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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Analysis of the influence of brake pipe pressure gradient on heavy haul combined train and optimisation of operation strategy</title>
      <link>https://trid.trb.org/View/2633019</link>
      <description><![CDATA[In this paper, based on the theory of gas flow, the action logic of the control valve, and the principle of multi-rigid-body dynamics, a simulation model of the 20,000 t heavy haul combined train is established to investigate the influence of brake pipe pressure gradient on the braking performance, longitudinal dynamics, braking and release characteristics of trains. Utilizing real railway line conditions, locomotive and vehicle parameters, and train operation monitoring equipment (LKJ) record data of Shuozhou-Huanghua Railway, the cyclic braking condition of the train on the long and steep downhill is simulated, and the control strategy of reducing the coupler force during the cyclic braking is proposed. The results indicate that a larger brake pipe pressure gradient before braking leads to weaker braking capability, and higher coupler forces during braking, but smaller coupler forces during release. As the brake pipe pressure gradient before braking increases, braking synchronicity decreases, while release synchronicity slightly improves. By adjusting the locomotive’s electric braking force during the cyclic braking, it is possible to appropriately increase the brake pipe pressure gradient before braking, effectively reducing coupler forces during release and reducing the number of braking cycles, thus lowering the operational difficulty of the train.]]></description>
      <pubDate>Fri, 20 Feb 2026 09:04:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/2633019</guid>
    </item>
    <item>
      <title>Analysis of the impact of air lubrication on the hydrodynamic performance of KVLCC2</title>
      <link>https://trid.trb.org/View/2631330</link>
      <description><![CDATA[The air lubrication system (ALS) reduces frictional resistance, thereby improving ship efficiency. However, its full potential remains underexplored. This study investigates the hydrodynamic performance of a KVLCC2 ship model with ALS at water depth-to-draft ratios of 1.2, 1.5, 2, and 8.3. Two hole diameters, 1 mm and 2 mm, were tested under air flow rates of 0.85, 1.7, 3.4, and 5.1 m³ per hour. Manoeuvring conditions were simulated with different drift angles, and the resulting non-dimensional surge force, sway force, and yaw moment were analysed. The numerical model showed strong agreement with experimental data, with errors below 5 percent. Results indicate that increasing air flow and larger hole diameters increase the hydrodynamic performance. The maximum reduction in hydrodynamic moment, about 9.5 percent, was observed in deep water. Flow analysis confirms these findings and shows that the air layer remains away from the propeller region, which remains unaffected. Overall, the study highlights ALS as an effective method to reduce hydrodynamic forces and moments across a range of water depths.]]></description>
      <pubDate>Wed, 18 Feb 2026 13:22:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/2631330</guid>
    </item>
    <item>
      <title>Pulsating Magnetic Field Effect and Detent Force Analysis of Double-Sided Asymmetric Primary Staggered Tooth Permanent Magnet Linear Synchronous Motor</title>
      <link>https://trid.trb.org/View/2511576</link>
      <description><![CDATA[Double-sided linear motors often encounter significant detent forces. To address this issue, a double-sided asymmetric primary staggered tooth permanent magnet linear synchronous motor (DSAPST-PMLSM) is proposed to suppress detent forces. This structure maintains equal lengths of the upper and lower primaries while having different tooth widths at the ends, forming staggered teeth. However, the staggered teeth introduce pulsating magnetic fields. This article first introduces the structure and principles of the motor for detent force suppression. Then, a magnetic field model that considers magnetic permeability is established by combining mirror imaging and conformal mapping techniques. The effects of the motor’s structural parameters on detent forces are analyzed. Furthermore, the influence of the motor’s structural parameters on the pulsating magnetic field effect is analyzed. The results show that the additional ripple force caused by the asymmetric structure is negligible. Finally, a prototype of the novel double-sided asymmetric primary staggered tooth motor is manufactured, and the motor’s back electromotive force and mechanical characteristics are tested. The results demonstrate that the motor can achieve a maximum acceleration of 60 m/s² and a detent force of approximately 1.8 N, confirming the performance of the proposed motor structure and its effectiveness in suppressing detent forces.]]></description>
      <pubDate>Mon, 16 Feb 2026 17:29:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2511576</guid>
    </item>
    <item>
      <title>Identification of wake structures contributing to aerodynamic drag on an automobile using graph-structured analysis</title>
      <link>https://trid.trb.org/View/2630455</link>
