scholarly journals A Nonlinear Computational Model of Floating Wind Turbines

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Ali Nematbakhsh ◽  
David J. Olinger ◽  
Gretar Tryggvason
Keyword(s):  
Wind Turbines ◽  
Dynamic Models ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Immersed Boundary ◽  
Navier Stokes Equations ◽  
Structured Grid ◽  
Gyroscopic Effects

The dynamic motion of floating wind turbines is studied using numerical simulations. The full three-dimensional Navier–Stokes equations are solved on a regular structured grid using a level set method for the free surface and an immersed boundary method for the turbine platform. The tethers, the tower, the nacelle, and the rotor weight are included using reduced-order dynamic models, resulting in an efficient numerical approach that can handle nearly all the nonlinear hydrodynamic forces on the platform, while imposing no limitation on the platform motion. Wind speed is assumed constant, and rotor gyroscopic effects are accounted for. Other aerodynamic loadings and aeroelastic effects are not considered. Several tests, including comparison with other numerical, experimental, and grid study tests, have been done to validate and verify the numerical approach. The response of a tension leg platform (TLP) to different amplitude waves is examined, and for large waves, a nonlinear trend is seen. The nonlinearity limits the motion and shows that the linear assumption will lead to overprediction of the TLP response. Studying the flow field behind the TLP for moderate amplitude waves shows vortices during the transient response of the platform but not at the steady state, probably due to the small Keulegan–Carpenter number. The effects of changing the platform shape are considered, and finally, the nonlinear response of the platform to a large amplitude wave leading to slacking of the tethers is simulated.

scholarly journals A Nonlinear Computational Model for Floating Wind Turbines

2012 ◽  
Author(s):  
Ali Nematbakhsh ◽  
David J. Olinger ◽  
Gretar Tryggvason
Keyword(s):  
Wind Turbines ◽  
Dynamic Models ◽  
Stokes Equations ◽  
Computational Cost ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Current Approach ◽  
Immersed Boundary ◽  
Tension Leg Platform ◽  
Gyroscopic Effects

The dynamic motion of floating wind turbines is studied using computational simulations. The full three-dimensional Navier-Stokes equations are solved on a regular structured grid, using a level set method for the free surface and modified immersed boundary method to model the turbine platform. The tethers, the tower, the nacelle and the rotor weight are include using reduced order dynamic models, resulting in an efficient numerical approach. Wind is modeled as a constant thrust force. Other aerodynamic loading, rotor gyroscopic effects, and aeroelastic effects are not considered in the current study. The response of a tension leg platform to moderate amplitude waves is examined. By using the current approach, nearly all the nonlinear and viscose effects can be considered while keeping the computational cost reasonable. The model is applied to a Tension Leg Platform (TLP) consisting of a ballasted cylindrical tank.

scholarly journals Exploratory Simulation of Solar Granules: How Sharp is the Convection/Radiation Transition?

1998 ◽  
Vol 185 ◽  
pp. 217-218
Author(s):  
Kwing L. Chan ◽  
Y.C. Kim
Keyword(s):  
Stokes Equations ◽  
Fluid Layer ◽  
Three Dimensional ◽  
Thermal Relaxation ◽  
3D Models ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Space Resolution ◽  
Radiation Transition

Currently, the most successful direct simulation of the solar granules (and the convection/radiation transition layer) is the three-dimensional (3D) model computed by Stein and Nordlund (1989). So far, there is no other similar 3D models available for comparison [however, see Ludwig et al. (1997) for a recent 2D calculation]. We are developing an alternative numerical approach to simulate the 3D radiation hydrodynamics of this layer. In this approach, the Eddington approximation is used to handle the radiation rather than solving the radiative transfer equations along rays, and the ADISM method (Chan and Wolff 1982) which solves the Navier Stokes equations in conservative forms is used to speed up the thermal relaxation of the fluid layer. We are in the process of testing the numerical accuracy of the codes. This paper summarizes the results of a test that illustrate the effects of vertical space resolution on the mean profiles of some important quantities.

scholarly journals Two- and Three-Dimensional Numerical Experiments Representing Two Limiting Cases of an In-Line Pair of Finger Seal Components

2003 ◽  
Vol 9 (3) ◽  
pp. 171-179 ◽  
Author(s):  
M. J. Braun ◽  
V. V. Kudriavtsev ◽  
B. M. Steinetz ◽  
M. P. Proctor
Keyword(s):  
Solid Mechanics ◽  
Stokes Equations ◽  
Fluid Model ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Line Pair ◽  
Navier Stokes Equations ◽  
Flowing Fluid ◽  
Elemental Component

The work presented here concerns the numerical development and simulation of the flow, pressure patterns, and motion of a pair of fingers arranged one behind the other and axially aligned in line. The fingers represent the basic elemental component of a finger seal and form a tight seal around the rotor. Yet their flexibility allows compliance with rotor motion and, in a passive-adaptive mode, compliance with the hydrodynamic forces induced by the flowing fluid. Although this article does not treat the actual staggered configuration of a finger seal, the in-line arrangement represents a first step toward that final goal. The numerical two-dimensional (axial-radial) and three-dimensional results presented herein were obtained using a commercial package (CFD-ACE+). Both models use an integrated numerical approach, which couples the hydrodynamic fluid model based on Navier-Stokes equations to the solid mechanics code that models the compliance of the fingers.

