Uphill Section Research Articles

Experimental evaluation of solitary slugs in a horizontal pipe

In this work the existence of a bi-stable flow regime in a horizontal gas-liquid two-phase flow was experimentally confirmed. In this regime, both stratified and slug flows were found to be stable, and the occurrence of either regime depended on the inlet conditions imposed on the flow. When operating in the bi-stable flow condition, two types of slugs can occur. The first type was obtained by forcing a regular slug flow at the inlet of the horizontal pipe using an uphill section before the inlet. In this case, slugs in the uphill and horizontal sections have similar frequencies. The second type was obtained by forcing a stratified flow at the inlet, and then introducing a short pulse in the liquid flow rate. This triggered a solitary slug in the pipe, which grew linearly with the distance from the inlet. The behavior of the solitary slugs observed experimentally confirms the explanation and the model provided by Belt et al., 2024. The existence of such slugs can represent a threat in operations, since in long flowlines they can become extremely large and flood the downstream process installations. For instance, the experiments showed solitary slugs more than 200 pipe diameters long at a distance of 460 pipe diameters from the inlet. In order to evaluate the conditions under which the solitary slug phenomenon might occur, the extent of the bi-stable flow regime was experimentally determined. Its lower and upper boundaries match reasonably well with the stability conditions for slug flow and stratified flow, respectively, which were calculated within a 1D modeling framework.

A Performance Evaluation Method for Long and Steep Uphill Sections of Heavy-Haul Railway Lines

Any system for evaluating the safety service performance of heavy-haul railway lines must effectively reflect the real-time service status of the line. The working conditions of heavy-load lines are complex and diverse, particularly on uphill sections. Existing evaluation systems struggle to accurately reflect the service conditions of long and steep uphill sections bearing heavy loads, posing a significant threat to the safe operation of these lines. To address this problem, we propose a new method for evaluating the safety service performance of long and steep uphill sections of heavy-haul railway lines by establishing a scoring system based on the Analytic Hierarchy Process (AHP). First, damage indicators for heavy-haul lines are categorized into three groups: track geometry status indicators, track structure status indicators, and track traffic status indicators. Using data from existing heavy-haul lines and maintenance experiences, we determine a score deduction standard, classifying lines into four levels based on their safety service quality. Next, we establish a coefficient table for the service performance of long and steep uphill sections after the corresponding scores are deducted. Using data for the length and elevation grade of the actual uphill section, we adjust the deducted scores of the track structure status indicators, enhancing the evaluation system’s accuracy in describing the working conditions. Finally, we verify the stability of the entire system by conducting a sensitivity analysis of the indicator evaluation results using the One-At-a-Time (OAT) method. This method fills a critical gap in the safe operation and maintenance of heavy-haul railways and provides a safety guarantee for the operation of long uphill sections of heavy-haul railways.

Analysis of drivers’ mental workload in V-shaped undersea tunnels based on heart rate variability

To explore the effects of illumination and tunnel longitudinal slope on driving safety in V-shaped undersea tunnels, we conducted a study to analyze changes in drivers’ mental workload caused by Illumination and longitudinal slope variations within the tunnel through field data. The typical V-shaped undersea tunnel crossing Jiaozhou Bay in Qingdao, China, was selected. Thirty drivers were recruited to participate in the driving tests during off-peak hours and 120 sets of electrocardiographic (ECG) signals were collected from drivers under natural driving conditions. The standard deviation of the Normal-to-Normal intervals (SDNN) was used and an outlier test was performed using the box plot. The drivers’ SDNN was used to index drivers’ mental workload under different Illumination and longitudinal slope conditions in the V-shaped undersea tunnel. A model was established to quantify the relationships of illumination and longitudinal slope with the SDNN. The results showed a significant negative correlation between the illumination change rate and the SDNN, i.e., the greater the change rate of illumination was, the smaller the SDNN was (and the greater the mental workload was). While the mental workload of drivers varied on tunnel longitudinal slope compared with illumination. With increased steepness of longitudinal slopes, the driver’s SDNN value decreased, but the SDNN of drivers in the downhill section were smaller than SDNN in the uphill section, reflecting a greater mental workload. Finally, a proposed value interval for the combined design of illumination and slope in undersea tunnels is given in the context of drivers’ mental workload variations.

