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 Volume 5, 2010
Print ISSN: 1790-5087
E-ISSN: 2224-347X








Issue 1, Volume 5, January 2010

Title of the Paper: Adjustment of Dissipative Terms to Improve Two and Three-Dimensional Euler Flow Solutions


Authors: Seyed Saied Bahrainian

Abstract: The Euler equations are a set of non-dissipative hyperbolic conservation laws that can become unstable near regions of severe pressure variation. To prevent oscillations near shockwaves, these equations require artificial dissipation terms to be added to the discretized equations. A combination of first-order and third-order dissipative terms control the stability of the flow solutions. The assigned magnitude of these dissipative terms can have a direct effect on the quality of the flow solution. To examine these effects, subsonic and transonic solutions of the Euler equations for a flow passed a circular cylinder has been investigated. Triangular and tetrahedral unstructured grids were employed to discretize the computational domain. Unsteady Euler equations are then marched through time to reach a steady solution using a modified Runge-Kutta scheme. Optimal values of the dissipative terms were investigated for several flow conditions. For example, at a free stream Mach number of 0.45 strong shock waves were captured on the cylinder by using values of 0.25 and 0.0039 for the first-order and third-order dissipative terms. In addition to the shock capturing effect, it has been shown that smooth pressure coefficients can be obtained with the proper values for the dissipative terms.

Keywords: Artificial Dissipation, Unstructured Grids, Finite volume, Euler Equations, Shock capturing

Title of the Paper: Scale-up of a Cold Flow Model of FICFB Biomass Gasification Process to an Industrial Pilot Plant – Hydrodynamics of Particles


Authors: J. Mele, J. Oman, J. Krope

Abstract: The article introduces the research of particles hydrodynamics in a cold flow model of FICFB biomass gasification process and its scale-up to industrial pilot plant. A laboratory unit has been made for the purposes of experimental research. The laboratory unit is three times smaller than the later pilot plant. For a reliable observation of the flow process, similar flow conditions must be created in the laboratory unit and the pilot plant. The results of the laboratory model will be similar to those of the actual device if geometry, flow and Reynolds numbers are the same. Therefore, there is no need to bring a full-scale gasificator into the laboratory and actually test it. This is an example of "dynamic similarity".

Keywords: Fluid bed, Pneumatic transport, Reynolds number, Gasification, Scale-up

Title of the Paper: Synthetic Jet Design Criteria and Application for Boundary Layer Separation Control


Authors: Francesca Satta, Daniele Simoni, Marina Ubaldi, Pietro Zunino, Francesco Bertini

Abstract: With the purposes of better understanding the phenomena associated with the synthetic jet operation as well as identifying suitable design criteria to control boundary layer laminar separation, the aerodynamic performance of a synthetic jet system has been experimentally investigated. Both device design and its aerodynamic characterization are addressed in the paper, paying particular attention to the fundamental parameters to be set for the synthetic jet design. The synthetic jet behaviour has been surveyed adopting different measuring techniques. Power density spectra have been evaluated from jet velocity distributions measured by means of a hot-wire anemometer. In order to investigate the instantaneous flow field and to allow the identification of the jet organised flow structures, Particle Image Velocimetry has been adopted. Moreover, to distinguish the different jet dynamics during the peculiar phases of the device (blowing and suction), phaselocked ensemble averaging technique has been applied. The system has been successively tested with external cross-flow and the jet performance has been surveyed. In particular, the device has been applied on a flat plate installed in a double contoured walls test section in order to verify the capability of the jet in suppressing the boundary layer laminar separation induced by strong adverse pressure gradients, typical of Ultra-High-Lift turbine pressure distributions.

Keywords: Boundary layer control, synthetic jet, blowing ratio, Strouhal number, Particle Image Velocimetry, hot-wire anemometry

Issue 2, Volume 5, April 2010

Title of the Paper: Time-Varying Flow Investigation of Synthetic Jet Effects on a Separating Boundary Layer


Authors: Francesca Satta, Daniele Simoni, Marina Ubaldi, Pietro Zunino, Francesco Bertini

