scholarly journals Application of an alternative mesh morphing method on the numerical modeling of oscillating wave surge converters

RBRH ◽  
2019 ◽  
Vol 24 ◽  
Author(s):  
Guilherme Fuhrmeister Vargas ◽  
Edith Beatriz Camaño Schettini
Keyword(s):  
Numerical Modeling ◽  
Turbulence Modeling ◽  
Experimental Studies ◽  
Ocean Waves ◽  
Navier Stokes ◽  
Ocean Bottom ◽  
Mesh Morphing ◽  
Wave Energy Converters ◽  
Relative Differences ◽  
Good Agreement

ABSTRACT A technology capable of converting the horizontal motion of the ocean waves into energy by the application of a flap-piston system has been improved over the last few years, this device is known as oscillating wave surge converter. This system has great potential, already proven, for electric power generation. The computational fluid dynamics is one of the most used tools for the study of wave energy converters. In this context, the present paper proposes the application of an alternative mesh morphing method to represent the hydrodynamics of these devices, which is based on a bottom that oscillates with the converter, leading the flap to reach high inclinations without causing numerical divergences. The study is performed using the OpenFOAM computational code and its extension OLAFOAM. These are based on Reynolds Average Navier Stokes (RANS) turbulence modeling and the Volume of Fluid method (VOF) for the free surface representation, which are applied to a bidimensional model, allowing the numerical modeling of the converter. The proposed method presented good agreement of the results when compared to the experimental studies in similar hydrodynamic cases. The methodology based on a moving bottom presented relative differences, concerning the method that considers the bottom as fixed, between 4% and 17% for the cases where the flap is near to the ocean bottom and up to 8% for cases where it is further away.

Numerical Modeling of Evolution of Boundary Between Incompressible Gas and Liquid in Two-Dimensional Region

2006 ◽  
Vol 4 ◽  
pp. 224-236
Author(s):  
A.S. Topolnikov
Keyword(s):  
Numerical Modeling ◽  
Interphase Boundary ◽  
Incompressible Liquid ◽  
Stokes Equations ◽  
Numerical Code ◽  
Navier Stokes ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Incompressible Media ◽  
Good Agreement

The paper is devoted to numerical modeling of Navier–Stokes equations for incompressible media in the case, when there exist gas and liquid inside the rectangular calculation region, which are separated by interphase boundary. The set of equations for incompressible liquid accounting for viscous, gravitational and surface (capillary) forces is solved by finite-difference scheme on the spaced grid, for description of interphase boundary the ideology of Level Set Method is used. By developed numerical code the set of hydrodynamic problems is solved, which describe the motion of two-phase incompressible media with interphase boundary. As a result of numerical simulation the solutions are obtained, which are in good agreement with existing analytical and experimental solutions.

scholarly journals Stabilization of crossflow instability with plasma actuators: Linearized Navier–Stokes simulations

2019 ◽  
Vol 234 (1) ◽  
pp. 68-78
Author(s):  
Kean Lee Kang ◽  
Richard Ashworth ◽  
Shahid Mughal
Keyword(s):  
Experimental Studies ◽  
Cross Flow ◽  
Gradient Flow ◽  
Plasma Actuators ◽  
Navier Stokes ◽  
The European Union ◽  
Measurement Plane ◽  
Crossflow Instability ◽  
Non Linear ◽  
Good Agreement

This paper describes work carried out within the European Union (EU)-Russia Buterfli project to look at the control of transition-causing “target” stationary cross flow vortices, by the use of distributed plasma actuation to generate sub-dominant “killer” modes. The objective is to use the “killer” modes to control the “target” modes through a non-linear stabilizing mechanism. The numerical modelling and results are compared to experimental studies performed at the TsAGI T124 tunnel for a swept plate subject to a favorable pressure gradient flow. A mathematical model for the actuator developed at TsAGI was implemented in a linearized Navier–Stokes (LNS) solver and used to model and hence predict “killer” mode amplitudes at a measurement plane in the experiment. The LNS analysis shows good agreement with experiment, and the results are used as input for non-linear parabolized stability equation (PSE) analysis to predict the effect of these modes on crossflow transition. Whilst the numerical model indicates a delay in transition, experimental results indicated an advance in transition rather than delay. This was determined to be due to actuator-induced unsteadiness arising in the experiment, resulting in the generation of travelling crossflow disturbances which tended to obscure and thus dominate the plasma stabilized stationary disturbances.

