behaviour of the aircraft at various flight conditions.

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5

Stucke, Russell Andrew. "High Angle-of-Attack Yaw Control Using Strakes on Blunt-Nose Bodies." University of Toledo / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1167777201.

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6

Ravi, R. "High Angle of Attack Forebody Flow Physics and Design Emphasizing Directional Stability." Diss., This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-01252008-163458/.

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7

Yip, Pui-Chuen Patrick. "A comparison of control design options for high angle-of-attack flights." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13431.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science.
Includes bibliographical references (p. 168-170).
by Pui-Chuen Patrik Yip.
M.S.

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8

Stagg, Gregory A. "An Aerodynamic Model for Use in the High Angle of Attack Regime." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/35596.

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Harmonic oscillatory tests for a fighter aircraft using the Dynamic Plunge--Pitch--Roll model mount at Virginia Tech Stability Wind Tunnel are described. Corresponding data reduction methods are developed on the basis of multirate digital signal processing. Since the model is sting mounted, the frequencies associated with sting vibration are included in balance readings thus a linear filter must be used to extract out the aerodynamic responses. To achieve this, a Finite Impulse Response (FIR) is designed using the Remez exchange algorithm. Based on the reduced data, a state--space model is developed to describe the unsteady aerodynamic characteristics of the aircraft during roll oscillations. For this model, we chose to separate the aircraft into panels and model the local forces and moments. Included in this technique is the introduction of a new state variable, a separation state variable which characterizes the separation for each panel. This new variable is governed by a first order differential equation. Taylor series expansions in terms of the input variables were performed to obtain the aerodynamic coefficients of the model. These derivatives, a form of the stability derivative approach, are not constant but rather quadratic functions of the new state variable. Finally, the concept of the model was expanded to allow for the addition of longitudinal motions. Thus, pitching moments will be identified at the same time as rolling moments. The results show that the goal of modeling coupled longitudinal and lateral--directional characteristics at the same time using the same inputs is feasible.
Master of Science

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9

Ko, Joon Soo. "Analysis of the dynamic stability derivatives for high angle of attack aircraft." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/52300.

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Modern, high performance aircraft are required to be able to fly and be controlled over a wide variety of flight conditions. In order to predict the aircraft behavior and control requirements over the entire flight regime it is necessary to have a proper aerodynamic model. Flight conditions at high angles of attack lead to separated flows making the aerodynamic model more difficult to obtain. In this research wind tunnel experiments are performed on an F-5 air-craft model at high angles of attack, with small oscillations about the body oriented roll axis. In addition the free stream environment can be configured in one of three ways: l) straight uniform flow, 2) curved flow to simulated a horizontal turn, and 3) rolling flow to simulated a roll motion about the relative Velocity vector.
Ph. D.

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10

Sirangu, Vijaya. "AERODYNAMIC CONTROL OF SLENDER BODIES AT HIGH ANGLES OF ATTACK." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271365316.

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11

Jouannet, Christopher. "Model based aircraft design : high angle of attack aerodynamics and weight estimation methods /." Linköping : Dept. of Mechanical Engineering, Linköping University, 2005. http://www.bibl.liu.se/liupubl/disp/disp2005/tek968s.pdf.

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12

Johnson, Dan A. "Flowfield measurements in the wake of a missile at high angle of attack." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/27059.

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13

Fan, Yigang. "Identification of an Unsteady Aerodynamic Model up to High Angle of Attack Regime." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29830.

