Abstract: We have measured the pressure drop and convective
heat transfer coefficient of water – based AL(25nm),AL2O3(30nm)
and CuO(50nm) Nanofluids flowing through a uniform heated
circular tube in the fully developed laminar flow regime. The
experimental results show that the data for Nanofluids friction factor
show a good agreement with analytical prediction from the Darcy's
equation for single-phase flow. After reducing the experimental
results to the form of Reynolds, Rayleigh and Nusselt numbers. The
results show the local Nusselt number and temperature have
distribution with the non-dimensional axial distance from the tube
entry. Study decided that thenNanofluid as Newtonian fluids through
the design of the linear relationship between shear stress and the rate
of stress has been the study of three chains of the Nanofluid with
different concentrations and where the AL, AL2O3 and CuO – water
ranging from (0.25 - 2.5 vol %). In addition to measuring the four
properties of the Nanofluid in practice so as to ensure the validity of
equations of properties developed by the researchers in this area and
these properties is viscosity, specific heat, and density and found that
the difference does not exceed 3.5% for the experimental equations
between them and the practical. The study also demonstrated that the
amount of the increase in heat transfer coefficient for three types of
Nano fluid is AL, AL2O3, and CuO – Water and these ratios are
respectively (45%, 32%, 25%) with insulation and without insulation
(36%, 23%, 19%), and the statement of any of the cases the best
increase in heat transfer has been proven that using insulation is
better than not using it. I have been using three types of Nano
particles and one metallic Nanoparticle and two oxide Nanoparticle
and a statement, whichever gives the best increase in heat transfer.
Abstract: In this paper, many techniques for blind identification of moving average (MA) process are presented. These methods utilize third- and fourth-order cumulants of the noisy observations of the system output. The system is driven by an independent and identically distributed (i.i.d) non-Gaussian sequence that is not observed. Two nonlinear optimization algorithms, namely the Gradient Descent and the Gauss-Newton algorithms are exposed. An algorithm based on the joint-diagonalization of the fourth-order cumulant matrices (FOSI) is also considered, as well as an improved version of the classical C(q, 0, k) algorithm based on the choice of the Best 1-D Slice of fourth-order cumulants. To illustrate the effectiveness of our methods, various simulation examples are presented.
Abstract: The study investigates the mixing performance of
electrokinetically-driven power-law fluids in a microchannel
containing patterned trapezoid blocks. The effects of the geometry
parameters of the patterned trapezoid blocks and the flow behavior
index in the power-law model on the mixing efficiency within the
microchannel are explored. The results show that the mixing efficiency
can be improved by increasing the width of the blocks and extending
the length of upper surface of the blocks. In addition, the results show
that the mixing efficiency increases with an increasing flow behavior
index. Furthermore, it is shown that a heterogeneous patterning of the
zeta potential on the upper surfaces of the trapezoid blocks prompts
the formation of local flow recirculations, and therefore improves the
mixing efficiency. Consequently, it is shown that the mixing
performance improves with an increasing magnitude of the
heterogeneous surface zeta potential.
Abstract: The parametrical study of Shrouded Contra-rotating
Rotor was done in this paper based on 2D axisymmetric simulations.
The calculations were made with an actuator disk as double rotor
model. It objects to explore and quantify the effects of different shroud
geometry parameters mainly using the performance of power loading
(PL), which could evaluate the whole propulsion system capability as
5 Newtontotal thrust generationfor hover demand. The numerical
results show that:The increase of nozzle radius is desired but limited
by the flow separation, its optimal design is around 1.15 times rotor
radius, the viscosity effects greatly constraint the influence of nozzle
shape, the divergent angle around 10.5° performs best for chosen
nozzle length;The parameters of inlet such as leading edge curvature,
radius and internal shape do not affect thrust great but play an
important role in pressure distribution which could produce most part
of shroud thrust, they should be chosen according to the reduction of
adverse pressure gradients to reduce the risk of boundary separation.