Stability and safety analysis of mixed traffic flow considering network function degradation and platoon driving on the road with a slope

Considering the influence of slope sections and random degradation of the communication function of cooperative adaptive cruise control vehicles and the effect of the cooperative adaptive cruise control vehicle group driving, a linear stability criterion for heterogeneous traffic flow composed of cooperative adaptive cruise control vehicles and humanly-driven vehicles on slopes is derived, and a parameter sensitivity analysis is carried out. On this foundation, the safety of traffic flow on two-lane roads up and down hills is simulated while considering the lane-changing behavior of automobiles. The stability study shows increased cooperative adaptive cruise control vehicle penetration and uphill gradient will help improve traffic flow stability. In contrast, the increase in the downhill slope will intensify the transmission amplitude of the disturbance. When vehicle starting sensitivity is 2.5, and the gradient is 60, the minimum cooperative adaptive cruise control vehicle penetration required for mixed traffic flow to maintain stability on a downhill at any initial equilibrium speed is 85%, and the minimum penetration required on an uphill is 73%, and this proportion decreases with the increase in the uphill gradient and increases with the rise in the downhill slope. According to the safety study, increasing cooperative adaptive cruise control vehicle penetration and implementing lane-changing rules will improve traffic flow safety. Compared with the straight section, under the same conditions, the traffic flow safety of the uphill section is the best, and the safety of the downhill section is poor, which is consistent with the stability analysis results. This study is of great significance for future traffic control strategies for mountain roads.

Deformation analysis of underwater shield tunnelling based on HSS model parameter obtained by the Bayesian approach

Deformation analysis and control of underwater large-diameter shield tunnels is a prerequisite for safe tunnel construction. Reasonable selection of constitutive model and its parameters is the key to accurately predicting the deformation induced by underwater shield tunnelling. In this paper, the finite element analysis of cavity expansion during the piezocone penetration test (CPTU) based on the hardening soil model with small strain stiffness (HSS) model was carried out, and the correlation model of the normalized cone tip resistance Q with the reference secant modulus E50ref and the effective internal friction angle φ’ was established and verified using mini CPTU chamber test. Then, a Bayesian probability characterization approach for E50ref of silty clay based on CPTU was proposed. Furthermore, the deformation analysis of Jinan Yellow River tunnel crossing the south embankment was carried out to verify the reliability of the proposed approach. The good agreement between the field measurement and numerical simulation confirms that the parameters obtained by the Bayesian approach are reliable. Finally, a sensitivity analysis was performed to study the law of riverbed settlement induced by underwater large-diameter shield tunnelling. The results show that the increasing support pressure could effectively reduce the riverbed settlement, but there is an upper limit. The optimal support pressure of established model is between 0.45 MPa and 0.5 MPa. The uphill section causes greater riverbed settlement than the downhill section. Under the same condition, increasing buried depth and water level will lead to a more significant settlement.

Study on rail corrugation on curved tracks on metro ramps

A typical feature of rail corrugation on metro rails is the almost 100% probability that low rails on sharply curved tracks will suffer from corrugation, but both high and low rails on gently curved tracks are less prone to corrugation. On Chongqing Metro Line 10, there is a curved track on an ascending slope, and the high rail of this track suffered from severe corrugation. Shenzhen Metro Line 3 has a curved track on a descending slope, and the low rail of this track was also subjected to corrugation. This article presents a study on the rail corrugation formed on metro ramps. Two vehicle-track coupled dynamic models were employed to judge whether the creep force in the contact patch would be saturated, with results showing that the creep force of the leading wheel on the high rail on the uphill section tends to be saturated, affected by the tractive force. Influenced by the braking force, the creep force on the leading inner wheel on the downhill section is also prone to be saturated. In this study, the formation of corrugation is attributed to the self-excited oscillation generated at the wheel-rail (W-R) interface. Based on this mechanism, a finite element model for predicting the occurrence propensity of the low rail corrugation on the downhill track was developed. The simulation results show that increasing lateral fastener damping is beneficial for suppressing rail corrugation.

