WSEAS Transactions on
Fluid Mechanics

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

Volume 10, 2015

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 10, 2015

Title of the Paper: Physical Modelling of Laboratory Debris Flows by Using the Sodium Carboxymethylcellulose (Na-CMC)

Authors: Giacomo Viccione, Marco Genovese, Fabio Rossi, Domenico Guida, Tony Luigi Leopoldo Lenza

Abstract: Debris flows are among the most destructive processes occurring in mountain environments. It is recognized that rheology describing the relationship between stress and strain rates is mainly dependent from interstitial fluid content, pore fluid pressure, sediment concentration, and size and distribution of dispersed grains. However, due to their complex behaviour, it is unlikely that they can be characterized by a prefixed rheological model. Within this framework, we have assessed the feasibility of a double model of similarity of Reynolds and Froude, as attempt to mimicking the interstitial fluid phase at laboratory scale. For the purpose we used the Sodium Carboxymethylcellulose (Na-CMC or briefly CMC) as thickening agent in aqueous solutions. By varying the solute concentration, it was possible to reproduce the pore fluid of a specific viscosity. The related transparency of such solutions allows observing and describing evolution processes by high-frequency digital acquisition. Among the others, the main innovative feature consisted in the possibility of establishing a relationship between laboratory experiments and corresponding assumed prototypes, by means of the proposed model scaling. The experimental campaign being carried out, allowed to establish a state equation for the model reference, that is a relationship among viscosity, solute concentration and temperature. A predominant dependence between viscosity and solute concentration was observed, marking another advantage in using such solutions. The similarity then connect model results to the prototype.

Keywords: Interstitial fluid – Sodium Carboxymethylcellulose – Na-CMC – Physical modelling – model scaling – Viscosity – viscometric tests – Rheological models

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #17, pp. 164-174

Title of the Paper: Permeability Simulations in Textiles

Authors: Karel Adamek

Abstract: The paper deals with numerical flow simulation in permeable textile structures and their combinations. Permeability parameters are evaluated from permeability measuring on such real structures and combinations. The flow inside of the permeable volume is explained by numerical flow simulation. The received images of flow fields give a good idea about the behavior of the studied structure at the intended purpose. Several examples are presented here – the permeability of thick yarn layer, wound on the bobbin, permeability of combined multi-layer clothing under wind effect and condition for water vapor condensation in such multi-layer clothing.

Keywords: Numerical flow simulation, Air permeability, Multi-layer clothing

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #16, pp. 155-163

Title of the Paper: Numerical Investigation of the Reflection of Asymmetric Shock Waves in Steady Flow: Transitions (RR-MR) and Hysteresis Phenomenon

Authors: Benderradji Razik, Beghidja Abd elhadi, Gouidmi Hamza

Abstract: The analytical study and experimental research on the reflection of the asymmetric shock waves (RR-MR interference), in the stationary supersonic flows been reported for the first time by H. Li and al [1]. The purpose of this research is to perform numerical simulations (CFD) on the Interference shock waves in the supersonic flows and more particularly being studied of the transition regular reflection (RR) to Mach reflection (MR) and vice versa – phenomenon hysteresis. This last process was largely studied numerically in the case of the symmetrical reflections during these last years. The analysis of the results obtained was based on experimental results H. Li and al [1], and compared analytically by the theory of tripled shock (shock polar). The theoretical study allowed the identification of the criteria of transition, and clearly shows the existence of a hysteresis phenomenon in the transition (RR) - (MR), from the asymmetric shock waves similar to that existing in interaction of symmetrical shock waves.

Keywords: Shock wave, Shock Interferences, regular reflection, Mach Reflection, shock polar

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #15, pp. 146-154

Title of the Paper: A New Approach for the Estimation of Longitudinal Damping Derivatives: CFD Validation on NACA 0012

Authors: Piero Gili, Michele Visone, Angelo Lerro, Francesco De Vivo, Gianluca Scognamiglio

Abstract: Aerodynamic longitudinal damping derivatives are of great importance for aircraft stability and control and for aircraft aeroelasticity problems. The classical methods adopted to calculate damping derivatives, using USAF Datcom or wind tunnel tests, are not accurate enough for unconventional shaped aircrafts in particular. Moreover, experimental methods refer to body pitch and plunge motion: it follows that the derivatives are affected to a great extent by the frequency. Some authors have proposed quasi-steady methods, which fail at the transonic regime. To overcome all of these shortcomings, a new approach, based on looping and heaving motion, is presented. The results of the proposed methods are validated, using CFD simulation with the NACA 0012 airfoil, against the exact Theodorsen theory, indicial functions and numerical results from other authors.

