Abstract: We report the results of an lattice Boltzmann
simulation of magnetohydrodynamic damping of sidewall convection
in a rectangular enclosure filled with a porous medium. In particular
we investigate the suppression of convection when a steady magnetic
field is applied in the vertical direction. The left and right vertical
walls of the cavity are kept at constant but different temperatures
while both the top and bottom horizontal walls are insulated. The
effects of the controlling parameters involved in the heat transfer and
hydrodynamic characteristics are studied in detail. The heat and mass
transfer mechanisms and the flow characteristics inside the enclosure
depended strongly on the strength of the magnetic field and Darcy
number. The average Nusselt number decreases with rising values of
the Hartmann number while this increases with increasing values of
the Darcy number.
Abstract: The control of commutation of switched reluctance
(SR) motor has nominally depended on a physical position detector.
The physical rotor position sensor limits robustness and increases
size and inertia of the SR drive system. The paper describes a method
to overcome these limitations by using magnetization characteristics
of the motor to indicate rotor and stator teeth overlap status. The
method is using active current probing pulses of same magnitude that
is used to simulate flux linkage in the winding being probed. A
microprocessor is used for processing magnetization data to deduce
rotor-stator teeth overlap status and hence rotor position. However,
the back-of-core saturation and mutual coupling introduces overlap
detection errors, hence that of commutation control. This paper
presents the concept of the detection scheme and the effects of backof
core saturation.
Abstract: To improve HSE standards, oil and gas industries are
interested in using remotely controlled and autonomous robots instead
of human workers on offshore platforms. In addition to earlier reason
this strategy would increase potential revenue, efficient usage of
work experts and even would allow operations in more remote areas.
This article is the presentation of a custom climbing robot, called
Walloid, designed for offshore platform topside automation. This 4
arms climbing robot with grippers is an ongoing project at University
of Oslo.
Abstract: In the present study, the pressure drop and laminar convection heat transfer characteristics of nanofluids in microchannel heat sink with square duct are numerically investigated. The water based nanofluids created with Al2O3 and CuO particles in four different volume fractions of 0%, 0.5%, 1%, 1.5% and 2% are used to analyze their effects on heat transfer and the pressure drop. Under the laminar, steady-state flow conditions, the finite volume method is used to solve the governing equations of heat transfer. Mixture Model is considered to simulate the nanofluid flow. For verification of used numerical method, the results obtained from numerical calculations were compared with the results in literature for both pure water and the nanofluids in different volume fractions. The distributions of the particles in base fluid are assumed to be uniform. The results are evaluated in terms of Nusselt number, the pressure drop and heat transfer enhancement. Analysis shows that the nanofluids enhance heat transfer while the Reynolds number and the volume fractions are increasing. The best overall enhancement was obtained at φ=%2 and Re=100 for CuO-water nanofluid.
Abstract: This paper presents Faults Forecasting System (FFS)
that utilizes statistical forecasting techniques in analyzing process
variables data in order to forecast faults occurrences. FFS is
proposing new idea in detecting faults. Current techniques used in
faults detection are based on analyzing the current status of the
system variables in order to check if the current status is fault or not.
FFS is using forecasting techniques to predict future timing for faults
before it happens. Proposed model is applying subset modeling
strategy and Bayesian approach in order to decrease dimensionality
of the process variables and improve faults forecasting accuracy. A
practical experiment, designed and implemented in Okayama
University, Japan, is implemented, and the comparison shows that
our proposed model is showing high forecasting accuracy and
BEFORE-TIME.
Abstract: The present work demonstrates the design and simulation of a fuzzy control of an air conditioning system at different pressures. The first order Sugeno fuzzy inference system is utilized to model the system and create the controller. In addition, an estimation of the heat transfer rate and water mass flow rate injection into or withdraw from the air conditioning system is determined by the fuzzy IF-THEN rules. The approach starts by generating the input/output data. Then, the subtractive clustering algorithm along with least square estimation (LSE) generates the fuzzy rules that describe the relationship between input/output data. The fuzzy rules are tuned by Adaptive Neuro-Fuzzy Inference System (ANFIS). The results show that when the pressure increases the amount of water flow rate and heat transfer rate decrease within the lower ranges of inlet dry bulb temperatures. On the other hand, and as pressure increases the amount of water flow rate and heat transfer rate increases within the higher ranges of inlet dry bulb temperatures. The inflection in the pressure effect trend occurs at lower temperatures as the inlet air humidity increases.
