Application of an Improved Ghost Fluid Method to the Collapse of Non-Spherical Bubbles in a Compressible Liquid

2011 ◽  
Author(s):  
Hiroyuki Takahira ◽  
Yoshinori Jinbo
Keyword(s):  
Surface Tension ◽  
Shock Waves ◽  
Thermal Diffusion ◽  
Level Set ◽  
Compressible Liquid ◽  
Maximum Temperature ◽  
Bubble Collapse ◽  
Ghost Fluid Method ◽  
Toroidal Bubble ◽  
The Impact

The ghost fluid method (GFM) is improved to investigate violent bubble collapse in a compressible liquid, in which the adaptive mesh refinement with multigrids, the surface tension, and the thermal diffusion through the bubble interface are taken into account. The improved multigrid GFM is applied to the interaction of an incident shock wave with a bubble. The multigrid GFM captures the fine interfacial and vortex structures of the toroidal bubble when the bubble collapses violently accompanied with the penetration of the liquid jet and the formation of the shock waves. The multigrid GFM is also applied to the bubble collapse near a tissue surface in which the tissue is modeled with gelatin in order to predict the tissue damage due to the bubble collapse; the motions of three phases for the gas inside the bubble, the liquid surrounding the bubble, and the gelatin boundary are solved directly by coupling the level set method with the improved GFM. Two kinds of level set functions are utilized for distinguishing the gas-liquid interface from the liquid-gelatin interface. It is shown that the impact of the shock waves generated from the collapsing bubble on the boundary leads to the formation of depression of the boundary; the toroidal bubble penetrates into the depression. Also, the surface tension effects are successfully included in the improved GFM. The thermal effects of internal gas on the bubble collapse are also discussed by considering the thermal diffusion across the interface in the GFM. The thermal boundary layers of the toroidal bubble are captured with the method. The result shows that the smaller the initial bubble radius becomes, the lower the maximum temperature inside the bubble becomes because of the thermal diffusion across the interface.

Numerical Investigations of Thermal Effects on the Interaction of Shock Waves With Bubbles

2011 ◽  
Author(s):  
Yoshinori Jinbo ◽  
Hiroyuki Takahira
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Thermal Diffusion ◽  
Bubble Radius ◽  
Strong Shock ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Compressible Liquid ◽  
Bubble Collapse ◽  
Spherical Bubble

The present study deals with the collapse of nonspherical bubbles in a compressible liquid by taking the thermal diffusion into account. The ghost fluid method (GFM) is modified so as to consider the thermal diffusion through the bubble surface. The boundary condition for the temperature continuity at the interface is discussed for determining the values of the ghost fluids. The improved GFM is applied to the collapse of a single spherical bubble. The present results are in good agreement with those obtained from the equation of motion for a single bubble (Keller equation) coupling with the energy equation. The improved multigrid GFM is also applied to the interaction of a gas bubble with a strong shock wave. The non-spherical bubble collapse is simulated successfully by taking the thermal diffusion into account. The thermal boundary layers both inside and outside the bubble are captured with the present method although the thermal boundary layer in liquid is very thin. The bubble collapse due to the incident shock wave accompanies the formation of the liquid jets and shock waves leading to the high temperature field. The influence of thermal diffusion becomes more prominent when the initial bubble radius is small. It is shown that a large amount of heat outflows from the interior of the bubble to the liquid when the liquid jet hits the downstream surface of the bubble and the bubble rebounds. The increased thermal diffusion causes the decrease of the internal pressure and temperature in the bubble leading to more violent collapse.

Cavitation Bubble Collapse in Viscous, Compressible Liquids—Numerical Analysis

1965 ◽  
Vol 87 (4) ◽  
pp. 977-985 ◽  
Author(s):  
R. D. Ivany ◽  
F. G. Hammitt
Keyword(s):  
Surface Tension ◽  
High Pressures ◽  
Numerical Solutions ◽  
Compressible Liquid ◽  
Navier Stokes ◽  
Bubble Collapse ◽  
Navier Stokes Equation ◽  
Scaling Parameters ◽  
Collapse Behavior ◽  
Normalized Solution

Collapse of a spherical bubble in a compressible liquid, including the effects of surface tension, viscosity, and an adiabatic compression of gas within the bubble is investigated by numerical solutions of the hydrodynamic equations. A limiting value of shear viscosity causes the bubble collapse to slow down markedly, for both compressible and incompressible liquids, whereas moderate viscosities have very little effect on the rate of collapse. The inclusion of surface tension and viscosity introduces two scaling parameters into the solution, so that a single normalized solution is no longer sufficient to describe collapse behavior. The magnitude of the density changes calculated for the compressible liquid and the extremely rapid changes with time suggest that the usual Navier-Stokes equation of motion may not be appropriate. The possibility of liquid relaxational phenomenon and its contribution to sonoluminescence is considered. Shock waves or damagingly high pressures are not generated during collapse at a distance in the liquid equal to the initial radius from the center of collapse, although they will appear at such a distance if the bubble rebounds.