Abstract: In this article, we aim to discuss the formulation of two explicit group iterative finite difference methods for time-dependent two dimensional Burger-s problem on a variable mesh. For the non-linear problems, the discretization leads to a non-linear system whose Jacobian is a tridiagonal matrix. We discuss the Newton-s explicit group iterative methods for a general Burger-s equation. The proposed explicit group methods are derived from the standard point and rotated point Crank-Nicolson finite difference schemes. Their computational complexity analysis is discussed. Numerical results are given to justify the feasibility of these two proposed iterative methods.
Abstract: In order to realize long-lived electric propulsion
systems, we have been investigating an electrodeless plasma thruster.
In our concept, a helicon plasma is accelerated by the magnetic nozzle
for the thrusts production. In addition, the electromagnetic thrust can
be enhanced by the additional radio-frequency rotating electric field
(REF) power in the magnetic nozzle. In this study, a direct
measurement of the electromagnetic thrust and a probe measurement
have been conducted using a laboratory model of the thruster under the
condition without the REF power input. Fromthrust measurement, it is
shown that the thruster produces a sub-milli-newton order
electromagnetic thrust force without the additional REF power. The
thrust force and the density jump are observed due to the discharge
mode transition from the inductive coupled plasma to the helicon wave
excited plasma. The thermal thrust is theoretically estimated, and the
total thrust force, which is a sum of the electromagnetic and the
thermal thrust force and specific impulse are calculated to be up to 650
μN (plasma production power of 400 W, Ar gas mass flow rate of 1.0
mg/s) and 210 s (plasma production power of 400 W, Ar gas mass flow
rate of 0.2 mg/s), respectively.
Abstract: Double-diffusive natural convection in an open top
square cavity and heated from the side is studied numerically.
Constant temperatures and concentration are imposed along the right
and left walls while the heat balance at the surface is assumed to obey
Newton-s law of cooling. The finite difference method is used to
solve the dimensionless governing equations. The numerical results
are reported for the effect of Marangoni number, Biot number and
Prandtl number on the contours of streamlines, temperature and
concentration. The predicted results for the average Nusselt number
and Sherwood number are presented for various parametric
conditions. The parameters involved are as follows; the thermal
Marangoni number, 0 ≤ MaT ≤1000 , the solutal Marangoni number,
0 1000 c ≤ Ma ≤ , the Biot number, 0 ≤ Bi ≤ 6 , Grashof number,
5 Gr = 10 and aspect ratio 1. The study focused on both flows; thermal
dominated, N = 0.8 , and compositional dominated, N = 1.3 .
Abstract: This paper presents a method to estimate load profile
in a multiple power flow solutions for every minutes in 24 hours per
day. A method to calculate multiple solutions of non linear profile is
introduced. The Power System Simulation/Engineering (PSS®E) and
python has been used to solve the load power flow. The result of this
power flow solutions has been used to estimate the load profiles for
each load at buses using Independent Component Analysis (ICA)
without any knowledge of parameter and network topology of the
systems. The proposed algorithm is tested with IEEE 69 test bus
system represents for distribution part and the method of ICA has
been programmed in MATLAB R2012b version. Simulation results
and errors of estimations are discussed in this paper.
Abstract: This paper describes an experimental investigation of
the drying behavior and conditions of rosehip in a convective
cyclone-type dryer. Drying experiments were conducted at air inlet
temperatures of 50, 60 and 70 o C and air velocities of 0.5, 1 and 1.5
ms–1. The parametric values obtained from the experiments were
fitted to the Newton mathematical models. Consequently, the drying
model developed by Newton model showed good agreement with the
data obtained from the experiments. Concluding, it was obtained that;
(i) the temperature is the major effect on the drying process, (ii) air
velocity has low effect on the drying of rosehip, (iii) the C-vitamin is
observed to change according to the temperature, moisture, drying
time and flow types. The changing ratio is found to be in the range of
0.70-0.74.
