BesøksadresseNiels Henrik Abels hus (kart) Moltke Moes vei 35
Experimental investigation of linear stability mechanisms in stratified gas-liquid pipe flow
The evolution of interfacial waves on a stratified air water pipe flow is investigated experimentally. An oscillating plate introduced controlled perturbations at the inlet of the pipe. High speed cameras captured the evolution of these perturbations along the pipe by means of a phase-locked shadowgraphy technique. Thereby, it was possible to measure the temporal and the spatial evolution of the disturbances introduced in the flow. Particle image velocimetry was performed further downstream in order to evaluate changes in the base flow.
A relatively large data bank has been gathered with varying air and water flow rates as well as varying amplitudes and frequencies of the inlet perturbations. Some preliminary results contain a qualitative assessment of linear vs. non-linear regimes and momentum transfer into the water layer.
Zebrafish embryos: a useful tool for the study of nanoparticle behavior in real time in a vertebrate
Potential flow with free boundaries using the level set method. A review of some electro-hydrodynamic applications
PIV investigation of the flow structures developing in a parallel valves Diesel engine cylinder during the intake stroke.
Hydrodynamics and adhesion of soft interfaces
Mathematical Institute, University of Oxford
The Lattice Boltzmann Method and its application in modeling of physiological flows
Victor Haughton, Professor of Radiology at the University of Wisconsin
and Adjunct Research Scientist at Simula Research Laboratory
Three-dimensional instability of solitary water waves
Flow induced vibration (FIV) is a recent discipline in Flow Assurance which focuses on the piping and equipment vibrations caused by the internal flow of gas, oil and/or water in subsea production systems (SPS). Those vibrations may cause fatigue failure at weak spots in the piping such as welds and tees. Due to recent incidents and ever-increasing production rates and velocities, FIV is now considered as a major limiting factor in the design and operation of SPS. Based on real cases and ongoing projects, this presentation provides an introduction to the following aspects: fluid-structure interaction mechanism, fatigue mechanism, design requirements for SPS, analysis tools and vibration monitoring techniques.
Muligheter for samarbeid med DHI innen forskning, PhD og master-prosjekter.
Wave measurements are traditionally performed in one of two locations: either at the sea surface or from below the surface. Both have their challenges and benefits.
Nortek is among those offering a subsurface wave measurement solution. This is done with acoustic Doppler current profilers. The presentation will discuss how subsurface wave measurements have evolved in the last decade. An emphasis will be placed on the challenges that exist and what has been done to expand the limits and improve the performance.
Thierry Coupez is professor at Mines - Paristech
We will take a look at ideas for Mechanics Academy (MA), a freely-accessible web-based resource for anyone aiming to learn mechanics.
Harish Narayanan is at SIMULA.
Patrick J. Lynett is from the University of Southern California.
Randall J. LeVeque, Applied Mathematics Department University of Washington
Lateral-torsional buckling of elastic structures under combined loading will be considered in this seminar. This problem has been first reported in the habilitation thesis of Prandtl dated 1899. Closed-form solutions based on Bessel's functions are available for some speciﬁc types of loading. However, numerical methods such as the Finite Element Methods (FEM) or other approximate methods are needed in the general case. More generally, approximation of the buckling curve (limit of the stable domain in the loading parameters space) is investigated from the stationary property of the Rayleigh’s quotient. The approximation is then compared to a numerical approach, namely the iterative method of Vianello and Stodola. Closed-form solutions give upper bounds with relative error less than 0.2%. It is shown that the stable domain of the loading parameter space is convex. The Papkovitch–Schaefer theorem proven in 1934 is extended for this specific problem, despite the nonlinear dependence of the equilibrium equations on the loading parameters for the one-dimensional system. The boundary of the stable domain is clearly nonlinear, but this nonlinearity is weak. It is shown that Dunkerley’s lower bound is relevant for the two structural cases considered, and the maximum relative error induced by such a lower bound is lower than 2%. Prandtl's linear approximation is then validated approximately one century later the pioneer works of Prandtl devoted to elastic instability.
Noël Challamel is Professor at the Department of Civil Engineering (LIMATB), University of South-Brittany, Lorient, France, and Marie Curie fellow at the Department of Mathematics, University of Oslo, Oslo, Norway.
The fundamental mechanisms of plasticity in inorganic glasses are distinctly different from those in crystalline metals. Whereas dislocations and their mobility require plasticity in metals, mechanisms responsible for permanent deformation in glasses are to be looked at the atomistic scale. The lecture will deal with this and will involve topics such as for instance constitutive material laws, plasticity theory, dislocation theory, computational mechanics, multiscale analysis, finite element methods, crack modelling, etc.
Vincent Keryvin is professor at Department of Materials Engineering (LIMATB), University of South-Brittany, Lorient, France.
This seminar will be focused on some elementary structural systems such as the cantilever beam. The cantilever is an old problem in structural mechanics already investigated by Galileo (1638) from equilibrium and strength arguments. This structural paradigm will be reconsidered here using buckling, post-buckling and inelastic theory. We will first present some fundamental buckling results for axially loaded columns. This model covers the case of a tree under its own weight or gives an answer to Babel mythology, at least from the stability theory point of view. This in-plane buckling problem in presence of distributed and concentrated axial forces has been recently exactly solved using hypergeometric functions. The post-buckling behavior associated with a nonlinear boundaryvalue problem will be also discussed using some asymptotic and numerical methods. The out-of-plane buckling problem of this cantilever beam will be further investigated. The lateral-torsiona l buckling problem of Prandtl (1899) dealing with the stability boundary of a beam loaded by its own weight and a concentrated force will be also solved. The convexity theorem of Papkovitch and Schaefer (1934) will be shown for these structural problems. The seminar will be concluded by the inelastic analysis of the beam in bending. We will show the need to develop a nonlocal plasticity law to describe the post-failure behavior of a beam in presence of softening. Wood’s paradox (1968) is overcome by using a nonlocal plasticity model. The Galileo problem is then revisited in the light of nonlocal mechanics. Applications of such theoretical studies can be found in the field of civil engineering at the macro scale (reinforced concrete design, timber beams, steel or composite beams…), but also at micro- or nano-scales including for instance nanostructures.
Challamel is Professor of Civil Engineering, University of South Brittany, Lorient, France, and Marie Curie Fellow in solid mechanics (faststoffmekanikk) at UiO (2011/2012).
Volume tracking is a popular method for the computation of two phase flow problems. In this talk we present a reformulation of volume tracking in two dimensions in terms of an explicit tracking of the interface between the two immiscible phases. This allows for a higher order accurate representation of the interface with respect to the spatial discretization while conserving the mass up to roundoff precision.
Joris Verschaeve is postdoc at the Mechanics Division, Department of Mathematics, University of Oslo.