Dimensionless analysis of transient air-water pipe flow

Numerical and experimental investigation of optimum surge tank forms in hydroelectric power plants

This study investigates the scaling criteria used to evaluate immiscible water and chemical floods, and miscible solvent injection and VAPEX processes by deriving dimensionless groups. We present findings from various flooding experiments and evaluate the interplay between viscous and capillary forces as functions of oil viscosity, injection velocity, and porous media characteristics. Updated dimensionless times, capillary numbers, and diffusion numbers were derived from the results of different core floods, which accurately predict recovery performance for different solvent and chemical types, injection rates, and rock properties. The capillary number (Nca) and dimensionless time (tD) are the most commonly used dimensionless numbers to characterize oil recovery performance in porous media. Nca balances forces at a given moment, and tD captures the displacement process over time. However, none of these individual numbers accurately correlate with the recovery factor. To address this, we incorporated viscosity ratios, oil density, reservoir thickness, porosity, and permeability, and adjusted the exponent for each term in new dimensionless numbers. We propose combined dimensionless scales to predict oil production in immiscible and miscible floods. The effect of each dimensionless group in our proposed numbers on oil recovery was examined through sensitivity analysis. The proposed updated dimensionless numbers successfully predicted oil recovery for water flooding, chemical flooding, and solvent injection in heavy oil systems. It was found that while traditional dimensionless numbers failed to accurately correlate with the recovery factor, our modified dimensionless numbers improved oil recovery prediction across varying viscosity ratios, solvent types, injection velocities, and core porosities and permeabilities. Incorporating oil density and reservoir height into Nenniger's dissolution term enabled the development of a new capillary number, Nca*, which improved the prediction of oil recovery during solvent injection processes. Our results showed increased recovery efficiency with higher Nca* values, as viscous forces overcame capillary forces. Dimensionless parameters provide accurate scaling from laboratory to field conditions. While extensive dimensionless analysis has been conducted on waterflooding, little work has focused on developing scaling laws for solvent flooding in heavy oil reservoirs. Our study demonstrated that the incorporation of viscosity ratio and dissolution term improved the accuracy of the existing dimensionless numbers in predicting oil production during immiscible and miscible flooding.

Modeling powder properties remains a complex and difficult area of study because particulate materials can behave differently under variable conditions based on their bulk and surface-level properties. The research presented in this manuscript was designed to support the fundamental understanding of powder systems by joining experimental and theoretical calculations of dimensionless numbers groups for design purposes. In order to do so, this work focused on two critical variables to better understand fluidization design: physical and chemical surface properties. To better resolve the influence of surface properties, surface-treated powders were used. Five different powder samples of varying particle size distribution were characterized using physical property measurements, including pressure drop profiles to obtain the minimum fluidization velocity, density measurements, and particle sizing. Using theoretical equations, the minimum fluidization velocity was also calculated to compare with those obtained experimentally and determine typical dimensionless number groups used in bulk handling system design. The results showed that the theoretically determined values were lower than those calculated using the experimentally umf. In the case of the Reynolds number, the experimental values were 3–20% higher than the theoretical values, which is an important distinction for designing conveying systems and pipeline flow. Similar results were observed for the theoretical and experimental Froude numbers, indicating an important dependence on the cohesive properties of the particle interactions. Additional dimensionless number groups were considered, including the granular bond number and flow factors. To investigate the influence of surface forces, Hamaker constants were utilized for alumina and polydimethylsiloxane in the calculation of the granular bond number. A lower granular bond was observed with a decrease in the Hamaker constant for PDMS, suggesting that the surface forces would be lower for our surface-treated powders.

