Effect Of Crosswinds Research Articles

Study of Paired Approach Wake Separation Based on Crosswinds

The effect of crosswinds on paired approach (PA) procedures for Closely Spaced Parallel Runways (CSPR) is investigated in this paper by fully utilizing the crosswind environment to implement a more efficient PA and increase runway capacity. An improved wake dissipation model is used to quickly predict the change in the wake velocity field for the PA procedures. The change in the width of the hazard zone is explored in detail using the roll moment coefficient as a determination index. The calculation method for the hazard zone of a wake encounter in a PA is designed considering the influence of crosswind, turbulence, and ground effect. The results show the diffusion rate of the hazard zone and a decrease in the width of the maximum hazard zone under a breezeless environment with increases in the turbulence intensity. The maximum hazard zone width decreases with an increase in crosswind speed. Favorable crosswinds can reduce wake separation and improve the efficiency of a PA. Lower turbulence intensity has a better crosswind effect under a normal PA. The 3-degree offset PA can accommodate larger unfavorable crosswinds, with a higher turbulence intensity having a better crosswind effect. The 3-degree offset PA can substantially increase the proportion of time when no wake affects the PA procedure.

The Effect of wind barriers on the local wind field on a bridge deck

Abstract The adverse effect of crosswinds on road vehicles on a bridge deck or traffic lanes is of increasing concern. Local flow characteristics depend on the bridge's architecture and wind barriers are commonly used to alleviate wind-induced instability for vehicles. Terrain orography is another dominant factor. This study uses a terrain model with a coastal bridge (Chen-Kung Bridge, Penghu, Taiwan). The bridge is located between a reservoir and the Taiwan Strait. Numerous accidents have occurred due to strong monsoon winds in autumn and winter. In wind tunnel experiments, an atmosphere boundary layer is established and the test conditions (wind speed and wind incidence) are taken from local meteorological data. The effect of the height of solid wind barriers on local wind direction and speed is determined. The results can be used to remodel wind barriers to increase safety for road vehicles.

How do crosswinds from two turbulent generators affect the aerodynamic loads of running trains at tunnel entrances?

In order to investigate the effect of natural turbulent crosswinds on the aerodynamic loads of a high-speed train (HST) running through a tunnel entrance of high-speed railways, the new contribution is that the changing law of the HST's aerodynamic loads under the incoming turbulence with actual turbulence integral scale is revealed when the HST running in tunnel-flat ground-tunnel scenes, based on two types of turbulence generators with size scaled up by 8 times. The train surface pressure coefficients of the numerical model are compared with the corresponding results of wind tunnel experiments to verify the computational fluid dynamics method. The primary results show that the incoming turbulent flow generated by the spire is consistent with the characteristics of the measured wind. The peak aerodynamic load coefficients of the head carriage increase 1.12–1.5 and 1.06–2.0 times, respectively, under the incoming turbulent flow by the spire and fence, compared to the incoming flow of 11.50 m/s.

Influence of wind and rain environment on operational safety of intercity train running on the viaduct

PurposeBased on the aerodynamic loads and dynamic performances of trains, this study aims to investigate the effect of crosswinds and raindrops on intercity trains operating on viaducts to ensure the safe operation of intercity railways in metropolitan areas.Design/methodology/approachAn approach coupled with the Euler multiphase model as well as the standard k-ɛ turbulence model is used to investigate the coupled flow feature surrounding trains and viaducts, including airflow and raindrops, and the numerical results are validated with those of the wind tunnel test. Additionally, the train’s dynamic response and the operating safety region in different crosswind speeds and rainfall is investigated based on train’s aerodynamic loads and the train wheel–rail dynamics simulation.FindingsThe aerodynamic loads of trains at varying running speeds exhibit an increasing trend as the increase of wind speed and rainfall intensity. The motion of raindrop particles demonstrates a significant similarity with the airflow in wind and rain environments, as a result of the dominance of airflow and the supplementary impacts of droplets. As the train’s operating speed ranged between 120 and 200 km/h and within a rainfall range of 20–100 mm/h, the safe operating region of trains decreased by 0.56%–7.03%, compared with the no-rain condition (0 mm/h).Originality/valueThe impact of crosswind speeds and rainfall on the train’s aerodynamic safety is studied, including the flow feature of crosswind and different particle-sized raindrops around the train and viaduct, aerodynamic loads coefficients suffered by the intercity train as well as the operating safety region of intercity trains on the viaduct.

