15,012 research outputs found
Theoretical and Numerical Investigation of Liquid-Gas Interface Location of Capillary Driven Flow During the Time Throughout Circular Microchannels
The main aim of this study is to find the best, most rapid, and the most
accurate numerical method to find the liquid-gas interface of capillary driven
flow during the time in circular Microchannels by using COMSOL Multiphysics
software. Capillary driven flow by eliminating micropumps or any physical
pressure gradient generators can make the microfluidic devices cheaper and more
usable. Hence, by using this two-phase flow, the final costs of lots of
microfluidic devices and lab-on-a-chip can significantly be decreased and help
them to be commercialized. The first step to employing the capillary flow in
these devices is the simulation of this flow inside the microchannels. One of
the most common and valid software for this work is COMSOL Multiphysics; this
fact reveals the importance of this study. In this research study, simulation
results obtained by using two possible numerical methods in this software, for
capillary flows of water and ethanol in two different circular microchannels,
verified and compared with four other methods, which verified experimentally
before. Finally, the most accurate and time-saving numerical method of this
software will be specified. This appropriate technique can contribute to
simulate microfluidic and lab-on-a-chip devices, which are made of different
mechanical and electrical parts, in COMSOL Multiphysics software by choosing
the best method.Comment: 7 pages, 13 figures, 7 tables, 2017 5th International Conference on
Robotics and Mechatronics (ICROM
A multiscale-multiphysics strategy for numerical modeling of thin piezoelectric sheets
Flexible piezoelectric devices made of polymeric materials are widely used
for micro- and nano-electro-mechanical systems. In particular, numerous recent
applications concern energy harvesting. Due to the importance of computational
modeling to understand the influence that microscale geometry and constitutive
variables exert on the macroscopic behavior, a numerical approach is developed
here for multiscale and multiphysics modeling of piezoelectric materials made
of aligned arrays of polymeric nanofibers. At the microscale, the
representative volume element consists in piezoelectric polymeric nanofibers,
assumed to feature a linear piezoelastic constitutive behavior and subjected to
electromechanical contact constraints using the penalty method. To avoid the
drawbacks associated with the non-smooth discretization of the master surface,
a contact smoothing approach based on B\'ezier patches is extended to the
multiphysics framework providing an improved continuity of the
parameterization. The contact element contributions to the virtual work
equations are included through suitable electric, mechanical and coupling
potentials. From the solution of the micro-scale boundary value problem, a
suitable scale transition procedure leads to the formulation of a macroscopic
thin piezoelectric shell element.Comment: 11 pages, 6 pages, 21 reference
Optimal modelling and experimentation for the improved sustainability of microfluidic chemical technology design
Optimization of the dynamics and control of chemical processes holds the promise of improved sustainability for chemical technology by minimizing resource wastage. Anecdotally, chemical plant may be substantially over designed, say by 35-50%, due to designers taking account of uncertainties by providing greater flexibility. Once the plant is commissioned, techniques of nonlinear dynamics analysis can be used by process systems engineers to recoup some of this overdesign by optimization of the plant operation through tighter control. At the design stage, coupling the experimentation with data assimilation into the model, whilst using the partially informed, semi-empirical model to predict from parametric sensitivity studies which experiments to run should optimally improve the model. This approach has been demonstrated for optimal experimentation, but limited to a differential algebraic model of the process. Typically, such models for online monitoring have been limited to low dimensions.
Recently it has been demonstrated that inverse methods such as data assimilation can be applied to PDE systems with algebraic constraints, a substantially more complicated parameter estimation using finite element multiphysics modelling. Parametric sensitivity can be used from such semi-empirical models to predict the optimum placement of sensors to be used to collect data that optimally informs the model for a microfluidic sensor system. This coupled optimum modelling and experiment procedure is ambitious in the scale of the modelling problem, as well as in the scale of the application - a microfluidic device. In general, microfluidic devices are sufficiently easy to fabricate, control, and monitor that they form an ideal platform for developing high dimensional spatio-temporal models for simultaneously coupling with experimentation.
