BITS Faculty Publications

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Author: search.filters.author.Yadav, Shyam SunderSubject: search.filters.subject.Mechanical engineering

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    Influence of electric potential boundary condition on the electrospraying process
    (Elsevier, 2025-08) Rao, Venkatesh K.P.; Yadav, Shyam Sunder
    In the current work, we perform three dimensional numerical simulations of the electrospraying process. Our aim is to investigate the effect of electric potential boundary condition on the electrospraying process of a liquid. We observe a steady electrospraying process in the cone jet mode for the case of uniform electric potential boundary condition. On the other hand, we observe a highly unsteady, violent electrospraying process for the case of non-uniform boundary condition. We provide explanation of this widely different behavior of the electrospraying process.
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    A three-dimensional open-source solver for incompressible viscoelastic two-component flows
    (ASME, 2025-10) Rao, Venkatesh K.P.; Yadav, Shyam Sunder
    In this study, we unveil a three-dimensional flow solver designed to simulate viscoelastic two-phase flows using the Oldroyd-B formulation. Acknowledging the challenges that researchers encounter in this dynamic field, we have integrated the three-dimensional Log conformation approach into the open-source flow solver basilisk, significantly enhancing its capabilities beyond its two-dimensional predecessors. Our solver stands as a testament to rigorous testing against a wide range of three-dimensional viscoelastic flow challenges, encompassing both single and two-phase scenarios drawn from established literature. True to its two-dimensional roots, it exhibits extraordinary robustness, adeptly managing viscoelastic flows, even at high Weissenberg numbers. By offering this powerful solver as an open-source resource, we aspire to empower the computational fluid dynamics community. We believe it will become an invaluable tool for researchers delving into the complexities of viscoelastic flows, fostering innovation and inspiring new progress in the field.
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    A comparison of classical nucleation theory and thermal phase change based condensation models
    (IOP, 2024) Yadav, Shyam Sunder; Dasgupta, Mani Sankar
    In this work, we perform numerical simulations of the condensation process of CO2 inside a converging-diverging nozzle. We use Ansys Fluent for the simulation work. The real gas properties of CO2 are generated in tabular form (including metastable states) using NIST Refprop. We compare the distribution of physical quantities during the high-speed, compressible flow of CO2 inside a nozzle under the Classical Nucleation Theory (CNT) and the Thermal Phase Change (TPC) models. The CNT model is known to be accurate but computationally expensive while the TPC model is computationally cheaper. We observe that the TPC model predicts a knee in the pressure distribution near the throat of the nozzle while CNT predicts a continuous decrease in the pressure. The two solvers predict slightly different temperature, supercooling and liquid mass fraction values in the diverging part of the nozzle. The compressible, phase change simulations under high speed conditions can be performed quickly with the TPC solver. Overall, the TPC based solver appears to be a reliable alternative to the CNT based model.
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    Impact of microgrooves on supersonic CO2 condensation and pressure recovery in a converging-diverging nozzle
    (Elsevier, 2025-08) Yadav, Shyam Sunder
    As global awareness of climate change grows, innovative CO2 capture solutions are crucial for sustainability. This research explores the potential of supersonic condensation-based separation as an advanced method for CO2 capture, leveraging the principles of supersonic flow and rapid condensation. The study employs computational fluid dynamics (CFD) modeling to simulate the behavior of CO2 during the phase change process in a converging-diverging nozzle. Three nozzle wall surface conditions were examined: smooth surface, 35-μm roughness, and microgrooves (0.35 mm height, 1 mm width) on the diverging section. The CFD based results are in good agreement with experimental data from the literature. The key findings include: (1) microgrooves enhance the pressure recovery post-condensation; (2) extended nucleation regions and multiple shockwaves are observed with microgrooves; (3) The smooth wall nozzle achieves the highest liquid condensation effectiveness at 15.7 %, compared to 12.7 % for the rough wall and 12 % for the microgroove wall nozzle., indicating the highest CO2 capture efficiency with smooth walls. The microgroove geometry promoted better fluid mixing but reduced overall condensation. This research contributes to developing sustainable carbon management technologies, providing valuable insights into optimizing the nozzle design and flow dynamics for enhanced CO2 capture performance.
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    Design of experiments-based optimization of supersonic nozzles for enhanced methane capture
    (2025-06) Yadav, Shyam Sunder; Dasgupta, Mani Sankar
    Computational fluid dynamics (CFD) simulations are employed in this study to optimize key geometric parameters of supersonic nozzles, aiming to enhance methane capture efficiency through non-equilibrium condensation mechanisms. A Design of Experiments (DoE) approach was used to systematically vary key geometric parameters of a converging-diverging Laval nozzle, including inlet radius, throat radius, divergence angle, and section lengths. The non-equilibrium condensation of CH4 under metastable conditions was modeled using a custom implementation of Classical Nucleation Theory. The computational model demonstrated high accuracy when validated against experimental data for both steam and CO₂, supporting its reliability for multi-species condensation simulations. Performance metrics including exergy loss, thermal efficiency, and condensation efficiency were evaluated across 32 nozzle configurations. Four designs demonstrated superior performance, with one configuration (Run ID 22) emerging as optimal, exhibiting the highest condensation efficiency and extensive supercooling zones. The optimized design maintained stable performance across a range of inlet temperatures (240–260 K) and pressures (65–75 bar). The optimized design maintained thermal efficiencies above 91% and exergy losses below 10% and maximum condensation efficiency of 17% across a range of inlet conditions. This work establishes a foundation for designing efficient supersonic separators for methane capture, with potential applications in natural gas processing and greenhouse gas mitigation.