Moving Model Experimental Study on a Slipstream of a High-Speed Train Running on the Bridge Suffering a Crosswind

A running train induces a slipstream around it, which is closely related to its aerodynamic features and crucial for the safety of people and structures near the track. However, the effect of crosswinds is almost inevitable when the train runs on a bridge. In this work, an experimental study using moving model testing technology was conducted to investigate the effects of wind speeds, train speeds, and yaw angles on the aerodynamic performance of a Fuxing Hao high-speed train running on a bridge under the influence of crosswind. The results show that, for the crosswind cases, the slipstream velocities on the leeward side of the train are generally higher than those in the no-crosswind cases. Moreover, the results were compared for the cases with the same effective yaw angle of 21.8° but different wind speeds (6 m/s, 8 m/s) and train speeds (15 m/s, 20 m/s), which suggests the method of the resultant wind’s yaw angle is no longer valid when the train runs on a bridge due to the aerodynamic interactions.

Flow Structure Characteristics of the Simplified Compact Car Exposed to Crosswind Effects using CFD

Aerodynamic characteristics of a car are important in reducing car accidents caused by wind loading and in lowering fuel economy, continuing to be a major topic of interest. The restrictions of wind tunnel tests and the rising trend of numerical methods have been complied with by past researchers to investigate vehicle aerodynamics computationally. This research aims to analyze comprehensively the effect of crosswinds on a moving vehicle in terms of aerodynamic loadings and flow structures using commercial fluid dynamic software ANSYS FLUENT. This paper will focus on the CFD-based simplified compact car body developed in CATIA V5 by neglecting the external parts such as side mirrors and underbody.

On the effect of boat-tails on a simplified heavy vehicle geometry under crosswinds

The flow around a Ground Transport System (GTS), is numerically investigated using steady RANS model; k−ω SST, at a Reynolds number of ∼2×106. This paper focuses on the effect of crosswinds on the near-wake structure of the GTS with and without boat-tails. Upon the emanation of crosswinds, a quadratic increase in the drag coefficient(CD) was observed, as a function of the yaw angle. Such an increase is attributed to the break in the symmetry of near-wake structure and three, streamwise vortices emanating from the leading edges of the GTS. Boat-tail with a slant angle of 15°, at zero yaw, has resulted in a(CD) reduction of up to∼50%, relative to the baseline GTS. The reduction is consistent with previous studies on various simplified geometries. Such reduction is a resultant of a smaller wake length, coupled with an overall increase in the pressure in the wake, consequently increasing the mean base pressure coefficient. Higher boat-tail angles have resulted in an increase in CD, whereas, under crosswind, ∼40% reduction in (CD) is observed. Boat-tails have additionally resulted in a quasi-symmetric near-wake structure, under crosswinds, acting as a blockage and preventing the interaction between the three streamwise vortices and the near-wake.

Effect of crosswinds on aerodynamic characteristics around a generic train model

ABSTRACTIn this article, simulations of crosswinds over a rectangular prism with two types of train nose shapes (i.e. blunt and ellipse) that are running on flat ground case are discussed. The incident flow angle is varied from 0° to 90°. The flow around the train is solved using the incompressible form of the unsteady Reynolds Navier-Stokes (URANS) equations combined with the Shear-Stress-Transport turbulence model. The Reynolds number used, based on the height of the train is 3.7 × 105. Two distinctive flow regimes appear which represent a slender body behaviour at a smaller range of incident flow angles (below 45°) and bluff body behaviour at a much higher range of incident flow angles (above 45°). The safety guidelines for train’s operation suggested that both the train’s nose geometry and the wind speed condition are the two major factors that limit the maximum allowable speed for a particular train to be travelling.

