Crosswind Conditions Research Articles

Analysis of dust dispersion in the loading of a bulk carrier ship using CFD and DEM

Dust generation and dispersion continue to be a major concern for many in the industries that rely on bulk materials handling, and the ability to predict dust generation and dispersion remains challenging. This study looks at the use of computational fluid dynamics (CFD) and discrete element method (DEM) as a means of predicting dust generation and dispersion. The paper outlines work completed on predicting dust dispersion during the loading process of a bulk carrier using the Rotabox™ system for a stevedoring company at a port in Australia. CFD simulations are conducted to analyze the induced air flow generated inside the cargo hold of a bulk carrier including typical cross-wind conditions. Coupled CFD-DEM simulations are conducted to analysis the air flow inside the cargo hold driven by the unloading of the bulk material. Dust particle free-settling time is used to assess the dust cloud formation and dispersion based on the flow conditions predicted by CFD-DEM simulations. The study finds that the unloading process is likely to disperse dust into the cargo hold at a level that without dust suppression would result in dust being dispersed into the broader environment by the typical cross-wind conditions at the port.

Research on the ground vortex and inlet flow field under the ground crosswind condition

The ground vortex field and nacelle inlet flow field under ground crosswind condition are investigated experimentally and numerically. A test rig with ground plane and crosswind blowing devices have been built, the experiments have been carried out by DSA3217 Pressure Scanner and Hot Wire Anemometer to get inlet total pressure distribution and the unsteady characteristics of ground vortex, respectively. The characteristics of ground vortex are quantitatively analyzed respect to vortex intensity, frequency, and dynamics, then the study crosswind interact on ground vortex is conducted, by considering the direct influence of crosswind on inlet distortion and the indirect effect of crosswind on ground vortex. Finally, it is found that due to the ground vortex, the process that inlet distortion increases with crosswind is unsteady and unstable. According to the variation of vortex intensity and the influence level that ground vortex acted on the inlet flow field, the process of blowing away the ground vortex from the beginning to the end can be divided into four phases, the encouraging phase, the initial blowing phase, the rapid blowing phase and the end blowing phase.

Розрахункове дослідження аеродинамічних характеристик рульового гвинта вертольота типу Мі-8 з урахуванням інтерференції з несучим гвинтом на режимі висіння при боковому вітрі

Under certain conditions of a helicopter flight, the main rotor can exert a rather strong effect on the tail rotor, changing its traction and power characteristics. The calculated and experimental characteristics of an isolated tail rotor under such operating conditions can differ significantly from those under conditions of interaction with the main rotor. The study of this phenomenon is an urgent task, since a change in the characteristics of the tail rotor and the conditions of its operation in the presence of the main rotor can cause a decrease in controllability margins and, as a consequence, the cause of an aircraft accident, for example, the so-called. "left rotation" of the helicopter. Since 1985, on helicopters from M. L. Mile, 42 aviation accidents occurred in units and subdivisions of the state and civil aviation of the USSR (and now Russia) due to helicopters falling into spontaneous left rotation. Over the past 10 years, 29 accidents (8 accidents and 21 accidents) have occurred for this reason. 29 helicopters were lost: 20 Mi-8, 5 Mi-24, 4 Mi-2. Experience shows that getting into an uncontrolled left rotation in almost 100% of cases ends with a collision of the helicopter with the ground and overturning it on the starboard side. The interaction of the main and tail rotor is most significantly manifested in the modes of horizontal flight with sliding at low speeds and hovering in crosswind conditions. This is due to the peculiarities of the formation of the main rotor vortex wake. In this article, the case of aerodynamic interference of the main rotor and several helicopter configurations in horizontal flight mode with the low speed with sliding (hovering in a crosswind) is considered. Using the methods of computational fluid dynamics, the degree of influence of the main rotor on the tail rotor was investigated in the described modes. The most severe operating modes of the tail rotor of each configuration have been determined. Based on the results of calculations, the most rational configuration of the tail rotor has been chosen, which has the greatest reserves of controllability under unfavorable operating conditions. The results obtained have been used in the design of a new perspective helicopter, modernization of the existing fleet, as well as improving the flight safety level.

