Numerical Study of Surface Tension Effect on the Hydrodynamic Modeling of the Partially Submerged Propeller's Blade Section

2016 ◽  
Vol 32 (5) ◽  
pp. 653-664 ◽  
Author(s):  
E. Yari ◽  
H. Ghassemi
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Volume Fraction ◽  
Numerical Study ◽  
Suction Side ◽  
Navier Stokes ◽  
Surface Tension Effect ◽  
Pressure Distributions ◽  
Blade Section ◽  
The Impact

AbstractThis article is presented the surface tension effect on the two-dimensional blade section of the partially submerged propeller (PSP). In this regard, blade is entered to the water that causes to splash the water due to the impact and free surface. Also, because of the blade's angle of attack suction side is vented by air and pressure side is wetted and gripped the water to generate thrust. The Reynolds-Averaged Navier-Stokes (RANS) method is used in order to predict the hydrodynamic flow from entering to the exit. Present paper is numerically investigated the effect of free surface and surface tension i.e. related to the Weber number. So, many numerical results are presented and discussed that are included volume fraction, ventilation zones, pressure distributions, vertical and horizontal forces at various Weber numbers.

scholarly journals Splash jet generated by collision of two liquid wedges

2013 ◽  
Vol 737 ◽  
pp. 132-145 ◽  
Author(s):  
Y. A. Semenov ◽  
G. X. Wu ◽  
J. M. Oliver
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Hodograph Method ◽  
Pressure Distributions ◽  
Wide Range ◽  
Self Similar Solution ◽  
Gravity Effects ◽  
Self Similar ◽  
The Impact ◽  
Analytical Expressions

AbstractA complete nonlinear self-similar solution that characterizes the impact of two liquid wedges symmetric about the velocity direction is obtained assuming the liquid to be ideal and incompressible, with negligible surface tension and gravity effects. Employing the integral hodograph method, analytical expressions for the complex potential and for its derivatives are derived. The boundary value problem is reduced to two integro-differential equations in terms of the velocity modulus and angle to the free surface. Numerical results are presented in a wide range of wedge angles for the free surface shapes, streamline patterns, and pressure distributions. It is found that the splash jet may cause secondary impacts. The regions with and without secondary impacts in the plane of the wedge angles are determined.

scholarly journals Numerical Study of Density Ratio Influence on Global Wave Shapes Before Impact

2018 ◽  
Author(s):  
Stéphane Etienne ◽  
Yves-Marie Scolan ◽  
Laurent Brosset
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Gas Flow ◽  
Numerical Study ◽  
Mechanical Energy ◽  
Density Ratio ◽  
Free Surface Flows ◽  
Liquid Density ◽  
The Impact ◽  
Wave Shapes

The influence of the gas-to-liquid density ratio (DR) on the global wave shape before impact is studied through numerical simulations of the propagation of two different waves in a rectangular wave canal. Two different codes are used: the first one, named FSID, is a highly non-linear 2D bi-fluid potential code initially developed in the frame of SLOSHEL JIP (Kaminski et al. (2011)) to simulate incompressible inviscid free-surface flows without surface tension thanks to a desingularized technique and series of conformal mappings; the second one, named CADYF, is a bi-fluid high-fidelity front-tracking software developed by Ecole Polytechnique Montreal to simulate separated two-phase incompressible viscous flows with surface tension. The first studied wave leads to a flip-through impact while the second one leads to a large gas-pocket impact. Each condition is studied with water and three different gases with increasing densities corresponding to DR = 0.001, 0.003 and 0.005. The global wave shapes are compared a few tenths of second before the impact, before free surface instabilities triggered by the shearing gas flow have developed and also before any gas compressibility matters. Both codes give precisely the same global wave shapes. Whatever the condition studied, it is shown that DR has an influence on these global wave shapes. The trends observed from the simulations are the same as those described in Karimi et al. (2016) obtained from sloshing model tests with Single Impact Waves (SIW) in a 2D tank with a low filling level. A small part of the mechanical energy of the liquid is progressively given to the gas. The larger the DR, the larger this transfer of energy from the liquid to the gas. This explains an increasing delay of the wave front for increasing DRs.

