Buddhika Hewakandamby | The University of Nottingham (original) (raw)

Papers by Buddhika Hewakandamby

In this paper, we outline the framework that we are developing as part of the Multi-scale Explora... more In this paper, we outline the framework that we are developing as part of the Multi-scale Exploration of Multiphase PHysIcs in flowS (MEMPHIS) programme to create the next generation modelling tools for complex multiphase flows. These flows are of central importance to microfluidics, oil-and-gas, nuclear, and biomedical applications, and every processing and manufacturing technology. This framework involves the establishment of a transparent linkage between input and prediction to allow systematic error-source identification, and, optimal, modeldriven experimentation, to maximise prediction accuracy. The framework also involves massivelyparallelisable numerical methods, capable of running efficiently on 105-106 core supercomputers, with optimally-adaptive, three-dimensional resolution, and sophisticated multi-scale physical models. The overall aim of this framework is to provide unprecedented resolution of multi-scale, multiphase phenomena, thereby minimising the reliance on correlations and empiricism.

Volume 3: Fluid Machinery; Erosion, Slurry, Sedimentation; Experimental, Multiscale, and Numerical Methods for Multiphase Flows; Gas-Liquid, Gas-Solid, and Liquid-Solid Flows; Performance of Multiphase Flow Systems; Micro/Nano-Fluidics, 2018

Effect of injector geometry on two phase flows is of profound importance to industry. If the inje... more Effect of injector geometry on two phase flows is of profound importance to industry. If the injection method is found to vary the flow characteristics dramatically, it can be employed to obtain desirable two phase flow regimes/attributes and avoid rather unsought conditions. This could potentially save a lot of costs in the extraction and transportation of oil and gas as well as in many other applications. Moreover, the issue of flow development and dependency on the injection conditions is essential when modelling two phase flows. A lot of experimental data and empirical models may have been developed based on systems that may not be fully developed. Therefore, inaccurate modelling of the physical interactions of the flow gets adopted, and hence large divergence between models and experimental data produced by different researchers often transpires. Most of the published studies on entrance effect were conducted on air-water or steam-water systems because of their relevance to hea...

Bulletin of the American Physical Society, 2015

The interfacial wave structure of the liquid phase in upwards annular gas-liquid flow in a 11.7 m... more The interfacial wave structure of the liquid phase in upwards annular gas-liquid flow in a 11.7 mm pipe was studied using the brightness based laser induced fluorescent technique (BBLIF). Due to the versatility of the BBLIF technique, film thickness measurements were carried out over different axial locations covering a measurement area with very high spatial and temporal resolution. These comprise measurements performed close to the inlet section (between 0 to 10 z/D), where the dynamics of the small wavelets that are created due to the gas-liquid interaction and that subsequently will lead to the formation of the disturbance waves was analysed. Furthermore, using a tracking algorithm to detect disturbance waves, a full characterization in terms of their velocity, distance and time separation (both in absolute and in terms of their distribution), frequency, intermittency and wavelength was carried out based on measurements conducted further downstream (between 28 to 37 z/D). An Omega-K analysis was also conducted to these latter measurements showing a constant increasing ratio between the ripple and disturbance wave velocity. Although these measurements were conducted well below the predicted length for a fully developed annular flow to occur, it was observed that the behaviour of the structures present in the film during these undeveloped stages plays a crucial role on the overall events that occur further downstream.

Bulletin of the American Physical Society, 2016

annular flow, the experimental validation of the basic assumptions on the liquid velocity profile... more annular flow, the experimental validation of the basic assumptions on the liquid velocity profile is vital for developing theoretical models of the flow. However, the study of local velocity of liquid in gas-sheared films has proven to be a challenging task due to the highly curved and disturbed moving interface of the phases, small scale of the area of interrogation, high velocity gradients and irregular character of the flow. This study reports on different optical configurations and interface-tracking methods employed in a horizontal duct in order to obtain high-resolution particle image velocimetry (PIV) data in such types of complex flows. The experimental envelope includes successful measurements in 2D and 3D waves regimes, up to the disturbance wave regime. Preliminary data show the presence of complex structures in the liquid phase, which includes re-circulation areas below the liquid interface due to the gas-shearing action, together with non-uniform transverse movements of the liquid phase close to the wall due to the presence of 3D waves at the interface. With the aid of the moving interface-tracking, PIV, time-resolved particle-tracking velocimetry and vorticity measurements were performed.

