scholarly journals Drag and lift coefficients of ellipsoidal particles under rarefied flow conditions

2022 ◽  
Vol 105 (1) ◽  
Author(s):  
C. Livi ◽  
G. Di Staso ◽  
H. J. H. Clercx ◽  
F. Toschi
Keyword(s):  
Flow Conditions ◽  
Rarefied Flow ◽  
Drag And Lift Coefficients ◽  
Ellipsoidal Particles ◽  
Drag And Lift

Simplified Aerodynamic Loading Model for Non-Production Conditions for Floating Wind Systems Design

2021 ◽  
Author(s):  
Armando Alexandre ◽  
Raffaello Antonutti ◽  
Theo Gentils ◽  
Laurent Mutricy ◽  
Pierre Weyne
Keyword(s):  
Wind Speed ◽  
Coupled Model ◽  
Systems Design ◽  
Simplified Model ◽  
Aerodynamic Loads ◽  
Drag And Lift Coefficients ◽  
Aerodynamic Loading ◽  
Yaw Bearing ◽  
Drag And Lift ◽  
Turbine Model

Abstract Floating wind is now entering a commercial-stage, and there are a significant number of commercial projects in countries like France, Japan, UK and Portugal. A floating wind project is complex and has many interdependencies and interfaces. During all stages of the project several participants are expected to use a numerical model of the whole system and not only the part the participant has to design. Examples of this are the mooring and floater designer requiring a coupled model of the whole system including also the wind turbine, the operations team requiring a model of the system to plan towing and operations. All these stakeholders require a coupled model where the hydrodynamics, aerodynamics and structural physics of the system are captured with different levels of accuracy. In this paper, we will concentrate on a simplified model for the aerodynamic loading of the turbine in idling and standstill conditions that can be easily implemented in a simulation tool used for floater, mooring and marine operations studies. The method consists of using a subset of simulations at constant wind speed (ideally close to the wind speed required for the simulations) run on a detailed turbine model on a rigid tower and fixed foundation — normally run by the turbine designer. A proxy to the aerodynamic loads on the rotor and nacelle (RNA) is to take the horizontal yaw bearing loads. The process is then repeated for a range of nacelle yaw misalignments (for example every 15° for 360°). A look-up table with the horizontal yaw bearing load for the range of wind-rotor misalignments investigated is created. The simplified model of the aerodynamic loads on the RNA consists of a fixed blade (or wing) segment located at the hub, where aerodynamic drag and lift coefficients can be specified. Using the look-up tables created using the detailed turbine model, drag and lift coefficients are estimated as a function of the angle between the rotor and the wind direction. This representation of the aerodynamic loading on the RNA was then verified against full-field turbulent wind simulations in fixed and floating conditions using a multi-megawatt commercial turbine. The results for the parameters concerning the floater, mooring and marine operations design were monitored (e.g. tower bottom loads, offsets, pitch, mooring tensions) for extreme conditions and the errors introduced by this simplified rotor are generally lower than 4%. This illustrates that this simplified representation of the turbine can be used by the various parties of the project during the early stages of the design, particularly when knowing the loading within the RNA and on higher sections of the tower is not important.

Research on Aerodynamic Characteristics of a Simplified SUV Model

2013 ◽  
Vol 275-277 ◽  
pp. 603-606 ◽  
Author(s):  
Xing Jun Hu ◽  
Lei Liao ◽  
Jing Yu Wang ◽  
Li Min Fu
Keyword(s):  
Drag Coefficient ◽  
Pressure Distribution ◽  
Aerodynamic Characteristics ◽  
Drag And Lift Coefficients ◽  
Transition Radius ◽  
Drag And Lift ◽  
Underbody Diffuser

The aerodynamics characteristics of square Mira model were researched by simulation, the drag coefficient and the aerodynamic characteristics around model were achieved with analysis of velocity and pressure distribution. Based on results, the angle of rear wind window, the angle of underbody diffuser and the front transition radius were changed, the drag and lift coefficients were achieved. The conclusions provide reference for how to reduce drag coefficient of SUV

scholarly journals Numerical Simulation of Flow Control around a Circular Cylinder by Installing a Wedge-Shaped Device Upstream

