Thermal and Fluid Sciences

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24 Οκτ 2013 (πριν από 3 χρόνια και 10 μήνες)

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Mechanical Engineering
Graduate Research Symposium
@ UCR

Mechanical Engineering Graduate Student Association


Thermal and Fluid Sciences


Air Quality Modeling


Advisor: Akula Venkatram,

Professor


Numerical 1
-
D Simulation of Internal Combustion Engines

Considering Entropy Level Changes


Oral
Presenter
:

Karim Alizad
, M.E. graduate student

Location
:

Engineering Building II 206

Time slot:

9
:

4
0


9
:

5
5 am

Abstract:
The internal combustion engine has evolved over the past
hundred years as the most important prime mover for various
applications.

Several related technologies have been developed to improve the
performance and efficiency of operation of the engine.

Improvements in computer technologies in the past 20 years have
provided engine researchers with powerful tools to optimize engine

design

and to meet increasingly stringent emission requirements.
Computational Fluid Dynamics, which is used in this research, is

one such tool that enables study of complex systems in great details.
In this research, writing a CFD code, Internal Combustion

Engines simulated considering entropy level changes, called
Non
-
Homentropic.




Combustion and Fire Research


Advisor: Shankar Mahalingam,

Professor


An investigation of laboratory scale
crown fire initiation in
shrubs

Oral
Presenter
:

Jesse Lozano1
, M.E.
graduate student

Co
-
author
s
:
Shankar
Mahalingam, and David R. Weise
,
Department
of Mechanical Engineering, University of California, Riverside
;

David Weise
,
Forest Fire Laboratory, Pacific Southwest Research
Station, USDA Forest Service

Location
:

Engineering Building II 206

Time slot:

9
:
5
5



10:

1
0

am

Abstra
ct
:
The influence of separation distance between crown fuel
matrices on the process of transition of surface fires to crown fires is
investigated experimentally. The laboratory experiments were

carried
-
roof
wind tunnel to ensure that flame generated buoyancy effects are not
impeded. The surface fire was initiated in a fuel bed comprised of
aspen (Populus tremuloides Michx) excelsior that

was evenly
0.10 m. Crown fuel matrices comprised of live chamise (Adenostoma
0.8 m width wire mesh frame at a height o
f 0.4 m from the surface
fuel bed. Crown separation distances in the horizontal direction
investigated range from 0.1 m to 0.3 m. Results show that for the
smaller crown fuel separation cases, the surface and crown fires
merge prior to ignition of a downwi
nd fuel matrix, but at larger crown
fuel separation distance, the fires separated, prior to ignition of the
downwind fuel matrix.




Environmental

Flow Modeling


Advisor: Marko Princevac, Assistant

Professor


Modeling and Parameterization of Superfog

Oral
Presenter
:

Christian Bartolome


C
o
-
author:
Marko Princevac, Akula Venkatram, and Shankar
Mahalingam
,
Department of Mechanical Engineering, University of
California at Riverside

Location
:

Engineering Building II 206

Time slot:

10: 10


10: 2
5 am

Abstract:
Land management techniques in wildland areas include
prescribed fires to promote biodiversity and reduce risk of sever
wildfires. The loss of life, numerous injuries, and millions of dollars
spent on litigation in motor vehicles accidents have resulted fr
om
smoke related visibility reduction from prescribed burns (Mobley
1989 and Twiley 2000). In the southern areas of the US, prescribed
fires in the winter season have special cases of visibility depletion to
less than 3 meters known as superfog (Achtemeie
r 2008).
Occurrences of superfog led to incidences on Interstate
-
4 in Florida
on January 9, 2008 and on the Interstate
-
10 in Mississippi on May
2008, where major car pileups happened. The need for
characterization and parameterization of favorable condit
ions that
lead to superfog has become of great importance. Land managers
will be able to prevent dangerous low visibility situations by planning
prescribed burns accordingly with the proper parameterizations.
Empirical relations on naturally occurring ad
vection fogs relate
visibility to the liquid water content (LWC) (Kunkel 1984 and Fisak


Mechanical Engineering
Graduate Research Symposium
@ UCR

Mechanical Engineering Graduate Student Association

2006). These relations suggest relatively large LWC approximately
6 [g/m3] that are thermodynamically difficult to achieve to reach
visibilities less than 3 meters. I
t has been hypothesized that
extremely hygroscopic cloud condensation nuclei (CCN), formed
during the smoldering phase in great numbers, can produce large
number of droplets smaller in size compared to naturally occurring
fogs. The result of this large nu
mber of small droplets is that a
feasible LWC can produce. Thermodynamic parcel model and
sensitivity study of various size distributions on the extinction
coefficient, LWC, and number densities of droplets will be presented
along with laboratory results.