Chemical Engineering Research and Design, 2021

Abstract Most of the experimental and theoretical studies on the film thickness of falling liquid... more Abstract Most of the experimental and theoretical studies on the film thickness of falling liquid films are focussed on either small diameter pipes or flat plates. Almost, all these studies provide time series data of the film thickness measured at single positions around the pipe wall or along the pipe section, which might not reflect the real flow structure in both axial and circumferential directions. This paper reports the interfacial structure of freely falling liquid films (liquid Reynolds numbers, ReL = 618–1670) in a vertical large diameter pipe (127 mm) using advanced Multi-Probes Film Sensor (MPFS). Unlike smaller diameter pipes where the waves are characterised as coherent rings, the waves found in this paper with larger diameter pipe were much localised around the pipe circumference and evolved with time in the axial direction. Skewness and Kurtosis numbers showed two distinct linear trends with two different slopes intersecting at ReL = 960. One of the significant contributions of the current paper is that the new experimental reconstructed three-dimensional wave structure data for the falling liquid film in a vertical large pipe diameter will be available in the literature which would be of interest to many modellers who need such data to validate their CFD models.

SPE Production & Operations, 2021

SummaryIntermittent flow is one of the most complex flow regimes in horizontal pipes. Various stu... more SummaryIntermittent flow is one of the most complex flow regimes in horizontal pipes. Various studies have classified this regime as two distinct subregimes: plug and slug flow. This classification has been made based on flow observations. In this work, the behavior of several flow parameters that characterize plug and slug flow are presented. Data from eight published works in the open literature were collected and studied to explain the behavior of both regimes. These data include pressure drop, void fraction, and slug frequency, as well as the lengths of liquid slugs and elongated bubbles for slug and plug regimes.It is observed from the evolution and analysis of these parameters that plug and slug flows have several different distinct features and should be considered as two separate regimes for the empirical modelization of the hydrodynamic parameters. The mixture Froude number, and to a lesser extent the liquid superficial velocity to gas superficial velocity ratio, seem to ha...

IEEE Access, 2020

Three-phase gas-oil-water flow is an important type of flow present in petroleum extraction and p... more Three-phase gas-oil-water flow is an important type of flow present in petroleum extraction and processing. This paper reports a novel threshold-based method to visualize and estimate the crosssectional phase fraction of gas-oil-water mixtures. A 16 × 16 dual-modality wire-mesh sensor (WMS) was employed to simultaneously determine the conductive and capacitive components of the impedance of fluid. Then, both electrical parameters are used to classify readings of WMS into either pure substance (gas, oil or water) or two-phase oil-water mixtures (foam is neglected in this work). Since the wire-mesh sensor interrogates small regions of the flow domain, we assume that the three-phase mixture can be segmented according to the spatial sensor resolution (typically 2-3 mm). Hence, the proposed method simplifies a complex three-phase system in several segments of single or two-phase mixtures. In addition to flow visualization, the novel approach can also be applied to estimate quantitative volume fractions of flowing gas-oil-water mixtures. The proposed method was tested in a horizontal air-oil-water flow loop in different flow conditions. Experimental results suggest that the threshold-based method is able to capture transient three-phase flows with high temporal and spatial resolution even in the presence of water-oil dispersion regardless of the continuous phase. INDEX TERMS Complex impedance, flow visualization, gas-oil-water horizontal flow, three-phase, wiremesh sensor.