Research on the braking energy reuse management strategy of hybrid electric mining trucks based on motor load rate

The braking energy recovery and reuse technology are significant to the energy-saving and emission reduction of hybrid mining dump trucks. Therefore, this paper proposes a technical scheme to increase the speed of the heavy-load uphill section by using the light overload of the motor. By constructing the vehicle dynamics model of the mining dump truck and the electric drive system component efficiency and engine energy consumption model and taking the “feedback braking energy-saving coefficient” as the evaluation index, the electric motors of each slope section under the rule-based energy management strategy are obtained. Then, the dynamic programing algorithm is used to optimize the selection of the motor load rate on the slope section. The results show that: on the premise of ensuring the dynamic performance of the vehicle, maximizing the use of the braking energy can shorten the driving time by 57.8 s and reduce the engine energy consumption 18.63 kWh, accounting for 8.56% of the engine energy consumption of the entire heavy-load uphill section. This paper provides a theoretical reference for the energy-saving research on the efficient reuse of braking energy of mining dump trucks on slopes.

Modeling and Analysis of Car-Following for Intelligent Connected Vehicles Considering Expected Speed in Helical Ramps

In this paper, to explore the influence of expected speed on traffic flow in helical ramps, a new car-following model for intelligent connected vehicles (ICVs) was established for helical ramps, mainly considering the expected speed provided in the vehicle-to-everything (V2X) environment. On this basis, sufficient conditions to ensure the stability of the traffic stream were met and the congestion propagation mechanism was discussed by using a linear stability analysis and nonlinear stability analysis. The results showed that the ICVs can effectively increase the stability of the traffic flow by considering the expected speed of the helical ramps. When the feedback coefficients of the expected speed of the helical ramps were 0.3 and 0.5, the stability of the traffic flow changed significantly, especially in the uphill section; the feedback coefficient was 0.5 when the traffic flow was completely restored to the initial steady state even under the action of small disturbances. In a difficult field-driving test, this paper showed through a numerical simulation that broadcasting an expected speed to the ICVs in the helical ramps can effectively improve the stability of traffic flow, which provides a theoretical basis for future landing applications of ICVs in complex road scenarios.

Numerical optimization of pacing strategy in cross-country skiing based on Gauss pseudo-spectral method

In cross-country skiing competitions, the choice of pacing strategy is of decisive significance to athletes' performance. A reasonable pacing strategy is essential for athletes to improve their performance. In this paper, the mathematical models of cross-country skiing simulation and pacing optimization are established, including motion model, athlete power output model, and optimization model. The actual competition data of a Chinese athlete in Guyangshu 1.5 km track was compared with the model simulation results. The whole process time error is less than 3%, which verifies the accuracy of the motion and power output model. Gauss pseudo-spectral method is applied to the optimization model. By changing the distribution of athletes' power output, the racing time is minimized under the condition that the total energy output remains unchanged. Compared with the pacing strategy before optimization, the optimized racing time was shortened by 12.6 s, which verifies the effectiveness of the optimization model. Optimized results show that in the first significant uphill section, a recommendation is to use a more conservative strategy, while in the latter half of uphill sections the power output should be increased.

Pole Length Influences Performance During On-Snow Skating in Female Cross-Country Skiers

PurposeThe purpose of this study was to examine the effect of pole length on performance and technique selection during a simulated skating cross-country (XC) skiing competition on snow in female XC skiers.MethodsNine female XC skiers and biathletes (VO2max 63.6 ± 6.2 mL/min/kg, age 22.9 ± 3.5 years, body height 1.69 ± 0.1 m and body mass 60.8 ± 4.6 kg) completed two 5-km skating time-trail with maximal effort. The athletes had a minimum 4.5 h of rest between the two races, which were performed in a random order: one with self-selected poles (89.0% ± 0.6% of body height) and one with 7.5 cm increased pole length (94.0% ± 0.5% of body height). Speed in set terrain sections was determined and the selection of sub-technique was self-reported immediately after each race based on a detailed review of the entire track.ResultsSkiers performed on average 7.1 ± 7.1 s (P = 0.029) faster with the long poles, with this difference occurring during the first 200 m and in the uphill parts of the track, in which ~ 5% more G3 and ~ 5% fewer G2 sub-techniques were chosen (both P < 0.05). The rating of perceived exertion was 1 ± 0.9 point lower (P = 0.04) and skiing technique was perceived to be ~ 1.2 ± 1.5 points better with long poles (P = 0.038), while the physiological responses (i.e., peak and average heart rate, and blood lactate concentration) did not differ between trials.ConclusionIn conclusion, poles 7.5 cm longer than self-selected ones improved performance in skating, by enhancing speed in the initial phase (first 200 m) and in the uphill section of the track. In addition, the longer poles induced more use of the G3 skating sub-technique.

