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See detailExperimental Analysis of the Bifurcation Behaviour of a Bridge Deck Undergoing Across-Wind Galloping
Andrianne, Thomas ULg; Dimitriadis, Grigorios ULg

in De Roeck, G.; Degrande, G.; Lombaert, G. (Eds.) et al Proceedings of the 8th International Conference on Structural Dynamics, EURODYN 2011 (2011, July 05)

The phenomenon of aeroelastic galloping is a very important design consideration for bridges and other slender structures. It has been investigated by a number of researchers but, most frequently, the ... [more ▼]

The phenomenon of aeroelastic galloping is a very important design consideration for bridges and other slender structures. It has been investigated by a number of researchers but, most frequently, the analysis is limited to quasi-steady aerodynamic and linearized aeroelastic considerations. Such treatment has been shown to be effective for simple cross-sectional shapes, such as rectangles. In this work, an aeroelastic model of a realistic bridge deck cross-section is tested in a low speed wind tunnel. Both static and dynamic tests are carried out and the resulting force and vibration measurements are presented. The static force results are used to set up a quasi-steady mathematical model. The dynamic responses are used to draw a complete bifurcation diagram within a chosen airspeed range and to discuss the stability of the system. It is shown that the experimental system undergoes a subcritical Hopf bifurcation, its phase space including both a stable and an unstable limit cycle. As consequence, throughout the chosen airspeed, the system can either remain stable or undergo limit cycle oscillations. The quasi-steady analysis fails completely in capturing this type of behaviour. The predicted galloping onset speed is too conservative and the predicted oscillation amplitudes too high. The reason for this failure is the fact that the quasi-steady mathematical model is incapable of modelling subcritical Hopf bifurcations. [less ▲]

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See detailExperimental Analysis of the Effects of Particulate Fouling on Heat Exchanger Heat Transfer and Air-Side Pressure Drop for a Hybrid Dry Cooler
Bell, Ian ULg; Groll, Eckhard; Konig, Holger

in Heat Transfer Engineering (2011), 32

It is well known that significant fouling by particulate matter can have a deleterious effect on the performance of enhanced surface heat exchangers, and the same is true for hybrid heat exchangers ... [more ▼]

It is well known that significant fouling by particulate matter can have a deleterious effect on the performance of enhanced surface heat exchangers, and the same is true for hybrid heat exchangers. Hybrid heat exchangers are heat exchangers which are typically run in dry mode to reject heat. When the ambient conditions require more heat rejection than can be provided by sensible heat transfer a water pump is turned on and water flows over the fins and the evaporation of water provides a further cooling effect. Fouling in dry mode operation is physically similar to that of air-cooled heat exchangers, but in evaporative mode the flow of the water over the coil eliminates the impact of fouling. A hybrid dry cooler heat exchanger of 60 cm x 60 cm frontal area has been installed in a well-instrumented wind tunnel to measure the heat exchanger’s performance. Hot water flows through the coil to provide the load, and air flows over the coil to provide cooling. During evaporative mode operation another stream of water flows over the outside face of the coil, adhering mainly to the louvered fins. The louvered fins are specially designed for optimized water flow during wetting mode. The fins are made of aluminum, the tubes are copper, and protection against corrosion is realized by a special E-coating. This coil has been tested clean and fouled with ASHRAE standard dust, for both dry and wet operation. Results are presented for the air side pressure drop and overall heat transfer conductance of the coil under all conditions for which 50% increases in air-side pressure drop are found under heavy fouling. The influence of fouling on heat transfer is small. Also, using the wetting water to wash the fouling off the coil is investigated, and found to be of some limited utility. [less ▲]

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See detailExperimental analysis of the stability of coarse sediments
Duma, Diana-Maria ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Symposium on Two-phase Modelling for Sediment Dynamics in Geophysical Flows (2013, June 12)

To predict the inception of sediment motion, Shields diagram remains the most widely used criterion in engineering practice so far. However, this approach faces several limitations and a number of gaps in ... [more ▼]

