Gravity wave interaction with multiple submerged artificial reefs

2020 ◽  
pp. 147509022096084
Author(s):  
KG Vijay ◽  
S Neelamani ◽  
CS Nishad ◽  
T Sahoo
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Gravity Wave ◽  
Wave Interaction ◽  
Hydrodynamic Performance ◽  
Artificial Reefs ◽  
Intermediate Water ◽  
Model Based ◽  
Rate Of Increase ◽  
Base Width

In the present study, gravity wave interaction with a series of submerged artificial permeable reefs is analysed within the framework of linearised water wave theory. For wave past porous walls of the artificial reefs, a quadratic pressure drop is assumed to account for the wave energy dissipation due to the changes in wave height. The physical problem is handled for a solution using a numerical model based on the iterative multi-domain boundary element method and the developed numerical model is validated with known results in the literature. The iterative model is compared with the numerical model based on linear pressure drop boundary condition (i.e., Darcy law). The study reveals that the wave transmission reduces with the increase in the number of reef units. It is demonstrated that the transmission coefficient can be reduced to less than 0.5 when the number of reef units is greater than or equal to three for a relative height greater than 0.7, reef porosities less than 20% and for 0.4<k0h<3.0. Bragg reflection is observed when the porosity is in the range of 0 to 10% and above which the recurrent nature of wave reflection gradually fades away due to dissipation effects. The number of peaks occurring in the shallow and intermediate water depths is equal to the number of reef units wherein the maxima occur at the first frequency. A relative increase in the base width improves the energy losses but the rate of increase in energy loss decreases. The scattering coefficient pattern is oscillatory when the relative spacing between the barriers is varied and their hydrodynamic performance is invariant for higher relative base width.

scholarly journals Numerical Simulation and Hydrodynamic Performance Predicting of 2 Two-Dimensional Hydrofoils in Tandem Configuration

2021 ◽  
Vol 9 (5) ◽  
pp. 462
Author(s):  
Yuchen Shang ◽  
Juan J. Horrillo
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Resource Constraints ◽  
Lift Coefficient ◽  
Parametric Method ◽  
Experimental Results ◽  
Hydrodynamic Performance ◽  
Tandem Configuration ◽  
Artificial Neural Network Ann ◽  
Naca 0012

In this study we investigated the performance of NACA 0012 hydrofoils aligned in tandem using parametric method and Neural Networks. We use the 2D viscous numerical model (STAR-CCM+) to simulate the hydrofoil system. To validate the numerical model, we modeled a single NACA 0012 configuration and compared it to experimental results. Results are found in concordance with the published experimental results. Then two NACA 0012 hydrofoils in tandem configuration were studied in relation to 788 combinations of the following parameters: spacing between two hydrofoils, angle of attack (AOA) of upstream hydrofoil and AOA of downstream hydrofoil. The effects exerted by these three parameters on the hydrodynamic coefficients Lift coefficient (CL), Drag Coefficient (CD) and Lift-Drag Ratio (LDR), are consistent with the behavior of the system. To establish a control system for the hydrofoil craft, a timely analysis of the hydrodynamic system is needed due to the computational resource constraints, analysis of a large combination and time consuming of the three parameters established. To provide a broader and faster way to predict the hydrodynamic performance of two hydrofoils in tandem configuration, an optimal artificial neural network (ANN) was trained using the large combination of three parameters generated from the numerical simulations. Regression analysis of the output of ANN was performed, and the results are consistent with numerical simulation with a correlation coefficient greater than 99.99%. The optimized spacing of 6.6c are suggested where the system has the lowest CD while obtaining the highest CL and LDR. The formula of the ANN was then presented, providing a reliable predicting method of hydrofoils in tandem configuration.

Forced Harmonic Response of Grouped Blade Systems: Part II—Application

1996 ◽  
Vol 118 (1) ◽  
pp. 137-145 ◽  
Author(s):  
L. F. Wagner ◽  
J. H. Griffin
Keyword(s):  
Numerical Model ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Turbine Blades ◽  
Modal Identification ◽  
Harmonic Response ◽  
Model Based ◽  
Grouped Blades ◽  
Flexible Disk ◽  
Symmetric Structures

The vibration of grouped blades on a flexible disk should, for purposes of economy and clarity of modal identification, be analyzed using procedures developed for cyclically symmetric structures. In this paper, a numerical model, based on the theory of cyclically symmetric structures, is applied to the vibration analysis, and in particular, the harmonic response, of a flexible disk supporting a number of groups, or packets, of turbine blades. Results are presented to show variations in the modal participation factors as a function of such parameters as disk flexibility, blade density, and the total number of assembled groups. It is also shown that many characteristics of the system spectra of natural frequencies are strongly dependent on the number of blade groups.

