scholarly journals Effect on Richtmyer-Meshkov instability of deviation from sinusoidality of the corrugated interface between two fluids

2007 ◽  
Vol 25 (3) ◽  
pp. 503-510 ◽  
Author(s):  
M.R. Gupta ◽  
S. Roy ◽  
S. Sarkar ◽  
M. Khan ◽  
H.C. Pant ◽  
...  
Keyword(s):  
Growth Rate ◽  
Laser Pulse ◽  
Geometrical Shape ◽  
Fluid Interface ◽  
Two Fluids ◽  
Optimum Stability ◽  
Geometrical Shapes ◽  
Icf Target ◽  
Two Fluid ◽  
Arbitrary Shapes

The effect of arbitrary shapes of the two fluid interface on Richtmyer-Meshkov (RM) instability is investigated. It is seen that deviation from sinusoidality in the geometrical shapes has interesting influence on the overall growth rate. In the linear theoretic domain the RM instability may be actually reduced for suitable geometrical shape of the interface. The figures given demonstrate this aspect. This result is important in designing ICF target and also gives an idea to tailor laser pulse for optimum stability of RM modes.

A moving fluid interface. Part 2. The removal of the force singularity by a slip flow

1977 ◽  
Vol 79 (2) ◽  
pp. 209-229 ◽  
Author(s):  
L. M. Hocking
Keyword(s):  
Contact Line ◽  
Slip Flow ◽  
Slip Condition ◽  
Solid Boundary ◽  
Parallel Plates ◽  
Fluid Interface ◽  
Slip Coefficient ◽  
Outer Flow ◽  
Normal Contact ◽  
Two Fluids

If the no-slip condition is used to determine the flow produced when a fluid interface moves along a solid boundary, a non-integrable stress is obtained. In part 1 of this study (Hocking 1976), it was argued that, when allowance was made for the presence of irregularities on the solid boundary, an effective slip coefficient could be found, which might remove the difficulty.This paper examines the effect of a slip coefficient on the flow in the neighbourhood of the contact line. Particular cases which are solved in detail are liquid–gas interfaces at an arbitrary angle, and normal contact of fluids of arbitrary viscosity. The contribution of the vicinity of the contact line to the force on the boundary is obtained.The inner region, near the contact line, must be matched with an outer flow, in which the no-slip condition can be applied, in order to obtain the total value of the force on the boundary. This force is determined for the flow of two fluids between parallel plates and in a pipe, with a plane interface. The enhanced resistance produced by the presence of the interface is calculated, and it is shown to be equivalent to an increase in the length of the column of fluid by a small multiple of the pipe radius.

scholarly journals Topology design of two-fluid heat exchange

2020 ◽  
Author(s):  
Hiroki Kobayashi ◽  
Kentaro Yaji ◽  
Shintaro Yamasaki ◽  
Kikuo Fujita
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Transfer Rate ◽  
Design Variable ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Maximum Heat ◽  
Variable Field ◽  
Two Fluids ◽  
Two Fluid

Abstract Heat exchangers are devices that typically transfer heat between two fluids. The performance of a heat exchanger such as heat transfer rate and pressure loss strongly depends on the flow regime in the heat transfer system. In this paper, we present a density-based topology optimization method for a two-fluid heat exchange system, which achieves a maximum heat transfer rate under fixed pressure loss. We propose a representation model accounting for three states, i.e., two fluids and a solid wall between the two fluids, by using a single design variable field. The key aspect of the proposed model is that mixing of the two fluids can be essentially prevented. This is because the solid constantly exists between the two fluids due to the use of the single design variable field. We demonstrate the effectiveness of the proposed method through three-dimensional numerical examples in which an optimized design is compared with a simple reference design, and the effects of design conditions (i.e., Reynolds number, Prandtl number, design domain size, and flow arrangements) are investigated.

scholarly journals Geometrical form assessment of a CFD based breathing thermal manikins, designed by simplified polygonal shapes

2019 ◽  
Vol 85 ◽  
pp. 02002
Author(s):  
Martin Ivanov ◽  
Sergey Mijorski
Keyword(s):  
Flow Characteristics ◽  
Temperature Fields ◽  
Geometrical Shape ◽  
Thermal Plume ◽  
Flow Acceleration ◽  
Geometrical Shapes ◽  
Geometrical Form ◽  
The Difference ◽  
High Degree ◽  
Positive Effect

The presented paper focuses on a CFD based analyses of the complexity in the geometrical shape of the breathing thermal manikins, associated with their main functionalities. Both impacts of the external manikin’s form were studied – over the velocity and over the temperature fields in the thermal plume zone above the head. Three different geometrical shapes are analysed – a physiologically identified (called Humanoid Manikin) and two other shapes, designed to match the overall 95th percentile of the anthropometric size of the standard person (called Polygonal Manikins). The first model represents a comprehensive multifaceted figure of a manikin with high degree of physiological identity with a female human being. The second and third one, are simplified, but still with anatomically realistic component forms, accurately representing the anthropometric size of a standard person. The difference between them is in the presence of additional flow optimization collars in the third model. The numerical results demonstrate the clear impact of the manikins’ geometrical characteristics over the simulated breathing and convective flows. The optimization with the proposed collars had a positive effect over the resulted flow acceleration at top head and chest zones. However, the improvement of the flow characteristics was observed for two of the simulated three breathing phases and further shape optimization is required.

scholarly journals Simulation of Free Surface Compressible Flows via a Two Fluid Model

2008 ◽  
Author(s):  
Fre´de´ric Dias ◽  
Denys Dutykh ◽  
Jean-Michel Ghidaglia
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Compressible Flows ◽  
Fluid Model ◽  
Three Dimensional ◽  
Two Fluids ◽  
Equation Of States ◽  
Two Fluid Model ◽  
Velocity Pressure ◽  
Two Fluid

The purpose of this communication is to discuss the simulation of a free surface compressible flow between two fluids, typically air and water. We use a two fluid model with the same velocity, pressure and temperature for both phases. In such a numerical model, the free surface becomes a thin three dimensional zone. The present method has at least three advantages: (i) the free-surface treatment is completely implicit; (ii) it can naturally handle wave breaking and other topological changes in the flow; (iii) one can easily vary the Equation of States (EOS) of each fluid (in principle, one can even consider tabulated EOS). Moreover, our model is unconditionally hyperbolic for reasonable EOS.

