scholarly journals Experimental Investigation on Glaze Ice Accretion and Its Influence on Aerodynamic Characteristics of Pipeline Suspension Bridges

2020 ◽  
Vol 10 (20) ◽  
pp. 7167 ◽  
Author(s):  
Haiyan Yu ◽  
Fuyou Xu ◽  
Mingjie Zhang ◽  
Aoqiu Zhou
Keyword(s):  
Inclination Angle ◽  
Aerodynamic Force ◽  
Aerodynamic Characteristics ◽  
Climatic Conditions ◽  
Suspension Bridges ◽  
Ice Accretion ◽  
Atmospheric Conditions ◽  
Force Coefficients ◽  
Size And Shape ◽  
Ice Accretions

Pipeline suspension bridges may experience ice accretion under special atmospheric conditions, and the aerodynamic characteristics of the bridges may be modified by the ice accretion. Under some specific climatic conditions of freezing rain, the dependencies of the ice size and shape on the icing duration and some structural properties (including pipeline diameter, inclination angle of wind hanger, inclination angle and size of section steel, and girder geometry) were experimentally investigated in a refrigerated precipitation icing laboratory. Typical ice accretions on pipelines, wind hangers, section steels, and girders of pipeline suspension bridges are summarized. Then the effects of some selected ice accretions on aerodynamic force coefficients of a bridge girder were further investigated through wind tunnel tests. The ice size and shape on the pipeline were closely related to the pipeline diameter and icing duration. The engineering geometric models of ice accretion on pipelines were extracted. The ice shape and size on wind hangers and section steels changed with their inclination angles. The aerodynamic force coefficients of a girder with ice accretion were much higher than those of an ice-free one. The results can provide references for simulating the ice accretion and further evaluating the effect of ice accretion on the aerodynamics of pipeline suspension bridges.

Effects of Ice Thickness on the Aerodynamic Characteristics of Crescent Shape Iced Conductors

2012 ◽  
Vol 166-169 ◽  
pp. 2696-2703 ◽  
Author(s):  
Dong Yan ◽  
Wen Juan Lou ◽  
Ming Feng Huang ◽  
Wei Lin
Keyword(s):  
Lift Force ◽  
Aerodynamic Force ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Ice Thickness ◽  
Force Curve ◽  
Force Coefficients ◽  
Variation Patterns ◽  
The Difference ◽  
Force Characteristics

Aerodynamic characteristics of iced conductors were investigated by the wind tunnel test. Under the homogeneous turbulence of 5% intensity, aerodynamic force coefficients of single and bundled conductors were obtained at wind angles of 0°~180°. The variation patterns of aerodynamic forces on the iced conductors with respect to wind angels of attack were systematically studied for the ice thickness of 0.25, 0.5, 0.75 and 1 times of the conductor diameter. The difference of aerodynamic force characteristics for single and bundled conductors were identified and discussed. Based on the Den Hartog and Nigol’s mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed. The results show that lift and torsion force coefficients reach peak values at wind angles of 15°~20°. For bundled conductors, lift force curve is approximately agreed with the curve of single conductor. Drag force coefficients were smaller than these of single conductor at some wind angles. There are noticeably differences of torsion coefficients existed between bundled conductors and single conductor. According to two classical galloping mechanisms, wind angles of 15°~30°are critical for the galloping of iced conductors with crescent shapes.

Numerical Simulation on Aerodynamic Characteristics of Road Vehicles on Bridges under Cross Winds

2013 ◽  
Vol 774-776 ◽  
pp. 241-247
Author(s):  
Y. Han ◽  
S. Q. Shu ◽  
D. Tan
Keyword(s):  
Numerical Simulation ◽  
Aerodynamic Force ◽  
Aerodynamic Characteristics ◽  
Wind Loads ◽  
Aerodynamic Forces ◽  
Road Vehicles ◽  
Force Coefficients ◽  
The Road ◽  
Cfd Method

The aerodynamic force coefficients of road vehicles under wind loads depend on not only the shapes of vehicles but also those of infrastructures, such as a bridge. Therefore, study of the aerodynamic characteristics of road vehicles considering the interaction of aerodynamic forces between the road vehicles and bridge is necessary for predicting the performance of vehicle under wind loads properly. This paper studies aerodynamic characteristics of road vehicles when vehicles run on bridges under cross winds using the CFD method. The dependence of aerodynamic forces on vehicle speeds, the interaction of aerodynamic forces between the vehicles and bridges and the influence of the turbulence are investigated by different simulation cases.