Dispersion Measurements from a Ground Level Release using
Optical Fiber Sensors:

Water Channel Modeling


Oral Presenter:

Sam Pournazeri
, M.E. graduate student

Co
-
author
s
:
Marko Princevac and Akula Venkatram
,
Department of
Mechanical Engineering,
University of California, Riverside
;

Location
:

Engineering Building II 206

Time slot:

10:
2
5



10:

4
0

am

Abstract:
Air pollution dispersion over urban areas, especially from
sources near to the ground, is still a challenging problem. Therefore, a
new set o
f experiments on vertical, horizontal and downstream
dispersion from ground level releases has been done in the laboratory
for environmental flow modeling (LEFM). In this experiment a
fluorescent dye was released from a continuous point source at the
groun
d level. Flow velocity and concentrations were measured using
Particle Image Velocimetry (PIV) system and a newly designed
concentration measurement system which is capable of measuring the
point concentration with real time corrections of the background
c
oncentrations. This new technique prevents any light reflection and
self illumination which presented a bane to previously used planar
laser induced Fluorescence (PLIF) system which suffers from errors
associated with light attenuation. The results are giv
en for 3 different
surface friction velocities u and roughness length z
0

=0.01mm.


The results from this study indicate that ground level concentration
decays as
𝐶
𝑄

𝑥

1
.
8

where Q is the mass release rate and x is the
downstream distance from the source
. Also measurements show that
concentration profile related to vertical dispersion of pollutants
released in surface layer are no longer Gaussian, but

𝑐
𝑐
0
=
𝑒𝑥𝑝
(

𝑏
(
𝑧
𝜎
𝑧
)
1
.
5
)
, where c
0

represents the ground level
concentration and
𝜎
z

is the vertical plume spread. In addition to
above concentration measurements, horizontal spread of surface
released plumes is also investigated by visualization and
concentration measurement. Results on horizontal plume spread show
very good agreement wi
th Eckman Hypothesis (Eckman, 1994)
consistent with several field experiments including Prairie Grass
experiment (Barad 1958).

The future work would involve concentration measurements
associated with buoyant and non
-
buoyant release from near ground
source
s in urban areas.

References:

Barad, M.L., 1958. Project Prairie Grass, a field program in diffusion,
Vol. 1, Geophysics Research Paper No. 59. Air Force Cambridge
Research Center, Bedford, MA.

Eckman R.M., 1994. Re
-
examination of empirically derived fo
rmulas
for horizontal diffusion from surface sources. Atmospheric
Environment 28, 265
-
272


Computation
Information and
Design


Integrated Design and Manufacturing

Smart Tools


Advisor:
Venkatadriagram Sundararajan


Assistant Professor

Thomas Stahovich,
Associate

Professor


EEG signal classification for detecting the geometry of imagined
object

Oral pre
senter:
Ehsan Tarkesh Esfahani
, M.E. graduate student

Location
:

Engineering Building II 206

Time slot:

1
1
: 00


1
1
: 15 am

Abstract:

Brain computer interfaces creates a novel communication
channel from the brain to an output device bypassing conventional
motor output pathways of nerves and muscles. Any thought of
moving, rotating and imagination of three dimensional objects will
activat
e certain parts of the brain. This activation is a product of
millions of firing neurons within those regions of the brain.
Performing each of these activities will result in a specific pattern in


Mechanical Engineering
Graduate Research Symposium
@ UCR

Mechanical Engineering Graduate Student Association

the brain activity. The goal of all BCI systems is to detec
t the pattern
in brain signals and relate it to the subject thought or intention.
Currently noninvasive brain
-
computer interfaces are mostly based on
recording Electroencephalography (EEG) signals from multiple
electrodes placed on the scalp.

In the last t
wo decades there has been lots of effort to find the pattern
in EEG signals related to imaginary movements [1
-
3], and some
mental task such as multiplication problems or mental counting [4].
However less attention has been on classification of imaginary 3D

objects. The aim of this paper is to develop a computer interface that
uses EEG signals to classify imagined geometric objects. To do so a
portable Emotiv© neauroheadset will be used to record the EEG
activity of brain through 14 electrodes. The process o
f classifying the
EEG signals can be summarized as artifact removal (removing the
effect of muscle and eye movements), feature selection and
classification. The recording device and the process of the projects
are illustrated in Figure 1.


1. Anderson, C.

W., Stolz, E.A. and Shamsunder, S., 1995
“Discriminating mental tasks using EEG represented by AR models
“Proc. 17th Annual Int. Conf. of the IEEE Engineering in Medicine
and Biology Society (Montreal) pp 875

6

2. Lemm, S., Schafer, C. and Curio, G., 2004

“BCI competition
2003

data set III: probabilistic modeling of sensorimotor mu rhythms
for classification of imaginary hand movements IEEE Trans.”
Biomed. Eng. 51 1077

80

3. Millan, J.R. and Mourino, J., 2003 “Asynchronous BCI and local
neural classifiers:

an overview of the adaptive brain interface project”
IEEE Trans. Neural Syst. Rehabil. Eng. 11 159

61

4. Kubler, A., Kotchoubey, B., Kaiser, J., Wolpaw, J. R. and
Birbaumer, N., 2001 “Brain

computer communication: unlocking the
locked” Psychol. Bull. 127
358

75

Mechanics and Materials


Nano Mechanics and Materials


Advanced Material Processing and Synthesis


Advisor: Javier Garay,

Associate

Professor


Applications and Advantages of Current Activated Densification


Oral Presenter
:
Alexander Dupuy
, M.E.
graduate student

Location
:

