virkeshwar kumar

Scopus Publications

Salt Creeping and Crystal Lifting in Ternary Droplets on Hydrophobic Substrates
Narendra Ch. Kumar, Virkeshwar Kumar
Langmuir, 2026
Salt creeping during evaporative crystallization is generally associated with hydrophilic substrates, where capillary spreading of the saline solution promotes lateral crystal growth. In contrast, hydrophobic surfaces are typically expected to suppress such spreading. Here, we demonstrate the unexpected and sustained occurrence of salt creeping on both hydrophobic and superhydrophobic substrates during the evaporative crystallization of ternary saline droplets. To establish the generality of this phenomenon, multiple ternary systems are investigated, including water–NaCl–KCl, water–NaCl–KNO3, water–NaCl–NH4Cl, water–KCl–KNO3, water–KCl–NH4Cl, and water–KNO3–NH4Cl, over a broad substrate temperature range of 40–135 °C. Detailed experiments with water–NaCl–KCl mixtures on heated substrates reveal distinct creeping deposition patterns and crystal lifting, accompanied by systematic changes in contact angle, deposit height, and lateral footprint. Morphological analysis shows that ternary crystallization promotes elongated and hopper-type crystals that form interconnected porous networks rather than simple cubic structures. These networks act as efficient capillary pathways, sustaining liquid transport and enabling lateral redistribution of the solution, even on hydrophobic substrates. A local mass-balance between the capillary wicking flux and crystallization indicates that the extent of creeping is governed by the competition between these two processes. At elevated temperatures, this balance shifts, producing a transition from dominant creeping to a mixed regime of creeping and crystal lifting, revealing distinct temperature-dependent deposition behavior. Overall, this work proposes a generalized mechanism based on capillary-driven mass flux to explain salt creeping on hydrophobic substrates and highlights the critical role of crystal morphology in controlling liquid transport and deposit evolution during multicomponent evaporative crystallization.
Review on advances in wet underwater arc welding: Thermo-mechanical aspects and emerging machine learning approach
Shashikumar Maurya, Keval S. Ramani, Virkeshwar Kumar
Journal of Manufacturing Processes, 2026
Correction: Grain Refinement and Corrosion Behavior of Solid-State Additive Manufacturing of AA6063 Al Alloy Composite (JOM, (2026), 10.1007/s11837-026-08245-1)
Pradyumn Kumar Arya, Virkeshwar Kumar, Neelesh Kumar Jain, Dan Sathiaraj, Pasquale Cavaliere, Behzad Sadeghi
JOM, 2026
Grain Refinement and Corrosion Behavior of Solid-State Additive Manufacturing of AA6063 Al Alloy Composite
Pradyumn Kumar Arya, Virkeshwar Kumar, Neelesh Kumar Jain, Dan Sathiaraj, Pasquale Cavaliere, Behzad Sadeghi
JOM, 2026
Multicomponent Droplet Crystallization: Latent Heat Release and Bubble Formation
Narendra Ch. Kumar, Virkeshwar Kumar
Langmuir, 2025
Bubble formation in evaporating saline droplets at subboiling temperatures is a striking and nonintuitive phenomenon that challenges conventional understanding of phase change processes. In this study, the mechanisms of bubble formation are systematically investigated in ternary saline droplets (water + two salts) with different combinations of high- and low-latent heat of solid formation (LHSF) salts, which can potentially be extended to multicomponent systems encompassing all possible combinations. The results reveal that bubble formation is not governed solely by the LHSF but also critically by the rate at which this latent heat is released. Real-time imaging is employed to capture the onset of nucleation, crystal growth, and bubble evolution, while in situ thermocouple measurements provide direct evidence of transient thermal fluctuations. A one-dimensional energy balance at the solid-liquid interface demonstrates that the governing parameter is not LHSF alone but the combined influence of latent heat release and the kinetics of crystal growth. Bubble formation is consistently observed in droplets containing high-LHSF salts as well as in high-high and high-low LHSF combinations, the latter mainly due to the presence of high-LHSF salts. Remarkably, certain low-low LHSF systems also produce bubbles when crystallization proceeds at sufficiently high growth rates. These findings establish that bubble formation arises from the interplay between the thermodynamic magnitude (LHSF) and the kinetic rate (growth), thereby proposing a generalized mechanism for this unusual phenomenon.
