Vatsal Sanjay

University of Twente | UT · Group of Physics of Fluids (POF)

When a liquid drop falls on a solid substrate, the air layer in between them delays the occurrence of liquid--solid contact. For impacts on smooth substrates, the air film can even prevent wetting, allowing the drop to bounce off with dynamics identical to that observed for impacts on superamphiphobic materials. In this article, we investigate simi...

This thesis investigates several free-surface phenomena to illustrate the role of viscous stresses. In part I (chapters 1-4), we study the impact of spherical liquid drops on non-wetting substrates. After impact on a rigid substrate, a falling liquid drop deforms and spreads, owing to the normal reaction force. Subsequently, if the substrate is n...

Non-wetting substrates allow impacting liquid drops to spread, recoil, and takeoff, provided they are not too heavy (Biance et al. 2006) or too viscous (Jha et al. 2020). In this article, using direct numerical simulations with the volume of fluid method, we investigate how viscous stresses and gravity conspire against capillarity to inhibit drop r...

A falling liquid drop, after impact on a rigid substrate, deforms and spreads, owing to the normal reaction force. Subsequently, if the substrate is nonwetting, the drop retracts and then jumps off. As we show here, not only is the impact itself associated with a distinct peak in the temporal evolution of the normal force, but also the jump-off, wh...

When a freely suspended liquid film ruptures, it retracts spontaneously under the action of surface tension. If the film is surrounded by air, the retraction velocity is known to approach the constant Taylor–Culick velocity. However, when surrounded by an external viscous medium, the dissipation within that medium dictates the magnitude of the retr...

Non-wetting substrates allow impacting liquid drops to spread, recoil and take-off, provided they are not too heavy (Biance et al. , J. Fluid Mech. , vol. 554, 2006, pp. 47–66) or too viscous (Jha et al. , Soft Matt. , vol. 16, no. 31, 2020, pp. 7270–7273). In this article, using direct numerical simulations with the volume of fluid method, we inve...

When a liquid drop falls on a solid substrate, the air layer between them delays the occurrence of liquid–solid contact. For impacts on smooth substrates, the air film can even prevent wetting, allowing the drop to bounce off with dynamics identical to that observed for impacts on superamphiphobic materials. In this paper, we investigate similar bo...

When a freely suspended liquid film ruptures, it retracts spontaneously under the action of surface tension. If the film is surrounded by air, the retraction velocity is known to approach the constant Taylor-Culick velocity. However, when surrounded by an external viscous medium, the dissipation within that medium dictates the magnitude of the retr...

A falling liquid drop, after impact on a rigid substrate, deforms and spreads, owing to the normal reaction force. Subsequently, if the substrate is non-wetting, the drop retracts and then jumps off. As we show here, not only is the impact itself associated with a distinct peak in the temporal evolution of the normal force, but also the jump-off, w...

When a rising bubble in a Newtonian liquid reaches the liquid-air interface, it can burst, leading to the formation of capillary waves and a jet on the surface. Here, we numerically study this phenomenon in a yield stress fluid. We show how viscoplasticity controls the fate of these capillary waves and their interaction at the bottom of the cavity....

When a rising bubble in a Newtonian liquid hits the liquid-air interface, it can burst, leading to the formation of capillary waves and a jet on the surface. Here, we numerically study this phenomenon in a yield stress fluid. We show how viscoplasticity controls the fate of these capillary waves and their interaction at the bottom of the cavity. Un...

Colliding drops are encountered in everyday technologies and natural processes, from combustion engines and commodity sprays to raindrops and cloud formation. The outcome of a collision depends on many factors, including the impact velocity and the degree of alignment, and intrinsic properties like surface tension. Yet, little is known on binary im...

Colliding drops are widely encountered in everyday technologies and natural processes, from combustion engines and commodity sprays to raindrops and cloud formation. The outcome of a collision depends on many factors, including the impact velocity and the degree of head-on alignment, in addition to intrinsic properties like surface tension. Yet lit...

When a millimetric water drop is gently deposited on a silicone oil bath, it reaches a temporarily stable shape supported by a thin lubricating air layer. Upon the drainage of this layer, a triple contact line (between air, water, and oil) forms. Owing to the positive spreading coefficient of silicone oil, it tries to maximize its surface area. Thi...