Abstract: In this paper, an analytical approach for free vibration
analysis of four edges simply supported rectangular Kirchhoff plates
is presented. The method is based on wave approach. From wave
standpoint vibration propagate, reflect and transmit in a structure.
Firstly, the propagation and reflection matrices for plate with simply
supported boundary condition are derived. Then, these matrices are
combined to provide a concise and systematic approach to free
vibration analysis of a simply supported rectangular Kirchhoff plate.
Subsequently, the eigenvalue problem for free vibration of plates is
formulated and the equation of plate natural frequencies is
constructed. Finally, the effectiveness of the approach is shown by
comparison of the results with existing classical solution.
Abstract: A numerical study has been carried out to investigate
the heat transfer by natural convection of nanofluid taking Cu as
nanoparticles and the water as based fluid in a three dimensional
annulus enclosure filled with porous media (silica sand) between two
horizontal concentric cylinders with 12 annular fins of 2.4mm
thickness attached to the inner cylinder under steady state conditions.
The governing equations which used are continuity, momentum and
energy equations under an assumptions used Darcy law and
Boussinesq-s approximation which are transformed to dimensionless
equations. The finite difference approach is used to obtain all the
computational results using the MATLAB-7. The parameters affected
on the system are modified Rayleigh number (10 ≤Ra*≤ 1000), fin
length Hf (3, 7 and 11mm), radius ratio Rr (0.293, 0.365 and 0.435)
and the volume fraction(0 ≤ ¤ò ≤ 0 .35). It was found that the
average Nusselt number depends on (Ra*, Hf, Rr and φ). The results
show that, increasing of fin length decreases the heat transfer rate and
for low values of Ra*, decreasing Rr cause to decrease Nu while for
Ra*
greater than 100, decreasing Rr cause to increase Nu and adding
Cu nanoparticles with 0.35 volume fraction cause 27.9%
enhancement in heat transfer. A correlation for Nu in terms of Ra*,
Hf and φ, has been developed for inner hot cylinder.
Abstract: A conjugate heat transfer for steady two-dimensional
mixed convection with magnetic hydrodynamic (MHD) flow of an
incompressible quiescent fluid over an unsteady thermal forming
stretching sheet has been studied. A parameter, M, which is used to
represent the dominance of the magnetic effect has been presented in
governing equations. The similar transformation and an implicit
finite-difference method have been used to analyze the present
problem. The numerical solutions of the flow velocity distributions,
temperature profiles, the wall unknown values of f''(0) and '(θ (0) for
calculating the heat transfer of the similar boundary-layer flow are
carried out as functions of the unsteadiness parameter (S), the Prandtl
number (Pr), the space-dependent parameter (A) and
temperature-dependent parameter (B) for heat source/sink and the
magnetic parameter (M). The effects of these parameters have also
discussed. At the results, it will produce greater heat transfer effect
with a larger Pr and M, S, A, B will reduce heat transfer effects. At
last, conjugate heat transfer for the free convection with a larger G has
a good heat transfer effect better than a smaller G=0.
Abstract: A numerical study is presented on convective heat transfer in enclosures. The results are addressed to automotive headlights containing new-age light sources like Light Emitting Diodes (LED). The heat transfer from the heat source (LED) to the enclosure walls is investigated for mixed convection as interaction of the forced convection flow from an inlet and an outlet port and the natural convection at the heat source. Unlike existing studies, inlet and outlet port are thermally coupled and do not serve to remove hot fluid. The input power of the heat source is expressed by the Rayleigh number. The internal position of the heat source, the aspect ratio of the enclosure, and the inclination angle of one wall are varied. The results are given in terms of the global Nusselt number and the enclosure Nusselt number that characterize the heat transfer from the source and from the interior fluid to the enclosure walls, respectively. It is found that the heat transfer from the source to the fluid can be maximized if the source is placed in the main stream from the inlet to the outlet port. In this case, the Reynolds number and heat source position have the major impact on the heat transfer. A disadvantageous position has been found where natural and forced convection compete each other. The overall heat transfer from the source to the wall increases with increasing Reynolds number as well as with increasing aspect ratio and decreasing inclination angle. The heat transfer from the interior fluid to the enclosure wall increases upon decreasing the aspect ratio and increasing the inclination angle. This counteracting behaviour is caused by the variation of the area of the enclosure wall. All mixed convection results are compared to the natural convection limit.
