scholarly journals Flettner Rotor Concept for Marine Applications: A Systematic Study

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
A. De Marco ◽  
S. Mancini ◽  
C. Pensa ◽  
G. Calise ◽  
F. De Luca
Keyword(s):  
Aspect Ratio ◽  
Systematic Study ◽  
Rotating Cylinder ◽  
Navier Stokes ◽  
Preliminary Design ◽  
Mathematical Tool ◽  
Drag Coefficients ◽  
Simulation Results ◽  
Marine Applications ◽  
Lift And Drag

The concept of Flettner rotor, a rotating cylinder immersed in a fluid current, with a top-mounted disk, has been analyzed by means of unsteady Reynolds averaged Navier-Stokes simulations, with the aim of creating a suitable tool for the preliminary design of the Flettner rotor as a ship’s auxiliary propulsion system. The simulation has been executed to evaluate the performance sensitivity of the Flettner rotor with respect to systematic variations of several parameters, that is, the spin ratio, the rotor aspect ratio, the effect of the end plates, and their dimensions. The Flettner rotor device has been characterized in terms of lift and drag coefficients, and these data were compared with experimental trends available in literature. A verification study has been conducted in order to evaluate the accuracy of the simulation results and the main sources of numerical uncertainty. All the simulation results were used to achieve a surrogate model of lift and drag coefficients. This model is an effective mathematical tool for the preliminary design of Flettner rotor. Finally, an example of assessment of the Flettner rotor performance as an auxiliary propulsion device on a real tanker ship is reported.

Three-Dimensional Numerical Prediction of the Hydrodynamic Loads and Motions of Offshore Structures

2000 ◽  
Vol 122 (4) ◽  
pp. 294-300 ◽  
Author(s):  
Karl W. Schulz ◽  
Yannis Kallinderis
Keyword(s):  
Flow Structure ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Structural Response ◽  
Offshore Structures ◽  
Three Dimensions ◽  
Navier Stokes ◽  
Hydrodynamic Loads ◽  
Drag Coefficients ◽  
Lift And Drag

A generalized numerical method for solution of the incompressible Navier-Stokes equations in three-dimensions has been developed. This solution methodology allows for the accurate prediction of the hydrodynamic loads on offshore structures, which is then combined with a rigid body structural response to address the flow-structure coupling which is often present in offshore applications. Validation results using this method are first presented for fixed structures which compare the drag coefficients of sphere and cylinder geometries to experimental measurements over a range of subcritical Reynolds numbers. Additional fixed structure results are then presented which explore the influence of aspect ratio effects on the lift and drag coefficients of a bare circular cylinder. Finally, the spanwise flow variations between a fixed and freely vibrating cylindrical structure are compared to demonstrate the ability of the flow-structure method to correctly predict correlation length increases for a vibrating structure. [S0892-7219(00)00904-3]

scholarly journals Effect of Aspect Ratio on Lift and Drag Coefficients of Cambered Plates

2000 ◽  
Vol 66 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Kengo Fukuda ◽  
Fuxiang Hu ◽  
Tadashi Tokai ◽  
Ko Matuda
Keyword(s):  
Aspect Ratio ◽  
Drag Coefficients ◽  
Lift And Drag

Force and Moment Measurements of Supercavitating Hydrofoils of Finite Span With Comparison to Theory

1975 ◽  
Vol 97 (4) ◽  
pp. 453-462
Author(s):  
P. Leehey ◽  
T. S. Stellinger
Keyword(s):  
Aspect Ratio ◽  
Asymptotic Expansions ◽  
Cavity Length ◽  
Large Aspect Ratio ◽  
Drag Coefficients ◽  
Finite Span ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Lift And Drag ◽  
Good Agreement

Measurements were made of lift, drag, and moment coefficients, and cavity length for aspect ratio 3 and 5 supercavitating hydrofoils of elliptical planform. These measurements are compared with theoretical predictions obtained from matching asymptotic expansions for large aspect ratio. Good agreement was obtained for lift and drag coefficients for angles of attack from 10 deg to 15 deg and for a wide range of cavity lengths. Theoretical moment coefficients were too large indicating the need for lifting surface corrections.

Experimental Force Coefficients for a Parametric Series of Spinnakers

2003 ◽  
Author(s):  
William C. Lasher ◽  
James R. Sonnenmeier ◽  
David R. Forsman ◽  
Cheng Zhang ◽  
Kenton White
Keyword(s):  
Aspect Ratio ◽  
Thrust Force ◽  
Statistical Design ◽  
Navier Stokes ◽  
Statistical Design Of Experiments ◽  
Force Coefficient ◽  
Force Coefficients ◽  
Drag Forces ◽  
Parametric Series ◽  
Lift And Drag

A parametric series of eight spinnaker models was built and tested in a wind tunnel according to the theory of statistical Design of Experiments. In these models, three sail shape parameters were varied - cross section camber ratio, sail aspect ratio, and sweep. Lift and drag forces were measured for a range of angles of attack, and the thrust force coefficient was determined as a function of apparent wind angle for each of the eight sails. It was found that flat spinnakers are faster than full spinnakers and that spinnakers with low sweep (more vertical) are faster than spinnakers with high sweep. This is consistent with general sailing practice, which maximizes projected sail area by pulling the pole back and down. The influence of aspect ratio on drag coefficient was small and within experimental error. A description of the sail shapes and corresponding force coefficients is presented for future validation of Reynolds Averaged Navier-Stokes simulations.

