Search

• A numerical simulation was conducted to analyze the susceptibility to crosswinds during the spraying of the air cooler. • The flow field temperature within the skid-mounted CNG air cooler when subjected to crosswind conditions was analyzed. • The installation of baffles enhances the air intake of the cooler, which effectively eliminates the adverse effects of ambient wind. Air cooler is a critical heat dissipation equipment applied in the field of oil and gas storage, which is mainly used to control the temperature during oil and gas storage and ensure the safety of oil and gas storage. After the installation of the spray cooling system on the skid-mounted compressed natural gas (CNG) air cooler Suqiao gas storage, the inlet air temperature of the air cooler decreases, resulting in reduced compressor power consumption. This effectively addresses the issue of unit shutdown due to high temperatures during the summer. However, the actual spray effect on-site reveals the impact of crosswinds, which poses a challenge. In this study, the flow field and causes of the skid-mounted CNG air cooler equipped with a spray cooling system under the influence of crosswinds are analyzed. Additionally, a solution involving the installation of a baffle is proposed. The results highlight that crosswinds have an adverse effect on outdoor spray cooling. With the installation of the baffle, the low-temperature area expands, resulting in lower temperatures. The cooling range is approximately 2 K, effectively counteracting the negative effects of crosswinds. [ABSTRACT FROM AUTHOR]

This research presents an improvement to the traditional solar updraft tower, which relies solely on solar energy and cannot operate continuously throughout the day. The enhancement involves a hybrid energy approach by installing a vortex generator at the top of the tower to convert crosswinds into a vortex flow at the chimney's top. This modification induces an updraft within the tower, enabling it to generate electricity continuously, even at night when there is no sunlight. The aim is to enable the solar updraft tower to harness crosswind energy without altering the tower's main structure. This involves developing a vortex generator from a unidirectional wind intake design to a three‐directional intake, enhancing the feasibility of commercial installation. Additionally, various designs and heights of vortex generators were developed, considering different crosswind speeds (2, 4, 6, and 8 m/s). The research utilizes the finite element method, along with real model construction, to validate the reliability of the study's findings. The results indicate that the updraft speed is directly proportional to the crosswind speed. From a physical standpoint, the vortex generator with a height equal to D produced the best results in all experiments. The square, cylindrical, and diffuser shapes increased the wind speed inside the chimney by 60%, 41%, and 48%, respectively. These results from various shapes provide effective design and development guidelines for the future commercial use of vortex generators. [ABSTRACT FROM AUTHOR]

Flying cars, or vertical takeoff and landing (VTOL) aircraft, are revolutionary devices that can address traffic congestion and help build a three-dimensional transportation system in the future. Flight safety could deteriorate in actual flight because ducted fans may suffer from significant thrust fluctuations induced by crosswinds. In this article, we propose a variable-speed control method to reduce thrust fluctuations by applying a speed waveform opposite to the fluctuation waveform. We choose a typical condition of a 5 m/s crosswind for validation. The results of unsteady Reynolds averaged Navier‒Stokes (URANS) calculations show that crosswinds lead to fluctuations in all thrusts with the frequency of the blade passing frequency. The total thrust fluctuation amplitude accounts for 6.2% of the total thrust. By applying the variable-speed control where the frequency is identical to the thrust fluctuation frequency, the phase difference is 180 degrees, and the amplitude is approximately the square root of the fluctuation amplitude, the standard deviation of the thrust fluctuation is reduced by 92% without affecting the mean total thrust. Fluctuations in other performance parameters, such as lateral force and pitching moment, are improved as well. This active control method can achieve accurate control without any auxiliary equipment and has good application prospects. It provides a promising idea for solving the problem of performance fluctuations in turbomachinery. [ABSTRACT FROM AUTHOR]

This work presents a numerical study on flow configurations and pressure distribution of cylindrical towers attached with different shapes of vortex generators. The vortex‐generator attachment is done with the main aim of reducing the energy of ventilation for the cylindrical tower. The two different types of vortex generators, namely, a cylindrical‐shaped vortex generator and a diffuser‐shaped vortex generator, are compared with an original square‐shaped vortex generator. The effects of air velocity (2, 4, 6, and 8 m/s) and vortex generator size (D/2, D, and 2D) on flow structure are considered. The finite element method (a commercial code) is selected for the main problem‐solving. The numerical models of the cylindrical towers attached with various vortex generators are validated to confirm the reliability of the numerical results. From the numerical results, it was found that the suctioned updraft speed in the tower was proportional to the crosswind speed. In addition, the vortex generator with h = 2D performs the highest updraft speed, which leads to the best efficiency for ventilation. [ABSTRACT FROM AUTHOR]

