Aerospace Engineering Commons^™

Flightlines, Vol. 12, No. 1, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Modeling And Simulation Research And Instruction At The U.S. Air Force Academy, Russell M. Cummings, Scott A. Morton, Keith Bergeron

Aerospace Engineering

Modeling and simulation has become a driving force within the engineering and science communities as the cost of, and time for, experimentation continues to rise. Some areas of study, such as chemistry and biology, may not even have the ability to fully evaluate certain processes experimentally, making modeling and simulation even more important. The situation has led many areas of research to the necessity of modeling and simulating various processes using computers. In addition, the rise in computational capabilities (the supercomputers of a decade ago are outmoded by the PC clusters of today), has led to a paradigm shift from …

High Resolution Turbulence Treatment Of F/A-18 Tail Buffet, Scott A. Morton, Russell M. Cummings, Denis B. Kholodar

Aerospace Engineering

Unsteady tail loads of the F/A-18 are computed using various turbulence models at an angle of attack consistent with buffet induced by leading-edge extension vortex breakdown. Comparison of these industry standard turbulence models with the Detached Eddy Simulation (DES) hybrid RANS-LES approach reveals the inadequacies of RANS methods and the ability of DES to reproduce the observed unsteadiness at these conditions. Computed vortex breakdown position and frequencies of the DES method are shown to be accurate by comparison to flight test and experimental results. Finally, comparison of the DES unsteady tail pressures with flight-test tail pressures reveal the ability of …

Flightlines, Vol. 11, No. 2, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Data Smoothing And Interpolation Using Eighth-Order Algebraic Splines, Daniel J. Simon

Electrical and Computer Engineering Faculty Publications

A new type of algebraic spline is used to derive a filter for smoothing or interpolating discrete data points. The spline is dependent on control parameters that specify the relative importance of data fitting and the derivatives of the spline. A general spline of arbitrary order is first formulated using matrix equations. We then focus on eighth-order splines because of the continuity of their first three derivatives (desirable for motor and robotics applications). The spline's matrix equations are rewritten to give a recursive filter that can be implemented in real time for lengthy data sequences. The filter is lowpass with …

Astronaut Eva Exposure Estimates From Cad Model Spacesuit Geometry, Giovanni De Angelis, Brooke M. Anderson, William Atwell, John E. Nealy, Gary D. Qualls, John W. Wilson

Mathematics & Statistics Faculty Publications

Ongoing assembly and maintenance activities at the International Space Station (ISS) require much more extravehicular activity (EVA) than did the earlier U.S. Space Shuttle missions. It is thus desirable to determine and analyze, and possibly foresee, as accurately as possible what radiation exposures crew members involved in EVAs will experience in order to minimize risks and to establish exposure limits that must not to be exceeded. A detailed CAD model of the U.S. Space Shuttle EVA Spacesuit, developed at NASA Langley Research Center (LaRC), is used to represent the directional shielding of an astronaut; it has detailed helmet and backpack …

Airplane Design And The Biomechanics Of Flight – A More Completely Multi- Disciplinary Perspective, John H. Mcmasters, Russell M. Cummings

Aerospace Engineering

Aeronautics is usually presumed to have started as a formal engineering discipline somewhere in historical time between the mythological experiments of Daedalus and his ill-fated son, Icarus; and the dreams and schemes of Leonardo da Vinci during the Italian Renaissance. As reviewed in this paper, “aeronautics” has a far longer history, extending over a period of about 300 million years beginning with the evolution of the ability of insects to fly. With the advent of the success of the Wright brothers, technologists quickly turned their attention from the inspirations and lessons provided by natural models of flying machines to …

Some Systemic Issues In The Development Of The Aerospace Industry Technical Workforce Of The Future, John H. Mcmasters, Russell M. Cummings

Aerospace Engineering

This paper is a continuation of the authors’ previous examinations of a suite of issues surrounding the putative decline in aeronautics in this country. The purpose of this paper is to discuss three specific issues believed to be of particular importance to the future of our industry. The first is the question of how many engineers we may need in our future as we confront the problem of an aging workforce and the globalization of our industry. The second is the question of what skills and abilities these engineers will need to possess as the overall industry continues to evolve. …

Detached-Eddy Simulation Of Slat And Flap Aerodynamics For A High-Lift Wing, Russell M. Cummings, Scott A. Morton, James R. Forsythe

