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    <title>Transport Research International Documentation (TRID)</title>
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    <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>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>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 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>
    </item>
    <item>
      <title>Impact of flow regime on the performance of anti-biofouling coatings</title>
      <link>https://trid.trb.org/View/2201938</link>
      <description><![CDATA[Biofouling poses significant challenges for marine transportation due to increased skin drag, which results in increased fuel cost and associated [Formula: see text] emissions. Current antifouling methods involving polymer coating, biocides, and self-depleting layers harm marine ecosystems and contribute to marine pollution. Significant advancements have resulted in using bioinspired coatings to address this issue. However, prior investigations have predominantly focused on wettability and adhesion aspects, resulting in a limited understanding of the impact of flow regime on bioinspired structure patterns for antifouling. The authors conducted comprehensive experiments with two bioinspired coatings1 under laminar and turbulent flow regimes and compared them with a smooth surface. The two coatings are composed of regular arrangements of micropillars measuring 85 mum in height and spaced at 180 mum (pattern A) and 50 mum high micropillars spaced at 220 mum (pattern B). Theoretical arguments indicate that wall-normal velocity fluctuations near the micropillars' top significantly contribute to reducing the onset of biofouling under turbulence compared to the smooth surface. Pattern A coating can effectively decrease biofouling by 90% for fouling sizes exceeding 80 microns when compared to a smooth surface subjected to a turbulent flow regime. The coatings exhibited comparable anti-biofouling properties under a laminar flow. Also, the smooth surface experienced substantially higher biofouling under laminar flow compared to turbulent conditions. This underscores how the effectiveness of anti-biofouling approaches is critically influenced by the flow regime.]]></description>
      <pubDate>Thu, 27 Jul 2023 16:55:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/2201938</guid>
    </item>
    <item>
      <title>Transition Prediction for Hybrid Laminar Flow Control Flight Test Considering Geometric Uncertainties</title>
      <link>https://trid.trb.org/View/2021893</link>
      <description><![CDATA[Due to its significant capability for energy and environmental sustainability, the hybrid laminar flow control (HLFC) shows excellent technical appeal for civil aircraft. To use computational tools to speed up the HLFC design process, it is crucial to accurately predict the transition location and reveal the coupling mechanism of suction control and pressure gradient. The authors carry out HLFC wing glove flight experiments under different flight conditions. More than 40% chord laminar flow region is maintained for some flight conditions. They then perform numerical simulations based on the eN method. The good agreement between the deterministic simulation and experimental data indicates that the eN-based method using the critical N factor from natural laminar flow (NLF) can capture Tollmien–Schlichting (TS) instabilities for HLFC under similar conditions. For the HLFC simulation, the suction velocity is determined using an algebraic model as a boundary-layer condition, which is verified by the test data. The authors further consider geometric uncertainties to the laminar-to-turbulent transition prediction. They conclude that as long as TS instabilities are fully suppressed in the leading edge region, the variation of stochastic solutions about predicted transition locations is less than 8% chord for most flight conditions. Besides, experimental results locate in the given confidence intervals. For this wing glove test, both deterministic and uncertainty transition prediction results of the HLFC wing by using the critical N factor of TS waves calibrated throught NLF experiment agree with HLFC experiment well.]]></description>
      <pubDate>Wed, 30 Nov 2022 10:59:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/2021893</guid>
    </item>
    <item>
      <title>Numerical Investigation of Laminar Burning Velocities of High Octane Fuel Blends Containing Ethanol</title>
      <link>https://trid.trb.org/View/1817958</link>
      <description><![CDATA[Recently, fuels containing ethanol have become more and more important for spark ignition engines. Fuels with up to 10 vol.-% ethanol can be used in most spark ignition engines without technical modification. These fuels have been introduced in many countries already. Alternatively, for fuels with higher amounts of ethanol so called flex fuel vehicles (FFV) exist. One of the most important quantities characterizing a fuel is the laminar burning velocity. To account for the new fuels with respect to engine design, reliable data need to be existent. Especially for engine simulations, various combustion models have been introduced which rely on the laminar burning velocity as the physical quantity describing the progress of chemical reactions, diffusion, and heat conduction. However, there is very few data available in the literature for fuels containing ethanol, especially at high pressures. A detailed chemical kinetic mechanism for iso-octane, n-heptane, and ethanol is used to calculate laminar burning velocities under engine relevant conditions. The results are validated against data from literature and new experimental measurements using the closed-vessel bomb method. Finally, based on the results obtained, the effect of ethanol blended to standard fuels is analyzed.]]></description>