Large quantities of sand carried by crosswinds often settle in the cabin of diesel locomotives operating in desert regions. This study adopts an Euler-Lagrange two-phase flow model to simulate sand movement and deposition in a running diesel locomotive through the ventilation grilles. The realistic sand particle diameter distribution obtained from the field test is incorporated by the Rosin-Rummler model in computational fluid dynamics software. The realizable k-ε turbulent model is adopted to simulate the turbulence. The operation of the locomotive on a straight track at 200 km/h with five different crosswind velocities is studied numerically. The simulation results indicate that the increment of crosswind speed leads to higher pressure on the grille and the velocity of the internal flow field. The relationship between the number of sand particles trapped inside the car and the incident angle (i.e., resultant wind angle) is discovered. It is evident that the majority of sand particles enter the compartment through the windward tail grilles. Therefore, the influence of adjusting the tilt angle of the tail grille on the sand entering the locomotive cabin is calculated. It is discovered that the compartment experiences the least sand deposition at a 30° title angle. Therefore, optimizing the tilt angle of the frame for grilles can significantly enhance the filtering of the grille. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aerodynamic loads of a sedan experience significant fluctuations when passing by a sand dune at the roadside under crosswinds, which can easily cause yawing and overturning. Computational fluid dynamics (CFD) methods, based on different turbulence modeling approaches, yield different aerodynamic results for sedans. This study aims to investigate the effects of three prevailing turbulence modeling approaches (renormalization group (RNG) k-ε, large eddy simulation (LES), and improved delayed detached eddy simulation (IDDES)) on the aerodynamic characteristics of a sedan passing by a sand dune under crosswinds. The CFD dynamic mesh models are constructed using the "mosaic" mesh technique to account for the dune–air–sedan interaction. The reliability of the CFD prediction method is verified by comparing it with field test results. The predictive capabilities of the three turbulence modeling approaches are compared in terms of aerodynamic loads and flow field characteristics. The simulation of sand particle movement is conducted through the discrete phase model, aiming to assess the impact of wind–sand flow on the aerodynamic properties of sedans. Corresponding results show that the aerodynamic loads predicted by the LES model closely match (within 4.4–7.5%) the corresponding data obtained from field tests. While the IDDES and LES models demonstrate similar abilities in characterizing the wind field details, and their results exhibit maximum differences of 8.3–15.7%. Meanwhile, the maximum difference between the results obtained by the RNG k-ε and LES models ranges from 14.8% to 18.4%, attributed to its inability to capture subtle changes in the vortex structure within the flow field. This work will provide a numerical modeling reference for studies on the wind–sand flow and the aerodynamic characteristics of sedans running through the desert, and it has implications for the safe driving of sedans under extreme conditions. [ABSTRACT FROM AUTHOR]

Crosswind and angle of attack are critical factors that influence the safe operation of civil aviation engines, which are also essential criteria in the certification of civil engine airworthiness. Conducting research on the effects and mechanisms of angle of attack and crosswind on the integrated characteristics and flow field of nacelle and fan holds significant engineering value. In this study, a high-bypass-ratio turbofan engine serves as the research subject, and the influence of crosswind and angle of attack coupling on the nacelle intake and fan components is analyzed using numerical simulations. The numerical research findings indicate that both individual angle of attack and crosswind, as well as their combination, lead to a specific range of total pressure distortion in the inlet. At an angle of attack of 25°, the extent and degree of circumferential total pressure distortion formed on the aerodynamic interface exhibit minor variations under different crosswind inflow conditions. Under two operating conditions involving left crosswind and right crosswind, both characterized by an angle of attack of 25° and a wind speed of 20 m/s, the combined effects of crosswind and angle of attack on the fan and outlet guide vane (OGV) components are mainly concentrated at the blade tip. These influencing factors collectively lead to total pressure distortion in the inlet flow field, resulting in the interaction between tip leakage flow and passage shock waves. At the same angle of attack, there are differences in the impact of total pressure distortion caused by crosswinds in two directions on the fan. Under the same operating conditions, the total pressure distortion induced by the right crosswind has a greater impact on OGV. [ABSTRACT FROM AUTHOR]

Purpose – Express freight transportation is in rapid development currently. Owing to the higher speed of express freight train, the deformation of the bridge deck worsens the railway line condition under the action of wind and train moving load when the train runs over a long-span bridge. Besides, the blunt car body of vehicle has poor aerodynamic characteristics, bringing a greater challenge on the running stability in the crosswind. Design/methodology/approach – In this study, the aerodynamic force coefficients of express freight vehicles on the bridge are measured by scale model wind tunnel test. The dynamic model of the train-long-span steel truss bridge coupling system is established, and the dynamic response as well as the running safety of vehicle are evaluated. Findings – The results show that wind speed has a significant influence on running safety, which is mainly reflected in the over-limitation of wheel unloading rate. The wind speed limit decreases with train speed, and it reduces to 18.83 m/s when the train speed is 160 km/h. Originality/value – This study deepens the theoretical understanding of the interaction between vehicles and bridges and proposes new methods for analyzing similar engineering problems. It also provides a new theoretical basis for the safety assessment of express freight trains.

Flying cars, or vertical takeoff and landing (VTOL) aircraft, are revolutionary devices that can address traffic congestion and help build a three-dimensional transportation system in the future. Flight safety could deteriorate in actual flight because ducted fans may suffer from significant thrust fluctuations induced by crosswinds. In this article, we propose a variable-speed control method to reduce thrust fluctuations by applying a speed waveform opposite to the fluctuation waveform. We choose a typical condition of a 5 m/s crosswind for validation. The results of unsteady Reynolds averaged Navier‒Stokes (URANS) calculations show that crosswinds lead to fluctuations in all thrusts with the frequency of the blade passing frequency. The total thrust fluctuation amplitude accounts for 6.2% of the total thrust. By applying the variable-speed control where the frequency is identical to the thrust fluctuation frequency, the phase difference is 180 degrees, and the amplitude is approximately the square root of the fluctuation amplitude, the standard deviation of the thrust fluctuation is reduced by 92% without affecting the mean total thrust. Fluctuations in other performance parameters, such as lateral force and pitching moment, are improved as well. This active control method can achieve accurate control without any auxiliary equipment and has good application prospects. It provides a promising idea for solving the problem of performance fluctuations in turbomachinery.

