The Role of Complex Fluids on the Flow and Instabilities of Particle-Laden Liquids

In advanced technologies, small devices, such as microfluidic devices play a crucial role in cell detection. These devices rely on carefully arranging particles under flowing conditions, a process often requiring the controlled movement of particles across the flow. Typically, this movement is achieved by using external fields like electricity, magnetism, acoustics, or optics, but this method has limitations and depends on specific particle properties. An alternative approach known as elasto-inertial focusing, instead balances natural forces within the flow to concentrate particles along the centerline of the device. While this approach promises a noninvasive way to achieve the desired particle movement, it has challenges. When dealing with certain types of fluids (polymeric or non-Newtonian), there is a limit to how fast particles can be processed due to the onset of elastic instabilities. To address these challenges, the research will develop novel experimental methods and numerical simulations that go beyond the limitations of microfluidic devices. Experiments and simulations together should provide a more thorough understanding of the distribution of velocity and particle patterns in both the fluid and particle phases. In addition to advancing scientific knowledge, this research has a broader impact on education. The team is committed to providing unique opportunities for interdisciplinary STEM education and training. The goal is to equip a diverse group of students and researchers to emerge as the next generation of interdisciplinary scientists and engineers. The planned outreach activities include creating hands-on activities for K-12 programs, with a focus on underrepresented students. This project aims to uncover new and essential understandings of the physics involved in fluid flows carrying non-Brownian particles within complex solvents. The proposed effort combines highly resolved numerical simulations with the experiments, which include time-resolved and highly resolved planar particle image velocimetry (PIV), particle tracking velocimetry (PTV), and Magnetic resonance imaging (MRI), focused specifically on suspensions of spherical particles in complex fluids. Using a comprehensive approach that integrates both numerical and experimental studies, the project explores specific conditions defined by considerations of particle concentrations and fluid rheological properties. The primary goal is to provide a better physical understanding of both the flow characteristics and instabilities in the presence of particles and complex fluids. A better understanding of these flows has implications for various industries, including inkjet printing, biomedical devices, and even enhanced oil recovery. This study has the potential to benefit society by providing valuable insights and tools for effectively managing particle-laden flows in practical applications. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.