Keywords: Damping derivatives, CFD, Flight mechanics, Moving boundary

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #14, pp. 137-145

Title of the Paper: Large Eddy Simulation in Three-dimensional Cavity Using Dynamic Modeling

Authors: A. F. A. Pinho, J. G. Coelho, A. S. Neto

Abstract: Our study developed a fourth-order numerical code in space and a third-order in time with dynamical turbulence model. This code was applied to study turbulence transition in shear driven cavity flow in bi and three- dimensional configurations. The simulations had been carried out for bi and three-dimensional configurations. The two dimensional simulations were performed to be compared with results presented in the literature in order to validate the developed code, as well as to define the best parameters for the simulations in three-dimensional configuration. The Reynolds numbers were taken as 3200, 10000, 25000, 50000 and 100000. The simulations of cubic shear driven cavity flow with Reynolds numbers 3200 and 10000 were compared with results presented in the literature. Two-dimensional simulation was performed without turbulence model, and three-dimensional simulations were performed using the Smagorinsky and Germano models for sub-grid scale. The topological physical nature was analyzed and some important new physic characteristics were pointed out.

Keywords: LES, Simulation, Cavity

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #13, pp. 126-136

Title of the Paper: Prediction of Free Surface Flows Relevant to PTS Problems

Authors: Alexander Churbanov

Abstract: This paper deals with assessment of two CFD codes (commercial code FLUENT and free/open source software OpenFOAM) for predicting free surface flows relevant to Nuclear Reactor Safety (NRS). Three validation cases attributed to Pressurized Thermal Shock (PTS) problems are calculated and compared with experimental data. The numerical results are in good agreement with measurements for all cases considered in the work. Both codes provide high-fidelity predictions of free surface flows and can be extensively exploited for reactor safety analysis.

Keywords: Pressurized thermal shock, free surface flows, validation cases, FLUENT, OpenFOAM

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #12, pp. 117-125

Title of the Paper: A Numerical Method to Analyze the Interaction Between Sea Waves and Rubble Mound Emerged Breakwaters

Authors: Fabio Dentale, Giovanna Donnarumma, Eugenio Pugliese Carratelli, Ferdinando Reale

Abstract: The paper provides some results of a new procedure, developed by MEDUS, to analyze the hydrodynamic aspects of the interactions between maritime emerged breakwaters and waves, by integrating CAD and CFD software. The filtration of the fluid within the interstices of a concrete blocks breakwater is evaluated by integrating the Reynolds Averaged Navier-Stokes equations (RANS) inside the voids rather than making use of the widespread "porous media" approach. The structure is thus modelled, very much like in the real world or in the physical laboratory testing, by overlapping individual three-dimensional elements (Armour in AccropodeTM, Core-locTM or Xbloc®, toe protection and filter layer in stones), and then the computational grid is fitted so as to provide enough computational nodes within the flow paths. This approach is meant to match closely the physical laboratory test procedure, and it is oriented at analyzing the hydrodynamic aspects of the phenomenon (overtopping, breaking, Run-up, reflection) as well as the stability of armour elements. Therefore, for the results' validation, the numerical Run-up and reflection effects on virtual breakwater were compared with some empirical formulas and some similar laboratory tests.

Keywords: CFD, Breakwater, Armour, Rubble Mound, Virtual Structures, Wave Run-Up, Wave Reflection, Wave Overtopping

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #11, pp. 106-116

Title of the Paper: A Moving Piston Boundary Condition Including Gap Flow in OpenFOAM

Authors: Clemens Fries, Bernhard Manhartsgruber

Abstract: Fuel injection as well as digital switching strategies in fluid power applications are not only famous representatives of a large field of technology but also a main reason for the increasing interest in wave propagation effects in research. While there is a huge number of works dealing with the pressure drop of different hydraulic components in the steady state, many issues still remain unresolved in the transient regime, even in the case of laminar fluid flow. A better understanding of these processes would be a great benefit as it would lead to a higher accuracy of predicted system responses. In order to reach a higher degree of precision, the highly sophisticated computational fluid dynamics (CFD) codes are a wide-spread tool. These codes solve the famous Navier-Stokes equations in all three dimensions of space and therefore result in the full resolution of the pressure field as well as of the velocity field. A very awkward topic of performing a CFD simulation is the choice of the boundary condition, which should correspond to a physical one. At the latest when measurements for validation are carried out, the boundary condition of the experimental setup should match the one used in the simulation. Especially the use of a volumetric flow rate boundary condition is fraught with problems. Using a moving piston, a definite volumetric flow rate could be forced on a boundary. In an experimental setup only the measurement of the position of the piston would be necessary to use it in the simulation. This measurement has no backlash on the system, which is therefore well separated. In this work a moving piston boundary condition including gap flow is implemented and used in OpenFOAM. For this reason moving walls have to be used and the mesh has to change during the simulation. Results of simulations done with this moving piston boundary condition are

Keywords: Fluid power, fluid mechanics, fluid flow, transmission lines, hydraulics, CFD, OpenFOAM