Abstract: This paper proposed a nonlinear model predictive
control (MPC) method for the control of gantry crane. One of the main
motivations to apply MPC to control gantry crane is based on its
ability to handle control constraints for multivariable systems. A
pre-compensator is constructed to compensate the input nonlinearity
(nonsymmetric dead zone with saturation) by using its inverse
function. By well tuning the weighting function matrices, the control
system can properly compromise the control between crane position
and swing angle. The proposed control algorithm was implemented for
the control of gantry crane system in System Control Lab of University
of Technology, Sydney (UTS), and achieved desired experimental
results.
Abstract: This paper describes the shape optimization of impeller
blades for a anti-heeling bidirectional axial flow pump used in ships.
In general, a bidirectional axial pump has an efficiency much lower
than the classical unidirectional pump because of the symmetry of the
blade type. In this paper, by focusing on a pump impeller, the shape of
blades is redesigned to reach a higher efficiency in a bidirectional axial
pump. The commercial code employed in this simulation is CFX v.13.
CFD result of pump torque, head, and hydraulic efficiency was
compared. The orthogonal array (OA) and analysis of variance
(ANOVA) techniques and surrogate model based optimization using
orthogonal polynomial, are employed to determine the main effects
and their optimal design variables. According to the optimal design,
we confirm an effective design variable in impeller blades and explain
the optimal solution, the usefulness for satisfying the constraints of
pump torque and head.
Abstract: In this study the behavior of interlaminar fracture of
carbon-epoxy thermoplastic laminated composite is investigated
numerically and experimentally. Tests are performed with Arcan
specimens. Testing with Arcan specimen gives the opportunity of
utilizing just one kind of specimen for extracting fracture properties
for mode I, mode II and different mixed mode ratios of materials with
exerting load via different loading angles. Variation of loading angles
in range of 0-90° made possible to achieve different mixed mode
ratios. Correction factors for various conditions are obtained from
ABAQUS 2D finite element models which demonstrate the finite
shape of Arcan specimens used in this study. Finally, applying the
correction factors to critical loads obtained experimentally, critical
interlaminar fracture toughness of this type of carbon- epoxy
composite has been attained.
Abstract: The present work is concerned with the effect of turning process parameters (cutting speed, feed rate, and depth of cut) and distance from the center of work piece as input variables on the chip micro-hardness as response or output. Three experiments were conducted; they were used to investigate the chip micro-hardness behavior at diameter of work piece for 30[mm], 40[mm], and 50[mm]. Response surface methodology (R.S.M) is used to determine and present the cause and effect of the relationship between true mean response and input control variables influencing the response as a two or three dimensional hyper surface. R.S.M has been used for designing a three factor with five level central composite rotatable factors design in order to construct statistical models capable of accurate prediction of responses. The results obtained showed that the application of R.S.M can predict the effect of machining parameters on chip micro-hardness. The five level factorial designs can be employed easily for developing statistical models to predict chip micro-hardness by controllable machining parameters. Results obtained showed that the combined effect of cutting speed at it?s lower level, feed rate and depth of cut at their higher values, and larger work piece diameter can result increasing chi micro-hardness.
Abstract: Cooktop burners are widely used nowadays. In
cooktop burner design, nozzle efficiency and greenhouse
gas(GHG) emissions mainly depend on heat transfer from the
premixed flame to the impinging surface. This is a complicated
issue depending on the individual and combined effects of various
input combustion variables. Optimal operating conditions for
sustainable burner design were rarely addressed, especially in the
case of multiple slot-jet burners. Through evaluating the optimal
combination of combustion conditions for a premixed slot-jet
array, this paper develops a practical approach for the sustainable
design of gas cooktop burners. Efficiency, CO and NOx emissions
in respect of an array of slot jets using premixed flames were
analysed. Response surface experimental design were applied to
three controllable factors of the combustion process, viz.