To predict the inception of sediment motion, Shields diagram remains the most widely used criterion in engineering practice so far. However, this approach faces several limitations and a number of gaps in knowledge still remain. The present research aims to provide new knowledge about the inception of motion in rivers with coarse sediments. A series of experiments was conducted in a flume horizontal 6 m long and 15 cm wide. The bottom was paved, either entirely or partly, with gravels of approximately 12 mm in diameter. Ultrasonic sensors were used to measure the water depth, a flowmeter for the discharge, an ultrasonic velocity profiler (UVP) transducer for the flow velocity. Three different thresholds were defined to distinguish between the following states: no motion, vibration of stones, local motion, and large scale motion. The overwhelming influence of turbulence was emphasized by the conducted tests. This paper details the results of these experiments and demonstrates the need for further research in order to better quantify these effects. [less ▲]

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See detailExperimental and analytical investigations on single-sided composite joint configuration
Demonceau, Jean-François ULg; Jaspart, Jean-Pierre ULg

in Walraven, Joost; Blaauwendraad, Johan; Scarpas, Tom (Eds.) et al 5th International PhD Symposium in Civil Engineering (2004, June 16)

For three years, in the framework of a European research project funded by the European Community for Steel and Coal (ECSC) in which the Liège University was deeply involved, intensive experimental ... [more ▼]

For three years, in the framework of a European research project funded by the European Community for Steel and Coal (ECSC) in which the Liège University was deeply involved, intensive experimental, numerical and theoretical investigations have been carried out on the behaviour of composite sway buildings under static and seismic loading. This paper presents experimental and analytical studies carried out at Liège University, as part of the above European project, with the objective to investigate the behaviour of a single-sided composite joint configuration under static loading. A particular failure mode occurred during the experimental tests, which had not yet been detected previously; it is described in details. Then, an analytical formula covering this particular phenomenon and based on a theoretical model is presented; it is validated through comparisons with experimental results. [less ▲]

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See detailExperimental and analytical investigations on the behaviour of building frames further to a column loss
Demonceau, Jean-François ULg; Jaspart, Jean-Pierre ULg

in Mazzolani, F.; Mistakidis, E.; Borg, R. P. (Eds.) et al Urban Habitat Constructions under Catastrophic Events (2008, October 23)

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See detailExperimental and analytical investigations on the response of structural building frames further to a column loss
Demonceau, Jean-François ULg; Jaspart, Jean-Pierre ULg

(2009, May)

Recent events such as natural catastrophes or terrorism attacks have highlighted the necessity to ensure the structural integrity of buildings under exceptional events. Design requirements are proposed in ... [more ▼]

Recent events such as natural catastrophes or terrorism attacks have highlighted the necessity to ensure the structural integrity of buildings under exceptional events. Design requirements are proposed in some codes but are generally not satisfactory. In particular, it is not demonstrated that, even if these requirements are respected, a structure subjected to an exceptional event will really behave properly. A European RFCS project called “Robust structures by joint ductility” has been set up in 2004, for three years, with the aim to provide requirements and practical guidelines so as to ensure the structural integrity of steel and composite structures under exceptional events through an appropriate robustness. The investigations performed at the University of Liège, as part of this European project, are mainly dedicated to the exceptional event “loss of a column in a steel or steel-concrete composite building frame”; the main objective is to develop a simplified analytical procedure to predict the frame response further to a column loss. The development of this simplified procedure is detailed in two complementary PhD theses: the thesis of Demonceau J.-F. and the thesis of Luu N.N.H. Present paper describes experimental and analytical studies carried out in [Demonceau, 2008]. In particular, a simplified analytical procedure for the prediction of the global frame response when significant membrane forces develop further to a column loss will be described; it allows: (i) to predict the development of the catenary action in a frame with joints subjected to combined bending moment and tension loads and (ii) to compute the requested rotation capacity at the joint level according to the loads applied on the frame. [less ▲]

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See detailExperimental and computational study of the correlation between oxygen tension, cell viability and proliferation in fibrin hydrogels
Demol, J.; Lambrechts, D.; Geris, Liesbet ULg et al

in Proceedings of the 17th conference of the European Society of Biomechanics (2010)

