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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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    <language>en-us</language>
    <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>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Beyond uniform roughness: Ship resistance with spatially non-uniform hull surface conditions</title>
      <link>https://trid.trb.org/View/2670605</link>
      <description><![CDATA[Traditional ship resistance models often assume uniform hull surface roughness, potentially misrepresenting the heterogeneous fouling patterns observed in real-world operations. To address this limitation, we investigate the hydrodynamic impact of spatially non-uniform roughness on a KRISO Container Ship (KCS) hull using Computational Fluid Dynamics (CFD) simulations.Seven hull surface conditions were investigated, including a smooth baseline and six types of roughness distributions: uniform, linear gradient, non-linear gradient, random, direct-shear, and inverse-shear. All cases were designed to have the same arithmetic mean hull surface roughness, allowing isolation of the effects of spatial roughness distribution. Among the tested configurations, the linear gradient distribution exhibited the most favourable resistance characteristics, whereas the shear-based and random distributions showed relatively minor differences from the uniform case.Spatial roughness patterns significantly influenced boundary layer growth and wake development. Uniform, random, and shear-based distributions induced thicker boundary layers and delayed wake recovery, whereas the linear gradient case resulted in weaker momentum loss and faster wake recovery.These findings indicate that even under identical arithmetic mean roughness conditions, the spatial distribution of hull surface roughness can significantly affect resistance characteristics. Explicit modelling of roughness patterns is therefore essential for accurate performance prediction and motivates further experimental validation and integration with propeller-hull interaction and free surface effects.]]></description>
      <pubDate>Tue, 24 Feb 2026 09:02:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/2670605</guid>
    </item>
    <item>
      <title>Finding the Bed Shear Stress Using the Logarithmic Law at Channel Roughness Transitions</title>
      <link>https://trid.trb.org/View/2672767</link>
      <description><![CDATA[Flow through transition of bed roughness occurs in many situations in highway transportation including culverts, bridge abutments, and roadways in the floodplain, where the bed materials can change abruptly from one type to another. A sudden change in bed roughness also occurs frequently in the laboratory when soil erosion and scour is studied using a sediment recess in an open-channel flume. In all the above, the bed shear stress is a fundamental flow parameter that must be determined accurately.

A research project is proposed to investigate the use of logarithmic law (log law) for finding bed shear stress near a sudden change in bed roughness. Velocity field measurements will be obtained using a Particle Image Velocimetry (PIV) system. The measured data will be used to determine the distribution of bed shear stress by control volume analysis using the linear momentum equation to determine whether the log law can be applied to a developing boundary layer downstream of a bed roughness transition and develop procedures to reduce the measurement uncertainty of the method.]]></description>
      <pubDate>Mon, 23 Feb 2026 13:58:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/2672767</guid>
    </item>
    <item>
      <title>Study on hydrodynamic noise characteristics of stiffened cylindrical shell with multilayer gradient acoustic coating</title>
      <link>https://trid.trb.org/View/2660734</link>
      <description><![CDATA[In this paper, the hydrodynamic noise characteristics of a finite stiffened cylindrical shell submerged in water are studied. The shell is covered with a multilayer gradient acoustic coating, and its outer surface is subjected to excitation of turbulent boundary layer (TBL) pressure fluctuations. The power spectral density (PSD) function of the modal pressure induced by TBL pressure fluctuations is computed using two analytical methods: the direct extension method and the comb function method. These methods extend the TBL wavenumber-frequency spectrum from planar to cylindrical surfaces through different approaches. Furthermore, the hydrodynamic noise predicted by these analytical methods is compared with results obtained via the finite element method and the statistical energy analysis (SEA) method. The comb function method is demonstrated to be more effective in accurately predicting the hydrodynamic noise of finite cylindrical shells. Additionally, variations in the acoustic impedance, density and sound velocity of the coating in the radial direction are explored to determine their impact on hydrodynamic noise control. The results show that, compared to an uncoated shell, a multilayer gradient acoustic coating with optimized parameters can significantly attenuate the hydrodynamic noise of a finite stiffened cylindrical shell.]]></description>
      <pubDate>Wed, 11 Feb 2026 15:10:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2660734</guid>
    </item>
    <item>
      <title>Impinging Shockwave/Boundary Layer Interaction–Induced Separation
                    Mitigation Using Passive Control</title>
      <link>https://trid.trb.org/View/2639320</link>
      <description><![CDATA[
                
                A passive control device to mitigate shock-induced separation in a generic
                    supersonic inlet model is computationally studied. The simulations were based on
                    the Favre-averaged Navier–Stokes equations with the Spalart–Allmaras (SA)
                    turbulence model. The shockwave was generated by an 8° turn supersonic inlet.