Reynolds number, equivalence ratio and jet-to-vessel distance.
Desirability Function Approach(DFA) is the analytic technique
used for the simultaneous optimization of the efficiency and
emission responses.
Abstract: A transient finite element model has been developed
to study the heat transfer and fluid flow during spot Gas Tungsten
Arc Welding (GTAW) on stainless steel. Temperature field, fluid
velocity and electromagnetic fields are computed inside the cathode,
arc-plasma and anode using a unified MHD formulation. The
developed model is then used to study the influence of different
helium-argon gas mixtures on both the energy transferred to the
workpiece and the time evolution of the weld pool dimensions. It is
found that the addition of helium to argon increases the heat flux
density on the weld axis by a factor that can reach 6.5. This induces
an increase in the weld pool depth by a factor of 3. It is also found
that the addition of only 10% of argon to helium decreases
considerably the weld pool depth, which is due to the electrical
conductivity of the mixture that increases significantly when argon is
added to helium.
Abstract: This study deals with Computational Fluid Dynamics
(CFD) studies of the interactions between the air flow and louvered
fins which equipped the automotive heat exchangers. 3D numerical
simulation results are obtained by using the ANSYS Fluent 13.0 code
and compared to experimental data. The paper studies the effect of
louver angle and louver pitch geometrical parameters, on overall
thermal hydraulic performances of louvered fins.
The comparison between CFD simulations and experimental data
show that established 3-D CFD model gives a good agreement. The
validation agrees, with about 7% of deviation respectively of friction
and Colburn factors to experimental results. As first, it is found that
the louver angle has a strong influence on the heat transfer rate. Then,
louver angle and louver pitch variation of the louvers and their effects
on thermal hydraulic performances are studied. In addition to this
study, it is shown that the second half of the fin takes has a
significant contribution on pressure drop increase without any
increase in heat transfer.
Abstract: Most CT reconstruction system x-ray computed
tomography (CT) is a well established visualization technique in
medicine and nondestructive testing. However, since CT scanning
requires sampling of radiographic projections from different viewing
angles, common CT systems with mechanically moving parts are too
slow for dynamic imaging, for instance of multiphase flows or live
animals. A large number of X-ray projections are needed to
reconstruct CT images, so the collection and calculation of the
projection data consume too much time and harmful for patient. For
the purpose of solving the problem, in this study, we proposed a
method for tomographic reconstruction of a sample from a limited
number of x-ray projections by using linear interpolation method. In
simulation, we presented reconstruction from an experimental x-ray
CT scan of a Aluminum phantom that follows to two steps: X-ray
projections will be interpolated using linear interpolation method and
using it for CT reconstruction based upon Ordered Subsets
Expectation Maximization (OSEM) method.
Abstract: In today-s era of plasma and laser cutting, machines using oxy-acetylene flame are also meritorious due to their simplicity and cost effectiveness. The objective to devise a Computer controlled Oxy-Fuel profile cutting machine arose from the increasing demand for metal cutting with respect to edge quality, circularity and lesser formation of redeposit material. The System has an 8 bit micro controller based embedded system, which assures stipulated time response. A new window based Application software was devised which takes a standard CAD file .DXF as input and converts it into numerical data required for the controller. It uses VB6 as a front end whereas MS-ACCESS and AutoCAD as back end. The system is designed around AT89C51RD2, powerful 8 bit, ISP micro controller from Atmel and is optimized to achieve cost effectiveness and also maintains the required accuracy and reliability for complex shapes. The backbone of the system is a cleverly designed mechanical assembly along with the embedded system resulting in an accuracy of about 10 microns while maintaining perfect linearity in the cut. This results in substantial increase in productivity. The observed results also indicate reduced inter laminar spacing of pearlite with an increase in the hardness of the edge region.
Abstract: A 2-Degrees of freedom powered prosthetic wrist
actuator has been proposed that can provide the Abduction/Adduction
& Flexion/Extension movements of the human wrist. The basic
structure of the actuator is a Ball and Socket joint and the force is
transmitted from the DC geared servo motors to the joint through the
Bowden cables. The proposed design is capable of providing the
required DOF in both axes i.e. 85° & 90° in flexion extension axis.
The size and weight of the actuator lies within the ranges of an
average human being-s wrist.