Numerical Simulation using RANS-based Tools for America’s Cup Design

2003 ◽  
Author(s):  
Geoff Cowles ◽  
Nicola Parolini ◽  
Mark L. Sawley
Keyword(s):  
Design Process ◽  
Water Surface ◽  
Navier Stokes ◽  
Computational Fluid Dynamics Simulations ◽  
America’S Cup ◽  
Dynamics Simulations ◽  
École Polytechnique ◽  
Cup Design ◽  
Cup Drawing

The application of Computational Fluid Dynamics simulations based on the Reynolds Averaged Navier- Stokes (RANS) equations to the design of sailing yachts is becoming more commonplace, particularly for the America's Cup. Drawing on the experience of the Ecole Polytechnique Fédérale de Lausanne as Official Scientific Advisor to the Alinghi Challenge for the America’s Cup 2003, the role of RANS-based codes in the yacht design process is discussed. The strategy for simulating the hydrodynamic flow around the boat appendages is presented. Two different numerical methods for the simulation of wave generation on the water surface are compared. In addition, the aerodynamic flow around different sail configurations is investigated. The benefits to the design process as well as its limitations are discussed. Practical matters, such as manpower and computational requirements, are also considered.

scholarly journals Numerical investigation of a small water turbine used for the power supply of underwater vehicles

2018 ◽  
Vol 10 (6) ◽  
pp. 168781401878365 ◽  
Author(s):  
Zhaoyong Mao ◽  
Jingang Bai
Keyword(s):  
Stokes Equations ◽  
Underwater Vehicles ◽  
Geometric Parameters ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Sliding Mesh ◽  
Small Water ◽  
Water Turbine ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

The development of underwater vehicles is facing the problem of sustainable energy supply. This study introduces a small water turbine, the Lenz turbine, for energy generation from the ocean currents which will provide energy for the underwater vehicles. Computational fluid dynamics simulations of the effect of geometric parameters, including the blade radius, chord length, and pitch angle, on the performance of the turbine are conducted. The Reynolds-Averaged Navier–Stokes equations are numerically solved with a sliding mesh method. Thirteen sets of tests in total are performed at different values of tip-speed ratios. The tests are divided into three groups to study the effect of the three parameters mentioned above, separately. The obtained power coefficients, coefficient of torque, and the dynamic torque on a blade are then compared in each group of tests. Pressure contours and velocity contours are given to explain the reason how the geometric parameters affect the rotor performance.

scholarly journals A Comparison of Experimental and Computational Heat Transfer Results for a Leading Edge Impingement System

2018 ◽  
Vol 3 (4) ◽  
pp. 23
Author(s):  
Robert Pearce ◽  
Peter Ireland ◽  
Ed Dane ◽  
Janendra Telisinghe
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
High Heat ◽  
Navier Stokes ◽  
Spatially Resolved ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Leading edge impingement systems are increasingly being used for high pressure turbine blades in gas turbine engines, in regions where very high heat loads are encountered. The flow structure in such systems can be very complex and high resolution experimental data is required for engine-realistic systems to enable code validation and optimal design. This paper presents spatially resolved heat transfer distributions for an engine-realistic impingement system for multiple different hole geometries, with jet Reynolds numbers in the range of 13,000–22,000. Following this, Reynolds-averaged Navier-Stokes computational fluid dynamics simulations are compared to the experimental data. The experimental results show variation in heat transfer distributions for different geometries, however average levels are primarily dependent on jet Reynolds number. The computational simulations match the shape of the distributions well however with a consistent over-prediction of around 10% in heat transfer levels.

Simulations of an Air-Ventilated Strut Crossing Water Surface at Variable Yaw Angles

2018 ◽  
Author(s):  
Konstantin I. Matveev ◽  
Miles P. Wheeler ◽  
Tao Xing
Keyword(s):  
Water Surface ◽  
Free Water ◽  
Suction Side ◽  
Complex Flow ◽  
Air Ventilation ◽  
History Of ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Lift Control ◽  
Good Agreement

