scholarly journals Wind-Induced Vibration of an Irregular Pentagon Lamella

2021 ◽  
Vol 1203 (3) ◽  
pp. 032111
Author(s):  
Norbert Jendzelovsky ◽  
Roland Antal
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Solution Process ◽  
Software Simulation ◽  
New Findings ◽  
Exact Position ◽  
Real Size ◽  
Size Model ◽  
Wind Induced Vibration

Abstract At present, there are increasingly encountering the use of lamellar structures, for example on the roofs of buildings, which, in addition to their visual function, also fulfil the function of reducing the flow of wind into the roof space. These structures are often designed as long and subtle structures and therefore their very common problem is unwanted vibration. In this article, the main focus is to show the methodology of the determination of the effects of wind on the lamella of the shape of an irregular pentagon. A real-size model made of steel with a total length of 2 m and a weight of 7.4 kg was used. Its size and shape were influenced by several factors which are specified in more detail in the paper. In the wind tunnel experiment, it was very important to ensure the exact position of the model and also to secure both ends of the model against shifting (to replicate fixed ends). Dynamic response of the structure in two directions together with wind speed were measured simultaneously. To investigate the wind effects by numerical analysis, fluid-structure interaction software simulation (FSI) on a full-size model was used. The main pitfall of the software solution was to get as close as possible to the conditions of the wind tunnel. The actual wind speed measured under laboratory conditions was used as the input wind speed for FSI simulation. The material of the model and the shape of the model was set in software simulation to be as close as possible to the real structure. Subsequently, other boundary conditions were set and the solution process was executed. The biggest problem, especially in terms of comparing the results of both approaches which greatly affected the results, was the very high stiffness of the model. Due to the extent and interconnectedness of results, findings are presented in more detail in the conclusions of the paper. The methodology of setting up a relatively complex FSI simulation, its results, as well as new findings that we came up with if the measurement of the dynamic effects of wind is the matter of interest are presented in this paper.

Accurate determination of reference wind speed and reference static pressure in wind tunnel tests

2019 ◽  
Vol 23 (3) ◽  
pp. 578-583
Author(s):  
YC He ◽  
JCK Cheung ◽  
QS Li ◽  
JY Fu
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Measurement Method ◽  
Static Pressure ◽  
Accurate Determination ◽  
Indirect Measurement ◽  
Measurement Methods ◽  
Wind Tunnel Experiments

The reference wind speed and reference static pressure are two key parameters for determining the testing results of wind tunnel experiments. Traditionally, the values of these parameters can be determined using direct measurement methods. However, such methods may suffer from less accuracy and inconvenience of operations. This article documents an indirect measurement method which, compared to the traditional methods, has the merits of higher accuracy and greater operational convenience. Examples are presented to demonstrate the main procedures of the method and typical findings by using the method in a boundary layer wind tunnel.

DETERMINATION OF MATERIAL CATALYCITY AT HIGH TEMPERATURES IN THE VAT-104 HYPERSONIC WIND TUNNEL

2014 ◽  
Vol 45 (1) ◽  
pp. 3-20 ◽  
Author(s):  
Ivan Vladimirovich Egorov ◽  
Boris Evgen'evich Zhestkov ◽  
Vladimir Viktorovich Shvedchenko
Keyword(s):  
Wind Tunnel ◽  
High Temperatures ◽  
Hypersonic Wind Tunnel

Extremely Gusty Winds from a Viewpoint of Aerodynamic Force

2020 ◽  
Author(s):  
Junji Maeda ◽  
Takashi Takeuchi ◽  
Eriko Tomokiyo ◽  
Yukio Tamura
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Rise Time ◽  
Aerodynamic Force ◽  
Step Function ◽  
Object Size ◽  
Aerodynamic Forces ◽  
Wind Force ◽  
Wind Observation

To quantitatively investigate a gusty wind from the viewpoint of aerodynamic forces, a wind tunnel that can control the rise time of a step-function-like gust was devised and utilized. When the non-dimensional rise time, which is calculated using the rise time of the gusty wind, the wind speed, and the size of an object, is less than a certain value, the wind force is greater than under the corresponding steady wind. Therefore, this wind force is called the “overshoot wind force” for objects the size of orbital vehicles in an actual wind observation. The finding of the overshoot wind force requires a condition of the wind speed recording specification and depends on the object size and the gusty wind speed.

The effect of cytochalasin D on preprophase band organization in root tip cells of Allium

1992 ◽  
Vol 103 (4) ◽  
pp. 989-998 ◽  
Author(s):  
E.P. Eleftheriou ◽  
B.A. Palevitz
Keyword(s):  
Preprophase Band ◽  
Cytochalasin D ◽  
Root Tip ◽  
Average Width ◽  
Exact Position ◽  
The Relationship ◽  
Tip Cells ◽  
Root Tip Cells ◽  
Control Samples

