Peristaltic Flow in a Deformable Channel

2011 ◽  
Vol 66 (1-2) ◽  
pp. 24-32 ◽  
Author(s):  
Dil Nawaz ◽  
Khan Marawat ◽  
Saleem Asghar
Keyword(s):  
Stokes Equations ◽  
Expansion Ratio ◽  
Peristaltic Flow ◽  
Wave Number ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Peristaltic Motion ◽  
Navier Stokes Equations ◽  
Small Wave Number ◽  
Deformable Channel

The effects of wall contraction or expansion on the characteristics of the peristaltic flow have been considered in this paper. For that, we present a theoretical model of laminar incompressible viscous peristaltic flow in a deformable channel. The problem is modeled in terms of unsteady twodimensional Navier Stokes equations and the solution is obtained using the perturbation method. The physical parameters appearing due to deformation and the peristaltic motion are the wall expansion ratio (α) and the wave number (δ ), respectively. Analytic perturbation results are obtained for small wave number and small wall expansion ratio. Basically the study is undertaken to examine the peristaltic motion along with the deformation of the channel. This will enhance our understanding of deformation/squeezing and peristalsis phenomena independently and jointly. Deformation effects are shown on the otherwise peristaltic fluid flow. The results of peristaltic flow [Shapiro et al., J. Fluid Mech. Digit. Archive 37, 799 (1969)] can be recovered for the limiting case of α equal to zero.

Modeling and computation of the cavitating flow in injection nozzle holes

2015 ◽  
Vol 06 (01) ◽  
pp. 1550003 ◽  
Author(s):  
Hatem Kanfoudi ◽  
Ridha Zgolli
Keyword(s):  
Transport Equation ◽  
Source Term ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Variable Density ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Cavitating Flows ◽  
Navier Stokes Equations ◽  
Injection Nozzle

Cavitating flows inside a diesel injection nozzle hole were simulated using a mixture model. A two-dimensional (2D) numerical model is proposed in this paper to simulate steady cavitating flows. The Reynolds-averaged Navier–Stokes equations are solved for the liquid and vapor mixture, which is considered as a single fluid with variable density and expressed as a function of the vapor volume fraction. The closure of this variable is provided by the transport equation with a source term Transport-equation based methods (TEM). The processes of evaporation and condensation are governed by changes in pressure within the flow. The source term is implanted in the CFD code ANSYS CFX. The influence of numerical and physical parameters is presented in detail. The numerical simulations are in good agreement with the experimental data for steady flow.

scholarly journals Inertial dynamics of air bubbles crossing a horizontal fluid–fluid interface

2012 ◽  
Vol 707 ◽  
pp. 405-443 ◽  
Author(s):  
Romain Bonhomme ◽  
Jacques Magnaudet ◽  
Fabien Duval ◽  
Bruno Piar
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Complex Dynamics ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Air Bubbles ◽  
Fluid Interface ◽  
Navier Stokes Equations ◽  
Film Drainage ◽  
Two Fluids

AbstractThe dynamics of isolated air bubbles crossing the horizontal interface separating two Newtonian immiscible liquids initially at rest are studied both experimentally and computationally. High-speed video imaging is used to obtain a detailed evolution of the various interfaces involved in the system. The size of the bubbles and the viscosity contrast between the two liquids are varied by more than one and four orders of magnitude, respectively, making it possible to obtain bubble shapes ranging from spherical to toroidal. A variety of flow regimes is observed, including that of small bubbles remaining trapped at the fluid–fluid interface in a film-drainage configuration. In most cases, the bubble succeeds in crossing the interface without being stopped near its undisturbed position and, during a certain period of time, tows a significant column of lower fluid which sometimes exhibits a complex dynamics as it lengthens in the upper fluid. Direct numerical simulations of several selected experimental situations are performed with a code employing a volume-of-fluid type formulation of the incompressible Navier–Stokes equations. Comparisons between experimental and numerical results confirm the reliability of the computational approach in most situations but also points out the need for improvements to capture some subtle but important physical processes, most notably those related to film drainage. Influence of the physical parameters highlighted by experiments and computations, especially that of the density and viscosity contrasts between the two fluids and of the various interfacial tensions, is discussed and analysed in the light of simple models and available theories.

