scholarly journals FORCES INDUCED ON A VERTICAL BREAKWATER BY INCIDENT OBLIQUE WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 14
Author(s):  
Javier Lara ◽  
Pablo Higuera ◽  
Maria Maza ◽  
Manuel Del Jesus ◽  
Inigo J. Losada ◽  
...  
Keyword(s):  
Wave Train ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Two Dimensions ◽  
Navier Stokes ◽  
Coastal Structures ◽  
Vast Number ◽  
Dimensional Effects ◽  
Model Predictions ◽  
Vertical Breakwater

Over the last years Navier-Stokes numerical models have been developed to accurately simulate wave interaction with all kinds of coastal structures, focusing on both functionality and stability of coastal structures. Although several models have been used to simulate wave interaction with coastal structures in two dimensions (2DV) there are a vast number of three-dimensional effects that need to be investigated in order to improve the design. In this paper a new model called IH-FOAM has been applied to study a vertical breakwater at prototype scale. As a first attempt of validation, the model has been used to simulate a regular wave train generated with a relative angle with the breakwater inducing three-dimensional wave patterns not only seaward the structure due to reflection but also generating an overtopping discharge variation along the breakwater trunk. Pressure laws and overtopping discharge at three different cross-sections along the structure have been studied. The pressure laws have been compared with classical Goda’s formulation. Although, the numerical model predictions are in accordance with Goda’s calculations, a clear three-dimensional variability of wave-induced pressure has been observed. Moreover, an additional study has been performed calculating pressure laws on the side-wall at the breakwater head. Large three-dimensional effects are detected from the simulations due to the flow separation at that area. Overtopping model predictions have been compared with Overtopping Manual calculations showing very close values along the trunk. However, lower overtopping discharge values are observed at the breakwater head. This paper is a preliminary work to show the range of applicability of a three-dimensional Navier-Stokes model to study wave interaction with a vertical breakwater under the action of an oblique wave train.

Three-Dimensional Effects on Slamming Loads

2021 ◽  
Author(s):  
Shan Wang ◽  
C. Guedes Soares
Keyword(s):  
3D Model ◽  
Numerical Solutions ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
The Body ◽  
Navier Stokes ◽  
Courant Number ◽  
Dimensional Effects ◽  
Coefficient Distribution ◽  
Experimental Values

Abstract Three-dimensional effects on slamming loads predictions of a ship section are investigated numerically using the unsteady incompressible Reynolds-Average Navier-Stokes (RANS) equations and volume of fluid (VOF) method, which are implemented in interDyMFoam solver in open-source library OpenFoam. A convergence and uncertainty study is performed considering different resolutions and constant Courant number (CFL) following the ITTC guidelines. The numerical solutions are validated through comparisons of slamming loads and motions between the CFD simulations and the available experimental values. The total slamming force and slamming pressures on a 2D ship section and the 3D model are compared and discussed. Three-dimensional effects on the sectional force and the pressures are quantified both in transverse and longitudinal directions of the body considering various entry velocities. The non-dimensional pressure coefficient distribution on the 3D model is presented.

scholarly journals 3D Numerical Simulation of the Interaction between Waves and a T-Head Groin Structure

2020 ◽  
Vol 8 (3) ◽  
pp. 227
Author(s):  
Giovanni Cannata ◽  
Marco Tamburrino ◽  
Francesco Gallerano
Keyword(s):  
Numerical Model ◽  
Numerical Scheme ◽  
Wave Motion ◽  
Stokes Equations ◽  
Wave Train ◽  
Three Dimensional ◽  
Solid Material ◽  
Coastal Structures ◽  
Vertical Coordinate ◽  
Hydrodynamic Fields

The aim of coastal structures for the defense from erosion is to modify the hydrodynamic fields that would naturally occur with the wave motion, to produce zones of sedimentation of solid material, and to combat the recession of the coastline. T-head groin-shaped structures are among the most adopted in coastal engineering. The assessment of the effectiveness of such structures requires hydrodynamic study of the interaction between wave motion and the structure. Hydrodynamic phenomena induced by the interaction between wave motion and T-head groin structures have three-dimensionality features. The aim of the paper is to propose a new three-dimensional numerical model for the simulation of the hydrodynamic fields induced by the interaction between wave fields and coastal structures. The proposed model is designed to represent complex morphologies as well as coastal structures inside the domain. The numerical scheme solves the three-dimensional Navier–Stokes equations in a contravariant formulation, on a time-dependent coordinate system, in which the vertical coordinate varies over time to follow the free-surface elevation. The main innovative element of the paper consists in the proposal of a new numerical scheme that makes it possible to simulate flows around structures with sharp-cornered geometries. The proposed numerical model is validated against a well-known experimental test-case consisting in a wave train approaching a beach (non-parallel with the wave front), with the presence of a T-head groin structure. A detailed comparison between numerical and experimental results is shown.

scholarly journals Computational analysis of high-lift-generating airfoils for diffuser-augmented wind turbines