Near-to-Far Wake Characteristics of Road Vehicles Part 3: Influence of Multi-Vehicle Interactions

<div class="section abstract"><div class="htmlview paragraph">Conventional assessments of the aerodynamic performance of ground vehicles have, to date, been considered in the context of a vehicle that encounters a uniform wind field in the absence of surrounding traffic. Recent vehicle-platooning studies have revealed measurable fuel savings when following other vehicles at inter-vehicle distances experienced in every-day traffic. These energy savings have been attributed in large part to the air-wakes of the leading vehicles. This set of three papers documents a study to examine the moderate-to-far regions of ground-vehicle wakes (one to ten vehicle lengths), in the context of their potential influence on other vehicles.</div><div class="htmlview paragraph">Part Three of this three-part paper documents the wake characteristics for multi-vehicle scenarios of two or three vehicles, in single-lane or two-lane arrangements. A set of high-fidelity numerical simulations, based on a Lattice-Boltzmann approach, and a series of scaled-model wind-tunnel measurements are presented to examine some multi-vehicle scenarios with four types of vehicle shapes: a sedan, an SUV, a medium-duty vehicle, and a heavy-duty vehicle. The wake-merging process of a two-lane longitudinally-staggered sedan-and-SUV configuration is examined in detail with and without cross winds. Experimental-results are presented only for the SUV, medium- and heavy-duty vehicle shapes due to challenges described in Part One with respect to the sedan-model and the stationary-floor arrangement.</div><div class="htmlview paragraph">Complex wake patterns emerge under multi-lane scenarios, particularly under cross-wind conditions, but the results suggest a level of predictability in the aggregate wake properties. Only for the cases with close lateral proximity (side-by-side configurations) do the wake patterns change substantially such that the characteristics of the individual wakes are not perceptible. Additionally, the merged wakes in cross winds are shown to potentially influence vehicles up to three or four lane widths away. The results suggest that superposition of moderate-to-far-wake profiles may be possible to generate on-road wind conditions associated with a range of traffic scenarios.</div></div>

Tower Configuration Impacts on the Thermal and Flow Performance of Steel-Truss Natural Draft Dry Cooling System

In recent years, the steel-truss natural draft dry cooling technique has received attention owing to its advantages in better aseismic capability, shorter construction period, and preferable recycling. For cooling towers generating the draft force of air flow, its configuration may impact the thermal and flow performance of the steel-truss natural draft dry cooling system. With regard to the issue, this work explored the thermal and flow characteristics for the steel-truss natural draft dry cooling systems with four typical engineering tower configurations. By numerical simulation, the pressure, flow, and temperature contours were analyzed, then air mass flow rates and heat rejections were calculated and compared for the local air-cooled sectors and overall steel-truss natural draft dry cooling systems with those four tower configurations. The results present that tower 2 with the conical/cylindrical configuration had slightly lower heat rejection compared with tower 1 with the traditional hyperbolic configuration. Tower 3 with the hyperbolic/cylindrical configuration showed better thermo-flow performances than tower 1 at high crosswinds, while tower 4 with the completely cylindrical configuration appeared to have much reduced cooling capability under various crosswind conditions, along with strongly deteriorated thermal and flow behaviors. As for engineering application of the steel-truss natural draft dry cooling system, the traditional hyperbolic tower configuration is recommended for local regions with gentle wind, while for those areas with gale wind yearly, the hyperbolic/cylindrical integrated cooling tower is preferred.