The laser-based resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS) technique has been applied to the exhaust gas stream of a diesel generator to measure, in real time, concentration levels of aromatic air toxics. Volatile organic compounds, as well as several polycyclic aromatic hydrocarbons were detected in the concentration range of 10-200 ppb in the steady-state diesel generator exhaust. The results were verified and compared with conventional extractive sampling and analytical techniques using gas chromatography/mass spectrometry (GC/MS). The high isomer selectivity of the REMPI-TOFMS instrument provided data for individual xylene isomers that are otherwise (partially) coeluting in standard GC/MS analyses. Good agreement was observed between results for volatile and semivolatile organic compounds obtained with REMPI-TOFMS and conventional extractive sampling. Transient events, such as cold start-ups of the diesel generator, resulted in sharp (less than 15 s) peak emissions that were, for benzene, up to a factor of 90 higher than the predominately constant concentrations observed during steady-state operation; warm restarts resulted in lower peak concentrations by a factor of 2.5. These fast transient emissions are only detectable using a real-time approach (1-s resolution) as demonstrated here using REMPI-TOFMS.

Statistical analysis about major accidents indicate that pool fires are among the most frequently encountered major accidents in the Chemical Industry, cause the highest material and economical losses. The CFD simulation has become an important research tool in this type of fires. Also hydrocarbons are first materials to be ignited the first, in this paper, the phenomenon denominated as hydrocarbon pool fire is studied. The hydrodynamics behavior considering the turbulent flow in transient regime were coupled with mass and heat transfer transport including a generation of mas and energy due to a combustion reaction, where the chemical kinetics considering the heptane as a surrogate compound for gasoline. The results are validated comparing them with previously published experimental data, and show the presence of gradients of concentration, temperature as well as velocity. In this type of scenarios, there are numerous dimensionless numbers which can be used to describe the phenomena. These dimensionless groups provide the advantage of being able to compare behaviors at different scales, where space and time variations are generally present. As a result these dimensionless groups can be used in scaling analysis procedures.

A dynamic model that describes the mass transport and attenuation of odor-causing air emissions (i.e., hydrogen sulfide and other reduced sulfur compounds) in a biofiltration unit was developed and incorporated into a software package called Biofilter. Mechanisms included advective flow, mass transfer from the bulk phase to the biofilm, biofilm internal diffusion, and biological reaction in the biofilm. A dimensionless analysis revealed that the mass transport and attenuation of target compounds can be characterized by several dimensionless groups. Model equations were converted to ordinary differential equations using orthogonal collocation and the resulting ordinary differential equations were solved using the DGEAR algorithm. Numerical solutions were verified by comparing model simulations to analytical solutions. The model simulations showed that the existence of a water layer surrounding the biofilm in a biofiltration unit lowers the removal efficiency of hydrogen sulfide. A sensitivity analysis of model parameters (including the film transfer coefficient, biofilm diffusivity, biofilm thickness, maximum specific biomass growth rate, yield coefficient, half-saturation coefficient, and initial active biomass concentration) using data from two biofilters located at the Cedar Rapids (Iowa) Water Pollution Control Facilities, showed that biofilm internal diffusion and biofilm kinetics have a significant effect on hydrogen sulfide removal, while external mass transfer has little effect.