Study the influence of ship length ratio on ship to ship interaction on moving in parallel on their hydrodynamic characteristics

2021 ◽  
pp. 61-66
Author(s):  
Р. Али ◽  
Н.В. Тряскин
Keyword(s):  
Hydrodynamic Interaction ◽  
Turbulence Modeling ◽  
Relative Length ◽  
Velocity Fields ◽  
Length Ratio ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Turbulent Model ◽  
Calm Water ◽  
Good Agreement

Суда в некоторых случаях эксплуатации могут двигаться в непосредственной близости друг от друга. Такой сценарий обычно связан с изменением полей давления и скорости вблизи корпуса судов, в результате чего возникают гидродинамические силы и моменты взаимодействия, которые сильно зависит от относительной длины. В этой статье была проведена серия систематических расчётов на двух корпусах KVLCC2, движущихся на большой глубине в безветренную погоду с одинаковой постоянной малой скоростью, не превышающей 4 уз., чтобы исследовать влияние отношения длин на силы и моменты гидродинамического взаимодействия. OpenFOAM, пакет CFD с открытым исходным кодом использовался для организации и проведения расчётов. Метод осреднения по Рейнольдсу уравнений Навье-Стокса (RANS) применялся для моделирования турбулентности. Хорошо известная модель турбулентности использовалась для замыкания уравнений Навье-Стокса. Числовые результаты, касающиеся поля скоростей и гидродинамического следа за судами, были обработаны, проанализированы, сопоставлены и показали хорошее согласование с экспериментальными результатами. Ships, during the lightering operations, are forced to sail in a close position to each other, such a scenario generally associates with a change in the pressure and velocity fields surrounding their hulls, as a result, interaction hydrodynamic forces and moments are generated which are strongly related to the relative length of the interacted ships. In this paper, a series of systematic computations were performed on two KVLCС2 hulls advancing in deep and calm water with the same constant low speed (full scale speed 4kt) in order to investigate the influence of the length ratio on the hydrodynamic interaction forces and moments during the lightering operation. OpenFOAM, an open-source CFD packet was used for carrying out the simulations, Reynolds Averaged Navier-Stokes (RANS) method was used for turbulence modeling and the well-known turbulent model k-ω SST was used to close RANS equations. Numerical results have been post-processed, analyzed, compared and found to be of a good agreement with the experimental results. The velocity fields and wake were presented and analyzed.

A Navier-Stokes Analysis of the Stall Flutter Characteristics of the Buffum Cascade

2000 ◽  
Author(s):  
Stefan Weber ◽  
Max F. Platzer
Keyword(s):  
Mach Number ◽  
Turbulence Modeling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Navier Stokes ◽  
Implicit Time ◽  
Fully Implicit ◽  
High Incidence ◽  
Stall Flutter ◽  
Good Agreement

Numerical stall flutter prediction methods are highly needed as modern jet engines require blade designs close to the stability boundaries of the performance map. A Quasi-3D Navier-Stokes code is used to analyze the flow over the oscillating cascade designed and manufactured by Pratt & Whitney, and studied at the NASA Glenn Research Center by Buffum et al. The numerical method solves for the governing equations with a fully implicit time-marching technique in a single passage by making use of a direct-store, periodic boundary condition. For turbulence modeling the Baldwin-Lomax model is used. To account for transition, the criterion to predict the onset location suggested by Baldwin and Lomax is incorporated. Buffum et al. investigated two incidence cases for three different Mach numbers. The low-incidence case at a Mach number of 0.5 exhibited the formation of small separation bubbles at reduced oscillation frequencies of 0.8 and 1.2. For this case the present approach yielded good agreement with the steady and oscillatory measurements. At high-incidence at the same Mach number of 0.5 the measured steady-state pressure distribution and the separation bubble on the upper surface was also found in good agreement with the experiment. But computations for oscillations at high-incidence failed to predict the negative damping contribution caused by the leading edge separation.