2021 ◽  
Vol 6 (1) ◽  
pp. 149-157
Author(s):  
Aniruddha Deepak Paranjape ◽  
Anhad Singh Bajaj ◽  
Shaheen Thimmaiah Palanganda ◽  
Radha Parikh ◽  
Raahil Nayak ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Computational Analysis ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Two Dimensions ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Energy Access ◽  
Cross Sectional ◽  
High Lift

Abstract. The impetus towards sustainable energy production and energy access has led to considerable research and development on decentralized generators, in particular diffuser-augmented wind turbines. This paper aims to characterize the performance of diffuser-augmented wind turbines (DAWTs) using high-lift airfoils employing a three-step computational analysis. The study is based on computational fluid dynamics, and the analysis is carried out by solving the unsteady Reynolds-averaged Navier–Stokes (URANS) equations in two dimensions. The rotor blades are modeled as an actuator disk, across which a pressure drop is imposed analogous to a three-dimensional rotor. We study the change in performance of the enclosed turbine with varying diffuser cross-sectional geometry. In particular, this paper characterizes the effect of a flange on the flow augmentation provided by the diffuser. We conclude that at the end of the three-step analysis, Eppler 423 showed the maximum velocity augmentation.

Characterization of Three-Dimensional Effects for the Rotating and Parked NREL Phase VI Wind Turbine

2006 ◽  
Vol 128 (4) ◽  
pp. 445-454 ◽  
Author(s):  
Sven Schmitz ◽  
Jean-Jacques Chattot
Keyword(s):  
Wind Turbine ◽  
Computational Models ◽  
Three Dimensional ◽  
Vortex Sheet ◽  
Inviscid Flow ◽  
Radial Force ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Flow Conditions ◽  
Dimensional Effects

This paper addresses three-dimensional effects which are pertinent to wind turbine aerodynamics. Two computational models were applied to the National Renewable Energy Laboratory Phase VI Rotor under rotating and parked conditions, a vortex line method using a prescribed wake, and a parallelized coupled Navier-Stokes/vortex-panel solver (PCS). The linking of the spanwise distribution of bound circulation between both models enabled the quantification of three-dimensional effects with PCS. For the rotating turbine under fully attached flow conditions, the effects of the vortex sheet dissipation and replacement by a rolled-up vortex on the computed radial force coefficients were investigated. A quantitative analysis of both radial pumping and Coriolis effect, known as the Himmelskamp effect, was performed for viscous as well as inviscid flow. For the parked turbine, both models were applied at various pitch angles corresponding to fully attached as well as stalled flow. For partially stalled flow, computed results revealed a vortical structure trailing from the blade’s upper surface close to the 40% radial station. This trailing vortex was documented as a highly unsteady flow structure in an earlier detached eddy simulation by another group, however, it was not directly observed experimentally but only inferred. Computed results show very good agreement with measured wind tunnel data for the PCS model. Finally, a new method for extracting three-dimensional airfoil data is proposed that is particularly well suited for highly stalled flow conditions.

Scaling of small vortices in stably stratified shear flows

2017 ◽  
Vol 821 ◽  
pp. 582-594 ◽  
Author(s):  
Kengo Deguchi
Keyword(s):  
Reynolds Number ◽  
Richardson Number ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Maximum Size ◽  
Navier Stokes ◽  
Large Reynolds Number ◽  
Order Unity ◽  
Steady Solutions

The present paper treats the large Reynolds number scaling of coherent structures in stably stratified flows sheared between two horizontally placed walls. Three-dimensional steady solutions are used to confirm the theoretical scaling. For small values of the Richardson number, the previously known scaling based on the vortex–wave interaction/self-sustaining process is found to give excellent predictions of the numerical results. When the Richardson number is increased, the maximum size of the vortices is limited by the Ozmidov scale. The largest possible Richardson number to sustain the vortices is predicted to be of order unity when the typical length scale of the vortices reaches the Kolmogorov scale. The minimum-scale vortices are governed by unit Reynolds number Navier–Stokes equations.

scholarly journals Localized vortex/Tollmien–Schlichting wave interaction states in plane Poiseuille flow

2016 ◽  
Vol 791 ◽  
pp. 97-121 ◽  
Author(s):  
L. J. Dempsey ◽  
K. Deguchi ◽  
P. Hall ◽  
A. G. Walton
Keyword(s):  
Reynolds Number ◽  
Poiseuille Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Travelling Wave ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
Plane Poiseuille Flow ◽  
Tollmien Schlichting

Strongly nonlinear three-dimensional interactions between a roll–streak structure and a Tollmien–Schlichting wave in plane Poiseuille flow are considered in this study. Equations governing the interaction at high Reynolds number originally derived by Bennett et al. (J. Fluid Mech., vol. 223, 1991, pp. 475–495) are solved numerically. Travelling wave states bifurcating from the lower branch linear neutral point are tracked to finite amplitudes, where they are observed to localize in the spanwise direction. The nature of the localization is analysed in detail near the relevant spanwise locations, revealing the presence of a singularity which slowly develops in the governing interaction equations as the amplitude of the motion is increased. Comparisons with the full Navier–Stokes equations demonstrate that the finite Reynolds number solutions gradually approach the numerical asymptotic solutions with increasing Reynolds number.