      <description><![CDATA[This study proposes a support method for analyzing unsteady flow fields around an automobile by graph-structured analysis to identify wake structures that contribute to aerodynamic drag. Large eddy simulation was conducted to obtain time series data on total pressure coefficients at several probe points in the wake and the drag coefficient. The dependence between probe points and the drag coefficient was visualized in a directed acyclic graph by graph structured analysis and the key position and times are identified. By focusing on them, the instantaneous flow fields that contributed to drag were successfully identified.]]></description>
      <pubDate>Mon, 09 Feb 2026 08:43:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2630455</guid>
    </item>
    <item>
      <title>Experiment investigation of scour and self-burial of sagging subsea pipelines in steady current</title>
      <link>https://trid.trb.org/View/2627252</link>
      <description><![CDATA[Fundamental mechanisms of the self-burial process of a subsea pipeline that fully sags into a scour hole and the effects of the timing of pipeline sagging on the self-burial are investigated experimentally. Each self-burial experiment starts with an initial scour hole that is generated by a scour experiment for a particular time, which is defined as the touchdown time Ttd. The effects of the touchdown time on the self-burial process are discussed. It was found that, to achieve self-burial, the touchdown time must be delayed to allow a sufficiently deep scour hole to develop. If the touchdown time is too soon, the scour will continue after the pipeline touches down and self-burial will not happen. After touchdown, self-burial initialises at the downstream side of the pipeline and has two stages: pre-self-burial scour and self-burial. The scoured sand behind the pipeline during pre-self-burial scour form a sand dune behind the pipeline and this sand dune is the key mechanisms of self-burial. The growth of this sand dune slows down the flow through the gap and finally stops the scour. Flow visualisation of a sagging pipeline was also conducted using the Particle Image Velocimetry method to understand the flow mechanism at different stages of the self-burial process. If the scour is allowed to fully develop, the pipeline can sag into the scour hole to a vertical distance of 0.7D before self-burial occurs, where D is diameter of pipeline. Based on the visualisation, recirculation of flow downstream to the pipeline plays a significant role in backfilling in the self-burial process.]]></description>
      <pubDate>Tue, 03 Feb 2026 10:07:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627252</guid>
    </item>
    <item>
      <title>Hybrid Deep Learning–CFD Method with Implicit Geometry Representation for Flow Field Reconstruction and Hull Form Optimization</title>
      <link>https://trid.trb.org/View/2648691</link>
      <description><![CDATA[In hull form optimization, obtaining hydrodynamic results is computationally expensive. This study proposes a Hydrodynamic Accelerator based on Deep Neural Networks (HA-DNN) to reconstruct the three-dimensional flow fields around ships, and conducts posterior verification based on the Volume of Fluid (VOF) equation. Concurrently, a fast, high-precision implicit framework termed Conformal Centroid Evolution (CCE) is proposed as an input representation for the accelerator. First, a flow-field dataset encompassing various hull forms was generated using experimentally validated CFD simulations. These hull forms were implicitly encoded in a spatial representation via the CCE method, enhancing the accuracy and efficiency of the deep learning model. Then, the physical conservation of the deep learning model's prediction results was evaluated using the VOF equation. Finally, the proposed method was applied to the construction of a ship total resistance surrogate model. Results indicate that the HA-DNN, utilizing the CCE as input, can accurately learn the mapping between complex hull geometries and three-dimensional flow fields. Compared with the conventional method, the efficiency of constructing the data required for surrogate model training was improved, while preserving predictive accuracy.]]></description>
      <pubDate>Mon, 02 Feb 2026 09:31:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/2648691</guid>
    </item>
    <item>
      <title>The sound source distribution and mechanisms of flow-sound correlation for cavitating propellers</title>
      <link>https://trid.trb.org/View/2627208</link>
      <description><![CDATA[Cavitating propeller is a main underwater sound source in ocean engineering. Its sound source distribution and flow-sound correlation mechanism are of interest for scholars. In this paper, four source components are considered. Large eddy simulation and acoustic analogy are adopted for flow-sound correlation mechanism study. Taking INSEAN E779A propeller as the research object, the predicted noise is compared with the experiments. It is found that the error is less than 6 dB. The correlation between the propeller side force and the dipole sound is high in all frequency bands. The lower the cavitation number, the higher the surface force fluctuation, which is reflected in the increased dipole intensity. The vortex affects the turbulence in the wake region, which contributes to the quadrupole source. The cavitation behavior affects the sphere pressure. The smaller the cavitation number and the larger the std value of the cavitation area, the stronger the sphere source is. The monopole, dipole and quadrupole sound components under non-uniform inflow conditions all exhibit more pronounced narrow-band peaks than those of uniform inflow. DMD results of the propeller wake vortices reveals that the uniform inflow, despite its higher energy at the 1st order mode, decays rapidly at higher order modes, while the non-uniform inflow decays slower, resulting in more pronounced peaks at the higher order frequencies.]]></description>