2019 ◽  
Vol 7 (12) ◽  
pp. 422 ◽  
Author(s):  
Xiaoshuang Han ◽  
Jie Wang ◽  
Bo Zhou ◽  
Guiyong Zhang ◽  
Soon-Keat Tan
Keyword(s):  
Circular Cylinder ◽  
Cavity Mode ◽  
Wake Flow ◽  
Side Length ◽  
Length Ratio ◽  
Drag And Lift Coefficients ◽  
Spacing Ratio ◽  
Wake Patterns ◽  
Drag And Lift ◽  
Sudden Jump

The effect of a triangular wedge upstream of a circular cylinder has been investigated, and the findings are presented herein. The triangular wedge is equilateral in plan form, and the Reynolds number based on the diameter of the main cylinder is approximately 200. Contours of vorticity clearly show that two entirely different wake patterns exist between the wedge and the main cylinder. There also exists a critical spacing ratio and side length ratio at which the wake flow pattern shifts from one within the cavity mode to one within the wake impingement mode. For a relatively small side length ratio of l w / D = 0.20 and 0.27, where the side length refers to the length of one side of the triangular wedge, the drag and lift coefficients decrease monotonically with the spacing ratio. There is a sudden jump of the drag and lift coefficients at larger side length ratios of l w / D = 0.33 and 0.40. This study shows that at a spacing ratio of L/D = 2.8 (where L is the distance between the vertex of the wedge and the center of the cylinder) and a wedge side length of l w / D = 0.40, the reduction of the amplitude of lift and mean drag coefficient on the main cylinder are 71.9% and 60.1%, respectively.

scholarly journals Gas permeability in rarefied flow conditions for characterization of mineral membrane support

2020 ◽  
Vol 79 ◽  
pp. 44-53 ◽  
Author(s):  
C. Savaro ◽  
J.P. Bonnet ◽  
M.V. Johansson ◽  
P. Perrier ◽  
I. Graur ◽  
...  
Keyword(s):  
Gas Permeability ◽  
Flow Conditions ◽  
Rarefied Flow

FLOW EFFECT AROUND TWO SQUARE CYLINDERS ARRANGED SIDE BY SIDE USING LATTICE BOLTZMANN METHOD

2008 ◽  
Vol 19 (11) ◽  
pp. 1683-1694 ◽  
Author(s):  
YONG RAO ◽  
YUSHAN NI ◽  
CHAOFENG LIU
Keyword(s):  
Lattice Boltzmann Method ◽  
Vortex Shedding ◽  
Lattice Boltzmann ◽  
Reynolds Numbers ◽  
Small Space ◽  
Flip Flop ◽  
Drag And Lift Coefficients ◽  
Square Cylinders ◽  
Drag And Lift ◽  
Boltzmann Method

The flow around two square cylinders arranged side by side has been investigated through lattice Boltzmann method under different Reynolds numbers and various space ratios (s = d/D, d is the separation distance between two cylinders, D is the characteristic length) from 1.0, 1.1 to 2.7, including 18 space ratios. It is found that the flip-flop regime occurs at small space ratios and the synchronized regime occurs at large space ratios. Wide and narrow wakes at small spacing are formed and intermittently change behind the cylinders, and the biased flow in the gap is bistable. The frequency of vortex shedding is different in two wakes. The upper frequency is smaller than the lower frequency for small space ratios (s < 1.4), and the time-averaged drag and lift coefficients of cylinders are also different. When the space ratios increase, two distinct vortex streets occur behind the cylinders, and the frequency of vortex shedding is almost equal in two wakes. Also the difference of time-averaged drag and lift coefficients of the cylinders decreases with the increase in space ratios; in this case the flow shows synchronized regime. The transition between flip-flop and synchronized regimes occurs at s = 1.5. When s < 1.5, the flow shows flip-flop regime; otherwise, it shows synchronized regime. When s = 2.0 and 2.5, the curves for the time-averaged drag and lift coefficient with different Reynolds numbers are smooth. When s = 1.5 and 1.8, the curves are also smooth under Re ≤ 140, but that will be fluctuant under Re > 140 because of the nonlinear interaction between the wakes, and the instability of flow becomes stronger with the increase in Reynolds numbers. On the other hand, the vortex shedding type from the cylinder occurs in-phase when s < 2.5 and s = 2.5 for Re < 190, whereas that occurs anti-phase when s = 2.5 for Re ≥190. In addition, the pressure varies a little on the left surfaces and greatly on the right surfaces of both cylinders with the increase in Reynolds number at s = 2.5.

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