837 research outputs found
Interactive simulation of fire, burn and decomposition
This work presents an approach to effectively integrate into one unified modular
fire simulation framework the major processes related to fire, namely: a burning
process, chemical combustion, heat distribution, decomposition and deformation of
burning solids, and rigid body simulation of the residue. Simulators for every stage
are described, and the modular structure enables switching to different simulators if
more accuracy or more interactivity is desired. A “Stable Fluids” based three gas
system is used to model the combustion process, and the heat generated during the
combustion is used to drive the flow of the hot air. Objects, if exposed to enough
heat, ignite and start burning. The decomposition of the burning object is modeled as
a level set method, driven by the pyrolysis process, where the burning object releases
combustible gases. Secondary deformation effects, such as bending burning matches
and crumpling burning paper, are modeled as a proxy based deformation.
Physically based simulation, done at interactive rates, enables the user to ef-
ficiently test different setups, as well as interact and change the conditions during
the simulation. The graphics card is used to generate additional frames for real-time
visualization.
This work further proposes a method for controlling and directing high resolution
simulations. An interactive coarse resolution simulation is provided to the user as a “preview” to control and achieve the desired simulation behavior. A higher resolution
“final” simulation that creates all the fine scale behavior is matched to the preview
simulation such that the preview and final simulations behave in a similar manner.
In this dissertation, we highlighted a gap within the CG community for the
simulation of fire. There has not previously been a physically based yet interactive
simulation for fire. This dissertation describes a unified simulation framework for
physically based simulation of fire and burning. Our results show that our implementation
can model fire, objects catching fire, burning objects, decomposition of
burning objects, and additional secondary deformations. The results are plausible
even at interactive frame rates, and controllable
On the TFNS Subgrid Models for Liquid-Fueled Turbulent Combustion
This paper describes the time-filtered Navier-Stokes (TFNS) approach capable of capturing unsteady flow structures important for turbulent mixing in the combustion chamber and two different subgrid models used to emulate the major processes occurring in the turbulence-chemistry interaction. These two subgrid models are termed as LEM-like model and EUPDF-like model (Eulerian probability density function), respectively. Two-phase turbulent combustion in a single-element lean-direct-injection (LDI) combustor is calculated by employing the TFNS/LEM-like approach as well as the TFNS/EUPDF-like approach. Results obtained from the TFNS approach employing these two different subgrid models are compared with each other, along with the experimental data, followed by more detailed comparison between the results of an updated calculation using the TFNS/LEM-like model and the experimental data
Modelling of Biotechnological Processes - An approach based on Artificial Neural Networks
In this chapter we describe a software tool for modelling fermentation processes, the FerMoANN, which allows researchers in biology and biotechnology areas to access the potential of Artificial Neural Networks (ANNs) for this task. The FerMoANN is tested and validated using two fermentation processes, an Escherichia coli recombinant protein production and the production of a secreted protein with Saccharomyces cerevisiae in fed-batch reactors. The application to these two case studies, tested for different configurations of feedforward ANNs, illustrate the usefulness of these structures, when trained according to a supervised learning paradigm
Controlling liquids using meshes
We present an approach for artist-directed animation of liquids using multiple levels of control over the simulation, ranging from the overall tracking of desired shapes to highly detailed secondary effects such as dripping streams, separating sheets of fluid, surface waves and ripples. The first portion of our technique is a volume preserving morph that allows the animator to produce a plausible fluid-like motion from a sparse set of control meshes. By rasterizing the resulting control meshes onto the simulation grid, the mesh velocities act as boundary conditions during the projection step of the fluid simulation. We can then blend this motion together with uncontrolled fluid velocities to achieve a more relaxed control over the fluid that captures natural inertial effects. Our method can produce highly detailed liquid surfaces with control over sub-grid details by using a mesh-based surface tracker on top of a coarse grid-based fluid simulation. We can create ripples and waves on the fluid surface attracting the surface mesh to the control mesh with spring-like forces and also by running a wave simulation over the surface mesh. Our video results demonstrate how our control scheme can be used to create animated characters and shapes that are made of water
Tools for fluid simulation control in computer graphics
L’animation basée sur la physique peut générer des systèmes aux comportements complexes
et réalistes. Malheureusement, contrôler de tels systèmes est une tâche ardue. Dans le cas
de la simulation de fluide, le processus de contrôle est particulièrement complexe. Bien
que de nombreuses méthodes et outils ont été mis au point pour simuler et faire le rendu
de fluides, trop peu de méthodes offrent un contrôle efficace et intuitif sur une simulation
de fluide. Étant donné que le coût associé au contrôle vient souvent s’additionner au coût
de la simulation, appliquer un contrôle sur une simulation à plus haute résolution rallonge
chaque itération du processus de création. Afin d’accélérer ce processus, l’édition peut se
faire sur une simulation basse résolution moins coûteuse. Nous pouvons donc considérer que
la création d’un fluide contrôlé peut se diviser en deux phases: une phase de contrôle durant
laquelle un artiste modifie le comportement d’une simulation basse résolution, et une phase
d’augmentation de détail durant laquelle une version haute résolution de cette simulation
est gĂ©nĂ©rĂ©e. Cette thèse prĂ©sente deux projets, chacun contribuant Ă l’état de l’art reliĂ© Ă
chacune de ces deux phases.
