Effect of bogie fairings on the snow reduction of a high-speed train bogie under crosswinds using a discrete phase method

Gao, Guangjun,Zhang, Yani,Zhang, Jie,Xie, Fei,Zhang, Yan,Wang, Jiabin Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.27 No.4

This paper investigated the wind-snow flow around the bogie region of a high-speed train under crosswinds using a coupled numerical method of the unsteady Realizable $k-{\varepsilon}$ turbulence model and discrete phase model (DPM). The flow features around the bogie region were discussed and the influence of bogie fairing height on the snow accumulation on the bogie was also analyzed. Here the high-speed train was running at a speed of 200 km/h in a natural environment with the crosswind speed of 15 m/s. The mesh resolution and methodology for CFD analysis were validated against wind tunnel experiments. The results show that large negative pressure occurs locally on the bottom of wheels, electric motors, gear covers, while the positive pressure occurs locally on those windward surfaces. The airflow travels through the complex bogie and flows towards the rear bogie plate, causing a backflow in the upper space of the bogie region. The snow particles mainly accumulate on the wheels, electric motors, windward sides of gear covers, side fairings and back plate of the bogie. Longer side fairings increase the snow accumulation on the bogie, especially on the back plate, side fairings and brake clamps. However, the fairing height shows little impact on snow accumulation on the upper region of the bogie. Compared to short side fairings, a full length side fairing model contributes to more than two times of snow accumulation on the brake clamps, and more than 20% on the whole bogie.

Optimization of the anti-snow performance of a high-speed train based on passive flow control

Guangjun Gao,Zhen Tian,Jiabin Wang,Yan Zhang,Xinchao Su,Jie Zhang 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.30 No.4

In this paper, the improvement of the anti-snow performance of a high-speed train (HST) is studied using the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) coupled with the Discrete Phase Model (DPM). The influences of the proposed flow control scheme on the velocity distribution of the airflow and snow particles, snow concentration level and accumulated mass in the bogie cavities are analyzed. The results show that the front anti-snow structures can effectively deflect downward the airflow and snow particles at the entrance of the cavities and alleviate the strong impact on the bogie bottom, thereby decrease the local accumulated snow. The rotational rear plates with the deflecting angle of 45° are found to present well deflecting effect on the particles’ trajectories and force more snow to flow out of the cavities, and thus significantly reduce the accretion distribution on the bogie top. Furthermore, running speeds of HST are shown to have a great effect on the snow-resistance capability of the flow control scheme. The proposed flow control scheme achieves more snow reduction for HST at higher train’s running speed in the cold regions.

Effect of bogie fairings on the snow reduction of a high-speed train bogie under crosswinds using a discrete phase method

Guangjun Gao,Yani Zhang,Jie Zhang,Fei Xie,Yan Zhang,Jiabin Wang 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.4

This paper investigated the wind-snow flow around the bogie region of a high-speed train under crosswinds using a coupled numerical method of the unsteady Realizable k-ε turbulence model and discrete phase model (DPM). The flow features around the bogie region were discussed and the influence of bogie fairing height on the snow accumulation on the bogie was also analyzed. Here the high-speed train was running at a speed of 200 km/h in a natural environment with the crosswind speed of 15 m/s. The mesh resolution and methodology for CFD analysis were validated against wind tunnel experiments. The results show that large negative pressure occurs locally on the bottom of wheels, electric motors, gear covers, while the positive pressure occurs locally on those windward surfaces. The airflow travels through the complex bogie and flows towards the rear bogie plate, causing a backflow in the upper space of the bogie region. The snow particles mainly accumulate on the wheels, electric motors, windward sides of gear covers, side fairings and back plate of the bogie. Longer side fairings increase the snow accumulation on the bogie, especially on the back plate, side fairings and brake clamps. However, the fairing height shows little impact on snow accumulation on the upper region of the bogie. Compared to short side fairings, a full length side fairing model contributes to more than two times of snow accumulation on the brake clamps, and more than 20% on the whole bogie.

