scholarly journals Towards an Acoustic Simulation of a Water Drop Impacting in a Water Pool

2020 ◽  
Vol 105 (4) ◽  
pp. 1231-1247
Author(s):  
Jonas Friedrich ◽  
Michael Schäfer
Keyword(s):  
Multiphase Flow ◽  
Water Drop ◽  
Surface Force ◽  
Significant Rise ◽  
Test Case ◽  
Force Model ◽  
Water Pool ◽  
Linearized Euler Equations ◽  
Physical Mechanisms ◽  
Drop Impacts

AbstractThe sound which is produced when a water drop impacts into a water pool is a prominent example for acoustics produced by multiphase flow. In this work the feasibility of numerical methods for simulating this challenging test case is evaluated. First the multiphase flow needs to produce the correct physical mechanisms, e.g. the bubble entrapment. For this an in-house block-structured finite-volume solver with the volume-of-fluid method is used. For the curvature computation a standard finite difference method within the continuum surface force model is employed, including some necessary improvements. A high resolution in space and time is essential and therefore the method is parallelized by domain decomposition. The acoustic part is simulated with the linearized Euler equations which are valid in each phase but need to be adapted in the interface region. The results are compared with numerical and experimental data. It is shown, that the methods are suitable for simple test cases. A coupled drop impact test case corresponds with equivalent experiments until the drop detachment. The acoustic pressure shows a significant rise in the vicinity of the bubble detachment within both phases. However, an oscillation of the cavity bottom can not be observed in the multiphase neither in the acoustic outputs of the airborne signal.

scholarly journals Enhanced discrete phase model for multiphase flow simulation of blood flow with high shear stress

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042110080
Author(s):  
Zheqin Yu ◽  
Jianping Tan ◽  
Shuai Wang
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Multiphase Flow ◽  
Experimental Verification ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Phase Model ◽  
Force Model ◽  
Discrete Phase Model ◽  
Discrete Phase

Shear stress is often present in the blood flow within blood-contacting devices, which is the leading cause of hemolysis. However, the simulation method for blood flow with shear stress is still not perfect, especially the multiphase flow model and experimental verification. In this regard, this study proposes an enhanced discrete phase model for multiphase flow simulation of blood flow with shear stress. This simulation is based on the discrete phase model (DPM). According to the multiphase flow characteristics of blood, a virtual mass force model and a pressure gradient influence model are added to the calculation of cell particle motion. In the experimental verification, nozzle models were designed to simulate the flow with shear stress, varying the degree of shear stress through different nozzle sizes. The microscopic flow was measured by the Particle Image Velocimetry (PIV) experimental method. The comparison of the turbulence models and the verification of the simulation accuracy were carried out based on the experimental results. The result demonstrates that the simulation effect of the SST k- ω model is better than other standard turbulence models. Accuracy analysis proves that the simulation results are accurate and can capture the movement of cell-level particles in the flow with shear stress. The results of the research are conducive to obtaining accurate and comprehensive analysis results in the equipment development phase.

scholarly journals Comparison of Surface Tension Models for the Volume of Fluid Method

Processes ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 542 ◽  
Author(s):  
Kurian J. Vachaparambil ◽  
Kristian Etienne Einarsrud
Keyword(s):  
Surface Tension ◽  
Multiphase Flow ◽  
Capillary Rise ◽  
Surface Tension Force ◽  
Surface Force ◽  
Parallel Plates ◽  
Time Step ◽  
Mesh Resolution ◽  
Active Research ◽  
Spurious Currents

With the increasing use of Computational Fluid Dynamics to investigate multiphase flow scenarios, modelling surface tension effects has been a topic of active research. A well known associated problem is the generation of spurious velocities (or currents), arising due to inaccuracies in calculations of the surface tension force. These spurious currents cause nonphysical flows which can adversely affect the predictive capability of these simulations. In this paper, we implement the Continuum Surface Force (CSF), Smoothed CSF and Sharp Surface Force (SSF) models in OpenFOAM. The models were validated for various multiphase flow scenarios for Capillary numbers of 10 − 3 –10. All the surface tension models provide reasonable agreement with benchmarking data for rising bubble simulations. Both CSF and SSF models successfully predicted the capillary rise between two parallel plates, but Smoothed CSF could not provide reliable results. The evolution of spurious current were studied for millimetre-sized stationary bubbles. The results shows that SSF and CSF models generate the least and most spurious currents, respectively. We also show that maximum time step, mesh resolution and the under-relaxation factor used in the simulations affect the magnitude of spurious currents.

