Christine M. Hrenya

Education

BS, Chemical Engineering, The Ohio State University (1991)
PhD, Chemical Engineering, Carnegie Mellon University (1996)

Honors

• APS Fellow (2021)
• AIChE Thomas Baron Award in Fluid-Particle Systems (2020)
• Chair, AIChE Annual Meeting (2016)
• Associate Editor, AIChE Journal (2015 – present)
• AIChE Lectureship Award in Fluidization (2014)
• AIChE Particle Technology Forum Service Award (2014)
• Editor, Aerosol Science and Technology (2013-2015)
• Boulder Faculty Assembly Excellence in Teaching Award (2013)
• University of Colorado Outstanding Graduate Teaching Faculty in 
    Chemical Engineering (2012-2013 and 2009-2010)
• College of Engineering Hutchinson Memorial Teaching Awards (2010)
• AIChE Particle Technology Forum Best Paper Award (2010)
• University of Colorado Emerging Leaders Program Fellow (2009-2010)
• Editor, Granular Matter (2008 – present)
• Provost's Faculty Achievement Award (2008)
• University of Colorado Dean’s Faculty Fellowship (2008-2009)
• ACS PROGRESS/Dreyfus Lectureship Award (2006)
• Chair, Gordon Conference on Granular and Granular-Fluid Flow (2006)
• NSF POWRE Award (1999)
• University of Colorado Junior Faculty Development Award (1999)
• AIChE Particle Technology Forum Award for Best Ph.D. in Particle Technology (1997)

Selected Publications

• Mishra, I., M. J. Molnar, M. Y. Hwang, A. Shetty, and C. M. Hrenya, “Experimental validation of the extraction of a particle-particle cohesion model (square-force) from simple bulk measurements (defluidization in a rheometer),” Chemical Engineering Journal 259, 117782, 12 pages (2022).
• LaMarche, W. C. Q., P. Liu, K. M. Kellogg, A. M. Lattanzi and C. M. Hrenya, “Toward general regime maps for cohesive-particle flows: Force vs. energy-based descriptions and relevant dimensionless groups,” AIChE Journal, 67, e17337, 16 pages (2021; Editor’s Choice Article).
• Lattanzi, A. M., X. Yin and C. M. Hrenya, “Heat and Momentum Transfer to a Particle in a Laminar Boundary Layer,” Journal of Fluid Mechanics 889, A6, 40 pages (2020).
• P. Liu and C. M. Hrenya, “Cluster-induced Deagglomeration in Dilute Gravity-driven Gas-solid Flows of Cohesive Grains,” Physical Review Letters 121, art. no. 238001, 7 pages (2018).
• Kellogg, K. M., P. Liu, C. Q. LaMarche, and C. M. Hrenya, “Continuum Theory for Rapid, Cohesive-Particle Flows: General Balance Equations and Discrete-element-method-based Closure of Cohesion-specific Quantities,” Journal of Fluid Mechanics 832, 345-382 (2017).
• Fullmer, W. D., G. Liu, X. Yin and C. M. Hrenya, “Clustering instabilities in sedimenting fluid-solid systems: Critical assessment of kinetic-theory-based predictions using DNS data,” Journal of Fluid Mechanics 823, 433-469 (2017).
• Fullmer, W. D. and C. M. Hrenya, “The clustering instability in rapid granular and gas-solid flows,” Annual Review of Fluid Mechanics 49, 485-510 (2017).
• Morris, A. B., Z. Ma, S. Pannala, and C. M. Hrenya, “Simulations of heat transfer to solid particles flowing through an array of heated tubes,” Solar Energy 130, 101-115 (2016).   
• LaMarche, C. Q., P. Liu, K. M. Kellogg, A. W. Weimer, "A system-size independent validation of CFD-DEM for non-cohesive particles," AIChE Journal (Letter) 61, 4051-4058 (2015).
• Mitrano, P. P., J. R. Zenk, S. Benyahia, J. E. Galvin, S. R. Dahl, and C. M. Hrenya, “Kinetic-theory predictions of clustering instabilities in granular flows: beyond the small-Knudsen-number regime,” Journal of Fluid Mechanics, 738, R2, 12 pages (2014); this work was highlighted in Focus on Fluids feature (Journal of Fluid Mechanics, 742, 1-4, 2014).
• Mitrano, P. P., S. R. Dahl, A. M. Hilger, C. J. Ewasko, and C. M. Hrenya, “Dual role of friction in granular flows:  Attenuation vs. enhancement of instabilities,” Journal of Fluid Mechanics, 729, 484-495 (2013).
• Yin, X., J. R. Zenk, P. P. Mitrano, and C. M. Hrenya, “Impact of collisional vs. viscous dissipation on flow instabilities in gas-solid systems,” Journal of Fluid Mechanics, 727, R2, 12 pages (2013).
• Chew, J.W., D. M. Parker, and C. M. Hrenya, “Elutriation and species segregation characteristics of polydisperse mixtures of Group B particles in a dilute CFB riser,” AIChE Journal, 59, 84-95 (2013).
• Garzó, V., S. Tenneti, S. Subramaniam, and C. M. Hrenya, “Enskog kinetic theory for monodisperse gas-solid flows,” Journal of Fluid Mechanics, 712, 129-168 (2012).
• Donahue, C. M., W. M. Brewer, R. H. Davis, and C. M. Hrenya, “Agglomeration and de-agglomeration of rotating wet doublets,” Journal of Fluid Mechanics, 708, 128-148 (2012).
• Chew, J. W. and C. M. Hrenya, “Link between bubbling and segregation patterns in gas-fluidized beds with continuous size distributions,” AIChE Journal, 57, 3003-3011 (2011).
• Donahue, C. M., C. M. Hrenya, and R. H. Davis, “Stokes’s cradle: Newton’s cradle with liquid coating,” Physical Review Letters, 105, art. no. 034501, 4 pages (2010); this work was featured in Nature (466, 22 July 2010, p. 417) and the New Scientist (2768, 8 July 2010).
• Donahue, C. M., C. M. Hrenya, R. H. Davis, K. J. Nakagawa, A. P. Zelinskaya, and G. G. Joseph, “Stokes’ cradle: normal three-body collisions between wetted particles,” Journal of Fluid Mechanics, 650, 479-504 (2010).