Analysis of the Flow Characteristics of Two Nonrotating Rotor Blades

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
R. P. J. O. M. van Rooij
Keyword(s):  
Aspect Ratio ◽  
Dominant Role ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Rotor Blades ◽  
Drag Coefficients ◽  
Wing Model ◽  
Stall Angle ◽  
Twisted Blade ◽  
Lift And Drag

The investigation focuses on the analysis of the airfoil segment performances along rotor blades in the parked configuration. In this research, wind tunnel experiments on two twisted blade geometries with different airfoils played a dominant role. These measurements were carried out by the Swedish Aeronautical Research Institute, former FFA, and by the American National Renewable Energy Laboratories (NREL) during the Unsteady Aerodynamic Experiment. The spans of the blades were 2.375m and 5m, the STORK 5 WPX and the NREL Phase VI blade, respectively. Five span locations (inboard, midspan, outboard, and tip regions) were considered and compared with the 2D airfoil characteristics. Wing model experiments with similar blade aspect ratio were included in the research. Furthermore, the commercial computational fluid dynamics code FLUENT was used for the validation and analysis of the spanwise lift and drag coefficients at four different pitch settings, 20deg, 30deg, 45deg, and 60deg. The computed pressure distributions compared reasonably well, but the derived lift and drag showed quite some differences with the blade measurements. The lift coefficients for the sections beyond the leading-edge stall angle of the STORK blade were larger than for the NREL blade and were close to that of a wing model with similar airfoil and aspect ratio. Lift and drag coefficients for the sections of the two blades were always much smaller than the 2D results. The drag values for both blades showed quite some agreement, and airfoil and blade dependency seemed to be small.

Investigation of the Possibilities of Rotating Cylinders as an Auxiliary Lift Device

1964 ◽  
Vol 68 (647) ◽  
pp. 777-780
Author(s):  
J. E. Chacksfield
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Experimental Studies ◽  
Rotating Cylinder ◽  
Test Results ◽  
Major Research ◽  
Drag Coefficients ◽  
Magnus Effect ◽  
The One ◽  
Gains And Losses

The following is an attempt to show the gains and losses achieved when a rotating cylinder is used to create additional lift during the take-off and landing of an aircraft.A hundred-year old theory lies behind the results (the “Magnus” effect), which, up to the present day has not been put to practical use in flight for increasing CL. Many proposals and tentative designs have been studied at major Research Establishments, notably A.V.A. Gottingen and the RAE but experimental studies on aircraft converted for the purpose have yet to be made.Limited test results show that the CL on a rotating cylinder can be as great as 15 providing that sufficient care is taken to approach infinite aspect ratio by means of end-plates on a high aspect ratio cylinder. The one great disadvantage with the cylinder is the high drag coefficients produced. However, there seems no reason why a fairing should not be placed in the wake to reduce the drag to that corresponding to a blunt-nosed thick aerofoil section.

scholarly journals The flow induced by a rotationally oscillating and translating circular cylinder

2000 ◽  
Vol 407 ◽  
pp. 123-144 ◽  
Author(s):  
S. C. R. DENNIS ◽  
P. NGUYEN ◽  
SERPIL KOCABIYIK
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Interesting Phenomenon ◽  
Navier Stokes Equations ◽  
Drag Coefficients ◽  
Small Times ◽  
High Reynolds ◽  
Lift And Drag

The temporal development of two-dimensional viscous incompressible flow induced by an impulsively started circular cylinder which performs time-dependent rotational oscillations about its axis and translates at right angles to this axis is investigated. The investigation is based on the solutions of the unsteady Navier–Stokes equations. A series expansion for small times is developed. The Navier–Stokes equations are also integrated by a spectral–finite difference method for moderate values of time for both moderate and high Reynolds numbers. The numerical method is checked with the results of the analytical solution. The effects of the Reynolds number and of the forcing Strouhal number S on the laminar asymmetric flow structure in the near-wake region are studied. The lift and drag coefficients are also extracted from numerical results. An interesting phenomenon has been observed both in the flow patterns and in the behaviour of drag coefficients for S = π/2 at Reynolds number R = 500 and is discussed. For comparison purposes the start-up flow is determined numerically at a low Reynolds number and is found to be in good agreement with previous experimental predictions.