The main focus of the present work is to investigate the collision of two oblique cylindrical water jets through a series of experiments. Different regimes for the collision of water jets are illustrated and transitions to the fingering instability and subsequently to the violent flapping regime are discussed. The collision between high inertia and...

Separation of particulate impurities from liquid medium became indispensable in areas like water filtration. In the present study, FVM-LPP coupling based numerical framework is used to investigate the settling of the particles in a rectangular microchannel for different inlet flow Reynolds numbers within the range 50 to 300. Water with particle lad...

We have explored different configurations of bubble entrainment inside a liquid pool resulting from the impact of plunging jets. We delve into the asymmetries arising due to impingement of an inclined jet. The aberrations from the symmetric case have been realized in the genesis of the entrainment, including the formation and collapse of the annula...

Interactions between two facing liquid jets and consequences of jet impingement onto a pool are studied using detailed numerical simulations and intelligent experimental investigations. The collision between liquid jets leads to the formation of a sheet in the median plane and is illustrated numerically. The sheet subsequently transforms into a cha...

The fire ignited due to Air Conditioner (A/C) malfunctioning is studied numerically for a single room, two rooms with interconnection, two interconnected rooms with attached corridor and a two-storeyed building with stairs. Coupled finite difference and finite volume based open source solver, Fire Dynamics Simulator (FDS) is used for domain discret...

This presentation may be downloaded for personal use only. The author (Vatsal Sanjay) has presented this as a part of Master’s thesis evaluation. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Sanjay, V. and Das, A. K., “Formation of liquid chain by collision of two laminar jets,” Physics...

Supplementary material for the complete movie of the time sequenced still images provided in Fig. 4 of the article: Sanjay, V. and Das, A. K., “Formation of liquid chain by collision of two laminar jets,” Physics of Fluids 29, 112101 (2017), https://doi.org/10.1063/1.4998288.

The collision of liquid jets and formation of a sheet in the median plane is illustrated numerically. The sheet subsequently transforms into a chain like fluidic structure with successive dwarf links in mutually orthogonal planes. To understand the behavior of fluid parcels inside the chain, flow kinematics are studied with streamlines and a self-s...

Full text available at http://onlinelibrary.wiley.com/doi/10.1002/aic.15828/epdf Air entrainment due to impingement of a water jet on a pool is studied extensively to understand the physics of the initiation and the cluster of bubbles formed below the free surface. Possible outcomes due to the jet impingement in a pool have been identified as smoo...

Two phase flows are ubiquitous in nature and industries, from atomization of shower jets to the entrainment process in huge industrial mixtures. Numerical simulation of these phenomena can help us to not just understand the fundamental Physics involved but also to design accurate equipment. More often than not, these involve multiple scales from th...

Head on oblique collision of two horizontal jets is studied extensively using numerical simulations to understand the Physics behind the formation of liquid sheet in a plane perpendicular to the motion of the jets. Behavior of jets is also studied prior to the formation of this sheet. Attempts have been made to demonstrate the initiation process of...

Atomization of a liquid jet is studied numerically with the aid of a two-way coupled Eulerian-Lagrangian model. Detailed simulations are carried out for the phenomenological study of two cases of atomization, namely shear induced atomization due to high gas flow around the circular jet and modulated velocity instability induced atomization. Co-rela...

Free surface vortex structures are often observed as the liquid flows out of a typical kitchen sink (or from any liquid pool). In the current article, we will be discussing the phenomenological study of the gravity driven free surface vortices using numerical simulations. As the liquid drains out, there are three forces acting upon it. The force of...

We have presented here the details (compilation) of image analysis carried out under on experimental and numerical output images and videos. The best thing about images is that they are simply matrices whereby the pixel size (mxn) is simply the rows m and columns n. The best way to manipulate matrices is to use matlab. In a given image, pixel size...

Fire dynamics and fire propagation study reckon attention due to the role they play in evacuation planning and minimizing the loss of lives and properties in case of a fire breakout. For this paper, Fire Dynamics Simulator (FDS) is used to simulate a fire situation involving an air conditioning device in a two-room domain. The rooms are connected t...