UB - University at Buffalo, The State University of New York UB Mechanical and Aerospace Engineering
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Fluids and Thermal Sciences

Faculty

Affiliated Faculty

  • Van Slooten, R.

Laboratories

Research Summaries

Simulation of Lipid Vesicles


Lipid vesicles have been proposed as novel drug delivery systems or as micro-reactors. The objective of this work is to investigate the behavior of lipid vesicles when exposed to fluid flow and externally applied electric fields. Using advanced numerical modeling techniques and large-scale computing resources the dynamic behavior of fully three-dimensional vesicles will is explored. An ongoing avenue of research is also the modeling of lipid rafts and patterns within the vesicle membrane. The over-arching goal of this work is to provide researchers the knowledge needed to develop the next generation of vesicle based biotechnologies.

 

Turbulence-Chemistry Interactions in Reactive Compressible Turbulence


Turbulent combustion is a complex physico-chemical phenomenon that is spatially three-dimensional and is of transient nature. This phenomenon has been the subject of intense research within the past sixty years and continues to be of high priority in view of the worldwide concern about energy and pollution control. Since the mean shear is present in most of the turbulent flows, the study of homogeneous shear flows can reveal many features of compressibility in practical turbulent flows. The influence of chemical reaction on the development of compressible turbulent shear flows is being studied by solving the Navier-Stokes equations, the energy equation, and the transport equations for the reactive scalars.
C.K. MADNIA.

 

Stochastic Large Eddy Simulations of Turbulent Combustion


Work is underway in assessing the validity of recently developed stochastic models for large eddy simulation (LES) of turbulent combustion. The assessment is via the use of DNS and is being applied to several reacting flow configuration. The stochastic model is based on the use of the probability density function (PDF) methodology for the unresolved subgrid scale quantities. The DNS data are used in both a priori and a posteriori manners to measure the PDFs of the statistical variables within the subgrid. The consistency, convergence, and accuracy of the LES/PDF equation and the Monte Carlo solution of its equivalent stochastic differential equations are assessed. The model predictions are further appraised by comparisons with data generated by DNS and with experimental measurements. In the absence of a closure for the SGS scalar correlations, the results based on the conventional LES are significantly different from those obtained by DNS. The LES/PDF results show a closer agreement with DNS. These results also agree favorably with laboratory data of exothermic reacting turbulent shear flows, and portray several of the features observed experimentally.
C.K. MADNIA.


Compressibility Effects in Turbulent Shear Flows


The development of the dilatational field is studied by considering the influence of the initial values of the turbulent and gradient Mach numbers. In nonreacting flows, for large values of the gradient Mach number the RDT limit for homogeneous shear flow is recovered. The RDT equations are examined and analytical solutions are found for the long time behavior of the pressure and dilatational velocity modes. The main contributions to the integral of their spectrum functions come from different regions of the wavenumber space than those mostly contributing to the one-point statistics in RDT limit of incompressible turbulent shear flow. This difference accounts for important physics of the dilatational field, and in particular explains the amplification of the dilatational effects in the direction of the mean velocity gradient found in the DNS results.
C.K. MADNIA.


Modeling and DNS of Hydrocarbon Flame-Vortex Interactions


The laminar diffusion flame-vortex ring configuration is a simple configuration that contains some of the key physical characteristics of turbulent diffusion flames. The ongoing investigation can help us extricate some of the fundamental questions that are central to the turbulent diffusion flame processes. The main objective of this study is to gain fundamental understanding of the physicochemical processes that occur during the combustion of non-premixed laminar hydrocarbon fuels. The main thrust of this research is to conduct direct numerical simulations (DNS) of non-premixed flame-vortex interactions with inclusion of "realistic" chemistry models. The DNS generated results will then be used to develop kinetic mechanisms for unsteady combustion systems.
C.K. MADNIA.


Reliable Chemistry Models for Analytical Modeling of Turbulent Combustion


A stumbling block in mathematical modeling of turbulent reacting flows is the mechanism of turbulence-chemistry interactions. The emphasis in almost all previous analytical studies of these flows has been on the turbulence phenomena, not the chemistry. For example, unrealistic one-step reaction schemes have been widely used within the past 15 years. Despite its simplicity and computational convenience, one-step chemistry models are unable to capture many important phenomena such as flame ignition, extinction, propagation, intermediate radical species concentration and soot formation. The objective of this work is to develop and implement more reliable chemistry schemes in theoretical-computational investigations of turbulent combustion phenomena. The implementation of full kinetics schemes for computations of hydrocarbon combustion is impossible; but it is possible to implement reduced kinetics schemes. Reduced schemes imply simplified chemistry mechanisms deduced from the full chemistry. Several of available reduced kinetic schemes are being utilized in mathematical-computational modeling of hydrocarbon diffusion flames in various turbulent flow configurations.
C.K. MADNIA.