Abstract: This paper is focused on the investigation of the interaction between a synthetic jet and the boundary layer which develops over a flat plate subjected to an adverse pressure gradient typical of a high-lift lowpressure turbine profile. Two different Reynolds numbers of the main flow, Re = 200000 and Re = 70000, typical of the low-pressure turbine operating conditions during the take-off/landing and cruise phases, respectively, have been investigated. Wall static pressure distributions along the plate showed the different effects induced by the jet on the boundary layer separation with the jet Strouhal numbers investigated. The device capability of suppressing the large laminar separation bubble which occurs for the uncontrolled condition has been more in depth investigated by means of hot-wire time-mean and ensemble averaged measurements. The phase-locked ensemble averaging technique, synchronized with the synthetic jet frequency, has been employed to distinguish the effects induced by the jet during the blowing and the suction phases. The active device has been proved to be able to control the laminar separation bubble induced by a strong adverse pressure gradient, also at the low Reynolds number condition tested. The ensemble averaged measurements showed that a larger contribution to the reduction of the boundary layer velocity defect is obtained during the suction phase of the jet.

Keywords: Boundary layer control, separated boundary layer, low-pressure turbines, synthetic jet, phaselocked measurements, hot-wire anemometry

Title of the Paper: Two Different Turbulence Models in Comparison with Experiments on Thermal Mixing Phenomenon in a Tee Piping


Authors: Chao-Jen Li, Yao-Long Tsai, Tai-Ping Tsai, Li-Hua Wang

Abstract: Thermal fatigue failures in reactor cooling systems of nuclear power plants are caused by the fluctuating stresses on a piping system due to the hot and cold flows are mixed together in a mixing piping. The present paper describes BSL Reynolds Stress (BSL-RSM) and k-epsilon (k-ε) simulation data of thermal mixing in a mixing piping compared with results from experimental data. The fluid in the experiment is concentration of de-ionized water and the liquid electrical conductivities are measured by the use of the 16?16 electrode. To verify the mixing phenomenon between de-ionized water with different electrical conductivities and water with different temperatures, the inlet temperatures of the hot and cold water in the simulation process are set to 80? and 15? respectively. The analytic results calculated by the commercial CFD code ANSYS CFX 11.0 show that the different turbulence models(BSL-RSM, k-ε)and different turbulent Prandtl numbers(0.9, 0.2, 0.1) will affect the simulation results of temperature fluctuations. Since the coefficient of determination, R2, obtained by using Prt=0.1 for BSL-RSM turbulence mode is between 0.996 and 0.788, which is higher than that by using Prt=0.2 and Prt=0.9, the perditions for smaller turbulent Prandtl number are in better agreement with measurements. The absolute error, β, obtained by using BSL-RSM turbulence model at x=0.025m is smaller than that by using k-ε turbulence model. However, at x=-0.025m, the absolute error, β, obtained by using k-ε turbulence model is smaller than that by using BSL-RSM turbulence model. The computational results are in qualitative good agreement with experimental data that the mixing phenomenon of water with two different temperatures can be explained by de-ionized water with two different electrical conductivities.

Keywords: BSL-RSM, Thermal Fatigue, Turbulent Prandtl Number, Mixing

Title of the Paper: Computing of Cavitation Characteristic and Sensitivity Curves for Francis Pump-Turbine


Authors: Anton Iosif, Ioan Sarbu

Abstract: It is well known, that the fluid motion in reversible hydraulic machinery elements is a complex threedimensional problem. In this paper it is developed an explicit numerical model based on Finite Element Method and Dual Reciprocity Method for the simulation of the flow velocity and pressure distributions on blade of the Francis type reversible radial-axial hydraulic machine’s runner, in the hypothesis of ideal incompressible fluid and the relative rotational motion. The proposed numerical model was applied for reversible radial–axial hydraulic machinery operating as a pump. The blade has the basic profile NP205. This profile has a quadratic equation which defines its skeleton and its thickness function is that of a NACA profile with a maximum relative thickness of five percent. The numerical results for different discharge values have finally allowed obtaining the cavitation characteristic and sensitivity curves for the reversible hydraulic machinery.

Keywords: Reversible hydraulic machines, Axial-symmetrical motion, Radial-axial profile cascades, Velocity and pressure distributions, Two-dimensional numerical model, Computer programs, Cavitation characteristic, Cavitation sensitivity curves

Issue 3, Volume 5, July 2010

Title of the Paper: A Study on Saline Water Intrusion and Fresh Water Recharge Relevant to Coastal Environment


Authors: Sudip Basack, A. K. Bhattacharya, Chitta Sahana, Prabir Maity

Abstract: The paper is based on experimental laboratory model study with relevant mathematical analysis followed by field investigation so as to understand the characteristics and flow pattern of saline water intrusion into natural porous medium followed by subsequent fresh water recharge.