Non-inertial multiblock Navier-Stokes calculation for hovering rotor flowfields using relative velocity approach

2001 ◽  
Vol 105 (1049) ◽  
pp. 379-389 ◽  
Author(s):  
B. Zhong ◽  
N. Qin
Keyword(s):  
Relative Velocity ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Structured Grid ◽  
Cylindrical Grid ◽  
Relative Variable ◽  
Model Rotor

AbstractA three dimensional Navier-Stokes solver is presented for calculating the hovering rotor flowfield using Osher's approximate Riemann solver. The Navier-Stokes equations are recast in the attached blade relative system using relative flow velocities as variables. Multiblock techniques are used to obtain a structured grid around the blade. A modified MUSCL scheme is proposed to alleviate the inaccuracy in the discretisation of the relative variable formulation. The calculations are performed for a two-bladed model rotor on C-H, O-O and C-H cylindrical grid topologies respectively. Computational solutions show reasonably good agreement with the experimental data for different lifting cases. The difficulty and suitability of different grid topologies for capturing the tip vortex is illustrated. The differences between Euler and Navier-Stokes solutions and between wake modelling and wake capturing approaches are also revealed. The results indicate that the relative velocity approach can give reasonable results for hovering rotor flowfields if due care is taken in minimising possible numerical errors.

Effectiveness of multiple jets for a finned large slenderness ratio missile in supersonic crossflows

2021 ◽  
pp. 095441002098689
Author(s):  
Longfei Li ◽  
Jiangfeng Wang ◽  
Ding Wang ◽  
Tianpeng Yang ◽  
Jiawei Li
Keyword(s):  
Stokes Equations ◽  
Slenderness Ratio ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Amplification Factors ◽  
Structured Grid ◽  
Sonic Jet ◽  
Multiple Jets ◽  
Jet Plumes

The reaction control system with multiple lateral jets shows great advantages in agility and maneuverability for supersonic air vehicles. Interactions among sonic jet plumes, X-shape fins, and supersonic crossflow at Mach 4.5 and Reynolds number 3.8 × 107 are numerically studied considering different number of jets for a large slenderness ratio missile with 7 jet exits. Three-dimensional Reynolds-averaged Navier–Stokes equations closed by Spalart–Allmaras turbulence model for the structured grid are validated and solved. The overall force and moment amplification factors of configurations with and without fins are analyzed and compared. Moreover, the force and moment amplification factors on fins and ratio of force and moment on fins are proposed and discussed to measure the jet effectiveness contributed from fins. The number of jet plumes is under consideration for all cases. Results show that the increment of effectiveness decreases as the number of jets increases for the finned configuration. Fins can significantly improve the jet effectiveness with more than 70% force and 50% moment increment, which shows great advantages to the jet effectiveness as well as the overall aerodynamic performance.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

The inlet flow structure of a conceptual open-nose supersonic drone

2021 ◽  
pp. 095441002098304
Author(s):  
Eiman B Saheby ◽  
Xing Shen ◽  
Anthony P Hays ◽  
Zhang Jun
Keyword(s):  
Flow Structure ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Computational Fluid Dynamic Simulation ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Aerodynamic Efficiency ◽  
Performance Effects

This study describes the aerodynamic efficiency of a forebody–inlet configuration and computational investigation of a drone system, capable of sustainable supersonic cruising at Mach 1.60. Because the whole drone configuration is formed around the induction system and the design is highly interrelated to the flow structure of forebody and inlet efficiency, analysis of this section and understanding its flow pattern is necessary before any progress in design phases. The compression surface is designed analytically using oblique shock patterns, which results in a low drag forebody. To study the concept, two inlet–forebody geometries are considered for Computational Fluid Dynamic simulation using ANSYS Fluent code. The supersonic and subsonic performance, effects of angle of attack, sideslip, and duct geometries on the propulsive efficiency of the concept are studied by solving the three-dimensional Navier–Stokes equations in structured cell domains. Comparing the results with the available data from other sources indicates that the aerodynamic efficiency of the concept is acceptable at supersonic and transonic regimes.

Sign in / Sign up

Export Citation Format

Share Document