scholarly journals RANS Simulations of Flow Past an DU-91-W2-250 Airfoil at High Reynolds Number

2018 ◽  
Vol 44 ◽  
pp. 00150
Author(s):  
Krzysztof Rogowski ◽  
Martin O.L. Hansen
Keyword(s):  
Reynolds Number ◽  
Navier Stokes ◽  
Transient Model ◽  
Drag Coefficients ◽  
Pressure Distributions ◽  
Sst Turbulence Model ◽  
Rans Simulations ◽  
High Reynolds ◽  
Lift And Drag ◽  
Good Agreement

This paper presents numerical results of the DU-91-W2-250 airfoil. Reynolds-averaged Navier–Stokes (RANS) simulations of the 2D profile are performed employing the Transient SST turbulence model. The airfoil was investigated for the Reynolds number of 6 106. Lift and drag coefficients are compared with the experimental data from LM Low Speed Wind Tunnel (LSWT). The results of lift and drag coefficients obtained using the SST Transient model are in a good agreement in comparison with the experiment in the angle of attack range from -10° to 10°. The static pressure distributions calculated by the SST Transition model are also in good agreement with the experiment.

On the performance of RANS turbulence models in predicting static stall over airfoils at high Reynolds numbers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
M. R. Nived ◽  
Bandi Sai Mukesh ◽  
Sai Saketha Chandra Athkuri ◽  
Vinayak Eswaran
Keyword(s):  
Turbulence Models ◽  
Cost Effective ◽  
Boussinesq Approximation ◽  
Navier Stokes ◽  
Drag Coefficients ◽  
Content Type ◽  
Rans Turbulence Models ◽  
Rans Models ◽  
Lift And Drag ◽  
Naca 0012

Purpose This paper aims to conduct, a detailed investigation of various Reynolds averaged Navier–Stokes (RANS) models to study their performance in attached and separated flows. The turbulent flow over two airfoils, namely, National Advisory Committee for Aeronautics (NACA)-0012 and National Aeronautics and Space Administration (NASA) MS(1)-0317 with a static stall setup at a Reynolds number of 6 million, is chosen to investigate these models. The pre-stall and post-stall regions, which are in the range of angles of attack 0°–20°, are simulated. Design/methodology/approach RANS turbulence models with the Boussinesq approximation are the most commonly used cost-effective models for engineering flows. Four RANS models are considered to predict the static stall of two airfoils: Spalart–Allmaras (SA), Menter’s k – ω shear stress transport (SST), k – kL and SA-Bas Cakmakcioglu modified (BCM) transition model. All the simulations are performed on an in-house unstructured-grid compressible flow solver. Findings All the turbulence models considered predicted the lift and drag coefficients in good agreement with experimental data for both airfoils in the attached pre-stall region. For the NACA-0012 airfoil, all models except the SA-BCM over-predicted the stall angle by 2°, whereas SA-BCM failed to predict stall. For the NASA MS(1)-0317 airfoil, all models predicted the lift and drag coefficients accurately for attached flow. But the first three models showed even further delayed stall, whereas SA-BCM again did not predict stall. Originality/value The numerical results at high Re obtained from this work, especially that of the NASA MS(1)-0317, are new to the literature in the knowledge of the authors. This paper highlights the inability of RANS models to predict the stall phenomenon and suggests a need for improvement in modeling flow physics in near- and post-stall flows.

Tail shapes lead to different propulsive mechanisms in the body/caudal fin undulation of fish

2020 ◽  
pp. 095440622096768
Author(s):  
Jialei Song ◽  
Yong Zhong ◽  
Ruxu Du ◽  
Ling Yin ◽  
Yang Ding
Keyword(s):  
Numerical Simulation ◽  
Aspect Ratio ◽  
High Efficiency ◽  
The Body ◽  
Caudal Fin ◽  
Fish Model ◽  
Swimming Efficiency ◽  
Simulation Results ◽  
Propulsive Mechanism ◽  
High Depth

In this paper, we investigate the hydrodynamics of swimmers with three caudal fins: a round one corresponding to snakehead fish ( Channidae), an indented one corresponding to saithe ( Pollachius virens), and a lunate one corresponding to tuna ( Thunnus thynnus). A direct numerical simulation (DNS) approach with a self-propelled fish model was adopted. The simulation results show that the caudal fin transitions from a pushing/suction combined propulsive mechanism to a suction-dominated propulsive mechanism with increasing aspect ratio ( AR). Interestingly, different from a previous finding that suction-based propulsion leads to high efficiency in animal swimming, this study shows that the utilization of suction-based propulsion by a high- AR caudal fin reduces swimming efficiency. Therefore, the suction-based propulsive mechanism does not necessarily lead to high efficiency, while other factors might play a role. Further analysis shows that the large lateral momentum transferred to the flow due to the high depth of the high- AR caudal fin leads to the lowest efficiency despite the most significant suction.

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