Numerical Investigation of the Unsteady Flow at High Reynolds Number Over a Marine Riser With Helical Strakes

2006 ◽  
Author(s):  
Antonio Pinto ◽  
Riccardo Broglia ◽  
Andrea Di Mascio ◽  
Emilio F. Campana ◽  
Pierpaolo Rocco
Keyword(s):  
Fluid Dynamics ◽  
Unsteady Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Numerical Code ◽  
Three Dimensional Model ◽  
Analysis Phase ◽  
Helical Strakes ◽  
Advanced Analysis ◽  
High Reynolds

Prediction of Vortex-Induced Vibrations (VIV) is one of the main topics in the design of deepwater risers. The understanding and modelling of the complex fluid-structure interaction requires advanced analysis techniques coupling, in a correct manner, both structural and fluid dynamics aspects. This study aims to develop, optimise and calibrate a numerical code to provide reliable results within a reasonable analysis timeframe and without, or very limited, need of experimental verification. For this purpose, the unsteady Reynolds Average Navier-Stokes (RANS) code χnavis is applied to solve a typical riser VIV problem and compute the three-dimensional riser-fluid dynamics interaction. During a preliminary analysis phase, the two-dimensional (2-D) flow past (i) a bare circular cylinder and (ii) a straked riser at high Reynolds numbers is simulated (different incidences flow/strake vanes are analysed). Numerical results are validated and calibrated against published test data. The core analysis phase is then focused on the numerical investigation of the unsteady flow over a three-dimensional (3-D) helical strake. In this phase, the three-dimensional flow field, turbulent structures and response frequency patterns are analysed. Spectral analysis of data is performed to identify carrier frequencies deemed to be critical due to the induced vibration of the whole structure, and helical strakes efficiency in reducing the riser vibrations is also addressed. Finally, comparison between numerical and experimental results shows that the complexity of a three-dimensional model is indeed compensated by a significantly improved accuracy of the obtained results.

Numerical Simulation of Flow around a Cylinder under Different Reynolds Number

2014 ◽  
Vol 543-547 ◽  
pp. 434-440
Author(s):  
Qiang Liu ◽  
Wei Xie ◽  
Wen Yang Duan ◽  
Chang Hong Hu
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Initial Field ◽  
Fine Grid ◽  
Flow Around A Cylinder ◽  
Wall Functions ◽  
High Reynolds ◽  
Les Model

Based on fully structured grids parallel numerical simulations of flow around a cylinder under different Reynolds number are carried out. Two-dimensional and three-dimensional models are established at the same time under specific Reynolds number, and further analyze of three-dimensional flow characteristics as well as the generated influence to overall physical quantities are presented. In order to explore efficient high Reynolds number turbulence models, a comparative research of the LES model without wall functions and the Spalart-Allmaras turbulence model is carried out. In order to improve the computational efficiency, a domain decomposition parallel computing strategy is used, and a calculation strategy that results of coarse grid was assigned to fine grid as initial field value by 3D linear interpolation is presented. Simulation results show that: Drag coefficient and Strouhal number have very good consistency with the experimental data, which verifies the correctness of the calculation method; Even if at low Reynolds number (200≤Re≤300), using a three-dimensional model is still necessary; While in the high Reynolds number stage, compared to LES model without wall functions, Spalart-Allmaras model is more applicable and more efficient.

Vortex Suppression Efficiency of Discontinuous Helicoidal Fins

2007 ◽  
Author(s):  
Antonio Pinto ◽  
Riccardo Broglia ◽  
Elena Ciappi ◽  
Andrea Di Mascio ◽  
Emilio F. Campana ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Computational Time ◽  
Reynolds Number Flow ◽  
Flow Past A Cylinder ◽  
Helical Strakes ◽  
Unsteady Rans ◽  
Number Flow ◽  
Offshore Industry ◽  
Good Trade ◽  
High Reynolds