Impact of lateral groundwater flow on hydrothermal conditions of the active layer in a high-Arctic hillslope setting

Abstract. Modeling the physical state of permafrost landscapes is a crucial addition to field observations in order to understand the feedback mechanisms between permafrost and the atmosphere within a warming climate. A common hypothesis in permafrost modeling is that vertical heat conduction is most relevant to derive subsurface temperatures. While this approach is mostly applicable to flat landscapes with little topography, landscapes with more topography are subject to lateral flow processes as well. With our study, we contribute to the growing body of evidence that lateral surface and subsurface processes can have a significant impact on permafrost temperatures and active layer properties. We use a numerical model to simulate two idealized hillslopes (a steep and a medium case) with inclinations that can be found in Adventdalen, Svalbard, and compare them to a flat control case. We find that ground temperatures within the active layer uphill are generally warmer than downhill in both slopes (with a difference of up to ∼0.8 ∘C in the steep and ∼0.6 ∘C in the medium slope). Further, the slopes are found to be warmer in the uphill section and colder in the base of the slopes compared to the flat control case. As a result, maximum thaw depth increases by about 5 cm from the flat (0.98 m) to the medium (1.03 m) and the steep slope (1.03 m). Uphill warming on the slopes is explained by overall lower heat capacity, additional energy gain through infiltration, and lower evaporation rates due to drier conditions caused by subsurface runoff. The major governing process causing the cooling on the downslope side is heat loss to the atmosphere through evaporation in summer and enhanced heat loss in winter due to wetter conditions and resulting increased thermal conductivity. On a catchment scale, these results suggest that temperature distributions in sloped terrain can vary considerably compared to flat terrain, which might impact the response of subsurface hydrothermal conditions to ongoing climate change.

Study on corrosion mechanism and the risk of the shale gas gathering pipelines

Corrosion and perforation accidents often occur in shale gas gathering and transportation pipelines, which causes serious economic losses. The medium in shale gas gathering pipelines is complex, and the corrosion rate is fast under the combined action of many factors. In this paper, the corrosion mechanism of shale gas gathering and transportation pipelines was studied by field data analysis and experiments. By means of multiphase flow simulation analysis and magnetic flux leakage internal detection, the characteristics and distribution of pipeline corrosion defects were identified, and the corrosion sensitive area was further determined. The results show that in the shale gas gathering pipelines, there were multiple corrosive media of CO2, O2 and SRB. The local corrosion was more serious under the promotion of Cl- and low liquid flow rate. The 3–9o'clock position on the low-lying and uphill section of the pipelines were the corrosion sensitive areas. Through the analysis of internal corrosion mechanism and ERF curves, there were many high-risk corrosion areas in the pipelines.

Walking Characteristics of Dual-Arm Inspection Robot with Flexible-Cable

The overhead transmission line has a catenary shape, which has great influence on the dynamic characteristics of an inspection robot walking along the line and may even cause the walking-wheel to fall from the line. Compared with other similar inspection robots, the unique structure of the dual-arm inspection robot with flexible-cable is introduced. Taking the dual-arm inspection robot with flexible-cable walking along the uphill section of the line as an example, the force states of the robot when it works at acceleration, uniform speed, deceleration, and stopping were studied in detail. The corresponding force balance equations were established, and the walking-wheel torques in each working state were solved. The working states of the robot walking along the catenary shape line were simulated using ADAMS software. Simulation results show that the walking process of the robot is stable, the walking-wheels have good contact with the line, and the forces of two walking-wheels are almost balanced, which enables the robot to have good adaptability and climbing ability for the line. The prototype test that the robot walked along the line was carried out. The results of the simulation and prototype test are consistent with the theoretical analysis, so the rationality of robot structure design is verified. In the future, the navigation control and stability of the robot walking along the line will be researched, so that the robot can complete the patrol task in the real environment.