The Effect of Film Thickness on EHD-Driven Instability of Interface Separating Two Liquids

2009 ◽  
Author(s):  
Payam Sharifi ◽  
Asghar Esmaeeli
Keyword(s):  
Stokes Equations ◽  
Thin Liquid Film ◽  
Front Tracking ◽  
Thin Layers ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Interface Instability ◽  
Navier Stokes Equations ◽  
Dielectric Model ◽  
Leaky Dielectric Model

Most of the studies conducted so far on EHD-driven instability of superimposed fluids have been concerned with liquid layers of modest depths. In many applications, however, the liquid layers can be very thin. Since the dynamics in thin films is generally governed by lubrication equations rather than full Navier-Stokes equations, it is expected that the interface dynamics will be quite different from that of the liquids with modest depths. The objective of this study is to explore the effect of initial liquid thickness on the dynamics of the phase boundary. To do this end, we perform Direct Numerical Simulations (DNS) using a front tracking/finite difference scheme, in conjunction with Taylor’s leaky dielectric model. For the physical parameters used here, it is shown that for sufficiently thick liquid layers, the interface instability leads to formation of liquid columns that merge together to form a big column. However, for thin layers, the interactions between the columns are weaker and lead to a short and a longer column that are connected by a thin liquid film.

scholarly journals The thermochemical non-equilibrium scale effects of the high enthalpy nozzle

2020 ◽  
Author(s):  
Junmou Shen ◽  
Hongbo Lu ◽  
Ruiqu Li ◽  
Xing Chen ◽  
Handong Ma
Keyword(s):  
Stokes Equations ◽  
Scale Effects ◽  
Flow Region ◽  
Expansion Ratio ◽  
Navier Stokes ◽  
Ratio Increase ◽  
Navier Stokes Equations ◽  
High Enthalpy ◽  
Equilibrium Region ◽  
Non Equilibrium

Abstract The high enthalpy nozzle converts the high enthalpy stagnation gas into the hypervelocity free flow. The flow region of the high enthalpy nozzle consists of three parts: an equilibrium region upstream of the throat, a non-equilibrium region near the throat, and a frozen region downstream of the throat. Here we propose to consider the thermochemical non-equilibrium scale effects in the high enthalpy nozzle. With numerical solving axisymmetric compressible Navier-Stokes equations coupling with Park’s two-temperature model, the fully non-equilibrium solution is employed throughout the entire nozzle. Calculations are performed at different stagnation conditions with the different absolute scales and expansion ratio. The results of this study contain twofold. Firstly, as the absolute scale and expansion ratio increase, the freezing position is delayed, and the flow approaches equilibrium. Secondly, the vibrational temperature and Mach number decrease with the increase in the nozzle scale and expansion ratio，while the speed of sound, static pressure, and translational temperature increase as the nozzle scale and expansion ratio increase.

scholarly journals The thermochemical non-equilibrium scale effects of the high enthalpy nozzle

2020 ◽  
Author(s):  
Junmou Shen ◽  
Hongbo Lu ◽  
Ruiqu Li ◽  
Xing Chen ◽  
Handong Ma
Keyword(s):  
Stokes Equations ◽  
Scale Effects ◽  
Flow Region ◽  
Expansion Ratio ◽  
Navier Stokes ◽  
Ratio Increase ◽  
Navier Stokes Equations ◽  
High Enthalpy ◽  
Equilibrium Region ◽  
Non Equilibrium

Abstract The high enthalpy nozzle converts the high enthalpy stagnation gas into the hypervelocity free flow. The flow region of the high enthalpy nozzle consists of three parts: an equilibrium region upstream of the throat, a non-equilibrium region near the throat, and a frozen region downstream of the throat. Here we propose to consider the thermochemical non-equilibrium scale effects in the high enthalpy nozzle. With numerical solving axisymmetric compressible Navier-Stokes equations coupling with Park’s two-temperature model, the fully non-equilibrium solution is employed throughout the entire nozzle. Calculations are performed at different stagnation conditions with the different absolute scales and expansion ratio. The results of this study contain twofold. Firstly, as the absolute scale and expansion ratio increase, the freezing position is delayed, and the flow approaches equilibrium. Secondly, the vibrational temperature and Mach number decrease with the increase in the nozzle scale and expansion ratio，while the speed of sound, static pressure, and translational temperature increase as the nozzle scale and expansion ratio increase.

