References of "Huynen, Alexandre"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailEulerian Formulation of Elastic Rods
Huynen, Alexandre ULiege; Detournay, Emmanuel; Denoël, Vincent ULiege

in Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences (2016), 472(2190),

In numerous biological, medical and engineering applications, elastic rods are constrained to deform inside or around tube-like surfaces. To solve efficiently this class of problems, the equations ... [more ▼]

In numerous biological, medical and engineering applications, elastic rods are constrained to deform inside or around tube-like surfaces. To solve efficiently this class of problems, the equations governing the deflection of elastic rods are reformulated within the Eulerian framework of this generic tubular constraint defined as a perfectly stiff canal surface. This reformulation hinges on describing the rod deformed configuration by means of its relative position with respect to a reference curve, defined as the axis or spine curve of the constraint, and on restating the rod local equilibrium in terms of the curvilinear coordinate parameterizing this curve. Associated with a segmentation strategy, which partitions the global problem into a sequence of rod segments either in continuous contact with the constraint or free of contact (except for their extremities), this approach not only trivializes the detection of new contacts but also suppresses the isoperimetric constraints resulting from the self-feeding feature of these elementary problems and the imposition of the rod position at the extremities of each rod segments. [less ▲]

Detailed reference viewed: 34 (13 ULiège)
Full Text
Peer Reviewed
See detailTowards an Novel Stiff String Model for the Torque and Drag Problem
Huynen, Alexandre ULiege

Conference (2016, May)

The petroleum industry relies on several kilometer long drillstrings to transmit the axial force and torque necessary to drill the rock formations and reach deep hydrocarbon reservoirs. The assessment of ... [more ▼]

The petroleum industry relies on several kilometer long drillstrings to transmit the axial force and torque necessary to drill the rock formations and reach deep hydrocarbon reservoirs. The assessment of the energy loss along the drillstring, known as the torque and drag problem, plays an essential role in well planning and drilling as the friction appearing at the contacts between the drillstring and the borehole may dramatically increase the costs or, even, be a limiting factor in some configurations. The identification of the number of contacts as well as their positions and extents constitutes the central concern of this question. The nonlinearities associated with the large deflection of the drillstring and the non-penetration condition as well as the a priori unknown number of contacts, however, make the use of conventional numerical tools rather inefficient. To circumvent these difficulties, a simplified stiff string model is derived. Partitioning the global problem in segments of drillstring either in continuous contact with the borehole or free of contact between their extremities, the originality of the proposed formulation lies in the descripion of the drillstring deflection as perturbation of the well-path. [less ▲]

Detailed reference viewed: 36 (3 ULiège)
Full Text
Peer Reviewed
See detailSurface Constrained Elastic Rods with Application to the Sphere
Huynen, Alexandre ULiege; Detournay, Emmanuel; Denoël, Vincent ULiege

in Journal of Elasticity (2016)

The unilateral contact between an elastic rod and a rigid surface is encountered in numerous biological and engineering applications. Along continuous contacts, the centerline of the rod reflects the ... [more ▼]

The unilateral contact between an elastic rod and a rigid surface is encountered in numerous biological and engineering applications. Along continuous contacts, the centerline of the rod reflects the geometry of the constraining surface. This restriction of the rod axis to surface bound configurations enters its local equilibrium through a reaction pressure which ensures the compatibility between the deformation and the restraint geometry. The classic equations governing the static equilibrium of elastic rods are particularized to surface bound configurations by (i) specifying the location of the rod axis in terms of its coordinates in the parameter space associated with the constraining surface parameterization, and (ii) characterizing the orientation of its material frame through its rotation with respect to the surface normal. This formulation, which emphasizes the relations between the rod configuration and the geometry of the constraint, also leads to an expression for the reaction pressure. This approach is then validated on a spherical surface by comparing with known solutions for elastic curves, i.e., inextensible and twist free rods. [less ▲]

Detailed reference viewed: 56 (11 ULiège)
Full Text
See detailEulerian Formulation of Spatially Constrained Elastic Rods
Huynen, Alexandre ULiege

Doctoral thesis (2015)

Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is ... [more ▼]

Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is in contact with a stiff constraining surface. The research work presented in this doctoral dissertation formulates a computational model for the solution of elastic rods constrained inside or around frictionless tube-like surfaces. The segmentation strategy adopted to cope with this complex class of problems consists in sequencing the global problem into, comparatively simpler, elementary problems either in continuous contact with the constraint or contact-free between their extremities. Within the conventional Lagrangian formulation of elastic rods, this approach is however associated with two major drawbacks. First, the boundary conditions specifying the locations of the rod centerline at both extremities of each elementary problem lead to the establishment of isoperimetric constraints, i.e., integral constraints on the unknown length of the rod. Second, the assessment of the unilateral contact condition requires, in principle, the comparison of two curves parametrized by distinct curvilinear coordinates, viz. the rod centerline and the constraint axis. Both conspire to burden the computations associated with the method. To streamline the solution along the elementary problems and rationalize the assessment of the unilateral contact condition, the rod governing equations are reformulated within the Eulerian framework of the constraint. The methodical exploration of both types of elementary problems leads to specific formulations of the rod governing equations that stress the profound connection between the mechanics of the rod and the geometry of the constraint surface. The proposed Eulerian reformulation, which restates the rod local equilibrium in terms of the curvilinear coordinate associated with the constraint axis, describes the rod deformed configuration by means of either its relative position with respect to the constraint axis (contact-free segments) or its angular position on the constraint surface (continuous contacts.) This formulation circumvents both drawbacks that afflict the conventional Lagrangian approach associated with the segmentation strategy. As the a priori unknown domain, viz. the rod length, is substituted for the known constraint axis, the free boundary problem and the associated isoperimetric constraints are converted into a classical two-point boundary value problem. Additionally, the description of the rod deflection by means of its eccentricity with respect to the constraint axis trivializes the assessment of the unilateral contact condition. Along continuous contacts, this formulation expresses the strain variables, measuring the rod change of shape, in terms of the geometric invariants of the constraint surface, and emphasizes the influence of the constraint local geometry on the reaction pressure. Formalizing the segmentation strategy, a computational model that exploits the Eulerian formulation of the rod governing equations is devised. To solve the quasi-static deflection of elastic rods constrained inside or around a tube-like surface, this computational model identifies the number of contacts, their nature (either discrete or continuous), and the rod configuration at the connections that satisfies the unilateral contact condition and preserves the rod integrity along the sequence of elementary problems. [less ▲]

Detailed reference viewed: 101 (23 ULiège)
Full Text
Peer Reviewed
See detailA Remark on the Poroelastic Center of Dilation
Huynen, Alexandre ULiege; Detournay, Emmanuel

in Journal of Elasticity (2014), 116(2), 189-206

In the original derivation due to Dougall (1897), the center of dilation is constructed from the superposition of orthogonal force dipoles. However, it can also be built by combining dislocation dipoles ... [more ▼]

In the original derivation due to Dougall (1897), the center of dilation is constructed from the superposition of orthogonal force dipoles. However, it can also be built by combining dislocation dipoles. While the two representations are equivalent in elasticity, the different nature of the force and dislocation dipoles leads to different transient behaviors in poroelasticity, when the response evolves from undrained to drained. Indeed, we show that the poroelastic solution of a center of dilation is obtained by superposing the corresponding elastic solution and either an instantaneous fluid sink or an instantaneous fluid source, depending on whether the center of dilation is treated as a singular stress or displacement discontinuity. A simple explanation to the instantaneous injection or withdrawal of a finite volume of fluid from/to the singularity is given by adopting an exploded view of the poroelastic center of dilation. The exploration of the drained, undrained and transient responses of this singularity also requires to clarify the close relationship between an instantaneous fluid source and a continuous fluid dodecapole, an object constructed by collapsing onto a point three orthogonal pairs of fluid dipoles. [less ▲]

Detailed reference viewed: 52 (19 ULiège)
Full Text
See detailEulerian Formulation of the Torque and Drag Problem
Huynen, Alexandre ULiege; Detournay, Emmanuel; Denoël, Vincent ULiege

in Detournay, Emmanuel; Denoël, Vincent; van de Wouw, Nathan (Eds.) Third International Colloquium on Nonlinear Dynamics and Control of Deep Drilling Systems (2014, May)

Detailed reference viewed: 67 (26 ULiège)
Full Text
Peer Reviewed
See detailEulerian Formulation for an Extensible Elastic Rod
Huynen, Alexandre ULiege; Detournay, Emmanuel; Denoël, Vincent ULiege

in Proceedings of the Fifth International Conference on Structural Engineering, Mechanics and Computation (2013, September)

This paper reformulates the governing equations of an extensible elastic rod by reference to a given spatial curve. This Eulerian formulation is motivated by the need to solve efficiently the constrained ... [more ▼]

This paper reformulates the governing equations of an extensible elastic rod by reference to a given spatial curve. This Eulerian formulation is motivated by the need to solve efficiently the constrained elastica problem encountered in many medical and engineering applications, in which a thin rod is inserted in a tortuous conduit. The Eulerian reformulation of the equations hinges on the restatement of the rod local equilibrium in terms of derivatives with respect to the curvilinear coordinate associated with the reference curve and the description of the rod deflection as a perturbation of this curve. The originality of the proposed formulation lays in the axially unconstrained character of the resulting system such that the determination of the rod configuration between two fixed points reduces to the resolution of a classical boundary value problem. [less ▲]

Detailed reference viewed: 124 (46 ULiège)
See detailPoroelastic Center of Dilation Revisited
Huynen, Alexandre ULiege; Detournay, Emmanuel

Conference given outside the academic context (2013)

