EFFECTS OF INCOMING FLOW ASYMMETRY ON SHOCK TRAIN STRUCTURES IN CONSTANT-AREA ISOLATORS

To simulate the actual flowfield at the exit of the supersonic/hypersonic inlet, a wind tunnel is designed to study the flow in the scramjet isolator under the asymmetric incoming flow. And compression fields in the isolator are investigated using wall static and pitot pressure measurements. Three incoming Mach numbers are considered as 1.5, 1.8 and 2. Results show that the increase of the asymmetry of the flow at the isolator entrance leads to the increase of the shock train length in the isolator for a given pressure ratio. Based on the analysis of the flow asymmetry effect at the isolator entrance on the shock train length, a modified correlation is proposed to calculate the length of the shock train. Predicted results of the proposed correlation are in good agreement with the experimental data.

Blood flow restriction training improves the efficacy of routine intervention in patients with chronic ankle instability

As a new means of rehabilitation,blood flow restriction training(BFRT)is widely used in the field of musculoskeletal rehabilitation.To observe whether BFRT can improve the efficacy of routine rehabilitation intervention in patients with chronic ankle instability(CAI).Twenty-three patients with CAI were randomly divided into a routine rehabilitation group(RR Group)and a routine rehabilitationþblood flow restriction training group(RRþBFRT Group)according to the Cumberland Ankle Instability Tool(CAIT)score.The RR Group was treated with routine rehabilitation means for intervention,and the RRþBFRT Group was treated with a tourniquet to restrict lower limb blood flow for rehabilitation training based on routine training.Before and after the intervention,the CAIT score on the affected side,standing time on one leg with eyes closed,comprehensive scores of the Y-balance test,and surface electromyography data of tibialis anterior(TA)and peroneus longus(PL)were collected to evaluate the recovery of the subjects.Patients were followed up 1 year after the intervention.After 4 weeks of intervention,the RRþBFRT Group CAIT score was significantly higher than the RR Group(19.33 VS 16.73,p<0.05),the time of standing on one leg with eyes closed and the comprehensive score of Y-balance were improved,but there was no statistical difference between groups(p>0.05).RRþBFRT Group increased the muscle activation of the TA with maximum exertion of the ankle dorsal extensor(p<0.05)and had no significant change in the muscle activation of the PL with maximum exertion of the ankle valgus(p>0.05).There was no significant difference in the incidence of resprains within 1 year between the groups(36.36%VS 16.67%,p>0.05).The incidence of ankle pain in the RRþBFRT Group was lower than that in the RR Group(63.64%VS 9.09%,p<0.01).Therefore,four-weeks BFRT improves the effect of the routine intervention,and BFRT-related interventions are recommended for CAI patients with severe ankle muscle mass impairment or severe pain.

Flow structure around high-speed train in open air

According to the analysis of the turbulent intensity level around the high-speed train, the maximum turbulent intensity ranges from 0.2 to 0.5 which belongs to high turbulent flow. The flow field distribution law was studied and eight types of flow regions were proposed. They are high pressure with air stagnant region, pressure decreasing with air accelerating region, low pressure with high air flow velocity region I, turbulent region, steady flow region, low pressure with high air flow velocity region II,pressure increasing with air decelerating region and wake region. The analysis of the vortex structure around the train shows that the vortex is mainly induced by structures with complex mutation and large curvature change. The head and rear of train, the underbody structure, the carriage connection section and the wake region are the main vortex generating sources while the train body with even cross-section has rare vortexes. The wake structure development law studied lays foundation for the train drag reduction.

Properties of train traffic flow in a moving block system

The development direction of railways is toward the improvement of capacity and service quality, where the service quality includes safety, schedule, high speed, and comfort. In light of the existing cellular automaton models, in this paper, we develop a model to analyze the mixed running processes of trains with maximal speeds of 500 km/h and 350 km/h respectively in the moving block system. In the proposed model, we establish some sound rules to control the running processes of a train, where the rules include the departure rules in the intermediate stations, the overtaking rules, and the conditions of speed limitation for a train stopping at a station or passing through a station. With the consideration of the mixed ratio and the distance between two adjacent stations, the properties of the train traffic flow （including capacity and average speed） are simulated. The numerical results show that the interactions among different trains will affect the capacity, and a proper increase of the spatial distance between two adjacent stations can enhance the capacity and the average speed under the moving block.

Scheduling of high-speed rail traffic based on discrete-time movement model

In this paper, a new simulation approach for solving the mixed train scheduling problem on the high-speed double-track rail line is presented. Based on the discrete-time movement model, we propose control strategies for mixed train movement with different speeds on a high-speed double-track rail line, including braking strategy, priority rule, travelling strategy, and departing rule. A new detailed algorithm is also presented based on the proposed control strategies for mixed train movement. Moreover, we analyze the dynamic properties of rail traffic flow on a high-speed rail line. Using our proposed method, we can effectively simulate the mixed train schedule on a rail line. The numerical results demonstrate that an appropriate decrease of the departure interval can enhance the capacity, and a suitable increase of the distance between two adjacent stations can enhance the average speed. Meanwhile, the capacity and the average speed will be increased by appropriately enhancing the ratio of faster train number to slower train number from 1.

An Improved Discrete-Time Model for Heterogeneous High-Speed Train Traffic Flow

This paper aims to present a simulation model for heterogeneous high-speed train traffic flow based on an improved discrete-time model（IDTM）.In the proposed simulation model,four train control strategies,including departing strategy,traveling strategy,braking strategy,overtaking strategy,are well defined to optimize train movements.Based on the proposed simulation model,some characteristics of train traffic flow are investigated.Numerical results indicate that the departure time intervals,the station dwell time,the section length,and the ratio of fast trains have different influence on traffic capacity and train average velocity.The results can provide some theoretical support for the strategy making of railway departments.