A model on the turbulent wind field over wind-waves in curvilinear co-ordinates

1978 ◽  
Vol 34 (4) ◽  
pp. 117-128 ◽  
Author(s):  
Hiroshi Ichikawa
Keyword(s):  
Wind Field ◽  
Wind Waves ◽  
Turbulent Wind ◽  
Turbulent Wind Field

Temporal evolution of rain drops’ velocities in a turbulent wind field

2020 ◽  
Author(s):  
Auguste Gires ◽  
Ioulia Tchiguirinskaia ◽  
Daniel Schertzer
Keyword(s):  
Drag Force ◽  
Wind Field ◽  
Temporal Evolution ◽  
Fall Velocity ◽  
Turbulent Wind ◽  
Wide Range ◽  
Rain Drop ◽  
Initial Work ◽  
Rain Drops ◽  
Turbulent Wind Field

<p>It is commonly assumed that a rain drop falls vertically at a speed equal to its so called “terminal fall velocity” which has been determined both empirically and theoretically by equating the net gravity force with the drag force due to the fact the drop is moving in the atmosphere. This velocity depends on the size of the drop, usually characterized by its equivolumic diameter.</p><p>In this investigation we study the temporal evolution of the velocity of a rain drop falling through turbulent wind field. The equation governing a rain drop motion relates the acceleration to the forces of gravity and buoyancy along with the drag force. The latter depends non-linearly on the instantaneous relative velocity between the drop and the local wind. The whole complexity of the resulting behaviour arises from this feature. In this work, the drag force is expressed in a standard way with the help of a drag coefficient, which is itself determined according to a Reynolds number. It should be mentioned that in this initial work, the strong assumption that the drops remain spherical in their fall is made. It is well known that its not true for drops greater than typically 1-2 mm which tend to become oblate, and potential effects on the results will be discussed.</p><p>An explicit numerical scheme is implemented to solve this equation for 3+1D turbulent wind field to study the temporal evolution of the velocities as well as the trajectories of rain drops over few hundreds of meters. The variations in both space and time of the wind field are simulated with the help of a Universal Multifractals which are a framework that has been widely used to characterize and simulate geophysical fields extremely variable over a wide range of scales such as wind.</p><p>Temporal multifractal analysis are then carried out on the simulated drop velocity, which enables to characterize the behaviour of drops according to their size, and notably a scale below which turbulent eddies have a limited impact on their motion. Finally the consequences of these findings on rainfall remote sensing with radars are briefly discussed.</p>

scholarly journals A CFD Study for Floating Offshore Wind Turbine Aerodynamics in Turbulent Wind Field

2021 ◽  
Author(s):  
Yang Zhou ◽  
Qing Xiao ◽  
Yuanchuan Liu ◽  
Atilla Incecik ◽  
Christophe Peyrard ◽  
...  
Keyword(s):  
Wind Field ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wind Effect ◽  
Turbulent Wind ◽  
Wind Turbine Aerodynamics ◽  
Wind Turbulence ◽  
Power Outputs ◽  
Cfd Method ◽  
Turbulent Wind Field

Abstract The present study is aimed at investigating the turbulent wind effect on FOWT through the usage of a high-fidelity computational fluid dynamics (CFD) method. This method is believed to resolve the wind field, giving us a more in-depth examination into the aerodynamics of FOWT. The work is built upon our previous studies on the modelling of a coupled aero-hydro-mooring FOWT system under regular wave and uniform wind. In the present study, we replaced the previously uniform wind with a temporal and spatial variable turbulent wind field using a time-varying spectrum. The turbulent wind is generated with Mann’s wind turbulence model while the Von Karman wind spectrum is used to represent wind turbulence. The present study shows that when turbulent wind is present, there may be fluctuations of the rotor thrust and power outputs, causing the non-uniform wake region. Despite this, both the dynamic motions and the mooring tensions of the floater are not significantly influenced by the wind turbulence under the present inflow wind conditions.