Dans un premier temps, on introduit un nouveau système de contrôle de liquide représenté
par un modèle particulaire. À l’aide de ce système, un artiste peut sélectionner dans une base
de données une parcelle de liquide animé précalculée. Cette parcelle peut ensuite être placée
dans une simulation afin d’en modifier son comportement. À chaque pas de simulation, notre
système utilise la liste de parcelles actives afin de reproduire localement la vision de l’artiste.
Une interface graphique intuitive a été développée, inspirée par les logiciels de montage vidéo,
et permettant Ă un utilisateur non expert de simplement Ă©diter une simulation de liquide.
Dans un second temps, une méthode d’augmentation de détail est décrite. Nous proposons
d’ajouter une étape supplémentaire de suivi après l’étape de projection du champ de
vitesse d’une simulation de fumée eulérienne classique. Durant cette étape, un champ de
perturbations de vitesse non-divergent est calculé, résultant en une meilleure correspondance
des densités à haute et à basse résolution. L’animation de fumée résultante reproduit fidèlement
l’aspect grossier de la simulation d’entrée, tout en étant augmentée à l’aide de détails
simulés.Physics-based animation can generate dynamic systems of very complex and realistic behaviors.
Unfortunately, controlling them is a daunting task. In particular, fluid simulation
brings up particularly difficult problems to the control process. Although many methods
and tools have been developed to convincingly simulate and render fluids, too few methods
provide efficient and intuitive control over a simulation. Since control often comes with extra
computations on top of the simulation cost, art-directing a high-resolution simulation leads
to long iterations of the creative process. In order to shorten this process, editing could be
performed on a faster, low-resolution model. Therefore, we can consider that the process of
generating an art-directed fluid could be split into two stages: a control stage during which
an artist modifies the behavior of a low-resolution simulation, and an upresolution stage
during which a final high-resolution version of this simulation is driven. This thesis presents
two projects, each one improving on the state of the art related to each of these two stages.
First, we introduce a new particle-based liquid control system. Using this system, an
artist selects patches of precomputed liquid animations from a database, and places them in
a simulation to modify its behavior. At each simulation time step, our system uses these entities
to control the simulation in order to reproduce the artist’s vision. An intuitive graphical
user interface inspired by video editing tools has been developed, allowing a nontechnical
user to simply edit a liquid animation.
Second, a tracking solution for smoke upresolution is described. We propose to add an
extra tracking step after the projection of a classical Eulerian smoke simulation. During
this step, we solve for a divergence-free velocity perturbation field resulting in a better
matching of the low-frequency density distribution between the low-resolution guide and the
high-resolution simulation. The resulting smoke animation faithfully reproduces the coarse
aspect of the low-resolution input, while being enhanced with simulated small-scale details
Multi-functional, self-sensing and automated real-time non-contact liquid dispensing system
Liquid dispensing in the order of pico-liter has become more and more important in biology, electronics and micro-electronic-mechanical-system (MEMS) during the past two decades due to the rapid progress of researches on the deoxyribonucleic acid (DNA) microarray, compact and low-cost direct write technology (DWT), organic semiconductors and nano-particles.
