WSEAS Transactions on
Fluid Mechanics

2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | Pre-2008

Print ISSN: 1790-5087
E-ISSN: 2224-347X

Volume 11, 2016

Notice: As of 2014 and for the forthcoming years, the publication frequency/periodicity of WSEAS Journals is adapted to the 'continuously updated' model. What this means is that instead of being separated into issues, new papers will be added on a continuous basis, allowing a more regular flow and shorter publication times. The papers will appear in reverse order, therefore the most recent one will be on top.

Volume 11, 2016

Title of the Paper: Binormal Evolution of Curves with Prescribed Velocity

Authors: O. J. Garay, A. Pampano

Abstract: At the end of the 19th century, Kirchhoff studied dynamical problems involving vortex flows of inviscid incompressible fluids focusing on flows having the shape of a vortex tube (vortex filaments). In 1906, Da Rios, a student of Levi-Civita, analyzed the motion of a vortex filament and obtained the remarkable equation describing its evolution, which, under mild conditions, is equivalent to the so called binormal evolution equation. Motivated by this, in this work we use fundamental facts of the theory of submanifolds to analyze the evolution of curves under binormal flows with curvature dependent velocity in pseudo-riemannian 3-space forms. The compatibility conditions for these systems are given by the Gauss-Codazzi equations, which here are expressed with respect to a geodesic coordinate system in terms of the Frenet curvatures of the evolving curves. Then, an existence result is derived from the Fundamental Theorem of submanifolds. Moreover, we show the connection between travelling wave solutions of the Gauss-Codazzi equations and the Frenet-Serret dynamics of curves. In fact, travelling wave solutions of the Gauss-Codazzi equations are shown to lead to the Euler-Lagrange equations of extremal curves for curvature dependent energies with a penalty on the total torsion and the length (generalized Kirchhoff centerlines). A characterization of generalized Kirchhoff centerlines in terms of Killing vector fields allows us to construct binormal evolution surfaces with prescribed velocity by using them as initial conditions for the evolution. Binormal surfaces obtained in this way evolve without change in shape. Finally, we particularize the previous findings to three significant cases which give rise to Hasimoto surfaces, Hopf tubes, and constant mean curvature surfaces.

Keywords: binormal flow, curve evolution, Frenet-Serret dynamics, extremal curves, submanifolds, real space forms

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #14, pp. 112-120

Title of the Paper: Investigation on the Detection of Water Leaks in Small-Diameter Polyethylene Pipes Using Acoustic Emission Signals

Authors: Alberto Martini, Marco Troncossi, Alessandro Rivola

Abstract: Active control of water losses is an essential strategy to increase the efficiency of urban water supply systems. This work deals with the early detection of leaks occurring in small-diameter service pipes of water distribution networks. Preliminary experiments were conducted in a test facility to assess the sensitivity of Acoustic Emission methods to leaking water flows. Acoustic Emission measurements were performed on an unburied polyethylene pipe with artificially generated leaks. A good correlation between several monitored parameters and the characteristics of the examined leaks could be identified.

Keywords: Leak detection, Acoustic Emission, service pipe, water supply network

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #13, pp. 106-111

Title of the Paper: Active Control of Axisymmetric Flow with Two Synthetic Jets Worked in Bifurcated Mode

Authors: Petra DanĨová, Tomáš Vít, Darina Jašíková, Jan Novosád

Abstract: This paper deals with the experimental research of the effect of two synthetic jets worked in the bifurcated mode used for control of an axisymmetric air jet. First, the control synthetic jets were measured alone. After an adjustment, the primary axisymmetric jet was added in to the system. For comparison, the primary flow without synthetic jets control was also measured. All experiments were performed using PIV method whereby the synchronization between synthetic jets and PIV system was necessary to do. This work continues the investigation described in [11].

