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Key research themes
1. How do hydrodynamic interactions and shear-induced migration influence particle distribution and stability in shear and pressure-driven dilute suspensions?
This area investigates the microstructure evolution and spatial distribution of particles suspended in fluid flows subjected to shear and pressure gradients, focusing on dilute to moderately concentrated suspensions. The central concern is understanding how hydrodynamic pair interactions, shear-induced migration, and normal stresses govern particle migration, concentration profiles, and flow stability. These questions are critical for modeling suspension rheology, predicting viscosity variations, and controlling particle segregation in industrial and physiological contexts.
Key finding: Developed an exact pairwise hydrodynamic theory based on Boltzmann-like master equations that predicts a non-singular particle concentration boundary layer near zero shear rate regions (e.g., channel centerline) by... Read more
Key finding: Performed linear stability analysis on gravity-driven shallow particle-laden flows, demonstrating that shear-induced migration leads to viscosity stratification via microstructure development. Identified two instability modes... Read more
Key finding: Reviewed and characterized natural geophysical particle-laden flows as complex mixtures exhibiting varying solid-fluid interactions and flow regimes, emphasizing the role of gravitational driving forces coupled with... Read more
Key finding: Using particle-resolved direct numerical simulations with the lattice Boltzmann method, derived and computed radial transport equations for turbulent kinetic energy conditioned on moving solid particle surfaces in forced... Read more
2. In what ways do finite-size particles modulate turbulent flows through two-way coupling and particle clustering in wall-bounded turbulent regimes?
Research under this theme focuses on the intricate two-way interactions between finite-size inertial particles and turbulent carrier flows, especially in wall-bounded geometries like channels and Couette flows. Key objectives include understanding how particle size, rotation, and clustering affect turbulence intensity, coherent structure modification, and energy transfer processes. These insights are essential for predicting turbulence augmentation or attenuation phenomena, optimizing industrial particulate flows, and modeling environmental transport processes accurately.
Key finding: Utilized fully-resolved lattice Boltzmann simulations to reveal that finite-size spherical particles form clusters of varying strength depending on their size, and particle rotation influences clustering behavior.... Read more
Key finding: Through DNS of two-way coupled turbulent Couette flow, characterized the dual role of particle inertia on turbulence: low-inertia particles enhance large-scale vortical structures facilitating laminar-to-turbulent transition,... Read more
Key finding: Conducted DNS at Reτ=180 with varying mass loading and fixed Stokes number, revealing a non-monotonic augmentation of streamwise turbulence fluctuations peaking at intermediate mass loading (ϕm=0.75), while wall-normal and... Read more
Key finding: Analyzed turbulence statistics conditional on fluid-solid interfaces in particle-resolved DNS of homogeneous isotropic turbulence. Derivation and evaluation of radial transport equations elucidated localized turbulence... Read more
3. What mechanistic roles do particle size disparity and granular temperature gradients play in size segregation and mixing behaviors in particle-laden flows?
This research strand examines the influence of particle size differences and granular temperature anisotropies on segregation patterns and mixing efficiency in granular and particle-laden flows. Investigations range from microchannel inertial flows to geophysical avalanches and turbulent river sediment transport. Understanding how size-dependent forces (e.g., granular analogs of Saffman lift), wake-induced interactions, and particle clustering drive segregation and mixing offers actionable insights for sediment transport modeling, microfluidic device design, and industrial mixing processes.
Key finding: Via discrete element method simulations, discovered that in rapid granular flows down steep inclines, large particles segregate into the interior dense core rather than surface layers, contrasted with slower flows.... Read more
Key finding: Identified a velocity lag of large intruder particles relative to bulk flow in dense granular chute flows and quantified an anisotropic pressure/stress field surrounding the intruders. Proposed a scaling law between lift... Read more
Key finding: Conducted high-resolution flume experiments tracking sediment transport rates by particle size, revealing that small particles (< ~5 mm) remain trapped in wake vortices generated by 'keystone' large particles (>20 mm) until... Read more
Key finding: Provided experimental evidence of self-organization phenomena where particles in inertial microchannel flows spontaneously form regular particle trains aligned along the flow direction. Demonstrated these microchannel flow... Read more