In this paper, an adaptive backstepping-based control scheme is proposed to perform autonomous lateral maneuvers under significant lateral offset in the center of gravity (c.g.) position in a UAV. It is first shown that the coupled equations of motion arising from lateral c.g. shift can be simplified and cast in block strict feedback form making it amenable to a two-step backstepping control design. Useful nonlinear terms in the equations of motion are identified and retained in the backstepping design to ensure a less conservative control. Adaptation law is incorporated to dynamically adjust to changes in the c.g. position by adding an adaptive term to each step of the backstepping control. Lyapunov’s direct method and LaSalle’s invariance principle are applied to establish asymptotic stability of both tracking errors and errors in the c.g. estimate. To validate the effectiveness of the proposed control strategy, simulation results for horizontal turn maneuver are presented for the fixed wing Aerosonde UAV and maneuver performance is observed to remain highly insensitive to a wide range of lateral c.g. positions on either side of the fuselage centerline. Furthermore, a comparative control performance analysis is carried out against an ad-hoc model-based adaptive backstepping control scheme available in the literature and the results show significant performance enhancement in the proposed scheme. Along with the c.g. variations, the effects of steady crosswind are also investigated and the control formulation is modified to mitigate these effects too. Real-time control hardware in loop simulations are also provided in support of the real time viability of the proposed control. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

When high-speed trains (HSTs) meet on a bridge in a crosswind environment, the train on the windward side (TWS) will produce a wind-shielding effect similar to a windbreak. This effect, coupled with the instantaneous pressure wave generated at the time of the meeting, will cause an abrupt variation in the aerodynamic load of the train on the leeward side (TLS) during the meeting process, thereby affecting the safe and stable operation of the train. This study analyzed the factors affecting the degree of the abrupt variation in the aerodynamic load of the TLS during the meeting, and studied the change rule of the safety index of the TLS under different wind speeds. In addition, we also explored the impact of three types of ventilation rate curved wind barriers on the abrupt variation in the aerodynamic load of the TLS during the meeting. The research results show that the increase in crosswind speed will increase the degree of the abrupt variation in the aerodynamic load of the TLS, further exacerbating the impact on the safe and stable operation of the TLS. Although the increase in train speed will reduce the magnitude of the abrupt variation in the aerodynamic load of the TLS during the meeting, it will increase the rate of abrupt variation. However, a curved wind barrier with a ventilation rate of 30% can effectively alleviate the abrupt variation in the aerodynamic load of the TLS during the meeting. These research results have important reference value for improving the driving safety of HSTs in crosswind environments. [ABSTRACT FROM AUTHOR]

Objective When urban rail transit trains operate on elevated tracks, crosswinds have a significant impact on the stability and safety of vehicle operation. It is essential to conduct a more in-depth study on the dynamics performance of metro vehicles under crosswind action. Method Three classical crosswind load models (classical constant steady-state wind load model, transient Chinese hat wind load model, and non-steady-state stochastic wind load model) in MATLAB software are employed to simulate dynamic wind fields. In SIMPACK software, a detailed rigid-body dynamics model of a single-car formation train is established. The three wind load models are applied as external excitations to the vehicle. Comparative analysis is conducted on the influence of different wind load models, wind speeds, and vehicle speeds on the operational stability of metro vehicles when operating on straight tracks. From a safety design perspective, the non-steady-state stochastic wind load model is selected to analyze the stability and safety of the vehicle during curve negotiation, exploring the safety domain of vehicle speeds under different wind speeds. Result & Conclusion Under crosswind action, both metro vehicle speed and wind speed significantly influence vehicle operational stability and safety. During train high-speed running, wind speed has a more pronounced impact on the lateral vibration of the vehicle. Among the three crosswind load models, the non-steady-state stochastic wind load model has the most significant impact on vehicle stability. Based on the analysis of vehicle stability and safety, speed limits for vehicles are determined for different route geometries (straight or curve tracks) and wind speeds.