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #10, pp. 95-105

Title of the Paper: Effects of the Advance Ratio on Flow Structures Around Marine Propeller

Authors: Hyun Sik Yoon

Abstract: This study numerically carried out the propeller open water test (POW) by solving Navier-Stokes equations governing the three-dimensional unsteady incompressible viscous flow with the turbulence closure model of the k-ω SST model. Numerical simulations were performed at wide range of advance ratios. A great difference of velocity magnitude between the inner region and the outer region of the slipstream tube forms the thick and large velocity gradient which originates from the propeller tip and develops along the downstream. Eventually, the strong shear layer appears and plays the role of the slipstream boundary. As the advance ratio increases, the vortical structures originated from the propeller tips quickly decay. The contraction of the vortices trace is considerable with decreasing the advance ratio.

Keywords: propeller, wake, tip vortex, slipstream, advance ratio, KP505

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #9, pp. 88-94

Title of the Paper: Numerical Optimization of AdBlue®-Injection into the Mixing Section of SCR-Systems

Authors: Lukas Möltner, Verena Schallhart

Abstract: The selective catalytic reduction (SCR) of nitrogenous oxides is the most promising technique to meet prospective emission regulations of cars. Due to its toxic potential the reducing agent ammonia cannot be stored in a car, but it can be carried in the form of an urea-water-solution (UWS) which is injected into the hot exhaust gas and reacts in different sub-steps to ammonia. This formation of ammonia upstream the catalytic converter is a key factor for the efficiency of the entire SCR-process-chain. This study deals with the numerical optimization of the position and direction of the UWS-injection into the hot exhaust gas. For this purpose a numerical model was developed, which considers in contrast to previous surveys the loss of droplets` weight caused by evaporation and thermal decomposition. The model is able to determine the exact position of flying droplets, the droplets’ velocity, the composition and its current temperature in a gas flow. Comparative investigations of coflow- and counter flow-injection, of centered or off centered injection position of the UWS-injection system to avoid droplet/wall-contact are focused in this survey.

Keywords: Exhaust gas after-treatment, internal combustion engines, NOx, SCR, AdBlue®

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #8, pp. 80-87

Title of the Paper: Saw-Tooth Approximation and Numerical Solution for Flows in Inclined Channels

Authors: Christina G. Georgantopoulou, George A. Georgantopoulos, Nikolaos S. Vasilikos

Abstract: Incompressible flows inside short or extended pipes present multiple industrial applications and their numerical study is essential for the related companies in order to control the flow variables. The present work is a flexible numerical approach and solution for incompressible flows inside inclined channels. Despite of the non-Cartesian channel bound, a saw-tooth Cartesian grid generation methodology is applied in combination with a finite volume scheme in order to predict the flow field as well as the recirculation zones of the flow. The new Cartesian approximated bound is consisted of only grid lines while solutions are provided for laminar viscous flows for various Reynolds numbers. The solution of Navier-Stokes equations is based on an artificial compressibility technique in combination with the flux-vector splitting methodology. We prove that the methodology is independent of the grid size, step angle or expansion ratio of the channel and the final results present satisfied accuracy despite of the geometry approximation which is taking place during the mesh generation. The utility of the algorithms is tested using related results using body fitted grid approach as well as the flow simulation software FLUENT. We conclude that the below method is appropriate for industrial flows study, manly in power industries, reducing the computational time and providing a simple and flexible scheme which easily can be used and modified by engineers without advanced knowledge in CFD.

Keywords: Cartesian grids, inclined pipes, saw-tooth method, incompressible flows, sub – grids, viscous flows

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #7, pp. 69-79

Title of the Paper: Numerical and Approximate Solutions of Boundary Layer Development Due to a Moving Extensible Surface

Authors: Jacob Nagler

Abstract: In this study, several numerical analysis methods were performed for solving boundary layer flow model development due to a moving surface ('sheet'). This model obeys to general stretching law and was presented by Kuiken in 1981. The numerical simulation methods which were used are the shooting method and finite difference method (FDM). Creating the final simulation model involved a calibration step. It was found that the shooting method does not describe properly the fluid physics as compared to finite difference method (FDM). Additionally, comparison between numerical and suggested approximate solutions was done while qualitative compatibility was found between solutions. Kuiken solution branch was found to be fully coincided with current FDM solution for κ=1/3. Finally, comparison between ADM (Adomian Decomposition Method) and FDM has been done, while appropriate match was found between solutions. Quantitatively, all presented solutions have the same order of magnitude; nevertheless, inaccuracy between all kinds of solutions does exist.

