Impact analysis of TOTEM data at the LHC: black disk limit exceeded

We discuss the profile of the impact--parameter dependent elastic scattering amplitude. Extraction of impact-parameter dependence from the dataset with inclusion of the experimental data on elastic scattering at the LHC energies helps to reveal the asymptotics of hadron interactions. Analysis of the data clearly indicates that the impact-parameter elastic scattering amplitude exceed the black disk limit at the LHC energy 7TeV and the inelastic overlap function reaches its maximum value at $b>0$Comment: 5 pages, 5 figure

Chiral color symmetry and possible G′G'-boson effects at the Tevatron and LHC

A gauge model with chiral color symmetry is considered and possible effects of the color $G'$-boson octet predicted by this symmetry are investigated in dependence on two free parameters, the mixing angle $\theta_G$ and $G'$ mass $m_{G'}$. The allowed region in the $m_{G'} - \theta_G$ plane is found from the Tevatron data on the cross section $\sigma_{t\bar{t}}$ and forward-backward asymmetry $A_{\rm FB}^{p \bar p}$ of the $t\bar{t}$ production. The mass limits for the $G'$-boson are shown to be stronger than those for the axigluon. A possible effect of the $G'$-boson on the $t\bar{t}$ production at the LHC is discussed and the mass limits providing for the $G'$-boson evidence at the LHC are estimated in dependence on $\theta_G$.Comment: 11 pages, 2 figures, accepted for publication in Modern Physics Letters

Modelling Dry Ice Formation Following Rapid Decompression of CO₂ Pipelines

A fundamentally important issue regarding the safety assessment of CO2 pipelines is the possibility of solid or ‘dry ice’ discharge during an accidental release. This is particularly relevant given the near-adaibatic decompression process and the unusually high Joule Thomson coefficient of expansion of CO2. Solids discharge will affect many aspects of the ensuing hazard spanning the erosion of surrounding equipment, modification of the toxic dose duration, atmospheric dispersion and possibly, the pipeline’s propensity to fracture propagation. This paper describes the development of a Cubic Equation of State capable handling solid CO2 as a third phase. Pipeline rupture outflow data are reported based on the coupling of this new equation of state into a rigorous transient outflow model in order to investigate the impact of the pipeline design and operating conditions as well as the presence of the typical impurities on solid CO2 discharge

Hybrid fluid–structure interaction modelling of dynamic brittle fracture in steel pipelines transporting CO2 streams

Pressurised steel pipelines are considered for long-distance transportation of dense-phase CO2 captured from fossil fuel power plants for its subsequent sequestration in a Carbon Capture and Storage (CCS) chain. The present study develops a hybrid fluid–structure methodology to model the dynamic brittle fracture of buried pressurised CO2 pipeline. The proposed model couples the fluid dynamics and the fracture mechanics of the deforming pipeline exposed to internal and back-fill pressures. To simulate the state of the flow in the rupturing pipeline a compressible one-dimensional Computational Fluid Dynamics (CFD) model is applied, where the fluid properties are evaluated using rigorous thermodynamic model. In terms of the fracture model, an eXtended Finite Element Method (XFEM)-based cohesive segment technique is used to model the dynamic brittle fracture behaviour of pipeline steel. Using the proposed model, a study is performed to evaluate the rate of brittle fracture propagation in a real-scale 48 in. diameter API X70 steel pipeline. The model was verified by comparing the obtained numerical results against available semi-empirical approaches from the literature. The simulated results are found to be in good correlation with the simulations using a simple semi-empirical model accounting for the fracture toughness, indicating the capability of the proposed approach to predict running brittle fracture in a CO2 pipeline

Assessment of brittle fractures in CO2 transportation pipelines: A hybrid fluid-structure interaction model

In order to transport dense-phase CO2 captured from power and industrial emission sources in the Carbon Capture and Storage (CCS) chain, pressurised steel pipelines are considered the most practical tool. However, concerns have been raised that low temperatures induced by the expansion of dense-phase CO2, for example following an accidental puncture or during emergency depressurization, may result in a propagating brittle fracture in the pipeline steels. The present study describes the development of a hybrid fluid-structure model for simulating dynamic brittle fracture in buried pressurised CO2 pipelines. To simulate the state of the flow in the rupturing pipeline, a compressible one-dimensional Computational Fluid Dynamics (CFD) model is applied, where the pertinent fluid properties are determined using a thermodynamic model. In terms of the fracture model, an extended Finite Element Method (XFEM) is used to model the dynamic brittle fracture behaviour of the pipeline steel. Using the coupled fluid-structure model, a study is performed to evaluate the risk of brittle fracture propagation in a (real-scale) 1.22m diameter API X70 steel pipeline, containing CO2 at 0°C and 11MPa. The simulated results are found to be in good agreement with the predictions obtained using a semi-empirical model accounting for the pipeline fracture toughness. From the results obtained it is observed that a propagating fracture is limited to a short distance. As such, for the conditions tested, there is no risk of brittle fracture propagation for API X70 pipeline steel transporting dense-phase CO2

A fully coupled fluid-structure interaction simulation of three-dimensional dynamic ductile fracture in a steel pipeline

Long running fractures in high-pressure pipelines transporting hazardous fluid are catastrophic events resulting in pipeline damage and posing safety and environmental risks. Therefore, the ductile fracture propagation control is an essential element of the pipeline design. In this study, a coupled fluid-structure interaction modelling is used to simulate the dynamic ductile fractures in steel pipelines. The proposed model couples a fluid dynamics model describing the pipeline decompression and the fracture mechanics of the deforming pipeline exposed to internal and back-fill pressures. To simulate the state of the flow in a rupturing pipeline, a compressible one-dimensional computational fluid dynamics model is applied, where the fluid properties are evaluated using a rigorous thermodynamic model. The ductile failure of the steel pipeline is described as an extension of the modified Bai-Wierzbicki model implemented in a finite element code. The proposed methodology has successfully been applied to simulate a full-scale pipeline burst test performed by British Gas Company, which involved rupture of a buried X70 steel pipeline, initially filled with rich natural gas at 11.6 MPa and −5 °C