Engineering Building II 206

Time slot:

1
1
:
15



1
1
:
30

am

Abstract:

The Current Activated Pressure Assisted Densification
(CAPAD) technique has shown great promise in efficiently
consolidating a wide range of materials systems
while simultaneously
preserving small grain sizes. Using controlled joule heating and
applied pressure, the CAPAD technique allows for a dramatic
decrease in processing time and temperature compared with more
traditional densification methods. This is part
icularly important for
processing nanocrystalline materials, which are known to have
significant advantages over materials with larger grain sizes. A review
of the CAPAD technique and its benefits will be presented.
Additionally, current work involving the

CAPAD techniques
application to a variety of material systems will be discussed. These
materials, which possess diverse structural, optical, ferroelectric,
ferromagnetic, and thermoelectric properties, are ideal for
demonstrating the versatility of the CA
PAD processing technique.



Growth of Large
-
Area Graphene Films from Metal
-
Carbon
Melts

Oral Presenter
:
Shaahin Amini
, M.E. graduate student

Co
-
author:
Javier Garay, Alexander A. Balandin, Reza Abbaschian
,
Department of Mechanical Engineering, University
of California at
Riverside
.

Location
:

Engineering Building II 206

Time slot:

11
:
3
0


11
:

4
5 am

Abstract:

We demonstrated a new method for the large
-
area
graphene growth, which can be developed into the scalable low
-
cost
high
-
throughput production technol
ogy. The method is based on
growing single
-
layer and few
-
layer graphene films from a molten
phase. It involves dissolving carbon atoms inside a molten metal
phase at a specified temperature and then allowing the dissolved
carbon to nucleate and grow on top

of the melt at lower temperature.


Mechanical Engineering
Graduate Research Symposium
@ UCR

Mechanical Engineering Graduate Student Association

The resulting graphene layers were subjected to detailed microscopic
and micro
-
Raman spectroscopic characterization, which confirmed
their high quality. The deconvolution of the Raman 2D band was used
to determine the num
ber of atomic planes in the resulting graphene
layers. Since graphene growth utilizes molten phase it is expected that
the proposed technique would simplify the chemical doping of
graphene.




Nano
Energy
and Heat Transfer in Solids



Advisor:
Chris Dames
,

Assistant Professor


Applications and Advantages of Current Activated Densification


Oral Presenter
:
Zhaojie Wang
, M.E. graduate student

Co
-
author:
Zhaojie Wang, Joseph Alaniz, Wanyoung Jang, Javier
Garay, Chris Dames
,
Department of Mechanical Engineering
,
University of California at Riverside
.

Location
:

Engineering Building II 206

Time slot:

1
1
:
45



12
:

00

am

Abstract:

Engineering bulk materials with nano
-
sized grains is an
effective strategy for reducing the thermal conductivity, due to the
increased
phonon scat
tering at the grain boundaries
1
.

It has recently
been shown that it is also possible to achieve an increased power
factor in the same material, leading to a significant increase in the
thermoelectric figure of merit
2,3,4,5,6,7,8
.
To better under
stand the
fundamental mechanisms of the thermal conductivity reduction, here
we focus on the effects of grain size and temperature on the thermal
conductivity of silicon w
ith grain sizes down to 50 nm.
We use a
Spark Plasma Sintering (SPS) technique to con
solidate the samples
from nanopowders at high pressure (~100 MPa) and high temperature
(~1200 C) over a short time scale (~450 sec)
9
. The thermal
conductivity is measured by a 3 omega method. At room
temperature the thermal conductivity of a Si sample wi
th 50 nm
grains is 5 times smaller than that of bulk silicon, with much larger
reductions seen at lower tempera
tures (e.g. 60X

reduction at 80 K).
These results are explained by a thermal model that accounts for the
additional phonon scattering at grain b
oundaries.

References:

[1] Bed Poudel, Qing Hao, et al., Science, 320, 634, (2008)

[2] Sabah K. Bux, Richard G. Blair, et al., Adv. Funct. Mater. 19,
2445
-
2452 (2009)

[3] A. J. Minnich, M. S. Dresselhaus, Z. F. Ren and G. Chen, Energy
Environ. Sci. 2,
466 (2009)

[4] M. S. Dresselhaus, G. Chen et al., Adv. Mater. 19, 1043
-
1053
(2007)

[5] Deyu Li, A. Majumdar, APL 83, 14 (2003)

[6] G. H. Zhu, H. Lee, et al., PRL 102, 196803 (2009)

[7] G. Joshi, H. Lee, et al., Nano Letters 8, 12, 4670 (2008)

[8] X. W. Wan
g, H. Lee, et al., Appl. Phys. Lett. 93, 193121 (2008)

[9] U. Anselmi
-
Tamburinia, b, S. Gennarib, J.E. Garaya and Z.A.
Munir, Materials Science and Engineering A, 394, 1
-
2, 139
-
148
(2005).