      <pubDate>Thu, 29 Jan 2026 17:01:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627208</guid>
    </item>
    <item>
      <title>Water wave propagation over two asymmetric trenches in weakly viscous fluid system</title>
      <link>https://trid.trb.org/View/2627085</link>
      <description><![CDATA[Substantial amount of work is available on wave propagation over uneven bottoms and trenches for inviscid fluid. In this work, we extend the study by considering the weakly viscous model of the fluid and emphasize analyzing the impact of viscosity on wave attenuation, dispersion, and flow dynamics using the eigenfunction expansion method. Through numerical analysis, we have observed that viscosity greatly increases energy loss by increasing internal friction, especially in low-frequency and shallow-water cases. In addition to the geometrical configurations of the trenches, viscosity also plays a key role in wave scattering phenomena by reducing the transmission of waves. It also has a remarkable impact on the stress distribution and velocity pattern near the trenches. These findings improve our understanding of the behavior of waves in variable seabeds and asymmetric trenches. From a practical perspective, they provide helpful information for improving navigation safety, reducing harbor oscillations, and designing more effective coastal structures such as harbor entrances and breakwaters.]]></description>
      <pubDate>Mon, 26 Jan 2026 14:44:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627085</guid>
    </item>
    <item>
      <title>Influence of longitudinal and lateral spacing of cubic artificial reefs on flow dynamics and scour volume</title>
      <link>https://trid.trb.org/View/2627054</link>
      <description><![CDATA[The spatial configuration of artificial reefs (ARs) critically influences local hydrodynamics, yet systematic assessments of scour stability and deployment efficiency remain limited. Combining flume experiments and OpenFOAM simulations, this study examines how normalized longitudinal (T/D) and lateral (P/D) spacings affect flow interactions, scour processes, and ecological flow features. Here, T and P denote the longitudinal and lateral spacing between ARs, respectively, and D is the AR edge length. Results show that longitudinal spacing transitions from pronounced flow shielding (T/D ≤ 0.5) to peak wake vortex interactions (T/D = 1.0–2.0) and finally independent wakes (T/D > 2.0), directly impacting scour intensity, turbulence, and beneficial ecological flow features like upwelling. Similarly, lateral spacing shifts from merged wakes (P/D = 0) to enhanced gap flows (P/D = 0.5–1.0) and decoupled patterns (P/D ≥ 1.5). A comprehensive evaluation index (Ib) balances ecological benefits, scour stability, and deployment costs, identifying optimal spacings (T/D = 1.0–1.5, and P/D = 1.5–2.0) across multiple weighting scenarios, validated via Monte Carlo simulations. These findings deepen our fundamental understanding of hydrodynamic-scour interactions and offer theoretical foundations and practical guidelines for sustainable marine ranching and the optimal design of offshore ecological infrastructure worldwide.]]></description>
      <pubDate>Mon, 26 Jan 2026 14:44:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627054</guid>
    </item>
    <item>
      <title>Long-duration blast loading of box girder with complex cross-section</title>
      <link>https://trid.trb.org/View/2632250</link>
      <description><![CDATA[Long-duration blast waves are commonly encountered in the far-field of large-scale explosions, with a positive pressure duration exceeding 100 ms. It is crucial to consider not only the impact of the diffraction loading on structures but also the dynamic pressure effects of drag loading, which significantly differ from short-duration blast waves experienced in near-field explosions. The box girder is extensively employed in bridge construction, and its loading characteristics are complex due to the intricate flow field surrounding it. Numerical analysis is conducted to examine the long-duration blast loading on the box girder for various aspect ratios (W/B=1–4, width-to-height ratio) and incident overpressures (Pi,max=100 kPa-1000 kPa). This includes investigating drag, lift, and moment characteristics, analyzing the distributions of reflected overpressure and impulse, as well as comprehending the flow field structure and its mechanism. Our findings demonstrate a consistent decrease in the drag coefficient as the incident overpressure increases. An initial increase followed by stabilization is observed in the drag coefficient with increasing aspect ratio, while both amplitude and duration of lift and moment show an increasing trend. Interestingly, there exist notable differences in peak impulse due to diverse flow structures despite the similar distribution of peak reflected overpressure across box girders with different aspect ratios.]]></description>
