Session: 08-01: Poster Session

Paper Number: 151067

151067 - Study of Thermodynamic Nonlinearities on Turbulent Mixing in Supercritical Flow 

Abstract: 

Supercritical fluids, with their unique thermodynamic properties and significant deviations from ideal gas behavior, present both challenges and opportunities in engineering applications. This research investigates how thermodynamic nonlinearities in supercritical fluids, particularly supercritical carbon dioxide (CO₂), impact fluid dynamics, aiming to enhance the design and optimization of energy systems, propulsion devices, and other advanced technologies. Supercritical fluids exhibit highly nonlinear variations in their equation of state, thermodynamic quantities, and transport properties. These variations can significantly affect parameters such as enthalpy, isothermal compressibility, speed of sound, and Prandtl number, leading to amplified local pressure and temperature perturbations. Understanding these nonlinear effects is crucial for applications involving confined flows, such as combustors, where enhanced pressure oscillations can couple with the acoustic modes of the geometry, potentially causing operational instabilities. This study employs a combination of theoretical analysis, computational simulations, and data visualization. Maxwell's relations are used to express properties like the speed of sound and isothermal compressibility as functions of partial derivatives of density with respect to pressure and temperature, highlighting the role of thermodynamic nonlinearities at supercritical conditions. The conservation equations are recast in terms of pressure, velocity, and temperature to demonstrate how these quantities affect fluid dynamic operators. The Jacobian inversion technique is applied to maintain the integrity of the operators in the governing equations, illustrating the modulation of fluid dynamic operators by thermodynamic metrics. A crucial aspect of this research is the examination of a supercritical mixing layer designed to perturb these nonlinearities deliberately. Computational techniques, including Direct Numerical Simulations (DNS) and Wall-Resolved Large Eddy Simulations (LES), are employed to simulate the mixing layer and generate contour plots of pressure, temperature, and density. These visualizations provide a qualitative understanding of the property variations within the layer. Line plots are extracted to analyze the spatial variations of key parameters across the mixing layer, quantifying the degree to which they modulate quantities such as pressure and temperature. Results demonstrate that at specific supercritical conditions, property variations can significantly amplify pressure oscillations and temperature fluctuations. This amplification has critical implications for confined flows, where enhanced pressure oscillations can couple with the acoustic modes of the geometry, leading to potential operational instabilities. The study underscores the importance of understanding these mechanisms to predict and control the effects of thermodynamic nonlinearities in practical applications. In conclusion, this research advances the understanding of thermodynamic nonlinearities in supercritical fluids and their impact on fluid dynamics. By comparing supercritical and ideal gas conditions, the study highlights the significant modulation of key fluid dynamic processes by nonlinear thermophysical properties. The insights gained from this research contribute to developing strategies for mitigating adverse effects in engineering systems, ensuring more stable and efficient operation. Future work will focus on refining the analytical models and extending the computational analysis to more complex geometries and flow conditions, ultimately paving the way for improved predictions in complex fluid dynamics scenarios involving supercritical fluids.

Presenting Author: S M Al Mamun Or Roshid Prairie View A&M University

Presenting Author Biography: S M Al Mamun Or Roshid is a graduate student in the Mechanical Engineering Department at Prairie View A&M University, where he also serves as a Graduate Research Assistant in the Center for High Pressure Combustion (CHPC) in Microgravity. Under the guidance of Dr. Ziaul Huque (PVAMU) and Dr. Joseph Oefelein (Georgia Institute of Technology), his research focuses on the critical areas of liquid fuel combustion at high pressures.

Authors:

S M Al Mamun Or Roshid Prairie View A&M University
Joseph Oefelein Georgia Institute of Technology
Ziaul Huque Prairie View A&M University