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See detailAn experimental and numerical analysis of effects induced by moving bodies in free surface water
Kerger, François ULg; Detrembleur, Sylvain ULg; Archambeau, Pierre ULg et al

in Pagliara Stefano (Ed.) Hydraulic Structures (2008)

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See detailExperimental and numerical analysis of flow instabilities in rectangular shallow basins
Dewals, Benjamin ULg; Kantoush, Sameh; Erpicum, Sébastien ULg et al

in Environmental Fluid Mechanics (2008), 8(1), 31-54

Free surface flows in several shallow rectangular basins have been analyzed experimentally, numerically and theoretically. Different geometries, characterized by different widths and lengths, are ... [more ▼]

Free surface flows in several shallow rectangular basins have been analyzed experimentally, numerically and theoretically. Different geometries, characterized by different widths and lengths, are considered as well as different hydraulic conditions. First, the results of a series of experimental tests are briefly depicted. They reveal that, under clearly identified hydraulic and geometrical conditions, the flow pattern is found to become nonsymmetric, in spite of the symmetrical inflow conditions, outflow conditions and geometry of the basin. This non-symmetric motion results from the growth of small disturbances actually present in the experimental initial and boundary conditions. Second, numerical simulations are conducted based on a depth-averaged approach and a finite volume scheme. The simulation results reproduce the global pattern of the flow observed experimentally and succeed in predicting the stability or instability of a symmetric flow pattern for all tested configurations. Finally, an analytical study provides mathematical insights into the conditions under which the symmetric flow pattern becomes unstable and clarifies the governing physical processes. [less ▲]

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See detailExperimental and numerical analysis of flow instabilities in rectangular shallow basins
Dewals, Benjamin ULg

Scientific conference (2007, March 29)

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See detailAn experimental and numerical analysis of the HCCI auto-ignition process of primary reference fuels, toluene reference fuels and diesel fuel in an engine, varying the engine parameters
Machrafi, Hatim ULg; Cavadias, Simeon; Gilbert, Philippe

in Fuel Processing Technology (2008), 89(11), 1007-1016

For a future HCCI engine to operate under conditions that adhere to environmental restrictions, reducing fuel consumption and maintaining or increasing at the same time the engine efficiency, the choice ... [more ▼]

For a future HCCI engine to operate under conditions that adhere to environmental restrictions, reducing fuel consumption and maintaining or increasing at the same time the engine efficiency, the choice of the fuel is crucial. For this purpose, this paper presents an auto-ignition investigation concerning the primary reference fuels, toluene reference fuels and diesel fuel, in order to study the effect of linear alkanes, branched alkanes and aromatics on the auto-ignition. The auto-ignition of these fuels has been studied at inlet temperatures from 25 to 120 degrees C, at equivalence ratios from 0.18 to 0.53 and at compression ratios from 6 to 13.5, in order to extend the range of investigation and to assess the usability of these parameters to control the auto-ignition. It appeared that both iso-octane and toluene delayed the ignition with respect to n-heptane, while toluene has the Strongest effect. This means that aromatics have higher inhibiting effects than branched alkanes. In an increasing order, the inlet temperature, equivalence ratio and compression ratio had a promoting effect on the ignition delays. A previously experimentally validated reduced surrogate mechanism, for mixtures of n-heptane, iso-octane and toluene, has been used to explain observations of the auto-ignition process. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailAn experimental and numerical analysis of the influence of the inlet temperature, equivalence ratio and compression ratio on the HCCI auto-ignition process of Primary Reference Fuels in an engine
Machrafi, Hatim ULg; Cavadias

in Fuel Processing Technology (2008), 89(11), 1218-1226

In order to understand better the auto-ignition process in an HCCI engine, the influence of some important parameters on the auto-ignition is investigated. The inlet temperature, the equivalence ratio and ... [more ▼]

In order to understand better the auto-ignition process in an HCCI engine, the influence of some important parameters on the auto-ignition is investigated. The inlet temperature, the equivalence ratio and the compression ratio were varied and their influence on the pressure, the heat release and the ignition delays were measured, The inlet temperature was changed from 25 to 70 degrees C and the equivalence ratio from 0.18 to 0.41, while the compression ratio varied from 6 to 13.5. The fuels that were investigated were PRF40 and n-heptane. These three parameters appeared to decrease the ignition delays, with the inlet temperature having the least influence and the compression ratio the most. A previously experimentally validated reduced surrogate mechanism, for mixtures of n-heptane, iso-octane and toluene, has been used to explain observations of the auto-ignition process. The same kinetic mechanism is used to better understand the underlying chemical and physical phenomena that make the influence of a certain parameter change according to the operating conditions. This can be useful for the control of the auto-ignition process in an HCCI engine. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailExperimental and Numerical Approaches of Contact with Friction and Wear in Large Deformation
Cescotto, Serge ULg; Charlier, Robert ULg; Bricout, J. P. et al

