scholarly journals Gravitational Effects in the Collision of Elasto-Viscoplastic Drops on a Vertical Plane

Fluids ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 61 ◽  
Author(s):  
Cassio M. Oishi ◽  
Fernando P. Martins ◽  
Roney L. Thompson
Keyword(s):  
Free Surface ◽  
Vertical Plane ◽  
Solid Substrate ◽  
Surface Approach ◽  
Surface Evolution ◽  
Gravitational Effects ◽  
Practical Applications ◽  
Rich Variety ◽  
Complex Fluid ◽  
Marker And Cell Method

The collision of drops in a solid substrate is an interesting problem with several practical applications. When the drop is made of a complex fluid the problem presents numerical challenges due to the interaction of the mechanical properties and the free surface approach. In the present work, we solve the numerical problem of elasto-viscoplastic drops colliding in vertical plane. The free surface evolution is handled by a Marker-And-Cell method combined with a Front-Tracking interface representation. Special emphasis is given to the gravitational effects by means of exploring the Froude number. We were able to find a rich variety of outputs that can be classified as sticking, sliding, bouncing, detaching, and slithering.

The Introduction of Micro Cells to Treat Pressure in Free Surface Fluid Flow Problems

1995 ◽  
Vol 117 (4) ◽  
pp. 683-690 ◽  
Author(s):  
Peter E. Raad ◽  
Shea Chen ◽  
David B. Johnson
Keyword(s):  
Fluid Flow ◽  
Free Surface ◽  
Pressure Field ◽  
Flow Simulation ◽  
New Method ◽  
Computational Domain ◽  
Critical Feature ◽  
Flow Problems ◽  
Macro Cell ◽  
Marker And Cell Method

A new method of calculating the pressure field in the simulation of two-dimensional, unsteady, incompressible, free surface fluid flow by use of a marker and cell method is presented. A critical feature of the new method is the introduction of a finer mesh of cells in addition to the regular mesh of finite volume cells. The smaller (micro) cells are used only near the free surface, while the regular (macro) cells are used throughout the computational domain. The movement of the free surface is accomplished by the use of massless surface markers, while the discrete representation of the free surface for the purpose of the application of pressure boundary conditions is accomplished by the use of micro cells. In order to exploit the advantages offered by micro cells, a new general equation governing the pressure field is derived. Micro cells also enable the identification and treatment of multiple points on the free surface in a single surface macro cell as well as of points on the free surface that are located in a macro cell that has no empty neighbors. Both of these situations are likely to occur repeatedly in a free surface fluid flow simulation, but neither situation has been explicitly taken into account in previous marker and cell methods. Numerical simulation results obtained both with and without the use of micro cells are compared with each other and with theoretical solutions to demonstrate the capabilities and validity of the new method.

scholarly journals Diagnostic and prognostic simulations with a full Stokes model accounting for superimposed ice of Midtre Lovénbreen, Svalbard

2009 ◽  
Vol 3 (2) ◽  
pp. 217-229 ◽  
Author(s):  
T. Zwinger ◽  
J. C. Moore
Keyword(s):  
Free Surface ◽  
Steady State ◽  
Thermal State ◽  
Steady State Solution ◽  
Radar Data ◽  
Data Set ◽  
Surface Evolution ◽  
Steady State Model ◽  
Elevation Changes ◽  
Ground Penetrating

Abstract. We present steady state (diagnostic) and transient (prognostic) simulations of Midtre Lovénbreen, Svalbard performed with the thermo-mechanically coupled full-Stokes code Elmer. This glacier has an extensive data set of geophysical measurements available spanning several decades, that allow for constraints on model descriptions. Consistent with this data set, we included a simple model accounting for the formation of superimposed ice. Diagnostic results indicated that a dynamic adaptation of the free surface is necessary, to prevent non-physically high velocities in a region of under determined bedrock depths. Observations from ground penetrating radar of the basal thermal state agree very well with model predictions, while the dip angles of isochrones in radar data also match reasonably well with modelled isochrones, despite the numerical deficiencies of estimating ages with a steady state model. Prognostic runs for 53 years, using a constant accumulation/ablation pattern starting from the steady state solution obtained from the configuration of the 1977 DEM show that: 1 the unrealistic velocities in the under determined parts of the DEM quickly damp out; 2 the free surface evolution matches well measured elevation changes; 3 the retreat of the glacier under this scenario continues with the glacier tongue in a projection to 2030 being situated ≈500 m behind the position in 1977.

scholarly journals Heat transfer in the seabed boundary layer

2021 ◽  
Vol 928 ◽  
Author(s):  
S. Michele ◽  
R. Stuhlmeier ◽  
A.G.L. Borthwick
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Surface ◽  
Surface Waves ◽  
Multiple Scales ◽  
Perturbation Expansion ◽  
Phase Speed ◽  
Maximum Heat ◽  
Practical Applications ◽  
Free Surface Waves

We present a theoretical model of the temperature distribution in the boundary layer region close to the seabed. Using a perturbation expansion, multiple scales and similarity variables, we show how free-surface waves enhance heat transfer between seawater and a seabed with a solid, horizontal, smooth surface. Maximum heat exchange occurs at a fixed frequency depending on ocean depth, and does not increase monotonically with the length and phase speed of propagating free-surface waves. Close agreement is found between predictions by the analytical model and a finite-difference scheme. It is found that free-surface waves can substantially affect the spatial evolution of temperature in the seabed boundary layer. This suggests a need to extend existing models that neglect the effects of a wave field, especially in view of practical applications in engineering and oceanography.

