Fluid Analysis Techniques Research Articles

Mechanistic Investigation of LSW/Surfactant/Alkali Synergism for Enhanced Oil Recovery: Fluid-Fluid Interactions.

The combination of chemical enhanced oil recovery (CEOR) and low salinity water (LSW) flooding is one of the most attractive enhanced oil recovery (EOR) methods. While several studies on CEOR have been performed to date, there still exists a lack of mechanistic understanding on the synergism between surfactant, alkali and LSW. This synergism, in terms of fluid–fluid interactions, is experimentally investigated in this study, and mechanistic understanding is gained through fluid analysis techniques. Two surfactants, one cationic and one anionic, namely an alkyltrimethylammonium bromide (C19TAB) and sodium dodecylbenzenesulfonate (SDBS), were tested, together with NaOH used as the alkali, diluted formation brine used as the LSW, and the crude oil was collected from an Iranian carbonate oil reservoir. Fluids were analyzed using pendant drop method for interfacial tension (IFT) measurement, and Fourier transform infrared spectroscopy for determination of aqueous and oleic phase chemical interaction. The optimum concentration of LSW for IFT reduction was investigated to be 1000 ppm. Additionally, both surfactants reduced IFT significantly, from 28.86 mN/m to well below 0.80 mN/m, but in the presence of optimal alkali concentration the IFT dropped further to below 0.30 mN/m. IFT reduction by alkali was linked to the production of three different types of in situ anionic surfactants, while in the case of anionic and cationic surfactants, saponification reactions and the formation of the C19TAOH alcohol, respectively, were linked to IFT reduction. The critical micelle concentration and optimal alkali concentration when using cationic C19TAB were significantly lower than with the anionic surfactant; respectively: 335 vs 5000 ppm, and 500 vs 5000 ppm. However, it was found that SDBS was more compatible with NaOH than C19TAB, due to occurrence of alkali deposition with the latter beyond the optimal point.

Enabling Fluid Analysis for Queueing Petri Nets via Model Transformation

Due to the growing size of modern IT systems, their performance analysis becomes an even more challenging task. Existing simulators are unable to analyze the behavior of large systems in a reasonable time, whereas analytical methods suffer from the state space explosion problem. Fluid analysis techniques can be used to approximate the solution of high-order Markov chain models enabling time efficient analysis of large performance models. In this paper, we describe a model-to-model transformation from queueing Petri nets (QPN) into layered queueing networks (LQN). Obtained LQN models can benefit from three existing solvers: LINE, LQNS, LQSIM. LINE internally utilize fluid limits approximation to speed up the solving process for large models. We present the incentives for developing the automated model-to-model transformation and present a systematic approach that we followed in its design. We demonstrate the transformations using representative examples. Finally, we evaluate and compare the performance predictions of existing analytical, simulation and fluid analysis solvers. We analyze solvers' limitations, solving time, and memory consumption.

Time-inhomogeneous Population Models of a Cycle-Stealing Distributed System

Organisations such as research institutions and universities often increase utilisation of their office workstations by deploying a high-throughput cycle-stealing distributed system. Such systems allow users to submit a large number of computing tasks into a central pool. The system observes activity of workstations and continually assigns tasks to idle machines. When a user becomes active on the machine, the scheduler interrupts the task execution. This approach can significantly increase utilisation of the resources. However, it can also lead to wastage of computing cycles if tasks get interrupted too often.In this paper, we develop a detailed Population Continuous Time Markov Chain (PCTMC) model of the whole system that accurately captures the contention between the interactive users and high-throughput tasks. The PCTMC framework is well suited to the inherently time-inhomogeneous nature of the user behaviour and allows to capture a large number of performance and energy consumption metrics. We fit the PCTMC model to real data and propose a methodology to forecast cluster availability in the near future. We show how to use historically collected and live data to parametrise the PCTMC model and use efficient fluid analysis techniques to predict the desired metrics. Additionally, the fast analysis enables exploration of various what-if scenarios. We demonstrate a working implementation of the method using the existing GPA tool for analysis of PCTMC models. We argue that this methodology could allow the system maintainers to optimise the energy and performance parameters of the system. Moreover, it would benefit the users who could use the model forecasts to better distribute and plan their large scale computations.

Two-dimensional numerical simulation of the red blood cell floating in a plasma-alcohol solution through stenosis in a microvessel

A two-dimensional computational model of a single red blood cell (RBC) floating in a plasma-alcohol solution through a microchannel with stenosis was created using the Arbitrary Lagrangian-Eulerian (ALE) method with moving mesh for a fluid structure interaction problem. Cell deformability and stability were studied in a plasma-alcohol solution at different fluid flow conditions during movement through the channel with stenosis. Different results were obtained for different input parameters. Motion through 45% and 70% stenoses with the high and law velocities of the RBC and different viscosities was analyzed and successfully simulated. Results show that changes in RBC deformability were due to the effects of alcohol. Changes in behavior during motion were also observed. At low shear rate and high surrounding fluid viscosity the RBC showed a tendency to rotate during movement. The proposed model with its coupling of structural and fluid analysis techniques could be useful to understand the effect of alcohol on the RBC passing through stenosis.