Keywords: Coastal aquifer, Darcy flow, Forchheimer flow, Fresh water recharge, Reynolds number, Saline water intrusion

Title of the Paper: Hydraulic Performance of Double Slotted Barriers under Regular Wave Attack


Authors: E. V. Koutandos

Abstract: In the present study, wave interaction with double, fixed, vertical, semi-immersed, slotted barriers is investigated numerically. Numerical results concerning obtained with the use of the COBRAS (Cornell breaking Wave and Structures) wave model for regular waves reveal the effects of barriers porosity, relative depth d/L (d: water depth, L: wave length) and relative distance between the two barriers S/L (S: the distance between the two barriers, L: wave length) on the hydrodynamic characteristics (wave transmission, reflection, dissipation, velocity field, turbulence kinetic energy field). Numerical results concerning wave transmission, reflection, dissipation against the porosity of the barriers, d/L and S/L are well compared with experimental results by Isaacson et al. [14], revealing the credibility of the wave model. Detailed computed velocities and turbulence kinetic energy in the vicinity of the structure indicate the effects of the special breakwater on the flow pattern and the turbulence structure.

Keywords: Double Slotted Barriers, Permeable Barriers, Special Βreakwater

Title of the Paper: Feasible Structural and Non- Structural Measures to Minimize Effect of Flood in Lower Tapi Basin


Authors: Dhruvesh P. Patel, Mrugen B. Dholakia

Abstract: Floods have always been a major problem to the human race, as many settlements have grown up around rivers. The fastest growing city of India, Surat, is settled on the bank of river Tapi. Varekhadi, a group of 26 mini watersheds lead water into river Tapi and the flow takes a small time period to reach near Surat city. Due to which, the city gets flooded once in a 4 to 5 years and losses large amount of property and lives. Present work describes the flood potential of Varekhadi watershed group by application of Soil and Water Assessment Tool (SWAT) model, using Remote Sensing (RS) and Geographical Information System (GIS). In order to minimize the effect of flood, in and around Surat city, feasible structural and non-structural measures are suggested.

Keywords: Flood, Tapi, Varekhadi, SWAT, LTB, CWC, GIS, Ukai dam

Title of the Paper: Metallographic and Numerical Methods Investigations about Failure of a Kaplan Turbine Runner Blade


Authors: Doina Frunzaverde, Viorel Campian, Dorian Nedelcu, Gilbert-Rainer Gillich, Gabriela Marginean

Abstract: The paper presents the results of the failure analysis of a Kaplan turbine runner blade from a hydropower station in Romania. In order to determine the causes that led to the cracks, the authors first carried out metallographic investigations on a sample obtained from the cracked blade. The metallographic investigations included macroscopic and microscopic examinations (light microscopy and scanning electron microscopy) and X-ray diffraction analyzes (XRD). They led to the conclusion that the cracking of the blade was caused by fatigue, initiated by the numerous non metallic inclusions, which were discovered in the vicinity of the blade surface. The results obtained were confirmed by calculations on the resistance and service life estimations of the blade. The calculations carried out included the following steps: construction of the solid 3D-model of the blade, determination of the blade loads from hydrodynamic conditions, linear static analysis of the blade and service life estimations, calculated for maximal stress values of the concentrators. They led to the conclusion that the cracking of the blade started and developed from the stress concentrator placed between blade and blade flange on leading edge direction. In order to decrease the maximal stress value, the authors concluded that the hydrodynamic loads on the blade must be obligatory reduced. Therefore, as the operating conditions (discharge, head, speed, power) are not changeable, the stress reduction could be realized only by increasing the number of the runner blades.

Keywords: Hydropower station, Kaplan turbine, fatigue cracking, service life estimations

Title of the Paper: Modeling of Induced Circulation


Authors: Lale Balas, Asu Inan

Abstract: Marinas located along the coastline of an enclosed sea are subjected to water quality problems due to insufficient water exchange resulting from the weakness of the tidal motion. For such marinas forced flushing measures may need to be designed. In this paper, two forced flushing schemes for enhancing flushing rates of marinas in enclosed seas are discussed. First forced flushing scheme is the removal of the surface layer of water in the marina by mechanical pumping and the second one is the wave pump. The induced circulation patterns by the use of the Morning Glory type intake structure and wave pump experiments were performed in the laboratory and forced circulations were simulated by the developed three dimensional hydrodynamic and transport model, HYDROTAM-3. Turbulence has been simulated by a two equation k-ω turbulence model. With the application of the morning glory type intake and the wave pump, the flushing ability of the marina increased about 10 times and 12 times respectively, compared to the tidal flushing alone. Model predictions provided encouraging results. HYDROTAM-3 reproduces the velocity field that is in good agreement in the intensity and spatial scale with the current measurement.