 

Numerical Modelling and Simulation of Fires

The objective of this research is to develop an advanced modeling and simulation framework for predicting large-scale fires.  The modeling is based on Large Eddy Simulation (LES) techniques using probabilistic based subgrid scale (SGS) models to account for multiphase coupling of buoyantly driven turbulence, combustion, droplet transport and thermal radiation heat transfer.  The main interest is predicting the heat transfer from these flows to surrounding structures and volatile materials.  Details at: cet.eng.buffalo.edu – P. E. DESJARDIN


Fire Spread and Fluid Structure Modelling

Characteristic of all fires is their exponential growth, which comes from the continued participation of surrounding materials as fuel in the fire event.  Minimizing fire growth requires a detailed understanding of conjugate heat and mass transfer processes that define fire spread and tools which can yield quantitative predictions of fire growth.  The focus of this research is to develop numerical algorithms and material models to describe the response of structures to fire and predict fire growth.  Details at: cet.eng.buffalo.edu – P. E. DESJARDIN

 

Reactive Blast Waves

This effort is to examine shock-induced ignition and burning of reactive particles. These particles are often employed for use in the design of propellants and explosives to increase the energy density and specific impulse. Details at:  cet.eng.buffalo.edu – P. E. DESJARDIN

The Electrohydrodynamics of Vesicles
Vesicles exposed to the combined effects of fluid flow and electric fields have shown a wide and varied set of behaviors. Exposure to electric fields have induced vesicle shapes not normally accessible. Weak electric fields have induced lipid flow patterns in the membranes of multicomponent vesicles. As the electric field strength is increased pores begin to form in the vesicle membrane. This allows foreign substance to either enter or leave the vesicle. Vesicles exposed to strong electric fields have been shown to burst. It is unknown how exposure to combined fluid and electric effects will influence vesicle behavior.This research will address this shortcoming in knowledge by constructing and performing experiments in-silico and in-vitro to study the behavior of single and multicomponent vesicles in fluid flow and during exposure to electric fields.
Funding: NSF, UB
Numerical Methods for Multiphase Fluid Flow
The objective of this research is to develop high performance and accurate numerical methods to model multiphase fluid flow, particularly for incompressible embedded interfaces. The interface is described implicitly using the Gradient Augmented Level Set Method. The fluid equations are modeled using a sharp interface method based on the Immersed Interface Method. The multiphase system results in jumps in the pressure and fluid velocity fields in the domain. These jumps can not be determined a priori and are part of the problem to solve.
Funding: NSF, UB
Fluid-Structure Interaction
Fluid-structure interaction (FSI) occurs in many engineering and biological flows. For example, it occurs in flows in elastic blood vessels, heart valves, marine structures such as risers and conductor tubes in oil drilling platforms, civil structures such as bridges and chimneystacks, etc. Numerical simulations can play a major role in understanding FSI physics and the response behavior over a range of controlling parameters and complement experimental investigations.
Simulations of Biological flows
Biological flows occur in or around living organisms, and their study is a critical prerequisite for elucidating and quantifying presumed links between fluid mechanics and particular biological responses and biochemical processes or specific behavioral and/or evolutionary patterns. Most of such flows take place in multi-connected domains with complex, flexible moving boundaries over a range of Reynolds numbers, which pose great challenges even to the most advanced numerical simulations. We are investigating flows such as the ones that occur in the heart, through prosthetic heart valves, and around aquatic animals in collaborations with physicians and biologists.
Wind/water energy
Generating electricity by burning fossil fuel creates more than 40% of greenhouse gases, causing global climate change. To reduce such emission a major shift in generating electricity from fossil fuels to renewable energy is required. Wind and water energy are a great renewable resource that can help reduce fossil fuel dependencies. The computational tools can have an important role in the design of the new generation of wind/hydrokinetic turbines by providing the 3D flow and mechanical stresses on the blades through fluid-structure interaction simulations.
Image-Based Computational Fluid Dynamics Simulations for Intracranial Aneurysms
At the Hemodynamics and Vascular Biology Lab at the Toshiba Stroke & Vascular Research Center, we aim at understanding pathophysiology of intracranial aneurysms and improving their diagnosis and treatment, by combining computational fluid dynamics (CFD) and engineering design with medical imaging and molecular biology techniques. We analyze aneurysm rupture risk, evaluate endovascular device for stroke intervention, and develop patient-specific image-based computational fluid dynamics and FEM analysis tools to provide both rapid clinical input and in-depth mechanistic understanding. We also employ in vivo and in vitro bioengineering model systems to study flow-mediated vascular responses and aneurysm pathogenesis.
H. MENG. Sponsors: NIH/NINDS, Toshiba Medical Systems, Covidien.

 

Hemodynamic Stresses and Pathogenesis of Intracranial Aneurysms
At the Hemodynamics and Vascular Biology Lab at the Toshiba Stroke & Vascular Research Center, we aim at understanding pathophysiology of intracranial aneurysms and improving their diagnosis and treatment, by combining computational fluid dynamics (CFD) and engineering design with medical imaging and molecular biology techniques. We analyze aneurysm rupture risk, evaluate endovascular device for stroke intervention, and develop patient-specific image-based computational fluid dynamics and FEM analysis tools to provide both rapid clinical input and in-depth mechanistic understanding. We also employ in vivo and in vitro bioengineering model systems to study flow-mediated vascular responses and aneurysm pathogenesis.
H. MENG. Sponsors: NIH/NINDS, Toshiba Medical Systems, Covidien.

 

 

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    Study of Non-premixed flame-wall interaction using vortex ring configuration is done for the first time at the Computational Fluid Dynamics Laboratory.

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