in European Journal of Mechanical Engineering (1991), 36(n° 2),

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See detailExperimental and numerical investigation of a meandering jet in shallow rectangular reservoirs under different hydraulic conditions
Camnasio, Erica; Pirotton, Michel ULg; Erpicum, Sébastien ULg et al

in 3rd International Symposium on Shallow Flows (2012, June)

A central meandering jet in shallow rectangular reservoirs has been investigated numerically by the model WOLF2D, on the basis of experimental evidence of this type of flow field in two different setups ... [more ▼]

A central meandering jet in shallow rectangular reservoirs has been investigated numerically by the model WOLF2D, on the basis of experimental evidence of this type of flow field in two different setups at different scales. A sensitivity analysis has been conducted with respect to the main parameters of the model. The oscillation frequency of the transversal velocity and the characteristic Strouhal number have been calculated for different Froude numbers. A logarithmic relationship has been found between the Strouhal and the Froude numbers. [less ▲]

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See detailExperimental and numerical investigation of high-strength steel circular columns subjected to fire
Tondini, Nicola; Hoang, Van Long ULg; Demonceau, Jean-François ULg et al

in Journal of Constructional Steel Research (2013), 80

This paper presents an experimental–numerical study on the behaviour of High Strength Steel (HSS) columns at elevated temperature, both on Circular Hollow Sections (CHS) and on a Concrete Filled Tube (CFT ... [more ▼]

This paper presents an experimental–numerical study on the behaviour of High Strength Steel (HSS) columns at elevated temperature, both on Circular Hollow Sections (CHS) and on a Concrete Filled Tube (CFT). The measured yield strength of the circular sections was in the order of 820 MPa. In detail, three HSS CHS and a HSS CFT were tested under the standard ISO fire with constant eccentric compression applied load. The evolution of temperature and deformation patterns were measured by means of a comprehensive instrumentation made of thermocouples and displacement transducers. Numerical analyses were performed and compared with experimental data by employing stress–strain relationships of carbon steel at elevated temperatures provided by the Eurocodes associated to two different sets of reduction factors: i) those provided by the Eurocodes valid up to S460 steel grades; and ii) those proposed in the literature and based on tests on HSS. [less ▲]

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See detailExperimental and Numerical Investigation of Mixed Flow in a Gallery
Erpicum, Sébastien ULg; Kerger, François ULg; Archambeau, Pierre ULg et al

in Transaction: Engineering Sciences, volume 1, Computational Methods in Multiphase Flow V (2009, June)

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See detailAn experimental and numerical investigation on the influence of external gas recirculation on the HCCI autoignition process in an engine: Thermal, diluting, and chemical effects
Machrafi, Hatim ULg; Cavadias, Simeon; Guibert, Philippe

in Combustion & Flame (2008), 155(3), 476-489

In order to contribute to the solution of controlling the autoignition in a homogeneous charge compression ignition (HCCI) engine, parameters linked to external gas recirculation (EGR) seem to be of ... [more ▼]

In order to contribute to the solution of controlling the autoignition in a homogeneous charge compression ignition (HCCI) engine, parameters linked to external gas recirculation (EGR) seem to be of particular interest. Experiments performed with EGR present some difficulties in interpreting results using only the diluting and thermal aspect of EGR. Lately, the chemical aspect of EGR is taken more into consideration, because this aspect causes a complex interaction with the dilution and thermal aspects of EGR. This paper studies the influence of EGR on the autoignition process and particularly the chemical aspect of EGR. The diluents present in EGR are stimulated by N-2 and CO2, with dilution factors going from 0 to 46 vol%. For the chemically active species that could be present in EGR, the species 0 and 170 ppm, while that of CH2O alters between 0 and 1400 ppm. For the investigation of the effect of the chemical species on the autoignition, a fixed dilution factor of 23 vol% and a fixed EGR temperature of 70 degrees C are maintained. The inlet temperature is held at 70 degrees C, the equivalence ratios between 0.29 and 0.41, and the compression ratio at 10.2. The fuels used for the autoignition are n-heptane and PRF40. It appeared that CO, in the investigated domain, did not influence the ignition delays, while NO had two different effects. At concentrations up until 45 ppm, NO advanced that ignition delays for the PRF40 and at higher concentrations, the ignition delayed. The influence of NO on the autoignition of n-heptane seemed to be insignificant, probably due to the higher burn rate of n-heptane. CH2O seemed to delay the ignition. The results suggested that especially the formation of OH radicals or their consumption by the chemical additives determines how the reactivity of the autoignition changed. (C) 2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved. [less ▲]