Adaptive feedforward control for crosswind landing with variable step size

In this article, a modified Steiglitz–McBride (SM) structure with variable step size is proposed for aircraft feedforward control to reduce lateral landing deviation in the presence of crosswind disturbance. Currently, most of the aircraft landing studies focus on the trajectory tracking problems in the longitudinal plane and seldom focus on lateral disturbances. This article develops a modified SM structure–based feedforward control system to online estimate both the primary path and the control path (secondary path), where a fuzzy logic–based variable step size strategy is implemented to ensure fast convergence rate and strong robustness under complex crosswind scenarios. As a consequence, the lateral deviation during crosswind landing could be largely reduced as fast as possible while the stability of the flight control system is maintained. A Boeing 747 model is used as a test bed, and the simulations are carried out on two different crosswind conditions to demonstrate the feasibility and effectiveness of the proposed method.

Assessment of dynamic pairwise wake vortex separations for approach and landing at Vienna airport

The Wake Vortex Prediction System WSVS (WirbelSchleppenVorhersageSystem) has been developed to tactically increase airport capacity by employing dynamically adjusted aircraft separations for approach and landing without compromising safety. For this purpose, the WSVS considers the involved aircraft type pairing, the prevailing weather conditions, and the resulting wake vortex behavior. A Monte Carlo simulation study demonstrates that the WSVS is well adjusted to a reasonable level of safety. The simulation study evaluates the probability that wake vortices still linger within defined radii around the follower aircraft and compares this probability to measurement data collected at five major international airports. The potential of the WSVS to optimize aircraft separations is assessed by employing twelve months of traffic and weather prediction data collected at Vienna International Airport. Analyses of the separation reduction potential are established and compared to current regulations. Dependencies on prevailing headwind and crosswind conditions are discussed in terms of individual wake vortex behavior and statistical distributions of wake turbulence separations. The results indicate that substantial potential for safely reduced aircraft separations exists mainly under sufficiently strong crosswind conditions for any aircraft type combination requiring wake vortex separation minima.

Optimization for Circulating Cooling Water Distribution of Indirect Dry Cooling System in a Thermal Power Plant under Crosswind Condition with Evolution Strategies Algorithm

Crosswind has an adverse impact on the performance of an indirect dry cooling system. In order to mitigate the adverse influence, this study redistributed the circulating cooling water among air-cooled heat exchanger sectors so that the performance of the indirect dry cooling system could be improved. An evolution strategies algorithm combined with numerical effectiveness-based heat exchanger model was established to minimize the operation costs of the whole system. Based on a 660 MW practical power plant, optimal circulating cooling water operation strategies under varied crosswind speeds and ambient temperatures were calculated to show its application. According to the calculated results, the performance of the indirect dry cooling system could be enhanced by optimizing circulating cooling water distribution under any crosswind speed, especially under high ambient wind speeds. There is a slight promotion of the coal savings with a rise in ambient temperature: improvements of about 5%. The standard coal consumption rate could save as much as 2.50 g/kWh under crosswind speed of 10 m s−1 and ambient temperature of 32 °C, compared to the 0.1 g/kWh under crosswind speed of 2 m s−1 and ambient temperature of 32 °C.

Learning to Have a Civil Aircraft Take Off under Crosswind Conditions by Reinforcement Learning with Multimodal Data and Preprocessing Data.

Autopilot technology in the field of aviation has developed over many years. However, it is difficult for an autopilot system to autonomously operate a civil aircraft under bad weather conditions. In this paper, we present a reinforcement learning (RL) algorithm using multimodal data and preprocessing data to have a civil aircraft take off autonomously under crosswind conditions. The multimodal data include the common flight status and visual information. The preprocessing is a new design that maps some flight data by nonlinear functions based on the general flight dynamics before these data are fed into the RL model. Extensive experiments under different crosswind conditions with a professional flight simulator demonstrate that the proposed method can effectively control a civil aircraft to take off under various crosswind conditions and achieve better performance than trials without visual information or preprocessing data.