As chemical microreactors already promise low raw materials wastage through tight control of reagent contacting, improved design techniques should be able to augment optimal control systems to achieve very low resource wastage. In this paper, we discuss how the paradigm for optimal modelling and experimentation should be developed and foreshadow the exploitation of this methodology for the development of chemical microreactors and microfluidic sensors for online monitoring of chemical processes. Improvement in both of these areas bodes to improve the sustainability of chemical processes through innovative technology. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved
The Actuator Design and the Experimental Tests of a New Technology Large Deformable Mirror for Visible Wavelengths Adaptive Optics
Recently, Adaptive Secondary Mirrors showed excellent on-sky results in the
Near Infrared wavelengths. They currently provide 30mm inter-actuator spacing
and about 1 kHz bandwidth. Pushing these devices to be operated at visible
wavelengths is a challenging task. Compared to the current systems, working in
the infrared, the more demanding requirements are the higher spatial resolution
and the greater correction bandwidth. In fact, the turbulence scale is shorter
and the parameter variation is faster. Typically, the former is not larger than
25 mm (projected on the secondary mirror) and the latter is 2 kHz, therefore
the actuator has to be more slender and faster than the current ones. With a
soft magnetic composite core, a dual-stator and a single-mover, VRALA, the
actuator discussed in this paper, attains unprecedented performances with a
negligible thermal impact. Pre-shaping the current required to deliver a given
stroke greatly simplifies the control system, whose output supplies the current
generator. As the inductance depends on the mover position, the electronics of
this generator, provided with an inductance measure circuit, works also as a
displacement sensor, supplying the control system with an accurate feed-back
signal. A preliminary prototype, built according to the several FEA
thermo-magnetic analyses, has undergone some preliminary laboratory tests. The
results of these checks, matching the design results in terms of power and
force, show that the the magnetic design addresses the severe specifications
Multiphysics Finite\u2013Element Modelling of an All\u2013Vanadium Redox Flow Battery for Stationary Energy Storage
All-Vanadium Redox Flow Batteries (VRFBs) are emerging as a novel technology for stationary energy storage. Numerical models are useful for exploring the potential performance of such devices, optimizing the structure and operating condition of cell stacks, and studying its interfacing to the electrical grid. A one-dimensional steady-state multiphysics model of a single VRFB, including mass, charge and momentum transport and conservation, and coupled to a kinetic model for electrochemical reactions, is first presented. This model is then extended, including reservoir equations, in order to simulate the VRFB charge and discharge dynamics. These multiphysics models are discretized by the finite element method in a commercial software package (COMSOL). Numerical results of both static and dynamic 1D models are compared to those from 2D models, with the same parameters, showing good agreement. This motivates the use of reduced models for a more efficient system simulation
Research and Education in Computational Science and Engineering
Over the past two decades the field of computational science and engineering
(CSE) has penetrated both basic and applied research in academia, industry, and
laboratories to advance discovery, optimize systems, support decision-makers,
and educate the scientific and engineering workforce. Informed by centuries of
theory and experiment, CSE performs computational experiments to answer
questions that neither theory nor experiment alone is equipped to answer. CSE
provides scientists and engineers of all persuasions with algorithmic
inventions and software systems that transcend disciplines and scales. Carried
on a wave of digital technology, CSE brings the power of parallelism to bear on
troves of data. Mathematics-based advanced computing has become a prevalent
means of discovery and innovation in essentially all areas of science,
engineering, technology, and society; and the CSE community is at the core of
this transformation. However, a combination of disruptive
developments---including the architectural complexity of extreme-scale
computing, the data revolution that engulfs the planet, and the specialization
required to follow the applications to new frontiers---is redefining the scope
and reach of the CSE endeavor. This report describes the rapid expansion of CSE
and the challenges to sustaining its bold advances. The report also presents
strategies and directions for CSE research and education for the next decade.Comment: Major revision, to appear in SIAM Revie
Experimental and Numerical Investigation of Thermal Performance of a Crossed Compound Parabolic Concentrator with PV Cell
Crossed compound parabolic concentrator (CCPC) is a solar energy device used to increase the photovoltaic (PV) cell electrical power output. CCPC’s thermal and optical performance issues are equally important for a PV cell or module to work under a favourable operating condition. However, most work to-date is emphasised on its optical performance paying a little attention to the thermal characteristics. In this contribution, we investigate the thermal performance of a CCPC with PV cell at four different beam incidences (0o, 10o, 20o, 30o and 40o). Initially, experiment is performed in the indoor PV laboratory at the University of Exeter with 1kW/m2 radiation intensity. 3D simulations are carried out to first validate the predicted data and then to characterise the overall performance. Results show that the temperature in the PV silicon layer is the highest at 0o and 30o, with the top glass cover of CCPC having the lowest temperature at all the incidences. The temperature and optical efficiency profiles at the various incidences predicted by simulation show very good agreement with the measurements, especially at 0o incidence. This study provides useful information for understanding the coupled optical-thermal performance of the CCPC with PV cell working at various conditions
Experiences from Software Engineering of Large Scale AMR Multiphysics Code Frameworks
Among the present generation of multiphysics HPC simulation codes there are
many that are built upon general infrastructural frameworks. This is especially
true of the codes that make use of structured adaptive mesh refinement (SAMR)
because of unique demands placed on the housekeeping aspects of the code. They
have varying degrees of abstractions between the infrastructure such as mesh
management and IO and the numerics of the physics solvers. In this experience
report we summarize the experiences and lessons learned from two of such major
software efforts, FLASH and Chombo.Comment: Experience Repor
Computational homogenization of fibrous piezoelectric materials
Flexible piezoelectric devices made of polymeric materials are widely used
for micro- and nano-electro-mechanical systems. In particular, numerous recent
applications concern energy harvesting. Due to the importance of computational
modeling to understand the influence that microscale geometry and constitutive
variables exert on the macroscopic behavior, a numerical approach is developed
here for multiscale and multiphysics modeling of thin piezoelectric sheets made
of aligned arrays of polymeric nanofibers, manufactured by electrospinning. At
the microscale, the representative volume element consists in piezoelectric
polymeric nanofibers, assumed to feature a piezoelastic behavior and subjected
to electromechanical contact constraints. The latter are incorporated into the
virtual work equations by formulating suitable electric, mechanical and
coupling potentials and the constraints are enforced by using the penalty
method. From the solution of the micro-scale boundary value problem, a suitable
scale transition procedure leads to identifying the performance of a
macroscopic thin piezoelectric shell element.Comment: 22 pages, 13 figure
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