scholarly journals Buoyancy control in ammonoid cephalopods refined by complex internal shell architecture

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
David J. Peterman ◽  
Kathleen A. Ritterbush ◽  
Charles N. Ciampaglio ◽  
Erynn H. Johnson ◽  
Shinya Inoue ◽  
...  
Keyword(s):  
Surface Tension ◽  
Water Retention Capacity ◽  
Functional Explanation ◽  
Retention Capacity ◽  
Biomechanical Stress ◽  
Liquid Retention ◽  
3D Printed ◽  
Functional Explanations ◽  
Hydrophilic Coatings ◽  
The Impact

AbstractThe internal architecture of chambered ammonoid conchs profoundly increased in complexity through geologic time, but the adaptive value of these structures is disputed. Specifically, these cephalopods developed fractal-like folds along the edges of their internal divider walls (septa). Traditionally, functional explanations for septal complexity have largely focused on biomechanical stress resistance. However, the impact of these structures on buoyancy manipulation deserves fresh scrutiny. We propose increased septal complexity conveyed comparable shifts in fluid retention capacity within each chamber. We test this interpretation by measuring the liquid retained by septa, and within entire chambers, in several 3D-printed cephalopod shell archetypes, treated with (and without) biomimetic hydrophilic coatings. Results show that surface tension regulates water retention capacity in the chambers, which positively scales with septal complexity and membrane capillarity, and negatively scales with size. A greater capacity for liquid retention in ammonoids may have improved buoyancy regulation, or compensated for mass changes during life. Increased liquid retention in our experiments demonstrate an increase in areas of greater surface tension potential, supporting improved chamber refilling. These findings support interpretations that ammonoids with complex sutures may have had more active buoyancy regulation compared to other groups of ectocochleate cephalopods. Overall, the relationship between septal complexity and liquid retention capacity through surface tension presents a robust yet simple functional explanation for the mechanisms driving this global biotic pattern.

scholarly journals Social media reveal ecoregional variation in how weather influences visitor behavior in U.S. National Park Service units

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Emily J. Wilkins ◽  
Peter D. Howe ◽  
Jordan W. Smith
Keyword(s):  
National Park ◽  
National Park Service ◽  
Spatial Behavior ◽  
Maximum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
Daily Weather ◽  
Visitor Behavior ◽  
Park Service ◽  
The Impact

AbstractDaily weather affects total visitation to parks and protected areas, as well as visitors’ experiences. However, it is unknown if and how visitors change their spatial behavior within a park due to daily weather conditions. We investigated the impact of daily maximum temperature and precipitation on summer visitation patterns within 110 U.S. National Park Service units. We connected 489,061 geotagged Flickr photos to daily weather, as well as visitors’ elevation and distance to amenities (i.e., roads, waterbodies, parking areas, and buildings). We compared visitor behavior on cold, average, and hot days, and on days with precipitation compared to days without precipitation, across fourteen ecoregions within the continental U.S. Our results suggest daily weather impacts where visitors go within parks, and the effect of weather differs substantially by ecoregion. In most ecoregions, visitors stayed closer to infrastructure on rainy days. Temperature also affects visitors’ spatial behavior within parks, but there was not a consistent trend across ecoregions. Importantly, parks in some ecoregions contain more microclimates than others, which may allow visitors to adapt to unfavorable conditions. These findings suggest visitors’ spatial behavior in parks may change in the future due to the increasing frequency of hot summer days.

scholarly journals The impact of climate change in wheat and barley yields in the Iberian Peninsula

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Virgílio A. Bento ◽  
Andreia F. S. Ribeiro ◽  
Ana Russo ◽  
Célia M. Gouveia ◽  
Rita M. Cardoso ◽  
...  
Keyword(s):  
Climate Change ◽  
Iberian Peninsula ◽  
Climate Model ◽  
Global Climate Models ◽  
Maximum Temperature ◽  
Historical Period ◽  
Early Winter ◽  
Impact Of Climate Change ◽  
The Impact ◽  
Spring Maximum

AbstractThe impact of climate change on wheat and barley yields in two regions of the Iberian Peninsula is here examined. Regression models are developed by using EURO-CORDEX regional climate model (RCM) simulations, forced by ERA-Interim, with monthly maximum and minimum air temperatures and monthly accumulated precipitation as predictors. Additionally, RCM simulations forced by different global climate models for the historical period (1972–2000) and mid-of-century (2042–2070; under the two emission scenarios RCP4.5 and RCP8.5) are analysed. Results point to different regional responses of wheat and barley. In the southernmost regions, results indicate that the main yield driver is spring maximum temperature, while further north a larger dependence on spring precipitation and early winter maximum temperature is observed. Climate change seems to induce severe yield losses in the southern region, mainly due to an increase in spring maximum temperature. On the contrary, a yield increase is projected in the northern regions, with the main driver being early winter warming that stimulates earlier growth. These results warn on the need to implement sustainable agriculture policies, and on the necessity of regional adaptation strategies.