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The harmonic oscillatory tests for a fighter aircraft configuration using the Dynamic Plunge-Pitch-Roll (DyPPiR) model mount at Virginia Tech Stability Wind Tunnel are described and analyzed. The corresponding data reduction methods are developed on the basis of multirate digital signal processing techniques. Since the model is sting-mounted to the support system of DyPPiR, the Discrete Fourier Transform (DFT) is first used to identify the frequencies of the elastic modes of sting. Then the sampling rate conversion systems are built up in digital domain to resample the data at a lower rate without introducing distortions to the signals of interest. Finally linear-phase Finite Impulse Response (FIR) filters are designed by Remez exchange algorithm to extract the aerodynamic characteristics responses to the programmed motions from the resampled measurements. These data reduction procedures are also illustrated through examples. The results obtained from the harmonic oscillatory tests are then illustrated and the associated flow mechanisms are discussed. Since no significant hysteresis loops are observed for the lift and the drag coefficients for the current angle of attack range and the tested reduced frequencies, the dynamic lags of separated and vortex flow effects are small in the current oscillatory tests. However, large hysteresis loops are observed for pitch moment coefficient in the current tests. This observation suggests that at current flow conditions, pitch moment has large pitch rate and alpha-dot dependencies. Then the nondimensional maximum pitch rate q__max is introduced to characterize these harmonic oscillatory motions. It is found that at current flow conditions, all the hysteresis loops of pitch moment coefficient with same nondimensional maximum pitch rate are tangential to one another at both top and bottom of the loops, implying approximately same maximum offset of these loops from static values. Several cases are also illustrated. Based on the results obtained and those from references, a state-space model is developed to describe the unsteady aerodynamic characteristics up to the high angle of attack regime. A nondimensional coordinate is introduced as the state variable describing the flow separation or vortex burst. First-order differential equation is used to govern the dynamics of flow separation or vortex bursting through this state variable. To be valid for general configurations, Taylor series expansions in terms of the input variables are used in the determination of aerodynamic characteristics, resembling the current approach of the stability derivatives. However, these derivatives are longer constant. They are dependent on the state variable of flow separation or vortex burst. In this way, the changes in stability derivatives with the angle of attack are included dynamically. The performance of the model is then validated by the wind-tunnel measurements of an NACA 0015 airfoil, a 70 degree delta wing and, finally two F-18 aircraft configurations. The results obtained show that within the framework of the proposed model, it is possible to obtain good agreement with different unsteady wind tunnel data in high angle-of-attack regime.
Ph. D.

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14

MAY, CAMERON. "HIGH ANGLE OF ATTACK FLIGHT CONTROL OF DELTA WING AIRCRAFT USING VORTEX ACTUATORS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1109166873.

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15

Rosti, Marco. "Direct numerical simulation of an aerofoil at high angle of attack and its control." Thesis, City, University of London, 2016. http://openaccess.city.ac.uk/15843/.

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Detailed analysis of the flow around a NACA0020 aerofoil at moderate low chord Reynolds number (Rec = 2×104) in completely stalled conditions has been carried out by means of Direct Numerical Simulations. The stalled condition is either a steady configuration at a fixed angle of attack (α = 20o) or it is reached via a ramp-up manoeuvre, increasing the angle of attack from 0o to 20o. Concerning this last case, new insights on the vorticity dynamics leading to the lift overshoot, lift crisis and the damped oscillatory cycle that gradually matches the steady condition, are discussed using a number of post-processing techniques. These include a detailed analysis of the flow ensemble average statistics and coherent structures identification that has been carried out using the Q-criterion and the Finite-Time Lyapunov Exponent technique. Based on the fundamental knowledge achieved in studying the static and the dynamic stall, we introduced a biomimetic passive control technique to mitigate the aerodynamic performance degradation typical of such flow conditions. In particular, the envisaged control technique has been inspired by the dorsal feathers that are used by almost all birds to adapt their wing characteristics to delay stall or to moderate its adverse effects (e.g., during landing or sudden increase in angle of attack due to gusts). Some of the feathers are believed to pop up as a consequence of flow separation and to interact with the flow producing beneficial modifications of the unsteady vorticity field. The adoption of self adaptive flaplets in aircrafts, inspired by birds feathers, requires the understanding of the physical mechanisms leading to their aerodynamic benefits and the determination of the characteristics of optimal flaps including their size, positioning and ideal fabrication material. In this framework, we have used numerical simulation to study the effects of this passive control technique in both steady and dynamic stall. In particular, for the static case, we have defined an optimal condition as the one that delivers the highest lift coefficient CL, preserving or improving the aerodynamic efficiency E = CL/CD. To achieve a condition close to optimality we started by considering a simplified scenario, to determine the main characteristics of the flap (i.e., variations of its length, position and natural frequency). Later on, a detailed direct numerical simulation analysis is used to understand the origin of the aerodynamic benefits introduced by the pop-up of the optimal flaplet. It is found that an optimal flap can deliver a mean lift increase of about 20% on a NACA0020 aerofoil at an incidence of 20o degrees. The analysis of direct numerical simulation data of the flow field around the aerofoil equipped with the optimal flap allowed to elucidate the main mechanism that promotes the aerodynamic improvements. In particular, it is found that the flaplet movement, induced by the transit of a large recirculation bubble on the aerofoil suction side, displaces the trailing edge vortices further downstream, away from the wing. The downstream displacement of the trailing edge generated vortices, limits the downforce generated by those vortices also regularising the shedding cycle that appears to be much more organised when the flaplet is activated. A similar study has also been carried out for the dynamic case. We have analysed the effects produced by the presence of an elastically mounted flap on the transient behaviour of the flow fields. For a specific ramp-up manoeuvre characterised by a reduced frequency slower the shedding one, it is found that it is possible to design flaps that limit the severity of the dynamic stall breakdown. In particular, it is possible to increase the value of the lift overshoot and to smooth its abrupt decay in time. A detailed analysis on the modification of the unsteady vorticity field due to the flap-flow interaction during the ramp-up motion is also provided to explain the physical mechanism that lead to more benign aerodynamic response.