Hydrodynamic devices intended to produce lift, control actions, or propulsion can be prone to air ventilation when operating near the free water surface. The atmospheric air may propagate to the low-pressure zones around these devices located under the nominal water level. This often leads to performance degradation of hydrodynamic systems. Modeling of air-ventilated flows is challenging due to complex flow nature and many factors in play. In this study, the computational fluid dynamics simulations are carried out for a surface-piercing strut at different yaw angles. At small yaw angles, the strut underwater surfaces remain wetted, whereas at large yaw and sufficiently high Froude numbers the suction side becomes air ventilated. At the intermediate yaw angles, both wetted and ventilated flow regimes are possible, and the existence of a specific state depends on the history of the process. The present computational results demonstrate good agreement with available experimental data.

scholarly journals Boxfish swimming paradox resolved: forces by the flow of water around the body promote manoeuvrability

2015 ◽  
Vol 12 (103) ◽  
pp. 20141146 ◽  
Author(s):  
S. Van Wassenbergh ◽  
K. van Manen ◽  
T. A. Marcroft ◽  
M. E. Alfaro ◽  
E. J. Stamhuis
Keyword(s):  
Drag Reduction ◽  
High Performance ◽  
Flow Direction ◽  
Current Theory ◽  
The Body ◽  
Hydrodynamic Drag ◽  
Aerodynamic Design ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

The shape of the carapace protecting the body of boxfishes has been attributed an important hydrodynamic role in drag reduction and in providing automatic, flow-direction realignment and is therefore used in bioinspired design of cars. However, tight swimming-course stabilization is paradoxical given the frequent, high-performance manoeuvring that boxfishes display in their spatially complex, coral reef territories. Here, by performing flow-tank measurements of hydrodynamic drag and yaw moments together with computational fluid dynamics simulations, we reverse several assumptions about the hydrodynamic role of the boxfish carapace. Firstly, despite serving as a model system in aerodynamic design, drag-reduction performance was relatively low compared with more generalized fish morphologies. Secondly, the current theory of course stabilization owing to flow over the boxfish carapace was rejected, as destabilizing moments were found consistently. This solves the boxfish swimming paradox: destabilizing moments enhance manoeuvrability, which is in accordance with the ecological demands for efficient turning and tilting.

scholarly journals Aerodynamic optimisation of the rear wheel fairing of the land speed record vehicle BLOODHOUND SSC

2016 ◽  
Vol 120 (1228) ◽  
pp. 930-955
Author(s):  
J. Townsend ◽  
B. Evans ◽  
T. Tudor
Keyword(s):  
Design Space ◽  
Aerodynamic Drag ◽  
Ground Plane ◽  
Rear Wheel ◽  
Navier Stokes ◽  
High Dimensional ◽  
Aerodynamic Properties ◽  
Function Design ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

ABSTRACTThis paper describes the design optimisation study used to aerodynamically optimise the fairings that cover the rear wheels of the Land Speed Record vehicle, BLOODHOUND SuperSonic Car (SSC). Initially, using a Design of Experiments approach, a series of Computational Fluid Dynamics simulations were performed on a set of parametric geometries, with the goal of identifying a fairing geometry that was aerodynamically optimised for the target speed of 1,000 mph. Several aerodynamic properties were considered when deciding what design objectives the fairings would be optimised to achieve; chief amongst these was the minimisation of aerodynamic drag. A parallel, finite-volume Navier–Stokes solver was used on unstructured meshes in order to simulate the complex aerodynamic behaviour of the flow around the vehicle’s rear wheel structure, which involved a rotating wheel, and shockwaves generated close to a supersonic rolling ground plane. It was found that the simple response surface fitting approach did not sufficiently capture the complexities of the optimisation objective function across the high-dimensional design space. As a result, a Nelder–Mead optimisation approach was implemented, coupled with Radial Basis Function design space interpolation to find the final optimised fairing design. This paper presents the results of the optimisation study as well as indicating the likely impact this optimisation will have on the ultimate top speed of this unique vehicle.

scholarly journals Understanding the Role of Pattern Geometry on Nanofiltration Threshold Flux

Membranes ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 445
Author(s):  
Anna Malakian ◽  
Zuo Zhou ◽  
Lucas Messick ◽  
Tara N. Spitzer ◽  
David A. Ladner ◽  
...  
Keyword(s):  
Membrane Surface ◽  
Cross Flow ◽  
Cake Filtration ◽  
Cross Flow Filtration ◽  
Colloidal Fouling ◽  
Computational Fluid Dynamics Simulations ◽  
Flow Filtration ◽  
Dynamics Simulations ◽  
The Relationship