Keywords: Synthetic jet, primary flow, unforced flow, flow control, pulse modulation, PIV, synchronization

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #12, pp. 98-105

Title of the Paper: Modelling and Design of Microflow Sensors Based on Measuring of Temperature

Authors: Milan Adamek, Michaela Barinova, Dora Lapkova

Abstract: The paper presents the design and experimental experience with the gas flow measurement instrument for the range of (5 – 25) ml/hr. The aimed application area is in a biochemical laboratory for the study of reaction kinetic of sediments decomposition in waste water. The time-of- flight type of sensor with one upstream and one downstream temperature sensor has been chosen for the study. We explain the basic operation principles of the tiny flow measurement and the sensor structure. In the numerical model paragraph, we are describing the basic configuration model and the modelling results. As the three-dimensional simulation would be very time consuming process, we have simplified the simulation for only two-dimensional task. The presented diagrams are derived for different gases (air, nitrogen, carbon oxide and chlorine) and sensor tube materials, namely steel, copper, and plexi-glass. We present also the experimental set-up including the design and sensor parameters. The paragraph with experimental results and discussion on them illustrates the good correspondence with expected values. The paper concludes with the employment of designed gas flowmeter in the biochemical laboratory.

Keywords: flow measurement, calorimetric sensor, time of flight, heating power, mass and heat transfer, Femlab, flow tube, flow range

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #11, pp. 91-97

Title of the Paper: Adaptive Control of Fluid Inside CSTR Using Continuous-Time and Discrete-Time Identification Model and Different Control Configurations

Authors: Jiri Vojtesek, Petr Dostal

Abstract: An adaptive control is a kind of modern control methods with great theoretical background and various modifications. This control approach could be used for system with negative control properties such as nonlinearity, non-minimum phase behaviour etc. The adaptive control in this paper is based on the recursive identification of the external linear model as a linear representation of the originally nonlinear system. The control synthesis is based on the polynomial approach together with the spectral factorization and the pole-placement method. The identification model in the continuous-time uses differential filters and so called delta-models in the discrete-time. There were tested also two types of control configurations with the one degree-of-freedom (1DOF) that has controller only in the feedback part and with the two degrees-of-freedom (2DOF) where the controller is separated into two parts the first is in the feedback and the second is feedforward part of the control loop. Paper shows usability of this control approach by the simulations on the mathematical model of the continuous stirred-tank reactor with the cooling in the jacket as a typical nonlinear system with lumped parameters.

Keywords: Simulation, Mathematical Model, Adaptive control, Continuous-time model, Delta-model, Continuous Stirred-tank Reactor, 1DOF, 2DOF

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #10, pp. 81-90

Title of the Paper: Unsteady MHD Second Grade Fluids Flow in a Porous Medium with Ramped Wall Temperature

Authors: Zulkhibri Ismail, Ahmad Qushairi Mohamad, Ilyas Khan, Sharidan Shafie

Abstract: In this paper, the unsteady MHD flow of second grade fluids in a porous medium are analyzed. It is assumed that the bounding infinite inclined plate has a ramped wall temperature with the presence of heat and mass diffusion. Closed-form solutions in a general form are obtained by using the Laplace transform technique. The obtained results for velocity is found to satisfy all the imposed initial and boundary conditions. It can be reduced to known solutions from the literature as limiting cases.

Keywords: Double diffusion, MHD, Porous medium, Inclined plate, Second grade fluids, Laplace transform

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #9, pp. 76-80

Title of the Paper: Effect of Liquid Density on Particulate Flow in Dam Break

Authors: Gyeong Min Park, Hyun Sik Yoon, Min Il Kim

Abstract: The present study invetigated the dam breaking containg the particles by handling three pahses of the lquid-gas-solid mixure. The discrete element method (DEM) - computational fluid dynamics (CFD) conbined methos was adopted to resolve the three pahses of the lquid-gas-solid mixure. The present study considers the wide range of the liquid density to investugate the effect of the liquid density on the behavior of the particles and the free-surface. Three regimes of the overlapping, divergent and impinging behaviors govern the time evolution of the particles and the free-surface. The overlapping regime shows that the front head positions of the liquid and the particles are almost identical and two dimensional behaviors. However, in the divergent regime, lower liquid densities derive that the liquid front head is faster than that of the particle. Over the critical liquid density, the opposite divergent pattern to the low liquid density appears. Especially, the three-dimension effect on the distribution of the particles and the free-surface appears in the divergent regime.