      <pubDate>Mon, 24 Oct 2022 10:22:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/1817958</guid>
    </item>
    <item>
      <title>Static roughness element effects on protuberance full-span wing at micro aerial vehicle application</title>
      <link>https://trid.trb.org/View/1992973</link>
      <description><![CDATA[Although the tubercle wings provide good maneuverability at post-stall conditions, the aerodynamic performance at pre-stall angles is threatened by forming a laminar separation bubble at the trough section of the tubercle wing; consequently, the flight endurance and range are reduced. In the present study, the idea of passive flow control is introduced by using the distribution of static roughness elements on a full-span wing with a sinusoidal leading edge. Initially, the effect of roughness element length, height, and its location are studied at a pre-stall angle (16-degree). Their effect on the laminar separation bubble and vortex shedding formed behind the wing are also investigated. The Reynolds number is assumed to be equal to 1.4×105 which is in the range of critical Reynolds number and matches to the micro aerial vehicles application. An improved hybrid model, improved delay detached eddy simulation IDDES, has been used to model the flow turbulence structure. In the extended transition region at low Reynolds numbers, the roughness bypassed the instability. Consequently, roughening the surface of the aerofoil increased the boundary layer’s flow momentum, making it more resistible to adverse pressure gradients. By suppressing the bubble, the static roughness element led to pre-stall flow control, which saw an increase in lift coefficient, Cl, and a decrease in drag coefficient, Cd. The results have been demonstrated that the aerodynamic performance,  cl/cd, has been improved approximately 22.7%, 38%, and 45% for α=16°, α=12°, and α=8°, respectively. The optimal arrangement of static roughness elements could decline the size of the vortices and strengthen the cores associated with them. This claim can be interpreted with the vortex shedding frequency.]]></description>
      <pubDate>Fri, 30 Sep 2022 14:27:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/1992973</guid>
    </item>
    <item>
      <title>Measurements of Laminar Flame Velocity and Markstein Length for Standard Gasoline and a Corresponding Reference Fuel Mixture (PRF87)</title>
      <link>https://trid.trb.org/View/1813013</link>
      <description><![CDATA[An experimental and numerical investigation of commercial Gasoline (octane number = 90) with a reference fuel (PRF87) were accomplished. Laminar Flame Velocities and Markstein Numbers of these fuel air mixtures were investigated and compared with each other and with numerical results. PRF87 is presented as a reference fuel for Gasoline defined as 87 percent Iso-Octane and 13 percent N-Heptane by volume at ambient conditions. Spherical flames of Gasoline- and PRF87-Air-Mixtures at initial temperature of 373 K, initial pressure range from 10 bar to 25 bar and equivalence ratios from ϕ = 0.7 to ϕ = 1.2 were experimentally investigated using the Constant Volume Bomb Method.]]></description>
      <pubDate>Mon, 26 Sep 2022 09:12:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1813013</guid>
    </item>
    <item>
      <title>Internal laminar flow effect on the nonlinear dynamic response of marine risers under uniform ocean current</title>
      <link>https://trid.trb.org/View/1986310</link>
      <description><![CDATA[Under the actual marine environment, slender risers suffer from external ocean current and internal flowing fluid. When the viscosity of internal fluid is included, the riser’s nonlinear dynamic response is worthy of extra concern. This paper adopts a force-decomposition model to simulate VIV hydrodynamic forces, the embroil force, relative inertia force and Coriolis force induced by internal flow are included in the motion equation of marine riser. The internal fluid viscosity in essence affects the relative inertia force and Coriolis force, and its effect has to be considered. The comparable ideal flow with Ui = Ui,max/2 brings the dynamic response closer to the laminar flow case than that with Ui = Ui,max, while Ui = Ui,max/2 underestimates the fatigue damage with internal laminar flow. Generally, the internal laminar flow effect on structural cumulative fatigue damage is more significant than that on dynamic response.]]></description>
      <pubDate>Wed, 24 Aug 2022 15:02:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1986310</guid>
    </item>
    <item>