Interference Effect on Stationary Aerodynamic Performance between Parallel Bridges

2017 ◽  
Vol 17 (02) ◽  
pp. 1750017
Author(s):  
Rui Zhou ◽  
Yongxin Yang ◽  
Lihai Zhang ◽  
Yaojun Ge
Keyword(s):  
Aerodynamic Force ◽  
Aerodynamic Performance ◽  
Vertical Position ◽  
Width Ratio ◽  
Suspension Bridges ◽  
Box Girders ◽  
Force Coefficients ◽  
Smooth Flow ◽  
Operation Stage ◽  
Bridge Structures

During the operation stage, parallel bridges may become nonparallel as a result of unequal load distribution between two parallel bridges and other special conditions. Aerodynamic performance could change significantly under nonparallel positions and become different from that under parallel positions. In this paper, the stationary aerodynamic performance of two parallel bridges under various nonparallel positions during operation stage is studied through a series of wind tunnel tests. This includes the investigation of two horizontal gap distances (HGDs), five relative vertical displacements (RVD) and five relative torsional displacements (RTD). First, sectional models of two closed box girders were tested in smooth flow for stationary aerodynamic force coefficients. An optimum iteration method was then used to calculate the structural displacements and torsional divergence critical wind velocities ([Formula: see text]) of two assumed suspension bridges under stationary aerodynamic force. The research outcomes demonstrated that the changes of stationary aerodynamic force coefficients are dependent on the relative displacements of two girders and wind attack angles. In addition, it was revealed that interference effects are detrimental to stationary aerodynamic instability of two bridges with a larger gap-width ratio (i.e. D/B [Formula: see text] 1), which is related to the aerodynamic shape of girders and bridge structures. Further, the [Formula: see text] of the leeward bridge significantly decline when the vertical position of the leeward bridge become higher that of the windward bridge. Most importantly, it showed that the combination of RVD and RTD (e.g. RVD [Formula: see text][Formula: see text]mm and RTD [Formula: see text]) could potentially lead to the worst stationary aerodynamic performance by decreasing [Formula: see text] of the windward and leeward bridge with 12.03% and 7.89%, respectively.

Studies on Galloping of Iced Conductor Based on Tower-Line Coupling System – Aerodynamic Loads

2012 ◽  
Vol 182-183 ◽  
pp. 1630-1633
Author(s):  
Hao Jun Hu ◽  
Yuan Han Wang ◽  
Zi Dong Hu
Keyword(s):  
Finite Element ◽  
Wind Speed ◽  
Finite Element Model ◽  
Aerodynamic Force ◽  
Element Model ◽  
Aerodynamic Characteristics ◽  
Explicit Integration ◽  
Computing Platform ◽  
Coupling System ◽  
Line Coupling

Based on the second development at the ANSYS computing platform, finite element model of a Tower-Line Coupling system was established. The computational fluid dynamics module (CFX) was used for the numerical simulation of the aerodynamic characteristics of iced conductor. On the basis of the Kaimal spectrum, fast Fourier transform was introduced to prepare the wind speed simulation program WVFS with spatial correlation into consideration, thus generating aerodynamic coefficients of iced conductor at different wind attack angles as well as wind speed time series at tower-line nodes. According to the finite element model of continuous multi-conductors and the aerodynamic force- wind attack angle curve, the explicit integration is applied for numerical solution of galloping of iced conductor.

