Chemical Power for Microscopic Robots in Capillaries

The power available to microscopic robots (nanorobots) that oxidize bloodstream glucose while aggregated in circumferential rings on capillary walls is evaluated with a numerical model using axial symmetry and time-averaged release of oxygen from passing red blood cells. Robots about one micron in size can produce up to several tens of picowatts, in steady-state, if they fully use oxygen reaching their surface from the blood plasma. Robots with pumps and tanks for onboard oxygen storage could collect oxygen to support burst power demands two to three orders of magnitude larger. We evaluate effects of oxygen depletion and local heating on surrounding tissue. These results give the power constraints when robots rely entirely on ambient available oxygen and identify aspects of the robot design significantly affecting available power. More generally, our numerical model provides an approach to evaluating robot design choices for nanomedicine treatments in and near capillaries.Comment: 28 pages, 7 figure

Modelling of heat and mass transfer processes in neonatology

This paper reviews some of our recent applications of Computational Fluid Dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled Infant Heat Balance Module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices

Large eddy simulation of plume dispersion behind an aircraft in the take-off phase

The aim of this paper is to provide an investigation, using large eddy simulation, into plume dispersion behind an aircraft in co-flowing take-off conditions. Validation studies of the computational model were presented by Aloysius and Wrobel (Environ Model Softw 24:929–937, 2009) and a study of the flow and dispersion properties of a double-engine aircraft jetwas presented by Aloysius et al. EEC/SEE/2007/001,EUROCONTROLExperimentalCentre, http://www.eurocontrol.int/eec/gallery/content/public/document/eec/report/2007/ 032_ALAQS_comparison_of_CFD_and_Lagrangian_dispersion_methods.pdf), in which only the engine was modelled. In this paper, the complete geometry of a Boeing 737 is modelled and investigated. The currentwork represents a contribution towards a better understanding of the source dynamics behind an airplane jet engine during the take-off and landing phases. The information provided from these simulations will be useful for future improvements of existing dispersion models

Heat and mass transfer under an infant radiant warmer – Development of a numerical model

This is the post-print version of the final paper published in Medical Engineering & Physics. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.The main objectives of this paper are to present a procedure of how to create and set up a model for the physical processes that take place within an infant radiant warmer and to validate that Computational Fluid Dynamics (CFD) can be used to resolve such problems. In this study, the results are obtained for a simplified model, both in terms of the geometry employed and the prescribed boundary conditions. The results were numerically verified in terms of the convergence history, monitor data and the physical correctness. This study shows that the physical situation is unsteady and the results tend to oscillate, almost periodically, around a mean value. The results presented in the paper are found to be in qualitative agreement with the experimental data. This gives us confidence that the techniques employed in this paper are appropriate and form the starting point for the inclusion of more realistic effects, e.g. real shape of the newborn and radiant lamp, heat generated inside the newborn, moisture transport, etc.European Union Marie Curie Fellowship programm

Co-axial capillaries microfluidic device for synthesizing size- and morphology-controlled polymer core-polymer shell particles

An easy assembling-disassembling co-axial capillaries microfluidic device was built up for the production of double droplets. Uniform polymer core-polymer shell particles were synthesized by polymerizing the two immiscible monomer phases composing the double droplet. Thus poly(acrylamide) core-poly(tripropylenglycol-diacrylate) shell particles with controlled core diameter and shell thickness were simply obtained by adjusting operating parameters. An empirical law was extracted from experiments to predict core and shell sizes. Additionally uniform and predictable non-spherical polymer objects were also prepared without adding shape-formation procedures in the experimental device. An empirical equation for describing the lengths of rod-like polymer particles is also presented

Applying rotorcraft modelling technology to renewable energy research

The perceived need to reduce mankind's impact on the global climate motivates towards a future society in which a significant proportion of its energy needs will be extracted from the winds and the tides of the planet. This paper shows several examples of the application of Brown's Vorticity Transport Model, originally developed to perform simulations of helicopter aeromechanics and wake dynamics, to the analysis of the performance of renewable energy devices and their possible impact on the environment. Prediction of the loading on wind turbines introduces significant additional challenges to such a model, including the need to account fully for the effects of radial flow on blade stall. The wake-mediated aerodynamic interactions that occur within a wind farm can reduce its power output significantly, but this problem is very similar to that where the aerodynamic unsteadiness of the coupled wake of the main and tail rotors of a helicopter can result in significantly increased pilot workload. The helicopter-related problem of brownout, encountered during operations in desert conditions, has its analogue in the entrainment of sediment into the wakes of tidal turbines. In both cases it may be possible to ameliorate the influence of the rotor on its environment by careful and well-informed design. Finally, calculations of the distortion and dispersal of the exhaust plumes of a helicopter by the wake of its rotor allow insight into how wind turbines might interfere with the dispersal of pollutants from nearby industrial sites. These examples show how cross-disciplinary information transfer between the rotorcraft field and the renewable energy community is helping to develop the technologies that will be required by our future society, as well as helping to understand the environmental issues that might need to be faced as these technologies become more prevalent

Experimental and numerical investigation of Helmholtz resonators and perforated liners as attenuation devices in industrial gas turbine combustors

This paper reports upon developments in the simulation of the passive control of combustion dynamics in industrial gas turbines using acoustic attenuation devices such as Helmholtz resonators and perforated liners. Combustion instability in gas turbine combustors may, if uncontrolled, lead to large-amplitude pressure fluctuations, with consequent serious mechanical problems in the gas turbine combustor system. Perforated combustor walls and Helmholtz resonators are two commonly used passive instability control devices. However, experimental design of the noise attenuation device is time-consuming and calls for expensive trial and error practice. Despite significant advances over recent decades, the ability of Computational Fluid Dynamics to predict the attenuation of pressure fluctuations by these instability control devices is still not well validated. In this paper, the attenuation of pressure fluctuations by a group of multi-perforated panel absorbers and Helmholtz resonators are investigated both by experiment and computational simulation. It is demonstrated that CFD can predict the noise attenuation from Helmholtz resonators with good accuracy. A porous material model is modified to represent a multi-perforated panel and this perforated wall representation approach is demonstrated to be able to accurately predict the pressure fluctuation attenuation effect of perforated panels. This work demonstrates the applicability of CFD in gas turbine combustion instability control device design

The motion of a deforming capsule through a corner

A three-dimensional deformable capsule convected through a square duct with a corner is studied via numerical simulations. We develop an accelerated boundary integral implementation adapted to general geometries and boundary conditions. A global spectral method is adopted to resolve the dynamics of the capsule membrane developing elastic tension according to the neo-Hookean constitutive law and bending moments in an inertialess flow. The simulations show that the trajectory of the capsule closely follows the underlying streamlines independently of the capillary number. The membrane deformability, on the other hand, significantly influences the relative area variations, the advection velocity and the principal tensions observed during the capsule motion. The evolution of the capsule velocity displays a loss of the time-reversal symmetry of Stokes flow due to the elasticity of the membrane. The velocity decreases while the capsule is approaching the corner as the background flow does, reaches a minimum at the corner and displays an overshoot past the corner due to the streamwise elongation induced by the flow acceleration in the downstream branch. This velocity overshoot increases with confinement while the maxima of the major principal tension increase linearly with the inverse of the duct width. Finally, the deformation and tension of the capsule are shown to decrease in a curved corner