Three-dimensional surfactant-covered flows of thin liquid films on rotating cylinders

2018 ◽  
Vol 844 ◽  
pp. 61-91 ◽  
Author(s):  
Weihua Li ◽  
Satish Kumar
Keyword(s):  
Free Surface ◽  
Flow Visualization ◽  
Evolution Equations ◽  
Thin Liquid Film ◽  
Three Dimensional ◽  
Axial Direction ◽  
Liquid Films ◽  
Practical Applications ◽  
Rotation Rates ◽  
Visualization Experiments

The coating of discrete objects is an important but poorly understood step in the manufacturing of a broad variety of products. An important model problem is the flow of a thin liquid film on a rotating cylinder, where instabilities can arise and compromise coating uniformity. In this work, we use lubrication theory and flow visualization experiments to study the influence of surfactant on these flows. Two coupled evolution equations describing the variation of film thickness and concentration of insoluble surfactant as a function of time, the angular coordinate and the axial coordinate are solved numerically. The results show that surface-tension forces arising from both axial and angular variations in the angular curvature drive flows in the axial direction that tend to smooth out free-surface perturbations and lead to a stable speed window in which axial perturbations do not grow. The presence of surfactant leads to Marangoni stresses that can cause the stable speed window to disappear by driving flow that opposes the stabilizing flow. In addition, Marangoni stresses tend to reduce the spacing between droplets that form at low rotation rates, and reduce the growth rate of rings that form at high rotation rates. Flow visualization experiments yield observations that are qualitatively consistent with predictions from linear stability analysis and the simulation results. The visualizations also indicate that surfactants tend to suppress dripping, slow the development of free-surface perturbations, and reduce the shifting and merging of rings and droplets, allowing more time for solidifying coatings in practical applications.

Three-dimensional coating flow of nematic liquid crystal on an inclined substrate

2015 ◽  
Vol 26 (5) ◽  
pp. 647-669 ◽  
Author(s):  
M. A. LAM ◽  
L. J. CUMMINGS ◽  
T.-S. LIN ◽  
L. KONDIC
Keyword(s):  
Free Surface ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Nonlinear Partial Differential Equation ◽  
Three Dimensional ◽  
Travelling Wave ◽  
Linear Stability Theory ◽  
Newtonian Flow ◽  
Surface Evolution ◽  
Coating Flow

We consider a coating flow of nematic liquid crystal (NLC) fluid film on an inclined substrate. Exploiting the small aspect ratio in the geometry of interest, a fourth-order nonlinear partial differential equation is used to model the free surface evolution. Particular attention is paid to the interplay between the bulk elasticity and the anchoring conditions at the substrate and free surface. Previous results have shown that there exist two-dimensional travelling wave solutions that translate down the substrate. In contrast to the analogous Newtonian flow, such solutions may be unstable to streamwise perturbations. Extending well-known results for Newtonian flow, we analyse the stability of the front with respect to transverse perturbations. Using full numerical simulations, we validate the linear stability theory and present examples of downslope flow of nematic liquid crystal in the presence of both transverse and streamwise instabilities.

scholarly journals A Discrete-Forcing Immersed Boundary Method for Moving Bodies in Air–Water Two-Phase Flows

2020 ◽  
Vol 8 (10) ◽  
pp. 809
Author(s):  
Haixuan Ye ◽  
Yang Chen ◽  
Kevin Maki
Keyword(s):  
Free Surface ◽  
Immersed Boundary Method ◽  
Surface Profile ◽  
Field Extension ◽  
Immersed Boundary ◽  
Two Phase Flows ◽  
Two Phase ◽  
Practical Applications ◽  
Boundary Method ◽  
Immersed Boundaries

For numerical simulations of ship and offshore hydrodynamic problems, it is challenging to model the interaction between the free surface and moving complex geometries. This paper proposes a discrete-forcing immersed boundary method (IBM) to efficiently simulate moving solid boundaries in incompressible air–water two-phase flows. In the present work, the air–water two-phase flows are modeled using the Volume-of-Fluid (VoF) method. The present IBM is suitable for unstructured meshes. It can be used combined with body-fitted wall boundaries to model the relative motions between solid walls, which makes it flexible to use in practical applications. A field extension method is used to model the interaction between the air–water interface and the immersed boundaries. The accuracy of the method is demonstrated through validation cases, including the three-dimensional dam-break problem with an obstacle, the water exit of a circular cylinder, and a ship model advancing with a rotating semi-balanced rudder. The flow field, free-surface profile and force on the immersed boundaries (IBs) are in good agreement with experimental data and other numerical results.