Differential pulsed amperometry coupled to microchip capillary electrophoresis

In this work, we describe a novel electrochemical detection method, differential pulsed amperometry (DPA) on microchip capillary electrophoresis (MCE). In a pulse period, a sequential two-step sampling is executed at two different potentials (E1 and E2). Differential current signal of the duplex sampling events is recorded that functions as time domain. The performance of this detection scheme was evaluated by separating and detecting three model analytes including tyramine (Tym), tryptophan (Trp), and p-aminobenzoic acid (PABA). Multiple parameters that would affect electrochemical response and peak shape, such as sampling potential, sampling time, and electrode cleaning time, were investigated. This pulse technique exhibits better sensitivity over constant potential amperometry (CPA), nearly equal to triple pulsed amperometry (TPA). More importantly, DPA can generate more stable baseline than TPA, primarily due to the background subtraction through the two-step sampling, which is beneficial to further improve analytical sensitivity. In the optimal condition, the limits of detection for Tym, Trp and PABA, were down to 0.27μM, 0.32μM and 1.1μM, respectively. DPA detection opens up a new avenue for microchip electrochemistry, and can be virtually extended to other fluid analysis techniques.

Fluid analysis of energy consumption using rewards in massively parallel Markov models (abstracts only)

Capturing energy consumption directly from a stochastic behavioural model is a computationally expensive process. Using a so-called fluid analysis technique we are able to access accumulated reward measures in much larger scale stochastic systems than has been previously possible.These accumulated rewards are ideal for deriving energy and power consumption from stochastic process models. In previous work, it has been shown how to derive a set of ordinary differential equations (ODEs) whose solutions approximate the moments of component counts in a continuous-time Markov chain(CTMC) described in a stochastic process algebra. In this paper, we show how to extend the method to provide rapid access to moments of accumulated rewards in CTMCs. In addition to measuring the amount of energy used by a system, we are also interested in the time taken to reach a particular level of energy consumption. In reward terms, this is a so-called completion time. In this paper, we are able to use higher moments of rewards to give us access to completion time distributions. We demonstrate the technique on a model of energy consumption in a client-server system with server failure and hibernation. Moreover, we are able to use these new and rapid techniques to capture the trade-off between energy consumption and service level agreement (SLA) compliance. We use a standard optimisation approach to find the precise configuration of the system which minimises the energy consumption while satisfying an operational response-time quantile.

Fluid computation of the performance

Recent fluid analysis techniques allow fast and effcient calculation of complex reward metrics and passage time probabilities in systems with very large state space. We demonstrate how to incorporate these to look at the trade-off between service level agreement (SLA) satisfaction and complex reward optimisation. We show how the uid analysis naturally leads to a constrained global optimisation problem with embedded differential equations. We illustrate this problem on an abstract model of a virtualised execution environment that accurately captures resource allocations.

Uniformity Characteristics of Bi2212 Tubes Depending on Cooling Conditions

For the possible application of resistive superconducting fault current limiters (SCFCL), Bi-2212 tube was fabricated by centrifugally forming process (CFP) in terms of different mold designs and cooling rates. Typical tube size was 30 mm in diameter with 3 mm thickness and 100 mm in length. In order to check tube uniformity characteristics, heat and fluid analysis technique of EFDLab was adopted. When the tube was cooled down from 900degC for 100 sec, we found that there was quite different temperature variation along the tube. Based on the results of simulation and experimental data, it was confirmed that the mold designed for the effective heat circulation has more uniform temperature distribution and fast cooling rate in tube, which associated with better texture formation and thereby shows greater electric properties.

401 構造格子SuperCartesian法による複雑形状に対する熱流体解析技法(OS04.流体の数値計算手法と数値シミュレーション(1))

401 構造格子SuperCartesian法による複雑形状に対する熱流体解析技法(OS04.流体の数値計算手法と数値シミュレーション(1))

Applicability of time-average fluid holography for analysis of propagating waves

Numerical procedures for construction of digital patterns of fringes mimicking fluid holograms are developed. Because conventional finite-element fluid analysis techniques are based on the approximation of nodal displacements, conjugate smoothing of the values of volumetric strain is performed in order to obtain realistic holographic images. Two-dimensional fluid oscillations are analyzed using the developed techniques. It is shown that though time-average fluid holography is a powerful optical experimental method for analysis of short-term transient processes and harmonic vibrations, it has rather limited applicability to studying propagating waves.

直噴ディーゼル用サックレスノズルの噴霧ばらつきのメカニズム解析(エンジンの新しい計測技術とモデリング(1),エンジンの新しい計測技術とモデリング)

This paper proposes a hypothesis concerning the mechanism causing asymmetrical sprays from sac-less nozzles used for direct-injection diesel engines. The mechanism was deduced by using 3-dimensional numerical simulation techniques. It has been thought by many researchers that the eccentricity of the needle under a low lift condition causes the flow inside the nozzle to vary, resulting in an asymmetrical spray. However, the reason why such eccentricity occurs has yet to be clarified. In this study, the cause of needle eccentricity was investigated by using 3-dimensional fluid analysis techniques to calculate the force acting on the needle and a probable mechanism of asymmetrical sprays is proposed on the basis of the results.

216 カットセル直交格子に基づいた流体解析汎用ソフトウェア V-FLOW の開発

We have proposed a voxel Cartesian grid method combined with cut cells for simulating unsteady, viscous, and incompressible flows with arbitrary boundaries. In this study, the low load and robust fluid analysis software V-FLOW developed using the proposed approach is introduced. By integrating completely the V-CAD data system, which is expected as the next generation CAD, V-FLOW shows the practical usefulness of the fluid analysis technique based on the Cartesian Grid with Cut Cells. Especially, it could mitigate the cost concerning grid generation in practical use.