A Graph-Based Optimal On-Ramp Merging of Connected Vehicles on the Highway

Connected and automated vehicles (CAVs) are a very promising alternative for reducing fuel consumption and improving traffic efficiency when vehicles merge at on-ramps. In this study, we propose a graph-based method to coordinate CAVs to merge at the highway ramp. First, the optimized vehicles were divided into groups to pass the merging point. Then we built a directed graph model for each group of vehicles, where each path of the graph corresponds to one of all possible merging sequences. The improved shortest path algorithm is proposed to find the optimal merging sequence for minimizing total fuel consumption. The results of the simulation showed that the proposed graph-based method reduced fuel consumption and ensured high traffic efficiency; moreover, the vehicles can form a platoon after passing the merge point.

Experimental Study on Multi-Channel Jets in Plate Assembly Under Blockage Condition

In the nuclear field, the reactor using plate fuel assembly forms multiple jets at exit. So, it’s meaningful to study multiple jets to learn the behavior of the coolant when it leaves the core. This paper uses PIV technology to study the flow characteristics of 9 jets at low Reynolds number. Firstly, the velocity field reveals that the pressure outside the jet is greater than the inside of the jet, which causes the jet to deflect and converge inward at z/w = 0–8. Then, the velocity field with different Re number is analyzed in the center plane, and find that the flow distribution is similar. Then, a detailed analysis is performed on the jet under specific conditions, and the merge point is discussed in the paper. At the same time, the first-order velocity tensor are also calculated in this paper. In addition, this article also analyzes the jet flow field after the central narrow channel was blocked. In this experiment, a plug was used to block the No. 5 jet by 1/3. And the flow redistribution is discussed in this case. The methods of flow calculation using PIV technology is established and compared with the real number of flowmeters, it’s found that the calculation method is rather accurate. On the other hand, the experiment find that the distribution of flow in each channel is not uniform, and the blocking condition make an increase in the flow of edge channels, which leads to the decreasing of flow in the blocked adjacent channel.

Analysis of the Driver’s Behavior Characteristics in Low Volume Freeway Interchange

Drivers’ behavior characteristics cannot be ignored in designing freeway interchange facilities in order to improve traffic safety. This paper conducted a field experiment in Qingyin expressway. Four freeway interchanges from K571+538 to K614+932 with relatively low volume were selected, and 12 qualified drivers, 6 car test drivers and 6 truck test drivers, were driving vehicles according to the driving program. GPS and eye-tracking instrument were employed to record running speed, real-time, running track, fixation point, and so forth. Box-plot graphs and Student’st-test were used to analyze the 12 data sets of driver’s fixation on exit guide signs. Speed-distance curves of effective 11 data sets were plotted to examine the test drivers’ behavior in diverging area and merging area. The results indicated that (1) drivers recognize the exit direction signs in 170 m–180 m advanced distance; (2) the diverging influence area is 1000 m upstream of the diverge point, and the merging influence area is 350 m downstream of the merge point; (3) NO OVERTAKING sign is recommended to be placed at 350 m upstream of the diverge point. The results can provide guidance for the design of freeway interchange facilities and management in order to improve traffic safety.

Study of a Turbulent Dual Jet Consisting of a Wall Jet and an Offset Jet

The study of a two-dimensional, steady, incompressible, turbulent flow of a dual jet consisting of a wall jet and an offset jet has been simulated numerically. The standard high Reynolds number two-equation k-ɛ model is used as the turbulence model. The Reynolds number is considered as 20000 for all the computations because the flow becomes fully turbulent. The merge point and the combined point have been obtained and compared with other results. The central streamline has been plotted and observed to follow an arc of a circle. The momentum flux has been computed along the axial length for the wall jet, offset jet and the dual jet and compared. A similarity profile has been obtained in the downstream direction. A detailed discussion has been provided on the pressure field, Reynolds stress, kinetic energy and its dissipation rate. The jet growth rate in terms of half-width, the decay of maximum velocity and the jet width are presented

Momentum Flux in Plane, Parallel Jets

The evolution of the streamwise momentum flux for two turbulent, plane, parallel jets discharging through slots in a direction normal to a wall was studied both numerically and experimentally. The numerical results, obtained by solving the Reynolds-averaged Navier-Stokes equations employing a standard k−ε turbulence model, predicted to within experimental error measured integrals of the momentum flux downstream of the merge point for jet spacing S/d=5. Integration of the streamwise component of the Reynolds-averaged Navier-Stokes equations over a control volume results in an integral constant that was evaluated numerically for jet spacings S/d=3, 5, 7, 9, and 11, and for different levels of turbulence kinetic energy and dissipation rate at the jet inlet boundaries. Results revealed that the integral constant is decreased as the jet spacing increases, and is also decreased as jet entrainment rates are increased due to higher levels of inlet turbulence kinetic energy, or alternatively, decreased levels of dissipation rate. Streamwise distance to the merge point was also found to decrease for increased levels of turbulence kinetic energy or decreased levels of dissipation rate at the jet inlet.

A Numerical Study of Buoyant Plane Parallel Jets

A numerical study was performed to assess the influence of buoyancy on plane, parallel jets. Results indicate that, relative to isothermal jets, the location along the vertical symmetry plane at which the two jets merge (the merge point) decreases with increasing jet inlet temperature. This decrease is attributed to higher entrainment rates for the heated jet relative to the isothermal jet. It was also found that for sufficiently high values of the Archimedes number, the merge point becomes nearly independent of the initial jet spacing.