Surface Roughness Impact on Secondary Flow and Losses in a Turbine Exhaust Casing

2018 ◽  
Author(s):  
Isak Jonsson ◽  
Valery Chernoray ◽  
Borja Rojo
Keyword(s):  
Surface Roughness ◽  
Secondary Flow ◽  
Suction Side ◽  
Pressure Probe ◽  
Time Resolved ◽  
Pressure Distributions ◽  
Turbulence Decay ◽  
Inlet Swirl ◽  
High Level ◽  
The Impact

This paper experimentally addresses the impact of surface roughness on losses and secondary flow in a Turbine Rear Structure (TRS). Experiments were performed in the Chalmers LPT-OGV facility, at an engine representative Reynolds number with a realistic shrouded rotating low-pressure turbine (LPT). Outlet Guide Vanes (OGV) were manufactured to achieve three different surface roughnesses tested at two Reynolds numbers, Re = 235000 and Re = 465000. The experiments were performed at on-design inlet swirl conditions. The inlet and outlet flow of the TRS were measured in 2D planes with a 5-hole probe and 7-hole probe accordingly. The static pressure distributions on the OGVs were measured and boundary layer studies were performed at the OGV midspan on the suction side with a time-resolved total pressure probe. Turbulence decay was measured within the TRS with a single hot-wire. The results showed a surprisingly significant increase in the losses for the high level of surface roughness (25–30 Ra) of the OGVs and Re = 465000. The increased losses were primary revealed as a result of the flow separation on the OGV suction side near the hub. The loss increase was seen but was less substantial for the intermediate roughness case (4–8 Ra). Experimental results presented in this work provide support for the further development of more advanced TRS and data for the validation of new CFD prediction methods for TRS.

Investigation of Three-Dimensional Flow in Microchannels With Patterned Surfaces

2007 ◽  
Author(s):  
Auro Ashish Saha ◽  
Sushanta K. Mitra
Keyword(s):  
Surface Tension ◽  
Flow Instability ◽  
Numerical Study ◽  
Three Dimensional ◽  
Surface Characteristics ◽  
Bottom Wall ◽  
Surface Tension Effect ◽  
Hydrophobic Region ◽  
Side Walls ◽  
Dimensional Simulation

A three-dimensional numerical simulation of flow in patterned microchannel with alternate layers of hydrophilic and hydrophobic surfaces at the bottom wall is studied here. Surface characteristics of the microchannel are accounted by specifying the contact angle and the surface tension of the fluid. Meniscus profiles with varying amplitude and shapes are obtained under the different specified surface conditions. Flow instability increases as the fluid at the bottom wall traverses alternately from hydrophilic region to hydrophobic region. To understand the surface tension effect of the side walls, a two-dimensional numerical study has also been carried out for the microchannel and the results are compared with three-dimensional simulation. The surface tension effect of the side walls enhances the capillary effect for three-dimensional case.

scholarly journals Numerical Study of Hydrodynamic Impact on Bubbly Water

2015 ◽  
Author(s):  
Mehdi Elhimer ◽  
Aboulghit El Malki Alaoui ◽  
Kilian Croci ◽  
Céline Gabillet ◽  
Nicolas Jacques
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Numerical Data ◽  
Void Volume Fraction ◽  
Bubbly Liquid ◽  
Impact Loads ◽  
Hydrodynamic Impact ◽  
Physical Mechanisms ◽  
The Impact ◽  
The Relationship

The phenomenon of slamming on a bubbly liquid has many occurrences in marine and costal engineering. However, experimental or numerical data on the effect of the presence of gas bubbles within the liquid on the impact loads are scarce and the related physical mechanisms are poorly understood. The aim of the present paper is to study numerically the relationship between the void volume fraction and the impact loads. For that purpose, numerical simulations of the impact of a cone on bubbly water have been performed using the finite element code ABAQUS/Explicit. The present results show the diminution of the impact loads with the increase of the void fraction. This effect appears to be related to the high compressibility of the liquid-gas mixture.

Numerical Study of High Velocity Impact onto MMC/Ceramic Layered Systems

2016 ◽  
Vol 715 ◽  
pp. 210-215
Author(s):  
Seung Hwan Lee ◽  
Minh Lee
Keyword(s):  
Mild Steel ◽  
Ceramic Tile ◽  
Volume Fraction ◽  
Numerical Study ◽  
Tungsten Alloy ◽  
Layered Systems ◽  
Depth Of Penetration ◽  
Ballistic Performance ◽  
Long Rod ◽  
The Impact

Metal Matrix Composites (MMCs) can be applied to military applications due to the light weight and the ballistic performance. In this study, a numerical simulation has been performed for the penetration of a long-rod penetrator into MMC/Ceramic layered systems. The impact velocity is 1.5km/s and the length to diameter (L/D) ratio is 10.6. First, the ballistic performances of each candidate materials are examined by doing the semi-infinite target simulation to estimate the depth of penetration (DOP) data. The materials included in this study are four (tungsten alloy, mild steel, SiC, MMC. The MMC materials are SiC/Al7075 (volume fraction around 45%). For a reference data, the impact simulation into mild-steel target only was also carried out. Finally, the main simulation is performed by varying the position of ceramic tile at three types of the thickness of ceramic tile. The residual velocity, residual mass and residual kinetic energy of the long-rod are obtained from the simulation. Based on these predicted values, the optimum system of the layered plate has been estimated.