                    The Mach number in the inlet was varied between 2.1 and 2.46. The baseline
                    shockwave/boundary layer interaction (SBLI) simulation results compare favorably
                    with experimental data. The passive device, in the form of a splitter plate,
                    eliminates both the separation and flow unsteadiness. The splitter plate causes
                    reduction in the total pressure of the boundary layer at the exit of the inlet
                    due to increased skin friction on the floor and due to wake of the plate.
            ]]></description>
      <pubDate>Thu, 15 Jan 2026 14:31:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/2639320</guid>
    </item>
    <item>
      <title>A Quasi-Two-Dimensional Approach in Laminar Flow of Lubricating Oil and Grease</title>
      <link>https://trid.trb.org/View/2604482</link>
      <description><![CDATA[The overarching objective of the present study is to apply a quasi-two-dimensional approach to analyze the laminar flow of lubricating oil. Lubricating oils are non-Newtonian by nature. For these types of oils, the Sisko fluid model is the most suitable model of the nonlinear stress–strain relationship for these types of oils. It is hoped that by omitting the dependence of flow quantities in one direction, more qualitative information can be obtained on the characteristics of the purely three-dimensional boundary layer flow of lubricating oils. Some of the most familiar flow geometries discussed are steady flow over a flat plate, a corner of a wedge, and a stagnation region; steady flow in a convergent and divergent channel; and impulsively started flow over an infinite flat plate and semi-infinite flat plate. The governing equations of all flow geometries are transformed into nonlinear ordinary differential equations (ODE) using the free parameter transformation. The results are discussed briefly in the graphical presentation.]]></description>
      <pubDate>Tue, 02 Dec 2025 09:25:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/2604482</guid>
    </item>
    <item>
      <title>Influence of local slip boundary condition on the hydrodynamic performance of hydrofoils for cross-domain vehicles at low Reynolds number</title>
      <link>https://trid.trb.org/View/2623639</link>
      <description><![CDATA[Slip boundaries exhibit significant potential for modifying the near-wall flow field, which has a critical significance for the hydrodynamic performance of hydrofoils in cross-domain vehicles (CDV) such as lift enhancement and drag reduction. The effect of slip conditions on hydrofoil hydrodynamic performance at moderate Reynolds numbers (Re) has been well recognized, while it is yet not clear for the local slip condition at low Re. This study utilizes a combined numerical and experimental approach to explore the impact of local slip boundaries on the hydrodynamic performance of a hydrofoil at a low Re of 5000. Specifically, it examines the influence of four distinct slip modes—no-slip (N), full-slip (F), suction-surface-slip (S), and pressure-surface-slip (P)—on the hydrofoil's hydrodynamic characteristics. Both F and S modes can enhance the lift, and the S mode exhibits superior performance. In contrast, the P mode shows negligible impact on lift. Meanwhile, both F and S modes can suppress separation and reduce resistance. P has a small inhibitory effect on separation and a weak effect on drag reduction. In addition, both the F and S modes significantly enhance the flow stability of the hydrofoil by suppressing vortex shedding and inducing a transition of the shedding mode from alternating to continuous. This stabilizing effect becomes more pronounced with increasing slip length. In contrast, the P mode shows no observable improvement in flow stability. These findings provide valuable insights for optimizing hydrofoil design for the CDV.]]></description>
      <pubDate>Fri, 21 Nov 2025 08:44:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/2623639</guid>
    </item>
    <item>
      <title>Investigating Impact of Boundary Layer in Pervious Concrete</title>
      <link>https://trid.trb.org/View/2407387</link>
      <description><![CDATA[Pervious concrete is a green concrete because of its environmental benefits including reduced carbon footprint. However, industrial application of pervious concrete is limited by uncertainty of its mechanical properties. While porosity plays an important role in mechanical properties and understanding on porosity distribution and characteristics is essential in optimising design of pervious concrete. Image analysis is a modern tool which could employ different analyses techniques and significantly reduce error than in conventional methods of analysing porosity. This study aims to analyse distribution of porosity in pervious concrete, using image analyses tools. Cubes were cast, cores were obtained, and images of the surfaces were painted and photographed. Image was converted to binary and analysed and total porosity of cubes were obtained. A small layer in the top and bottom have high porosity than total porosity and between those layers the porosity, which is lower than total porosity, is called effective porosity. Therefore, the top and bottom boundary layers were analysed with design parameters. Top boundary layer of a concrete cube is 4.7 mm and it does not depend on design parameters. The bottom boundary layer of the concrete cube increases with the aggregate to cement ratio and decreases with applied compaction energy. For blows more than 45, the bottom boundary layer does not significantly change. Minimum required number of blows for the 1st layer of the cube to get optimum bottom boundary layer is 10 for all Aggregate to cement ratio (A/C) except for design with A/C of 2.5.]]></description>