Research Interests

Granular Flows, Gas-Particle Fluidization, Aerosol Dynamics
Flows involving solid particles are used extensively in the chemical process industries, including areas such as petrochemicals, pollution control, powder technology, coal combustion, and pharmaceuticals. However, since the fundamental flow behavior of such systems is not well understood, the design and operation of these systems are often based on experience rather than on scientific principles. As a result, processes employing particulate flows often operate below design capacity and exhibit undesired flow behavior. The overall focus of this research program is to further the physical understanding of fluidized systems, and to incorporate this knowledge into practical mathematical models that can be used for process design, scale-up, and optimization.

Granular Flows
The term “granular flows” refers to a system of solid particles in which the flow behavior is dictated solely by particle-particle and particle-wall interactions (i.e., the role of the interstitial fluid is negligible). Examples include avalanches, flow of sand in an hourglass, planetary-ring dynamics, and pharmaceutical handling. Granular flows exhibit complex flow behavior, such as particle clustering and size segregation. The goal of this work is to use discrete-particle or “molecular-dynamic” simulations of granular systems to gain insight into these phenomena, and to use this information to develop improved constitutive theories.

Gas-Particle Fluidization
Unlike granular flows, gas-solid flows are systems in which the role of the “carrier” fluid cannot be ignored. Although gas-solid systems are characterized by the same mechanical interactions that are present in granular flows (e.g., collisions between two particles), the physical nature of the gas-solid interaction must also be considered (e.g., drag force). Research efforts in this area are focused on developing fundamental, continuum models for practical systems, such as those characterized by a nonuniform distribution of particle sizes. Applications of this work include coal combustion for power generation, fluid catalytic cracking, and pneumatic conveying of grains and ores.

Aerosol Dynamics
The aerosol systems being considered are also composed of a gas phase and solid particles. However, due to the extremely small mass of the particulates (often submicron), the physical interactions that dictate the flow behavior of these systems are significantly different than those of the fluidized systems described above. In particular, the motion of an individual particle is significantly affected by collisions with gaseous molecules (i.e., Brownian motion). Current projects in this field are targeted at improving the understanding of thermophoretic deposition, which refers to the tendency of particles suspended in a relatively hot fluid to deposit on cool surfaces. A physical model that accurately describes this phenomenon will be useful for advanced material synthesis and pollution control.