Detailed reference viewed: 17 (3 ULiège)
Full Text
Peer Reviewed
See detailPoroelastic Center of Dilation Revisited
Huynen, Alexandre ULiege; Detournay, Emmanuel

in Hellmich, Christian; Pichler, Bernhard; Dietmar, Adam (Eds.) Poromechanics V: Proceedings of the Fifth Biot Conference on Poromechanics (2013, July)

A comparison of the original elastic solution for the center of dilation with the classic Lame ́ solution reveals an unexpected dependence of the center of dilation solu- tion on Poisson’s ratio. This ... [more ▼]

A comparison of the original elastic solution for the center of dilation with the classic Lame ́ solution reveals an unexpected dependence of the center of dilation solu- tion on Poisson’s ratio. This inconsistency is investigated by means of two alternative representations of the singularity which lead to the identification of a compressed zone inside the singularity. The poroelastic equivalent to this nucleus of strain is shown to be the superposition of the elastic one with drained material parameters and an instan- taneous point fluid source associated with a finite volume of fluid that is expelled from the compressed region inside the singularity and is injected in the porous medium. [less ▲]

Detailed reference viewed: 35 (11 ULiège)
Full Text
See detailEulerian Formulation of the Constrained Spatial Elastica
Huynen, Alexandre ULiege

Report (2013)

Detailed reference viewed: 40 (3 ULiège)
Full Text
See detailPoroelastic Center of Dilation Revisited
Huynen, Alexandre ULiege

Master of advanced studies dissertation (2012)

In both elasticity and poroelasticity, the nucleus of strain is usually used to refer to a singular solution such as the point force, the force dipole, the centers of rotation and dilation, etc. These ... [more ▼]

In both elasticity and poroelasticity, the nucleus of strain is usually used to refer to a singular solution such as the point force, the force dipole, the centers of rotation and dilation, etc. These fundamentals solutions constitute the building blocks for various problems of practical importance and are, therefore, relatively well understood. However, a comparison of the original elastic solution for the center of dilation with the classic Lamé solution reveals an unexpected dependence of the center of dilation solution on the Poisson’s ratio. This inconsistency is investigated by means of two alternative representations of the singularity and leads to the identification of a compressed zone inside the singularity. The poroelastic equivalent to this nucleus of strain is shown to be the superposition of the elastic one with drained material parameters and an instantaneous point fluid source associated with a finite volume of fluid that is expelled from the compressed region inside the singularity and is injected in the porous medium. [less ▲]

Detailed reference viewed: 42 (13 ULiège)
Full Text
See detailEnhancement and parametric analysis of a model of a drilling assembly equipped with a rotary steerable system
Huynen, Alexandre ULiege

Master's dissertation (2010)

Demand in products derived from crude oil and the decrease of the gas and petroleum reserves have been boosting the petroleum industry to always beat back the limit between reserves and resources ... [more ▼]

Demand in products derived from crude oil and the decrease of the gas and petroleum reserves have been boosting the petroleum industry to always beat back the limit between reserves and resources, explaining why the interest for directional drilling has been growing up during the last several decades. Nowadays, rotary steerable systems are so efficient that they are becoming the benchmark for the industry. More than one million feet of well-bore are drilled every year using this technology. The drilling industry handles dimensions and times that cover several order of magnitude. The time scale ranges from seconds for the bit revolution to days for the drilling of a well, while the length scale ranges from hundredth of millimetres for the penetration parameters of a bit in a rock formation to kilometres for the length of a drillstring. This makes the drilling industry such an unfamiliar field which confronts engineers to unconventional challenges. This complexity may explain why, despite the substantial resources of the oil industry, direc- tional drilling processes are still misapprehended. Indeed, the industry continues to rely on trial and error to control the direction of an oil well. Nevertheless, relatively recent theories try to com- prehend the directional behaviour of a drilling assembly in order to predict, with relative success, the geometry of the borehole drilled. Mathematical models of the near-bit region of the drillstring already exist. However the literature covers especially drilling assembly equipped with a push- the-bit system. The main purpose of the second part of this work is to develop a mathematical model of a drilling assembly equipped with a point-the-bit system. This one is an enhancement of the Mathematical Model of the Near-Bit Region of an Advancing Drilling System developed by Detournay (2007). The model is composed of three interacting components: (i) the equations governing the geometrical evolution of the borehole, (ii) the laws that link the kinematical bit-rock penetration variables to the forces on the bit, and (iii) the relationships between the forces on the bit and the loads on the drillstring. The third part of this work presents the results of a parametric analysis of this mathematical model. The parametric analysis, led in the framework of planar borehole trajectories and stationary solutions, focus on the the borehole curvature and distinguishes the two configurations of the BHA: with and without rotary steerable system. Finally, a brief case study of a commercialised point-the-bit system is presented in the fourth part. The goal of this last section is to validate the mathematical model developed and highlight the limitations of this one. Some commonly accepted thoughts are also approached. [less ▲]

Detailed reference viewed: 79 (14 ULiège)