Mechanical Engineering Commons^™

Global Characteristics And Structure Of Hydrogen-Air Counterflow Diffusion Flames, J. Zhao, Kakkattukuzhy M. Isaac, G. L. Pellett

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A model based on similarity transformation, for the nitrogen-diluted, H2-air opposed-jet laminar counterflow diffusion flame (CFDF), was developed independently of earlier models, and numerically solved to study flame location and flame structure and extinction limits. Numerical stiffness is handled by a special treatment of the species production term. Flame location with respect to the stagnation plane is identified as an important parameter that governs H2-air diffusion flames, and physical explanations are given to show how flame location is affected by fuel dilution, strain rate, and Lewis number. Results show very good agreement with experimental extinction conditions. The effect of thermal …

Gas And Liquid Phase Transport In Pulsed Fuel Sprays, Pete D. Jennings, James A. Drallmeier

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An infrared extinction technique was used to characterize spatially and temporally the vapor phase of a transient fuel spray. Optical extinction data were taken at two laser wavelengths and compared to obtain fuel vapor partial pressure values averaged over the line-of-sight through the spray. A transient fuel injector spray was characterized at several axial positions with a spatial resolution of 0.125 cm and a temporal resolution of 0.2 ms. With the knowledge of an axisymmetric spray pulse, the line-of-sight averaged results were deconvoluted to obtain spatially resolved vapor pressure data. The same spray was also characterized using phase/doppler interferometry to …

Radiative Heating In Scramjet Combustors, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Currently, there is considerable interest in scramjet engines for hypersonic aircraft and missiles. This paper presents preliminary calculations of the radiative heating of the walls of scramjet combustion chambers. The analysis assumes isothermal, constant property flow fields which are representative of actual combustor flow fields. The fuel is H2 and N2 is taken as inert. Temperature in the combustor is on the order of 2000 to 3000 K and pressure is of the order of 5 atm. The combustion products consist mainly of H2O and OH. These gases are strong radiators in the infrared. Radiation heating can be significant because …

Dynamic Pulse Buckling Of Columns With Viscous Damping, Murli Kadandale

Masters Theses

This is a study of dynamic pulse buckling of columns with viscous damping. The differential equations of motion were obtained using the Bemoulli-Navier hypothesis. The effects of axial and rotary inertia were included in the analysis. The Voigt-Kelvin model for a viscoelastic material is used. The Finite Difference Method was employed to solve the differential equations of motion. First columns without geometrical imperfections were studied, and a correlation between the damping modulus and the more familiar damping ratio was obtained. Then beams with initial geometrical imperfection were studied. A suitable dynamic buckling criterion was defined. It was observed that viscous …

Buckling Analysis And Optimum Design Of Multidirectionally Stiffened Composite Curved Panel, Navin R. R. Jaunky

Mechanical & Aerospace Engineering Theses & Dissertations

Continuous filament grid-stiffened structure is a stiffening concept that combines structural efficiency and damage tolerance. However, buckle resistant design optimization of such structures using a finite element method is expensive and time consuming due to the number of design parameters that can be varied. An analytical optimization procedure which is simple, efficient and supports the preliminary design of grid-stiffened structures for application to combined loading cases is needed.

An analytical model for a general grid-stiffened curved panel is developed using an improved smeared theory with a first-order, shear-deformation theory to account for transverse shear flexibilities and local skin-stiffener interaction effects. …

An Experimental Investigation Of Wall Cooling Effects On Hypersonic Boundary Layer Stability In A Quiet Wind Tunnel, Alan E. Blanchard

Mechanical & Aerospace Engineering Theses & Dissertations

One of the primary reasons for developing quiet tunnels is for the investigation of high-speed boundary-layer stability and transition phenomena without the transition-promoting effects of acoustic radiation from tunnel walls. In this experiment, a flared-cone model under adiabatic- and cooled-wall conditions was placed in a calibrated, 'quiet' Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N=10' criterion used to predict boundary-layer transition in subsonic, transonic, and …

Experimental Investigation Of The Inlet Deflector Configuration Variation In The Flow Field At Mach 1.9, Kyu C. Hwang

Mechanical & Aerospace Engineering Theses & Dissertations

In recent years, active research has been conducted to study the technological feasibility of supersonic laminar flow control on the wing of the High Speed Civil Transport (HSCT). For this study, the F-16XL has been chosen due to its highly swept crank wing planform that closely resembles the HSCT configurations. During flights, it is discovered that the shock wave generated from the aircraft inlet introduces disturbances on the wing where the data acquisition is conducted. The flow field about a supersonic inlet is characterized by a complex three-dimensional pattern of shock waves generated by the geometrical configuration of a deflector …