Vortex-Induced Vibration (VIV) is one of the most demanding areas in the offshore industry, and detailed investigation of the fluid-structure interaction is becoming fundamental for designing new structures able to reduce VIV phenomenon. To carry on such analysis, and get reliable results in term of global coefficients, the correct modelling of turbulence, boundary layer, and separated flows is required. Nonetheless, the more accurate is the simulation, the more costly is the computation. Unsteady RANS simulations provide a good trade-off between numerical accuracy and computational time. This paper presents the analysis of the flow past a cylinder with several three-dimensional helical fins at high Reynolds number. Flow field, vortical structures, and response frequency patterns are analysed. Spectral analysis of data is performed to identify carrier frequencies, deemed to be critical due to the induced vibration of the whole structure. Finally, helical strakes efficiency in reducing the riser vibrations is also addressed, through direct consideration on the carrier shedding frequency.

A three-dimensional model for analyzing the effects of salmon redds on hyporheic exchange and egg pocket habitat

2009 ◽  
Vol 66 (12) ◽  
pp. 2157-2173 ◽  
Author(s):  
Daniele Tonina ◽  
John M. Buffington
Keyword(s):  
Fluid Dynamics ◽  
Hydraulic Conductivity ◽  
Dissolved Oxygen ◽  
Oxygen Content ◽  
Three Dimensional ◽  
Hyporheic Exchange ◽  
Dimensional Model ◽  
Dynamics Model ◽  
Three Dimensional Model ◽  
Channel Hydraulics

A three-dimensional fluid dynamics model is developed to capture the spatial complexity of the effects of salmon redds on channel hydraulics, hyporheic exchange, and egg pocket habitat. We use the model to partition the relative influences of redd topography versus altered hydraulic conductivity (winnowing of fines during spawning) on egg pocket conditions for a simulated pool–riffle channel with a redd placed at the pool tail. Predictions show that altered hydraulic conductivity is the primary factor for enhancing hyporheic velocities and dissolved oxygen content within the egg pocket. Furthermore, the simulations indicate that redds induce hyporheic circulation that is nested within that caused by pool–riffle topography and that spawning-related changes in hyporheic velocities and dissolved oxygen content could create conditions suitable for incubation in locations that otherwise would be unfavorable (reinforcing the notion that salmonids actively modify their environment in ways that may be beneficial to their progeny).

Bubble Behavior at an Uneven Wall

2016 ◽  
Author(s):  
H. Shmueli ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Bubble Growth ◽  
Three Dimensional ◽  
Grid Method ◽  
Numerical Code ◽  
Interface Tracking ◽  
Bubble Behavior ◽  
Three Dimensional Model ◽  
Surface Geometry ◽  
Initial State ◽  
Channel Orientation

The present study deals with single bubble growth on an uneven wall. A model problem is defined and solved using a three-dimensional numerical simulation. The wall has the shape of a triangular cavity and feature vortices. The equations solved in the present study are based on macro region modelling of the bubble alone and describe its growth from the initial state to detachment from the surface and consequent motion. The model includes a simultaneous solution of conservation equations for the liquid and gaseous phases, in conjunction with three-dimensional interface tracking. The latter is achieved using the level-set method. The numerical modeling includes the multi-grid method. The complete three-dimensional model is discretized using an original in-house numerical code realized in MATLAB. Different cases of bubble growth on the triangular cavity walls are investigated. The main conclusion from the calculations is that the bubble shape and its growth rate strongly depend on its location and on the channel orientation. New features, not possible for flat walls and special for this case, are revealed and discussed. It is demonstrated that under certain conditions, the bubble is obstructed by the surface geometry. It is also shown how a growing bubble affects the flow field inside a cavity, interacting with the vortex structure.