Aerospace Engineering

Three-dimensional multi-element wings are simulated to investigate slat and flap aerodynamics using Detached-Eddy Simulation. The computations are performed by solving the Navier-Stokes equations on unstructured grids. All of the computed cases include the main wing with a half-span flap deflected to 39 degrees and a three-quarter-span slat deflected to 6 degrees. Computations of the model, which simulates a landing configuration at 10 degrees angle of attack and a chord-based Reynolds number of 3.7 million, are validated with surface pressure measurements acquired at the NASA Ames 7- by 10-Foot Wind Tunnel. The results increase the computational knowledge of how to accurately …

An Embedded Boundary Cartesian Grid Scheme For Viscous Flows Using A New Viscous Wall Boundary Condition Treatment, David D. Marshall, Stephen M. Ruffin

Aerospace Engineering

This work presents a new viscous wall boundary condition technique for embedded Cartesian grid schemes in order to model laminar viscous flows. The development of viscous effects modeling using pure Cartesian grids with cut cells at the surface has been hampered by the widely varying control volume sizes associated with the mesh refinement and the cut cells associated with the solid surface. This scheme removes the cells adjacent to the surface from the control volume formulation. These cells are instead solved via an interpolation technique which utilizes the wall boundary conditions to build the interpolating functions. Two different interpolation techniques …

A New Inviscid Wall Boundary Condition Treatment For Embedded Boundary Cartesian Grid Schemes, David D. Marshall, Stephen M. Ruffin

Aerospace Engineering

This work presents a new inviscid wall boundary condition technique for embedded Cartesian grid schemes. This scheme eliminates the time step restrictions associated with the arbitrarily small control volumes that can result when the surface cuts the Cartesian control volumes. The cells adjacent to the surface are removed from the control volume formulation and are instead solved via an interpolation technique which utilizes the wall boundary conditions to build the interpolating functions. Two different interpolation techniques are presented, one without considering wall curvature and one considering wall curvature. Results are compared to a two-dimensional airfoil case and a three-dimensional wing …

Biomimetic Model Of Skeletal Muscle Isometric Contraction: I. An Energetic–Viscoelastic Model For The Skeletal Muscle Isometric Force Twitch, C. A. Phillips, D. W. Repperger, A. T. Neidhard-Doll, D. B. Reynolds

U.S. Air Force Research

This paper describes a revision of the Hill-type muscle model so that it will describe the chemo-mechanical energy conversion process (energetic) and the internal-element sti2ness variation (viscoelastic) during a skeletal muscle isometric force twitch contraction. The derivation of this energetic–viscoelastic model is described by a 3rst-order linear ordinary di2erential equation with constant energetic and viscoelastic coe5cients. The model has been implemented as part of a biomimetic model, which describes the excitation–contraction coupling necessary to drive the energetic–viscoelastic model. Finally, the energetic–viscoelastic model is validated by comparing its isometric force–time pro3le with that of various muscles reported in the literature.

Tether Reel Mechanism For The Mr Sat Project, Abbie Stewart

Opportunities for Undergraduate Research Experience Program (OURE)

The Missouri-Rolla Satellite (MR SAT) system is being designed and constructed by students at the University of Missouri - Rolla in order to give Aerospace Engineering students along with other major's practical experience in spaceflight concepts. The satellite system will consist of two tethered satellites that will eventually be completely disconnected and use a propulsion method to enter the chase phase of our mission. New design concepts are being used on this satellite including the possible use of a honeycomb-aluminum friction stir-welded structure and micro-pulse plasma thrusters for maneuvering. The research done this summer focused on the tether reel mechanism …

Open-Ended Problem-Solving Skills In Thermal-Fluids Engineering, Nikos J. Mourtos, Nicole Dejong-Okamoto, Jinny Rhee

Faculty Publications

Problem-solving skills have always been important in many professions. However, ABET EC 2000 recently placed a new focus on these skills in engineering education with outcome 3e, which states that engineering graduates must have an ability to identify, formulate and solve engineering problems. Problem-solving is defined as a process used to obtain a best answer to an unknown or a decision that is subject to some constraints. Problem-solving is not the same as textbook exercise solving, which is very common in engineering curricula. In the article, the authors first define engineering problem-solving and, in particular, what it means to identify …

The Cool Flames Experiment: Recent Results At Reduced And Partial Gravity, Michael R. Foster

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Cool flames at Earth (1g), Martian (0.38g), Lunar (0.18g) and reduced-gravity (10–2g) have been studied experimentally in a closed, unstirred, static reactor to better understand the role of natural convection and diffusive transport on the induction period(s), flame shape, flame propagation speed, pressure history and temperature profile. Natural convection is known to play an important role in all terrestrial, unstirred, static reactor cool flame and auto-ignition experiments when the Rayleigh number exceeds 600 [2,3,6]. At 1g, typical values of the Ra are 10^4-10^6.

