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Mechanical Engineering

DAVID DYER, DEPARTMENT CHAIR

COMBUSTION LABORATORY  

The Combustion Laboratory is investigating particle formation and dynamics in flames. Although the emission of combustion-generated particles into the atmosphere affects the environment negatively, the presence of particles in flames benefits combustion. They radiate heat, contributing to thermal energy transfer from hot combustion gases to heat exchanger surfaces.

Research on factors that govern particle growth will help predict whether a particle will be oxidized in a flame or be released into the atmosphere. Research on predicting radiative properties of combustion-generated particles will help assess the particles' contributions to overall heat release from a flame, and will help determine the effect on heat transfer from particle fouling of heat exchanger surfaces.

ELECTRONICS COOLING LABORATORY

The Electronics Cooling Laboratory research focuses on the cooling of microelectronic components, particularly on the pool boiling characteristics of micro-configured cavities etched into silicon heat sinks. A novel technique has been developed to create reentrant cavities in silicon that are excellent vapor traps. Research also covers interaction of multiple heat source-sink combinations, two-phase heat transfer in vertical channels, and enhanced nucleate pool boiling. Through these experiments, which are done in ozone-safe refrigerating fluids, effective methods will be developed for cooling the next generation of liquid-immersion cooled multichip microelectronic packages.

The laboratory has pool boiling rigs, advanced temperature sensors, thin-film heat sources, power supplies, a distillation unit, vacuum pumps, and a data acquisition system.

EXPERIMENTAL AND COMPUTATIONAL MECHANICS LABORATORY

Current research areas in the Experimental and Computational Mechanics Laboratory include electronic packaging, fracture mechanics, and mechanics of wood and paper.

This solid mechanics research facility includes rooms for coherent optical techniques, two general-purpose areas, a Sun Workstation subnet, and a fully equipped darkroom. Experimental stress analysis techniques are used with conventional and semiconductor strain gauges, computerizeddata acquisition, brittle coatings, photoelasticity and photoelastic coatings, holographic and speckle interferometry, shearing interferometry and coherent gradient sensing, moir? and moir? interferometry, and high-speed photography.

Equipment includes argon ion, helium neon, and pulse ruby lasers, high-speed and other cameras, a thermoplastic holographic recording system, vibration isolation tables, digital image processing system, computerized data-acquisition system, environmental chambers, PGC temperature/humidity control unit, transmission and reflection polariscopes, and optical components.

FLUID MECHANICS LABORATORY

The Fluid Mechanics Research Laboratory does fundamental and applied experimental studies of complex fluid flow problems. State-of-the-art laser-based flow diagnostic tools, including a laser Doppler velocimeter, laser sheet visualization unit and digital image processing hardware and software are used to explain spatially-resolved velocity field, turbulence data and qualitative flow-pattern information. Computational fluid dynamics codes are used to verify and complement the research.

Current experimental and computational projects deal with transport phenomena in materials processing. For example, experimental test-sections are used to study the flow of liquid steel in a continuous caster mold and liquid aluminum in a tundish. Projects focus onpredicting and measuring complex liquid metal flow fields and on observing the effects of geometrical and process conditions.

The GPS AND VEHICLE DYNAMICS LABORATORY

The GPS Vehicle Dynamics Laboratory focuses on the control and navigation of vehicles using GPS in conjunction with other sensors, such as Inertial Navigation System (INS) sensors. The laboratory has several research thrusts including: sensor fusion/integration, on-line system identification, adaptive and robust control algorithms, and vehicle state and parameter estimation. These research thrusts are focused towards vehicle dynamics and transportation, including heavy trucks, passenger cars, off-road vehicles, as well as autonomous and unmanned vehicles. The laboratory consists of various GPS receivers (including a software GPS receiver), Inertial Measurement Units (IMUs), an instrumented Chevrolet Blazer, an automatically steered John Deere tractor, and access to an iRobot ATRV. Current projects include ultra-tight GPS/INS coupling (sponsored by the Army), study of vehicle rollover propensity, improved steering control of GPS guided farm tractors (sponsored by John Deere), vehicle and driver monitoring, and navigation and control of unmanned ground vehicles (UGVs).

