Publications by Type: Conference Paper

2014
C. E. Tinney and Baars, W. J., “

Where are the nonlinearities in jet noise?

,” in 168th Meeting of the Acoustical Society of America, Indianapolis, 2014, vol. 136:2101. Publisher's VersionAbstract
For some time now it has been theorized that spatially evolving instability waves in the irrotational near-field of jet flows couple both linearly and nonlinearly to generate far-field sound [Sandham and Salgado, Philos. Trans. R. Soc. Am. 366 (2008); Suponitsky, J. Fluid Mech. 658 (2010)]. An exhaustive effort at The University of Texas of Austin was initiated in 2008 to better understand this phenomenon, which included the development of a unique analysis technique for quantifying their coherence [Baars et al., AIAA Paper 2010–1292 (2010); Baars and Tinney, Phys. Fluids 26, 055112 (2014)]. Simulated data have shown this technique to be effective, albeit, insurmountable failures arise when exercised on real laboratory measurements. The question that we seek to address is how might jet flows manifest nonlinearities? Both subsonic and supersonic jet flows are considered with simulated and measured data sets encompassing near-field and far-field pressure signals. The focus then turns to considering nonlinearities in the form of cumulative distortions, and the conditions required for them to be realized in a laboratory scale facility [Baars, et al., J. Fluid Mech. 749 (2014)].
2013
T. J. Watt, Yasuda, S., Ichitani, K., Takata, K., Carpenter, A., Jodlowski, J., and Taleff, E. M., “The Effect of Magnesium Content on Microstructure Evolution during Hot Deformation of Aluminum Alloys,” in Proceedings of the 2013 TMS Annual Meeting, San Antonio, TX, 2013, pp. 499–503. Publisher's Version
A. J. Carpenter, Carter, J. T., Louis G. Hector, J., and Taleff, E. M., “Gas-pressure Bulge Forming of Mg AZ31Sheet 450°C,” in Proceedings of the 2013 TMS Annual Meeting, San Antonio, TX, 2013, pp. 139–144. Publisher's Version
M. A. Morovat, Engelhardt, M. D., Helwig, T. A., and Taleff, E. M., “Influence of Creep on the Stability of Steel Columns Subjected to Fire,” in Proceedings, Annual Stability Conference, St. Louis, MO, 2013. Publisher's Version
D. R. Bell, Xia, Z., and Ren, P., “Multiscale modeling of RNA 3D structures,” in Biomedical Sciences and Engineering Conference (BSEC), 2013, 2013, pp. 1–4.
R. Rojo, Tinney, C. E., and Baars, W. J., “Near-field/far-field study of the end-effects regime produced by large area ratio nozzles,” in 166th Meeting of the Acoustical Society of America, San Fransisco, CA, 2013, vol. 134:5, Pt 2.
2012
J. Lee, Morovat, A., Engelhardt, M., and Taleff, E., “Creep Behavior of ASTM A992 Steel at Elevated Temperatures,” in Proceedings, 7th International Conference on Structures in Fire (SiF), Zurich, Switzerland, 2012. Publisher's Version
P. A. Sherek, Carpenter, A. J., Louis G. Hector, J., Krajewski, P. E., Carter, J. T., Lasceski, J., and Taleff, E. M., “The Effects of Strain and Stress Sate in Hot Forming of Mg AZ31 Sheet,” in Magnesium Technology 2012, TMS Annual Meeting, Orlando, FL, 2012. Publisher's VersionAbstract
Wrought magnesium alloys, such as AZ31 sheet, are of considerable interest for light-weighting of vehicle structural components. The poor room-temperature ductility of AZ31 sheet has been a hindrance to forming the complex part shapes necessary for practical applications. However, the outstanding formability of AZ31 sheet at elevated temperature provides an opportunity to overcome that problem. Complex demonstration components have already been produced at 450°C using gas-pressure forming. Accurate simulations of such hot, gas-pressure forming will be required for the design and optimization exercises necessary if this technology is to be implemented commercially. We report on experiments and simulations used to construct the accurate material constitutive models necessary for finite-element-method simulations. In particular, the effects of strain and stress state on plastic deformation of AZ31 sheet at 450°C are considered in material constitutive model development. Material models are validated against data from simple forming experiments.
A. Morovat, Engelhardt, M., Helwig, T., and Taleff, E., “High-Temperature Creep Buckling Phenomenon of Steel Columns Subjected to Fire,” in Proceedings, 7th International Conference on Structures in Fire (SiF), Zurich, Switzerland, 2012. Publisher's Version
M. Morovat, Engelhardt, M., Helwig, T., and Taleff, E., “Investigation of Time-Dependent Buckling of Steel Columns Exposed to Fire Temperatures,” 2012, pp. 2095–2106. Publisher's VersionAbstract
One of the critical factors affecting the strength of steel columns at elevated temperatures is the influence of material creep. Under fire conditions, steel columns can exhibit creep buckling, a phenomenon in which the critical buckling load for a column depends not only on slenderness and temperature, but also on the duration of applied load. The phenomenon of time-dependent buckling can have a significant impact on the safety of steel columns subjected to fire. This phenomenon has received relatively little research attention, and is not currently explicitly considered in code-based design formulas for columns at elevated temperatures, such as those in the Eurocode 3 or those in the AISC Specification. This paper presents some results of on-going research, which aims at developing analytical, computational and experimental predictions of the phenomenon of creep buckling in steel columns subjected to fire. Analytical solutions using the concept of time-dependent tangent modulus are developed to model time-dependent buckling behavior of steel columns at elevated temperatures. Results from computational creep buckling studies using Abaqus are also presented, and compared with analytical predictions. Material creep data on ASTM A992 steel is also presented in the paper and compared to existing creep models for structural steel at high temperatures. Both analytical and computational methods utilize material creep models for structural steel developed by Harmathy, by Fields and Fields, and by the authors. Predictions from this study are also compared against those from Eurocode 3 and the AISC Specification. Results of this work show that neglecting creep effects can lead to erroneous and potentially unsafe predictions of the strength of steel columns subjected to fire.