scholarly journals The thermochemical non-equilibrium scale effects of the high enthalpy nozzle

2020 ◽  
Author(s):  
Junmou Shen ◽  
Hongbo Lu ◽  
Ruiqu Li ◽  
Xing Chen ◽  
Handong Ma
Keyword(s):  
Stokes Equations ◽  
Scale Effects ◽  
Flow Region ◽  
Expansion Ratio ◽  
Navier Stokes ◽  
Ratio Increase ◽  
Navier Stokes Equations ◽  
High Enthalpy ◽  
Equilibrium Region ◽  
Non Equilibrium

Abstract The high enthalpy nozzle converts the high enthalpy stagnation gas into the hypervelocity free flow. The flow region of the high enthalpy nozzle consists of three parts: an equilibrium region upstream of the throat, a non-equilibrium region near the throat, and a frozen region downstream of the throat. Here we propose to consider the thermochemical non-equilibrium scale effects in the high enthalpy nozzle. With numerical solving axisymmetric compressible Navier-Stokes equations coupling with Park’s two-temperature model, the fully non-equilibrium solution is employed throughout the entire nozzle. Calculations are performed at different stagnation conditions with the different absolute scales and expansion ratio. The significant results of this study contain twofold. Firstly, as the absolute scale and expansion ratio increase, the freezing position is delayed, and the flow approaches equilibrium. Secondly, the vibrational temperature and Mach number decrease with the increase in the nozzle scale and expansion ratio，while the speed of sound, static pressure, and translational temperature increase as the nozzle scale and expansion ratio increase.

Numerical Simulations of Three-Dimensional Flows in a Cubic Cavity With an Oscillating Lid

1993 ◽  
Vol 115 (4) ◽  
pp. 680-686 ◽  
Author(s):  
Reima Iwatsu ◽  
Jae Min Hyun ◽  
Kunio Kuwahara
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Time Dependent ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Navier Stokes Equations ◽  
Sinusoidal Oscillations ◽  
Dependent Flow

Numerical studies are made of three-dimensional flow of a viscous fluid in a cubical container. The flow is driven by the top sliding wall, which executes sinusoidal oscillations. Numerical solutions are acquired by solving the time-dependent, three-dimensional incompressible Navier-Stokes equations by employing very fine meshes. Results are presented for wide ranges of two principal physical parameters, i.e., the Reynolds number, Re ≤ 2000 and the frequency parameter of the lid oscillation, ω′ ≤ 10.0. Comprehensive details of the flow structure are analyzed. Attention is focused on the three-dimensionality of the flow field. Extensive numerical flow visualizations have been performed. These yield sequential plots of the main flows as well as the secondary flow patterns. It is found that the previous two-dimensional computational results are adequate in describing the main flow characteristics in the bulk of interior when ω′ is reasonably high. For the cases of high-Re flows, however, the three-dimensional motions exhibit additional complexities especially when ω′ is low. It is asserted that, thanks to the recent development of the supercomputers, calculation of three-dimensional, time-dependent flow problems appears to be feasible at least over limited ranges of Re.

scholarly journals The Effect of Varying Magnetic Number, Reynolds Number and Pressure Gradient on Velocity Profiles in an MHD Flow

2020 ◽  
Vol 5 (7) ◽  
pp. 387-394
Author(s):  
LIHAVI ANNET ◽  
Dr. Virginia Kitetu ◽  
Dr. Mary wainaina
Keyword(s):  
Reynolds Number ◽  
Pressure Gradient ◽  
Hartmann Number ◽  
Stokes Equations ◽  
Mhd Flow ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Parallel Plates ◽  
Navier Stokes Equations ◽  
Electrically Conducting

Magnetohydrodynamic ow of a hot viscous electrically conducting incompressible uid through parallel plates is studied. In the study, the e ect of Hartmann number (M), pressure gradient and Reynolds number (Re) on the velocity eld is investigated. The Navier-stokes equations were coupled with Ohms law and then solved using nite di erence method (FDM). The velocity eld was computed for various values of the physical parameters and shown graphically. It was found that as the Hartmann number M increases, the velocity pro les decreased due to increased Lorents force while an increase in Reynolds number causes an increase in the velocity of the uid. All these analysis was done using MATLAB program and the results were presented in tables and graphs.

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