      <pubDate>Fri, 23 Jan 2026 09:58:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/2632250</guid>
    </item>
    <item>
      <title>Research on the cavity flow and motion characteristics of vehicle launched underwater in waves</title>
      <link>https://trid.trb.org/View/2633432</link>
      <description><![CDATA[The underwater vertical launch of a vehicle involves a complex gas-liquid mixing process. Upon water exit, the large-scale collapse and shedding of attached cavitation generate high-frequency transient impact loads on the vehicle surface, significantly influencing its load distribution and motion trajectory. Under extreme sea conditions with wave activity, strong disturbances of the wave surface particles complicate the evolution and development of cavitation during water exit. This paper presents numerical simulations of a vehicle exiting water in a wave environment, focusing on the influence of wave phase on the evolution of the multiphase flow field and the motion characteristics of the vehicle. Results show that cavitation exhibits significant asymmetric evolution during water exit at the crest and trough. At the crest phase, the cavity size on the downstream side is considerably larger than that on the upstream side, while the opposite occurs at the trough phase. Simultaneously, the vehicle experiences a pair of lateral loads characterized by narrow pulse widths, substantial magnitude differences, and a noticeable time lag. The load on the side with larger cavitation is several times greater than on the opposite side. When exiting at the crest and trough phases, the vehicle's trajectory and deflection angle curves exhibit significant deviations, with opposite deflection directions between the two phases. In contrast, the motion characteristics at the pre-crest and post-crest phases are closer to those in calm water, with minimal deflection.]]></description>
      <pubDate>Fri, 09 Jan 2026 16:59:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/2633432</guid>
    </item>
    <item>
      <title>An Automated Airborne Support Tool for Aircraft Emergencies: Selection of Landing Sites and 4D Diversion Trajectories</title>
      <link>https://trid.trb.org/View/2553346</link>
      <description><![CDATA[We present a software prototype (SafeNcy) capable of automatically choosing and ranking landing sites for emergency situations and of generating four-dimensional (4D) trajectories towards these sites. We describe the modules composing this framework, together with their main capabilities, interactions and the workflow of the full integrated system. Different types of emergencies are firstly categorized. Then, for each type of emergency, landing sites—including off-airport locations—are ranked, and speed and vertical trajectory descent profiles are tailored accordingly. These algorithms take into account several data from different sources, such as terrain databases, weather forecasts and aircraft performance models. We outline a new concept of operations aiming to integrate SafeNcy into the current aircraft operations and air traffic management paradigms. Several scenarios, focusing on total engine flame-out situations, are described and used to validate the framework, as well as to show its main features. The scenarios were designed in cooperation with a group of expert pilots and engineers. SafeNcy is expected to be an additional function for advanced and extended flight management systems, alleviating flight crew’s workload and contributing to a more digital cockpit. It could also be a technical enabler for future unmanned or highly-automated aviation.]]></description>
      <pubDate>Mon, 05 Jan 2026 09:53:59 GMT</pubDate>
      <guid>https://trid.trb.org/View/2553346</guid>
    </item>
    <item>
      <title>Numerical study on propeller flow field in four quadrants</title>
      <link>https://trid.trb.org/View/2631019</link>
      <description><![CDATA[The propeller hydrodynamic performance under different direction combinations of the uniform inflow and the propeller rate, i.e. four quadrants (Q1–Q4) conditions, is studied with CFD methods, and validated by the experimental data of a model-scale propeller. The numerical strategies including the turbulence model, the grid size, and the time step are discussed. Regarding the relative direction of the inflow and the propeller jet, RANS (Reynolds-Averaged Navier–Stokes) and DDES (Delayed Detached Eddy Simulation) are compared in resolving global and local flow quantities. RANS results show similar near-field flow fields to DDES results in Q1/Q3, while DDES gives more accurate forces and richer flow details such as vortex resolutions for cases with opposite flow directions. Then the propeller is simulated by RANS in Q1/Q3, and by DDES in Q2/Q4. In four quadrants, the propeller thrust and torque, vortex structures, and velocity and pressure distributions are presented for flow mechanism analysis. In Q1/Q3 conditions, the propeller jet evolves in the same direction as the inflow, promising a converged flow field. In Q3, the reverse rotation leads to less significant flow acceleration effects than Q1 under the same inflow velocity, and the non-uniformity of pressure distributions on the blades is strengthened. For Q2/Q4, massive flow separations occur due to the interaction of the propeller jet and counter inflow, and the recirculation zone with reversed axial velocities forms. With increased inflow velocities, the dominant role between the inflow and the propeller jet gradually shifts, and the difference in the propeller jet produced by ahead and astern rotations postpones the shift in Q2 compared with Q4. This study investigates the propeller flow field in four quadrants and can help to quantify rudder inflow variations in hull-propeller-rudder interactions for future research.]]></description>