Transport phenomena during solidification and melting of water: Experimental and numerical studies
Radhika Sarawagi, Abhishek Kumar Singh, Virkeshwar Kumar
International Journal of Thermal Sciences, 2025
Successive solidification and melting of binary salt-water system: Convection and double-diffusive layer formation
Radhika Sarawagi, Virkeshwar Kumar
Physics of Fluids, 2025
The dynamics of successive solidification and melting in binary salt systems are governed by intricate interactions between thermal and solutal convection, mushy zone evolution, and density stratification. While prior studies have examined double-diffusive convection in salt–water systems, the successive pathways of solidification and melting—particularly the staged life cycle of double-diffusive layer (DDL) formation during melting—remain unexplored. In this study, the phase-change behavior of water–NH4Cl solutions at hypo-, eutectic-, and hyper-eutectic compositions is investigated using in situ digital single-lens reflex imaging, shadowgraph visualization, thermocouple measurements, concentration sampling, and validated numerical simulations with user-defined functions in ANSYS Fluent. Solidification in the hypo-eutectic regime is dominated by strong thermosolutal convection, leading to mushy zone growth, solute accumulation, and eventual bridging, while melting generates transient DDLs and wavy interfaces. In the eutectic regime, solidification proceeds in an orderly manner without mush formation, governed by stable thermal convection rolls and a prolonged isothermal plateau, whereas melting is rapid, highly convective, and marked by temperature oscillations and vigorous interface variation. The hyper-eutectic regime exhibits dendritic NH4Cl growth, dendrite fragmentation, and preferential eutectic front formation during solidification, while melting proceeds asymmetrically from eutectic-rich top regions, producing stratified DDLs that extend downward in a filling-box mechanism. The staged life cycle of DDL formation—onset, preferential top melting, layered stratification, and eventual merging—is established for the first time in binary melting. This work provides the first mechanistic framework for understanding DDL-driven successive solidification and melting in multicomponent phase-change systems, with implications for desalination, thermal energy storage, and alloy solidification.
Transport phenomena during saline water solidification under top-cooling configuration for desalination purpose
Narendra Chadalavada Kumar, Deven Hitendrabhai Patel, Virkeshwar Kumar
Heat and Mass Transfer Waerme Und Stoffuebertragung, 2025
Effect of permanent magnetic field positioning on microstructure and mechanical properties of casted Al-Cu alloy
Rajesh Kumar Pradhan, Pradyumn Kumar Arya, Prashant Kashyap, Shashikumar Maurya, Virkeshwar Kumar
Journal of Alloys and Compounds, 2025
Drop spreading characteristics over a micro-pillared surface and comparison with an equivalent flat surface
C. Ramgopal, K. Muralidhar, Virkeshwar Kumar
Physics of Fluids, 2025
Low-Weber-number droplet impacts (We &lt; 1) are crucial in applications such as dropwise condensation, microfluidics, inkjet printing, and spray coating where surface tension is dominant. The present study investigates the spreading of millimetric droplets on micro-pillared surfaces with varying pitch (15, 30, and 60 μm) and Weber numbers (0.21, 1, and 3.9), encompassing capillary, transition, and inertia-dominated regimes. Experimental observations reveal distinct jet ejection regimes, including transitions from entrapped jets to singular thin jets with increasing Weber numbers. Multiple bouncing was observed on sparsely spaced pillars at lower Weber numbers. A numerical model employing an equivalent flat surface approximation, incorporating a dynamic contact angle model for a pillared surface, was utilized to obtain droplet shapes and spreading patterns. This approach successfully predicted droplet deformation in the capillary and inertia-dominated regimes. To account for the influence of liquid penetration into the pillar spacing at higher impact velocities, the contact angle parameters were suitably modified, resulting in improved agreement between simulations and experiments across all impact regimes. These findings highlight the importance of liquid penetration between pillars for accurately predicting wetting state transitions during droplet impact dynamics on micro-pillared surfaces.