Colloidal fouling can be mitigated by membrane surface patterning. This contribution identifies the effect of different pattern geometries on fouling behavior. Nanoscale line-and-groove patterns with different feature sizes were applied by thermal embossing on commercial nanofiltration membranes. Threshold flux values of as-received, pressed, and patterned membranes were determined using constant flux, cross-flow filtration experiments. A previously derived combined intermediate pore blocking and cake filtration model was applied to the experimental data to determine threshold flux values. The threshold fluxes of all patterned membranes were higher than the as-received and pressed membranes. The pattern fraction ratio (PFR), defined as the quotient of line width and groove width, was used to analyze the relationship between threshold flux and pattern geometry quantitatively. Experimental work combined with computational fluid dynamics simulations showed that increasing the PFR leads to higher threshold flux. As the PFR increases, the percentage of vortex-forming area within the pattern grooves increases, and vortex-induced shielding increases. This study suggests that the PFR should be higher than 1 to produce patterned membranes with maximal threshold flux values. Knowledge generated in this study can be applied to other feature types to design patterned membranes for improved control over colloidal fouling.

Experimental and Numerical Investigation of a Miniature Additively Manufactured Vortex Tube

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Gregory Wallace ◽  
Carl Bunge ◽  
Jacob Leachman ◽  
Konstantin I. Matveev
Keyword(s):  
Additive Manufacturing ◽  
Vortex Tube ◽  
Complex Geometry ◽  
Pressure Ratio ◽  
Navier Stokes ◽  
Cooling Power ◽  
Variable Diameter ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Vortex Tubes

Abstract Ranque–Hilsch vortex tubes are simple devices that can produce a cooling effect using compressed air. A key advantage of vortex tubes is the lack of moving solid parts; however, their efficiencies are relatively low. The present study focuses on the development of a miniature variable-diameter tube using additive manufacturing. A metal-based 3D printing technique was utilized to fabricate this vortex tube monolithically. Computational fluid dynamics simulations employing software star-ccm+ with a compressible Reynolds-Averaged Navier–Stokes (RANS) approach and the elliptic-blending lag k-epsilon turbulence model have been applied to model thermofluid processes inside the vortex tube, to good agreement with the experiment. A temperature decrease of 13.3 °C and a cooling power of approximately 4 W were experimentally achieved with a pressure ratio of 4 in the air at normal conditions. This result shows promise for the goal of utilizing additive manufacturing to design and build complex-geometry vortex tubes intended for use with cryogenic fluids.

scholarly journals On the role of the Knudsen layer in rapid granular flows

2007 ◽  
Vol 585 ◽  
pp. 73-92 ◽  
Author(s):  
J. E. GALVIN ◽  
C. M. HRENYA ◽  
R. D. WILDMAN
Keyword(s):  
Heat Flux ◽  
Granular Flows ◽  
Order Theory ◽  
Knudsen Layer ◽  
Navier Stokes ◽  
Experimental Systems ◽  
Theoretical Predictions ◽  
Flux Measurements ◽  
Dynamics Simulations

A combination of molecular dynamics simulations, theoretical predictions and previous experiments are used in a two-part study to determine the role of the Knudsen layer in rapid granular flows. First, a robust criterion for the identification of the thickness of the Knudsen layer is established: a rapid deterioration in Navier–Stokes order prediction of the heat flux is found to occur in the Knudsen layer. For (experimental) systems in which heat flux measurements are not easily obtained, a rule-of-thumb for estimating the Knudsen layer thickness follows, namely that such effects are evident within 2.5 (local) mean free paths of a given boundary. Secondly, comparisons of simulation and experimental data with Navier–Stokes order theory are used to provide a measure as to when Knudsen-layer effects become non-negligible. Specifically, predictions that do not account for the presence of a Knudsen layer appear reliable for Knudsen layers collectively composing up to 20% of the domain, whereas deterioration of such predictions becomes apparent when the domain is fully comprised of the Knudsen layer.

Sign in / Sign up

Export Citation Format

Share Document