Abstract: Sediment loads transfer in hydraulic installations and their consequences for the O&M of modern canal systems is emerging as one of the most important considerations in hydraulic engineering projects apriticularly those which are inteded to feed the irrigation and draiange schemes of large command areas such as the Dez and Mogahn in Iran.. The aim of this paper is to investigate the applicability of the vortex tube as a viable means of extracting sediment loads entering the canal systems in general and the water inatke structures in particulars. The Western conveyance canal of the Dez Diversion weir which feeds the Karkheh Flood Plain in Sothwestern Dezful has been used as the case study using the data from the Dastmashan Hydrometric Station. The SHARC software has been used as an analytical framework to interprete the data. Results show that given the grain size D50 and the canal turbulence the adaption length from the beginning of the canal and after the diversion dam is estimated at 477 m, a point which is suitable for laying the vortex tube.
Abstract: Turbulent forced convection flow in a 2-dimensional channel over periodic grooves is numerically investigated. Finite volume method is used to study the effect of turbulence model. The range of Reynolds number varied from 10000 to 30000 for the ribheight to channel-height ratio (B/H) of 2. The downstream wall is heated by a uniform heat flux while the upstream wall is insulated. The investigation is analyzed with different types of nanoparticles such as SiO2, Al2O3, and ZnO, with water as a base fluid are used. The volume fraction is varied from 1% to 4% and the nanoparticle diameter is utilized between 20nm to 50nm. The results revealed 114% heat transfer enhancement compared to the water in a grooved channel by using SiO2 nanoparticle with volume fraction and nanoparticle diameter of 4% and 20nm respectively.
Abstract: In this study, a semi-cylinder obstacle placed in a
channel is handled to determine the effect of flow and heat transfer
around the obstacle. Both faces of the semi-cylinder are used in the
numerical analysis. First, the front face of the semi-cylinder is stated
perpendicular to flow, than the rear face is placed. The study is
carried out numerically, by using commercial software ANSYS 11.0.
The well-known κ-ε model is applied as the turbulence model.
Reynolds number is in the range of 104 to 105 and air is assumed as
the flowing fluid. The results showed that, heat transfer increased
approximately 15 % in the front faze case, while it enhanced up to 28
% in the rear face case.
Abstract: Direct numerical simulation (DNS) is used to study the evolution of a boundary layer that was laminar initially followed by separation and then reattachment owing to generation of turbulence. This creates a closed region of recirculation, known as the laminar-separation bubble. The present simulation emulates the flow environment encountered in a modern LP turbine blade, where a laminar separation bubble may occur on the suction surface. The unsteady, incompressible three-dimensional (3-D) Navier-Stokes (NS) equations have been solved over a flat plate in the Cartesian coordinates. The adverse pressure gradient, which causes the flow to separate, is created by a boundary condition. The separated shear layer undergoes transition through appearance of ╬ø vortices, stretching of these create longitudinal streaks. Breakdown of the streaks into small and irregular structures makes the flow turbulent downstream.
Abstract: One of the main issues in Computer Vision is to extract the movement of one or several points or objects of interest in an image or video sequence to conduct any kind of study or control process. Different techniques to solve this problem have been applied in numerous areas such as surveillance systems, analysis of traffic, motion capture, image compression, navigation systems and others, where the specific characteristics of each scenario determine the approximation to the problem. This paper puts forward a Computer Vision based algorithm to analyze fish trajectories in high turbulence conditions in artificial structures called vertical slot fishways, designed to allow the upstream migration of fish through obstructions in rivers. The suggested algorithm calculates the position of the fish at every instant starting from images recorded with a camera and using neural networks to execute fish detection on images. Different laboratory tests have been carried out in a full scale fishway model and with living fishes, allowing the reconstruction of the fish trajectory and the measurement of velocities and accelerations of the fish. These data can provide useful information to design more effective vertical slot fishways.
Abstract: The aim of the paper work is to investigate and predict
the static performance of journal bearing in turbulent flow condition
considering micropolar lubrication. The Reynolds equation has been
modified considering turbulent micropolar lubrication and is solved
for steady state operations. The Constantinescu-s turbulence model is
adopted using the coefficients. The analysis has been done for a
parallel and inertia less flow. Load capacity and friction factor have
been evaluated for various operating parameters.