Proceedings of the 3rd World Congress on Momentum, Heat and Mass Transfer, Apr 1, 2018

An experimental investigation of slug flow around 90 horizontal bend is presented. This paper de... more An experimental investigation of slug flow around 90 horizontal bend is presented. This paper demonstrates the visual observations during the onset of hydrodynamic slugs. It also presents the axial development of slug flow downstream a horizontal 90 bend. The available slug flow correlations are tested against the experimental results. Air-Silicone oil (viscosity 5 mPa.s) experiments were conducted in a horizontal test section of a 68 mm ID. The behaviour of slug characteristics was studied at 5D upstream and four locations (10D, 40D, 69D and 75D) downstream of the bend using ECT and WMS. The flow around the bend was observed using a high speed imaging system. This work demonstrates that at low gas flow rate hydrodynamic slug flow is mainly generated from the Kelvin-Helmholtz instability. While at high gas superficial velocities (>2.29m.s-1), slugs are developed from the coalescence of roll waves travelling at different velocities. Horizontal 90° bends have inconsiderable effects on the behaviour of slugs. This is due to that the phase separation and momentum transfer being insignificant. The horizontal bend has a minimum influence on the velocity and frequency of the flow structure.

Inventions, 2018

The focus of this work is to examine the effect of flow rate ratio (quotient of the dispersed pha... more The focus of this work is to examine the effect of flow rate ratio (quotient of the dispersed phase flow rate over the continuous phase flow rate) on a regime transition from squeezing to dripping at constant capillary numbers. The effect of the flow rate ratio on the volume of droplets generated in a microfluidic T-junction is discussed, and a new scaling law to estimate their volume is proposed. Existing work on a regime transition reported by several researchers focuses on the effect of the capillary number on regime transition, and the results that are presented in this paper advance the current understanding by indicating that the flow rate ratio is another parameter that dictates regime transition. In this paper, the transition between squeezing and dripping regimes is reported at constant capillary numbers, with a transition region identified between squeezing and dripping regimes. Dripping is observed at lower flow rate ratios and squeezing at higher flow rate ratios, with a...

Qatar Foundation Annual Research Conference Proceedings Volume 2014 Issue 1, 2014

Dispersed water droplets in organic liquids are commonl y encountered in the oil, chemical and bi... more Dispersed water droplets in organic liquids are commonl y encountered in the oil, chemical and biochemical industries. A t ypical example is the separation of dispersed water drops in cr ude oil, in order to prevent catal yst fouling, viscosit y and volume increase, and to meet qualit y specifications of the cr ude oil. Water drops can be removed from a continuous oil phase by various techniques, such as chemical demulsification, gravit y or centrifugal separation, pH adjustment, filtration, heat treatment, membrane separation and electrostatic-enhanced coalescence. Compared to other methods, electrical demulsification is considered to be superior in terms of energ y efficienc y. The electrostatic effects arise from the much higher values of dielectric permittivit y and conductivit y of water in comparison to oil. However, the mechanism of electrocoalescence is still not full y understood and most of the conventional electro-separators are rather bulky. There is, therefore, a compelling need to optimiz e the design and operation of these separators by means of a better fundamental understanding of the under l ying physics. This study aims at investigating the coalescence behaviour of water droplets in sunflower oil when the aqueous phase is present in the form of a chain of droplets. Chains easil y form in an emulsion, since droplets tend to align themsel ves with the direction of the electric field. A pair of ladder-wise electrodes was implemented to set up an electric field almost parallel to the flow direction of the droplets. This design ensures that adjacent droplets in a chain experience the maximum attractive force and does not significantl y disturb the hydrodynamics of the continuous phase. The effect of the electric field strength, frequenc y and waveform on the process performance has been investigated. Both constant and pulsed dc fields have been applied to the dispersion. S inusoidal, sawtooth and square waves have been employed as pulsed dc waveforms. Droplet siz e distributions at the outlet of the device were measured by image anal ysis. The outcomes of the research suggest that it is possible to find a combination of electrical field intensit y, frequenc y and waveform to maximiz e the separation efficienc y.