Numerical investigation of swirl effects on a short natural draft dry cooling tower under windless and crosswind conditions

Swirling motions have been proven to improve the thermal performance of short natural draft dry cooling towers by reducing the cold air inflow and increasing the draft speed. However, crosswind influences on the favourable swirl effects have not been investigated. To fill this gap, 3-Dimensional simulations of a short natural draft dry cooling tower are carried out. Three different locations of the swirl generator, with solid body rotation, are compared under windless and crosswind conditions. The results show that, with no wind present, introducing swirling motions right above the heat exchangers is found to be the optimal location for improving around 40% of the reduced thermal performance, which is casued by cold air inflow penetration. On the other hand, as the swirl intensity further increases after the cold air inflow is eliminated, locating it at the tower outlet performs the best on the air draft speed enhancement, and thus further increases approximately 17% of the heat transfer rate at the angular frequency input of 2s-1. In the presence of crosswind and windbreak walls, air flows through the heat exchangers and tower non-uniformly. By mounting the swirl generator right above the heat exchangers, the uniform index of the heat flux can be improved by 5% with 1s-1 angular frequency input. More importantly, inducing swirls at the tower outlet is still the optimal choice for increasing the air draft speed through the tower. With 2s-1 angular frequency input, the thermal performance of the tower can be enhanced by 11~17% in accordance with the crosswind speed.

Flow Separation Control of Nacelle in Crosswind by Microsecond Pulsed Surface Dielectric Barrier Discharge Plasma Actuator

Flow separation under crosswind conditions seriously jeopardizes the quality of the nacelle’s flow field. In this paper, microsecond pulsed surface dielectric barrier discharge (μSDBD) is used to suppress the flow separation and reduce the crosswind distortion of the nacelle. The flow structure induced by the μSDBD is first explored by a high-speed schlieren system. The pressure waves composed of a cylindrical wave surrounding the electrodes and a flat wave at the top of the cylindrical one can be perceived, which indicates the fast gas heating produced by the μSDBD. A set of wind tunnel tests are then conducted to verify the ability of μSDBD to suppress the nacelle flow separation and study the influence laws of pulse frequency, coverage area, and the actuator layout on the flow control effects. Results show that plasma actuation can not only improve the total pressure at the exit of the nacelle but also suppress the flow distortion caused by the crosswind. The best flow control effect can be achieved at the pulse frequency of 500 Hz, with the value of sectional distortion coefficient reduced by 57.76% compared with the baseline condition. The flow control effect with the plasma actuator covering 120° of the nacelle perimeter is better than that of 60° and 180° coverage, showing the highest flow control efficiency in the 120° condition. The μSDBD can improve mixing between the boundary layer and the main flow, enhancing the ability of the boundary layer to resist the adverse pressure gradient, which is beneficial to flow separation control.

Preliminary study on crosswind aerodynamics for a group of road race cyclists

Under crosswind conditions, road cyclists experience an extra drag force and a destabilising lateral force. In these conditions a group of cyclists manages to reorganise its spatial formation to minimise these forces forming an echelon, i.e a diagonal single pace line of riders staggered across the road, a configuration which is markedly different from those adopted in wind-free conditions. To study the effect of the crosswind on drag and lateral forces on the riders we performed wind-tunnel experiments using a scale model cyclist and measuring the forces by means of a load cell. Several configurations with one, two, and four cyclists have been investigated varying yaw angles. Results show that, in a basic 4 rider configuration at a 50 ^{circ } yaw angle, a sheltered rider within the echelon experiences less than 30% of the drag of the guttered rider behind the echelon, struggling against the crosswind. Furthermore, we show that an echelon is worth being adopted under crosswind conditions only beyond a 30 ^{circ } yaw angle. At this critical 30 ^{circ } yaw angle the drag on the guttered rider doubles when the gap to the front group increases from 10 cm to 1 m (in real scale). These results can be of interest in defining road cycling race strategies and they allow some significant configurations to be identified and further investigated in more complex experiments.

