A microfluidic device with integrated surface plasmon resonance (SPR) chemical and biological sensors based on arrays of nanoholes in gold films is demonstrated. Widespread use of SPR for surface analysis in laboratories has not translated to microfluidic analytical chip platforms, in part due to challenges associated with scaling down the optics and the surface area required for common reflection mode operation. The resonant enhancement of light transmission through subwavelength apertures in a metallic film suggests the use of nanohole arrays as miniaturized SPR-based sensing elements. The device presented here takes advantage of the unique properties of nanohole arrays: surface-based sensitivity; transmission mode operation; a relatively small footprint; and repeatability. Proof-of-concept measurements performed on-chip indicated a response to small changes in refractive index at the array surfaces. A sensitivity of 333 nm per refractive index unit was demonstrated with the integrated device. The device was also applied to detect spatial microfluidic concentration gradients and to monitor a biochemical affinity process involving the biotin-streptavidin system. Results indicate the efficacy of nanohole arrays as surface plasmon-based sensing elements in a microfluidic platform, adding unique surface-sensitive diagnostic capabilities to the existing suite of microfluidic-based analytical tools.

An analytical solution for dispersion of ionic and neutral solutes in nanoscale channels is presented. Results suggest that in the presence of relatively thick electrical double layers (EDLs) characteristic of nanofluidics, the dispersion of ionic solutes differs from that of neutral solutes on which previous theory is based. Ionic dispersion for circular cross-section channels is quantified as a function of a valance parameter, the relative EDL thickness, and the form of the velocity profile. Two unique mechanisms governing ionic dispersion in both pressure- and electrokinetically driven flows are identified. The results of the analytical solution, employing the linearized form of the Poisson-Boltzmann equation, are supported and extended by the results of an independent computational model employing the nonlinear Poisson-Boltzmann equation. Applicability of the computational results is not limited by the Debye-Hückel approximation. Collectively, these results indicate that dispersion of ionic species in nanoscale channels is markedly charge dependent, and substantially deviates from that of neutral solutes in the same flow.

LedaFlow ® is a new transient multiphase flow simulator which includes 1D multi-fluid models consisting of mass, momentum and energy conservation equations for each field (continuous, bubble and droplet), as well as compositional tracking. In this paper, a new method called Slug Capturing is employed for slug flow, and the results analyzed and compared with the field data of two different fields. Additionally, for some cases, differences between the new simulator and another commercially available transient code results are compared and analyzed.The first case corresponds to the production of a TOTAL-operated field in the UK. Produced fluids from the wells are transported through a 21 km long, 16-inch multiphase flowline from the well platforms to the central receiving facilities. The multiphase line (gas/oil/water) must be operated in a narrow range of pressure and flow rate conditions in order to avoid severe slugging issues. Flow patterns are compared for various water cuts and superficial gas velocities. When severe slugging is observed, slug characteristics (frequency, length) are analyzed and compared to simulator predictions.The second case is from a CONOCOPHILLIPS-operated North Sea asset. The 3-phase, 18-inch ID oil flow line runs 3.7 km from a wellhead platform to a central processing platform. The line drops approximately 6 m over the last 3 km before flowing up a 130 m riser. The pipeline exhibits severe riser slugging which is not adequately modeled by conventional transient models, due to the complex interplay between hydrodynamic and riser slugging, as well as 3-phase effects. Slug frequencies and lengths are analyzed and compared to predictions.

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Large amplitude roll waves are incorporated into a previously developed slug tracking scheme for two phase gas-liquid pipe flow. The applicability of the tracking scheme to large amplitude waves is demonstrated with a simplified model for the waves. The waves are modelled analogous to slugs on a moving grid with corresponding wave velocities and a pressure variation determined using an orifice type relation. Slugs and waves in the tracking scheme are separated by regions of stratified flow, which are modelled on a stationary grid using the two-fluid model. The computational scheme is described, compared to experimental data on roll waves, and some wave dynamics such as waves developing to slugs and slugs decaying to waves are demonstrated.