In this paper, experimental results from static, unstirred reactor studies conducted at four different gravitational acceleration levels …

Analysis Of Jet-Wing Distributed Propulsion From Thick Wing Trailing Edges, Serhat Hosder, Joseph A. Schetz, Vance Dippold

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Conventional airliners use two to four engines in a Cayley-type arrangement to provide thrust, and the thrust is concentrated right behind the engine. Distributed propulsion is the idea of redistributing the thrust across most, or all, of the wingspan of an aircraft. This can be accomplished by using several large engines and using a duct to spread out the exhaust flow to form a jet-wing or by using many small engines spaced along the span of the wing. Jet-wing distributed propulsion was originally suggested as a way to improve propulsive efficiency. A previous study at Virginia Tech assessed the potential …

Airframe Noise Modeling Appropriate For Multidisciplinary Design And Optimization, Serhat Hosder, Bernard Grossman, Joseph A. Schetz, William H. Mason

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Trailing Edge Noise Metric has been developed for constructing response surfaces that may be used for optimization problems involving aerodynamic noise from a clean wing. The modeling approach includes a modified version of a theoretical trailing edge noise prediction and utilizes a high fidelity CFD (RANS) code with a two-equation turbulence model to obtain the characteristic velocity and length scales used in the noise model. The noise metric is not the absolute value of the noise intensity, but an accurate relative noise measure as shown in the validation studies. Parametric studies were performed to investigate the effect of the …

Automatic Feedback Control Of Mechanical Gas Face Seals Via Clearance Control, Sachin S. Yelma, Robert G. Landers, Brad A. Miller

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An approach based on proper orthogonal decomposition and Galerkin projection is presented for developing low-order nonlinear models of the gas film pressure within mechanical gas face seals. A technique is developed for determining an optimal set of global basis functions for the pressure field using data measured experimentally or obtained numerically from simulations of the seal motion. The reduced-order gas film models are shown to be computationally efficient compared to full-order models developed using the conventional semidiscretization methods. An example of a coned mechanical gas face seal in a flexibly mounted stator configuration is presented. Axial and tilt modes of …

Development And Analysis Of A Feedback Treatment Strategy For Parturient Paresis Of Cows, Radhakant Padhi, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An intelligent on-line feedback treatment strategy based on nonlinear optimal control theory is presented for the parturient paresis of cows. A limitation in the development of an existing nonlinear mathematical model for the homogeneous system is addressed and further modified to incorporate a control input. A neural network based optimal feedback controller is synthesized for the treatment of the disease. Detailed studies are used to analyze the effectiveness of a feedback medication strategy and it is compared with the current "impulse" strategy. The results show that while the current practice may fail in some cases, especially if it is carried …

Optimal Beaver Population Management Using Reduced Order Distributed Parameter Model And Single Network Adaptive Critics, Radhakant Padhi, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using a distributed parameter model for beaver population that accounts for their spatial and temporal behavior, an optimal control for a desired distribution of the animals is presented. Optimal solutions are obtained through a "single network adaptive critic" (SNAC) neural network architecture. The objective of this research is to design an "optimal" beaver harvesting scheme for a region of interest.

Solid State Aircraft Concept Overview, M. Shahinpoor, P. Jenkins, C. Smith, Kakkattukuzhy M. Isaac, T. Dalbello, Anthony Colozza

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Due to recent advances in polymers, photovoltaics, and batteries a unique type of aircraft may be feasible. This is a "solid-state" aircraft, with no conventional mechanical moving parts. Airfoil, propulsion, energy production, energy storage and control are combined in an integrated structure. The key material of this concept is an ionic polymeric-metal composite (IPMC) that provides source of control and propulsion. This material has the unique capability of deforming in an electric field and returning to its original shape when the field is removed. Combining the IPMC with thin-film batteries and thin-film photovoltaics provides both energy source and storage in …

Stationkeeping Of An L₂ Libration Point Satellite With Θ-D Technique, Ming Xin, S. N. Balakrishnan, Henry J. Pernicka, Michael W. Dancer