The objective of this project is to develop, and integrate, high-performance simulation tools capable of predicting plasma-facing component (PFC) operating lifetime and the impact of the evolving surface morphology of tungsten-based PFCs on plasma contamination, including the dynamic recycling of fuel species and tritium retention, in future magnetic fusion devices. Establishing a fundamental physical understanding and developing predictive capabilities of plasma-surface interactions (PSI) requires simultaneously addressing complex and diverse physics occurring over a wide range of length (Angstroms to meters) and time (femtoseconds to years) scales, as well as integrating extensive physical processes across the plasma–surface interface. This requires development of not only detailed physics models and computational strategies at each scale, but also algorithms and methods to couple them effectively in a way that can be robustly validated. Deploying these tools requires the continued development and coupling of leadership-scale computational codes to describe the boundary plasma and the evolving PFC surface, as well as a host of simulations that bridge disparate scales to address complex physical and computational issues at the plasma–surface interface in multi-component materials systems for magnetic fusion energy development beyond ITER. This project will enable discovery of the key physical phenomena controlling critical PFC performance issues, and the quantitative prediction of their impact on PFC performance during both steady-state and transient plasma conditions. Such phenomena include: (i) surface evolution in regions of either net erosion or net deposition; (ii) the impact of the evolving surface composition and roughness on the retention and recycling of hydrogenic fuel isotopes; (iii) the impact of dilute impurities on surface morphological evolution and plasma contamination; and (iv) the effects of high-energy neutron damage on surface properties that could influence helium/hydrogenic species retention and recycling. The outcome of this project will be a suite of coupled plasma and materials modeling tools, and a leadership class PFC simulator to predict PFC evolution and feedback to the boundary plasma both during steady-state plasma operation and transient events. Success in the proposed research tasks will enable the prediction of both plasma fueling and the sources of impurity contamination that impact core plasma performance, and will lay the foundation for understanding, designing, and developing the materials required to meet the performance objectives of future fusion reactors. Advanced capabilities for predictive modeling of plasma-facing component (PFC) surface morphological evolution and near-surface structural evolution are required for evaluation of tungsten (W) as a PFC in ITER’s divertor and improvement of its performance. Atomistically-informed, hierarchically developed and properly parameterized continuum-scale models that can efficiently access the spatiotemporal scales of PFC tungsten dynamical response enable such quantitative predictions of PFC structural and morphological evolution. Toward this end, the research conducted at UMass Amherst focused on the development of a materials property and defect interaction database that is required for constitutive modeling of the mechanical response of PFC tungsten and heat and mass transport in the near-surface region and on the surface of the PFC material, as well as the development and continuous upgrading of surface morphological evolution models which will improve significantly the predictive accuracy of our PFC tungsten evolution simulators. This effort is within the scale-bridging mission of the PSI-SciDAC center. Specific research tasks executed at UMass Amherst included: (1) Development of comprehensive databases for: (a) PFC tungsten mechanical, thermal, and transport properties (including elastic properties, mechanical strength, thermal conductivity, coefficient of thermal expansion, diffusion coefficients, and heats of transport); and (b) energetics of plasma-related defect interactions in the PFC near-surface region; (2) Incorporation of the above databases into constitutive models to determine the level of stress, as well as heat and species fluxes in PFC tungsten under plasma exposure conditions; (3) Developing and continuous upgrading of our hierarchical, atomistically-informed continuum-scale models of PFC surface evolution by incorporating additional physics modules (diffusion mechanisms, bubble dynamics) into the models; and (4) Computational implementation of the above databases, constitutive models, and upgraded surface dynamics in our simulators for predicting surface and near-surface dynamical response of PFC tungsten, from He retention to surface damaged (fuzz) layer growth as a function of fluence, under realistic plasma exposure conditions. The atomistic simulations involved in the database development employed state-of-the-art interatomic interaction potentials with excellent predictive capabilities. Our PSI-SciDAC kinetic Monte Carlo simulators, surface morphological evolution simulators, and the Xolotl PFC simulator are properly upgraded by integrating into their capabilities the above property database, constitutive information, and additional physics modules (from surface diffusion mechanisms to subsurface bubble dynamics).

Introduction. A gravity conduit with a control valve and a pressure regulator in the gravity water-supply pipe is considered under conditions when the hydraulic regime of the water-supply system is not disturbed. In relation to such a system, the problems of converting the energy of local artificial hydraulic resistance into electricity are investigated.Materials and Methods. Literature that highlights the possibility of using microturbines for power generation in water systems was studied. The actual values noted by the continuous pressure recorder (logger) for 12 hours were presented, as well as the water consumption by the turbine at a given unit section (the average for a year), and the pressure differential. It was noted that the use of small hydroelectric power plants in water supply systems significantly reduced the cost of their operation. The indicators of water consumption in the hydroturbine unit during the year, broken down by months, were given. The maximum power at the turbine inlet was calculated. The principles of selecting the type of hydraulic turbine were described. The average efficiency values for different elements of the hydroturbine plant, the average parameters of the power of the small hydro and the corresponding indicators of the average monthly electricity generation were indicated.Results. Equipping the units under study with specially designed turbines can enable to obtain electrical energy through converting artificially created by local resistance and extinguished mechanical energy. It is possible to apply the approaches described in this article when replacing many of the pressure control units of the Yerevan City Network system. The productivity of a small hydro power plant was predicted, as well as the terms of its construction and operation — for 2 years and 30 years, respectively. The construction and maintenance costs were calculated in advance. The expected data on income, expenses, and net profit are given. It is indicated that it will potentially be close to 6 million drams per year. The analysis of the data allowed us to conclude that the internal rate of return will be at the level of 10.4%, and the payback period is 9 years.Discussion and Conclusions. We recommend replacing the regulator with a hydroturbine having the same hydraulic resistance and automatic flow control in the system. The conclusions were confirmed by the energy and economic indicators of the hydroturbine plant located on the section of the Arzakan — Yerevan main water pipeline.