Keywords: Marina, forced flushing, modeling, turbulence, wave pump, mechanical pumping, finite element, hydrodynamic, transport

Title of the Paper: Research Regarding the Use of New Systems to Control Fluid Flow in Pipelines


Authors: Olimpiu Stoicuta, Marin Silviu Nan, Gabriel Dimirache, Nicolae Buda, Dan Liviu Dandea

Abstract: In this paper a research is made on the design of a new fluid flow control system on transport pipelines. The flow control system is based on a sensorless speed control system of an induction motor with the squirrel – cage. The estimator component for rotor flux and speed from the induction motor speed control system is an Extended Gopinath Observer

Keywords: Extended Gopinath Observer, Sensorless Control, Flow Control Simulation, Centrifugal Pumps

Title of the Paper: Numerical Study on the Flow Characteristics of a Solenoid Valve for Industrial Applications


Authors: Taewoo Kim, Sulmin Yang, Sangmo Kang

Abstract: Study on the flow characteristics of solenoid valves is essential since they play pivot role in a flow circuit for controlling the flow through a required path for a specified duration. The flow characteristics of a 3/2 -way solenoid valve used in the four stroke propulsion engine of a ship is studied by performing numerical simulation using ANSYS CFX 12.0 commercial software package. The solenoid valve can be operated in two ways- either by pushing the hand operated button for moving the spool or by moving the spool using electric signal. The valve under study is a superspeed valve and the response time of moving spool is very short. The movement of the spool which is located in the middle of the body of solenoid valve affects the flow characteristics. This is examined by performing a static analysis by changing the position of the spool. The high pressure air passes through a pipe and reaches the engine tank of given dimensions. The simulation is performed for different inlet pressure and spool displacement and the corresponding flow characteristics are obtained. The results of the three dimensional numerical simulation will be helpful in the proper design of solenoid valve for the industrial applications.

Keywords: Numerical simulation, Computational fluid dynamics, Solenoid valve, Spool displacement, Flow characteristics, ANSYS CFX, SST model

Title of the Paper: Determination of Optimal District Heating Pipe Network Configuration


Authors: M. Jamsek, D. Dobersek, D. Goricanec, J. Krope

Abstract: In this article the developed mathematical model, which based on simplex method is presented. The mathematical model, consisting of the non – linear objective function and system of non – linear equations for the hydraulics limitations is developed. On its basis the computer program for determination optimal tree path with the use of simplex method was solved. For economic estimation the capitalized value method, which consider all costs of investment and operation was used. The simulation is done on a pipe network with 22 pipes and 13 nodes.

Keywords: Heating, Pipe network, Optimisation, Non-linear programming, Simplex method

Title of the Paper: Convection in Superposed Fluid and Porous Layers in the Presence of a Vertical Magnetic Field


Authors: Hanadi M. Banjer, Abdullah A. Abdullah

Abstract: A linear stability analysis is applied to a system consisting of a horizontal fluid layer overlying a layer of porous medium saturated with the same fluid, with uniform heating from below in the presence of a vertical magnetic field. The flow in porous medium is assumed to be governed by Darcy’s law. The Beavers-Joseph condition is applied at the interface between the two layers. Numerical solutions are obtained using expansion of Chebyshev polynomials. This spectral method has a strong ability to solve multi-layered problems and allows us to obtain a highly accurate eigenvalues in a very efficient manner. Numerical results are obtained for different values of the parameter (= depth of fluid layer/depth of porous layer) and different values of the magnetic parameter Q. The effect of magnetic field is investigated and it is found that the linear stability curves for the onset of convection motion are bimodal even for higher values of d.

Keywords: Superposed porous and fluid layers- Thermal convection- Darcy's law- Magnetic field- Stationary convection, Chebyshev tau method

Title of the Paper: Simplified Mesoscale Lattice Boltzmann Numerical Model for Prediction of Natural Convection in a Square Enclosure filled with Homogeneous Porous Media


Authors: C. S. Nor Azwadi, M. A. M. Irwan

Abstract: The lattice Boltzmann method (LBM) is applied to a generalised isotropic porous media model in a square geometry by introducing a force term to the evolution equation and a porosity to the density equilibrium distribution function. The temperature field is obtained by simulating a simplified thermal model which uses less velocity directions for the equilibrium distribution function and neglects the compression work done by the pressure and the viscous heat dissipation. The reliability of this model for natural convective heat transfer simulation is studied by comparing with results from previous simulations at a porosity value, ε = 0.9999. The model is then used for simulation at ε = 0.4, 0.6 and 0.9 at three different Rayleigh numbers. Comparison of solutions with previous works confirms the applicability of the present approach.