The relationship between microfilaments (Mfs) and microtubules (Mts) in the organization of the preprophase band (PPB) was investigated in Allium root tip cells subjected to treatment with cytochalasin D (CD). Mts and Mfs were visualized by indirect immunofluorescence and various parameters such as PPB width were analyzed quantitatively. In control samples, the PPB first appears as a wide Mt band that progressively narrows to an average width of 4 micrometre in mid-prophase. Randomly oriented Mfs are present throughout the cytoplasm of most interphase control cells. Preprophase and prophase cells, however, contain cortical Mfs arranged parallel to the PPB. The Mfs initially occupy much of the cortex but in most cells they progressively become restricted to an area wider than the PPB. In the presence of CD, the PPB fails to narrow and remains at least two-fold wider than in control cells. PPB width expressed as a percentage of nuclear or cell length also increases compared to controls. Widening is concentration dependent, and the effect of 10 micromolar CD is near maximal only 15 min after application of the drug. This rapid response suggests that a rebroadening of already condensed PPBs takes place. After as little as 15 min in CD, Mfs are replaced by many small specks and rods. Dual localizations of both Mts and Mfs show that prophase cells contain broad PPBs without Mfs. The rapid disorganization of Mfs, by CD, therefore coincides with the rebroadening of PPBs. CD-treated cells in metaphase, anaphase and telophase contain larger actin aggregates at the poles, as previously reported. The results indicate that Mfs play an important role in the narrowing of the PPB, which in turn is essential for determination of the exact position of the plane of division. They also indicate that movement of intact Mts is important in PPB organization.

Determination of rated wind speed for maximum annual energy production of variable speed wind turbines

2017 ◽  
Vol 205 ◽  
pp. 781-789 ◽  
Author(s):  
Ahmad Sedaghat ◽  
Arash Hassanzadeh ◽  
Jamaloddin Jamali ◽  
Ali Mostafaeipour ◽  
Wei-Hsin Chen
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Energy Production ◽  
Variable Speed

Study on the Relation Between Side Ratios of Rectangular Cross Sections and Secondary Vortices at Trailing Edge in Motion-Induced Vortex Excitation

2017 ◽  
Author(s):  
Kazutoshi Matsuda ◽  
Kusuo Kato ◽  
Kouki Arise ◽  
Hajime Ishii
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Cross Sections ◽  
Leading Edge ◽  
Trailing Edge ◽  
Wind Speeds ◽  
Smoke Flow ◽  
Flow Visualizations ◽  
Institute Of Technology ◽  
Secondary Vortices

According to the results of conventional wind tunnel tests on rectangular cross sections with side ratios of B/D = 2–8 (B: along-wind length (m), D: cross-wind length (m)), motion-induced vortex excitation was confirmed. The generation of motion-induced vortex excitation is considered to be caused by the unification of separated vortices from the leading edge and secondary vortices at the trailing edge [1]. Spring-supported test for B/D = 1.18 was conducted in a closed circuit wind tunnel (cross section: 1.8 m high×0.9 m wide) at Kyushu Institute of Technology. Vibrations were confirmed in the neighborhoods of reduced wind speeds Vr = V/fD = 2 and Vr = 8 (V: wind speed (m/s), f: natural frequency (Hz)). Because the reduced wind speed in motion-induced vortex excitation is calculated as Vr = 1.67×B/D = 1.67×1.18 = 2.0 [1], vibrations around Vr = 2 were considered to be motion-induced vortex excitation. According to the smoke flow visualization result for B/D = 1.18 which was carried out by the authors, no secondary vortices at the trailing edge were formed, although separated vortices from the leading edge were formed at the time of oscillation at the onset wind speed of motion-induced vortex excitation, where aerodynamic vibrations considered to be motion-induced vortex excitation were confirmed. It was suggested that motion-induced vortex excitation might possibly occur in the range of low wind speeds, even in the case of side ratios where secondary vortices at trailing edge were not confirmed. In this study, smoke flow visualizations were performed for ratios of B/D = 0.5–2.0 in order to find out the relation between side ratios of rectangular cross sections and secondary vortices at trailing edge in motion-induced vortex excitation. The smoke flow visualizations around the model during oscillating condition were conducted in a small-sized wind tunnel at Kyushu Institute of Technology. Experimental Reynolds number was Re = VD/v = 1.6×103. For the forced-oscillating amplitude η, the non-dimensional double amplitudes were set as 2η/D = 0.02–0.15. Spring-supported tests were also carried out in order to obtain the response characteristics of the models.

The Influence of Complex Dynamic Phenomena Caused by Wind Action on Behaviour of Transportation Pipelines

2013 ◽  
Vol 837 ◽  
pp. 170-174
Author(s):  
Gheorghe Pintilie
Keyword(s):  
Wind Speed ◽  
Aerodynamic Force ◽  
Mathematical Expression ◽  
Periodic Variation ◽  
Operating Conditions ◽  
Frequency Variation ◽  
Wind Action ◽  
Karman Vortex ◽  
Dynamic Phenomena

The main transportation pipelines are subjected to complex stresses resulting from the nature and state of the transported material, the operating conditions, and the environmental factors and so on. Thus, the stress in the pipe wall is generated and influenced by the pressure, the temperature and the mass of the transported fluid, by the weight of the pipe, the ambient temperature and in certain periods of time by the wind speed. In this paper are presented dynamic phenomena generated by wind flow and their effect on the magistrate transportation pipelines. The content of the paper presents an detailed analysis regarding the regimes in which is developing the force generated by Karman vortex and the situation when resonance phenomena are developed. The study presents a mathematical model that describes the dynamic phenomena generated by the wind action, determining the mathematical expression of the aerodynamic force that act on the normal direction to the wind speed. This force is having a periodic variation, its size and the frequency variation is dependent on the wind speed. Some methods are proposed in order to decrease the wind influence on the lifetime of transportation pipelines. The main results of the study are: determination of the speed range for which the dynamic phenomena have a high influence on the pipeline lifetime; determination of the real conditions that can lead to sharp rises of the pipe deformations; determination of the pipeline lifetime reduction under development of dynamic loads.

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