Are seed mass and seedling size and shape related to altitude? Evidence in Gymnocalycium monvillei (Cactaceae)

Botany ◽  
2015 ◽  
Vol 93 (8) ◽  
pp. 529-533 ◽  
Author(s):  
Karen Bauk ◽  
Reyes Pérez-Sánchez ◽  
Sebastián R. Zeballos ◽  
M. Laura Las Peñas ◽  
Joel Flores ◽  
...  
Keyword(s):  
Negative Relationship ◽  
Seed Mass ◽  
Climatic Conditions ◽  
Mean Annual Temperature ◽  
Altitudinal Distribution ◽  
Seedling Morphology ◽  
Seedling Size ◽  
Size And Shape ◽  
Seedling Traits ◽  
Species Response

Several studies reported a negative relationship between altitude and seed mass. In cactus species, seed mass has been also related to seedling morphology (size and shape). Here we studied Gymnocalycium monvillei (Lem.) Pfeiff. ex Britton & Rose, a cactus species with a wide altitudinal distribution, with the main aim of analyzing how altitude affects seed mass and seedling size (height and width) and shape (globose or columnar). We collected seeds from five sites along the entire altitudinal distribution of the species in the Córdoba Mountains (sites were located between 878 and 2230 m a.s.l.), encompassing a marked climatic gradient (6 °C of mean annual temperature difference between the extreme sites). Seed mass and seedling traits were measured in the laboratory. Seedling height increased with altitude, whereas seed mass was not related to this parameter. Seedlings became more globose (reduced surface/volume ratio) with decreasing altitude. Variation in seedling shape along the altitudinal gradient may be related to the contrasting climatic conditions to which seedlings are exposed, and could account for the wide altitudinal distribution of G. monvillei. Our results highlight the importance of seedling traits in the species’ response to climatic change.

Effect of Shock Wave Behavior on Unsteady Aerodynamic Characteristics of Oscillating Transonic Compressor Cascade

2021 ◽  
Author(s):  
Jiuliang Gan ◽  
Toshinori Watanabe ◽  
Takehiro Himeno
Keyword(s):  
Shock Wave ◽  
Aerodynamic Force ◽  
Aerodynamic Characteristics ◽  
Fast Response ◽  
Influence Coefficient ◽  
Compressor Cascade ◽  
Blade Vibration ◽  
Unsteady Pressure ◽  
Transonic Compressor ◽  
Unsteady Aerodynamic

Abstract The unsteady behavior of the shock wave was studied in an oscillating transonic compressor cascade. The experimental measurement and corresponding numerical simulation were conducted on the cascade with different shock patterns based on influence coefficient method. The unsteady pressure distribution on blade surface was measured with fast-response pressure-sensitive paint (PSP) to capture the unsteady aerodynamic force as well as the shock wave movement. It was found that the movement of shock waves in the neighboring flow passages of the oscillating blade was almost anti-phase between the two shock patterns, namely, the double shocks pattern and the merged shock pattern. It was also found that the amplitude of the unsteady pressure caused by the passage shock wave was very large under the merged shock pattern compared with the double shocks pattern. The stability of blade vibration was also analyzed for both shock patterns including 3-D flow effect. These findings were thought to shed light on the fundamental understanding of the unsteady aerodynamic characteristics of oscillating cascade caused by the shock wave behavior.

The Aerodynamic Characteristics of the Pantograph When the Train Passes Through the Tunnel

2017 ◽  
Author(s):  
Dilong Guo ◽  
Wen Liu ◽  
Junhao Song ◽  
Ye Zhang ◽  
Guowei Yang
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Maximum Amplitude ◽  
Aerodynamic Characteristics ◽  
High Speed Train ◽  
Expansion Waves ◽  
Compression And Expansion ◽  
High Speed Trains ◽  
Current Characteristics ◽  
Pass Through

The aerodynamic force acting on the pantograph by the airflow is obviously unsteady and has a certain vibration frequency and amplitude, while the high-speed train passes through the tunnel. In addition to the unsteady behavior in the open-air operation, the compressive and expansion waves in the tunnel will be generated due to the influence of the blocking ratio. The propagation of the compression and expansion waves in the tunnel will affect the pantograph pressure distribution and cause the pantograph stress state to change significantly, which affects the current characteristics of the pantograph. In this paper, the aerodynamic force of the pantograph is studied with the method of the IDDES combined with overset grid technique when high speed train passes through the tunnel. The results show that the aerodynamic force of the pantograph is subjected to violent oscillations when the pantograph passes through the tunnel, especially at the entrance of the tunnel, the exit of the tunnel and the expansion wave passing through the pantograph. The changes of the pantograph aerodynamic force can reach a maximum amplitude of 106%. When high-speed trains pass through tunnels at different speeds, the aerodynamic coefficients of the pantographs are roughly the same.