Numerical Modeling of a Static Cavitation Module

2016 ◽  
Vol 817 ◽  
pp. 64-69
Author(s):  
Tatiana Vitenko ◽  
Paweł Droździel ◽  
Nazar Horodysky
Keyword(s):  
Experimental Data ◽  
Numerical Modeling ◽  
Numerical Modelling ◽  
Stokes Equation ◽  
Liquid State ◽  
Software Package ◽  
Navier Stokes ◽  
State Equations ◽  
Navier Stokes Equation ◽  
Good Agreement

This paper presents the results of numerical modelling of cavitation flows in a hydrodynamic module. The simulation was performed using the SolidWorks software package. The computations were made based on the Navier-Stokes equation combined with liquid state equations and empirical dependencies which define liquid parameters. The numerical results are in good agreement with experimental data.

scholarly journals Numerical modeling of the 2013 meteorite entry in Chebarkul Lake, Russia

2017 ◽  
Author(s):  
Andrey Kozelkov ◽  
Andrey Kurkin ◽  
Efim Pelinovsky ◽  
Vadim Kurulin ◽  
Elena Tyatyushkina
Keyword(s):  
Numerical Modeling ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Tsunami Waves ◽  
Theoretical Predictions ◽  
Meteorite Fall ◽  
Phase Fluid ◽  
Good Agreement

Abstract. The results of the numerical simulation of possible hydrodynamic perturbations in Lake Chebarkul (Russia) as a consequence of the meteorite fall of 2013 (Feb. 15) are presented. The numerical modeling is based on the Navier-Stokes equations for a two-phase fluid. The results of the simulation of a meteorite entering the water at an angle of 20 degrees are given. Numerical experiments are carried out both when the lake is covered with ice and when it isn't. The estimation of size of the destructed ice cover is made. It is shown that the size of the observed ice-hole at the place of the meteorite fall is in good agreement with the theoretical predictions, as well as with other estimates. The heights of tsunami waves generated by a small meteorite entering the lake are small enough (a few centimeters) according to the estimations. However, the danger of a tsunami of meteorite or asteroid origin should not be underestimated.

scholarly journals Numerical modeling of the 2013 meteorite entry in Lake Chebarkul, Russia

2017 ◽  
Vol 17 (5) ◽  
pp. 671-683 ◽  
Author(s):  
Andrey Kozelkov ◽  
Andrey Kurkin ◽  
Efim Pelinovsky ◽  
Vadim Kurulin ◽  
Elena Tyatyushkina
Keyword(s):  
Numerical Modeling ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Tsunami Waves ◽  
Theoretical Predictions ◽  
Meteorite Fall ◽  
Phase Fluid ◽  
Good Agreement

Abstract. The results of the numerical simulation of possible hydrodynamic perturbations in Lake Chebarkul (Russia) as a consequence of the meteorite fall of 2013 (15 February) are presented. The numerical modeling is based on the Navier–Stokes equations for a two-phase fluid. The results of the simulation of a meteorite entering the water at an angle of 20° are given. Numerical experiments are carried out both when the lake is covered with ice and when it is not. The estimation of size of the destructed ice cover is made. It is shown that the size of the observed ice hole at the place of the meteorite fall is in good agreement with the theoretical predictions, as well as with other estimates. The heights of tsunami waves generated by a small meteorite entering the lake are small enough (a few centimeters) according to the estimations. However, the danger of a tsunami of meteorite or asteroid origin should not be underestimated.

