@article{pillai_sponsel_stapelmann_bolotnov_2022, title={Direct Numerical Simulation of Bubble Formation Through a Submerged "Flute" With Experimental Validation}, volume={144}, ISSN={["1528-901X"]}, DOI={10.1115/1.4052051}, abstractNote={Abstract
               Direct numerical simulation (DNS) is often used to uncover and highlight physical phenomena that are not properly resolved using other computational fluid dynamics methods due to shortcuts taken in the latter to cheapen computational cost. In this work, we use DNS along with interface tracking to take an in-depth look at bubble formation, departure, and ascent through water. To form the bubbles, air is injected through a novel orifice geometry not unlike that of a flute submerged underwater, which introduces phenomena that are not typically brought to light in conventional orifice studies. For example, our single-phase simulations show a significant leaning effect, wherein pressure accumulating at the trailing nozzle edges leads to asymmetric discharge through the nozzle hole and an upward bias in the flow in the rest of the pipe. In our two-phase simulations, this effect is masked by the surface tension of the bubble sitting on the nozzle, but it can still be seen following departure events. After bubble departure, we observe the bubbles converge toward an ellipsoidal shape, which has been validated by experiments. As the bubbles rise, we note that local variations in the vertical velocity cause the bubble edges to flap slightly, oscillating between relatively low and high velocities at the edges.}, number={2}, journal={JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME}, author={Pillai, Naveen and Sponsel, Nicholas L. and Stapelmann, Katharina and Bolotnov, Igor A.}, year={2022}, month={Feb} }
 @article{trinh_mekonnen_2018, title={Hydrophobic esterification of cellulose nanocrystals for epoxy reinforcement}, volume={155}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2018.08.076}, abstractNote={The reinforcing effects of native and modified cellulose nanocrystal (CNC) materials on thermosetting epoxies are investigated. CNC modification is conducted by grafting an activated medium chain fatty acid to substitute the hydroxyl functional group. The level and effect of CNC modification are evaluated using Fourier Transform Infrared (FTIR), elemental analysis (EA), thermal analysis, contact angle measurements, and solvent dispersibility studies. The EA shows that CNCs with a degree of substitution (DS) of 0.2, 0.8 and 2.4 is obtained depending on the concentration of the catalyst and reactant used in the process. The native and modified CNCs are then incorporated into epoxy resin via an in situ polymerization. Dynamic mechanical analysis, and stress – strain studies showed that the lightly modified CNCs (DS 0.2 and DS 0.8) have an impressive reinforcing effect. CNC with DS 0.2 at 5% loading resulted in a 77% and 44% improvement in the tensile strength and modulus of the baseline epoxy matrix, respectively indicating significant reinforcement. Such materials can be useful in structural composites, printed circuit boards, and adhesive applications. An improvement in the dispersion and an enhanced interfacial adhesion between the modified CNC and the epoxy matrix is proposed for the observed reinforcement. A higher degree of fatty acid grafting onto the CNC resulted in a hydrophobic material, which reduced the water uptake of the epoxy nanocomposites.}, journal={POLYMER}, author={Trinh, Binh Minh and Mekonnen, Tizazu}, year={2018}, month={Oct}, pages={64–74} }