Keywords: DEM, CFD, Three pahses, Lquid-gas-solid mixure, Three regimes

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #8, pp. 69-75

Title of the Paper: Definition of Critical Hydrodynamic Conditions for Sediment Motion Initiation Using Optical Techniques

Authors: Juan Antonio García Aragón, Klever Izquierdo Ayala, Humberto Salinas Tapia, Carlos Díaz Delgado

Abstract: Sediment motion initiation experiments were performed in a glass rectangular channel, with a loose bed in the central part. The main goal is to obtain the critical hydrodynamic characteristics that causes sediment bed motion initiation, for different cohesionless sediment grain sizes. The optical technique of Particle Tracking Velocimetry (PTV) was used in order to determine the critical velocity profiles for sediment initiation of motion. Between the parameters that define this critical velocity profile is the one known as bed rugosity which represents the height of asperities in the bed. For conditions near bed motion initiation experimental velocity profiles were obtained and they allowed us also to define fluctuating velocities u?, v? and a value of bed rugosity ks related to a representative grain size of the bed. It was shown that obtained critical velocity profiles are in good agreement with other works in the scientific literature provided an appropriate definition of bed rugosity is made.

Keywords: non-cohesive sediments, motion initiation, bed rugosity, critical velocity profile, PTV

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #7, pp. 57-68

Title of the Paper: Study on Contact State and Contact Stress Distribution of Kettle Mechanical Seal

Authors: Shuangxi Li, Huanli, Kesong Huang, Qiuxiang Zhang, Jining Cai

Abstract: In traditional mechanical seal design, the average transverse stress is used. However, in practice, the distribution of seal face contact tress is not uniform. The contact state and contact stress distribution affect seal face’s state of wear and deformations, which are of vital to the sealability and sealing life. Therefore, in this paper, complete and accurate finite element models of kettle mechanical seal (KMS) rotator ring, stator ring and stator ring seat were established by ANSYS. The seal face contact state and the contact stress distribution were obtained by the finite element analysis. And the influence laws of working pressure P, stator ring height H, load coefficient K, stator ring auxiliary O-ring inner diameter ratio S, etc. on the face performance were analyzed. It was shown that the contact stress distribution may be non-uniform in higher working pressure condition. Besides, the higher the working pressure P was, the more non-uniform the distribution was and the smaller the contact area was. The contact stress distribution was more uniform, the contact area increased and the maximum seal face contact stress decreased with the increasing of H, K and S. The research results were verified by designed test and provide a theoretical basis for the design and optimization of mechanical seal.

Keywords: kettle mechanical seal, contact stress distribution, contact state

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #6, pp. 49-56

Title of the Paper: Thermal Simulation of the Effect of Windings Arrangement in a Cooled Power Transformer

Authors: Alejandro Roberto Tello Campos, William Vicente Rodríguez, José Luis Fernández Zayas, Ignacio Carvajal Mariscal, Rodrigo Ocon Valdez

Abstract: The outcome of the study will be the determination of the effects of modifying geometrical parameters of a real 33.6 MVA power transformer by means of a simplified model based on CFD methods. This will help the designers to prove that power transformers winding physical arrangements determine the location and value of critical temperatures such as the hot spot. Basically, the results show that a the proposed variations in the outer radius of the high voltage winding and the high and low voltage vertical cooling duct widths do affect the critical temperatures location and value due to oil hydrodynamics. Results show that there is a reduction of 3.21% and 1.34% in the value of critical temperatures for the HV and LV cooling duct variation respectively and the location of hot spot is more specifically defined at the 42th LV disc. Outer HV radius variation results show also an increase of 1.6% in critical temperature and the location of hot spot still remains in the 42th LV disc.

Keywords: Power transformer, mixed convection, CFD, thermal simulation, geometrical parameters

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #5, pp. 36-48

Title of the Paper: Fluid Filled Containments Impact by a High Velocity Bullet

Authors: Smirnova M. N., Kondrat’ev K. A.