Micro-splashing by drop impacts

2012 ◽  
Vol 706 ◽  
pp. 560-570 ◽  
Author(s):  
S. T. Thoroddsen ◽  
K. Takehara ◽  
T. G. Etoh
Keyword(s):  
Free Surface ◽  
Size Distribution ◽  
Solid Surface ◽  
High Speed ◽  
Solid Substrate ◽  
Liquid Sheet ◽  
Drop Surface ◽  
High Speed Video ◽  
Rain Drops ◽  
Drop Impacts

AbstractWe use ultra-high-speed video imaging to observe directly the earliest onset of prompt splashing when a drop impacts onto a smooth solid surface. We capture the start of the ejecta sheet travelling along the solid substrate and show how it breaks up immediately upon emergence from the underneath the drop. The resulting micro-droplets are much smaller and faster than previously reported and may have gone unobserved owing to their very small size and rapid ejection velocities, which approach 100 m s−1, for typical impact conditions of large rain drops. We propose a phenomenological mechanism which predicts the velocity and size distribution of the resulting microdroplets. We also observe azimuthal undulations which may help promote the earliest breakup of the ejecta. This instability occurs in the cusp in the free surface where the drop surface meets the radially ejected liquid sheet.

Modeling the sloshing problem in a rectangular tank with submerged incomplete baffles

2016 ◽  
Vol 26 (3/4) ◽  
pp. 722-744 ◽  
Author(s):  
Marcela A. Cruchaga ◽  
Carlos Ferrada ◽  
Nicolás Márquez ◽  
Sebastián Osses ◽  
Mario Storti ◽  
...  
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Wave Height ◽  
Numerical Study ◽  
Free Surface Flows ◽  
Numerical Results ◽  
Surface Evolution ◽  
Content Type ◽  
Near Resonance ◽  
Wave Heights

Purpose – The present work is an experimental and numerical study of a sloshing problem including baffle effects. The purpose of this paper is to assess the numerical behavior of a Lagrangian technique to track free surface flows by comparison with experiments, to report experimental data for sloshing at different conditions and to evaluate the effectiveness of baffles in limiting the wave height and the wave propagation. Design/methodology/approach – Finite element simulations performed with a fixed mesh technique able to describe the free surface evolution are contrasted with experimental data. The experiments consist of an acrylic tank of rectangular section designed to attach baffles of different sizes at different distance from the bottom. The tank is filled with water and mounted on a shake table able to move under controlled horizontal motion. The free surface evolution is measured with ultrasonic sensors. The numerical results computed for different sloshing conditions are compared with the experimental data. Findings – The reported numerical results are in general in good agreement with the experiments. In particular, wave heights and frequencies response satisfactorily compared with the experimental data for the several cases analyzed during steady state forced sloshing and free sloshing. The effectiveness of the baffles increases near resonance conditions. From the set of experiments studied, the major reduction of the wave height was obtained when larger baffles were positioned closer to the water level at rest. Practical implications – Model validation: evaluation of the effectiveness of non-massive immersed baffles during sloshing. Originality/value – The value of the present work encompass the numerical and experimental study of the effect of immersed baffles during sloshing under different imposed conditions and the comparison of numerical results with the experimental data. Also, the results shown in the present work are a contribution to the understanding of the role in the analysis of the proposed problem of some specific aspects of the geometry and the imposed motion.

An analysis of 2D and 3D multiple attenuation for a canonical example

Geophysics ◽  
2005 ◽  
Vol 70 (6) ◽  
pp. A13-A28 ◽  
Author(s):  
Luc T. Ikelle
Keyword(s):  
Free Surface ◽  
Inverse Scattering ◽  
Three Dimensional ◽  
Homogeneous Medium ◽  
Vertical Plane ◽  
Multiple Attenuation ◽  
Out Of Plane ◽  
Seismic Acquisition ◽  
2D And 3D ◽  
The Relationship

Three-dimensional formulations of free-surface multiple attenuation for multioffset seismic data are well known. They are not yet used in practice because they require very dense source-receiver coverage, which is still out of reach with existing seismic-acquisition systems. The development of alternative solutions based on 2D algorithms depends on our understanding of the relationship between 2D and 3D free-surface multiple-attenuation methods. This paper attempts to enhance this understanding by establishing the relationship between 2D and 3D inverse scattering free-surface multiple attenuation. A 3D model consisting of three scattering points (one scattered point located in the vertical plane containing the shooting line and the other two points outside this plane) in a homogeneous medium (for which the exact pressure field is analytically known) is used to show that the 2D inverse scattering multiple-attenuation algorithm predicts all free-surface multiples as does its 3D counterpart but with some traveltime and amplitude errors. One implication of this result is that the current 2D inverse scattering multiple-attenuation algorithm, with an appropriate 2D-to-3D correction, can be used to predict the free-surface multiples for data containing out-of-plane scattering.

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