The existing approaches, commercialized or experimental, to liquid dispensing in minute amounts have one common shortcoming: open loop control, i.e., they have no direct control on the quality of dispensed liquid. In contrast, the SmartPin has intrinsic self-sensing capability to not only control the process of liquid dispensing, but also the results of the dispensed liquid in real time. The dual purpose fiber optics sensor/plunger is able to detect the status of liquid morphology under dispensing, in real time, by the internal light sensor and control both the amount and the manner of liquid dispensing by its plunger-like movements.
This dissertation work has implemented, with the SmartPin technology, a frilly automated DNA microarrayer based on the first generation prototype developed at NJIT\u27s Real Time Control Laboratory. This new DNA microarrayer fulfills all requirements in each step of DNA microarray fabrication, such as thorough cleaning to avoid cross contamination and clogging, aspiration of tiny amount of DNA samples, spotting on multiple slides, and flexible in stream change of DNA samples. Experiment results shows that this DNA microarrayer compares favorably with its commercialized counterpart OmniGrid 100 with SMP3 pins. As a verification of robust implementation and on-the-fly control of spot morphology, high volume of spots (120 K) have been made, from which the corresponding experiment data has been obtained, categorized and normalized as template database. In addition, this dissertation research explores the patterned microline-drawing capability of the SmartPin. Two approaches, spot sequence and liquid-column sweeping, are proposed and implemented. Experiment results show that the SmartPin is promising in the area of patterning of large area organic electronics. Besides the experimental research, computational fluid dynamics (CFD) simulation of the liquid dispensing process has been done by utilizing GAMBIT and FLUENT, which are state-of-the-art computer programs for modeling fluid flow and heat transfer in complex geometries. The CFD simulation results, validated by experimental results, offer a guide to the design of control system for different tasks of liquid dispensation, such as fabrication of protein microarray
Experimental investigation of emission from a light duty diesel engine utilizing urea spray SCR system
Stringent pollutant regulations on diesel-powered vehicles have resulted in the development of new
technologies to reduce emission of nitrogen oxides (NOx). The urea Selective Catalyst Reduction (SCR) system
and Lean NOx Trap (LNT) have become the two promising solutions to this problem. Whilst the LNT results in a
fuel penalty due to periodic regeneration, the SCR system with aqueous urea solution or ammonia gas
reductants could provide a better solution with higher NOx reduction efficiency.
This thesis describes an experimental investigation which has been designed for comparing the effect NOx
abatement of a SCR system with AdBlue urea spray and ammonia gas at 5% and 4% concentration. For this
study, a SCR exhaust system comprising of a diesel particulate filter (DPF), a diesel oxidation catalyst (DOC) and
SCR catalysts was tested on a steady state, direct injection 1998 cc diesel engine. It featured an expansion can,
nozzle and diffuser arrangement for a controlled flow profile for CFD model validation. Four different lengths
of SCR catalyst were tested for a space velocity study. Chemiluminescence (CLD) based ammonia analysers
have been used to provide high resolution NO, NO2 and NH3 measurements across the SCR exhaust system. By
measuring at the exit of the SCR bricks, the NO and NO2 profiles within the bricks were found. Comparison of
the measurements between spray and gas lead to insights of the behaviour of the droplets upstream and
within the SCR bricks.
From the analysis, it was deduced that around half to three quarters of the droplets from the urea spray
remain unconverted at the entry of the first SCR brick. Approximately 200 ppm of potential ammonia was
released from the urea spray in the first SCR brick to react with NOx. The analysis also shows between 10 to
100 ppm of potential ammonia survived through the first brick in droplet form for cases from NOx-matched
spray input to excess spray. Measurements show NOx reduction was complete after the second SCR bricks.
Experimental and CFD prediction showed breakthrough of all species for the short brick with gas injection due
to the high space velocity. The long brick gas cases predictions gave reasonable agreement with experimental
results. NO2 conversion efficiency was found higher than NO which contradicts with the fast SCR reaction
kinetics.
Transient response was observed in both cases during the NOx reduction, ammonia absorption and desorption process. From the transient analysis an estimate of the ammonia storage capacity of the bricks was derived.
The amount of ammonia slippage was obtained through numerical integration of the ammonia slippage curve
using an excel spreadsheet. Comparing the time constant for the spray and gas cases, showed a slightly faster
time response from the gas for both NOx reduction and ammonia slippage
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