Numerical Investigation on the Influence of the Streamlined Structures of the High-Speed Train’s Nose on Aerodynamic Performances

The structural design of the streamlined shape is the basis for high-speed train aerodynamic design. With use of the delayed detached-eddy simulation (DDES) method, the influence of four different structural types of the streamlined shape on aerodynamic performance and flow mechanism was investigated. These four designs were chosen elaborately, including a double-arch ellipsoid shape, a single-arch ellipsoid shape, a spindle shape with a front cowcatcher and a double-arch wide-flat shape. Two different running scenes, trains running in the open air or in crosswind conditions, were considered. Results reveal that when dealing with drag reduction of the whole train running in the open air, it needs to take into account how air resistance is distributed on both noses and then deal with them both rather than adjust only the head or the tail. An asymmetrical design is feasible with the head being a single-arch ellipsoid and the tail being a spindle with a front cowcatcher to achieve the minimum drag reduction. The single-arch ellipsoid design on both noses could aid in moderating the transverse amplitude of the side force on the tail resulting from the asymmetrical vortex structures in the flow field behind the tail. When crosswind is considered, the pressure distribution on the train surface becomes more disturbed, resulting in the increase of the side force and lift. The current study reveals that the double-arch wide-flat streamlined design helps to alleviate the side force and lift on both noses. The magnitude of side force on the head is 10 times as large as that on the tail while the lift on the head is slightly above that on the tail. Change of positions where flow separation takes place on the streamlined part is the main cause that leads to the opposite behaviors of pressure distribution on the head and on the tail. Under the influence of the ambient wind, flow separation occurs about distinct positions on the train surface and intricate vortices are generated at the leeward side, which add to the aerodynamic loads on the train in crosswind conditions. These results could help gain insight on choosing a most suitable streamlined shape under specific running conditions and acquiring a universal optimum nose shape as well.

Airplane Vortices Evolution Near Ground

Airport traffic around the world has sharply increased over the years; as a result, airports need to be enlarged and the landing or taking off times between two consecutive airplanes must be reduced. To precisely determine the minimum time required between two consecutive airplanes, it is essential to understand the main physical characteristics of the vortices generated under airplanes’ wings and their evolution under different atmospheric conditions. In the present paper, such information is obtained through the complex potential equation of a vortex together with the potential Bernoulli equation. The process starts with the characteristic complex potential equation, which is simplified to find the velocity potential function. Then, the temporal movement of the vortices’ central core, the velocity and pressure fields around the vortical structures and the effect of the crosswind on the vortices’ displacement, velocity and pressure fields are obtained. The paper shows how optimizing the process of measuring and calculating the vortices’ behavior could save a certain amount of time between airplanes, therefore increasing airport throughput. This paper introduces a potential flow method, which is coupled with the temporal variation of the flow circulation, to predict the vortices’ behavior and movement over time. The inclusion of circulation decay over time is employed to simulate the viscosity effect over the vortical structures. The in-house code generates results in less than one minute and needs to be seen as a tool to determine, for each airport and crosswind condition, the minimum time needed between two consecutive airplanes.

Aerodynamic noise of propeller and shroud of multi-rotor drone in cross-wind conditions

Aerodynamic noise of propeller and shroud of multi-rotor drone in cross-wind conditions

Modeling a Large Air-Cooled Condenser

This study reports on a modeling strategy for large Air-Cooled Condensers (ACCs). A large 64-fan ACC was modeled under various crosswind conditions that investigated the ACC’s specific axial flow fan configuration. The ACC model was developed in two parts, an axial flow fan model and a heat exchanger model. The axial flow fans were modeled using an Actuator Disk Model (ADM). The heat exchangers’ pressure drop was modeled using the Darcy-Forchheimer porosity model, and the Effectiveness Number of Transfer Units (ε-NTU) method was used to determine the air heat transfer rate. The ACC was configured using two different axial flow fans, identified in this study as the L-fan and the N-fan. Comparatively the L-fan has a steeper fan static pressure characteristic curve than that of the N-fan, at the cost of a greater shaft power consumption. Under normal operating conditions the average heat-to-power ratios were calculated at 89.91 W/W for the L-fan and 102.48 W/W for the N-fan. Under crosswind conditions of 9 m/s the heat-to-power ratios of the leading edge fan-units decreased by 80.6% and 87.0% for the L-fan and N-fan respectively. However, at the fan-units immediately downstream of the leading edge the heat-to-power ratios only decreased by 34.1% for the L-fan and 64.2% for the N-fan.