Numerical Simulation of Interior Flow in Evaporation Droplet

2014 ◽  
Author(s):  
Qingming Dong ◽  
Zhentao Wang ◽  
Yonghui Zhang ◽  
Junfeng Wang
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Internal Flow ◽  
Surface Force ◽  
Droplet Surface ◽  
Force Model ◽  
Marangoni Flow ◽  
High Temperature Area ◽  
Interior Flow ◽  
Temperature Area

In this present study, the VOF (Volume of Fluid) approach is adopted to capture the interface, and CSF (Continuum Surface Force) model to calculate the surface tension, and the governing equations are founded in numerical simulation of evaporating droplets. In this work, a water droplet is assumed to be suspending in high temperature air, and the gravity of a droplet is ignored. During evaporating process of the droplet, the internal circulation flow will be induced due to the gradient of temperature at the droplet surface. The interface flows from high temperature area to low temperature area, which pulls the liquid to produce convective flow inside the droplet called as Marangoni flow. Marangoni flow makes the temperature distribution tend to uniformity, which enhances heat transfer but weakens Marangoni flow in turn. So, during droplet evaporation, the internal flow is not steady.

scholarly journals Body-force modeling for aerodynamic analysis of air intake – fan interactions

2016 ◽  
Vol 26 (7) ◽  
pp. 2048-2065 ◽  
Author(s):  
William Thollet ◽  
Guillaume Dufour ◽  
Xavier Carbonneau ◽  
Florian Blanc
Keyword(s):  
Body Force ◽  
Stokes Equations ◽  
The Body ◽  
Test Case ◽  
Force Model ◽  
Strong Impact ◽  
Analytic Model ◽  
Source Terms ◽  
Content Type ◽  
Air Intake

Purpose The purpose of this paper is to explore a methodology that allows to represent turbomachinery rotating parts by replacing the blades with a body force field. The objective is to capture interactions between a fan and an air intake at reduced cost, as compared to full annulus unsteady computations. Design/methodology/approach The blade effects on the flow are taken into account by adding source terms to the Navier-Stokes equations. These source terms give the proper amount of flow turning, entropy, and blockage to the flow. Two different approaches are compared: the source terms can be computed using an analytic model, or they can directly be extracted from RANS computations with the blade’s geometry. Findings The methodology is first applied to an isolated rotor test case, which allows to show that blockage effects have a strong impact on the performance of the rotor. It is also found that the analytic body force model underestimates the mass flow in the blade row for choked conditions. Finally, the body force approach is used to capture the coupling between a fan and an air intake at high angle of attacks. A comparison with full annulus unsteady computations shows that the model adequately captures the potential effects of the fan on the air intake. Originality/value To the authors’ knowledge, it is the first time that the analytic model used in this paper is combined with the blockage source terms. Furthermore, the capability of the model to deal with flows in choked conditions was never assessed.

Optimisation of Manufacturing Process Models via Intelligent Water Drop Algorithm

2012 ◽  
Vol 217-219 ◽  
pp. 1501-1505
Author(s):  
Pongchanun Luangpaiboon
Keyword(s):  
Water Drop ◽  
Cutting Speed ◽  
Process Models ◽  
Depth Of Cut ◽  
Force Model ◽  
Machining Parameters ◽  
Rough Machining ◽  
Convex Model ◽  
Turning Operation ◽  
Spring Force

In this paper, an intelligent water drop algorithm or IWD has been developed to optimise machining parameters in turning operation including a spring force model. Firstly, machining conditions are to minimise the production cost in conventional manufacturing processes. Several passes of rough machining are started on the turning operation with a final pass of a finishing. Various constraints are considered in each non-linear and non-convex model. The machining parameters in the turning consist of the depth of cut, cutting speed and feed. Finally, in a specialised manufacturing application on the spring force problem, an achievement of a specific goal may be the primary objective subject to some process parameter ranges. The computational results clearly showed that the proposed sequential procedures of the IWD have considerably improved the objective functions.