Abstract: A numerical study on the turbulent flow and heat
transfer characteristics in the rectangular channel with different types
of baffles is carried out. The inclined baffles have the width of 19.8
cm, the square diamond type hole having one side length of 2.55 cm,
and the inclination angle of 5o. Reynolds number is varied between
23,000 and 57,000. The SST turbulence model is applied in the
calculation. The validity of the numerical results is examined by the
experimental data. The numerical results of the flow field depict that
the flow patterns around the different baffle type are entirely different
and these significantly affect the local heat transfer characteristics.
The heat transfer and friction factor characteristics are significantly
affected by the perforation density of the baffle plate. It is found that
the heat transfer enhancement of baffle type II (3 hole baffle) has the
best values.
Abstract: In mechanical and environmental engineering, mixed
convection is a frequently encountered thermal fluid phenomenon
which exists in atmospheric environment, urban canopy flows, ocean
currents, gas turbines, heat exchangers, and computer chip cooling
systems etc... . This paper deals with a numerical investigation of
mixed convection in a vertical heated channel. This flow results from
the mixing of the up-going fluid along walls of the channel with the
one issued from a flat nozzle located in its entry section. The fluiddynamic
and heat-transfer characteristics of vented vertical channels
are investigated for constant heat-flux boundary conditions, a
Rayleigh number equal to 2.57 1010, for two jet Reynolds number
Re=3 103 and 2104 and the aspect ratio in the 8-20 range. The system
of governing equations is solved with a finite volumes method and an
implicit scheme. The obtained results show that the turbulence and
the jet-wall interaction activate the heat transfer, as does the drive of
ambient air by the jet. For low Reynolds number Re=3 103, the
increase of the aspect Ratio enhances the heat transfer of about 3%,
however; for Re=2 104, the heat transfer enhancement is of about
12%. The numerical velocity, pressure and temperature fields are
post-processed to compute the quantities of engineering interest such
as the induced mass flow rate, and average Nusselt number, in terms
of Rayleigh, Reynolds numbers and dimensionless geometric
parameters are presented.
Abstract: Due to the three- dimensional flow pattern interacting with bed material, the process of local scour around bridge piers is complex. Modeling 3D flow field and scour hole evolution around a bridge pier is more feasible nowadays because the computational cost and computational time have significantly decreased. In order to evaluate local flow and scouring around a bridge pier, a completely three-dimensional numerical model, SSIIM program, was used. The model solves 3-D Navier-Stokes equations and a bed load conservation equation. The model was applied to simulate local flow and scouring around a bridge pier in a large natural river with four piers. Computation for 1 day of flood condition was carried out to predict the maximum local scour depth. The results show that the SSIIM program can be used efficiently for simulating the scouring in natural rivers. The results also showed that among the various turbulence models, the k-ω model gives more reasonable results.
Abstract: Wind catchers are traditional natural ventilation
systems attached to buildings in order to ventilate the indoor air. The
most common type of wind catcher is four sided one which is
capable to catch wind in all directions. CFD simulation is the perfect
way to evaluate the wind catcher performance. The accuracy of CFD
results is the issue of concern, so sensitivity analyses is crucial to
find out the effect of different settings of CFD on results. This paper
presents a series of 3D steady RANS simulations for a generic
isolated four-sided wind catcher attached to a room subjected to wind
direction ranging from 0º to 180º with an interval of 45º. The CFD
simulations are validated with detailed wind tunnel experiments. The
influence of an extensive range of computational parameters is
explored in this paper, including the resolution of the computational
grid, the size of the computational domain and the turbulence model.
This study found that CFD simulation is a reliable method for wind
catcher study, but it is less accurate in prediction of models with non
perpendicular wind directions.
Abstract: In this paper, three dimensional flow characteristic was
presented by a revision of an impeller of an axial turbo fan for
improving the airflow rate and the static pressure. TO consider an
incompressible steady three-dimensional flow, the RANS equations
are used as the governing equations, and the standard k-ε turbulence
model is chosen. The pitch angles of 44°, 54°, 59°, and 64° are
implemented for the numerical model. The numerical results show that
airflow rates of each pitch angle are 1,175 CMH, 1,270 CMH, 1,340
CMH, and 800 CMH, respectively. The difference of the static
pressure at impeller inlet and outlet are 120 Pa, 214 Pa, 242 Pa, and 60
Pa according to respective pitch angles. It means that the 59° of the
impeller pitch angle is optimal to improve the airflow rate and the
static pressure.