The Demand of Specific Power for Trucks Operation Safety on The Uphill Section of Expressway

In this paper, the vehicle dynamics simulation software Trucksim was used to build road models and truck models to test the driving speed and climbing distance of 6-axis trucks under different conditions. By comparing with the correlation of the maximum slope length in the “Road Route Design Specification” (JTG D20-2017), we determine the demand of specific power for trucks on expressways with different design speeds. The results show that the initial speed, specific power and slope of the road affect the maximum slope length of the vehicle. The maximum slope length increases with the increase of the initial speed and the specific power of the vehicle and it decreases with the degree of longitudinal slope increases. The Demand of Specific power for trucks on China’s expressways increase with the decrease in design speed, which is 7.0kW/t (120km/h), 8.0kW/t (100km/h), and 9.0kW/t (80km/h) respectively.

Performance and Micro-Pacing Strategies in a Classic Cross-Country Skiing Sprint Race.

The purpose of the present study was to analyze micro-pacing strategies in cross-country skiing, and their relation to section and total race times. Eleven competitive female cross-country skiers were tracked during a classic sprint time-trial race using a global navigation satellite system (GNSS) unit. A coordinate mapping procedure was applied to the GNSS unit measurements to analyze the instantaneous velocities and split times. The track was divided into nine sections and individual section times were calculated. Statistical parametric mapping (SPM) was used to analyze the relationships between instantaneous velocity and section or total race time. SPM analyses revealed two uphill sections and one flat section where greater instantaneous velocities were related to faster total race times. The first major uphill section on the track demonstrated a more conservative micro-pacing strategy (SPM supra-threshold clusters along the entire uphill, p < 0.05–0.001) compared to the more aggressive strategy used in the last uphill section (clusters on the first half of the uphill, p < 0.05–0.001). Faster flat section times were associated with greater instantaneous velocities throughout the section (p < 0.001), while faster downhill section times were related to greater instantaneous velocities at the top of the downhill (p < 0.001), and in the downhill turns (p < 0.001). In conclusion, micro-pacing strategies were related to overall skiing performance and distinct track sections were identified where instantaneous velocities were related to section or total race times. In order to improve skiing performance, athletes could focus on more aggressive pacing early on in the “end spurt”, during the transitions from uphill to flat sections, and during the transitions from flat or uphill to downhill sections.

Experimental study on service performance of epoxy asphalt steel deck pavement of cable stayed bridge

After a cable-stayed bridge was opened to traffic in 2008, as of October 2017, various types of diseases have appeared in epoxy asphalt concrete pavement. However, as of now, the durability evaluation of steel bridge deck pavement is almost blank during the operation period. Therefore, the research team investigated and tested the service performance of epoxy asphalt concrete pavement on the cable-stayed bridge. The results showed that the intensity has attenuated to varying degrees at different positions of the heavy lane, and the most damaged area was the pavement of the uphill section. The crack resistance of the epoxy asphalt mixture was less affected by external conditions. In the composite beam, the bending strength of the mixture was significantly decreased where was under complex stress and threat of disease, and the deformation performance increased initially and then decreased. There was a bridge pavement that was under delamination and complex stress in the single layer beam, the low temperature performance of the lower layer of the pavement was inferior to that of the upper layer of the pavement. The epoxy asphalt mixture had good water stability. The fatigue life of epoxy asphalt mixture was more sensitive to the change of strain, and the change of modulus showed a gradual decay trend. It has been unable to meet the working environment under large strain conditions.