      <pubDate>Mon, 22 Sep 2025 08:49:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/2407387</guid>
    </item>
    <item>
      <title>Moving air-water interface on no-slip solid walls for high-speed planing hulls</title>
      <link>https://trid.trb.org/View/2559100</link>
      <description><![CDATA[In this study, the classical ‘moving-contact-line’ problem associated with the no-slip boundary condition (BC) is examined, with a particular focus on large-scale, high Reynolds number turbulent ship flows. Numerical ventilation is one of the main issues reported for the computational prediction of the high-speed small planing craft using the Volume-of-Fluid (VOF) method. A numerical strategy is presented to resolve this issue with a wave blanking distance defined and used when solving the VOF equations, which is chosen based on the 𝑦⁺ values and the velocity profiles in the boundary layer. A series of numerical tests are conducted using a slamming plate and a stepped high-speed planing hull. The numerical experiments show that if the blanking distance is 𝑦⁺ < 30 (inside the buffer and viscous sublayers), the air-water interface on the wall will be unstable and numerical ventilation will occur. For the blanking distance 𝑦⁺ < 30 (outside the buffer layer), the air-water contact line is smooth and air entrainment can be avoided. It is suggested that the blank distance needs to satisfy 30.0 < 𝑦⁺ < 200.0 in consideration of accuracy and stability, and a value of 𝑦⁺ ∼ 100.0  can be used in practice.]]></description>
      <pubDate>Wed, 10 Sep 2025 09:23:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/2559100</guid>
    </item>
    <item>
      <title>Acoustic vibrations of underwater double-walled cylindrical shells with elastically restrained boundaries</title>
      <link>https://trid.trb.org/View/2578072</link>
      <description><![CDATA[Underwater cylindrical shells are widely used in the construction of submarines and torpedoes, and are often strengthened with double walls containing complexly shaped support members. During service, the structures of double walls can undergo acoustic vibration, leading to functional failure of sensitive equipment. Thus, it is essential to control and manage such vibrations to preserve the functionality and integrity of an underwater cylindrical shell. The aim of this study is to develop an analytical method to characterize acoustic vibrations in underwater double-walled cylindrical shells with arbitrary elastic connections along their boundaries. Accordingly, spring models with arbitrarily shaped boundaries are built to capture translational and rotational movements of an underwater double-walled cylindrical shell; a spring–mass model is used to represent elastically restrained connections between the outer and inner shells; and then Flügge shell theory, together with improved Fourier series and model expansion approaches, are utilized to solve the acoustic wave problem. This method is validated in terms of natural frequency and radial mean velocity level by comparison with physical test and finite-element analysis results available in the literature. Furthermore, the method is used to perform a parametric study by varying the stiffness of elastically restrained boundary connections. The results indicate that when the stiffness of the connections between the outer and inner shells is small, acoustic vibrations are primarily transmitted by the main channel, but when the stiffness of the connections increases, acoustic vibrations are primarily transmitted by these connections.]]></description>
      <pubDate>Wed, 13 Aug 2025 09:25:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2578072</guid>
    </item>
    <item>
      <title>Hydraulic Design of a Component Cavity-Free Drains at Transient Water Flow in the Aggregate</title>
      <link>https://trid.trb.org/View/2407918</link>