A Navier–Stokes Analysis of the Stall Flutter Characteristics of the Buffum Cascade

2000 ◽  
Vol 122 (4) ◽  
pp. 769-776 ◽  
Author(s):  
Stefan Weber ◽  
Max F. Platzer
Keyword(s):  
Mach Number ◽  
Turbulence Modeling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Navier Stokes ◽  
Implicit Time ◽  
Fully Implicit ◽  
High Incidence ◽  
Stall Flutter ◽  
Good Agreement

Numerical stall flutter prediction methods are much needed, as modern jet engines require blade designs close to the stability boundaries of the performance map. A Quasi-3D Navier–Stokes code is used to analyze the flow over the oscillating cascade designed and manufactured by Pratt & Whitney, and studied at the NASA Glenn Research Center by Buffum et al. The numerical method solves for the governing equations with a fully implicit time-marching technique in a single passage by making use of a direct-store, periodic boundary condition. For turbulence modeling, the Baldwin–Lomax model is used. To account for transition, the criterion to predict the onset location suggested by Baldwin and Lomax is incorporated. Buffum et al. investigated two incidence cases for three different Mach numbers. The low-incidence case at a Mach number of 0.5 exhibited the formation of small separation bubbles at reduced oscillation frequencies of 0.8 and 1.2. For this case the present approach yielded good agreement with the steady and oscillatory measurements. At high incidence at the same Mach number of 0.5 the measured steady-state pressure distribution and the separation bubble on the upper surface was also found in good agreement with the experiment. But computations for oscillations at high incidence failed to predict the negative damping contribution caused by the leading edge separation. [S0889-504X(00)01304-0]

Computational Analysis of Heat Transfer Enhancement in Square Ducts With V-Shaped Ribs: Turbine Blade Cooling

2005 ◽  
Vol 127 (4) ◽  
pp. 425-433 ◽  
Author(s):  
R. Jia ◽  
B. Sunde´n ◽  
M. Faghri
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Transfer Enhancement ◽  
Turbulence Modeling ◽  
Experimental Studies ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Sampling Points

Experimental studies have revealed that both downstream and upstream pointing V-shaped ribs result in more heat transfer enhancement than transverse straight ribs in ducts. However, based on the available experimental results, contradiction exists whether the upstream or the downstream pointing V-shaped ribs orientation is superior for better enhancement in heat transfer. Further investigations are thus needed concerning the heat transfer and fluid flow phenomena in ducts with V-shaped ribs to clarify this. In the present investigation a numerical approach is taken and the heat and fluid flow is numerically simulated by a multi-block parallel 3D solver. For turbulence modeling, the v2¯ f-kε model is employed but results from previous EASM calculations are also considered in analyzing and attempting to understand the various experimental data. Large eddy simulations (LES) are also carried to evaluate the accuracy and reliability of the results of Reynolds-averaged Navier-Stokes (RANS) methods and to understand the underlying physical phenomena. It is suggested that the discrepancy between the various experiments most probably is due to the measurement methods, or the number of sampling points. With the TC (thermocouples) technique, a few sampling points are not sufficient to represent the heat transfer behavior in V-shaped ribs, due to the uneven distribution of the heat transfer coefficients.

Simulation of Unsteady Flow Around a Cylinder

2015 ◽  
Vol 3 (2) ◽  
pp. 28-49
Author(s):  
Ridha Alwan Ahmed
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Mean Value ◽  
Navier Stokes ◽  
Cylinder Surface ◽  
Navier Stokes Equations ◽  
Flow Around A Cylinder ◽  
Numerical Grid ◽  
Good Agreement

       In this paper, the phenomena of vortex shedding from the circular cylinder surface has been studied at several Reynolds Numbers (40≤Re≤ 300).The 2D, unsteady, incompressible, Laminar flow, continuity and Navier Stokes equations have been solved numerically by using CFD Package FLUENT. In this package PISO algorithm is used in the pressure-velocity coupling.        The numerical grid is generated by using Gambit program. The velocity and pressure fields are obtained upstream and downstream of the cylinder at each time and it is also calculated the mean value of drag coefficient and value of lift coefficient .The results showed that the flow is strongly unsteady and unsymmetrical at Re>60. The results have been compared with the available experiments and a good agreement has been found between them

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