Journal of Petroleum Science and Engineering, 2018

T-junctions are often used in offshore platforms to partially separate gas from produced fluids. ... more T-junctions are often used in offshore platforms to partially separate gas from produced fluids. Poorly designed T-junctions frequently produce very high liquid (oil and/or water) carryovers, causing major issues to the downstream equipment train which is not designed to handle excessive liquid. This paper reports the liquid carryover experiments in Tjunctions using five different side to main arm diameter ratios under slug flow regime. The obtained phase separation curves can be divided into two component variables; liquidcarryover threshold and peak liquid carryover. The experiments demonstrate that with a decrease in diameter ratio both of these variables decrease. Yet, for superior multiphase flow separation, a high liquid carryover threshold and a low peak liquid carryover are required. Hence, the generally accepted rule that a reduction in diameter ratio improves the phase separation is revealed to be an over-extrapolated statement. The novel findings of this work are: 1) for optimum flow splitting under slug flow conditions, the diameter ratio should be kept between 1 and 0.67, while the diameter ratio 0.67 was found to be most suitable; 2) two correlations were developed for predicting two-phase slug flow separation in different diameter ratio T-junctions. These correlations offer beneficial guidance and clarifications for a number of oil and gas flowline and pipeline applications.

International Journal of Multiphase Flow, 2019

Gas-liquid flows are affected strongly by both the liquid and gas properties and the pipe diamete... more Gas-liquid flows are affected strongly by both the liquid and gas properties and the pipe diameter, which control features and the stability of flow patterns and their transitions. For this reason, empirical models describing the flow dynamics can be applied only to limited range of conditions. Experiments were carried out to study the behaviour of air passing through silicone oil (360 Pa.s) in 240 mm diameter bubble column using Electrical Capacitance Tomography and pressure transducers mounted on the wall. These experiments are aimed at reproducing expected conditions for flows including (but not limited to) crude oils, bitumen, and magmatic flows in volcanic conduits. The paper presents observation and quantification of the flow patterns present. It particularly provides the characteristics of gas-liquid slug flows such as: void fraction; Taylor bubble velocity; frequency of periodic structures; lengths of liquid slugs and Taylor bubbles. An additional flow pattern, churn flow, has been identified. The transition between slug and churn has been quantified and the mechanism causing it are elucidated with the assistance of a model for the draining of the liquid film surrounding the Taylor bubble once this has burst through the top surface of the aerated column of gas-liquid mixture. It is noted that the transition from slug to churn is gradual.

Chemical Engineering Research and Design, 2019

A two-phase flow predictive model with the integration of conservative level-set method (LSM) and... more A two-phase flow predictive model with the integration of conservative level-set method (LSM) and Carreau-Yasuda constitutive equation was developed herein. The LSM was chosen as a potential interface capturing scheme for elucidating the interfacial phenomena including insight into the mechanism of shear-thinning droplets. In present paper, the dynamics of shear-dependent droplet emergence, growth, detachment and translocation in a Newtonian microsystem were examined

Chemical Engineering Science, 2018

Intermittent flows in vertical pipes occur in many industrial settings including power generation... more Intermittent flows in vertical pipes occur in many industrial settings including power generation and downstream oil-and gas production. This type of flows include cap bubble, slug and churn flow regimes. These regimes are of interest as downstream processes and control may heavily depend on the intermittency of the inflow. There are a number of correlations that predicts the features in such flows in vertical pipes. Most of the correlations were developed for air and water fluid pair for slug flow regime in vertical pipes with 25 to 50 mm inner diameter. In this paper, an attempt has been made to assess the suitability of several of these correlations specific to slug flow regime for a fluid pair that is different to air-water system. In this work, air-silicone oil flow development was experimentally investigated in a vertical pipe with an inner diameter of 68mm. A Wire Mesh Sensor (WMS) and an Electrical Capacitance Tomography (ECT) sensor were installed in series at four locations (15D, 30D, 45D and 65D) downstream of the mixing section. The flow was visually observed using a high speed camera. The void fraction time series obtained from the WMS and the ECT were used to establish the flow characteristics such as slug length, slug frequency, void fraction in liquid slugs and Taylor bubble velocity. A comparison showed that the void fraction measurements using ECT and WMS are in good agreement. Axial measurements shows that the flow development beyond 45D is minimal. Change in physical properties of the liquid phase is responsible for the 2 deviation associated with the existing slug flow models, particularly those developed to predict the gas holdup in liquid slugs.

Experimental Thermal and Fluid Science, 2018

Chemical Engineering Science, 2017

International Journal of Multiphase Flow, 2017