Numerical Study of the Wave Impact on a Square Column Using Large Eddy Simulation

2007 ◽  
Author(s):  
H. T. C. Pedro ◽  
K.-W. Leung ◽  
M. H. Kobayashi ◽  
H. R. Riggs
Keyword(s):  
Numerical Study ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Navier Stokes ◽  
Wave Impact ◽  
Eddy Simulation ◽  
Subgrid Model ◽  
Large Eddy ◽  
Volume Approximation ◽  
The Impact

This work concerns the numerical investigation of the impact of a wave on a square column. The wave is generated by a dam break in a wave tank. Two turbulence models were used: Large Eddy Simulations (LES) and Unsteady Reynolds Averaged Navier-Stokes (URANS). The numerical simulations were carried out using a finite volume approximation and the SIMPLE algorithm for the solution of the governing equations. Turbulence was modeled with the standard Smagorinsky-Lilly subgrid-model for the LES and the standard κ-ε model for the URANS. The results are validated against experimental data for the wave impact on a square column facing the flow. The results, especially for LES, show very good agreement between the predictions and experimental results. The overall accuracy of the LES, as expected, is superior to the URANS. However, if computational resources are limited, URANS can still provide satisfactory results for structural design.

Numerical Simulation of Breaking Waves Using a Level Set Method

2002 ◽  
Author(s):  
Pablo Go´mez ◽  
Julio Herna´ndez ◽  
Joaqui´n Lo´pez ◽  
Fe´lix Faura
Keyword(s):  
Free Surface ◽  
Level Set Method ◽  
Level Set ◽  
Stokes Equations ◽  
Numerical Study ◽  
Operating Conditions ◽  
Breaking Wave ◽  
Level Set Function ◽  
Set Function ◽  
The Impact

A numerical study of the initial stages of wave breaking processes in shallow water is presented. The waves considered are assumed to be generated by moving a piston in a two-dimensional channel, and may appear, for example, in the injection chamber of a high-pressure die casting machine under operating conditions far from the optimal. A numerical model based on a finite-difference discretization of the Navier-Stokes equations in a Cartesian grid and a second-order approximate projection method has been developed and used to carry out the simulations. The evolution of the free surface is described using a level set method, with a reinitialization procedure of the level set function which uses a local grid refinement near the free surface. The ability of different algorithms to improve mass conservation in the reinitialization step of the level set function has been tested in a time-reversed single vortex flow. The results for the breaking wave profiles show the flow characteristics after the impact of the first plunging jet onto the wave’s forward face and during the subsequent splash-up.

A Numerical Study of Electrode Arrangements for Precise Microdrop Generation in an Electrowetting-Based Digital Microfluidic Platform

2019 ◽  
Author(s):  
Yin Guan ◽  
Baiyun Li ◽  
Mengnan Zhu ◽  
Shengjie Cheng ◽  
Jiyue Tu ◽  
...  
Keyword(s):  
Free Surface ◽  
Cell Model ◽  
Numerical Study ◽  
Digital Microfluidics ◽  
Surface Force ◽  
Viscous Force ◽  
Generation Process ◽  
Parallel Plates ◽  
Digital Microfluidic ◽  
The Impact

Abstract Owing to the wide applications in a large variety of multi-disciplinary areas, electrowetting-based digital microfluidics (DMF) has received considerable attention in the last decade. However, because of the complexity involved in the droplet generation process, the techniques and configurations for precise and controllable microdrop generation are still unclear. In this paper, a numerical study has been performed to investigate the impact of electrode arrangements on microdrop generation in an electrowetting-based DMF Platform proposed by a previously published experimental work. The governing equations for the microfluidic flow are solved by a finite volume formulation with a two-step projection method on a fixed numerical domain. The free surface of the microdrop is tracked by a coupled level-set and volume-of-fluid (CLSVOF) method, and the surface tension at the free surface is computed by the continuum surface force (CSF) scheme. A simplified viscous force scheme based on the ‘Hele-Shaw cell’ model is adopted to evaluate the viscous force exerted by the parallel plates. The generation process has been simulated with three different electrode arrangements, namely, ‘SL’, ‘SW’, and ‘SQ’. The effect of electrode arrangement on microdrop volume has been investigated. Besides, the influences of the initial microdrop location and volume on the generation process for the ‘SL’ design have been studied. The results can be used to advance microdrop generation techniques for various electrowetting-based DMF applications.

Sign in / Sign up

Export Citation Format

Share Document