Browsing by Author "Kara, Fuat"

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    Computationally Efficient Stratified Flow Wet Angle Correlation for High Resolution Simulations
    (International Journal of Scientific & Engineering Research, 2019-01) Oloruntoba, Olusola; Kara, Fuat
    In high resolution two-phase pipe flow simulations, such as slug capturing simulation for liquid-gas pipe flow, explicit calculation of stratified flow wet angle has been proposed to improve computational speed of simulations. Most phenomenological and approximate models for obtaining reliable predictions for stratified flow wet angle employ iterative methods or contain long explicit equations which reduce computational efficiency of these models in high-resolution simulations. Therefore, the aim of this study is to adapt a simple mathematical model for predicting stratified flow wet angle to achieve computationally efficient high-resolution liquid-gas pipe flow simulations. The proposed model for predicting stratified flow wet angle is obtained by fitting the generic regression model, Hoerl power law, to analytical stratified flow wet angle data. The proposed model is compared with existing prediction model. Results obtained show that the prediction model proposed gives up to 25.9% savings in computational time over the existing prediction model.
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    Improved Unified Flow Regime Transition Criteria
    (BHR Group, 2016) Oloruntoba, Olusola; Kara, Fuat
    Majority of existing flow regime transition models do not identify the existence of plug and mist flows. Also, these models are applicable to either vertical or horizontal flow. Further, experimental data in literature show that the model of Taitel and Dukler (1976) under predict transition from stratified to annular flow. Present work aims at developing a unified flow regime transition model applicable to all inclination angles. The objectives of this study include: to improve transition from stratified to annular flow, to provide criteria for the existence of plug and mist flow, to develop new criteria for the existence of dispersed bubble flow, and to ensure consistent identification of flow regimes for inclination angles between horizontal and vertical. A modified model to Taitel and Dukler (1976) is proposed to identify transition from stratified to annular flow. A new flow dependent criterion is proposed for the existence of mist flow. Two models are proposed for the existence of plug flow. The first plug model is an exact criterion for the existence of bubble flow. The second plug model is based on experimental data published in literature. A new criterion for the existence of dispersed bubble is developed for vertical flow, and combined with Taitel and Dukler (1976) model for horizontal flow, to obtain a unified transition criterion for all inclination angles. Comparison with experimental data for stratified to annular flow show that present unified flow regime transition model accurately predict 83% of stratified flow, corresponding prediction of Taitel and Dukler (1976) model is lower at 73%. Present model accurately predict 84.6% of experimental data available in literature. First plug model identified 50% of experimental data, while second plug model identified all plug experimental data. Flow regime identification has been carried out for horizontal, vertical, and inclined flows at 30 degrees and 80 degrees, without discontinuities. The major significance of the present study is that better prediction of flow regime would result in application of flow regime specific mechanistic models for better prediction of pressure gradient and liquid holdup. Also, present flow regime transition model can be applied to all inclination angles.
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    Simplified Transient Two-Phase Model for Pipe Flow
    (International Journal of Modern Engineering, 2017) Oloruntoba, Olusola; Kara, Fuat
    Two-phase flow analyses are critical to successful design and operations of two-phase and multiphase pipe flow applications found in major industrial fields, such as petroleum, nuclear, chemical, geothermal and space industries. Due to difficulties in obtaining analytical transient solutions, approximate solutions have been applied to two-phase pipe flow. However, these approximate solutions neglect convective terms in two-phase Navier-Stokes equations. The aim of this current study was to develop transient tools to predict transient two-phase pipe flow. The objectives of this study were to develop a simplified transient model and to validate the proposed model with published experimental data. A simplified transient two-phase pipe flow model was obtained in this study by simplifying the two-phase Navier-Stokes equations. The simplified equations include: (i) a transient continuity equation of combined two-phase flow that includes two new dimensionless terms; (ii) transient two-phase momentum equations that account for convective terms only; and, (iii) a steady state pressure gradient.