Experimental study of pseudo-slug flow in upward inclined pipes

Pseudo-slug flow occurs between the slug and segregated flows and occupies a non-negligible area in the flow pattern map especially for gas condensate pipeline/wellbore where the liquid flow rate is low. An experimental study was conducted in a 3-in. flow loop with a valley configuration to investigate pseudo-slug flow characteristics using wire-mesh sensors, which include total average liquid holdup, liquid holdups in pseudo-slug body, and film region, respectively, pseudo-slug frequency, body length, and structure velocities.Comparison with conventional slug characteristics shows that pseudo-slugs have lesser liquid holdup in slug body, shorter body lengths, and smaller structure velocities. The pseudo-slug characteristics were also compared with predictions from existing correlations for conventional slug flows, as no correlation is available for pseudo-slug flow. The comparison shows poor agreement as expected, which necessitates the development of correlations for pseudo-slug flow specifically.The spatial evolution of pseudo-slugs is also discussed. Two initiation and dissipation mechanisms are described based on the location where pseudo-slugs are initiated and dissipated. In general, pseudo-slugs are shorter and slower near the inlet of uphill section compared the farther downstream locations in the uphill section.

Lane-Changing Risk Analysis in Undersea Tunnels Based on Fuzzy Inference

Lane-changing in undersea tunnels has a negative impact on the normal traffic flow, and even lays hidden dangers for the occurrence of traffic accidents. Lane-changing behavior in undersea tunnels was divided into free, compulsory, and collaborative lane-changing types according to the characteristics of traffic flow to explore lane-changing risk in undersea tunnels. A fuzzy inference analysis on the three lane-changing behaviors was conducted on the basis of the behavior characteristics of fuzzy uncertainty of drivers. The most representative influencing variables, including speed difference, initial space of vehicles, traffic density, and distance for minimum lane-changing, were selected as fuzzy input variables, and lane-changing risk was used as an output variable to construct fuzzy rules for different lane-changing behavior. Risks of the three lane-changing behaviors were simulated by MATLAB/Simulink. Results demonstrated that the compulsory lane-changing in undersea tunnel was the riskiest, followed by collaborative and free lane-changing. Slope considerably influenced lane-changing risk. Specifically, the lane-changing risk at the downhill section was the highest, and the lane-changing risk at the uphill section was the lowest. The lane-changing risk at the flat section was between them.

Inlet pressure simulation of pigging in uphill gas pipeline

Pipe cleaning is a common operation in the oil and gas industry. In this paper, the governing equation of the pipeline inspection gauge (PIG, lowercase pig is commonly used) speed is combined with the gas flow equations. The method of characteristics (MOC) is used to solve the transient equations of gas flow. And the process of a pig passing over an uphill section of a gas pipeline is simulated. The results indicate that a pig may get stuck in uphill gas pipeline, due to the coupling of the gas and the pig. Under these circumstances, a higher pressure of the upstream could be helpful for driving the pig in motion. Additionally, the ratio of inlet pressure rise during the pigging process is primarily determined by the inclination of the uphill section. In addition, a formula to predict the inlet pressure during pigging in an uphill pipe is presented. Furthermore, the proposed method and solution can be utilized to predict the speed and position of the pig, as well as the gas pressure and the stoppage of the pig in hilly gas pipelines.

Field measurements of the environmental parameter and pollutant dispersion in urban undersea road tunnel

The urban undersea road tunnels located between the islands in the seaside city are featured with high frequent traffic congestions and a strict environmental control standard. A reasonable ventilation system need be built for normal and emergency operation. The fresh air requirement for diluting vehicle pollutants during normal operation can be dominant in urban tunnel. This in turn requires that the main environmental parameters and vehicle pollutants of the tunnel should be sufficiently accurate. Thus, a field measurement was conducted in a real-world urban undersea road tunnel. The temperature, humidity, air velocity, CO, NO2 and PM concentration were tested along the tunnel. The tested results showed that the maximum temperature and relative humidity at the tunnel outlet was 35 °C and 94.5% respectively. The maximum NO2 concentration at the tunnel outlet was 3.73 ppm, the PM concentration at the bottom and outlet of the tunnel were 2030 μg/m3 and 1760 μg/m3 respectively, which exceeded the design threshold value. The emission of CO and NO2 in the uphill section was 2.78 and 1.28 times that in the downhill section respectively. The results can provide beneficial suggestion in ventilation system design and environmental assessment for urban undersea road tunnels, and the basic data in this paper can be used for relevant standard and norm compilation.