scholarly journals Non-Stationary Turbulent Wind Field Simulation of Long-Span Bridges Using the Updated Non-Negative Matrix Factorization-Based Spectral Representation Method

2019 ◽  
Vol 9 (24) ◽  
pp. 5506
Author(s):  
Zidong Xu ◽  
Hao Wang ◽  
Han Zhang ◽  
Kaiyong Zhao ◽  
Hui Gao ◽  
...  
Keyword(s):  
Wind Field ◽  
Spectral Representation ◽  
Wind Fields ◽  
Turbulent Wind ◽  
Long Span Bridges ◽  
Long Span ◽  
Spectral Representation Method ◽  
Representation Method ◽  
Turbulent Wind Field ◽  
Non Negative Matrix Factorization

Numerical simulation of the turbulent wind field on long-span bridges is an important task in structural buffeting analysis when it comes to the system non-linearity. As for non-stationary extreme wind events, some efforts have been paid to update the classic spectral representation method (SRM) and the fast Fourier transform (FFT) has been introduced to improve the computational efficiency. Here, the non-negative matrix factorization-based FFT-aided SRM has been updated to generate not only the horizontal non-stationary turbulent wind field, but also the vertical one. Specifically, the evolutionary power spectral density (EPSD) is estimated to characterize the non-stationary feature of the field-measured wind data during Typhoon Wipha at the Runyang Suspension Bridge (RSB) site. The coherence function considering the phase angles is utilized to generate the turbulent wind fields for towers. The simulation accuracy is validated by comparing the simulated and target auto-/cross-correlation functions. Results show that the updated method performs well in generating the non-stationary turbulent wind field. The obtained wind fields will provide the research basis for analyzing the non-stationary buffeting behavior of the RSB and other wind-sensitive structures in adjacent regions.

scholarly journals Characterisation of Small-Scale Atmospheric Wind-Field Structures Using Coherent Wind Lidar With Short Pulses

2020 ◽  
Vol 237 ◽  
pp. 06002
Author(s):  
D. T. Michel ◽  
M. Valla ◽  
D. Goular ◽  
L. Lombard ◽  
A. Dolfi-Bouteyre ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Wind Field ◽  
Small Scale ◽  
Short Pulses ◽  
Turbulent Wind ◽  
Wind Lidar ◽  
Scale Structures ◽  
Turbulent Wind Field ◽  
Small Scale Structures

A lidar design has been developed at ONERA that uses short square pulses (75 ns) to have a small spatial resolution (22.5 m) and be able to measure small-scale atmospheric wind-field structures. Results show that the system is able to resolve the small-scale structures of vortices and to measure wind field structures of a turbulent wind field down to ~20 m.

Simulation of a Turbulent Wind Field for HAWT

2006 ◽  
Vol 30 (6) ◽  
pp. 503-509
Author(s):  
Chen Yan ◽  
Zhang Zhicheng ◽  
Ye Zhiquan
Keyword(s):  
Wind Field ◽  
Turbulent Wind ◽  
Turbulent Wind Field

Large Eddy Simulation of Wind Field around Large-Span Cantilevered Roofs

2010 ◽  
Vol 163-167 ◽  
pp. 3914-3917
Author(s):  
Chong Yang Li ◽  
De Min Wei
Keyword(s):  
Large Eddy Simulation ◽  
Coherent Structures ◽  
Wind Field ◽  
Wind Pressure ◽  
Wind Engineering ◽  
Turbulent Wind ◽  
Large Span ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbulent Wind Field

Large-span cantilevered roofs are wind sensitive structures, this paper presents the finding of large eddy simulation(LES) of turbulent wind field around large-span cantilevered roofs with grandstand in atmosphere boundary layer. For a typical horizontal cantilevered roof, the wind pressure is researched in fluid mechanic view, the large scales of wind motion are computed explicitly while the small scales are modeled by LES, the contours of wind pressure and velocity are present to reveal the coherent structures. Some general issues related to LES in wind engineering are discussed also.

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