J. T. Lee, Carpenter, A. J., Jodlowski, J. P., and Taleff, E. M., “Predicting Hot Deformation of AA5182 Sheet,” in In Proceedings of the 13th International Conference on Aluminum Alloys (ICAA-13), Pittsburgh, PA, 2012. Publisher's Version
2011
C. N. Dolder, Villanueva, M. A., Haberman, M. R., and Tinney, C. E., “Application of boundary layer suction for reducing hydrophone sensing noise,” in 162nd Meeting of the Acoustical Society of America, San Diego, CA, 2011, vol. 130:4, Pt 2.
M. Morovat, Engelhardt, M., Helwig, T., and Taleff, E., “Creep Buckling of Steel Columns Subjected to Fire,” in In Proceedings of the 35th International Symposium on Bridge and Structural Engineering, London, England, 2011. Publisher's VersionAbstract
One of the critical factors affecting the strength of steel columns at elevated temperatures is the influence of material creep. Under fire conditions, steel columns can exhibit creep buckling, a phenomenon in which the critical buckling load for a column depends not only on slenderness and temperature, but also on the duration of applied load. Although material creep and consequently the phenomenon of creep buckling can significantly impact the safety of steel columns subjected to fire, they have received relatively little research attention, and are not currently explicitly considered in code-based design formula for columns at elevated temperatures, such as those in the Eurocode 3 or in the AISC Specification. This paper will propose a preliminary methodology to study the phenomenon of creep buckling in steel columns subjected to fire. Preliminary analytical solutions are presented, and compared with computational predictions for creep buckling. The analytical and computational results clearly indicate that accurate knowledge of material creep is essential in studying creep buckling phenomenon at elevated temperatures. In addition, the results show that neglecting creep effects can lead to erroneous and potentially unsafe predictions of the strength of steel columns subjected to fire.
H. Daigle, Bangs, N., and Dugan, B., “Transient pressures, hydraulic fracturing, and gas migration at southern Hydrate Ridge: Geophysical observations and flow modeling,” in 7th International Conference on Gas Hydrates, Edinburgh, UK, 2011.Abstract
Two collocated seismic surveys acquired 8 years apart at Hydrate Ridge offshore Oregon, USA, show migration of free gas in a permeable conduit, Horizon A, feeding an active methane hydrate province. They also reveal transients in active gas venting to the water column. We propose that episodic gas migration and pressure fluctuations in the reservoir underlying the regional hydrate stability zone (RHSZ) at southern Hydrate Ridge influence methane supply to the RHSZ and are linked with periodic fracturing and release of methane into the water column by complex feedback processes. We model the effect of pore pressure variations within the deep methane source on fracturing behavior with a 1D model coupling multiphase flow, hydrate accumulation, and pore pressure buildup. Fractures open when the pore pressure exceeds the fracture criterion, which we assume is the vertical effective stress assuming hydrostatic conditions. We define a rate of pressure increase, which determines the time required to reach the fracture criterion, and a maximum pressure based on estimates of the reservoir size. Once fractures open, gas flows through the fractures until the maximum reservoir pressure is reached, after which the gas pressure is depleted quickly because the high gas pressure drives rapid gas flux through the fracture system. This results in gas venting at the seafloor and accumulation of hydrate in the fracture system. If the amplitude of pressure oscillation is near the vertical effective stress in Horizon A (~0.87 MPa) and the time for pressure increase is on the order of years, the gas pressure will meet the fracture criterion on a time scale of months to a few years. The high gas pressure is then depleted over a time scale of a few months. Thus we conclude that gas migration pathways at southern Hydrate Ridge may evolve on a time scale of months to years. This provides important constraints on the time scale of transient effects on the methane hydrate system at southern Hydrate Ridge, and illustrates how pore pressure pulses affect fluid flow and fracturing behavior in active methane hydrate provinces.
PDF icon daigle_etal_icgh_paper.pdf
2010
E. M. Taleff, Takata, K., and Ichitani, K., “Hot and Warm Deformation of AA5182 Sheet Materials: Ductility and Microstructure Evolution,” in Proceedings of the 12th International Conference on Aluminum Alloys, September 5–9, 2010, 2010, pp. 1231–1236.Abstract
Not available.
E. Bakolas and Tsiotras, P., “Minimum-Time Paths for a Light Aircraft in the Presence of Regionally-Varying Strong Winds,” in AIAA Infotech ’’AT’’ Aerospace, Atlanta, Georgia, 2010.
C. N. Dolder, Haberman, M. R., and Tinney, C. E., “Turbulent Boundary Layers over Receiver Arrays,” in 159th Acoustical Society of America Meeting, NOISE-CON, Baltimore, MD, 2010, vol. 127:3, Pt 2.
2009
Y. Shi, Jiao, D., Schnieders, M. J., and Ren, P., “Engineering in Medicine and Biology Society, 2009. EMBC 2009,” in Annual International Conference of the IEEE, 2009, pp. 2328–2331.
Y. Shi, Jiao, D., Schnieders, M. J., and Ren, P., “Trypsin-ligand binding free energy calculation with AMOEBA,” in Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE, 2009, pp. 2328–2331.
2007
C. E. Tinney, Bonnet, J. - P., and Delville, J., “Stochastic estimation: structure eduction techniques for turbulent flows and other dynamical systems,” in Schloss Dagstuhl Seminar–07121: Experimental fluid mechanics, computer vision and pattern recognition, Wadern, Germany, 2007.

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