Abstract: High velocity fragment or bullet interaction with thin walled fluid-filled containment is investigated. Fragment subsonic motion in compressible fluid was studied being the function of the depth of perforation under the water level in case the containment was partially filled with water and partially with gas having a distinct fluid-gas interface. Approximation formulas were developed making it possible to simulate resistance and drag forces being functions of governing parameters. The developed models were validated by comparing theoretical data with results of experiments. The obtained solutions are applicable for developing concepts for effective shield design protecting from high velocity fragments.

Keywords: fragment, impact, crater, fluid-filled containment, resistance force, perforation

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #4, pp. 25-35

Title of the Paper: Regulation Performance of Regulatable Dry Gas Seal

Authors: Shuangxi Li, Qiaofeng Zhu, Jining Cai, Qiuxiang Zhang, Zhaoxu Jin

Abstract: It is important for the regulatory efficiency and the popularization of R-DGS to study on the regulation performance of a Regulatable Dry Gas Seal (R-DGS). Based on gas lubrication theory, a numerical model for R-DGS was set up, the Steady Reynold equation and Disturbance Reynold equation were resolved by using finite element method to obtain the equilibrium film thickness, leakage rate and dynamic parameters. The universal law of the seal parameters was obtained under difference regulation ratio Γ and shaft speed. The running regulation test is processed and the regulation reliability of R-DGS with outer regulative gas source is proved. The results show that the sealing performance of R-DGS changes obviously with the regulation ratio (Γ); and the shaft speed also effect the sealing performance when the regulation ratio is Γ<1.5. Comprehensive regulation performance of Pi-DGS is better than Po-DGS. The research results verify the feasibility of R-DGS and provide a reference for user to design and regulatory the R-DGS.

Keywords: Regulatable dry gas seal, Regulation performance, Steady state, Disturbed State

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #3, pp. 18-24

Title of the Paper: The Influence of the Reservoir Discontinuities on Fluid Filtration to the Production Well

Authors: Elena Andriyanova, Vladimir Astafev

Abstract: Today especially important to study the filtration process in the reservoir with fractures. The fracture may be either natural, in case of tectonic fault, or artificial, in case of well simulation, and it may have various permeability values. This paper considers the steady-state flow process of incompressible fluid to the production well in a reservoir of constant height and permeability. There is a thin area in the reservoir with constant permeability kf, which might be highly permeable crack or low permeable barrier. The characteristics of filtration process are studied for various kf values. The nature of fluid flow to the wellbore is analyzed at different locations of the well and the crack for different values of the fracture conductivity in this paper and the analytical expression for skin effect is defined.

Keywords: filtration, skin effect, highly permeable cracks, hydraulic fractures, low permeable barriers, Darcy flow, flow potential

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #2, pp. 10-17

Title of the Paper: Computational Investigation of the External Excitation Frequency Effect on Liquid Sloshing Phenomenon

Authors: Abdallah Bouabidi, Zied Driss, Nihed Cherif, Mohamed Salah Abid

Abstract: In this work, the Computational Fluid Dynamic (CFD) method was used to simulate the liquid sloshing phenomenon in a rectangular tank. The tank was subjected to an external sinusoidal excitation. Particularly, we are interested on the study of the external excitation frequency effect. The hydrodynamic parameters describing the flow like the velocity field, the average velocity, the static and the dynamic pressure were presented. All numerical results were conducted using the commercial CFD code "FLUENT". The volume of fluid (VOF) method based on the finite volume method was used to simulate incompressible viscous two phase flow in a tank partially filled with liquid. The results show that the liquid sloshing significantly depends on the frequency value. For a weak value of frequency, the liquid moves slowly. With the increase of the frequency, the liquid sloshing becomes more violent. A good agreement has been shown by comparing our numerical results with the experimental one.

Keywords: External excitation, frequency, turbulent flow, finite volume method, VOF

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 11, 2016, Art. #1, pp. 1-9