scholarly journals CFD Investigations of Transient Cavitation Flows in Pipeline Based on Weakly-Compressible Model

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 448 ◽  
Author(s):  
Xuelin Tang ◽  
Xiangyu Duan ◽  
Hui Gao ◽  
Xiaoqin Li ◽  
Xiaoyan Shi
Keyword(s):  
Velocity Distribution ◽  
Compressible Fluid ◽  
Transient Flow ◽  
Volume Fraction ◽  
Evolution Process ◽  
Cavitation Flow ◽  
Pipe Length ◽  
Vapor Cavity ◽  
Wall Area ◽  
Weakly Compressible

In hydraulic systems, transient flow often occurs and may results in cavitation in pipelines. In this paper, the Computational Fluid Dynamics (CFD) method based on the Fluent software was used to investigate the cavitation flow in pipeline; the density-pressure model was incorporated into the continuity equation by using further development of UDF (user defined function), which reflects the variable wave speed of the transient cavitation flow, and the related algorithms were established based on weakly compressible fluid Reynolds Average Navier-Stokes (RANS) techniques. Firstly, the numerical simulations of the transient non-cavitation and cavitation flows caused by the fast closing valve in the reservoir-pipe-valve system were carried out by using the grid slip technique. The simulation results can enrich the flow field information such as velocity, pressure and vapor volume fraction. Through the evolution process of the pressure field, the propagation characteristics of pressure waves can be analyzed qualitatively and quantitatively. Through the evolution process of the velocity field, it can be seen that the velocity distribution in the wall area changes rapidly and has a high gradient, which mainly depends on the viscosity. However, the change of the velocity distribution in the core region is related to the velocity distribution of the history of the past time, which mainly depends on the diffusion. The formation, development and collapse of the cavity can be successfully captured, and it can be clearly and visually observed that the uneven distribution of vapor cavity in the direction of pipe length and pipe diameter, and the vapor cavity move slowly along the top of the pipe wall. Rarefaction wave’s propagation into pressure decreasing region and pressure increasing region can lead to different results of cavitation flow. The accuracy and reliability of the weakly compressible fluid RANS method were verified by comparing the calculated results with the experimental data.

Transient flow of viscous compressible fluid past a heated cylinder

2016 ◽  
Vol 5 (3/4) ◽  
pp. 172 ◽  
Author(s):  
Nan Chen ◽  
Fanglin Wang ◽  
Ruifeng Hu ◽  
Nepal C. Roy ◽  
Md. Anwar Hossain
Keyword(s):  
Compressible Fluid ◽  
Transient Flow ◽  
Viscous Compressible Fluid ◽  
Heated Cylinder

Transient Flow of a Compressible Fluid in a Connected Layered Permeable Medium

2004 ◽  
Vol 57 (2) ◽  
pp. 153-169 ◽  
Author(s):  
B. Lenoach ◽  
T. S. Ramakrishnan ◽  
R. K. M. Thambynayagam
Keyword(s):  
Compressible Fluid ◽  
Transient Flow

scholarly journals A DEPTH-INTEGRATED EQUATION FOR LARGE SCALE MODELING OF TSUNAMI IN WEAKLY COMPRESSIBLE FLUID

2014 ◽  
Vol 1 (34) ◽  
pp. 9 ◽  
Author(s):  
Ali Abdolali ◽  
Claudia Cecioni ◽  
Giorgio Bellotti ◽  
Paolo Sammarco
Keyword(s):  
Compressible Fluid ◽  
Large Scale ◽  
Scale Modeling ◽  
Weakly Compressible ◽  
Large Scale Modeling

EQUILIBRIUM VELOCITY DISTRIBUTION FUNCTIONS FOR A KINETIC MODEL OF TWO-PHASE FLOWS

1995 ◽  
Vol 05 (02) ◽  
pp. 191-211 ◽  
Author(s):  
LIONEL SAINSAULIEU
Keyword(s):  
Velocity Distribution ◽  
Gas Flow ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Velocity Distribution Function ◽  
Distribution Functions ◽  
Solid Particles ◽  
Navier Stokes ◽  
Two Phase ◽  
Entropy Balance

We consider a cloud of solid particles in a gas flow. The cloud is described by a probability density function which satisfies a kinetic equation. The gas flow is modeled by Navier-Stokes equations. The two phases exchange momentum and energy. We obtain the entropy balance of the gas flow and deduce some bounds for the volume fraction of the gas phase. Writing the entropy balance for the dispersed phase enables one to determine the particles equilibrium velocity distribution function when the gas flow is known.