Summary Production shutdowns occur often throughout the life cycle of an oil field. In offshore fields, shutdown situations are accompanied by an intense heat exchange between pipeline and cold water, which exponentially increases oil viscosity. Such an event may lead to serious difficulty to restart the production, or even render it unfeasible, especially for heavy oil fields. Therefore, a preventive procedure is required to remove the ultraviscous oil from pipelines and risers; for example, by pumping diesel or methanol in a flush procedure. Designing an efficient cleanup procedure is therefore essential in terms of time, amount of fluid injected, and pumping system requirements. However, the amount of research published in this area is limited. In this paper, we propose a comprehensive analysis on how the displacement of a viscous liquid by a less-viscous liquid occurs in a pipeline through footages in different segments, varying the injection velocity. Two mineral oils with different viscosities and tap water were used as working fluids for this study. The experimental setup was built with a horizontal 10-m-long acrylic pipe with 19-mm internal diameter. Two high-speed cameras were placed both in the inlet and outlet segments. Our results demonstrate how water displaces viscous oil in a pipeline, showing different flow configurations as superficial water velocity increases, depending on the oil viscosity and distance from the inlet. A dimensionless analysis was performed by a combination of the forces that govern the flow and dimensionless groups found in literature. The results show an expected area of optimum values regarding cleaning time according to flow configuration. A unidimensional model using a logistic function was proposed and showed a good agreement with the experimental data. The model itself proven to be an easy tool for industry and academic purposes, supporting even more robust and elaborated models in the future.

Prediction of fiber coating thickness via liquid-phase process

Hydraulic transients that naturally occur in pressurised pipe systems propagate back and forth and carry information about different features of the systems, like bursts or leaks, changes of pipe diameter or material, tee-junctions, local head losses, air pockets, closed valves or pipe branches. The aim of the current paper is the report and analysis of different characteristic pressure traces associated with different pipe system features, whose detection, in the transient pressure signal, allows its identification and approximate location. Transient events analysed herein were artificially generated in different experimental facilities and real life systems by the fast closure of side discharge or in-line valves. Transient pressure data were collected at several locations, with and without bursts, air pockets, changes in pipe diameter/material and branches. Different transient pressure traces were observed and are reported: a burst creates a pressure drop; a dead-end reflects totally incident waves; a diameter decrease induces a pressure peak; an air pocket creates a pressure drop followed by an increase; different pipe materials have different pressure wave shapes and damping. Analyses carried out were aided by two diagnosis support tools: a hydraulic transient simulator and an inverse transient solver. Collected data were compared with the results of numerical simulations obtained by running a transient solver incorporating the accurate description of these phenomena in multi-pipe systems, and an excellent agreement was obtained. An inverse transient solver was applied for the evaluation of the location and size of bursts and air pockets, and it successfully estimated them, providing that an accurate transient solver was used, the evaluation was carried out simultaneously with calibration, and the transient event was created by a fast linear flow change. Conclusions are drawn concerning the importance of considering these phenomena since the design phase until system operation and future expansion. Transient-based techniques are particularly important for the diagnosis, monitoring and control of existing water supply systems, not only to identify abnormal features and estimate their approximate locations, but also for a better understanding of the causes of pipe bursts induced by transient events. This paper was presented at the 8th Annual Water Distribution Systems Analysis Symposium which was held with the generous support of Awwa Research Foundation (AwwaRF).