Experimental Research on Optimizing Inlet Airflow of Wet Cooling Towers under Crosswind Conditions

A new approach of installing air deflectors around tower inlet circumferentially was proposed to optimize the inlet airflow and reduce the adverse effect of crosswinds on the thermal performance of natural draft wet cooling towers (NDWCT). And inlet airflow uniformity coefficient was defined to analyze the uniformity of circumferential inlet airflow quantitatively. Then the effect of air deflectors on the NDWCT performance was investigated experimentally. By contrast between inlet air flow rate and cooling efficiency, it has been found that crosswinds not only decrease the inlet air flow rate, but also reduce the uniformity of inlet airflow, which reduce NDWCT performance jointly. After installing air deflectors, the inlet air flow rate and uniformity coefficient increase, the uniformity of heat and mass transfer increases correspondingly, which improve the cooling performance. In addition, analysis on Lewis factor demonstrates that the inlet airflow optimization has more enhancement of heat transfer than mass transfer, but leads to more water evaporation loss.

On the effect of crosswinds on the slipstream of a freight train and associated effects

When a train moves through the air, a region of air moves along with it at approximately the same speed: this region of air is known as the ‘slipstream’. Numerical simulations were conducted in order to simulate the slipstream around a model-scale freight train when subjected to crosswinds with two different yaw angles; 10° and 30°. The results were compared to a previous slipstream study without a crosswind. The velocities on the windward side of the train for each case are mostly lower than the crosswind speed due to the flow stagnation on the side of the train. In general, crosswind velocities are lower than those in the no-crosswind case. On the leeward side, velocities from the 30° crosswind case remain higher than train speed for more than two metres from train side. Peak instantaneous velocities showed strong dependence on yaw angle and position from train side as well as exhibiting superficial comparison to full-scale data. Velocities were used as inputs to a spring-mass-damper model which modelled human responses to wind gusts. The effect of a crosswind on the train's slipstream significantly increased the likelihood of a person becoming unsteadied while standing on the leeward side of the train.

Wind effects on the migration routes of trans-Saharan soaring raptors: geographical, seasonal, and interspecific variation.

Wind is among the most important environmental factors shaping birds’ migration patterns. Birds must deal with the displacement caused by crosswinds and their behavior can vary according to different factors such as flight mode, migratory season, experience, and distance to goal areas. Here we analyze the relationship between wind and migratory movements of three raptor species which migrate by soaring–gliding flight: Egyptian vulture Neophron percnopterus, booted eagle Aquila pennata, and short-toed snake eagle Circaetus gallicus. We analyzed daily migratory segments (i.e., the path joining consecutive roosting locations) using data recorded by GPS satellite telemetry. Daily movements of Egyptian vultures and booted eagles were significantly affected by tailwinds during both autumn and spring migrations. In contrast, daily movements of short-toed eagles were only significantly affected by tailwinds during autumn migration. The effect of crosswinds was significant in all cases. Interestingly, Egyptian vultures and booted eagles showed latitudinal differences in their behavior: both species compensated more frequently at the onset of autumn migration and, at the end of the season when reaching their wintering areas, the proportion of drift segments was higher. In contrast, there was a higher drift at the onset of spring migration and a higher compensation at the end. Our results highlight the effect of wind patterns on the migratory routes of soaring raptors, with different outcomes in relation to species, season, and latitude, ultimately shaping the loop migration patterns that current tracking techniques are showing to be widespread in many long distance migrants.

The effect of crosswinds on ride comfort in high speed trains running on curves

The effect of crosswinds on the risk of railway vehicles overturning has been a major issue ever since manufacturers began to produce lighter vehicles that run at high speeds. However, ride comfort can also be influenced by crosswinds, and this effect has not been thoroughly analyzed. This article describes the effect of crosswinds on ride comfort in high speed trains when running on curves and for several wind velocities under a Chinese hat wind scenario, which is the scenario recommended by the standard. Simulation results show that the combination of crosswinds and the added stiffness of the lateral bumpstop on the secondary suspension can become a significant source of instability, leading to flange-to-flange contact and greatly jeopardizing ride comfort. Moreover, this comfort problem is an issue even when the wheel unloading ratio is well below the standard’s limits and vehicle safety can be guaranteed.