Accurate range prediction requires good knowledge of the prevailing wind conditions and how they affect the energy consumption of the ego vehicle. A few different simplified vehicle air drag models that explicitly include the effect from crosswinds are presented and compared through some objective criteria. The models are developed from the normal air drag equation where the effect from wind is implicit and therefore often forgotten or neglected. The purpose is to find a low-complexity model complementing CFD models and wind tunnel tests, that can be used for range estimation and predictive energy management algorithms. To simplify online estimation, a requirement is that the air drag models only contain a few tuning parameters. The models are validated against CFD calculations for a few vehicle combinations and the best models show good accuracy for air attack angles up to at least 60 degrees. It is shown that the parameters of the simplified models can loosely be connected to some basic geometrical attributes of a vehicle combination so it should be possible to give at least a rough estimate of the parameters of a simplified model based on these geometrical attributes. This is useful for making a first estimate of the aerodynamic properties of a vehicle combination after major changes in the exterior, e.g. when adding a trailer. It also highlights that the size and the shape of the vehicle side may be mainly responsible for the high longitudinal air drag sensitivity to crosswinds for large vehicle combinations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper describes the use of wireless smart sensors for examining the underlying mechanism for the wind-induced vibration of high-mast illumination pole (HMIP) structures. HMIPs are tall, slender structures with low inherent damping. Video recordings of multiple HMIPs showed considerable vibrations of these HMIPs under wind loading in the state of Kansas. The HMIPs experienced cyclic large-amplitude displacements at the top, which can produce high-stress demand and lead to fatigue cracking at the bottom of the pole. In this study, the natural frequencies of the HMIP were assessed using pluck tests and finite element modeling, and the recorded vibration frequencies were obtained through computer vision-based video analysis. Meanwhile, a 30.48 m tall HMIP with three LED luminaires made of galvanized steel located in Wakeeney, Kansas, was selected for long-term vibration monitoring using wireless smart sensors to investigate the underlying mechanism for the excessive wind-induced vibrations. Data analysis with the long-term monitoring data indicates that while vortex-induced vibration occurs frequently at relatively low amplitude, buffeting-induced vibration was the leading cause of the excessive vibrations of the monitored HMIP. The findings provide crucial information to guide the design of vibration mitigation strategies for these HMIP structures. [ABSTRACT FROM AUTHOR]

To study the evolution of the pantograph-catenary system dynamic under crosswind environments, this paper examines the effect of crosswind on the quality of the current collection and explores the wind stability of different longitudinal suspension forms of the catenary system. Firstly, the catenary with different longitudinal suspension forms is established based on the absolute node coordinate formulation, and the initial equilibrium configuration are accurately obtained. Secondly, the pantograph model is derived, and the pantograph-catenary system coupling model is established according to the standard EN 50318:2018 and passed the verification. Then, the random wind speed spectrum of the simulated environment is built based on the Davenport spectrum and is validated. Finally, the pantograph-catenary system dynamic behavior under the crosswind environments is simulated. The results show that the crosswind affects the low-frequency vibration part of the pantograph-catenary system, with the increase in wind speed and the standard deviation of contact force, the worse current collection quality. Different longitudinal suspension forms of catenary systems have various wind stability. Semi-inclined and inclined longitudinal suspension forms have better wind stability, and the maximum reduction of contact force standard deviation is 14.05%, which can effectively improve the current collection quality in crosswind environments. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Urban Mass Transit is the property of Urban Mass Transit Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High-speed trains (HSTs) transiting subgrade-cutting transition sections in crosswinds have become a common operating scenario. This paper utilizes the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model, considers air compressibility, and establishes a three-dimensional coupled train-subgrade-wind dynamics model. The aerodynamic load (AL) variation rules of trains and discrepancies in the flow field mechanisms when HSTs transit various types of subgrade-cutting transition sections [half cutting and half flat (HCHF), double side cutting (DC), and half cutting and half embankment (HCHE)] under crosswind conditions are revealed using this model. The results indicate the following. (1) The aerodynamic performance deteriorates when trains transit three subgrade-cutting transition sections under crosswinds. (2) As trains enter the transition section from a flat approach, the head car’s AL power spectrum density (PSD) is the largest when operating in the DC case. (3) After the train drives into the subsequent operating scenario, the average of the AL in the DC case is the lowest. (4) In the DC case, a slope of 1:0.75 should be taken as the basis for the design of the corresponding cutting parameters. (5) After the train enters the cutting, the winding flow speed and number of vortex structures surrounding the trains increase significantly.

Crosswind is the primary external excitation source of the straddle monorail system. To ensure the ride quality of the monorail system under crosswind, based on multi-rigid body dynamics and finite element method, the coupling model of the monorail vehicle-beam is established, in which the track beam is considered as a flexible sub-model; the vehicle includes traveling/steering/stabilizing wheels and evaluate the characteristics of tire sideways and slip. Crosswind was obtained by the Davenport spectrum and loaded on the vehicle. Dynamic responses of the vehicle-beam system and the safe running/wind speed were studied. The study shows that, for a car, the wind loaded outside balances part of the centrifugal action and eliminates part of the overturning trend of the vehicle when it turns but makes the lateral ride comfort deteriorate in the straight line section. For the beam, the wind loads help reduce the track beam's transverse deformation when cars pass, and the vertical deformation is slightly improved. For operation, when the running speed is less than 50 km/h and the wind speed is less than 15 m/s, the monorail vehicle can operate safely. The straddle monorail wind-vehicle-beam model can conveniently update the design parameters for dynamic calculation and comfort evaluation. It can provide a specific theoretical basis or guiding principles for the safe operation of straddle monorail vehicles under wind loads. [ABSTRACT FROM AUTHOR]

Through the comparison and analysis of three numerical simulation methods, the optimal simulation scheme was obtained. Therefore, the separation vortices method was used to study the aerodynamic characteristics of Ahmed model, and the influence of different side wind angles on the distribution law of vorticity, turbulence intensity, pressure and streamline of blunt body wake was analyzed. The variation characteristics of force and moment coefficient were obtained, and the comprehensive formula of tail inclination angle changing with side wind angle was summarized. The results show that the influence of the side wind angle on the characteristic parameters of the blunt body wake is not monotonous, and the rear vorticity of the blunt body is the largest when the side wind angle is 30°. The inclination angle and aerodynamic coefficient of the wake of the blunt body increase with the increase of the side wind angle. Back windward side pressure and average head speed of the blunt body also reach maximum values at a side wind angle of 50°. The conclusions provide some basis for the safety and stability of vehicle operation under complex transverse inflow conditions. [ABSTRACT FROM AUTHOR]

