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Nagesh D. Patil

Bio: Nagesh D. Patil is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Particle & Evaporation. The author has an hindex of 9, co-authored 20 publications receiving 346 citations. Previous affiliations of Nagesh D. Patil include Indian Institute of Technology Bombay & University of British Columbia.

Papers
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Journal ArticleDOI
01 Nov 2016-Langmuir
TL;DR: In this paper, the effects of substrate temperature, substrate wettability, and particle concentration are experimentally investigated for evaporation of a sessile water droplet containing colloidal particles.
Abstract: Effects of substrate temperature, substrate wettability, and particle concentration are experimentally investigated for evaporation of a sessile water droplet containing colloidal particles. Time-varying droplet shapes and temperature of the liquid–gas interface are measured using high-speed visualization and infrared thermography, respectively. The motion of the particles inside the evaporating droplet is qualitatively visualized by an optical microscope and the profile of the final particle deposit is measured by an optical profilometer. On a nonheated hydrophilic substrate, a ring-like deposit forms after the evaporation, as reported extensively in the literature, while on a heated hydrophilic substrate, a thinner ring with an inner deposit is reported in the present work. The latter is attributed to Marangoni convection, and recorded motion of the particles as well as measured temperature gradient across the liquid–gas interface confirms this hypothesis. The thinning of the ring scales with the substr...

114 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of pitch of the pillars and impact velocity on the impact dynamics of a microliter water droplet on a micropillared hydrophobic surface was studied qualitatively by high-speed photography and quantitatively by the temporal variation of wetted diameter and droplet height.

96 citations

Posted Content
TL;DR: A first-order model corroborates the liquid-gas interface temperature measurements and variation in the measured ring profile with the substrate temperature, and proposes a regime map for predicting three types of deposits-namely, ring, thin ring with inner deposit, and inner deposit-for varying substrate temperature.
Abstract: Effects of substrate temperature, substrate wettability and particles concentration are experimentally investigated for evaporation of a sessile water droplet containing colloidal particles. Time-varying droplet shapes and temperature of the liquid-gas interface are measured using high-speed visualization and infrared thermography, respectively. The motion of the particles inside the evaporating droplet is qualitatively visualized by an optical microscope and profile of final particle deposit is measured by an optical profilometer. On a non-heated hydrophilic substrate, a ring-like deposit forms after the evaporation, as reported extensively in the literature; while on a heated hydrophilic substrate, a thinner ring with an inner deposit is reported in the present work. The latter is attributed to Marangoni convection and recorded motion of the particles as well as measured temperature gradient across the liquid-gas interface confirms this hypothesis. The thinning of the ring scales with the substrate temperature and is reasoned to stronger Marangoni convection at larger substrate temperature. In case of a non-heated hydrophobic substrate, an inner deposit forms due to very early depinning of the contact line. On the other hand, in case of a heated hydrophobic substrate, the substrate heating as well as larger particle concentration helps in the pinning of the contact line, which results in a thin ring with an inner deposit. We propose a regime map for predicting three types of deposits namely, ring, thin ring with inner deposit and inner deposit - for varying substrate temperature, substrate wettability and particles concentration. A first-order model corroborates the liquid-gas interface temperature measurements and variation in the measured ring profile with the substrate temperature.

52 citations

Journal ArticleDOI
12 Sep 2017-Langmuir
TL;DR: In this article, the impact dynamics of a microliter water droplet on a hydrophobic microgrooved surface were investigated and the effect of the pitch of the grooved surface and Weber number on the droplet dynamics and impact outcome was studied.
Abstract: We experimentally investigate the impact dynamics of a microliter water droplet on a hydrophobic microgrooved surface. The surface is fabricated using photolithography, and high-speed visualization is employed to record the time-varying droplet shapes in the transverse and longitudinal directions. The effect of the pitch of the grooved surface and Weber number on the droplet dynamics and impact outcome are studied. At low pitch and Weber number, the maximum droplet spreading is found to be greater in the longitudinal direction than the transverse direction to the grooves. The preferential spreading inversely scales with the pitch at a given Weber number. In this case, the outcome is no bouncing (NB); however, this changes at larger pitch or Weber number. Under these conditions, the following outcomes are obtained as a function of the pitch and Weber number: droplet completely bounces off the surface (CB), bouncing occurs with droplet breakup (BDB), or no bouncing because of a Cassie to Wenzel wetting tran...