Transmission and reflection of a real sound beam at a two‐fluid interface

1989 ◽  
Vol 85 (S1) ◽  
pp. S93-S93
Author(s):  
Jacqueline Naze Tjøtta ◽  
Hans‐Christen Salvesen ◽  
Sigve Tjøtta
Keyword(s):  
Fluid Interface ◽  
Sound Beam ◽  
Two Fluid ◽  
Transmission And Reflection

scholarly journals Global Existence and Asymptotic Behavior of Solutions for Compressible Two-Fluid Euler–Maxwell Equation

2020 ◽  
Vol 2020 ◽  
pp. 1-27
Author(s):  
Ismahan Binshati ◽  
Harumi Hattori
Keyword(s):  
Asymptotic Behavior ◽  
Fourier Transform ◽  
Global Existence ◽  
Maxwell Equations ◽  
Decay Rates ◽  
Asymptotic Behavior Of Solutions ◽  
Two Fluids ◽  
The Fourier Transform ◽  
Rates Of Decay ◽  
Two Fluid

We study the global existence and asymptotic behavior of the solutions for two-fluid compressible isentropic Euler–Maxwell equations by the Fourier transform and energy method. We discuss the case when the pressure for two fluids is not identical, and we also add friction between the two fluids. In addition, we discuss the rates of decay of Lp−Lq norms for a linear system. Moreover, we use the result for Lp−Lq estimates to prove the decay rates for the nonlinear systems.

scholarly journals Aspects concerning the influence of the design of flameproof electric motors on maximum explosion pressures

2020 ◽  
Vol 305 ◽  
pp. 00008
Author(s):  
Mihai Magyari ◽  
Lucian Moldovan ◽  
Diana Sălăşan
Keyword(s):  
High Pressure ◽  
Petrochemical Industry ◽  
Mine Safety ◽  
Geometrical Shape ◽  
Electric Motors ◽  
Geometrical Shapes ◽  
Explosion Protection ◽  
Internal Volume ◽  
Large Motor ◽  
Internal Arrangement

The research carried out in the specialized Laboratory of the National Institute for Research and Development in Mine Safety and Explosion Protection INSEMEX Petrosani has identified as causes for the occurrence of high pressure peaks in the case of electric motor enclosures, the internal volume, the geometrical shape of motor enclosures and the very intricate and complex internal arrangement of such motor enclosures (especially in the case of large motor enclosures), having in mind the tendency of motor manufacturers for chemical and petrochemical industry to manufacture motors having more complex geometrical shapes.

scholarly journals On-wall and interior separation in a two-fluid boundary layer

2019 ◽  
Vol 119 (1) ◽  
pp. 1-21
Author(s):  
Sergei N. Timoshin ◽  
Pallu Thapa
Keyword(s):  
Boundary Layer ◽  
Pressure Variation ◽  
Flow Reversal ◽  
Reversed Flow ◽  
Two Fluids ◽  
Transverse Pressure ◽  
Fluid Boundary ◽  
Interior Flow ◽  
High Reynolds ◽  
Two Fluid

Abstract A two-fluid boundary layer is considered in the context of a high Reynolds number Poiseuille–Couette channel flow encountering an elongated shallow obstacle. The flow is laminar, steady and two-dimensional, with the boundary layer shown to have the pressure unknown in advance and a specified displacement (a condensed boundary layer). The focus is on the detail of the flow reversal triggered by the obstacle. The interface between the two fluids passes through the boundary layer which, in conjunction with the effects of gravity and distinct densities in the two fluids, leads to several possible topologies of the reversed flow, including a conventional on-wall separation, interior flow reversal above the interface, and several combinations of the two. The effect of upstream influence due to a transverse pressure variation under gravity is mentioned briefly.

scholarly journals Growth rate of modulation instability of a laser pulse propagating in clustered gas

2013 ◽  
Vol 31 (3) ◽  
pp. 365-369 ◽  
Author(s):  
Rohit K. Mishra ◽  
Pallavi Jha
Keyword(s):  
Growth Rate ◽  
Laser Pulse ◽  
Pulse Duration ◽  
Growth Rates ◽  
Modulation Instability ◽  
Perturbation Growth

AbstractThis paper deals with the analysis of growth rate of modulation instability of a laser pulse propagating in a clustered gas. Finite pulse effects are considered to be a perturbation. Growth rates of modulation instability for 100 fs and 80 fs at the centroid as well as at the front and back of the pulses are evaluated and graphically analyzed. It has been shown that with decrease in pulse duration the growth rate of modulation instability increases at the front, back as well as at the centroid of the pulse. It is also shown that the change in growth rate of modulation instability at the front as well as at the back of the pulse in comparison to the centroid of the pulse for 80 fs pulse is less in comparison to that of 100 fs pulse.

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