scholarly journals Aerodynamic Damping Characteristics of a Transonic Turbine Cascade

1999 ◽  
Author(s):  
Mizuho Aotsuka ◽  
Toshinori Watanabe ◽  
Yasuo Machida
Keyword(s):  
Phase Angle ◽  
Aerodynamic Force ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Influence Coefficient ◽  
Suction Surface ◽  
Aerodynamic Damping ◽  
Unsteady Aerodynamic ◽  
Design Case ◽  
Oscillation Instability

The unsteady aerodynamic characteristics of oscillating thin turbine blades were studied both experimentally and numerically to obtain the comprehensive knowledge on the aerodynamic damping of the blades operating in transonic flows. The experiment was carried out in a linear cascade tunnel by use of the influence coefficient method. The two flow conditions were adopted, namely, a near-design condition and an off-design condition with a higher back pressure. In the results for the near-design case, a strong vibration instability was observed in the positive side of the interblade phase angle. In the off-design case, however, the instability did not appear for almost all the interblade phase angles. A drastic change was found in the phase angle of unsteady aerodynamic force between the two cases, which change was a governing factor for the oscillation instability. Numerical simulation based on 2-D Euler equation revealed that the phase change came from the change in phase of the unsteady surface pressure across the shock impingement point on the blade suction surface in the off-design case. The numerical results also showed that the aerodynamic damping increased with increasing reduced frequency, and that the oscillation instability disappeared.

scholarly journals 2D Numerical Simulation Study of Airfoil Performance

2021 ◽  
Author(s):  
Nasser Shelil
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Air Temperature ◽  
Wind Turbines ◽  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Ansys Fluent

Abstract. The aerodynamic characteristics of DTU-LN221 airfoil is studied. ANSYS Fluent is used to simulate the airfoil performance with seven different turbulence models. The simulation results for the airfoil with different turbulence models are compared with the wind tunnel experimental data performed under the same operating conditions. It is found that there is a good agreement between the computational fluid dynamics (CFD) predicted aerodynamic force coefficients with wind tunnel experimental data especially with angle of attack between −5° to 10°. RSM is chosen to investigate the flow field structure and the surface pressure coefficients under different angle of attack between −5° to 10°. Also the effect of changing air temperature, velocity and turbulence intensity on lift and drag coefficients/forces are examined. The results show that it is recommended to operate the wind turbines airfoil at low air temperature and high velocity to enhance the performance of the wind turbines.

scholarly journals Svalbard reindeer (Rangifer tarandus platyrhynchus) antler characteristics reflecting the local environmental conditions

2019 ◽  
Vol 46 (1) ◽  
pp. 16-23
Author(s):  
Jan Kavan ◽  
Veronika Anděrová
Keyword(s):  
Environmental Conditions ◽  
Rangifer Tarandus ◽  
Well Being ◽  
Climatic Conditions ◽  
High Mountain ◽  
Atmospheric Conditions ◽  
Individual Subject ◽  
Svalbard Reindeer ◽  
Invasive Method ◽  
Antler Size

AbstractA new non-invasive method based on picture analysis was used to estimate the conditions in Svalbard reindeer populations. The well-being of an individual subject is often expressed through visual indices. Two distinct reindeer populations were compared based on their antler parameters. Relative antler size and number of tines are variables supposed to reflect correspondingly the environmental conditions of sedentary populations within the growing season. The occurrence areas of two studied populations are distinctly isolated – separated with high mountain ridges, glaciers and fjords. The population in Petuniabukta occupies a sparsely vegetated region with harsh climatic conditions, whereas Skansbukta represents an area with continuous tundra vegetation cover, milder climatic conditions and, consequently, also a longer vegetation season. These environmental factors probably caused significant differences in the relative antler size and number of tines in the studied species. The Skansbukta population exhibited a larger relative antler size and higher number of tines than the population in Petuniabukta (both parameters differed significantly, p < 0.01). This difference reflects concisely the different environmental conditions of both locations. A comparison of Skansbukta population antler characteristics between years 2017 and 2018 did not reveal significant changes, most probably due to very similar atmospheric conditions in these two years (in terms of air temperature).

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