High-speed trains (HSTs) transiting subgrade-cutting transition sections in crosswinds have become a common operating scenario. This paper utilizes the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model, considers air compressibility, and establishes a three-dimensional coupled train-subgrade-wind dynamics model. The aerodynamic load (AL) variation rules of trains and discrepancies in the flow field mechanisms when HSTs transit various types of subgrade-cutting transition sections [half cutting and half flat (HCHF), double side cutting (DC), and half cutting and half embankment (HCHE)] under crosswind conditions are revealed using this model. The results indicate the following. (1) The aerodynamic performance deteriorates when trains transit three subgrade-cutting transition sections under crosswinds. (2) As trains enter the transition section from a flat approach, the head car's AL power spectrum density (PSD) is the largest when operating in the DC case. (3) After the train drives into the subsequent operating scenario, the average of the AL in the DC case is the lowest. (4) In the DC case, a slope of 1:0.75 should be taken as the basis for the design of the corresponding cutting parameters. (5) After the train enters the cutting, the winding flow speed and number of vortex structures surrounding the trains increase significantly. [ABSTRACT FROM AUTHOR]

This study investigates the performance of a natural draft dry cooling tower group in crosswind conditions through numerical analysis. A comprehensive three-dimensional model is developed to analyze the steady-state and dynamic behavior of the towers. The impact of wind speed and direction on heat rejection capacity and flow patterns is examined. Results indicate that crosswinds negatively affect the overall heat transfer capacity, with higher crosswind speeds leading to decreased heat transfer. Notably, wind direction plays a significant role, particularly at 0°. Moreover, tower response time increases with higher crosswind speeds due to increased turbulence and the formation of vortices. The response times are generally similar for wind directions of 45° and 90°, but differ when facing 0, where the leeward tower exhibits a shorter response time compared to the windward tower. These findings provide valuable insights into the performance of natural draft dry cooling tower groups under crosswind conditions, which can inform the design and operation of similar systems in practical applications. [ABSTRACT FROM AUTHOR]

Featured Application: The control, stability, or even safety of a vehicle can be influenced by crosswinds. The findings of the current study can be helpful for the reliable design of ground vehicles with less wind sensitivity early in their development processes. The development of lateral disturbance compensation algorithms and autonomous vehicles can also benefit from the results of the study. The general approach in the previous studies was to ignore the driver's steering contribution to a vehicle while investigating the interactions between crosswind and vehicle. Therefore, the goal of this study is to find out how steering inputs by drivers affect a heavy-ground vehicle's dynamic reaction to crosswinds. In the investigation, a two-way interaction between vehicle dynamics and aerodynamic simulations was employed. The steering inputs of drivers were modelled using a driver model taken from the previous literature that is able to reproduce the steering responses of a human driver. The study's findings demonstrated that the steering inputs made by drivers significantly impacted how the vehicle responded to crosswinds. For instance, the greatest lateral displacement of the least skilled driver (Driver 1) was around 1.53 times the greatest lateral displacement of the most skilled driver (Driver 3) at the delay time of tδ,delay = 0.5 s in the steering input. Additionally, the maximum lateral displacement results of Driver 1 and Driver 3 at tδ,delay = 1.0 s became 1.39 and 1.56 times greater than their maximum lateral displacement results at tδ,delay = 0.5 s. Similarly, the total steering inputs of Driver 1 and Driver 3 at tδ,delay = 1.0 s were 1.4 and 2.2 times greater than their total steering inputs at tδ,delay = 0.5 s, respectively. In general, the results of a driver who is more skilled than Driver 1 (Driver 2) fall in between the respective results of Driver 1 and Driver 3. On the other hand, each driver's total steering inputs at tδ,delay = 0.5 s were roughly the same as their total steering inputs at tδ,delay = 0 s. In all delay scenarios for the start of the driver's steering inputs, the drivers' steering inputs amplified the yaw moment applied to the vehicle. Meanwhile, they diminished the lateral force and roll moment. [ABSTRACT FROM AUTHOR]

Owing to the blunt car body and high design speed of express freight trains, the running safety is significantly affected by crosswinds when the train runs over a bridge; moreover, severe accidents, such as derailment or overturning may occur. Therefore, adequate measures should be adopted to avoid the occurrence of such accidents. In this study, a finite element model of the train, ballastless track, and parameterized 5-span simply supported girder bridge along with modal superposition method are adopted to establish the train-track-bridge coupling dynamic system. Numerical simulation of stochastic wind speed, wind tunnel tests, and computational fluid dynamics (CFD) simulation of vehicle-bridge scale model were conducted to calculate the wind load acting on the train and bridge. The dynamic responses of the bridge and train were evaluated to present the diagrams of wind and train speed limits for safe operation. The results indicated that the running safety of the vehicle declined with the wind and train speeds, and the wheel unloading rate was the most sensitive to wind speed. For safe operation, the train speed must be restricted if the mean wind speed is greater than 22.7 m/s, and an extreme scenario of derailment may occur for a mean wind speed of 34.0 m/s. In addition, the wind speed limit should be appropriately adjusted and improved according to the pier height of the bridge and terrain category. This research provides a theoretical basis and data support for the assessment of safety of express freight trains in actual operation. [ABSTRACT FROM AUTHOR]