Dynamic Unstructured Method For Prescribed And Aerodynamically Determined Relative Moving Boundary Problems, Kamakhya Prasad Singh

Mechanical & Aerospace Engineering Theses & Dissertations

A new methodology is developed to simulate unsteady flows about prescribed and aerodynamically determined moving boundary problems. The method couples the fluid dynamics and rigid-body dynamics equations to capture the time-dependent interference between stationary and moving boundaries. The unsteady, compressible, inviscid (Euler) equations are solved on dynamic, unstructured grids by an explicit, finite-volume, upwind method. For efficiency, the grid adaptation is performed within a window around the moving object. The Eulerian equations of the rigid-body dynamics are solved by a Runge-Kutta method in a non-inertial frame of reference. The two-dimensional flow solver is validated by computing the flow past a …

Numerical Investigation Of Shock-Induced Combustion Past Blunt Projectiles, Jagjit K. Ahuja

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study is conducted to simulate shock-induced combustion in premixed hydrogen-air mixtures at various free-stream conditions and parameters. Two-dimensional axisymmetric, reacting viscous flow over blunt projectiles is computed to study shock-induced combustion at Mach 5.11 and Mach 6.46 in hydrogen-air mixture. A seven-species, seven reactions finite rate hydrogen-air chemical reaction mechanism is used combined with a finite-difference, shock-fitting method to solve the complete set of Navier-Stokes and species conservation equations. In this approach, the bow shock represents a boundary of the computational domain and is treated as a discontinuity across which Rankine-Hugoniot conditions are applied. All interior details of …

Effects Of Blowing Ratios On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Fu-Jung Chen

Theses and Dissertations

The effects of transpiration cooling on heat transfer in the throat region of a porous-walled nozzle were investigated. The experiments were performed in the AFIT low speed shock tube fitted with a Mach 2 nozzle. A blowing region was limited to the area from 1.3 cm prior to the throat to 1.2 cm downstream of the throat. The blowing ratios from -0.0002 (suction) to 0.0117 (blowing) of the main stream flow were studied. Heat flux data were taken from both sides of the nozzle. One side was transpiration cooled by secondary air injection through a porous wall, while the other …

Advanced Rover Chassis, Eric Alan Poulson, Collin Lewis, Todd Graves

Undergraduate Honors Capstone Projects

Background:

The six wheeled rover vehicle detailed in this design is intended as an upgrade test bed for the sensor array and autonomous navigation algorithms in use by Utah State University's Center for Self-Organizing and Intelligent Systems (CSOIS). The CSOIS's sensor suite can successfully detect and avoid unnavigable obstacles up to five vehicle lengths in front of the vehicle. The center presently uses a modified RC type chassis and only supports two wheel drive. This chassis was adequate to bring the CSOIS's algorithms to a proof-of-principles state, but in order to place the system in any practical application, a full …

Aerodynamic Design Optimization With Consistently Discrete Sensitivity Derivatives Via The Incremental Iterative Method, Vamshi M. Korivi

Mechanical & Aerospace Engineering Theses & Dissertations

In this study which involves advanced fluid-flow codes, an incremental iterative formulation (also known as the "delta" or "correction" form), together with the well-known spatially split approximate-factorization algorithm, is presented for solving the large, sparse systems of linear equations that are associated with aerodynamic sensitivity analysis. For the smaller two dimensional problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. However, iterative methods are needed for larger two-dimensional and three dimensional applications because direct methods require more computer memory than is currently …

Finite Element Nonlinear Random Response Of Composite Panels Of Arbitrary Shape To Acoustic And Thermal Loads Applied Simultaneously, Roger R. Chen

Mechanical & Aerospace Engineering Theses & Dissertations

The nonlinear random response of composite plates to the simultaneously applied, combined acoustic/thermal loads are investigated in this dissertation. A finite element formulation for the nonlinear random response is developed. The three-node Mindlin plate element with improved transverse shear is extended and employed. The extension includes the development of the thermal geometric matrix, the mass matrix, the first- order and second-order nonlinear stiffness matrices, and the thermal and mechanical load vectors. An innovative solution procedure has been created which is believed to be the first attempt to analyze nonlinear random response of complex composite panels subjected to simultaneous acoustic and …

Fuzzy Logic In Restructurable Flight Control Systems, S. N. Balakrishnan, H. S. Ho

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a fuzzy logic controller (FLC) is proposed for restructurable flight control systems. The role of the FLC is to stabilize the aircraft upon a fault occurrence. The FLC derives pitch/roll/yaw controls from a generic knowledge base characterized by 49 if-then rules. A linearized model representative of a modern jet fighter provides the basis for the numerical simulation. Simulated faults include various degrees of surface loss at the right stabilator, combined with reduced ailerons and rudder control power. The FLC accomplishes the stabilization task under test conditions without any knowledge of the system parameters. The numerical results demonstrate …