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See detailExperimental and numerical investigations for I-girders in bending and shear stiffened by closed trapezoidal stiffeners
Boissonnade, N.; Degée, Hervé ULg; Naumes, J. et al

in Proceedings of the ICMS Conference (2006)

The paper investigates the shear resistance of I-girders longitudinally stiffened by closed trape-zoidal stiffeners. It first reports on 4 full-scale tests performed at RWTH Aachen, on stiffened panels ... [more ▼]

The paper investigates the shear resistance of I-girders longitudinally stiffened by closed trape-zoidal stiffeners. It first reports on 4 full-scale tests performed at RWTH Aachen, on stiffened panels with strong closed stiffeners. As expected, failure in the subpanels has been governing. A devoted FEA shell model is then described and validated towards these results and other experimental sources. Parametric stud-ies led with the numerical tool help pointing out several aspects where the Eurocode 3 Part 1.5 recommenda-tions on stiffened panels in bending and shear may be improved. [less ▲]

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See detailExperimental and numerical investigations for I-girders in bending and shear stiffened by closed trapezoidal stiffeners for use in steel bridges
Feldmann, M.; Naumes, J.; Oppe, M. et al

in Proceedings of the IABSE Symposium "Improving infrastructures..." (2007)

The paper summarizes the investigations on shear resistance of I-girders longitudinally stiffened by closed trapezoidal stiffeners, performed in the frame of a European RFCS project (RFS-CR-03018 ... [more ▼]

The paper summarizes the investigations on shear resistance of I-girders longitudinally stiffened by closed trapezoidal stiffeners, performed in the frame of a European RFCS project (RFS-CR-03018) designated as “ComBri” (Competitive Steel and Composite Bridges by improved Steel Plated Structures), with configurations typical of what may be expected in the design of modern steel bridges. It first reports on four full-scale tests performed at RWTH Aachen, on stiffened panels with strong closed stiffeners where the deformations have been measured with photogrammetric devices. As expected, failure in the subpanels has been governing. A devoted FEA shell model is then described and validated towards these results and other experimental sources. The numerical simulations demonstrate a very good agreement with the test-results. Parametric studies performed with a sophisticated numerical tool help pointing out several aspects where the recommendations of EN 1993-1-5 [1] on stiffened panels in bending and shear may be improved. [less ▲]

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See detailExperimental and numerical investigations for I-Girders in bending and shear stiffened by trapezoidal stiffeners
Boissonnade, N.; Degée, Hervé ULg; Naumes, J. et al

in Advanced Steel Construction (2008), 4(1), 1-13

The paper investigates the shear resistance of I-girders longitudinally stiffened by trapezoidal stiffeners. It first reports on 4 full-scale tests performed at RWTH Aachen, on stiffened panels with ... [more ▼]

The paper investigates the shear resistance of I-girders longitudinally stiffened by trapezoidal stiffeners. It first reports on 4 full-scale tests performed at RWTH Aachen, on stiffened panels with strong closed stiffeners. As expected, failure in the subpanels has been governing. A devoted FEA shell model is then described and validated towards these results and other experimental sources. Parametric studies led with the numerical tool help pointing out several aspects where the Eurocode 3 Part 1.5 recommendations on stiffened panels in bending and shear may be improved. [less ▲]

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See detailExperimental and numerical investigations of dike-break induced flows
Roger, Sebastian; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

in Journal of Hydraulic Research (2009), 47(3), 349-359

Experimental model data are compared with numerical computations of dike-break induced flows, focusing on the final steady state. An idealised scale model was designed reproducing the specific boundary ... [more ▼]

Experimental model data are compared with numerical computations of dike-break induced flows, focusing on the final steady state. An idealised scale model was designed reproducing the specific boundary conditions of dike breaks. Discharges, water levels and depth profiles of horizontal velocities were recorded and validated by numerical modeling. The latter was performed by two different models solving the two-dimensional depth-averaged shallow water equations, namely a total variation diminishing Runge-Kutta dis¬continuous Galerkin finite element method, and a finite volume scheme involving a flux vector splitting ap¬proach. The results confirmed convergence and general applicability of both methods for dike-break prob¬lems. As regards their accuracy, the basic flow pattern was satisfactorily reproduced yet with differences compared to the measurements. Hence, additional simulations by a finite volume model were performed con¬sidering various turbulence closures, wall-roughnesses as well as non-uniform Boussinesq coefficients. [less ▲]

