## Visiting address

Niels Henrik Abels husMoltke Moes vei 35 (map)

0851 OSLO

Norway

Time and place:
Sep. 30, 2016 11:15 AM–12:00 PM,
B91, NHA bygget

**Enrico Fermi and the birth of modern nonlinear physics**

In the early fifties in Los Alamos E. Fermi in collaboration with J. Pasta and S. Ulam investigated a one dimensional chain of equal masses connected by a weakly nonlinear spring. The key question was related to the understanding of the phenomenon of conduction in solids; in particular they wanted to estimate the time needed to reach a statistical equilibrium state characterized by the equipartition of energy among the Fourier modes. They approached the problem numerically using the MANIAC I computer; however, the system did not thermailize and they observed a recurrence to the initial state (this is known as the FPU-recurrence). This unexpected result has led to the development of the modern nonlinear physics (discovery of solitons and integrability). In this seminar, I will give an historical overview of the subject and present the different approaches that have been proposed in the last 60 years for explaining this paradox. Very recent results on the estimation of the time scale and on the explanation of the mechanism of equipartition will also be discussed.

Time and place:
Sep. 23, 2016 11:15 AM–12:00 PM,
NHA bygget 9 etg B91

**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.

Time and place:
Mar. 11, 2016 11:15 AM–12:00 PM,
B91, NHA bygget

**Zebrafish embryos: a useful tool for the study of nanoparticle behavior in real time in a vertebrate**

Time and place:
Jan. 19, 2016 12:15 PM–1:00 PM,
Undervisninsgrom 1036

Potential flow with free boundaries using the level set method. A review of some electro-hydrodynamic applications

Time and place:
Nov. 10, 2015 12:15 PM–1:00 PM,
NHA bygget 9 etg B91

PIV investigation of the flow structures developing in a parallel valves Diesel engine cylinder during the intake stroke.

Time and place:
Oct. 20, 2015 12:15 PM–1:00 PM,
NHA 935

Hydrodynamics and adhesion of soft interfaces

Time and place:
Oct. 6, 2015 12:15 PM–1:00 PM,
NHA 935

Mathematical Institute, University of Oxford

Time and place:
Oct. 23, 2014 10:15 AM–12:00 PM,
NHA bygget 9 etg B91

The Lattice Boltzmann Method and its application in modeling of physiological flows

Time and place:
Sep. 25, 2014 10:15 AM–11:00 AM,
B91

Victor Haughton, Professor of Radiology at the University of Wisconsin

and Adjunct Research Scientist at Simula Research Laboratory

Time and place:
Aug. 5, 2014 11:00 AM–12:00 PM,
B91 Abel Building

**Three-dimensional instability of solitary water waves**

Time and place:
May 14, 2014 12:15 PM–1:00 PM,
B91

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.

Time and place:
May 7, 2014 12:15 PM–1:00 PM,
B91

Time and place:
Sep. 26, 2013 2:15 PM–3:00 PM,
B91

Muligheter for samarbeid med DHI innen forskning, PhD og master-prosjekter.

Time and place:
Sep. 16, 2013 8:30 AM–Sep. 17, 2013 5:00 PM,
The Norwegian Academy of Science and Letters

The symposium is a follow-up of two highly successful previous symposia, held 14-15 October 2008 in the Norwegian Academy in Oslo and 1-2 November 2010 in RSE in Edinburgh. Topics of this year's symposium include: internal waves, ocean surface waves and tsunamis reflecting the activities in the current research projects of the Norwegian and Scottish groups.

Time and place:
Apr. 18, 2013 12:15 PM–1:00 PM,
B91

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.

Time and place:
Jan. 21, 2013 10:15 AM–11:00 AM,
B81

Dr. Mostafa Safdari Shadloo is from Faculty of Engineering and Natural Sciences,
Sabanci University

Time and place:
Nov. 21, 2012 1:15 PM–2:00 PM,
Room 1036 at CMA

Thierry Coupez is professor at Mines - Paristech

Time and place:
Nov. 9, 2012 12:15 PM–1:00 PM,
B91

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.

Time and place:
Aug. 23, 2012 1:15 PM–2:00 PM,
B62

Patrick J. Lynett is from the University of Southern California.

Time and place:
May 21, 2012 2:15 PM–3:00 PM,
NHA: 801 (Seminarrom B81)

Randall J. LeVeque, Applied Mathematics Department University of Washington

Time and place:
Mar. 7, 2012 3:15 PM–4:00 PM,
9th floor, Seminar room B91, NHA Building

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.

Time and place:
Mar. 1, 2012 1:15 PM–2:00 PM,
9th floor (common area), NHA (Mathematics) Building

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.

Time and place:
Jan. 20, 2012 12:15 PM–1:00 PM,
B91

Time and place:
Jan. 10, 2012 2:15 PM–3:00 PM,
9th floor. NHA building

The gas pipeline from the Ormen Lange Field to the terminal at Aukra faced several challenges. First, the terrain was very rugged as the route goes through the Storegga slide area where unprecedented long free spans were to be expected. Secondly, the area was believed to have complicated and strong ocean currents. An oceanographic campaign was started in 1999 and lasted to 2007. The presentation will give some background for the measurements, describe the programme and show some results.

Time and place:
Nov. 28, 2011 1:15 PM,
B91