Observation of Aircraft Wake Vortex Evolution under Crosswind Conditions by Pulsed Coherent Doppler Lidar

The observation and identification of wake vortex are considered important factors to reduce aviation accidents and increase airport capacity. In addition to aircraft parameters, the evolution process of the wake vortex is strongly related to atmospheric conditions, including crosswind, headwind, atmospheric turbulence, and temperature stratification. Crosswind generally affects the wake vortex trajectories by transporting them to the downwind direction. Additionally, the circulation attenuation of wake vortex is also influenced by crosswind shear or turbulence related to crosswind. This paper implemented the range height indicator (RHI) scanning mode of pulsed coherent Doppler lidar (PCDL) to study the influence of crosswind on wake vortex evolution. The crosswind was obtained from the non-wake vortex regions of the RHI sectors. The method, based on the measurements of radial velocity and spectrum with the broadening feature, was performed to locate wake vortex cores. The wake vortex trajectories with various crosswind strengths were comprehensively analyzed.

Modeling the Motion of an Aircraft during Vertical Landing in Crosswind Conditions

The paper considers the problem of increasing the safety of landing for small unmanned aerial vehicles under unfavorable external conditions, in particular, in the presence of gusty crosswind. A mathematical model describing the landing of a small unmanned aerial vehicle in the presence of aerodynamic flows and the stabilization in the XY plane is presented.

Influence of bottom wall on characteristics of jet diffusion flames under cross-wind

This study investigated the influence of different rear bottom wall lengths on the blow-out limit, flame shape, flame mean length, and flame tilt angle of jet diffusion flames under cross-wind conditions. The experimental results reveal that the bottom wall had a significant effect on the flame blow-out limit. The flame blow-out velocity was maximum only when the front bottom wall existed, and all jet diffusion flames had similar blow-out velocity under the influence of the rear bottom wall. Once the length of the rear bottom exceeded a certain value, the jet diffusion flames were prone to lift-off. Moreover, the jet diffusion flames adhered to the bottom wall, which is attributed to the Coanda effect. The flame length significantly increased under the influence of the bottom wall. Additionally, under the influence of the front bottom wall, the flame length was maximum when the cross-wind velocity was higher. Under the influence of different rear bottom wall lengths, the flame tilt angle was divided into two variation regions. Among them, the flame tilt angle affected only by the front bottom wall was minimum. The flame tilt angle was maximum when the rear bottom wall length was 20 cm. Finally, the empirical formula of the jet diffusion flame tilt angle was obtained by analogy analysis and exhibited good correlation with the experimental data.

Experimental study of carriage fire in a tunnel: Evolution of flame geometry characteristics under relative strong crosswinds

The present study investigated experimentally the effects of relative strong crosswinds on the flame geometry characteristics (flame height and flame horizontal length) from carriage fires in a tunnel, which have not been quantified previously. Overall 144 test conditions were involved for various heat release rates, crosswind speeds and opening sizes. It was found that, with increase in crosswind speed till relative strong conditions, the flame height first decreased then remained nearly unchanged, while the flame horizontal length first increased then decreased. Finally, the flame is blown-off at strong crosswind conditions. A physical model is proposed to interpret and characterize the evolution behavior of these flame geometry characteristics with crosswind till relative strong condition. Two non-dimensional parameters, the wind Froude number and the dimensionless excess heat release rate, were found based on the analysis of the controlling mechanisms including the flame tilt and air combustion with excess fuel outside the carriage. The experimental results were shown to be well represented by the proposed parameters. This study provides quantitative data and basic understanding of the flame geometry characteristics under relative strong crosswinds from carriage fires in a tunnel.