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A new method for L₂ libration-point orbit stationkeeping is proposed in this paper using continuous thrust. The circular restricted three-body problem with Sun and Earth as the two primaries is considered. The unstable orbit about the L₂ libration-point requires stationkeeping maneuvers to maintain the nominal path. In this study, an approach, called the "θ-D technique," based on optimal control theory gives a closed-form suboptimal feedback solution to solve this nonlinear control problem. In this approach the Hamiltonian-Jacobi-Bellman (HJB) equation is solved approximately by adding some perturbations to the cost function. The controller is designed such that the actual …

United States Air Force Posture Statement 2004, U.S. Air Force

U.S. Air Force Research

In 2003, U.S. and coalition military operations produced unprecedented mission successes - across the spectrum of conflict and around the globe. The joint warfighting team demonstated combat capability never previously witnessed in the history of conflict.

The Houston Conference Revisited, Ralph M. Reitan, Jim Hom, Janet Van De Voorde, Daniel E. Stanczak, Deborah Wolfson

U.S. Air Force Research

This paper presents a review and critique of the Houston Conference on Specialty Education and Training in Clinical Neuropsychology, together with an informal summary of opinions of a number of neuropsychologists. Issues regarding the role of the Clinical Neuropsychology Synarchy (CNS) and the applicability of the conference policies are offered. Several deficiencies and limitations of the policy statement are discussed. An informal survey of neuropsychologists interested in the Houston Conference indicates rather different opinions concerning the training and education of neuropsychologists. It is our contention that the results of the Houston Conference can only be considered controversial at best and …

Optimal Control Synthesis Of A Class Of Nonlinear Systems Using Single Network Adaptive Critics, Radhakant Padhi, Nishant Unnikrishnan, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive critic (AC) neural network solutions to optimal control designs using dynamic programming has reduced the need of complex computations and storage requirements that typical dynamic programming requires. In this paper, a "single network adaptive critic" (SNAC) is presented. This approach is applicable to a class of nonlinear systems where the optimal control (stationary) equation is explicitly solvable for control in terms of state and costate variables. The SNAC architecture offers three potential advantages; a simpler architecture, significant savings of computational load and reduction in approximation errors. In order to demonstrate these benefits, a real-life micro-electro-mechanical-system (MEMS) problem has been …

Characterization And Modeling Of Local Electromechanical Response In Stress-Biased Piezoelectric Actuators, N. Navapan-Traiphol, Robert W. Schwartz, Daniel S. Stutts, J. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Numerous investigators have explored the factors that contribute to the high electromechanical performance of stress-biased actuators with particular attention being given to the importance of the extrinsic (domain wall translation) response mechanism. Based on the variation in lateral stress through the thickness of the piezoelectric layer within these devices, it has been suggested that the piezoelectric coefficient varies as a function of position within the layer, though no direct evidence has been previously presented. In this study, the results of Moire interferometry investigations of local strains within these devices are reviewed. The technique permits effective depth-profiling of local deformations at …

Design And Technologies For A Smart Composite Bridge, K. Chandrashekhara, Prakash Kumar, Steve Eugene Watkins, Antonio Nanni

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An all-composite, smart bridge design for shortspan applications is described. The bridge dimensions are 9.14-m (30-ft.) long and 2.74-m (9-ft.) wide. A modular construction based on assemblies of pultruded fiber-reinforced-polymer (FRP) composite tubes is used to meet American Association of State Highway and Transportation Officials (AASHTO) H20 highway load ratings. The hollow tubes are 76 mm (3 in.) square and are made of carbon/vinyl-ester and glass/vinyl-ester. An extensive experimental study was carried out to obtain and compare properties (stiffness, strength, and failure modes) for a quarter portion of the full-sized bridge. The bridge response was measured for design loading, two-million-cycle …

Development And Implementation Of New Nonlinear Control Concepts For A Ua, Vijayakumar Janardhan, Derek Schmitz, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A reconfigurable flight control method is developed to be implemented on an Unmanned Aircraft (UA), a thirty percent scale model of the Cessna 150. This paper presents the details of the UAV platform, system identification, reconfigurable controller design, development, and implementation on the UA to analyze the performance metrics. A Crossbow Inertial Measurement Unit provides the roll, pitch and yaw accelerations and rates along with the roll and pitch. The 100400 mini-air data boom from spaceage control provides the airspeed, altitude, angle of attack and the side slip angles. System identification is accomplished by commanding preprogrammed inputs to the control …