A5023202198- Rheology and Fluid Dynamics Studies
- Fluid Dynamics and Turbulent Flows
- Blood properties and coagulation
- Fluid Dynamics and Vibration Analysis
- Model Reduction and Neural Networks
- Micro and Nano Robotics
- Microfluidic and Capillary Electrophoresis Applications
- Microfluidic and Bio-sensing Technologies
- Nonlinear Dynamics and Pattern Formation
- Lattice Boltzmann Simulation Studies
- Material Dynamics and Properties
- Erythrocyte Function and Pathophysiology
- Nanopore and Nanochannel Transport Studies
- Electrostatics and Colloid Interactions
- Fluid Dynamics and Thin Films
- Neural Networks and Applications
- Surfactants and Colloidal Systems
- Wind Energy Research and Development
- Granular flow and fluidized beds
- Theoretical and Computational Physics
- Pickering emulsions and particle stabilization
- Time Series Analysis and Forecasting
- Wind and Air Flow Studies
- Heat Transfer Mechanisms
- Platelet Disorders and Treatments
University of Wisconsin–Madison
2016-2025
National Louis University
2023
Stellenbosch University
2022
Princeton University
1993-2022
Royal Holloway University of London
2022
University of Indianapolis
2022
Imperial College London
2021
Madison Area Technical College
2021
Madison Group (United States)
2015-2020
Louisiana Tech University
2020
Direct simulations of large populations confined hydrodynamically interacting swimming particles at low Reynolds number are performed. Hydrodynamic coupling between the swimmers leads to large-scale coherent vortex motions in flow and regimes anomalous diffusion that consistent with experimental observations. At concentrations, propelled from behind (like spermatazoa) strongly migrate toward solid surfaces agreement simple theoretical considerations; higher concentrations this localization...
Molecular confinement offers new routes for arraying large DNA molecules, enabling single-molecule schemes aimed at the acquisition of sequence information. Such can rapidly advance to become platforms capable genome analysis if elements a nascent system be integrated an early stage development. Integrated strategies are needed surmounting stringent experimental requirements nanoscale devices regarding fabrication, sample loading, biochemical labeling, and detection. We demonstrate that...
Viscoelastic fluids can exhibit striking flow instabilities under conditions where ordinary Newtonian are stable, owing to the nonlinear coupling of elastic and viscous stresses. This article provides perspectives on viscoelastic by integrating input from speakers at a recent international workshop: historical remarks, characterization flows, discussion experimental simulation tools, modern questions puzzles that motivate further studies this fascinating subject. The materials here will be...
We present a fully parametrized bead–spring chain model for stained λ-phage DNA. The accounts the finite extensibility of molecule, excluded volume effects, and fluctuating hydrodynamic interactions (HI). Parameters are determined from equilibrium experimental data 21 μm DNA, shown to quantitatively predict non-equilibrium behavior molecule. is then used nonequilibrium DNA molecules up 126 μm. In particular, HI gives results that in quantitative agreement with diffusivity over wide range...
We simulate dilute solution dynamics of long flexible polymer molecules in pressure driven flow channels with widths roughly 0.1-10 times the bulk radius gyration. This is done using a self-consistent coarse-grained Langevin description and numerical simulation confined geometry that generated by motions segments. Results are presented for model DNA approximately 10-100 microm contour length micron-scale channels. During flow, chains migrate toward channel centerline, agreement well-known...
Populations of swimming micro-organisms produce fluid motions that lead to dramatically enhanced diffusion tracer particles. Using simulations suspensions particles in a periodic domain, we capture this effect and show it depends qualitatively on the mode swimming: swimmers "pushed" from behind by their flagella greater enhancement than are "pulled" front. The difference is manifested an increase, only occurs for pushers, diffusivity passive tracers velocity correlation length with size...
In this work, a continuum theory is developed for the behavior of flowing dilute polymer solutions near solid surfaces, using bead-spring dumbbell model dissolved chains. Hydrodynamic interactions between chains and wall lead to migration away from in shear flow. At steady state, hydrodynamic effect balanced by molecular diffusion; an analytical expression resulting concentration profile derived. It shown that depletion layer thickness determined normal stresses develop flow can be much...
Single molecule approaches offer the promise of large, exquisitely miniature ensembles for generation equally large data sets. Although microfluidic devices have previously been designed to manipulate single DNA molecules, many functionalities they embody are not applicable very normally extracted from cells. Importantly, such must work within an integrated system enable high-throughput biological or biochemical analysisa key measure any device aimed at chemical/biological interface and...