      <description><![CDATA[Scope: To develop a method for the hydraulic calculation of composite cavity-free drains in transient mode. Previously, a methodology was proposed for the hydraulic calculation of composite cavity-free drains, but only in the laminar regime, which takes place in a finer aggregate than the crushed stone used in the ballast prism. Methods: The cavity-free drainage is used in agriculture, engineering flood protection and environmental pollution control systems. There are proposals for effective dewatering and increasing the bearing capacity of railway and road beds to use continuous drains with different shapes of live cross-sections, including a composite profile. By replacing the composite profile of the live section with an equivalent rectangular one, the resulting differential equation is reduced to the previously solved analogous equation for the rectangular cross section. Results: Calculated dependencies for determining the water depth in the composite cavity-free drainage system and the spacing of the collectors in the case of two-way drainage inlets have been obtained. Practical relevance: The proposed calculation method will make it possible to justify the sizing of cavity-free drains, leading to a rational use and saving of the drainage fill material.]]></description>
      <pubDate>Thu, 31 Jul 2025 13:58:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/2407918</guid>
    </item>
    <item>
      <title>A two-dimensional numerical and experimental study of resonant coupled ship and piston-mode motion</title>
      <link>https://trid.trb.org/View/2567393</link>
      <description><![CDATA[The authors consider resonant coupled ship and piston-mode motion in a two-dimensional setting. The setting is that of a ship section moored by a bottom mounted terminal which are exposed to regular waves. The ship section is allowed to oscillate in three degrees of freedom: Sway, heave and roll. They investigate in particular the damping caused by flow separation from the bilge keels. This has importance near resonance. The investigation is carried out by means of model tests as well as by a linear wavetank and a fully nonlinear numerical wavetank. Both are time-domain wavetanks based on a Boundary Element Method (BEM) and the mixed Eulerian–Lagrangian (MEL) formalism. Flow separation is modelled in the nonlinear numerical wavetank by means of an inviscid vortex tracking method. They focus on the, under resonant condition, large-amplitude massive piston-like fluid motion in between the ship and the terminal and the associated large ship motions. They do not focus on the sloshing problem associated with higher modes. In resonant condition, large piston-mode motion occurs when the sway and heave motions are downwards and towards the terminal simultaneously.An alternative formulation of the forces and moment is derived and implemented into the nonlinear numerical wavetank as a means to circumvent the problems related to the φt term in the Bernoulli equation in the presently adopted MEL approach.]]></description>
      <pubDate>Tue, 01 Jul 2025 13:38:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/2567393</guid>
    </item>
    <item>
      <title>Effect of the Leading-Edge Tubercles on the Aerodynamic Performance of Transonic Cascades under High Static Pressure Rise</title>
      <link>https://trid.trb.org/View/2554049</link>
      <description><![CDATA[Under high static pressure rise conditions, flow separation in transonic compressor cascades is severe, exacerbating the performance degradation of the compressor cascades. Biomimetic flow control techniques, as a category of passive flow control technologies, hold promise for improving the performance degradation of transonic cascades under high static pressure rise conditions. Therefore, this paper takes the DLR transonic cascade L030-4 as the baseline cascade and investigates the impact of biomimetic leading-edge tubercles on the aerodynamic performance of transonic cascades under high static pressure rise conditions. This paper employs numerically simulated methods validated by experiments to obtain the variation laws of the total pressure loss coefficient and the leading-edge peak diffusion factor of the transonic cascade with biomimetic leading-edge tubercles as the static pressure rise increases. In the wavy leading-edge cascade, streamwise vortices and surface separation bubbles are observed, and the relationships between the development direction of streamwise vortices and static pressure rise, as well as between streamwise vortices and surface separation bubbles, are discovered. The study shows that biomimetic leading-edge tubercles can reduce flow separation at high static pressure rises by inducing the generation of streamwise vortices, thereby effectively reducing the total pressure loss and decreasing the leading-edge peak diffusion factor. Moreover, the effect of increasing static pressure rise is similar to that of increasing the angle of attack, both of which have the effect of changing the inlet angle of the blade. As the static pressure rise increases, the streamwise vortices gradually shift from developing along the pressure side to developing along the suction side. The streamwise vortices can cause the laminar separation bubbles induced by shock/boundary layer interaction to transition into turbulent separation bubble structures.]]></description>
      <pubDate>Tue, 01 Jul 2025 13:38:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/2554049</guid>
    </item>
    <item>
      <title>Numerical simulation of oscillating flows over a bed-mounted circular cylinder</title>