Anatomically based three-dimensional model of airways to simulate flow and particle transport using computational fluid dynamics

2005 ◽  
Vol 98 (3) ◽  
pp. 970-980 ◽  
Author(s):  
Caroline van Ertbruggen ◽  
Charles Hirsch ◽  
Manuel Paiva
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Deposition ◽  
Gas Flow ◽  
Three Dimensional ◽  
Bronchial Tree ◽  
Inspiratory Flow ◽  
Three Dimensional Model ◽  
Viscous Pressure ◽  
Curved Ducts

We have studied gas flow and particle deposition in a realistic three-dimensional (3D) model of the bronchial tree, extending from the trachea to the segmental bronchi (7th airway generation for the most distal ones) using computational fluid dynamics. The model is based on the morphometrical data of Horsfield et al. (Horsfield K, Dart G, Olson DE, Filley GF, and Cumming G. J Appl Physiol 31: 207–217, 1971) and on bronchoscopic and computerized tomography images, which give the spatial 3D orientation of the curved ducts. It incorporates realistic angles of successive branching planes. Steady inspiratory flow varying between 50 and 500 cm3/s was simulated, as well as deposition of spherical aerosol particles (1–7 μm diameter, 1 g/cm3 density). Flow simulations indicated nonfully developed flows in the branches due to their relative short lengths. Velocity flow profiles in the segmental bronchi, taken one diameter downstream of the bifurcation, were distorted compared with the flow in a simple curved tube, and wide patterns of secondary flow fields were observed. Both were due to the asymmetrical 3D configuration of the bifurcating network. Viscous pressure drop in the model was compared with results obtained by Pedley et al. (Pedley TJ, Schroter RC, and Sudlow MF. Respir Physiol 9: 387–405, 1970), which are shown to be a good first approximation. Particle deposition increased with particle size and was minimal for ∼200 cm3/s inspiratory flow, but it was highly heterogeneous for branches of the same generation.

The Numerical Investigation of Cracking Areas under Nonuniform Settlements of the Construction

2014 ◽  
Vol 472 ◽  
pp. 141-145
Author(s):  
Maria L. Bartolomey ◽  
Igor N. Shardakov ◽  
Nikolai A. Trufanov
Keyword(s):  
Numerical Model ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Strained State ◽  
Dimensional Model ◽  
Three Dimensional Model

We investigate the tensely-strained state of three-dimensional construction at the measured settlements of the foundation. The numerical model of the construction is developed within the limits of the theory of the plates bending and rectilinear rods, it allows to reveal dangerous places in the strength members particularly in the interfloor plate. The three-dimensional model of the dangerous area is developed, which allows to define the level of damaging the plates material. Settlements levels leading to first cracks and full destruction of the investigated area of the construction are defined.

scholarly journals Numerical Simulation of a Propeller-Type Turbine for In-Pipe Installation

2021 ◽  
Vol 83 (1) ◽  
pp. 1-16
Author(s):  
Oscar Darío Monsalve Cifuentes ◽  
Jonathan Graciano Uribe ◽  
Diego Andrés Hincapié Zuluaga
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Pipe Wall ◽  
Three Dimensional ◽  
Hydraulic Efficiency ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Mesh Independence ◽  
Using Data

In this work, a 76 mm diameter propeller-type turbine is numerically investigated using a parametric study and computational fluid dynamics. The three-dimensional model of the turbine is modeled using data available in the bibliography. A mesh independence study is carried out utilizing a tetrahedron-based mesh with inflation layers around the turbine blade and the pipe wall. The best efficiency point is determined by the maximum hydraulic efficiency of 64.46 %, at a flow rate of 9.72x10-3 m3/s , a head drop of 1.76 m, and a mechanical power of 107.83 W. Additionally, the dimensionless distance y+, pressure, and velocity contours are shown.

Secondary Flow in a Strong Curved Converging Channel

2005 ◽  
Vol 9 (3) ◽  
pp. 58-63
Author(s):  
L.X. L.X. ◽  
B. Wang ◽  
F.H. She
Keyword(s):  
Secondary Flow ◽  
Mesh Generation ◽  
Flow Characteristic ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Rotor Spinning ◽  
Converging Channel ◽  
Transfer Channel ◽  
High Reynolds

A three-dimensional model is developed to evaluate the effect of secondary flow generated from strongly bent duct profiles and turbulent flow of high Reynolds number on fibre movement in a bent channel. The fibre configuration is more complex in a three-dimensional model with the introduction of secondary flow. The strategies of mesh generation for threedimensional problems are discussed. The flow characteristic in the transfer-channel of a rotor spinning machine is predicted.

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