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16

Lego, Zachary Michael. "Analysis of High Angle of Attack Maneuvers to Enhance Understanding of the Aerodynamics of Perching." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1355101333.

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17

Coutley, Raymond L. "Numerical studies of compressible flow over a double-delta wing at high angle of attack." Thesis, Monterey, California. Naval Postgraduate School, 1990. http://hdl.handle.net/10945/30688.

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Approved for public release, distribution is unlimited
The objective of this work is the investigation of vortical flows at high angles of attack using numerical techniques. The first step for a successful application of a numerical technique, such as fimite difference or finite volume, is the generation of a computational mesh which can capture adequately and accurately the important physics of the flow. Therefore, the first part of this work deals with the grid generation over a double-delta wing and the second part deals with the visualization of the computed flow field over the double-delta wing at different angles of attack. The surface geometry of the double-delta wing is defined algebraically. The developed surface grid generator provides flexibility in distributing the surface points along the axial and circumferential directions. The hyperbolic grid generation method is chosen for the field grid generation and both cylindrical and spherical grids are constructed. The computed low speed (M = 0.2) flow results at different angles of attack over the double-delta wing are visualized. Important flow characteristics of the leeward side flow field are discussed while the development of vortex interaction, occurrence and progression of vortex breakdown as the angle of attack increases is demonstrated. The computed results at different fixed angles of attack are presented.

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18

Lung, Ming-Hung. "Flowfield measurements in the vortex wake of a missile at high angle of attack in turbulence." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23235.

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The flowfield downstream of a vertically-launched surface-to-air missile model at an angle of attack of 50° and a Reynolds number of 1.1 x 10(5) was investigated in a wind tunnel of the Naval Postgraduate School. The goal of this thesis is to experimentally validate the pressure measurement system for flowfield variables with elevated levels of turbulence; to determine the location and intensity of the asymmetric vortices in the wake of the VLSAM model at a raised level of freestream turbulence; and to display the asymmetric vortices by velocity mapping and pressure contours. The purpose is to correlate the results with the force measurements of Rabang to provide a greater understanding of the vortex flowfield. The body-only configuration was tested. Two flowfield conditions were treated: the nominal ambient wind tunnel condition, and a condition with grid generated turbulence of 3.8% turbulence intensity and a dissipation length scale of 1.7 inches. The following conclusions were reached: 1) The relative strengths of the asymmetric vortices can be noted by the sharp spike shape in the ambient condition; this condition becomes diffused and becomes fatter in the turbulent condition; 2) The right side vortex has greater strength than the left side one as seen by the diffusion in the total pressure coefficient and static pressure coefficient contours with and without a turbulent condition; 3) an increase in turbulence intensity tends to reduce the strength of the asymmetric nose-generated vortices; also pushes the two asymmetric vortices closer together; 4) and crossflow velocities were examined and were found to indicate the behavior denoted by the pressure contours.
http://archive.org/details/flowfieldmeasure00lung
Lieutenant, Republic of China Navy

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19

Takahama, Morio, Noboru Sakamoto, and Yuhei Yamato. "Attitude Stabilization of an Aircraft via Nonlinear Optimal Control Based on Aerodynamic Data." Institute of Electrical and Electronics Engineers, 2009. http://hdl.handle.net/2237/14420.