Abstract: Education, as the most important resource in any country, has multiplying effects on all facets of development in a society. The new social realities, particularly the interplay between democratization of education; unprecedented developments in IT sector; emergence of knowledge society, liberalization of economy and globalization have greatly influenced the educational process of all nations. This turbulence entails upon education to undergo dramatic changes to keep up with the new expectations. Growth of entrepreneurship among Indian women is highly important for empowering them and this is highly essential for socio-economic development of a society. Unfortunately in India there is poor acceptance of entrepreneurship among women as unfounded myths and fears restrain them to be enterprising. To remove these inhibitions, education system needs to be re-engineered to make entrepreneurship more acceptable. This paper empirically analyses the results of a survey done on around 500 female graduates in North India to measure and evaluate various entrepreneurial traits present in them. A formative model has been devised in this context, which should improve the teaching-learning process in our education system, which can lead to sustainable growth of women entrepreneurship in India.
Abstract: The flow field around a flat plate of infinite span has
been investigated for several values of the angle of attack. Numerical
predictions have been compared to experimental measurements, in
order to examine the effect of turbulence model and grid resolution
on the resultant aerodynamic forces acting on the plate. Also the
influence of the free-stream turbulence intensity, at the entrance of
the computational domain, has been investigated. A full campaign of
simulations has been conducted for three inclination angles (9°, 15°
and 30°), in order to obtain some practical guidelines to be used for
the simulation of the flow field around inclined plates and discs.
Abstract: A pressure-based implicit procedure to solve Navier-
Stokes equations on a nonorthogonal mesh with collocated finite
volume formulation is used to simulate flow around the smart and
conventional flaps of spoiler under the ground effect. Cantilever
beam with uniformly varying load with roller support at the free end
is considered for smart flaps. The boundedness criteria for this
procedure are determined from a Normalized Variable diagram
(NVD) scheme. The procedure incorporates es the k -ε eddyviscosity
turbulence model. The method is first validated against
experimental data. Then, the algorithm is applied for turbulent
aerodynamic flows around a spoiler section with smart and
conventional flaps for different attack angle, flap angle and ground
clearance where the results of two flaps are compared.
Abstract: Preliminary results for a new flat plate test
facility are presented here in the form of Computational Fluid Dynamics (CFD), flow visualisation, pressure measurements and thermal anemometry. The results from the CFD and flow
visualisation show the effectiveness of the plate design, with the trailing edge flap anchoring the stagnation point on the working surface and reducing the extent of the leading edge separation. The flow visualization technique demonstrates the
two-dimensionality of the flow in the location where the
thermal anemometry measurements are obtained.
Measurements of the boundary layer mean velocity profiles compare favourably with the Blasius solution, thereby allowing for comparison of future measurements with the
wealth of data available on zero pressure gradient Blasius
flows. Results for the skin friction, boundary layer thickness,
frictional velocity and wall shear stress are shown to agree well with the Blasius theory, with a maximum experimental deviation from theory of 5%. Two turbulence generating grids
have been designed and characterized and it is shown that the turbulence decay downstream of both grids agrees with established correlations. It is also demonstrated that there is
little dependence of turbulence on the freestream velocity.
Abstract: In hypersonic environments, the aerothermal effect
makes it difficult for the optical side windows of optical guided
missiles to withstand high heat. This produces cracking or breaking,
resulting in an inability to function. This study used computational
fluid mechanics to investigate the external cooling jet conditions of
optical side windows. The turbulent models k-ε and k-ω were
simulated. To be in better accord with actual aerothermal
environments, a thermal radiation model was added to examine
suitable amounts of external coolants and the optical window
problems of aero-thermodynamics. The simulation results indicate that
when there are no external cooling jets, because airflow on the optical
window and the tail groove produce vortices, the temperatures in these
two locations reach a peak of approximately 1600 K. When the
external cooling jets worked at 0.15 kg/s, the surface temperature of
the optical windows dropped to approximately 280 K. When adding
thermal radiation conditions, because heat flux dissipation was faster,
the surface temperature of the optical windows fell from 280 K to
approximately 260 K. The difference in influence of the different
turbulence models k-ε and k-ω on optical window surface temperature
was not significant.