scholarly journals The Unsteady Flow of a Weakly Compressible Fluid in a Thin Porous Layer I: Two-Dimensional Theory

2009 ◽  
Vol 69 (4) ◽  
pp. 1084-1109
Author(s):  
D. J. Needham ◽  
S. Langdon ◽  
G. S. Busswell ◽  
J. P. Gilchrist
Keyword(s):  
Unsteady Flow ◽  
Porous Layer ◽  
Compressible Fluid ◽  
Two Dimensional ◽  
Dimensional Theory ◽  
Weakly Compressible ◽  
Layer I

scholarly journals Numerical Modeling of Water Movement from Buried Vertical Ceramic Pipes through Soils

2018 ◽  
Vol 24 (6) ◽  
pp. 72
Author(s):  
Zena Kamil Rasheed ◽  
Maysoon Basheer Abid
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Transient Flow ◽  
Initial Conditions ◽  
Irrigation System ◽  
Pipe Length ◽  
Ceramic Pipe ◽  
Initial Soil

The problem of water scarcity is becoming common in many parts of the world, to overcome part of this problem proper management of water and an efficient irrigation system are needed.  Irrigation with a buried vertical ceramic pipe is known as a very effective in the management of irrigation water.  The two- dimensional transient flow of water from a buried vertical ceramic pipe through homogenous porous media is simulated numerically using the HYDRUS/2D software.  Different values of pipe lengths and hydraulic conductivity were selected.  In addition, different values of initial volumetric soil water content were assumed in this simulation as initial conditions.  Different values of the applied head were assumed in this simulation as boundary conditions.  The results of this research showed that greater spreading occurs in the horizontal direction.  Increasing applied heads, initial soil water contents and pipe hydraulic conductivities, cause increasing the size of wetting patterns but in a few increases.  Also, the results showed that the empirical formulas which can be used for expressing the wetted width and depth in terms of applied head, initial soil water content, application time, pipe hydraulic conductivity, and pipe length, are good and can be used as design equations.        

scholarly journals Numerical Modeling of Water Movement from Buried Vertical Ceramic Pipes through Coarse Soils

2018 ◽  
Vol 13 (4) ◽  
pp. 164-173
Author(s):  
Zena Kamil Rasheed ◽  
Maysoon Basheer Abid
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Transient Flow ◽  
Vertical Direction ◽  
Empirical Formulas ◽  
Pipe Length ◽  
Ceramic Pipe ◽  
Initial Soil

Problem of water scarcity is becoming common in many parts of the world.  Thus to overcome this problem proper management of water and an efficient irrigation systems are needed.  Irrigation with buried vertical ceramic pipe is known as a very effective in management of irrigation water.  The two- dimensional transient flow of water from a buried vertical ceramic pipe through homogenous porous media is simulated numerically using the software HYDRUS/2D to predict empirical formulas that describe the predicted results accurately.   Different values of pipe lengths and hydraulic conductivity were selected.  In addition, different values of initial volumetric soil water content were assumed in this simulation as initial conditions.  Different values of applied head were assumed in this simulation as a boundary conditions.  In general, a good agreement was obtained when comparing the predicted results with available measured values.  The results of this research showed that greater spreading occur in vertical direction.  Increasing applied heads, initial soil water contents, pipe hydraulic conductivities, cause increasing the size of wetting patterns.  Also the results showed that the empirical formulas which can be used for expressing the wetted width and depth in terms of applied head, initial soil water content, application time, pipe hydraulic conductivity, and pipe length, are good and can be used as a designing equations.  

Transient flow of a viscous compressible fluid in a circular tube after a sudden point impulse

2010 ◽  
Vol 644 ◽  
pp. 97-106 ◽  
Author(s):  
B. U. FELDERHOF
Keyword(s):  
Compressible Fluid ◽  
Transient Flow ◽  
Stokes Equations ◽  
Circular Tube ◽  
Slip Boundary Condition ◽  
Navier Stokes ◽  
Viscous Compressible Fluid ◽  
Navier Stokes Equations ◽  
Slip Boundary ◽  
Short Time

The flow of a viscous compressible fluid in a circular tube generated by a sudden impulse at a point on the axis is studied on the basis of the linearized Navier–Stokes equations. A no-slip boundary condition is assumed to hold on the wall of the tube. Owing to the finite velocity of sound the flow behaviour differs qualitatively from that of an incompressible fluid. The flow velocity and the pressure disturbance at any fixed point different from the source point vanish at short time and decay at long times with a t−3/2 power law.

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