Keywords: Lattice Boltzmann method, distribution function, Boussinesq approximation, porous media, convective heat transfer

Title of the Paper: Aerodynamic Characteristics of Wing of WIG Catamaran vehicle During Ground Effect


Authors: Adi Maimun, Saeed Jamei, Agoes Priyanto, Nor Azwadi

Abstract: In this paper, the aerodynamic characteristics of wing with NACA 6409 section from WIG Catamaran vehicles with the influence of twin hull and ground effect was numerically studied. The simulation of WIG Catamaran was performed by Three Dimensional (3D) Computational Fluid Dynamic (CFD). The k-ω SST turbulent model was used for turbulent flow in CFD mode. In order to validate the numerical results, the CFD simulations of only wing with NACA 6409 section were compared with experimental data published by previous researcher. Next, Lift coefficient and, drag coefficient and lift to drag ratio of wing with twin hulls of WIG catamaran were determined on various of angle of attacks and two ground clearances (h/c=0.3 and infinity). The results of the CFD simulation indicate a reduction on lift and drag coefficients but there is an increment lift to drag ratio of wing which is caused by twin hulls of WIG Catamaran, as well as there are enhancement on lift coefficient and decreasing on drag coefficient, hence lift to drag ratio increases when flying in proximity to the ground.

Keywords: WIG Catamaran, Wing In Ground effect, Aerodynamic characters, NACA 6409, CFD analysis

Title of the Paper: Energy Efficiency of Machinery Hydro-Pneumatic and Climate Impact


Authors: Marius-Constantin Popescu, Nikos E. Mastorakis, Mircea Grigoriu, Jean-Octavian Popescu

Abstract: In practice, due to various over-the loss of pregnancy considered by designers as a security measure, the pump provides a flow chosen much higher than calculated. The main greenhouse gases (GHGs) producer is represented by the fossil burning systems. The paper presents the effect on the GHGs emission combined with the economic effects of a new pumping system method of automatic mixing of hot and cold water circulated with variable speed driving pumps and adjustable vanes. Considering the potential economic and environmental effects combined with the social one, The heating systems represent a sensitive sector of the energy consumers’ basket, strengthen by the unpredictable primary energy price fluctuation, the recent financial crisis and the population expectations. This paper tries optimizing operation of machinery, hydro-pneumatic.

Keywords: Modeling and optimization, Greenhouse gases, Heating systems, Economic effects

Title of the Paper: Accessible Technical Solution for Normal Construction Apparatus Usage in Ex Classified Areas


Authors: Jeana Ionescu, Lucian Moldovan, Sorin Burian, Marius Darie, Tiberiu Csaszar, Carol Zoller

Abstract: This paper intercession is due to an undesirable penury state regarding eligible technical equipment for use in Ex classified areas. This fact competed with the negative dynamic of material possibilities leads to an apparent lack of interest regarding protection to explosion. As a solution to the identified problem, the authors propose the use of normal construction technical equipment adapted according to prescriptions of “pz” pressurized enclosure protection type. This intercession presents a good estimated level of tolerance to customer and will lead to the decrease of explosion risk level due to technical equipment and lower acquisition, maintenance and repair specific costs.

Keywords: Ex classified areas, Ex apparatus, pressurization, autonomy time, purging, loss compensation

Title of the Paper: Proper Orthogonal Decomposition Analysis for Unsteady Rotor-Stator Interaction in a Low Pressure Centrifugal Compressor


Authors: Sterian Danaila, Mihai Leonida Niculescu

Abstract: In this paper, Proper Orthogonal Decomposition (POD) is applied to the analysis of the unsteady rotor-stator interaction in a low-pressure centrifugal compressor. Numerical simulations are carried out through finite volumes method using the Unsteady Reynolds-Averaged Navier-Stokes Equations (URANS) model. Proper Orthogonal Decomposition allows an accurate reconstruction of flow field using only a small number of modes; therefore, this method is one of the best tools for data storage The POD results and the data obtained by the Adamczyk decomposition are analyzed. Both decompositions show the behavior of unsteady rotor-stator interaction, but the POD modes allow quantifying better the numerical errors.