Keywords: Shooting method, FDM, Two-dimensional flow, Numerical solution, Approximate solution, Analytical solution, Literature solution, ADM

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #6, pp. 54-68

Title of the Paper: The Effect of Non-Uniform Transverse Friction on the Linear Stability of Shallow Mixing Layers

Authors: Irina Eglite, Andrei Kolyshkin, Inta Volodko

Abstract: Linear stability analysis of mixing layers in shallow water is performed in the present paper under the following assumptions: (a) the fluid contains uniformly distributed heavy small particles, (b) the mixing layer is slightly curved in the longitudinal direction, (c) the friction coefficient changes in the transverse direction. Marginal stability curves are calculated for different base flow velocity profiles which represent both stably and unstably curved mixing layers. The effect of all parameters on the stability characteristics of the flow is investigated.

Keywords: Linear stability, shallow mixing layer, non-uniform friction, curvature

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #5, pp. 47-53

Title of the Paper: Theta Method Comparative Study of 2D Asymmetric Diffusion Problem with Convection on the Wall

Authors: Jacob Nagler

Abstract: In this paper, numerical simulation based on generalized Crank-Nicolson method (which is also known as theta method) was performed in case of 2D diffusion problem with asymmetrical convection B.C on the walls. Also, model calibration was involved during numerical simulation model. Additionally, comparison between numerical and analytical solutions was made while qualitative compatibility was found between solutions. Moreover, maximum error between these solutions was found to be about 7.5%. Comparisons between other studies and current numerical and analytic solutions have been proved to be coincided.

Keywords: Theta method, Diffusion, Crank-Nicolson, Analytical solution, Convection, Asymmetric B.C.

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #4, pp. 35-46

Title of the Paper: Some Aspects of Oscillatory Visco-Elastic Flow Through Porous Medium in a Rotating Porous Channel

Authors: Rita Choudhury, Hillol Kanti Bhattacharjee

Abstract: This paper presents the study of three-dimensional flow and the injection/suction on an oscillatory flow of a visco-elastic incompressible fluid through a highly porous medium bounded between two infinite horizontal porous plates. The fluid injected with constant velocity through the lower stationary plate and is being sucked simultaneously with same constant velocity through the upper plate oscillating in its own plane about a nonzero constant mean velocity. On the basis of certain simplifying assumptions,closed form analytical solutions are therefore constructed and the important properties of the overall structure of the flow are discussed. Emphasis has been given on the effects of the visco-elastic parameter with the combination of other physical parameters.

Keywords: Visco-elastic, oscillatory , porous medium, porous channel , injection/suction, rotational parameter

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #3, pp. 26-34

Title of the Paper: Non-Linear Shallow Water Equations Numerical Integration on Curvilinear Boundary-Conforming Grids

Authors: Giovanni Cannata, Francesco Lasaponara, Francesco Gallerano

Abstract: An Upwind Weighted Essentially Non-Oscillatory scheme for the solution of the Shallow Water Equations on generalized curvilinear coordinate systems is proposed. The Shallow Water Equations are expressed in a contravariant formulation in which Christoffel symbols are avoided. The equations are solved by using a high-resolution finite-volume method incorporated with an exact Riemann Solver. A procedure developed in order to correct errors related to the difficulties of numerically satisfying the metric identities on generalized boundary-conforming grids is presented; this procedure allows the numerical scheme to satisfy the freestream preservation property on highly-distorted grids. The capacity of the proposed model is verified against test cases present in literature. The results obtained are compared with analytical solutions and alternative numerical solutions.

Keywords: 2D Shallow Water Equations, Upwind WENO scheme, Contravariant formulation, Christoffel Symbols, Freestream preservation

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #2, pp. 13-25

Title of the Paper: Radiation and Mass Transfer Effects on Nonlinear MHD Boundary Layer Flow of Liquid Metal over a Porous Stretching Surface Embedded in Porous Medium with Heat Generation

Authors: G. V. Ramana Reddy, K. Jayarami Reddy, R. Lakshmi

Abstract: The present paper analyzes the effects of mass transfer on steady nonlinear MHD boundary layer flow of a viscous incompressible fluid over a nonlinear porous stretching surface embedded in a porous medium in presence of nonlinear radiation and heat generation. The liquid metal is assumed to be gray, emitting, and absorbing but non-scattering medium. Governing nonlinear partial differential equations are transformed to nonlinear ordinary differential equations by utilizing suitable similarity transformation. The resulting nonlinear ordinary differential equations are solved numerically using Runge-Kutta fourth order method along with shooting technique. Comparison with previously published work is obtained and good agreement is found. The effects of various governing parameters on the liquid metal fluid dimensionless velocity, dimensionless temperature, dimensionless concentration, skin-friction coefficient, Nusselt number and Sherwood number are discussed with the aid of graphs.

Keywords: Radiation, Mass transfer, MHD, Stretching surface, porous medium, heat generation

WSEAS Transactions on Fluid Mechanics, ISSN / E-ISSN: 1790-5087 / 2224-347X, Volume 10, 2015, Art. #1, pp. 1-12