      <pubDate>Wed, 31 Dec 2025 10:58:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2631019</guid>
    </item>
    <item>
      <title>Effect of spray targeting and energy-assisted ignition on in-flame flow fields in an optical compression ignition engine</title>
      <link>https://trid.trb.org/View/2612398</link>
      <description><![CDATA[The present study applies high-speed Mie-scattering spray imaging and flame image velocimetry (HS-FIV) to a jet fuel flame in a small-bore optical compression-ignition engine. The integration of sustainable aviation fuel (SAF) into the jet fuel supply may introduce challenges for stable engine operation due to low fuel reactivity. To resolve this issue, the engine is equipped with an ignition assistant plug providing additional heat into the compressed air. The impact of ignition assistant on the combustion of low reactivity fuel varies with injector tip protrusion, requiring detailed optical analysis to evaluate how the spray targeting changes relative to the piston bowl and thermal distributions. An optical engine is operated on a blend of 40% SAF and 60% F-24, a conventional jet fuel with mil-spec additives. The injector tip protrusion was varied between 1.5 and 4.5 mm below the cylinder head and for each protrusion, the high-speed movies were obtained with 30 cycles for sprays and 100 cycles for flames to address uncertainty concerns. The spray images were post processed via image binarisation to compute the liquid penetration length. An ensemble averaging method was applied to the FIV-derived flow fields to show the in-flame flow structure development while a spatial filtering approach was used for flow turbulence and combustion stability analysis. The spray image results exhibited decreased liquid penetration length and higher vaporisation for deeper injector tip protrusion, indicating higher temperature within the piston bowl. When the ignition assistant plug was activated, the FIV results showed similar overall flow structures and flow magnitude distribution to the plug off condition despite more advanced combustion phasing. However, lower cyclic variation was measured for the plug on condition, indicating more stable combustion as a key benefit of the active energy assistance. Regarding the injector tip protrusion variation, the shortest depth of 1.5 mm showed more retarded combustion phasing and lower peak pressure than those of 3.0 mm despite higher wall bounced-off flow magnitude. Enhanced vaporisation of the tested fuel blend as the injector tip was positioned deeper into the bowl was a likely cause of this observed trend. However, as the injector tip was protruded further to 4.5 mm, the combustion phasing was also more retarded and peak pressure was lower than those of 3.0 mm. Detailed flow field analysis showed lower magnitude flow vectors were observed for 4.5 mm depth as the jet impinged more on the floor of the piston bowl than the wall. The decreased wall bounce-off flow for deeper injector tip protrusion also led to lower flow turbulence measured in the r-θ plane. This outperformed higher fuel vaporisation expected, and thus the injector tip protrusion depth of 3 mm showed the most advanced combustion phasing and lowest cyclic variations.]]></description>
      <pubDate>Tue, 30 Dec 2025 09:46:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2612398</guid>
    </item>
    <item>
      <title>Prediction of Electromagnetic Vibration With Discrete Force–Response Matrix for Permanent Magnet Synchronous Motor</title>
      <link>https://trid.trb.org/View/2604080</link>
      <description><![CDATA[In view of the actual characteristics of electromagnetic (EM) force are ignored in existing vibration calculation models, this article proposes a hybrid calculation model based on a discrete force–response matrix for predicting EM vibration. Initially, the subdomain method is employed to calculate the air-gap force density (AGFD). Based on the mapping principle of air-gap force, an equivalent distributed force model is introduced, which accounts for the uneven distribution of radial and tangential EM forces on the tooth heads. Next, a frequency response function (FRF) model is developed to correspond with the distributed force. This model incorporates the circumferential variation of the FRF, and the differences in distribution patterns are analyzed. Subsequently, a vibration prediction model based on multipoint excitation and the multipoint response method is established. Finally, the accuracy of the proposed model is validated through vibration testing of the prototype, and the motor’s vibration modes are also confirmed.]]></description>
      <pubDate>Mon, 29 Dec 2025 09:37:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2604080</guid>
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