A Novel Method for Maintaining Low and Constant Salinity in Ice during Desalination of Binary Mixtures Using Directional Top-Cooling Solidification
Narendra Ch. Kumar, Radhika Sarawagi, Virkeshwar Kumar
ACS Es and T Water, 2025
A mechanism for the bubble formation during evaporative crystallization of saline droplets below boiling point
Narendra Ch. Kumar, Virkeshwar Kumar
International Communications in Heat and Mass Transfer, 2024
Image-Based Detection of Adulterants in Milk Using Convolutional Neural Network
Adhyayan Mamgain, Virkeshwar Kumar, Susmita Dash
ACS Omega, 2024
Real-Time Strengthening of Natural Convection and Dendrite Fragmentation During Binary Mixture Freezing
Virkeshwar Kumar, Shyamprasad Karagadde, Kamal Meena
Lecture Notes in Mechanical Engineering, 2024
Enhancing actuation frequency of shape memory alloy-based system with a novel evaporative cooling technique for fast cyclic applications
Kanhaiya Lal Chaurasiya, Navya Gupta, Fahad Javeed, Virkeshwar Kumar, Bishakh Bhattacharya
Proceedings of SPIE the International Society for Optical Engineering, 2024
Generality of Evaporative Crystal Liftoff on Heated Hydrophobic Substrates
Pranjal Agrawal, Virkeshwar Kumar, Samantha McBride, Susmita Dash
Langmuir, 2023
Patterns during Evaporative Crystallization of a Saline Droplet
Virkeshwar Kumar, Susmita Dash
Langmuir, 2022
Convection-induced bridging during alloy solidification
Virkeshwar Kumar, Ketan Sakalkale, Shyamprasad Karagadde
Physics of Fluids, 2022
Evaporation-Based Low-Cost Method for the Detection of Adulterant in Milk
Virkeshwar Kumar, Susmita Dash
ACS Omega, 2021
Role of microstructure and composition on natural convection during ternary alloy solidification
Virkeshwar Kumar, Atul Srivastava, Shyamprasad Karagadde
Journal of Fluid Mechanics, 2021
Shrinkage induced flow during directional solidification of pure substance in a bottom cooled cavity: A study on flow reversal phenomena
Aniket D. Monde, Oaj Chawla, Virkeshwar Kumar, Shyamprasad Karagadde, Prodyut R. Chakraborty
Physics of Fluids, 2020
Characteristics of solidification-driven double-diffusive layers in mixtures
Virkeshwar Kumar, Atul Srivastava, Shyamprasad Karagadde
Journal of Flow Visualization and Image Processing, 2020
On the mechanism responsible for unconventional thermal behaviour during freezing
Virkeshwar Kumar, G. S. Abhishek, Atul Srivastava, Shyamprasad Karagadde
Journal of Fluid Mechanics, 2020
Generalized regimes for the formation of stratified regions during freezing of multi-component mixtures
Virkeshwar Kumar, Atul Srivastava, Shyamprasad Karagadde
Physics of Fluids, 2019
Compositional dependency of double-diffusive layers during binary alloy solidification: Full-field measurements and quantification
Virkeshwar Kumar, Atul Srivastava, Shyamprasad Karagadde
Physics of Fluids, 2018
Real-Time Observations of Density Anomaly Driven Convection and Front Instability during Solidification of Water
Virkeshwar Kumar, Atul Srivastava, Shyamprasad Karagadde
Journal of Heat Transfer, 2018
Do the intrusive probes alter the characteristic length-scales of natural convection?
Virkeshwar Kumar, Atul Srivastava, Shyamprasad Karagadde
Journal of Flow Visualization and Image Processing, 2018
Mechanism of flow reversal during solidification of an anomalous liquid
Virkeshwar Kumar, Mitesh Kumawat, Atul Srivastava, Shyamprasad Karagadde
Physics of Fluids, 2017

virkeshwar kumar

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Scopus Publications