Flowing blood displays a phenomenon called margination, in which leukocytes and platelets are preferentially found near vessel walls, while erythrocytes depleted from these regions. Here margination is investigated using direct hydrodynamic simulations of binary suspension stiff ($s$) floppy ($f$) capsules, as well stochastic model that incorporates the key particle transport mechanisms suspensions---wall-induced migration shear-induced pair collisions. The allows relative importance two to...
Addition of a small amount very large polymer molecules or micelle-forming surfactants to liquid can dramatically reduce the energy dissipation it exhibits in turbulent flow regime. This rheological drag reduction phenomenon is widely used, for example, Alaska pipeline, but not well-understood, and no comparable technology exists consumption flows gases, which polymers cannot be dissolved. The most striking feature this existence so-called maximum (MDR) asymptote: given geometry driving...
An $O(N)$ method is presented for calculation of hydrodynamic or electrostatic interactions between $N$ point particles in a confined geometry. This approach splits forces sources into local contribution which rapidly decaying free-space analytical solutions to the Stokes Poisson equations are used, and global whose effect determined numerically using fast iterative method. The scheme applied Brownian dynamics simulations flowing polymer solutions, effects concentration on hydrodynamically...
Blood and many other multicomponent suspensions display a segregation behavior in which different components of the suspension are differentially distributed cross-stream direction during flow confined geometry such as an arteriole or microfluidic device. Specifically, blood platelets leukocytes strongly segregated to near-wall region said be "marginated". The present work reviews phenomena suspensions. Well-established results on migration shear-induced diffusion single-component followed...
The past decade has seen a renaissance in the study of polymer solutions flowing confined geometries, driven part by advances visualization large DNA molecules and desire to manipulate for genomic applications. This article summarizes features fundamental physics fluid dynamics that are relevant flow solutions, then reviews recent literature on topic. Experiments have clarified extended prior work showing diffusion flexible polymers is substantially altered confinement that, during flow,...
Significance Clinical hematologists have long known that antiinflammatory glucocorticoids such as dexamethasone and blood pressure-supporting catecholamines epinephrine cause leukocytes to demarginate from the vascular wall microvasculature into main circulation, significantly elevating effective white cell count. Canonically, this has been attributed down-regulation of adhesion molecules selectins, but we show a purely mechanical phenomenon caused by leukocyte softening plays major role...
Wall-bounded turbulence exhibits patterns that persist in time and space: coherent structures. These are important for transport processes form a conceptual framework theoretical approaches. Key observed structures include quasi-streamwise hairpin vortices, as well the localized spots puffs of during transition. This review describes recent research on so-called exact states (ECS) wall-bounded parallel flows at Reynolds numbers Re [Formula: see text] 10 4 ; these nonturbulent, nonlinear...
A data-driven framework is developed to represent chaotic dynamics on an inertial manifold (IM) and applied solutions of the Kuramoto-Sivashinsky equation. hybrid method combining linear nonlinear (neural-network) dimension reduction transforms between coordinates in full state space IM. Additional neural networks predict time evolution The formalism accounts for translation invariance energy conservation, substantially outperforms reduction, reproducing very well key dynamic statistical...
Abstract While many phenomena in physics and engineering are formally high-dimensional, their long-time dynamics often live on a lower-dimensional manifold. The present work introduces an autoencoder framework that combines implicit regularization with internal linear layers L 2 (weight decay) to automatically estimate the underlying dimensionality of data set, produce orthogonal manifold coordinate system, provide mapping functions between ambient space space, allowing for out-of-sample...
An extended Brownian dynamics simulation method is used to characterize the of long DNA molecules flowing in microchannels. The relaxation time increases due confinement agreement with scaling predictions. During flow migrate toward channel center line, and thereby segregate according molecular weight. Capturing these effects requires detailed incorporation solvent method, demonstrating importance hydrodynamic confined macromolecules.
We have simulated Brownian bead-spring chains of up to 125 units with fluctuating hydrodynamic and excluded volume interactions using the Chebyshev polynomial approximation proposed by Fixman [Macromolecules 19, 1204 (1986)] for square root diffusion tensor. developed a fast method continuously determine validity eigenvalue range used in approximation, demonstrated how this may be quickly updated when necessary. also weak first order semiimplicit time integration scheme which offers...
The dynamics of dissolved long-chain macromolecules are different in highly confined environments than bulk solution. A computational method is presented here for detailed prediction these dynamics, and applied to the behavior ∼1–100 μm DNA micron-scale channels. comprised a self-consistent coarse-grained Langevin description polymer numerical solution flow generated by motion segments. Diffusivity longest relaxation time show broad crossover from free-solution centered about point H≈10Sb,...