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20

Nadeau, Yvan. "A comparative non-linear analytical and numerical irrotational analysis of aerofoils at high angle of attack /." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55626.

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21

Lopera, Javier. "Aerodynamic Control of Slender Bodies from Low to High Angles of Attack through Flow Manipulation." Connect to Online Resource-OhioLINK, 2007. http://www.ohiolink.edu/etd/view.cgi?acc_num=toledo1177504352.

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22

Atkinson, Michael D. "Control of Hypersonic High Angle-Of-Attack Re-Entry Flow Using a Semi-Empirical Plasma Actuator Model." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1335283726.

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23

Pilkington, David J. "Motion induced unsteady aerodynamics at high angles-of-attack." Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760689.

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24

Alkhozam, Abdullah M. "Interaction, bursting and dynamic control of vortices of a cropped double-delta wing at high angle of attack." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA283656&Location=U2&doc=GetTRDoc.pdf.

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Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, March 1994.
Thesis advisor(s): S. K. Hebbar, M. F. Platzer. "March 1994." Cover title: Interaction, ... and control of vortices of a cropped ... Includes bibliographical references. Also available online.

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25

東, 大輔, Daisuke AZUMA, 佳朗中村, and Yoshiaki NAKAMURA. "前縁回転/後縁ジェットハイブリッド法によるデルタ翼揚力増加." 日本航空宇宙学会, 2006. http://hdl.handle.net/2237/13878.

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26

Schaeffler, Norman Walter. "All The King's Horses: The Delta Wing Leading-Edge Vortex System Undergoing Vortex Breakdown: A Contribution to its characterization and Control under Dynamic Conditions." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30454.

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The quality of the flow over a 75 degree-sweep delta wing was documented for steady angles of attack and during dynamic maneuvers with and without the use of two control surfaces. The three-dimensional velocity field over a delta wing at a steady angle of attack of 38 degrees and Reynolds number of 72,000 was mapped out using laser-Doppler velocimetry over one side of the wing. The three-dimensional streamline and vortex line distributions were visualized. Isosurfaces of vorticity, planar distributions of helicity and all three vorticity components, and the indicator of the stability of the core were studied and compared to see which indicated breakdown first. Visualization of the streamlines and vortex lines near the core of the vortex indicate that the core has a strong inviscid character, and hence Reynolds number independence, upstream of breakdown, with viscous effects becoming more important downstream of the breakdown location. The effect of cavity flaps on the flow over a delta wing was documented for steady angles of attack in the range 28 degrees to 42 degrees by flow visualization and surface pressure measurements at a Reynolds number of 470,000 and 1,000,000, respectfully. It was found that the cavity flaps postpone the occurrence of vortex breakdown to higher angles of attack than can be realized by the basic delta wing. The effect of continuously deployed cavity flaps during a dynamic pitch-up maneuver of a delta wing on the surface pressure distribution were recorded for a reduced frequency of 0.0089 and a Reynolds number of 1,300,000. The effect of deploying a set of cavity flaps during a dynamic pitch-up maneuver on the surface pressure distribution was recorded for a reduced frequency of 0.0089 and a Reynolds number of 1,300,000 and 187,000. The active deployment of the cavity flaps was shown to have a short-lived beneficial effect on the surface pressure distribution. The effect on the surface pressure distribution of the varying the reduced frequency at constant Reynolds number for a plain delta wing was documented in the reduced frequency range of 0.0089 to 0.0267. The effect of the active deployment of an apex flap during a pitch-up maneuver on the surface pressure distribution at Reynolds numbers of 532,000, 1,000,000, and 1,390,000 were documented with reduced frequencies of 0.0053 to 0.0114 with flap deployment locations in the range of 21Â° to 36Â° . The apex flap deployment was found to have a beneficial effect on the surface pressure distribution during the maneuver and in the post-stall regime after the maneuver is completed.
Ph. D.

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27

Ponton, Anthony J. C. "The evaluation of canard couplings at high angles of attack." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389992.

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28

Crowther, William James. "Yaw control at high angles of attack by tangential forebody blowing." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239945.