      <title>Aerospace Technology Demonstration: BLADE, the Flagship Laminar Flow Project within the Clean Sky Programme</title>
      <link>https://trid.trb.org/View/1835913</link>
      <description><![CDATA[In the year 2000 the Advisory Council for Aeronautics Research in Europe (ACARE) was established in order to provide research and policy guidance to the European Commission. “Flightpath 2050” was published in 2011 to provide a long term frame for collaborative technology research, soon followed by a “Strategic Agenda For Research and Innovation”. This agenda has been successful in providing a common and coherent reference for the 27 member states of the European Union, and others, to guide future actions in private and public research programs in order to meet societal and market needs. In June 2017 an update to the agenda was published at the Paris airshow, to reflect the rapid progress made in aviation technology and to respond to multiplicity of changed circumstances which the agenda must address. The Clean Sky Joint Technology Initiative is a key means of delivering the Strategic Research and Innovation Agenda, and it is the principal pre-competitive research and technology program in Europe. The Clean Sky program has been a public/private investment of 1.6€B by 600 partners over the period 2009 to 2017, which is now coming to a conclusion. It comprised six sub-programs working on civil technology demonstrations. This paper presents the progress made on the Smart Fixed Wing Aircraft sub-program, notably on the BLADE laminar flow technology demonstrator. A commentary is given on the means of technology demonstrations that were employed during the eight years of the program, as the various technology readiness levels have been achieved. A short video is presented highlighting the physical progress on BLADE before its planned first flight in late 2017. The lecture concludes with a short discussion of the merits and challenges associated with the physical demonstration of aviation technology, notably as digitalization is more and more a driver in the industry.]]></description>
      <pubDate>Sun, 23 Jan 2022 16:51:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/1835913</guid>
    </item>
    <item>
      <title>Laminar-to-turbulent flame transition and cycle-to-cycle variations in large eddy simulation of spark-ignition engines</title>
      <link>https://trid.trb.org/View/1866130</link>
      <description><![CDATA[This paper investigates the effect of laminar-to-turbulent flame transition modeling on the prediction of cycle-to-cycle variations (CCVs) in large eddy simulation (LES) of spark-ignition (SI) engines. A laminar-to-turbulent flame transition model that describes the non-equilibrium sub-filter flame speed evolution during an early stage of flame kernel growth is developed. In the present model, the flame transition is characterized by the flame kernel size at which the flame transition ends, defined here as the flame transition scale. The proposed model captures the effects that variations in a turbulent flow field have on the evolution of early-stage burning rates, through variations in the flame transition scale. The proposed flame transition model is combined with the front propagation formulation (FPF) method and a spark-ignition model to predict CCVs in a gasoline direct injection SI engine. It is found that multi-cycle LES with the proposed flame transition model reproduces experimentally-observed CCVs satisfactorily. When the transition model is not considered or when variations in the transition process are neglected, CCVs are significantly under-predicted for the case considered here. These results indicate the importance of modeling the laminar-to-turbulent flame transition and the effect of turbulence on the transition process, when predicting CCVs, under certain engine conditions. The LES results are also used to analyze sources for variations in the flame transition. It is found, for the present engine case, that the most important source is the cycle-to-cycle variation in the turbulence dissipation rate, which is used to measure the strength of turbulence in the proposed model, near a spark plug. The large-scale velocity field and the variations of the laminar flame speed due to the mixture composition and thermal stratification are also found to be important factors to contribute to the variations in the flame transition.]]></description>
      <pubDate>Mon, 27 Sep 2021 09:45:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/1866130</guid>
    </item>
    <item>
      <title>Numerical Investigation of Effects of G-Jitter on Buoyant Laminar Diffusion
			Flame</title>
      <link>https://trid.trb.org/View/1754777</link>
      <description><![CDATA[Numerical prediction of a confined, co-flowing, laminar jet diffusion flame has been investigated under sinusoidal “g-jitter” to describe the flame structure; this type of flame-body force interaction is typical of a microgravity environment such as in the spacecraft. The authors introduced g-jitter in the direction orthogonal to the fuel and air inflow. The authors show that the lower frequencies (0.1-0.5 Hz) of sinusoidal g-jitter significantly affected the flame geometry and behavior. The majority of the flame structure was found to oscillate directly in response to the imposed g-jitter. It has also been observed that nonlinearity in the response behaviors is more prominent in the reaction zone of the flame.]]></description>
