Intercampus Marine Science Graduate Program

For Zoom passcode email Callie Rumbut: c.rumbut@umassd.edu

Atlantic Meridional Overturning Circulation (AMOC) collapse models have become popular and some have recently claimed that the AMOC is close to a tipping point where it will transition from a thermal mode to a reverse haline mode. I argue that this is impossible and that such models suffer from gross misrepresentations of the global water cycle, energetically unfeasible exaggerations of the small Greenland melt rate, neglect of the diapycnal mixing that drives the MOC, and neglect of the strong salinification underway in the Subtropics. The North Atlantic, with its evaporative Mediterranean and Caribbean marginal seas, exports large volumes of freshwater to the Pacific across Central America, a transport that is found to increase in climate models. The Clausius-Clapeyron relation guarantees that low latitude water cycles are always stronger than high latitude cycles and low latitude salinification explains the increasing salinities observed in the North Atlantic. The AMOC may weaken slightly due to the decreased meridional temperature gradient arising from high latitude warming, but not due to freshening. With the present arrangement of continents, the North Atlantic will remain the saltiest ocean basin, there will always be an AMOC and Europe will continue to experience accelerated warming, not catastrophic cooling.

SMAST E 101-102 and via Zoom

Date: Monday, February 10, 2025 Time: 3pm Topic: Exploring Rheological Behavior and Interfacial Properties in Solid Polymer Electrolytes for Supercapacitor Location: SENG 110 Abstract: Solid polymer electrolytes (SPEs) and their composites are promising candidates for energy storage applications, including flexible and structural supercapacitors and batteries, due to their safety, stability, and mechanical robustness. However, their limited processability and low interfacial capacitance compared to liquid electrolytes present significant challenges for large-scale implementation. This study aims to address these limitations by investigating the rheological behavior, interfacial properties in SPEs. The processability, of SPE composites with various filers and salt which can be evaluated through rheology tests. This study evaluates how these factors influence the flow and deformation of SPEs under various shear rates and temperatures near and above their melting points. The insights gained will improve the processability of SPEs, enabling their integration into scalable manufacturing techniques like thermal drawing and injection molding. The interfacial capacitance of SPE is less understood in the literature. The mechanisms leading to lower capacitance with SPE compared to liquid electrolyte are still unclear. Experiments will investigate how polymer molecular structures affect the electric double layer (EDL) and capacitance at the SPE-electrode interface. By melting SPEs above their melting point to achieve smooth contact with planar electrodes, this work examines how crystalline and amorphous regions of polymers impact charging dynamics and the equilibrium EDL structure. Additionally, this research explores the role of effective contact area between SPEs and flat electrodes. The relationship between viscoelastic behavior, such as viscosity, and interfacial properties like wetting, adhesion, and surface roughness and energy will be examined. By correlating these properties, the study seeks to establish a framework for designing SPEs with enhanced wettability, adhesion, and interfacial performance. By bridging these knowledge gaps, this study seeks to advance the development of SPEs with enhanced performance and scalability for next-generation energy storage devices. ADVISOR(S): Dr. Caiwei Shen, Department of Mechanical Engineering (cshen2@umassd.edu) COMMITTEE MEMBERS: Dr. Maricris Mayes, Department of Chemistry/Biochemistry Dr. Vijaya Chalivendra, Department of Mechanical Engineering Dr. Hangjian Ling, Department of Mechanical Engineering NOTE: All EAS Students are ENCOURAGED to attend.

See description for location

Date: Wednesday, February 12, 2025 Time: 2pm Topic: Experimental Study of Fluid-Induced Vibration of Asymmetric Flexible Structures Location: SENG 110 Abstract: Flow-induced vibrations (FIV) can occur when a flexible or flexibly mounted bluff body is exposed to fluid flow. As the flow passes the structure, the shed vortices downstream of the body can produce fluctuating forces on the structure, causing large-amplitude oscillations. FIV is known as a destructive phenomenon causing fatigue damage to engineering structures. Over the past few decades, numerous studies have been conducted on the FIV of a circular cylinder as a canonical geometry. The FIV response of a bluff body is highly sensitive to its cross-sectional geometry as the location of the separation point, which is intricately linked to the vortex-shedding mechanism, is different for each geometry. Previous studies on the FIV of structures with non-circular and asymmetric cross-sections have mainly focused on the flexibly-mounted rigid bodies in flow. However, to fully understand the complex dynamic response of the system in many real-life applications where the structure has a non-circular cross-section, such as iced-covered electrical transmission lines, decks of suspension bridges, tension chains, and the riser that become asymmetric due to corrosion in the water, the structure's spanwise flexibility should be considered. This research is trying to fill the gap in the literature by doing laboratory measurements to investigate the FIV of flexible bluff bodies with an asymmetric and non-circular cross-section. The two structures studied in this research are (a) a flexible cylinder with a triangular cross-section and (b) a flexible circular cylinder with an attached flexible splitter plate. Among the effective parameters affecting the FIV response of the system, the role of the angle of attack of the triangular cylinder and the length of the splitter plate is investigated in our study. Findings from this research can leverage our fundamental understanding of the fluid-structure interactions response of the long-span flexible asymmetric structures, with applications in the design of fluidic energy harvesters as well as suppression of unwanted vibrations of systems operating in fluid environments. A series of well-controlled lab experiments have been conducted using water channel tests. Cylinder's oscillation was captured using a high-speed imaging technique, and the spanwise continuous response was reconstructed using a modal-analysis based technique. The structural response of the system is analyzed in terms of its oscillation amplitude and frequency. Qualitative and quantitative flow field visualizations and measurements have been conducted using Hydrogen Bubble (HB) and the state-of-the-art time-resolved volumetric Particle Tracking Velocimetry (TR-PTV) techniques. Three-dimensional vortex dynamics in the wake of the structure are studied and analyzed using the proper orthogonal decomposition technique. The interaction between structural dynamic response and the vortex-dominated flow field in the wake of the structure leads to a fully coupled fluid-structure interactions response that is investigated in this research. ADVISOR(S): Dr. Banafsheh Seyed-Aghazadeh, Dept of Mechanical Engineering (b.aghazadeh@umassd.edu) COMMITTEE MEMBERS: Dr. Mehdi Raessi, Department of Mechanical Engineering Dr. Hangjian Ling, Department of Mechanical Engineering Dr. Miles Sundermeyer, Dept of Estuarine & Ocean Sciences/SMAST NOTE: All EAS Students are ENCOURAGED to attend.

See description for location