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29

Mathre, John Mark. "Computational investigation of incompressible airfoil flows at high angles of attack." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22965.

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Cebeci's viscous/inviscid interaction program was applied to the analysis of steady, two dimensional, incompressible flow past four airfoils, the NACA 66₃-018, 0010 (Modified), 4412 and the Wortmann FX 63-137. Detailed comparisons with the available experimental results show that the essential features are correctly modelled, but that significant discrepancies are found in regions of flow separations.
http://archive.org/details/computationalinv00math
Lieutenant, United States Navy

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30

De, Oliveira Neto Pedro Jose. "An Investigation of Unsteady Aerodynamic Multi-axis State-Space Formulations as a Tool for Wing Rock Representation." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29600.

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The objective of the present research is to investigate unsteady aerodynamic models with state equation representations that are valid up to the high angle of attack regime with the purpose of evaluating them as computationally affordable models that can be used in conjunction with the equations of motion to simulate wing rock. The unsteady aerodynamic models with state equation representations investigated are functional approaches to modeling aerodynamic phenomena, not directly derived from the physical principles of the problem. They are thought to have advantages with respect to the physical modeling methods mainly because of the lower computational cost involved in the calculations. The unsteady aerodynamic multi-axis models with state equation representations investigated in this report assume the decomposition of the airplane into lifting surfaces or panels that have their particular aerodynamic force coefficients modeled as dynamic state-space models. These coefficients are summed up to find the total aircraft force coefficients. The products of the panel force coefficients and their moment arms with reference to a given axis are summed up to find the global aircraft moment coefficients. Two proposed variations of the state space representation of the basic unsteady aerodynamic model are identified using experimental aerodynamic data available in the open literature for slender delta wings, and tested in order to investigate their ability to represent the wing rock phenomenon. The identifications for the second proposed formulation are found to match the experimental data well. The simulations revealed that even though it was constructed with scarce data, the model presented the expected qualitative behavior and that the concept is able to simulate wing rock.
Ph. D.

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31

Salemi, Leonardo da Costa, and Leonardo da Costa Salemi. "Numerical Investigation of Hypersonic Conical Boundary-Layer Stability Including High-Enthalpy and Three-Dimensional Effects." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621854.

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The spatial stability of hypersonic conical boundary layers is investigated utilizing different numerical techniques. First, the development and verification of a Linearized Compressible Navier-Stokes solver (LinCS) is presented, followed by an investigation of different effects that affect the stability of the flow in free-flight/ground tests, such as: high-enthalpy effects, wall-temperature ratio, and three-dimensionality (i.e. angle-of-attack). A temporally/spatially high-order of accuracy parallelized Linearized Compressible Navier-Stokes solver in disturbance formulation was developed, verified and employed in stability investigations. Herein, the solver was applied and verified against LST, PSE and DNS, for different hypersonic boundary-layer flows over several geometries (e.g. flat plate - M=5.35 & 10; straight cone - M=5.32, 6 & 7.95; flared cone - M=6; straight cone at AoA = 6 deg - M=6). The stability of a high-enthalpy flow was investigated utilizing LST, LinCS and DNS of the experiments performed for a 5 deg sharp cone in the T5 tunnel at Caltech. The results from axisymmetric and 3D wave-packet investigations in the linear, weakly, and strongly nonlinear regimes using DNS are presented. High-order spectral analysis was employed in order to elucidate the presence of nonlinear couplings, and the fundamental breakdown of second mode waves was investigated using parametric studies. The three-dimensionality of the flow over the Purdue 7 deg sharp cone at M=6 and AoA =6 deg was also investigated. The development of the crossflow instability was investigated utilizing suction/blowing at the wall in the LinCS/DNS framework. Results show good agreement with previous computational investigations, and that the proper basic flow computation/formation of the vortices is very sensitive to grid resolution.

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32

Tait, Sean William. "An investigation of fore-body aerodynamics during the velocity vector roll." Thesis, University of the West of Scotland, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265929.

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33

Munro, Cameron. "Water tunnel validation and experiments at high angles of attack for aircraft conceptual design /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2002/tek847s.pdf.

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34

Bean, David. "The analysis and suppression of vortex induced unsteady loads at high angles of attack." Thesis, University of Bath, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306707.