Traditional deterministic aerodynamic optimisation cannot consider environmental uncertainty, which may lead to sensitivity issues. The present study proposes a robust design framework for the aerodynamic optimisation of high-speed trains, which accounts for the uncertain wind and its impact on crosswind stability. In this framework, a variance analysis method based on the Non- Intrusive Polynomial Chaos is proposed to determine the deformation area, and a parametric model is subsequently established. The Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is used as the optimiser to minimise the mean and variance of the aerodynamic response. The mean and variance can be quickly predicted by an uncertainty analysis approach combining Monte Carlo simulation and Kriging model. The framework is then applied to the optimisation of a high-speed train under crosswind. The results of the robust optimisation are compared with those of the baseline geometry and deterministic optimisation. The mean and variance of the rolling moment under crosswind are reduced by 2.26% and 3.37% respectively after optimisation, indicating that the performance and robustness are both improved. The proposed framework is effective for the engineering design of high-speed trains and can also provide a reference for the robust design of other aerodynamic shapes. [ABSTRACT FROM AUTHOR]

Vortex generators (VGs) have shown the potential to mitigate the train's operational instability issues caused by strong wind. Numerical simulations are used to predict the flow structures around a train with VGs of different heights. The improved delayed detached eddy simulation (IDDES) hybrid modeling method is adopted to predict the trailing vortices on the leeward field. The numerical method is validated by reproducing wind tunnel test results. The study results reveal that VGs are capable of reducing the rolling moment coefficient around the leeward rail of a train by about 5% ~ 15% while keeping the drag of the train still lower than its operational drag without crosswind. The control mechanism lies on that the streamwise vortices generated by VGs are attracted to the large-scale trailing vortices, resulting in the pressure on the leeward wall rising. The differences in the domain frequencies between VGs and Baseline cases in POD modes indicate that the VGs changed the periodicity and symmetry of the vorticity fluctuation. This study provides a new method to improve the safety of trains under crosswinds. [ABSTRACT FROM AUTHOR]

High-temperature Superconducting (HTS) maglev trains are vulnerable to the effects of crosswinds when operating at high speeds in open-air conditions, potentially compromising riding comfort and safety. This study established a vehicle dynamic model based on the nonlinear maglev-track relationship and added aerodynamic loads under crosswinds to the train's simplified load center to address this issue. Using the maximum vibration acceleration limit and the Sperling index, we evaluated the riding comfort of the HTS maglev train under different conditions. Further, the vibration acceleration power spectral density was analyzed to reveal the impact of increasing the train's operating speed and crosswind speed. The results indicated that the lateral and vertical Sperling index achieved an "excellent" rating, even at crosswind speeds of up to 20.7 m/s when the train was traveling at speeds of up to 600 km/h. However, it was noted that particular attention should be given to the riding comfort in the head car when the speed reaches 600 km/h. Moreover, the influence of the increase in train speed on the vibration frequency domain distribution of the three car bodies and the train's riding comfort is greater than that of the increase in the crosswind speed. These findings may provide a valuable reference for the future engineering application of the HTS maglev train. [ABSTRACT FROM AUTHOR]

Development of power packs suspended under the diesel train towards high power and high integration has been driven by the development of technology. The wind environment of the railway lines is complex and variable, strong crosswind would exacerbate the complexity of the airflow around the train, impacting the cooling-fan performance of power pack, smoke dispersion, posing safety concerns. Using incompressible RANS equations and SST k-ω model, flow field around a diesel train, and effect of train speed, crosswind, and skirt board on cooling-fan flow and smoke dispersion are simulated and analyzed. Results reveal that airflow in power pack fans is affected by train speed and location, with the upstream fan exhibiting slightly higher airflow, especially in tail car power packs, with a difference of up to 7% (at 160 km/h). Skirt boards reduce fan airflow by about 6%. Crosswinds positively correlate with fan airflow variation, with windward and leeward fans experiencing increased and decreased airflow, respectively. Skirt board effectively reduces crosswind effects on power pack fans. Smoke intake into air-conditioning units (ACUs) correlates positively with train speed, particularly in downstream air-intakes of ACUs near smoke vents. Crosswinds significantly alter smoke distribution between leeward and windward sides of ACUs, especially at low crosswind speed. Smoke rarely enters ACUs when crosswind speed exceeds train speed. These findings offer insights for combustion-powered train operation and smoke vent design on train roofs.

The aerodynamic loads of a sedan experience significant fluctuations when passing by a sand dune at the roadside under crosswinds, which can easily cause yawing and overturning. Computational fluid dynamics (CFD) methods, based on different turbulence modeling approaches, yield different aerodynamic results for sedans. This study aims to investigate the effects of three prevailing turbulence modeling approaches (renormalization group (RNG) k-ε, large eddy simulation (LES), and improved delayed detached eddy simulation (IDDES)) on the aerodynamic characteristics of a sedan passing by a sand dune under crosswinds. The CFD dynamic mesh models are constructed using the “mosaic” mesh technique to account for the dune–air–sedan interaction. The reliability of the CFD prediction method is verified by comparing it with field test results. The predictive capabilities of the three turbulence modeling approaches are compared in terms of aerodynamic loads and flow field characteristics. The simulation of sand particle movement is conducted through the discrete phase model, aiming to assess the impact of wind–sand flow on the aerodynamic properties of sedans. Corresponding results show that the aerodynamic loads predicted by the LES model closely match (within 4.4–7.5%) the corresponding data obtained from field tests. While the IDDES and LES models demonstrate similar abilities in characterizing the wind field details, and their results exhibit maximum differences of 8.3–15.7%. Meanwhile, the maximum difference between the results obtained by the RNG k-ε and LES models ranges from 14.8% to 18.4%, attributed to its inability to capture subtle changes in the vortex structure within the flow field. This work will provide a numerical modeling reference for studies on the wind–sand flow and the aerodynamic characteristics of sedans running through the desert, and it has implications for the safe driving of sedans under extreme conditions.