Numerical Methods for Tracking Interfaces With Surface Tension in 3-D Mold Filling Processes

2002 ◽  
Author(s):  
Matthew W. Williams ◽  
Doug Kothe ◽  
Deniece Korzekwa ◽  
Phil Tubesing
Keyword(s):  
Surface Tension ◽  
Weber Number ◽  
Three Dimensional ◽  
Surface Force ◽  
Qualitative Behavior ◽  
Force Model ◽  
Simulation Tool ◽  
Software Simulation ◽  
Number Problem ◽  
Asymmetric Top

Gravity-pour casting processes are simulated for both low and high Weber number flows. The validation problems examined are a symmetric side-fill problem and a more complex asymmetric top-fill problem with flow over and obstacle. A recently developed continuum surface force model was implemented within a transient three-dimensional software simulation tool and applied to the low Weber number problem. The resulting simulations are compared with experiments that were conducted in order to validate current and future gravity-pour casting simulations. The simulations are found to capture much of the qualitative behavior of the complex three-dimensional flows.

Surface Tension Capability Within an Adaptively Refined Compressible Flow Code

2017 ◽  
Author(s):  
Z. Jibben ◽  
J. Velechovsky ◽  
T. Masser ◽  
M. Francois
Keyword(s):  
Surface Tension ◽  
Compressible Flow ◽  
Piecewise Linear ◽  
Surface Force ◽  
Force Model ◽  
Material Interface ◽  
Flow Solver ◽  
Interface Reconstruction ◽  
Volume Method ◽  
Inviscid Compressible Flow

We present a method to simulate surface tension between immiscible materials within an inviscid compressible flow solver. The material interface is represented using the volume of fluid technique with piecewise-linear interface reconstruction. We employ the continuum surface force model for surface tension, implemented in the context of the MUSCL-Hancock finite volume method for the Euler equations on an adaptively refined Eulerian mesh. We show results for droplet verification test cases.

scholarly journals Fifth fundamental force and unification of fundamental forces

2021 ◽  
Author(s):  
Raghvendra Singh
Keyword(s):  
Water Drop ◽  
Surface Force ◽  
Adhesive Force ◽  
The Other ◽  
Unified Theory ◽  
Fifth Force ◽  
Functional Forms ◽  
Fundamental Forces ◽  
The Universe ◽  
Adhesive Forces

Abstract There are four known fundamental forces of nature and there is a need to combine them into a unified theory. Progress has been made toward this goal but gravity remains an issue. However, the four forces are body forces that act on points. They together do not make the universe a closed system. Here, I identify a surface force, which acts outward normal to the surface of the universe. Further, using water drop hanging in a vacuum as a model, I provide a formula to find the magnitude of this force. The fifth force is generated by the surface tension, a property of dark energy. On the other hand, matter particles interact with each other through a cohesive force and with dark matter through an adhesive force. I give a range of the functional forms of all cohesive and adhesive forces and present an equation that unifies all the forces of nature.

scholarly journals Fifth fundamental force and unification of fundamental forces

2021 ◽  
Author(s):  
Raghvendra Singh
Keyword(s):  
Water Drop ◽  
Surface Force ◽  
The Other ◽  
Unified Theory ◽  
Fifth Force ◽  
Cohesive Forces ◽  
Functional Forms ◽  
Fundamental Forces ◽  
The Universe ◽  
Adhesive Forces

Abstract There are four known fundamental forces of nature and there is a need to combine them into a unified theory. Progress has been made toward this goal but gravity remains an issue. However, the four forces are body forces that act on points. They together do not make the universe a closed system. Here, I identify a surface force, which acts outward normal to the surface of the universe. Further, using water drop hanging in a vacuum as a model, I provide a formula to find the magnitude of this force. The fifth force is generated by surface tension, a property of dark energy. On the other hand, matter particles interact with each other through cohesive forces and with dark matter through adhesive forces. I give a range of functional forms of all cohesive and adhesive forces and present an equation that unifies all the forces of nature.

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