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35

Greenwell, D. I. "Control of asymmetric vortical flow over a delta wing at high angles of attack." Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334618.

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36

Cetiner, Abdullah Emre. "Split Canard Design For Enhancing The Maneuverability Of A Missile At High Angles Of Attack." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614920/index.pdf.

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In this thesis, the effects of split canard on the aerodynamic characteristics of missiles at high angles of attack are numerically investigated. Moreover, an enhanced semi-empirical engineering-level method is developed for prediction of normal force and pitching moment of split canard mounted missiles. In order to analyze the effects of split canard, a generic test case model is created by mounting a split canard to a generic test case model, NASA Dual Control Missile (NDCM), which was previously modeled and analyzed for the validation of CFD modeling. After obtaining a generic missile model with split canard, the effects of split canard on the aerodynamic characteristics of this missile in case of no control, pitch control, yaw control, and roll control deflections are numerically investigated. It is seen that the split canard decreases the local angle of attack of existing canard, increases the normal force and the maneuverability of the missile, and reduces the induced rolling moment at high angles of attack. Five different aerodynamic design parameters are determined for split canard and the effects of each parameter on missile aerodynamics are numerically investigated. It is seen that the roll orientation, deflection angle, size of the split canards have strong effects on missile&rsquo
s aerodynamic performance whereas longitudinal position of the split canards only affects the pitching moment of the missile. Finally, an enhanced semi-empirical engineering-level method, CFD-CBU, is developed for split canard mounted missiles in order to predict the normal force and the pitching moment coefficients. The developed method is validated with NDCM test case model. After this validation, the method is applied to the split canard mounted generic missile in case of no control deflection and pitch control deflection. The results of this method are compared with CFD results and it is seen that the results are in good agreement with each other.

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37

Chang, Wen-Huan. "Effect of juncture fillets on double-delta wings undergoing sideslip at high angles of attack." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA286165.

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Thesis (M.S. in Aeronautical Engieering) Naval Postgraduate School, September 1994.
Thesis advisor(s): S. K.Hebbar, Max F. Platzer. "September 1994." Includes bibliographical references. Also available online.

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38

Mondoloni, Stéphane Lucien. "A numerical method for modelling wings with sharp edges maneuvering at high angles of attack." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/49922.

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39

Hooper, Jack Charles. "Vertical landing flight envelope definition." Thesis, Luleå tekniska universitet, Rymdteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80717.

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This paper will investigate the development of a landing footprint for a re-entry vehicle. Vehicles can re-enter the atmosphere with a range of orientations, velocities and flight path angles. The central question is whether a vehicle with any combination of these states can be brought to an acceptable landing condition at a particular landing site and with a particular landing speed. To aide in this investigation several models must be implemented, including that of the atmosphere, the vehicles, the Earth, and the aerodynamics. A detailed analysis of the aerodynamic model will be treated, and the equations of motion subject to these aerodynamic laws will then be compared to results from existing atmospheric reentry software. The principles of optimization will then be employed to generate the footprint of landable states, based on maximum and minimum possible downrange distances, for two vehicle concepts.

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40

Le, Moigne Yann. "Adaptive Mesh Refinement and Simulations of Unsteady Delta-Wing Aerodynamics." Doctoral thesis, KTH, Aeronautical and Vehicle Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3786.

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This thesis deals with Computational Fluid Dynamics (CFD)simulations of the flow around delta wings at high angles ofattack. These triangular wings, mainly used in militaryaircraft designs, experience the formation of two vortices ontheir lee-side at large angles of attack. The simulation ofthis vortical flow by solving the Navier-Stokes equations isthe subject of this thesis. The purpose of the work is toimprove the understanding of this flow and contribute to thedesign of such a wing by developing methods that enable moreaccurate and efficient CFD simulations.

Simulations of the formation, burst and disappearance of thevortices while the angle of attack is changing are presented.The structured flow solver NSMB has been used to get thetime-dependent solutions of the flow. Both viscous and inviscidresults of a 70°-swept delta wing pitching in anoscillatory motion are reported. The creation of the dynamiclift and the hysteresis observed in the history of theaerodynamic forces are well reproduced.