In a complex environment, large bridges will present different adhesion coefficient, often accompanied by large crosswind, which makes the flow field around the vehicle complex and changeable. It is easy to cause unnecessary lane change and sideslip of the vehicle, which will affect the driving stability and lead to serious traffic accidents. Therefore, this paper studies the aerodynamic stability of cars passing through the bridge tower at high speed under different road adhesion and crosswind conditions. The detached-eddy simulation (DES) model was employed and the reliability of the DES model was verified by wind tunnel tests. An overlapping mesh technique was adopted to realize the motion of the vehicle. A multibody dynamic (MBD) model of the vehicle was established, and its robustness was verified. A two-way coupling model was then established based on the aerodynamic and MBD models. Subsequently, the aerodynamic characteristics and dynamic response of the vehicle passing through the bridge tower at a high speed were compared and analyzed using one-way and two-way coupling methods, with road adhesion coefficients of 1.0, 0.6, and 0.4 under crosswind conditions. The results show that the aerodynamic characteristics of the vehicle passing the bridge tower at a low adhesion coefficient under two-way coupling change evidently, and the trajectory and body attitude of the vehicle change significantly. As the adhesion coefficient of the road surface decreases, the vehicle passes through the bridge tower with a large lateral displacement and yaw angle. The maximum lateral force of −1406 N and the maximum yaw moment of 803 N∙m are generated when the car passes through the bridge tower under the two-way coupling with the adhesion coefficient of 0.4. Under two-way coupling, the lateral displacement and yaw angle caused by the bridge deck with an adhesion coefficient of 0.4 are 0.265 m and 0.0205 rad, respectively, which is larger than those of the bridge deck with adhesion coefficients of 1.0 and 0.6. Because the coupling effect of aerodynamic and vehicle motion is not considered in the one-way coupling, the one-way and two-way coupling simulation results differ significantly. The results indicate that it is necessary to use a two-way coupling method to study the aerodynamic stability of vehicles passing through a bridge tower at a high speed under crosswind conditions.

Crosswind degrades the aerodynamic behaviour of trains, especially during train acceleration, and an understanding of the flow field and train safety details requires more research attention. In the present study, the improved delayed detached eddy simulation (IDDES) method is applied to investigate the aerodynamic behaviour when a high-speed train accelerates under crosswind conditions. The spatial–temporal evolution of eddies and pressure distributions on the train surface based on eight discrete moments are explored. Moreover, the effects of three acceleration values on the aerodynamic force/moment coefficients and safety indicators are evaluated. The results show that the distance between the eddy shedding from the head car and the train body becomes smaller and the negative pressure of the eddy core increases in the process of acceleration. The pressure on the windward side of the train is stable, while the pressure on the leeward side shows an increasing trend with increasing train speed. An increase in the acceleration value increases the maximum side force and rolling moment coefficients, most prominently for the head car. In addition, a larger acceleration value may cause stronger pulsation of the train. Although the acceleration values do not increase the maximum values of the safety indicators, they have a slight effect on the local maximum values.

INTRODUCTION: STAR-CCM+ is a CFD software that uses continuum mechanics numerical techniques and is a tool for thermodynamic and fluid dynamics analysis. STAR-CCM+has expanded the functions of surface treatment, such as surface wrapper, surface remesh, and volume mesh generation.With the increase of train speed, the aerodynamic phenomena become more prominent, and the aerodynamic phenomena of high-speed trains in crosswind environment become more complicated. OBJECTIVES: Bogie is an important part of high-speed train. It is of great significance to study the aerodynamic performance Three groups of trains operating in a strong wind environment are modeled, and the surface pressure distribution characteristics of the car body and bogie, as well as the aerodynamic and aerodynamic torque distribution characteristics of each car and bogie, are analyzed when the train operates at 350km/h under a Class 12 crosswind condition. RESULTS: The results of the study show the variation rules of surface pressure, aerodynamic force and aerodynamic moment of the car body and bogie with wind speed. CONCLUSION: The windward surface pressure of the vehicle body increases linearly with the increase of wind speed, and the surface pressure of the roof and leeward side decreases linearly with the increase of wind speed.