Abstract: In-core memory requirement is a bottleneck in solving
large three dimensional Navier-Stokes finite element problem
formulations using sparse direct solvers. Out-of-core solution
strategy is a viable alternative to reduce the in-core memory
requirements while solving large scale problems. This study
evaluates the performance of various out-of-core sequential solvers
based on multifrontal or supernodal techniques in the context of
finite element formulations for three dimensional problems on a
Windows platform. Here three different solvers, HSL_MA78,
MUMPS and PARDISO are compared. The performance of these
solvers is evaluated on a 64-bit machine with 16GB RAM for finite
element formulation of flow through a rectangular channel. It is
observed that using out-of-core PARDISO solver, relatively large
problems can be solved. The implementation of Newton and
modified Newton's iteration is also discussed.
Abstract: This paper deals with the helical flow of a Newtonian
fluid in an infinite circular cylinder, due to both longitudinal and
rotational shear stress. The velocity field and the resulting shear
stress are determined by means of the Laplace and finite Hankel
transforms and satisfy all imposed initial and boundary conditions.
For large times, these solutions reduce to the well-known steady-state
solutions.
Abstract: The present paper considers the steady free
convection boundary layer flow of a viscoelastics fluid with constant
temperature in the presence of heat generation. The boundary layer
equations are an order higher than those for the Newtonian (viscous)
fluid and the adherence boundary conditions are insufficient to
determine the solution of these equations completely. The governing
boundary layer equations are first transformed into non-dimensional
form by using special dimensionless group. Computations are
performed numerically by using Keller-box method by augmenting
an extra boundary condition at infinity and the results are displayed
graphically to illustrate the influence of viscoelastic K, heat
generation γ , and Prandtl Number, Pr parameters on the velocity
and temperature profiles. The results of the surface shear stress in
terms of the local skin friction and the surface rate of heat transfer in
terms of the local Nusselt number for a selection of the heat
generation parameterγ (=0.0, 0.2, 0.5, 0.8, 1.0) are obtained and
presented in both tabular and graphical formats. Without effect of the
internal heat generation inside the fluid domain for which we take
γ = 0.0, the present numerical results show an excellent agreement
with previous publication.
Abstract: CFD simulations are carried out in arterial stenoses
with 48 % areal occlusion. Non-newtonian fluid model is selected for
the blood flow as the same problem has been solved before with
Newtonian fluid model. Studies on flow resistance with the presence
of surface irregularities are carried out. Investigations are also
performed on the pressure drop at various Reynolds numbers. The
present study revealed that the pressure drop across a stenosed artery
is practically unaffected by surface irregularities at low Reynolds
numbers, while flow features are observed and discussed at higher
Reynolds numbers.
Abstract: In the analysis of structures, the nonlinear effects due to large displacement, large rotation and materially-nonlinear are very important and must be considered for the reliable analysis. The non-linear fmite element analysis has potential as usable and reliable means for analyzing of civil structures with the availability of computer technology. In this research the large displacements and materially nonlinear behavior of shear wall is presented with developing of fmite element code using the standard Galerkin weighted residual formulation. Two-dimensional plane stress model was carried out to present the shear wall response. Total Lagangian formulation, which is computationally more effective, is used in the formulation of stiffness matrices and the Newton-Raphson method is applied for the solution of nonlinear transient equations. The details of the program formulation are highlighted and the results of the analyses are presented, along with a comparison of the response of the structure with Ansys software results. The presented model in this paper can be developed for nonlinear analysis of civil engineering structures with different material behavior and complicated geometry.