Effect on measurements of anemometers due to a passing high-speed train

Jie Zhang,Guangjun Gao,Sha Huang,Tanghong Liu 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.4

The three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equationsand k-ε double equations turbulent model were used to investigate the effect on the measurements ofanemometers due to a passing high-speed train. Sliding mesh technology in Fluent was utilized to treat themoving boundary problem. The high-speed train considered in this paper was with bogies and inter-carriagegaps. Combined with the results of the wind tunnel test in a published paper, the accuracy of the presentnumerical method was validated to be used for further study. In addition, the difference of slipstreambetween three-car and eight-car grouping models was analyzed, and a series of numerical simulations werecarried out to study the influences of the anemometer heights, the train speeds, the crosswind speeds and thedirections of the induced slipstream on the measurements of the anemometers. The results show that theinfluence factors of the train-induced slipstream are the passing head car and tail car. Using the three-cargrouping model to analyze the train-induced flow is reasonable. The maxima of horizontal slipstreamvelocity tend to reduce as the height of the anemometer increases. With the train speed increasing, therelationship between Vtrain and Vinduced slipstream can be expressed with linear increment. In the absence ofnatural wind conditions, from the head car arriving to the tail car leaving, the induced wind directionchanges about 330°, while under the crosswind condition the wind direction fluctuates around -90°. With thecrosswind speed increasing, the peaks of VX, |VXY -Vwind| of the head car and that of VX of the tail car tend toenlarge. Thus, when anemometers are installed along high-speed railways, it is important to study the effecton the measurements of anemometers due to the train-induced slipstream.

Effect on measurements of anemometers due to a passing high-speed train

Zhang, Jie,Gao, Guangjun,Huang, Sha,Liu, Tanghong Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.4

The three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equations and k-${\varepsilon}$ double equations turbulent model were used to investigate the effect on the measurements of anemometers due to a passing high-speed train. Sliding mesh technology in Fluent was utilized to treat the moving boundary problem. The high-speed train considered in this paper was with bogies and inter-carriage gaps. Combined with the results of the wind tunnel test in a published paper, the accuracy of the present numerical method was validated to be used for further study. In addition, the difference of slipstream between three-car and eight-car grouping models was analyzed, and a series of numerical simulations were carried out to study the influences of the anemometer heights, the train speeds, the crosswind speeds and the directions of the induced slipstream on the measurements of the anemometers. The results show that the influence factors of the train-induced slipstream are the passing head car and tail car. Using the three-car grouping model to analyze the train-induced flow is reasonable. The maxima of horizontal slipstream velocity tend to reduce as the height of the anemometer increases. With the train speed increasing, the relationship between $V_{train}$ and $V_{induced\;slipstream}$ can be expressed with linear increment. In the absence of natural wind conditions, from the head car arriving to the tail car leaving, the induced wind direction changes about $330^{\circ}$, while under the crosswind condition the wind direction fluctuates around $-90^{\circ}$. With the crosswind speed increasing, the peaks of $V_X,{\mid}V_{XY}-V_{wind}{\mid}$ of the head car and that of $V_X$ of the tail car tend to enlarge. Thus, when anemometers are installed along high-speed railways, it is important to study the effect on the measurements of anemometers due to the train-induced slipstream.

State estimation of a heavy-duty hexapod robot with passive compliant ankles based on the leg kinematics and IMU data fusion

Yufei Liu,Haibo Gao,Liang Ding,Guangjun Liu,Zongquan Deng,Nan Li 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8

To control autonomous walking of a legged robot, it is essential to obtain the instantaneous velocity and posture of the robot. This paper presents a full body state estimation algorithm for a hexapod robot to estimate the velocity and posture of the trunk body without geometric knowledge of the environment. The velocity and posture estimates of the hexapod robot with passive compliant ankles are further processed by a data fusion method that is proposed based on the extended Kalman filter (EKF) technique, utilizing the leg kinematics model of the robot and the readouts from an on–board inertial measurement unit (IMU). The absolute footholds of the hexapod robot are estimated together with the velocity and posture of the trunk body, with consideration of intermittent ground contacts. Experiments have been conducted on both flat and uneven terrains, and the results have confirmed the effectiveness of the proposed approach.