Keywords: Unsteady Rotor-Stator Interaction, Adamczyk decomposition, POD, CFD, Compressor, URANS, Flow Field Reconstruction

Title of the Paper: Contribution for the Vulnerability Assessment of Water Pipe Network Systems


Authors: Jorge Pinto, Luis Afonso, Joao Varajao, Isabel Bentes, Humberto Varum, Antonio A. L. S. Duarte, Jitendra Agarwal

Abstract: Water pipe network systems are key public utilities which require being robust, protected and preserved. Knowing their weaknesses will help these processes. The theory of vulnerability of water pipe networks can contribute in this context because it is able to map the vulnerable parts of this type of system. The meaning of vulnerability has been defined as being the disproportionateness of the failure consequences in relation to the initial damage and, in particular, its theoretical concepts. The main objectives of this paper are to briefly introduce this theory, to illustrate its application highlighting its potential. The application of the theory is presented using an example of a simple water pipe network. In a real water supply utility, where the vulnerabilities of WPN components are less evident, the identification of the most vulnerable ones may play an important contribution as support decision during WPN design period and for a sustainable infrastructure asset management. Further work is in progress to account for different type of damage and consequences and thus manage risks due to failure scenarios not identified by the classical theories.

Keywords: Water management; water pipe networks, vulnerability, failure scenarios, system safety

Issue 4, Volume 5, October 2010

Title of the Paper: Performance of the Constants Couple of the Second Order Turbulence Model (RSM) Applied to an Axisymmetric Configuration


Authors: M. Senouci, A. Bounif

Abstract: The Reynolds stress model (RSM) is considered as a more sophisticated approach used to modelling the turbulent flows, compared to the other turbulence models. This type of model, used to improve the accuracy of the results, overcomes the turbulent viscosity concept and the assumption of the turbulence isotropy which it means. The pressure-strain correlation term is among the most important terms to be modelled in the exact transport equations of the Reynolds stresses. Different models, used for modelling the pressure-strain correlation term, have been proposed by different authors. The basic model is that proposed by Launder, Reece and Rodi (1975) [1] called LRR-IP, a combination of Rotta's model and the IP model (Isotropisation of Production). The main objective of this study is to test the performance of the constants pair (C1, C2) used in such model for modelling the pressure-strain correlation term.

Keywords: Turbulence, axisymmetric jets, second order modelling, pression-strain correlation

Title of the Paper: A Review of Effects of Initial and Boundary Conditions on Turbulent Jets


Authors: Adel Abdel-Rahman

Abstract: On the basis of available knowledge, it is shown that different mechanisms may have control in different jet flows or in different regions of a jet flow. In free jet flows, the downstream region is dominated by turbulence structure whereas coherent eddy-structure can have a strong influence on the near field, particularly for low-Reynolds number jet flows. At present, however, it has become a common belief that coherent-eddy structures determine, to a large degree, the evolution and dynamics of turbulent jet flows. The following article is an attempt to review the current information on round turbulent jet flows. In so doing, the influence of the jet origin (initial conditions) and the boundary conditions (presence or absence of endplate, side walls, and/or jet enclosure) on the jet flow structure is considered.

Keywords: Jets, Turbulent jets, Jet initial conditions, Jet structure, Coherent structure

Title of the Paper: Application of Euler-Euler Model for Numerical Simulation of a Radial Turbine Working in the Two-Phase Flow Regime


Authors: Sebastian Schuster, Friedrich-Karl Benra, Hans Josef Dohmen

Abstract: This paper deals with the numerical calculation of a single stage radial turbine with nucleation in the impeller. The calculations are performed with Ansys CFX 12.1 and are based on the Euler-Euler model. In terms of velocity and temperature, the flow is inhomogeneous. The Euler-Euler model is combined with a nucleation model based on the classical nucleation theory. The working fluid is steam calculated with the IAPWS formulation. First a validation of the used numerical code with experimental results is performed. On the investigated geometry different parameter variations such as different inlet conditions and change in rotational velocity are performed. The goal of the work is to show the influence of this parameters on the water film formation. It will be shown that a high proportion of water is at the blades even if the nucleation occurs in the impeller and the area averaged wetness at the outlet is low.

Keywords: Euler-Euler, inhomogeneous, two-phase flow, nucleation


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