      <link>https://trid.trb.org/View/2567248</link>
      <description><![CDATA[An immersed boundary (IB) method has been used to simulate oscillating flows over a bed-mounted circular cylinder at Reynolds number Re=1100. Two Keulegan–Carpenter (KC) numbers are considered in the study. For the smaller number of 0.99, there is no boundary layer separation and hence the flow is relatively simple. The acting forces on the cylinder can be evaluated by the potential theory. For the larger KC number of 6.6, the flow is very complicated due to the interactions between the shed vortices and the cylinder. The mechanisms of the boundary layer separation, vortex shedding and motion are explored by carefully calculating the transient vorticity field near the cylinder. In particular, the predicted vortex pair movement towards the bed is consistent with other researchers’ experimental flow visualization and is well explained by this numerical investigation. In addition, possible local scouring near the cylinder is suggested by the calculation of the bed shear stress and is proved by laboratory experiments. The acting force on the cylinder is also explained in relation to the patterns of the flow field.]]></description>
      <pubDate>Mon, 30 Jun 2025 17:27:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2567248</guid>
    </item>
    <item>
      <title>Research on the Noise Reduction Mechanisms of Bionic Airfoils with Different Serrated Trailing-Edge Structures</title>
      <link>https://trid.trb.org/View/2522050</link>
      <description><![CDATA[Inspired by the silent flight capability of owls, the serrated trailing-edge design is recognized as an effective method to control trailing-edge interference noise arising from turbulent boundary layers. Based on the NACA0018 airfoil and the serrated structures found in owl wings, this paper designs five different bionic airfoils featuring varying serration heights and spacings. By utilizing large eddy simulation and the Ffowcs Williams-Hawkings acoustic analogy model, we explore the noise reduction mechanism of the serrated trailing edge and validate the accuracy of the numerical methods employed. At an angle of attack of 6°, the study investigates the effects of serration spacing and height on the flow structure near the trailing edge, far-field noise, and noise reduction capabilities of the airfoils. It is found that the serrated trailing edge mitigates the separation of the turbulent boundary layer near the trailing edge, causing separation vortices to shift toward the trailing edge and enabling fluids to adhere more readily to the airfoil surface. This, in turn, reduces noise generated by vortex shedding. As the serration height 𝐻 increases, the noise reduction effect becomes more pronounced, whereas the effect of serration width 𝐿 on noise reduction is less distinct. Among the designs, the H2.5L10 and H5L5 airfoils exhibit the best noise reduction performance. Furthermore, acoustic field analysis reveals that the bionic serrations are beneficial in reducing mid-to-low-frequency noise. Through a comprehensive analysis of both flow and acoustic fields, this paper sheds light on the influence of serration parameters on airfoil noise reduction, providing crucial theoretical foundations for noise reduction in large-scale equipment such as axial flow fans and wind turbines.]]></description>
      <pubDate>Thu, 17 Apr 2025 16:55:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/2522050</guid>
    </item>
    <item>
      <title>A Laminar Flow, Propulsive, Jet-Flapped Concept for Electrically Powered Transport Aircraft</title>
      <link>https://trid.trb.org/View/2470726</link>
      <description><![CDATA[Friction drag constitutes approximately half of the total drag of subsonic civil transport aircraft at cruise conditions. Several means were examined to control the flow over an aircraft and achieve laminar flow. Here, a new concept for friction drag reduction in the form of an integration of the aerodynamics and propulsion of the aircraft is put forward. Engines buried in the wing and at the rear of the fuselage suck the boundary layer of the entire wing and fuselage surface, and then, they used it as intake air and exhaust through ducts. At the wings, the engines exhaust in the form of a jet flap at the trailing edge providing distributed propulsion. By this laminar flow, propulsive concept laminar flow is established over the entire aircraft, resulting in substantial drag reduction. The analysis showed that out of the four electrically powered aircraft versions considered only the combined lift distribution with tailless fuselage is about to be feasible. It was also found that the example aircraft design is inappropriate. It is expected that a design purposely based on the proposed concept would bring electrically powered transport aircraft within the specific energy levels of present batteries.]]></description>
      <pubDate>Mon, 30 Dec 2024 17:01:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2470726</guid>
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