Experimental study of heat transfer in the boundary layer of a flat plate with the impact of weak shock waves on the leading edge

2020 ◽  
Author(s):  
V. L. Kocharin ◽  
A. A. Yatskikh ◽  
D. S. Prishchepova ◽  
A. V. Panina ◽  
Yu. G. Yermolaev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Experimental Study ◽  
Shock Waves ◽  
Flat Plate ◽  
Leading Edge ◽  
Weak Shock ◽  
The Impact

scholarly journals Analysis of the Accelerator-Driven System Fuel Assembly during the Steam Generator Tube Rupture Accident

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1818
Author(s):  
Di-Si Wang ◽  
Bo Liu ◽  
Sheng Yang ◽  
Bin Xi ◽  
Long Gu ◽  
...  
Keyword(s):  
Fuel Assembly ◽  
Steam Generator ◽  
Metal Flow ◽  
Maximum Temperature ◽  
Steam Generator Tube ◽  
Driven System ◽  
Fuel Assemblies ◽  
Accelerator Driven System ◽  
The Impact ◽  
Steam Bubble

China is developing an ADS (Accelerator-Driven System) research device named the China initiative accelerator-driven system (CiADS). When performing a safety analysis of this new proposed design, the core behavior during the steam generator tube rupture (SGTR) accident has to be investigated. The purpose of our research in this paper is to investigate the impact from different heating conditions and inlet steam contents on steam bubble and coolant temperature distributions in ADS fuel assemblies during a postulated SGTR accident by performing necessary computational fluid dynamics (CFD) simulations. In this research, the open source CFD calculation software OpenFOAM, together with the two-phase VOF (Volume of Fluid) model were used to simulate the steam bubble behavior in heavy liquid metal flow. The model was validated with experimental results published in the open literature. Based on our simulation results, it can be noticed that steam bubbles will accumulate at the periphery region of fuel assemblies, and the maximum temperature in fuel assembly will not overwhelm its working limit during the postulated SGTR accident when the steam content at assembly inlet is less than 15%.

Evaluation the effect of the ambient temperature on the liquid petroleum gas transportation pipeline

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ammar Ali Abd ◽  
Samah Zaki Naji ◽  
Ching Thian Tye ◽  
Mohd Roslee Othman
Keyword(s):  
Energy Consumption ◽  
Greenhouse Gases ◽  
Ambient Temperature ◽  
Phase Change ◽  
Liquid State ◽  
Pump Energy ◽  
Compressible Liquid ◽  
Liquefied Petroleum Gas ◽  
Efficient Design ◽  
The Impact

Abstract Liquefied petroleum gas (LPG) plays a major role in worldwide energy consumption as a clean source of energy with low greenhouse gases emission. LPG transportation is exhibited through networks of pipelines, maritime, and tracks. LPG transmission using pipeline is environmentally friendly owing to the low greenhouse gases emission and low energy requirements. This work is a comprehensive evaluation of transportation petroleum gas in liquid state and compressible liquid state concerning LPG density, temperature and pressure, flow velocity, and pump energy consumption under the impact of different ambient temperatures. Inevitably, the pipeline surface exchanges heat between LPG and surrounding soil owing to the temperature difference and change in elevation. To prevent phase change, it is important to pay attention for several parameters such as ambient temperature, thermal conductivity of pipeline materials, soil type, and change in elevation for safe, reliable, and economic transportation. Transporting LPG at high pressure requests smaller pipeline size and consumes less energy for pumps due to its higher density. Also, LPG transportation under moderate or low pressure is more likely exposed to phase change, thus more thermal insulation and pressure boosting stations required to maintain the phase envelope. The models developed in this work aim to advance the existing knowledge and serve as a guide for efficient design by underling the importance of the mentioned parameters.

scholarly journals A Low Mach Number IMEX Flux Splitting for the Level Set Ghost Fluid Method

2021 ◽  
Author(s):  
Jonas Zeifang ◽  
Andrea Beck
Keyword(s):  
Level Set ◽  
Phase Interface ◽  
Time Discretization ◽  
Spectral Element ◽  
Computational Time ◽  
Minor Role ◽  
Ghost Fluid Method ◽  
Specific Level ◽  
Flux Splitting ◽  
Mach Numbers

AbstractConsidering droplet phenomena at low Mach numbers, large differences in the magnitude of the occurring characteristic waves are presented. As acoustic phenomena often play a minor role in such applications, classical explicit schemes which resolve these waves suffer from a very restrictive timestep restriction. In this work, a novel scheme based on a specific level set ghost fluid method and an implicit-explicit (IMEX) flux splitting is proposed to overcome this timestep restriction. A fully implicit narrow band around the sharp phase interface is combined with a splitting of the convective and acoustic phenomena away from the interface. In this part of the domain, the IMEX Runge-Kutta time discretization and the high order discontinuous Galerkin spectral element method are applied to achieve high accuracies in the bulk phases. It is shown that for low Mach numbers a significant gain in computational time can be achieved compared to a fully explicit method. Applications to typical droplet dynamic phenomena validate the proposed method and illustrate its capabilities.

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