DNV GL

About: DNV GL is a company organization based out in Sandvika, Norway. It is known for research contribution in the topics: Corrosion & Finite element method. The organization has 1929 authors who have published 2387 publications receiving 34644 citations.

Two‐Phase Flow: Structure, Upscaling, and Consequences for Macroscopic Transport Properties

Abstract: In disordered porous media, two-phase flow of immiscible fluids (biphasic flow) is organized in patterns that sometimes exhibit fractal geometries across a range of length scales, depending on the capillary, gravitational, and viscous forces at play. These forces, as well as the boundary conditions, also determine whether the flow leads to the appearance of fingering pathways, i.e., unstable flow, or not. We present a short review of these aspects, focusing on drainage and summarizing when these flows are expected to be stable or not, what fractal dimensions can be expected, and in which range of scales. We based our review on experimental studies performed in two-dimensional Hele–Shaw cells or addressing three-dimensional porous media by use of several imaging techniques. We first present configurations in which solely capillary forces and gravity play a role. Next, we review configurations in which capillarity and viscosity are the main forces at play. Eventually, we examine how the microscopic geometry of the fluid clusters affects the macroscopic transport properties. An example of such an upscaling is illustrated in detail: for air invasion in a monolayer glass-bead cell, the fractal dimension of the flow structures and the associated scale ranges depend on the displacement velocity. This controls the relationship between saturation and the pressure difference between the two phases at the macroscopic scale. We provide in this case expressions for dynamic capillary pressure and residual fluid-phase saturations.

Introduction to the Update of DNV'96, DNV OS F101; Submarine Pipeline Systems

Abstract: In late 1996, DNV issued a revision of the DNV Rules for Submarine Pipeline Systems (DNV'96). This constituted a complete revision of the previous version of the Rules from 1981. The major change in the Rules was the introduction of the limit state format, in form of a calibrated Load and Resistance Factor Design (LRFD) format. Since then, the Rules have become widely used throughout the world. One very important reason for this success was that it allowed a thinner wall, i.e. less material, hence there was a potential cost benefit from using it. This higher utilisation was allowed, given that both a more stringent design approach as well as a more stringent pipe manufacture was achieved. Based upon experience with DNV documents related to offshore installations and feedback from the industry, DNV has initiated a project New Offshore Class in order to improve these DNV documents. This includes a separation of technical requirements, into a neutral DNV Offshore Standard (OS) document, and DNV services into a DNV Offshore Service Description (OSD) document covering verification and certification. As part of this project, the DNV Pipeline Rules have been converted into this system. The conversion also gave the opportunity to do some modifications reflecting the gained experience as well as the received comments from the users of DNV'96. This paper gives an overview of experience gained from DNV'96 and an introduction to the new OS with special focus on the modifications from DNV'96.