Abstract: Nowadays, there is little information, concerning the
heat shield systems, and this information is not completely reliable to
use in so many cases. for example, the precise calculation cannot be
done for various materials. In addition, the real scale test has two
disadvantages: high cost and low flexibility, and for each case we
must perform a new test. Hence, using numerical modeling program
that calculates the surface recession rate and interior temperature
distribution is necessary. Also, numerical solution of governing
equation for non-charring material ablation is presented in order to
anticipate the recession rate and the heat response of non-charring
heat shields. the governing equation is nonlinear and the Newton-
Rafson method along with TDMA algorithm is used to solve this
nonlinear equation system. Using Newton- Rafson method for
solving the governing equation is one of the advantages of the
solving method because this method is simple and it can be easily
generalized to more difficult problems. The obtained results
compared with reliable sources in order to examine the accuracy of
compiling code.
Abstract: This paper deals with rheological behavior of tomato
paste from the view point of time independent properties inclusive of
processing variables such as sample temperature which influence on
rheological properties as well as breaking temperature and
concentration which beside the rheological properties, influence on
the quality of final product. With this aim 10 tomato paste samples at
various concentrations (17-25%) and breaking temperatures (65-
85 C o ) have been produced. The experimental results showed tomato
paste behaves as a non-Newtonian semi-fluid which follows power
law model that consistency coefficient (K) is supposed function of
breaking temperature, concentration and sample temperature with
consideration to superimpose function.
Abstract: An enhanced particle swarm optimization algorithm
(PSO) is presented in this work to solve the non-convex OPF
problem that has both discrete and continuous optimization variables.
The objective functions considered are the conventional quadratic
function and the augmented quadratic function. The latter model
presents non-differentiable and non-convex regions that challenge
most gradient-based optimization algorithms. The optimization
variables to be optimized are the generator real power outputs and
voltage magnitudes, discrete transformer tap settings, and discrete
reactive power injections due to capacitor banks. The set of equality
constraints taken into account are the power flow equations while the
inequality ones are the limits of the real and reactive power of the
generators, voltage magnitude at each bus, transformer tap settings,
and capacitor banks reactive power injections. The proposed
algorithm combines PSO with Newton-Raphson algorithm to
minimize the fuel cost function. The IEEE 30-bus system with six
generating units is used to test the proposed algorithm. Several cases
were investigated to test and validate the consistency of detecting
optimal or near optimal solution for each objective. Results are
compared to solutions obtained using sequential quadratic
programming and Genetic Algorithms.
Abstract: The stability of Newtonian and Non-Newtonian extending films under local or global heating or cooling conditions are considered. The thickness-averaged mass, momentum and energy equations with convective and radiative heat transfer are derived, both for Newtonian and non-Newtonian fluids (Maxwell, PTT and Giesekus models considered). The stability of the system is explored using either eigenvalue analysis or transient simulations. The results showed that the influence of heating and cooling on stability strongly depends on the magnitude of the Peclet number. Examples of stabilization or destabilization of heating or cooling are shown for Pe
Abstract: Reentry trajectory optimization is a multi-constraints
optimal control problem which is hard to solve. To tackle it, we
proposed a new algorithm named CDEN(Constrained Differential
Evolution Newton-Raphson Algorithm) based on Differential Evolution(
DE) and Newton-Raphson.We transform the infinite dimensional
optimal control problem to parameter optimization which is finite
dimensional by discretize control parameter. In order to simplify
the problem, we figure out the control parameter-s scope by process
constraints. To handle constraints, we proposed a parameterless constraints
handle process. Through comprehensive analyze the problem,
we use a new algorithm integrated by DE and Newton-Raphson to
solve it. It is validated by a reentry vehicle X-33, simulation results
indicated that the algorithm is effective and robust.
Abstract: In this work, we derive two numerical schemes for
solving a class of nonlinear partial differential equations. The first
method is of second order accuracy in space and time directions, the
scheme is unconditionally stable using Von Neumann stability
analysis, the scheme produced a nonlinear block system where
Newton-s method is used to solve it. The second method is of fourth
order accuracy in space and second order in time. The method is
unconditionally stable and Newton's method is used to solve the
nonlinear block system obtained. The exact single soliton solution
and the conserved quantities are used to assess the accuracy and to
show the robustness of the schemes. The interaction of two solitary
waves for different parameters are also discussed.