45 citations

Journal ArticleDOI
29 May 2018-Langmuir
TL;DR: Investigation of deposit patterns and associated morphology formed after the evaporation of an aqueous droplet containing mono- and bidispersed colloidal particles finds that there exists a critical substrate temperature as well as a diameter ratio to achieve the sorting.
Abstract: Here, we investigate deposit patterns and associated morphology formed after the evaporation of an aqueous droplet containing mono- and bidispersed colloidal particles. In particular, the combined effect of substrate heating and particle diameter is investigated. We employ high-speed visualization, optical microscopy, and scanning electron microscopy to characterize the evaporating droplets, particle motion, and deposit morphology, respectively. In the context of monodispersed colloidal particles, an inner deposit and a typical ring form for smaller and larger particles, respectively, on a nonheated surface. The formation of the inner deposit is attributed to early depinning of the contact line, explained by a mechanistic model based on the balance of several forces acting on a particle near the contact line. At larger substrate temperature, a thin ring with inner deposit forms, explained by the self-pinning of the contact line and advection of the particles from the contact line to the center of the drop...

32 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: In this paper, a brief review of potential applications of superhydrophobic surfaces is presented, which thoroughly focuses on the most recent advances regarding dynamics and kinematics of drop impinging super-hydrophilic substrates.

248 citations

01 Jan 2009
TL;DR: The results imply that the multiscale surface roughness at nanoscale plays a minor role in the impact events for small The authors less than or approximately equal 120 but an important one for large They greater than or about equal 120.
Abstract: We experimentally investigate drop impact dynamics onto different superhydrophobic surfaces, consisting of regular polymeric micropatterns and rough carbon nanofibers, with similar static contact angles. The main control parameters are the Weber number We and the roughness of the surface. At small We, i.e., small impact velocity, the impact evolutions are similar for both types of substrates, exhibiting Fakir state, complete bouncing, partial rebouncing, trapping of an air bubble, jetting, and sticky vibrating water balls. At large We, splashing impacts emerge forming several satellite droplets, which are more pronounced for the multiscale rough carbon nanofiber jungles. The results imply that the multiscale surface roughness at nanoscale plays a minor role in the impact events for small We less than or approximately equal 120 but an important one for large We greater than or approximately equal 120. Finally, we find the effect of ambient air pressure to be negligible in the explored parameter regime We less than or approximately equal 150.

246 citations

01 Jan 2017
TL;DR: In this article, the authors summarize the main models for moving contact lines and follow with an overview of computational methods that include direct continuum approaches and macroscale models that resolve only the large-scale flow by modeling the effects of the conditions near the contact line using theory.
Abstract: Computational methods have been extended recently to allow for the presence of moving contact lines in simulated two-phase flows. The predictive capability offered by these methods is potentially large, joining theoretical and experimental methods. Several challenges rather unique to this area need to be overcome, however, notably regarding the conditions near a moving contact line and the very large separation of length scales in these flows. We first summarize the main models for moving contact lines and follow with an overview of computational methods that includes direct continuum approaches and macroscale models that resolve only the large-scale flow by modeling the effects of the conditions near the contact line using theory. Results are presented for contact-line motion on ideal as well as patterned and grooved surfaces and for extensions to account for complexities such as thermocapillarity and phase change.

234 citations

Journal ArticleDOI
TL;DR: In this article, the mass transfer process, the formation and evolution of phase fronts and the identification of mechanisms of pattern formation are discussed, and several potential directions for future research in this area are discussed.

227 citations