Three-dimensional flow past a rotating cylinder

2015 ◽  
Vol 766 ◽  
pp. 28-53 ◽  
Author(s):  
  Navrose ◽  
Jagmohan Meena ◽  
Sanjay Mittal
Keyword(s):  
Rotation Rate ◽  
Stokes Equations ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Navier Stokes ◽  
Neutral Stability ◽  
Stabilized Finite Element ◽  
Stabilized Finite Element Method ◽  
Integral Number

AbstractThree-dimensional computations are carried out for a spinning cylinder placed in a uniform flow. The non-dimensional rotation rate is varied in the range $0.0\leqslant {\it\alpha}\leqslant 5.0$. A stabilized finite element method is utilized to solve the incompressible Navier–Stokes equations in primitive variables formulation. Linear stability analysis of the steady state shows the existence of several new unstable three-dimensional modes for $200\leqslant \mathit{Re}\leqslant 350$ and $4.0\leqslant {\it\alpha}\leqslant 5.0$. The curves of neutral stability of these modes are presented in the $\mathit{Re}{-}{\it\alpha}$ parameter space. For the flow at $\mathit{Re}=200$ and rotation rate in the ranges $0.0\leqslant {\it\alpha}\leqslant 1.91$ and $4.34\leqslant {\it\alpha}\leqslant 4.7$, the vortex shedding, earlier reported in two dimensions and commonly referred to as parallel shedding, can also exist as oblique shedding. In this mode of shedding, the vortices are inclined to the axis of the cylinder. In fact, parallel shedding is a special case of oblique shedding. It is found that the span of the cylinder plays a significant role in the time evolution of the flow. Of all the unstable eigenmodes, with varied spanwise wavenumber, only the ones whose integral number of wavelengths fit the span length of the cylinder are selected to grow. For the flow at $\mathit{Re}=200$, two steady states exist for $4.8\leqslant {\it\alpha}\leqslant 5.0$. While one of them is associated with unstable eigenmodes, the other is stable to all infinitesimal perturbations. In this regime, irrespective of the initial conditions, the fully developed flow is steady and devoid of any instabilities.

scholarly journals Numerical Simulations for Nonlinear Waves Interaction with Multiple Perforated Quasi-Ellipse Caissons

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Xiaozhong Ren ◽  
Yuxiang Ma
Keyword(s):  
Incident Wave ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Navier Stokes ◽  
Wave Forces ◽  
Wave Runup ◽  
Cnoidal Waves ◽  
Navier Stokes Equations ◽  
Transverse Distance

A three-dimensional numerical flume is developed to study cnoidal wave interaction with multiple arranged perforated quasi-ellipse caissons. The continuity equation and the Navier-Stokes equations are used as the governing equation, and the VOF method is adopted to capture the free surface elevation. The equations are discretized on staggered cells and then solved using a finite difference method. The generation and propagation of cnoidal waves in the numerical flume are tested first. And the ability of the present model to simulate interactions between waves and structures is verified by known experimental results. Then cnoidal waves with varying incident wave height and period are generated and interact with multiple quasi-ellipse caissons with and without perforation. It is found that the perforation plays an effective role in reducing wave runup/rundown and wave forces on the caissons. The wave forces on caissons reduce with the decreasing incident wave period. The influence of the transverse distance of multiple caissons on wave forces is also investigated. A closer transverse distance between caissons can produce larger wave forces. But when relative adjacent distanceL/D(Lis the transverse distance andDis the width of the quasi-ellipse caisson) is larger than 3, the effect of adjacent distance is limited.

Navier-Stokes Predictions of the NREL Phase VI Rotor in the NASA Ames 80-By-120 Wind Tunnel

2002 ◽  
Author(s):  
N. N. So̸rensen ◽  
J. A. Michelsen ◽  
S. Schreck
Keyword(s):  
Wind Tunnel ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Navier Stokes ◽  
Dimensional Effects ◽  
Pressure Distributions ◽  
Shaft Torque ◽  
Reynolds Averaged Navier Stokes ◽  
Nrel Phase Vi ◽  
Good Agreement

The application of an incompressible Reynolds Averaged Navier-Stokes solver to cases from the NREL/NASA Ames wind tunnel test is described. Six cases of the NREL PHASE-VI rotor in the upwind configuration under zero yaw and zero degrees tip pitch are computed. Favorable comparison of the computed results with measurements in the form of shaft torque, root moments, spanwise force distributions, and pressure distributions are shown. The good agreement documents the feasibility of 3D CFD computations in connection with prediction of the performance of new rotors. Additionally it is shown how CFD computations can be used to determine the three dimensional effects in rotor flows.

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