Characterizing the surface texture of a dense suspension undergoing dynamic jamming

Measurements of the surface velocity and surface texture of a freely propagating shear jamming front in a dense suspension are compared. The velocity fields are captured with particle image velocimetry (PIV), while the surface texture is captured in a separated experiment by observing a direct reflection on the suspension surface with high-speed cameras. A method for quantifying the surface features and their orientation is presented based on the fast Fourier transform of localized windows. The region that exhibits strong surface features corresponds to the the solid-like jammed region identified via the PIV measurements. Moreover, the surface features within the jammed region are predominantly oriented in the same direction as the eigenvectors of the strain tensor. Thus, from images of the free surface, our analysis is able to show that the surface texture contains information on the principle strain directions and the propagation of the jamming front. Graphic Abstract

Propagation of shear stress in strongly interacting metallic Fermi liquids enhances transmission of terahertz radiation

A highlight of Fermi-liquid phenomenology, as explored in neutral $$^3$$ 3 He, is the observation that in the collisionless regime shear stress propagates as if one is dealing with the transverse phonon of a solid. The existence of this “transverse zero sound” requires that the quasiparticle mass enhancement exceeds a critical value. Could such a propagating shear stress also exist in strongly correlated electron systems? Despite some noticeable differences with the neutral case in the Galilean continuum, we arrive at the verdict that transverse zero sound should be generic for mass enhancement higher than 3. We present an experimental setup that should be exquisitely sensitive in this regard: the transmission of terahertz radiation through a thin slab of heavy-fermion material will be strongly enhanced at low temperature and accompanied by giant oscillations, which reflect the interference between light itself and the “material photon” being the actual manifestation of transverse zero sound in the charged Fermi liquid.

Basin effects and limitations of 1D site response analysis from 2D numerical models of the Thorndon basin

Plane strain (2D) finite element models are used to examine factors contributing to basin effects observed for multiple seismic events at sites in the Thorndon basin of Wellington, New Zealand. The models consider linear elastic soil and rock response when subjected to vertically-propagating shear waves. Depth-dependent shear wave velocities are considered in the soil layers, and the effects of random variations of soil velocity within layers are modelled. Various rock shear wave velocity configurations are considered to evaluate their effect on the modelled surficial response. It is shown that these simple 2D models are able to capture basin reverberations and compare more favourably to observations from strong motion recordings than conventional 1D site response models. It is also shown that consideration of a horizontal impedance contrast across the Wellington Fault affects spectral response and amplification at longer periods, suggesting the importance of this feature in future ground motion modelling studies in the Wellington region.

Pipeline Fracture Control Concepts for Norwegian Offshore Carbon Capture and Storage

The Northern Lights onshore terminal will initially receive CO2 transported by ship tankers from industrial source sites located in south-eastern Norway and transport CO2 via a 12 ¾” OD offshore pipeline for injection into the Johansen storage reservoir, located south of the Troll field. The CO2 injection pipeline will be laid from the shore terminal to a subsea wellhead structure from where the liquid CO2 will be injected into the reservoir. Presently, demonstrating arrest of longitudinal propagating shear fracture in CO2 transport pipelines is specifically addressed in two international guidelines, ISO 27913 and DNVGL-RP-F104. The study reported here aims to develop a robust fracture control methodology unique to the Northern Lights pipeline. To this end, the maximum loading in terms of saturation pressure is conservatively estimated from temperature and pressure scenarios from the planned pipeline route and applied in numerical simulations of the running-fracture phenomenon using the SINTEF coupled FE-CFD code. It is shown that, with the given pipe material, diameter, and loading conditions, the proposed wall thickness of 15.9 mm is sufficient to arrest a propagating crack. Furthermore, the Battelle TCM with ISO 27913 or DNVGL-RP-F104 arrest- and load pressure correction is shown to provide a good first estimate in pipe design, although the arrest pressure saturates for low Charpy energy toughness values, indicating limited accuracy in this study.

THE INFLUENCE OF BOUNDARY CONDITIONS ON THE RESPONSE OF UNDERGROUND STRUCTURES SUBJECTED TO EARTHQUAKE

The paper deals with the prediction of the response of a real underground structure subjected to earthquake. A fully dynamic analysis is carried out in the GEO5 FEM program using the Finite Element Method. Limiting our attention to a two-dimensional analysis we focus on the implementation of special boundary conditions along the vertical edges of the computational model. A simple study is carried out first to show that incorrectly applied boundary conditions may significantly influence the actual design of underground structures loaded by vertically propagating shear waves. This study promotes the combination of so called free-field and static boundary conditions as demonstrated on a simple example.