scholarly journals Model-Based Optimization of Velocity Strategy for Lightweight Electric Racing Cars

2018 ◽  
Vol 2018 ◽  
pp. 1-20 ◽  
Author(s):  
Mirosław Targosz ◽  
Wojciech Skarka ◽  
Piotr Przystałka
Keyword(s):  
Numerical Model ◽  
Energy Efficient ◽  
Atmospheric Conditions ◽  
Vehicle Model ◽  
Model Based ◽  
Race Track ◽  
Functional Features ◽  
Race Conditions ◽  
Vehicle Dynamic Model ◽  
And Control

The article presents a method for optimizing driving strategies aimed at minimizing energy consumption while driving. The method was developed for the needs of an electric powered racing vehicle built for the purposes of the Shell Eco-marathon (SEM), the most famous and largest race of energy efficient vehicles. Model-based optimization was used to determine the driving strategy. The numerical model was elaborated in Simulink environment, which includes both the electric vehicle model and the environment, i.e., the race track as well as the vehicle environment and the atmospheric conditions. The vehicle model itself includes vehicle dynamic model, numerical model describing issues concerning resistance of rolling tire, resistance of the propulsion system, aerodynamic phenomena, model of the electric motor, and control system. For the purpose of identifying design and functional features of individual subassemblies and components, numerical and stand tests were carried out. The model itself was tested on the research tracks to tune the model and determine the calculation parameters. The evolutionary algorithms, which are available in the MATLAB Global Optimization Toolbox, were used for optimization. In the race conditions, the model was verified during SEM races in Rotterdam where the race vehicle scored the result consistent with the results of simulation calculations. In the following years, the experience gathered by the team gave us the vice Championship in the SEM 2016 in London.

scholarly journals RANS MODELLING OF CROSS-SHORE SEDIMENT TRANSPORT AND MORPHODYNAMICS IN THE SWASH-ZONE

2020 ◽  
pp. 14
Author(s):  
Joost Kranenborg ◽  
Geert Campmans ◽  
Niels Jacobsen ◽  
Jebbe van der Werf ◽  
Robert McCall ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Navier Stokes ◽  
Swash Zone ◽  
Rans Equations ◽  
Model Based ◽  
Numerical Studies ◽  
Reynolds Averaged Navier Stokes ◽  
Averaged Models

Most numerical studies of sediment transport in the swash zone use depth-averaged models. However, such models still have difficulty predicting transport rates and morphodynamics. Depth-resolving models could give detailed insight in swash processes but have mostly been limited to hydrodynamic predictions. We present a depth-resolving numerical model, based on the Reynolds Averaged Navier-Stokes (RANS) equations, capable of modelling sediment transport and morphodynamics in the swash zone.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/PB8Vs0LJq88

Numerical Simulation of Wave Interaction With a Pair of Fixed Large Tandem Cylinders Subjected to Regular, Non-Breaking Waves

2021 ◽  
Author(s):  
M. Mohseni ◽  
C. Guedes Soares
Keyword(s):  
Numerical Model ◽  
Wave Field ◽  
Circular Cross Section ◽  
Wave Interaction ◽  
Breaking Waves ◽  
Wave Loading ◽  
Two Phase ◽  
Wave Regime ◽  
Wave Amplification ◽  
Vof Model

Abstract The wave interaction with cylinders placed in proximity results in significant modification of the wave field, wave-induced processes, and wave loading. The evaluation of such a complex wave regime and accurate assessment of the wave loading requires an efficient and accurate numerical model. Concerning the wave scattering types identified by Swan et al. (2015) and lateral progressive edge waves, this paper presents the application of a two-phase Computational Fluid Dynamics (CFD) model to carry out a detailed investigation of nonlinear wave field surrounding a pair of columns placed in the tandem arrangement in the direction of wave propagation and corresponding harmonics. The numerical analysis is conducted using the Unsteady Reynolds-Averaged Navier-Stokes/VOF model based on the OpenFOAM framework combined with the olaFlow toolbox for wave generation/absorption. For the simulations, the truncated cylinders are assumed vertical and surface piercing with a circular cross-section subjected to regular, non-breaking fifth-order Stokes waves propagating with moderate steepness in deep water. Primarily, the numerical model is validated with experimental data provided by ITTC (OEC)[1] for a single cylinder. Future, the given simulations are conducted for different centre-to-centre distances between the tandem large cylinders. The results show the evolution of a strong wave diffraction pattern and consequently high wave amplification harmonics around cylinders are apparent.

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