In 2007, EPAL – Empresa Portuguesa das Águas Livres, S.A. – started to implement a water safety plan (WSP) in its water supply system, from source to tap, following the international methodologies regarding risk management of water quality. Since the implementation of its first version of the WSP, EPAL has been working on the optimization of its methodology regarding identification and evaluation of hazards/hazardous events and risk assessment. The main objective of this optimization is the prioritization of capital investments and implementation of mitigation actions, within the integrated risk-based management of the company. For this purpose, the initial risk assessment matrixes were optimized with the integration of new specific multicriteria tools to evaluate risks associated with different types of operational assets. The final risk assessment took into account the strategic importance of each individual asset within EPAL's supply system. The new risk assessment methodologies have helped decision-making and prioritization of capital investments and also allowed EPAL to better pinpoint the critical issues to address in its supply system.

In recent years Italian water utilities have gone through a restructuring process which focus is on processes optimization. Nowadays, the industry is still seeing many mergers and cost-reduction strategies taking place. Due to low tariffs, the Italian Water Industry has very limited economic resources that need to be spent optimally. In this framework, the importance of optimal asset management is increasing: as the budget is limited, an asset-specific knowledge is required "to choose exactly the right assets, to optimize maintenance activities and to refurbish and replace the selected assets at just the right times in a cost-effective manner". This paper introduces the methodology that was developed to reach this objective by HERA, combining the results of a criticality analysis, performed through a detailed hydraulic model, with a Mean Time To Failure analysis based on pipe bursts-leaks data collected during a six-year period and processed in a GIS software.

Intermittent water supply systems are prone to air entrapments during the pipe filling phase. This work aims to analyse and discuss the numerical results obtained by applying the recently developed AirSWMM model, an extension of SWMM incorporating air phase, to a laboratory network. Experimental data consisting of pressure-head at multiple locations and video recordings of air entrapments are collected in a single loop network with a high point, for different pipe-filling conditions, system layouts and node elevations. Experimental tests have shown that the air entrapment occurred not only at the high point but also throughout the pipe network, creating air pockets with elongated shapes and larger volumes than for single pipes. AirSWWM model with air-entrapment formation, growth and transport is tested in the pipe network, and results are compared with measurements. AirSWWM model can correctly locate large air pockets but underestimates their volume.

Pipeline transportation of petroleum products remains one of the safest and most efficient methods of bulk energy delivery, yet overpressure events continue to pose serious operational and regulatory challenges. Traditional fixed-gain PI controllers, commonly used with centrifugal pump drives, cannot adapt to varying product densities or transient disturbances such as valve closures that generate water hammer. This paper proposes a self-tuning adaptive controller based on Recursive Least Squares (RLS) parameter estimation to improve safety and efficiency in pipeline pump operations. A nonlinear simulation model of a centrifugal pump driven by an induction motor is developed, incorporating pipeline friction losses via the Darcy–Weisbach relation and pressure transients induced by rapid valve closures. The RLS algorithm continuously estimates effective loop dynamics, enabling online adjustment of proportional and integral gains under changing fluid and operating conditions. Simulation results demonstrate that the proposed RLS-based adaptive controller maintains discharge pressure within ±2% of the target setpoint under density variations from 710 to 900 kg/m3 and during severe transient events. Compared to a fixed-gain PI controller, the adaptive strategy reduced pressure overshoot by approximately 31.9% and settling time by 6%. Model validation using SCADA field data yielded an R2 = 0.957, RMSE = 3.95 m3/h, and normalized NRMSE of 12.6% (by range), confirming strong agreement with measured system behavior. The findings indicate that RLS-based self-tuning provides a practical enhancement to existing pipeline control architectures, offering both improved robustness to abnormal transients and greater efficiency during steady-state operation. This work establishes a foundation for higher-level supervisory and game-theoretic coordination strategies to be explored in subsequent studies.