The second part of the thesis is focusing on automatic meshrefinement and its influence on simulations of the delta wingleading-edge vortices. All the simulations to assess the gridquality are inviscid computations performed with theunstructured flow solver EDGE. A first study reports on theeffects of refining thewake of the delta wing. A70°-swept delta wing at a Mach number of 0.2 and an angleof attack of 27° where vortex breakdown is present abovethe wing, is used as testcase. The results show a strongdependence on the refinement, particularly the vortex breakdownposition, which leads to the conclusion that the wake should berefined at least partly. Using this information, a grid for thewing in the wind tunnel is created in order to assess theinfluence of the tunnel walls. Three sensors for automatic meshrefinement of vortical flows are presented. Two are based onflow variables (production of entropy and ratio of totalpressures) while the third one requires an eigenvalue analysisof the tensor of the velocity gradients in order to capture theposition of the vortices in the flow. These three vortexsensors are successfully used for the simulation of the same70° delta wing at an angle of attack of 20°. Acomparison of the sensors reveals the more local property ofthe third one based on the eigenvalue analysis. This lattertechnique is applied to the simulation of the wake of a deltawing at an angle of attack of 20°. The simulations on ahighly refined mesh show that the vortex sheet shed from thetrailing-edge rolls up into a vortex that interacts with theleading-edge vortex. Finally the vortex-detection technique isused to refine the grid around a Saab Aerosystems UnmannedCombat Air Vehicle (UCAV) configuration and its flight dynamicscharacteristics are investigated.

Key words:delta wing, high angle of attack, vortex,pitching, mesh refinement, UCAV, vortex sensor, tensor ofvelocity gradients.

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41

Morris, Seth Henderson. "Quasi-Transient Calculation of Surface Temperatures on a Reusable Booster System with High Angles of Attack." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1324573899.

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42

Li, Feng-Hsi. "Static and dynamic flow visualization studies of two double-delta wing models at high angles of attack." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23777.

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43

Sommers, John Douglas. "An experimental investigation of support strut interference on a three-percent fighter model at high angles of attack." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25926.

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44

Worasinchai, Supakit. "Small wind turbine starting behaviour." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/4436/.

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Small wind turbines that operate in low-wind environments are prone to suffer performance degradation as they often fail to accelerate to a steady, power-producing condition. The behaviour during this process is called “starting behaviour” and it is the subject of this present work. This thesis evaluates potential benefits that can be obtained from the improvement of starting behaviour, investigates, in particular, small wind turbine starting behaviour (both horizontal- and vertical-axis), and presents aerofoil performance characteristics (both steady and unsteady) needed for the analysis. All of the investigations were conducted using a new set of aerodynamic performance data of six aerofoils (NACA0012, SG6043, SD7062, DU06-W-200, S1223, and S1223B). All of the data were obtained at flow conditions that small wind turbine blades have to operate with during the startup - low Reynolds number (from 65000 to 150000), high angle of attack (through 360◦), and high reduced frequency (from 0.05 to 0.20). In order to obtain accurate aerodynamic data at high incidences, a series of CFD simulations were undertaken to illustrate effects of wall proximity and to determine test section sizes that offer minimum proximity effects. A study was carried out on the entire horizontal-axis wind turbine generation system to understand its starting characteristics and to estimate potential benefits of improved starting. Comparisons of three different blade configurations reveal that the use of mixed-aerofoil blades leads to a significant increase in starting capability. The improved starting capability effectively reduces the time that the turbine takes to reach its power-extraction period and, hence, an increase in overall energy yield. The increase can be as high as 40%. Investigations into H-Darriues turbine self-starting capability were made through the analogy between the aerofoil in Darrieus motion and flapping-wing flow mechanisms. The investigations reveal that the unsteadiness associated with the rotor is key to predicting its starting behaviour and the accurate prediction can be made when this transient aerofoil behaviour is correctly modelled. The investigations based upon the analogy also indicate that the unsteadiness can be exploited to promote the turbine ability to self-start. Aerodynamically, this exploitation is related to the rotor geometry itself.

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45

Hammer, Patrick Richard. "A Discrete Vortex Method Application to Low Reynolds Number Aerodynamic Flows." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1311792450.