As part of a current project with U.S. Army Aviation and Missile Command, a GPS receiver capable of performing ultra-tight GPS/INS integration has been acquired. Ultra-tight GPS/INS coupling provides improved anti-jamming resistance, improved satellite tracking, as well as allows for immediate GPS signal reacquisition after short GPS outages. This GPS unit could be valuable in investigating GPS navigation in cluttered environments, where GPS satellite signals become unavailable and available for intermittent periods. The GPS Vehicle Dynamics Laboratory also has access to the National Center for Asphalt Testing (NCAT) test track (http://www.pavetrack.com/). Validation of navigation and parameter and state estimation algorithms can be performed using the vehicles on the NCAT track. GPS and inertial sensors can be mounted on the semi-trucks or our own test vehicles to validate proposed estimation and control algorithms. Additionally, errors such as jamming, multi-path, and other sensor errors can be simulated to test the algorithms ability to reject these disturbances and continue to provide an accurate navigation solution.

For more information please visit: gavlab.auburn.edu

INTERFACIAL MECHANICS AND NON-NEWTONIAN FLUID MECHANICS LABORATORY

The theoretical and experimental research done in the Interfacial Mechanics and Non-Newtonian Fluid Mechanics Laboratory aims at practical applications in industry such as energy savings in the pumping of non-Newtonian liquids.

Research is under way on the interface behavior and stability between immiscible layers subject to thermal gradients. In non-Newtonian fluid mechanics, the mechanics of the interface between layers of viscoelastic fluids is being studied to identify general trends and patterns in viscoelastic liquids with different constitutive structures and to develop general stability criteria. The natural convection of viscoelastic liquids, including buoyancy-driven convection, is being studied to determine the effects of fluid elasticity and shear-dependent viscosity on flow conditions, particularly on the local Nusselt number. Also being studied are the effects of flow rate increase on viscoelastic liquids when driven by a pulsating gradient or vibrating boundaries.

MACHINE SIMULATION AND ANALYSIS LABORATORY

The Machine Simulation and Analysis Laboratory focuses on the dynamics and control of industrial mechanisms and machines, and on driving mechanisms at low and high speeds to measure their dynamic responses.

Slider-crank and four-bar mechanisms have been studied. In a recent experiment, a flexible-rod slider-crank mechanism, built in our machine shop, was driven at high speeds. Flexible-rod response, stresses, and strains were extracted from the data. Attached accelerometers sensed vibrations transmitted to its base. Other research includes studies of vibrating beams, and film digitization for correlating experimental and analytical motions.

Methods to control mechanism vibration are under investigation. The slider-crank rod is being layered with piezofilm and piezoceramic that can apply controlling forces on command from a voltage signal generated by a computer-derived control algorithm.

Researchers use the Sun network, mechanical systems simulation and control packages (such as ADAMS, DADS, MATLAB), and numerical and finite element codes.

NONLINEAR SYSTEMS RESEARCH LABORATORY

Researchers in the Nonlinear Systems Research Laboratory are developing techniques to study the behavior of nonlinear dynamical systems with periodically varying parameters--bifurcation analysis, response calculations and control system design. Several types of bifurcations (transcritical, flip, Hopf) are studied through an application of the Liapunov-Floquet transformation and time-dependent normal form theory. For critical cases of bifurcations, system equations are simplified withcenter manifold theory. This technique, which is virtually free from small parameter limitations (unlike averaging or perturbation methods), and the Liapunov direct approach are also used to study associated control problems. Helicopter blades, turbomachines, rotor-bearing systems and structural elements subjected to in-plane loads are analyzed with these techniques. Future control algorithms will be tested in the Multibody Modeling, Verification and Controls Laboratory.