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See detailExperimental and Numerical Investigations of the Aeroelastic Stability of Bluff Structures
Andrianne, Thomas ULg

Doctoral thesis (2012)

The study of the dynamic interactions between the wind and civil engineering structures has become increasingly important over the last few decades. Most of these structures are aerodynamically "bluff ... [more ▼]

The study of the dynamic interactions between the wind and civil engineering structures has become increasingly important over the last few decades. Most of these structures are aerodynamically "bluff" and are becoming more flexible. Bluff-body aeroelasticity is a very challenging research area due to the unsteadiness and nonlinearity of the aerodynamic loading. This thesis presents the investigation of three aeroelastic phenomena affecting bluff-bodies: Vortex Induced Vibration (VIV), Galloping and Torsional Flutter. For each instability, extensive experimental studies are carried out in the wind tunnel. Innovative analysis, based on the Common-base Proper Orthogonal Decomposition (CPOD) method is used to study the flow visualization data. The VIV phenomenon is studied on a flexible tube with a circular cross-section, supported from its midpoint. A CPOD-based input-output model is developed to describe the system. The galloping instability is studied on a generic bridge section. A complete analysis of the aeroelastic behaviour of the structure is presented and a new polynomial empirical model is developed, which reflects accurately the nonlinear nature of the system. The torsional flutter phenomenon is extensively studied for two different structures: a generic bridge deck and a rectangular cylinder. The Motion Induced Vortex is identified as the fundamental cause of this aeroelastic phenomenon, on the basis of the analysis of the flow around the oscillating rectangle. In addition, it is demonstrated that the quasi-steady theory is not adapted to estimate the onset velocity of torsional flutter. Finally, a 2D aeroelastic simulation code, based on the Discrete Vortex Method (DVM) is developed. The non-linear aerodynamics around the body are well reproduced, allowing the simulation of all the aeroelastic instabilities investigated experimentally. [less ▲]

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See detailExperimental and numerical investigations of the torsional flutter oscillations of a 4:1 rectangular cylinder
Andrianne, Thomas ULg; Dimitriadis, Grigorios ULg

in Journal of Fluids & Structures (2013), 41

The torsional flutter oscillations of a 4:1 rectangular cylinder around its pitching axis are investigated through wind tunnel experiments and numerical simulations. The rectangle’s responses to different ... [more ▼]

The torsional flutter oscillations of a 4:1 rectangular cylinder around its pitching axis are investigated through wind tunnel experiments and numerical simulations. The rectangle’s responses to different initial conditions and turbulence excitations at various wind tunnel airspeeds are recorded. Timeresolved Particle Image Velocimetry measurements are taken at two different airspeeds, when the rectangle undergoes Limit Cycle Oscillations. Aeroelastic simulations are carried out using the Discrete Vortex Method and the resulting responses are compared to the experimental measurements. The Common-base Proper Orthogonal Decomposition method is used to analyse and compare the measured and simulated unsteady flow fields around the rectangle. A discussion of the participation of each mode in the different states of the flow-field is presented, at two different amplitudes of oscillation. The Motion Induced Vortex (MIV) is identified as the fundamental cause of the torsional flutter phenomenon and its role over a complete cycle is studied. MIV-induced oscillations can be started either by a suitable initial disturbance or by a second, nearly linear self-excited instability that causes negative aerodynamic damping. The combination of these two instabilities results in a complete description of the torsional flutter of the rectangle. [less ▲]

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See detailExperimental and numerical investigations on iron columns reinforced by FRP under axial compression
Ly, Dong Phuong Lam ULg; Jaspart, Jean-Pierre ULg; Demonceau, Jean-François ULg et al

in Camelbeeck, Th.; Degée, Hervé; Degrande, G. (Eds.) et al Seismic risk (2008, September 11)

This paper presents experimental and numerical investigations on iron columns under axial compression, strengthened with high modulus carbon fibre reinforced polymer (FRP) sheets. It is shown that the ... [more ▼]

This paper presents experimental and numerical investigations on iron columns under axial compression, strengthened with high modulus carbon fibre reinforced polymer (FRP) sheets. It is shown that the resistance and stiffness of iron columns can be increased significantly with the use of longitudinal FRP sheets as a result of the reduction of the column slenderness, but also that transverse FRP sheets should be used to prevent any local buckling of the longitudinal FRP sheets. [less ▲]

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