CFD simulations of the flow around a cyclist subjected to crosswinds

For the first time, an extensive numerical study of the effect of crosswinds on the flow around a cyclist on a bicycle with stationary wheels has been undertaken for crosswind (yaw) angles ranging from 0° to 90°. The flow field and the aerodynamic forces have been obtained using three numerical techniques: Reynolds Averaged Navier Stokes (RANS), Detached Eddy Simulation (DES) and Large Eddy Simulation (LES). RANS simulations have been undertaken for all the range of yaw angles to provide a general insight of the flow around a cyclist, whilst DES and LES have been undertaken at 15° yaw angle in order to investigate the time-varying flow physics in detail. The aerodynamic forces have been compared with a series of wind tunnel experiments. The RANS results showed the development of large flow separation around the bicycle with increasing yaw angles. The instantaneous flow structures and the auto-spectral densities of the time histories of the force coefficients are identified and revealed that the DES and LES turbulence models are able to predict the dominant frequencies found in the physical experiments. This work provides an improved understanding of the flow characteristics around a cyclist in crosswinds that will hopefully help to improve the safety of cyclists.

A review of train aerodynamics Part 2 – Applications

AbstractThis paper is the second part of a two-part paper that presents a wide-ranging review of train aerodynamics. Part 1 presented a detailed description of the flow field around the train and identified a number of flow regions. The effect of cross winds and flow confinement was also discussed. Based on this basic understanding, this paper then addresses a number of issues that are of concern in the design and operation of modern trains. These include aerodynamic resistance and energy consumption, aerodynamic loads on trackside structures, the safety of passengers and trackside workers in train slipstreams, the flight of ballast beneath trains, the overturning of trains in high winds and the issues associated with trains passing through tunnels. Brief conclusions are drawn regarding the need to establish a consistent risk based framework for aerodynamic effects.

Effect of wind, thermal convection, and variation in flight strategies on the daily rhythm and flight paths of migrating raptors at Georgia's Black Sea coast

Every autumn, large numbers of raptors migrate through geographical convergence zones to avoid crossing large bodies of water. At coastal convergence zones, raptors may aggregate along coastlines because of convective or wind conditions. However, the effect of wind and thermal convection on migrating raptors may vary depending on local landscapes and weather, and on the flight strategies of different raptors. From 20 August to 14 October 2008 and 2009, we studied the effect of cloud development and crosswinds on the flight paths of raptors migrating through the eastern Black Sea convergence zone, where coastal lowlands at the foothills of the Pontic Mountains form a geographical bottleneck 5-km-wide near Batumi, the capital of the Independent Republic of Ajaria in southwestern Georgia. To identify key correlates of local aggregation, we examined diurnal variation in migration intensity and coastal aggregation of 11 species of raptors categorized based on size and flight strategies. As reported at other convergence zones, migration intensity of large obligate-soaring species peaked during the core period of thermal activity at mid-day. When clouds developed over interior mountains and limited thermal convection, these large obligate-soaring species aggregated near the coast. However, medium-sized soaring migrants that occasionally use flapping flight did not aggregate at the coast when clouds over the mountains weakened thermal convection. Numbers of alternate soaring-flapping harriers (Circus spp.) peaked during early morning, with these raptors depending more on flapping flight during a time of day with poor thermal convection. Small sparrowhawks (Accipiter spp.) aggregated at the coast during periods when winds blew offshore, suggesting aggregation caused by wind drift. Thus, weather conditions, including cloud cover and wind speed and direction, can influence the daily rhythm and flight paths of migrating raptors and, therefore, should be accounted for before inferring population trends from migration counts.