Equipment includes Sun Workstations and PCs, which are used to study nonlinear dynamics and control problems, and software, including IMSL, Macsyma, AUTO, Dynamical and Phaser.

SOUND AND VIBRATION LABORATORY

Researchers in the Sound and Vibration Laboratory are using the sound intensity technique to measure sound power of machines and to evaluate transmission loss of structures. Other research includes measurement of vibration damping of composite materials, and nondestructive evaluation of composite materials using acoustic and vibration techniques, acoustic scattering and radiation from structures, and active vibration control.

The laboratory has reverberation chambers and an anechoic chamber. The reverberation chambers, which are vibration-isolated from each other and the ground, can be used for measuring transmission loss of structures.

Experiments are done with state-of-the-art equipment for measuring and analyzing sound and vibration signals, including a real-timeanalyzer for measuring sound intensity and power, and reverberation time; FFT dual-channel analyzers; a computer system for on-line data management; and modal analysis software.

STRUCTURAL DYNAMICS LABORATORY

Research in the Structural Dynamics Laboratory deals with vibration and control of rotating machinery. Study areas include the impact of disk and blade vibrations and of bearing and seal properties on rotordynamical behavior, and the control strategies for vibration suppression in rotating machinery.

Test facilities include bench-top rotordynamics rigs, a rotordynamics test kit, and a rotorcraft vibration rig. Radial magnetic bearings and a thrust bearing are under construction. Data-acquisition devices are used for very high-quality and versatile data acquisition of dynamic systems--a dual-channel frequency analyzer for recording and analyzing data, and a personal computer with a high-speed data-acquisition card and data-analysis capabilities for reading data.

THERMAL RADIATION MEASUREMENTS LABORATORY

The Thermal Radiation Measurements Laboratory measures spatial, directional, and spectral distributions of radiation intensity to quantify radiation surface and bulk material properties, to determine radiation arriving at or leaving a surface, and to measure intensity distributions in radiatively participating media (for comparison tonumerical/analytical calculations).

Equipment for basic research and applied studies of radiation heat transfer includes: gold-coated parabolic mirrors for concentrating radiation; a monochromator with gratings and prefilters for selecting a single wavelength component; pyroelectric radiation detection devices; a radiometer locked in to a noise-filtering beam chopper; a radiating cavity blackbody source for calibration; and positioning and heating devices for sample surfaces and materials.

THERMAL SYSTEMS LABORATOR

The Thermal Systems Laboratory does graduate- and undergraduate-level experimental/analytical work. Research includes ways to improve energy use by boilers, chillers, fans, pumps, air compressors, engines, cooling towers, heat exchangers, refrigeration equipment, ovens, furnaces in industrial/commercial facilities.

Recent graduate-level research deals with turbulators for radiation heat transfer in boilers, fluid jet cleaning of contaminated surfaces, waste heat recovery in electric generating power plants, RO filters in a novel desalination system, and microwave heating for curing of advanced fiber composites.

Instruments include digital, multichannel thermometers, electronic gas analyzers; electronic instruments to measure velocity, relative humidity, surface temperature, and light; water quality chemical test kits; chemical tests for gases; flowmeters; power analyzers; anddifferential pressure gauges.

For more information: Thermal Systems

TURBOMACHINERY LABORATORY  

The Turbomachinery Laboratory is doing rim-sealing experiments to confirm the adequacy of a prototype seal design for a gas turbine plant's low-pressure turbo-expander. Other research includes improving cooling methods for turbomachinery components to ensure reliable operation at elevated temperatures in advanced gas turbine cycles.

Methods include hot-wire anemometry, laser-sheet flow visualization, and 3-D flow measurement. Equipment includes turbine flowmeters, pressure sensors, blowers, a turbomachinery simulation rig, and a data-acquisition system.