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See detailExperimental and Computational Study of the Structural and Electronic Properties of Fe II(2,20-bipyridine)(mes) 2 and [Fe II(2,20-bipyridine)(mes) 2] -, a Complex Containing a 2,20-Bipyridyl Radical Anion
Irwin, Mark; Jenkins, Rhiannon; Denning, Mark et al

in Inorganic Chemistry (2010), 49

Addition of potassium metal and 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) to a tetrahydrofuran (THF) solution of Fe(2,20 -bipyridine)(mes)2 (1; mes = 2,4,6-Me3C6H2) yielded ... [more ▼]

Addition of potassium metal and 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) to a tetrahydrofuran (THF) solution of Fe(2,20 -bipyridine)(mes)2 (1; mes = 2,4,6-Me3C6H2) yielded the anionic complex [Fe(2,20 -bipyridine)(mes)2] - which was isolated as [K(2,2,2-crypt)][Fe(2,20 -bipyridine)(mes) 2](2) alongside the side-product [K(2,2,2-crypt)][Fe(mes)3] 3 C6H12 (3). A compositionally pure sample of 2 was obtained by dissolving a mixture of 2 and 3 in dry pyridine and layering the resulting solution with toluene. Solid state magnetic susceptibility measurements on 1 reveal Curie-Weiss paramagnetic behavior with a molar magnetic moment of 5.12(1) μB between 20 and 300 K, a value which is in line with the expected iron(II) spin-only value of 4.90 μB. The magnetic measurements carried out on 2 reveal more complex temperature dependent behavior consistent with intramolecular antiferromagnetic coupling (J=-46 cm -1) between the unpaired electrons of the iron(II) ion (S Fe =2) and a π* orbital of the bipyridyl radical (Sbipy = 1/2). Structural data, M€ossbauer and electron paramagnetic resonance (EPR) spectroscopic measurements, and density functional theory (DFT) calculations are all consistent with this model of the electronic structure. To the best of our knowledge, species 2 represents the first crystallographically characterized transition metal complex of the 2,20 -bipyridyl ligand for which magnetic, spectroscopic, and computational data indicate the presence of an unpaired electron in the π* antibonding orbital. [less ▲]

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See detailExperimental And Conformational Analyses Of Interactions Between Butenafine And Lipids
Mingeot-Leclercq, Mp.; Gallet, X.; Flore, Christelle ULg et al

in Antimicrobial Agents and Chemotherapy (2001), 45(12), 3347-54

Butenafine (N-4-tert-butylbenzyl-N-methyl-1-naphtalenemethylamine hydrochloride) is an antifungal agent of the benzylamine class that has excellent therapeutic efficacy and a remarkably long duration of ... [more ▼]

Butenafine (N-4-tert-butylbenzyl-N-methyl-1-naphtalenemethylamine hydrochloride) is an antifungal agent of the benzylamine class that has excellent therapeutic efficacy and a remarkably long duration of action when applied topically to treat various mycoses. Given the lipophilic nature of the molecule, efficacy may be related to an interaction with cell membrane phospholipids and permeabilization of the fungal cell wall. Similarly, high lipophilicity could account for the long duration of action, since fixation to lipids in cutaneous tissues might allow them to act as local depots for slow release of the drug. We have therefore used computer-assisted conformational analysis to investigate the interaction of butenafine with lipids and extended these observations with experimental studies in vitro using liposomes. Conformational analysis of mixed monolayers of phospholipids with the neutral and protonated forms of butenafine highlighted a possible interaction with both the hydrophilic and hydrophobic domains of membrane phospholipids. Studies using liposomes demonstrated that butenafine increases membrane fluidity [assessed by fluorescence polarization of 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene and 1,6-diphenylhexatriene] and membrane permeability (studied by release of calcein from liposomes). The results show, therefore, that butenafine readily interacts with lipids and is incorporated into membrane phospholipids. These findings may help explain the excellent antifungal efficacy and long duration of action of this drug when it is used as a topical antifungal agent in humans. [less ▲]

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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)

Detailed reference viewed: 60 (22 ULg)