Abstract: Atmospheric stability plays the most important role in
the transport and dispersion of air pollutants. Different methods are
used for stability determination with varying degrees of complexity.
Most of these methods are based on the relative magnitude of
convective and mechanical turbulence in atmospheric motions.
Richardson number, Monin-Obukhov length, Pasquill-Gifford
stability classification and Pasquill–Turner stability classification, are
the most common parameters and methods. The Pasquill–Turner
Method (PTM), which is employed in this study, makes use of
observations of wind speed, insolation and the time of day to classify
atmospheric stability with distinguishable indices. In this study, a
model is presented to determination of atmospheric stability
conditions using PTM. As a case study, meteorological data of
Mehrabad station in Tehran from 2000 to 2005 is applied to model.
Here, three different categories are considered to deduce the pattern
of stability conditions. First, the total pattern of stability classification
is obtained and results show that atmosphere is 38.77%, 27.26%,
33.97%, at stable, neutral and unstable condition, respectively. It is
also observed that days are mostly unstable (66.50%) while nights are
mostly stable (72.55%). Second, monthly and seasonal patterns are
derived and results indicate that relative frequency of stable
conditions decrease during January to June and increase during June
to December, while results for unstable conditions are exactly in
opposite manner. Autumn is the most stable season with relative
frequency of 50.69% for stable condition, whilst, it is 42.79%,
34.38% and 27.08% for winter, summer and spring, respectively.
Hourly stability pattern is the third category that points out that
unstable condition is dominant from approximately 03-15 GTM and
04-12 GTM for warm and cold seasons, respectively. Finally,
correlation between atmospheric stability and CO concentration is
achieved.
Abstract: Droplet size distributions in the cold spray of a fuel
are important in observed combustion behavior. Specification of
droplet size and velocity distributions in the immediate downstream
of injectors is also essential as boundary conditions for advanced
computational fluid dynamics (CFD) and two-phase spray transport
calculations. This paper describes the development of a new model to
be incorporated into maximum entropy principle (MEP) formalism
for prediction of droplet size distribution in droplet formation region.
The MEP approach can predict the most likely droplet size and
velocity distributions under a set of constraints expressing the
available information related to the distribution.
In this article, by considering the mechanisms of turbulence
generation inside the nozzle and wave growth on jet surface, it is
attempted to provide a logical framework coupling the flow inside the
nozzle to the resulting atomization process. The purpose of this paper
is to describe the formulation of this new model and to incorporate it
into the maximum entropy principle (MEP) by coupling sub-models
together using source terms of momentum and energy. Comparison
between the model prediction and experimental data for a gas turbine
swirling nozzle and an annular spray indicate good agreement
between model and experiment.
Abstract: This paper focuses on developing an integrated
reliable and sophisticated model for ultra large wind turbines And to
study the performance and analysis of vector control on large wind
turbines. With the advance of power electronics technology, direct
driven multi-pole radial flux PMSG (Permanent Magnet Synchronous
Generator) has proven to be a good choice for wind turbines
manufacturers. To study the wind energy conversion systems, it is
important to develop a wind turbine simulator that is able to produce
realistic and validated conditions that occur in real ultra MW wind
turbines. Three different packages are used to simulate this model,
namely, Turbsim, FAST and Simulink. Turbsim is a Full field wind
simulator developed by National Renewable Energy Laboratory
(NREL). The wind turbine mechanical parts are modeled by FAST
(Fatigue, Aerodynamics, Structures and Turbulence) code which is
also developed by NREL. Simulink is used to model the PMSG, full
scale back to back IGBT converters, and the grid.
Abstract: The objective of this research was to find the diffusion properties of vehicles on the road by using the V-Sphere Code. The diffusion coefficient and the size of the height of the wake were estimated with the LES option and the third order MUSCL scheme. We evaluated the code with the changes in the moments of Reynolds Stress along the mean streamline. The results show that at the leading part of a bluff body the LES has some advantages over the RNS since the changes in the strain rates are larger for the leading part. We estimated that the diffusion coefficient with the computed Reynolds stress (non-dimensional) was about 0.96 times the mean velocity.