During the on-track acoustic detection process, a potential flow model and an acoustic finite element mathematical model based on synthetic wind are utilized, taking into account the combined effects of vehicle speed, wind direction angle, and crosswind speed. Simulation and modeling are achieved using Automatic Matching of Acoustic Radiation Boundary Conditions (AML) technology, enabling obtaining a distribution map and sound pressure frequency response curve of the trackside acoustic field under crosswind conditions by setting up field point grids. It is found that sound pressure values at the same location gradually increase as the vehicle speed increases in the frequency range of 10 Hz to 70 Hz, at different vehicle speeds. The sound pressure values and distribution area of the trackside acoustic field are the largest when the crosswind speed is 10 m/s (wind force at level five), allowing for easier location of the sound source when a fault occurs. The study also reveals that under different wind direction angles, the same location's sound pressure value on the trackside gradually decreases as the wind direction angle increases, to lower than that of the non-crosswind condition, severely hindering the reception and diagnosis of acoustic signals. [ABSTRACT FROM AUTHOR]

In this paper, the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) was coupled with the Discrete Phase Model (DPM) to study snow accretion on the bogies of a high-speed train under crosswind conditions. The influence of bogie fairing configurations on the snow particles' movement, accumulation and flow characteristics around bogie regions are assessed. The results show that the larger bogie fairings have a positive effect on snow reduction around the main components of bogies under crosswind conditions. Compared to currently used bogie fairings, the total snow accretion of a head car increases by 41.5% by removing the fairings, while it decreases by 24.9% with the installation of full bogie fairings. The larger bogie fairings can lower the velocity of underbody flow and prevent high-speed airflows from entering the bogie regions from the windward side of bogie cavities. Moreover, the larger bogie fairings reduce the snow concentration around the heat-producing components of the bogies and attenuate the amount of snow particles near the rear plates of the cavities. Thus, the larger fairings can provide better anti-snow performance of train bogies under crosswind conditions. [ABSTRACT FROM AUTHOR]

Trains tend to be faster and lighter to meet the increasing public travel needs and interact with crosswind to produce a strong aerodynamic interaction, leaving a safety hazard for the operation. This paper presents a study into the dynamic response and running safety of the train–bridge system accounting for this aerodynamic interaction. The threedimensional flow features of a moving train in crosswinds are first investigated by a computational fluid dynamics method, and then an aerodynamic model for simulating unsteady crosswind force is developed. Furthermore, the dynamic responses of the train and bridge are calculated by using a wind–train–bridge dynamic interaction equation, and finally, the characteristic wind curve and surface are defined to evaluate the train's running safety. The results show that the lateral response of the train–bridge system significantly increases as the crosswind increases, and the head car can experience a high derailment risk and determine the running safety of the train due to the aerodynamic coupling effect of a moving train and crosswind. Variations in the wind direction need to be factored into the safety assessment for low train speeds, and the train is at greater danger when the crosswind appears perpendicular to the car body. [ABSTRACT FROM AUTHOR]

A theoretical model was developed to predict the diffusion process of hydrogen clouds in a crosswind field with an atmospheric inversion layer in this work to evaluate the safety of liquid hydrogen spills. The theoretical model was verified by the experimental results carried out by NASA. The results show that the maximum deviation of diffusion cloud centerline heights of the theoretical model and experiments is 8.92%. The mechanism of the inversion layer suppressing cloud rise is revealed from the theoretical model, atmospheric temperature gradient is closely related to the air density gradient. Compared to the case without atmospheric inversion layer, the cloud height decreases by 2.60%, 5.22%, and 8.70% and the cloud concentration increases by 6.20%, 12.78%, and 22.30% for the temperature gradient of 0.03, 0.06 and 0.10 K/m, respectively. The velocity of crosswind is 1.7 m/s, 2.7 m/s, 3.6 m/s, and 6.0 m/s in the temperature gradient of 0.10 K/m inversion layer environment, the height of the cloud is 34.77 m, 24.05 m, 16.83 m, and 11.16 m, and the hydrogen concentrations of the cloud centerline are 10.22%, 13.67%, 17.54%, and 28.92%, respectively. Therefore, it is significant to consider the crosswind field and atmospheric inversion layer for liquid hydrogen diffusion. • A theoretical model was developed to predict hydrogen clouds in atmospheric inversion layer. • The model considers the combined effects of crosswind field and temperature stratification. • The mechanism of inhibiting the rise of hydrogen clouds at the atmospheric inversion layer. • Increasing of temperature gradient inhibit the hydrogen cloud rise and increase concentration. [ABSTRACT FROM AUTHOR]

In order to overcome the time-consuming computational drawback of using computational fluid dynamics (CFD) for the numerical simulation of aircraft wake vortex evolution under different crosswind velocities, this paper proposes a wake vortex prediction model based on a convolutional neural network (CNN) algorithm. The study focuses on the B737-800 aircraft, and employs CFD numerical simulations to obtain the evolutionary characteristics of wake vortex parameters under crosswind velocities ranging from 0 to 7 m/s. The wake vortex velocity and Q-criterion vorticity values are collected and partitioned into mutually exclusive training and testing datasets. A CNN model is constructed, and the training dataset is used to tune hyperparameters to minimize loss and achieve accurate predictions. After saving the trained model, the desired crosswind velocity value is input to obtain the predicted wake vortex velocity and Q-criterion vorticity values. The results indicate that the convolutional neural network model exhibits an average absolute percentage error of 1.5%, which is 2.3% lower than that of the fully connected neural network model. This suggests that convolutional neural networks can enhance the accuracy of wake vortex predictions, as demonstrated in this study. Compared to traditional CFD methods, the proposed model reduces the computation time by approximately 40 times, effectively improving computational efficiency and offering valuable insight for studies involving numerous numerical simulations, such as analyzing the safety separation between aircraft wake vortices during paired approach procedures. [ABSTRACT FROM AUTHOR]