      <pubDate>Mon, 06 Sep 2021 16:55:28 GMT</pubDate>
      <guid>https://trid.trb.org/View/1754777</guid>
    </item>
    <item>
      <title>Analytical modelling of laminar drag and freestream turbulence eddies on droplet breakup criterion for internal combustion engines</title>
      <link>https://trid.trb.org/View/1849031</link>
      <description><![CDATA[The paper presents novel analytical droplet breakup criteria, on Weber number (We)-relative turbulence intensity and We-Ohnesorge (Oh) representations, based on the critical Weber number. The We-Oh analytical criterion stressed the importance of turbulence effects on We-Oh breakup criterion at high We-Oh applications. In developing the analytical models the energy criterion for a disturbed parent droplet to disintegrate and the dual-timescale for turbulent shear in droplet dispersion were considered. The present model has an advantage over to two popular droplet breakup criterion models (Pilch-Erdman and Kolev) because the present model has the ability to support a parametric investigation of droplet breakup characteristics in turbulent flow fields. The Weber-relative turbulence intensity and We-Oh analytical breakup criteria are in good agreement with published experimental data. It is envisaged that the analytical model will be incorporated into larger CFD codes for spray simulation. The continuous research in this important area will present the next generation fuel injectors for improved fuel economy of internal combustion engines, especially high-pressure direct injection engines. The model has the potential to be applied in other natural and engineering systems.]]></description>
      <pubDate>Tue, 15 Jun 2021 12:32:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/1849031</guid>
    </item>
    <item>
      <title>Hydraulic Analysis of a Sloped Trapezoidal Non-cavity Drain Improved by a Pipe Drainage</title>
      <link>https://trid.trb.org/View/1838640</link>
      <description><![CDATA[Non-cavity drains usually have rectangular or trapezoidal profile in cross-section, hydraulic analysis of which is developed. Trapezoidal cross-sections in non-cavity drains facilitates their higher water absorption capacity at approximately the same level of water drainage capacity in comparison to pipe draining system. The water drainage capacity of a non-cavity drain can be improved by installing a pipe drain inside a non-cavity one. However, no hydraulic analysis of such combined drain has been developed. It is assumed that motion of water in both non-cavity part of a drain and pipe one changes gradually. In non-cavity part of the drain, transient flow takes place and it is turbulent in pipe one. Laminar flow is observed in non-cavity and pipe parts of the drain only near the source and has almost no influence on pressure losses lengthwise along the drain. There are obtained calculation dependencies to determine specific afflux to every part of the drain as well as the depth (head in the pipe part of the drain) at the source of drainage and at the section of maximum depth. This was achieved by solving a system of two equations describing the flow of water in non-cavity and pipe parts of the drain.]]></description>
      <pubDate>Mon, 03 May 2021 09:22:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/1838640</guid>
    </item>
    <item>
      <title>A semi-empirical laminar-to-turbulent flame transition model coupled with G equation for early flame kernel development and combustion in spark-ignition engines</title>
      <link>https://trid.trb.org/View/1763372</link>
      <description><![CDATA[It has been reported that early combustion in a spark-ignition engine determines the subsequent combustion. Also, the early combustion has a very strong correlation with cycle-to-cycle variability, which limits engine operating range. As such, accurate modeling of the early flame development is very important in accurate simulation of spark-ignition engine combustion. During the early flame development, the flame kernel, initiated by spark, grows initially at laminar flame speed. As the kernel grows, the flame surface wrinkles due to surface instability and interacts with the flow turbulence as the flame transitions from laminar to turbulent flame. In this study, a semi-empirical model is proposed to simulate the laminar-to-turbulent flame transition process during early spark-ignition combustion. A hyperbolic tangent function was used to emulate the laminar-to-turbulent flame speed transition process. The proposed transition function was evaluated during early flame kernel development for both Reynolds-averaged Navier–Stokes and large eddy simulation models against combustion analysis data from high-speed optical particle image velocimetry. Difference in Reynolds-averaged Navier–Stokes and large eddy simulation transition function was analyzed and discussed.]]></description>
      <pubDate>Mon, 22 Feb 2021 10:22:28 GMT</pubDate>
      <guid>https://trid.trb.org/View/1763372</guid>
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