Intercomparison Between Commercial Condensation Nucleus Counters And An Alternating Temperature Gradient Cloud Chamber, Darryl J. Alofs, C. K. Lutrus, Donald E. Hagen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Three Commercial CNC Counters (TSI Models 3010, 3022A, and 3025A) Are Compared with an Alternating Temperature Gradient Cloud Chamber (ALGR). Electrically Size Classified Aerosols of Sodium Chloride and Silver Are Used. Diffusional Losses within the ALGR Are Much Larger Than for the TSI Instruments: Therefore the ALGR Concentrations Are Corrected for Internal Diffusional Losses, But the TSI Instruments Are Not. the Particle Size Range Tested is 4–90 Nm. for Sodium Chloride, the TSI Concentrations Agreed Fairly Well with the Corrected ALGR at Larger Sizes, and Were Below the Corrected ALGR at Smaller Sizes. the Electrical Aerosol Classifier (EAC) Setting at …

Towards A More Hands-On, Design-Oriented Course On Mechanisms, Burford Furman

Faculty Research, Scholarly, and Creative Activity

No abstract provided.

On A Method For Obtaining Approximate Solutions To Sturm-Liouville Problems, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A method presented recently to find approximate solutions to a Sturm-Liouville problem is shown to be a special case of a classical weighted residual method. The choice of approximation functions and convergence of the method are also examined. © 1995 American Mathematical Society.

Thermal Contact Conductance Of Ceramic Substrate Junctions, K. C. Chung, H. K. Benson, John W. Sheffield

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

Adaptive Critic Based Neural Networks For Control (Low Order System Applications), S. N. Balakrishnan, Victor Biega

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Dynamic programming is an exact method of determining optimal control for a discretized system. Unfortunately, for nonlinear systems the computations necessary with this method become prohibitive. This study investigates the use of adaptive neural networks that utilize dynamic programming methodology to develop near optimal control laws. First, a one dimensional infinite horizon problem is examined. Problems involving cost functions with final state constraints are considered for one dimensional linear and nonlinear systems. A two dimensional linear problem is also investigated. In addition to these examples, an example of the corrective capabilities of critics is shown. Synthesis of the networks in …

Hamiltonian Based Adaptive Critics For Aircraft Control, S. N. Balakrishnan, Jie Shen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Aircraft designs are becoming more complex in order to either operate more efficiently as in the commercial sector or to push the performance envelopes as in the military sector. An interesting outcome of this scenario is that `control'' has come to play an important role in helping realize these objectives. Increasingly, control is becoming an integral part of an aircraft design rather than an afterthought. More effective and efficient control of an aircraft is certain to lead to improved performance at a lower cost

On The Use Of Students For Developing Engineering Laboratories, Bopaya Bidanda, Richard E. Billo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper describes a unique and innovative approach that solved the dual problem of starting up a new engineering instructional laboratory in a timely manner, and for teaching engineering students advanced skills in Automatic Data Collection. Students enrolled in a special pilot course were used to develop and startup an Automatic Data Collection laboratory. These students were assigned individual Automatic Data Collection technologies of interest and given total responsibility for the successful startup of the laboratory. The organization and structure of the course modeled the typical team oriented project development efforts in industry. Feedback from students showed the course to …

System Modeling And Control Of Smart Structures, Frank J. Kern, Leslie Robert Koval, K. Chandrashekhara, Vittal S. Rao

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents multidisciplinary research and curriculum efforts at the University of Missouri-Rolla in the smart structures area. The primary objective of our project is to integrate research results with curriculum development for the benefit of students in electrical, and mechanical and aerospace engineering and engineering mechanics. The approach to the accomplishment of curriculum objectives is the development of a two-course sequence in the smart structures area with an integrated laboratory. The research portion of the project addresses structural identification and robust control methods for smart structures. A brief summary of the research results and a description of curriculum development …

Improved Finite Element Modeling Of The Turbofan Engine Inlet Radiation Problem, I. Danda Roy, Walter Eversman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Improvements have been made in the finite element model of the acoustic radiated field from a turbofan engine inlet in the presence of a mean flow. The problem of acoustic radiation from a turbofan engine inlet is difficult to model numerically because of the large domain and high frequencies involved. A numerical model with conventional finite elements in the near field and wave envelope elements in the far field has been constructed. By employing an irrotational mean flow assumption, both the mean flow and the acoustic perturbation problem have been posed in an axisymmetric formulation in terms of the velocity …

