This paper proposes and validates the application of the two-dimensional Social Force Model to simulate the lane-disciplined vehicular flow on road. In detail, a lane-wise lane-keeping force field is established along the lateral direction of the road. This force, with a magnitude quadratic to the lateral displacement of vehicle to the lane centerline, confines the lateral movement of vehicle to form a laned pattern on road. To realize the overtaking maneuvers and to avoid collisions, the distance-dependent overtaking force and repulsive forces are also defined in the model. The parameters in the proposed model are calibrated by comparing with the fundamental diagram collected in the literature (GA400 dataset). The comparison shows that the proposed model could provide good prediction in terms of average speed and speed range up to 80 veh/km/lane. However, for very high-density flow, the model is likely to overpredict the flow speed which is possibly due to a fixed target speed in the model. After the validation step, the model is employed to simulate traffic flows on a segment of 4-lane freeway in Nanjing, China (data collected by Southeast University). The comparison of the simulated and measured trajectories demonstrates that, except very abnormal behaviors, the proposed model could predict most car-following and lane-changing behaviors based on relative velocity and inter-vehicle gaps on a microscopic level.

This paper investigates the influence of the fuselage arm cross-section shape on the aerodynamic and aeroacoustic performance of quadcopter Unmanned Aerial Vehicles in hover state by numerical simulation. The unsteady simulations of the flow field around one generic two-blade rotor and one fuselage arm are conducted by the Reynolds Averaged Navier-Stokes solver with the [ ] SST turbulence model. The total thrust forces and the sound pressure level spectra of five fuselage arm cross-section shapes with the same cross-section area are simulated and compared. Results show that the fuselage arm with a square cross-section has the highest aerodynamic performances for all the tested speeds of rotation. The fuselage arm with a circular cross-section ranks second in aerodynamic performance. However, it has the best aeroacoustic performance. The other three tested cross-section shapes show less thrust forces and higher sound pressure levels at the blade passing frequencies than the circular cross-section, which are not optimal neither aerodynamically nor aeroacoustically.

As urban buildings become increasingly dense, indoor personnel are often exposed to noise disturbances from adjoining rooms which can reduce working efficiency and affect mental health. Closing the door is one of the ways to reduce noise transmission, but it can cause a decrease in indoor air circulation. This paper investigates the sound insulation effect and air ventilation performance of a door in a partially open state by numerical simulation. To acquire the effect of sound insulation, an acoustic–structural solver is employed to calculate the sound transmission losses with different door opening angles in the frequency domain. To evaluate the ventilation performance, the mass flow rates across door opening are calculated by computational fluid dynamics. The simulation results confirm the trade-off relation between the sound insulation effect and the ventilation performance. To calculate the effect of noise and ventilation on work efficiency, a comprehensive evaluation index workplace environmental score (WES) was introduced and calculated by the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method. A clear sound insulation effect corresponds to an opening angle (θ_d) of less than 15° with minimum air ventilation. Good ventilation performance could be obtained when the door opening angle is larger than 45°, while the sound insulation effect is negligible. A good compromise between the sound insulation effect and the air ventilation performance is found to be in the range of θ_d = 15°~25°, which provides practical recommendations in daily routines.

This study proposes a model for simulating the dynamics of electric bicycle flow in isolated non-motorized lanes. The model is an extension of the conventional social force model with an additional rotational degree of freedom that describes the steering angle of electric bicycles. In this model, two corrective relaxation terms are included in the driving force for the rotational degree of freedom: one on the steering angle and another on the angular velocity. Stability analysis shows that an appropriate amount of correction on the angular velocity helps to avoid oscillation and overshoots of the turning angle. The proposed model is validated both macroscopically and microscopically, and the agreement of the simulated fundamental diagram with that in the literature demonstrates the rationality of the model in characterizing the collective motions of electric bicycles. Comparison of simulated and observed trajectories confirms that the proposed model could reproduce electric bicycle motions with a certain accuracy at the microscopic level. Finally, predictions based on the validated model are provided. According to the simulation results, congestion starts to occur when the inlet flow rate of the lane reaches 1500–1750 ebike/h/m. For a mixed configuration, the maximum allowed flow rate in the lane is 2350–2400 ebike/h/m, and this value depends on the proportion of fast electric bicycles and the riding style in the flow.

The acoustic concentration of submicron particles in a micro-channel is investigated numerically via a gas-particle multiphase coupling scheme. For modeling the gas flow under transverse standing wave, 2 dimensional linearized Euler equations with the parabolic mean flow are employed with the high order finite difference method. Through the analogous behavior of rarefied gas and air-suspended particles, a modified Unified Gas-Kinetic Scheme (UGKS) is adopted to estimate the particle dynamics. In detail, Stokes' drag force and acoustic radiation force applied on particles are accounted for by introducing a velocity-dependent kinetic acceleration term in the UGKS. To validate this modeling, numerical simulations are tested with varying standing wave amplitudes. The effects of acoustic radiation force to drag force ratio and mean flow velocity are also analyzed. The computed concentration patterns and efficiencies are compared with experimental results from the literature. The agreement shows that the adopted Euler-UGKS coupling scheme could be an effective tool for micro-sized particle acoustic concentration applications.

This paper optimizes the aerodynamic performance of quadcopter UAVs by varying the cross-section shape of the fuselage arm. In detail, a testing stand is set up to measure simultaneously the lift force as well as the input electric power. The tested quadcopter UAV has replaceable fuselage arms, allowing convenient testing for different arm cross-sections fabricated by 3D printing. The optimization process starts from a comparison between two basic cross-section shapes: circular arm and square arm. Results show that the square arm has an overall lift-to-power ratio 2.41% higher than the circular arm with the same weight. Then, by inclining and setting up curves on the side surfaces of a square arm, the optimized rhombus + 15°+arc2 arm is proposed to have an overall 3.68% increment in lift-to-power ratio and 5.77% increment in Figure of Merit (FM) as compared to the circular arm.