Date of Award

May 2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

Gautham Krishnamoorthy

Abstract

Accurately predicting efflux times from tanks with outlet pipes is critical for understanding fluid drainage behavior across a wide range of engineering applications. This study investigates both cylindrical and conical tank geometries using a combination of experimental measurements, analytical and empirical models, and advanced numerical simulations implemented in OpenFOAM, ANSYS Fluent, and DualSPHysics. By examining conditions spanning laminar to turbulent flow regimes, the work evaluates the influence of fluid properties, frictional losses, and modeling approaches on the accuracy of efflux time predictions.Measured and predicted efflux times from cylindrical tanks with an exit pipe were reported using a multi-pronged investigation encompassing measurements, analytical/empirical approaches and 2D/3D simulations invoking different free surface modeling methodologies in: OpenFOAM, ANSYS FLUENT, and DualSPHysics. The range of investigated conditions resulted in efflux-time averaged Reynolds numbers [Reavg] encompassing both laminar and turbulent regimes. A transient mass balance analysis using Torricelli’s equation through an exit orifice resulted in significant errors highlighting the importance of both fluid properties as well as frictional losses. Fully developed laminar flow profiles were able to predict both: efflux times within 6% of the measured values and an increase in efflux time with exit pipe length (due to frictional losses) when Reavg < 325. A modified Bernoulli’s equation with assumed values of entrance and exit losses [K], and friction factors [f] were able to predict both: efflux times to within 12% of the measured values and a decrease in efflux time with an increase in exit pipe length resulting from a higher pressure head in the turbulent scenarios. However, efflux time estimates varied up to 15% when the values of K and f were varied within reasonable limits. Additionally, 3D OpenFOAM simulations using the Volume of Fluid (VOF) methodology resulted in similar fidelities as the modified Bernoulli’s equation across all scenarios. Using 2D axisymmetric VOF simulations in ANSYS FLUENT showed spurious results near the centerline axis, close to complete drainage. Computational constraints enabled the investigations of only hypothetical scenarios using DualSPHysics where the exit pipe diameters were scaled to 3-5 times their actual values. The predicted efflux times were significantly higher than corresponding OpenFOAM, modified Bernoulli equation predictions possibly resulting from inaccurate modeling of fluid-solid interactions at wall boundaries. Efflux times for conical tanks equipped with outlet pipes were evaluated using a combined approach that integrates analytical/empirical formulations with both two- and three-dimensional numerical simulations. These simulations employed diverse free-surface modeling procedures in ANSYS Fluent and DualSPHysics, covering a wide range of circumstances corresponding to average Reynolds numbers spanning equally the laminar and turbulent regimes. The study also analyzed the influence of fluid properties and pipe-related frictional effects, particularly the role of pipe length, on drainage time. An analytical model that assumed fully developed laminar flow while neglecting inlet and outlet losses was able to predict efflux times within 1% of empirical correlations and successfully captured the upsurge in drainage time with increasing pipe length due to friction, especially for Re_avg<461. Two-dimensional ANSYS Fluent simulations using the Volume of Fluid (VOF) method produced results that closely matched those obtained from the modified Bernoulli equation across all tested cases. Due to computational limitations, DualSPHysics simulations were restricted to a set of idealized scenarios with and without outlet pipes. While the predicted efflux times exhibited strong agreement with empirical correlations and analytical estimates, these predicted efflux times were likely due to the method’s effective representation of fluid–solid interactions at boundary surfaces.

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Available for download on Tuesday, June 22, 2027

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