Vibration Of Point-Supported Rectangular Composite Plates, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A general approach is presented to study the free vibrations of rectangular symmetrically laminated composite plates with point supports by using the Rayleigh-Ritz method and the Lagrange multiplier technique for enforcing the zero displacement constraints at the support locations. Polynomial approximation functions are used, and the constitutive relationships are written in terms of four lamination parameters. With these lamination parameters, the number of design variables is reduced to a minimum, which is useful for design optimization purposes, while all symmetric lay-ups are considered. This paper illustrates how the lamination parameters can be used for optimal design of vibrating plates. Results …

A New Neural Architecture For Homing Missile Guidance, S. N. Balakrishnan, Victor Biega

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We present a new neural architecture which imbeds dynamic programming solutions to solve optimal target-intercept problems. They provide feedback guidance solutions, which are optimal with any initial conditions and time-to-go, for a 2D scenario. The method discussed in this study determines an optimal control law for a system by successively adapting two networks - an action and a critic network. This method determines the control law for an entire range of initial conditions; it simultaneously determines and adapts the neural networks to the optimal control policy for both linear and nonlinear systems. In addition, it is important to know that …

Effects Of Blowing Ratio On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Joseph L. Lenertz

Theses and Dissertations

This experiment analyzed the effects of blowing ratio on heat transfer to the throat region of a porous-walled nozzle, using the AFIT low speed shock tube. Heat flux data were taken from both sides of a two-dimensional Mach 2.0 Re-m=5.2x10⁷ nozzle using thin film resistance thermometers. One side was transpiration-cooled by secondary air injection through a sintered wall, while the other side served as a control. Control results were validated using empirical relations, and cooled side results showed up to a 14% reduction in heat transfer coefficient at blowing ratios of only 0.51%. The linear nature of cooling effectiveness …

An Investigation And Improvement Of Electrorheological (Er) Fluid Technology, Adil F. Dalal

Masters Theses

The purpose of this research was to investigate and overcome the limitations of Electrorheological (ER) fluids and to introduce this advanced technology at WMU. Electrorheological (ER) Fluids are a special class of fluids, which exhibit a reversible, infinitely variable phase transition from a liquid to a solid/semi-plastic state, in the presence of an electric field.

ER fluids can provide a unique solution to the problems of vibration isolation of systems. The applications are currently limited due to the high voltage requirements, electric power related heating and limited research into wear/abrasive characteristics of ER fluids.

A specially designed and constructed "electro-viscosimeter" …

Simulation Of Active Control Of Asymmetric Flows Around Slender Pointed Forebodies, Hazem Sharaf El-Din

Mechanical & Aerospace Engineering Theses & Dissertations

At high angles of attack, the flowfield over slender forebodies becomes asymmetric with substantial side force, which may exceed the available control capability. The unsteady compressible Navier-Stokes equations are used to investigate the effectiveness of different active control methods to alleviate and possibly eliminate the flow asymmetry and the subsequent side force. Although the research work focuses on active control methods, a passive control method has been investigated. The implicit, Roe flux-difference splitting, finite volume scheme is used for the numerical computations. Both locally-conical and three-dimensional solutions of the Navier-Stokes equations are obtained.

The asymmetric flow over five-degree semi-apex angle …

Investigation Of Wall Injectors For Supersonic Mixing Enhancement, Yaacov Haimovitch

Mechanical & Aerospace Engineering Theses & Dissertations

A comparative study of the interaction between wall mounted swept-ramp injectors and injector nozzle shape has been conducted in a constant area duct to explore techniques to enhance mixing in scramjet combustors. The scramjet combustors are currently being developed for propulsion systems applications on the envisioned hypersonic vehicles. Short combustor residence time, a requirement for fuel injection parallel to the main flow in the combustor, and an overall strong sensitivity of the vehicle performance to the propulsion system motivated the investigation. The swept-ramp injector investigated in this study produces vortex shedding and local separation downstream of the injector's nozzle exit, …

Three-Dimensional Aerodynamic Shape Optimization Using Discrete Sensitivity Analysis, Gregory Wayne Burgreen

Mechanical & Aerospace Engineering Theses & Dissertations

An aerodynamic shape optimization procedure based on discrete sensitivity analysis is extended to treat three-dimensional geometries. The function of sensitivity analysis is to directly couple computational fluid dynamics (CFD) with numerical optimization techniques, which facilitates the construction of efficient direct-design methods. The development of a practical three-dimensional design procedures entails many challenges, such as: (1) the demand for significant efficiency improvements over current design methods; (2) a general and flexible three-dimensional surface representation; and (3) the efficient solution of very large systems of linear algebraic equations. It is demonstrated that each of these challenges is overcome by: (1) employing fully …