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46

Frink, William D. Jr. "Hot-wire surveys in the vortex wake downstream of a three-percent fighter aircraft model at high angles of attack." Thesis, Monterey, California: Naval Postgraduate School, 1990. http://hdl.handle.net/10945/27586.

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Approved for public release; distribution is unlimited.
A low-speed wind tunnel investigation was conducted to examine the vortex wake downstream of a three-percent scale model of the YF-17 lightweight fighter prototype at high angles of attack. The study was in support of NASA ames Research Center's wind tunnel investigation of a full scale FA-18 as part of NASA's High Alpha Technology Program. Smoke flow visualization was used to locate the downstream vortex wake. Hot-wire surveys were taken through the vortex at two stations; one directly aft of the model and the other at a station three model lengths downstream of the model. The effect of adding a fence to the leading edge extension (LEX) was studied. Power spectra from the hot-wire were recorded for the survey station directly aft of the model. Results show that: peak turbulent fluctuation at this station occurred at 25 deg angle of attack; lateral turbulent fluctuation greatly diminished at the far downstream station; and the addition of the LEX fence shifted energy content of turbulence toward higher frequencies.

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47

Frink, William D. "Hot-wire surveys in the vortex wake downstream of a three-percent fighter aircraft model at high angles of attack." Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA241869.

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Thesis (M.S. in Engineering Science)--Naval Postgraduate School, December 1990.
Thesis Advisor(s): Hebbar, Sheshagiri K. ; Platzer, Max F. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Identifier(s): Trailling Vortices, Wake, Trubulent Flow, Jet Fighters, High Alpha (High Angle of Attack), Vortex Wake, Angle of Attack, Extendable Structures, Leading Edges, Fences, Lex Fences, Wind Tunnel Models, F-17 Aircraft, F/A-18 Aircraft, Wind Tunnel Tests, Hot Wire Anemometers, Theses. Author(s) subject terms: High Angle-of-Attack Aerodynamics, Hot-Wire Measurements, Wind Tunnel Studies. Includes bibliographical references (p. 24-25). Also available in print.

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48

Clark, Adam. "Predicting the Crosswind Performance of High Bypass Ratio Turbofan Engine Inlets." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1476265135449178.

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49

Cavazos, Odilon V. "A flow visualization study of LEX generated vortices on a scale model of F/A-18 fighter aircraft at high angles of attack." Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA236534.

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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 1990.
Thesis Advisor(s): Hebbar, S. K. ; Platzer, M. F. "June 1990." Description based on title screen as viewed on October 19, 2009. DTIC Descriptor(s): Angles, yaw, scale models, attack, motion, rates, moments, vortices, flow visualization, rupture, asymmetry, aerodynamic forces, leading edges, range(distance), statics, hysteresis, aerodynamics, high angles, pitch(motion). DTIC Indicator(s): Flow visualization, trailing vortices, F/A-18 aircraft. Author(s) subject terms: High angle of attack aerodynamics, effect of pitch rate and yaw, vortex development and bursting, flow visualization by dye injection, water tunnel studies, F/A-18 fighter aircraft. Includes bibliographical references (p. 44-45). Also available in print.

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50

Russ, Thomas William. "A surface flow visualization study of boundary layer behavior on the blades of a solid-wall compressor cascade at high angles of attack." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/53161.

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The oil-film surface flow visualization technique was applied to circular arc compressor blades in a solid wall, high aspect ratio cascade for the purpose of describing the transition from corner stall to full blade stall, and the blade surface flow under fully stalled conditions. Photos of the visualizations for three stagger angles are presented and analyzed. A map quantitatively describing the observed boundary layer development at midspan is presented. The most interesting discovery of the work showed the suction surface flow to be essentially two-dimensional, in the geometric sense, preceding and following the transition to a fully separated flow at the leading edge. Corner stall was the observed three-dimensional mechanism prior to full stall. For fully-stalled conditions, the three-dimensional mechanism took the form of recirculating flow regions at the blade ends. Complete separation at the leading edge occurred at lower angles of attack for the higher stagger angles. Special blade oil-flow tests were conducted to evaluate Reynolds number and tip clearance effects on boundary layer development. The experimental work was done as part of a larger research program aimed at measuring and predicting the stalled performance of a compressor cascade.
Master of Science

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