The Effect of Crosswinds on Cyclists: An Experimental Study

The aims of this research were to firstly investigate the effect of crosswinds on the aerodynamic behaviour of cyclists and secondly, to determine which parameters (cyclist position and bike type) influenced the aerodynamic forces on cyclists the most. The aerodynamic response of two different full-scale bikes with and without a mannequin has been recorded for a variety of crosswind angles ranging from 0o – 90o (in 15o increments). The results showed that the wind induced force is a function of the crosswind angle. The actual aerodynamic loads arising from such winds can be up to about 2.5 times the aerodynamic drag. It has also been observed that the torso angle has little effect on the lateral force coefficient. In contrast, the bike type significantly affects the aerodynamic forces: at large yaw angles, a road bike is responsible for approximately 60% of the total lateral force coefficient. This study is the first step in the process of determining the effect of crosswind from a full range of angles of attack on cyclists, and will help to improve the safety of cyclists and equipment, and to define guidelines for cycling lanes.

Is there a different response to winds during migration between soaring and flapping raptors? An example with the Montagu’s harrier and the lesser kestrel

During migrations, birds have to cope with varying meteorological conditions, which shape their migratory routes and affect their performance. Amongst these, wind is the main meteorological agent influencing behaviour of birds in their migration journeys. Here we analyze the effect of winds during migrations of adult individuals of two raptor species tracked with satellite telemetry, the Montagu’s harrier (Circus pygargus) and the lesser kestrel (Falco naumanni). While harriers use mostly soaring flight, kestrels principally use flapping flight and thus, wind can differently affect these birds. We found that both forward and perpendicular winds significantly affected the movements of the Montagu’s harrier, which were drifted from their intended direction but also took advantage of tailwinds. On the contrary, lesser kestrels moved more regardless of forward winds, despite they were highly drifted by crosswinds. Our results also support that the drifting effect of winds at the onset of the spring migration may explain the loop migration observed for both species, with birds compensating later the effect of crosswinds to arrive to their breeding areas. Results presented here illustrate how winds can differently affect migrating birds according to their flight modes.

Optimizing rainwater collection from droplets falling through crosswinds during the north‐east monsoons

AbstractThe quantity of precipitation received by the monsoons is enormous. The south‐west monsoons, unlike the north‐east monsoons, have been studied in great detail. This study deals with rainwater collection during the NE monsoons and involves an examination of the stochastic nature of a turbulent boundary layer and the effect of crosswinds on rain droplet trajectories and thence their collection. It must be borne in mind that whilst mid latitude precipitations typically range from a few millimetres per hour, the north‐east monsoon showers experience rainfall rates often 10 times higher than this value and their calculations deserve special attention. Probability distribution functions are calculated to quantify the coordinates of the landing trajectories on rooftop collectors. This investigation was essential to emulate the prevalent conditions of intense driving rain on top of high rises where setting up of a collector will be most suitable to directly harness rainwater in its purest form before contamination.

Direct Two–Phase Numerical Simulation of Snowdrift Remediation using Three–Dimensional Deflection Fins

We present a versatile three – dimensional two – phase model for simulating snow drift relocation around buildings utilizing deflection fins of various shapes and sizes. The first phase involves numerically obtaining the air velocity profile around the building and fin using a velocity – pressure Navier – Stokes algorithm, while the second phase involves direct classical simulation of snowfall with particle – particle, particle – surface and one – way particle – gusting wind interactions introduced to control accumulation, erosion, clumping and drifting. Because the simulation technique is direct, it is potentially useful for storms and surfaces with widely varying conditions. We are also able to consider the effect of crosswinds.

Effect of crosswinds and wheel selection on the aerodynamic behavior of a cyclist

This paper reports aerodynamic testing results of various styles of bicycle wheels across yaw angles of 0 to 30 degrees. Wheels considered include disc wheels, a bladed spoke wheel and various depth dished wheels. Testing has been completed in a three quarter open jet test section wind tunnel with a anthropomorphic mannequin and rotating front and rear wheels. Data is provided as to the influence of the wheel type on the overall drag and side force, and yaw and roll moment of the rider and bicycle combination. The results demonstrate that the wheel type has a significant effect on both the aerodynamic drag and stability of the bicycle system, and that evaluation of wheel aerodynamic performance should not be based on drag alone.