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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" />
    <description></description>
    <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>The impact of fuel cell vehicle exhaust grille shape under natural ventilation on hydrogen leakage and diffusion</title>
      <link>https://trid.trb.org/View/2617091</link>
      <description><![CDATA[The rapid progression of hydrogen fuel cell vehicles has brought forth various challenges, primarily the frequent occurrence of hazardous incidents stemming from hydrogen leakage and diffusion. Consequently, there is a growing emphasis on hydrogen safety, leading to the development of stricter standards and regulations to mitigate the associated safety risks. Research on the design of exhaust port structures to facilitate the safe diffusion of hydrogen after leakage in diverse scenarios has become increasingly significant. This study examines the impact of exhaust grille shapes on hydrogen leakage and diffusion phenomena within the hydrogen storage compartment of fuel cell vehicles under natural ventilation conditions. Five distinct porous grille shapes were examined: rectangular, circular, square, rhombic, and hexagonal grilles. Numerical simulations of hydrogen leakage and diffusion within the compartment were conducted using Cradle scFLOW software. The effectiveness of the different grille shapes was assessed using several criteria, including average hydrogen molar fraction, pressure drop (indicative of negative pressure regions), density, and Richardson number. Overall, the rectangular grille exhibited superior performance in facilitating hydrogen venting.]]></description>
      <pubDate>Wed, 03 Dec 2025 16:45:08 GMT</pubDate>
      <guid>https://trid.trb.org/View/2617091</guid>
    </item>
    <item>
      <title>Aerodynamic noise analysis of the skirting board under an ultra-high-speed train based on bidimensional empirical mode decomposition</title>
      <link>https://trid.trb.org/View/2578299</link>
      <description><![CDATA[The grille located in the lower part of the train often forms a grille-cavity structure in the equipment bay’s surface. The issue of flow-induced sound of this structure becomes more significant at high speeds. In this study, we focus on a skirting board with a grille, that is simplified as a grille-cavity structure. We use DDES in combination with modal decomposition, to analyze the fluidization mechanism of the structure. The results indicate that the shear oscillation at the opening of the cavity is more pronounced at ultra-high speed. Moreover, it has been shown that both POD and BEMD can accurately separate and identify coherent structures in the flow field. BEMD has higher accuracy. And the flow is primarily dominated by low-frequency acoustic oscillation. Finally, when we compare three grille configurations (V, ?), we find that the grille’s presence mitigates the cavity’s aerodynamic noise, especially when using a -shaped grille.]]></description>
      <pubDate>Fri, 26 Sep 2025 13:39:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/2578299</guid>
    </item>
    <item>
      <title>The bending vibration characteristics of the hull grillage structure based on back propagation neural network</title>
      <link>https://trid.trb.org/View/2568163</link>
      <description><![CDATA[This study investigates the longitudinal bending vibration characteristics of hull grillage structures through a synergistic approach integrating wave propagation methodology and back propagation neural network. The spring oscillator coupled beam system is established as the equivalent physical model to represent the low-frequency bending vibration behaviour of the grillage structure. The governing equations for this coupled beam system with elastic boundary conditions are systematically derived using the wave propagation approach. Subsequently, the back propagation neural network is developed to predict the natural frequencies of longitudinal bending vibrations, effectively circumventing the requirement for constructing finite element models during preliminary frequency analysis. The bending vibration of the grillage structure is conducted using the proposed equivalent model, with validation performed through comparative analysis with finite element simulations and model experiments. The research further explores the effects of structural parameters on longitudinal bending vibration characteristics. The neural network-based prediction methodology demonstrates significant advantages in rapidly estimating natural frequencies. This integrated approach provides an efficient alternative for preliminary vibration assessment of grillage structures, demonstrating both theoretical validity and practical applicability through comprehensive validation.]]></description>
      <pubDate>Fri, 18 Jul 2025 09:05:42 GMT</pubDate>
      <guid>https://trid.trb.org/View/2568163</guid>
    </item>
    <item>
      <title>Low frequency vibration isolation characteristics and intelligent design method of hull grillage metastructures</title>
      <link>https://trid.trb.org/View/2322919</link>
      <description><![CDATA[In this paper, the wave propagation mechanics theoretical model of hull grillage metastructures with local resonators is established, and the intelligent design method of hull grillage metastructures is proposed based on deep learning. The flexural vibration isolation characteristics of periodic hull grillage structures and the proposed hull grillage metastructures are theoretically studied using the spectral element method. Numerical calculation and experimental tests of the flexural wave vibration transmission of hull grillage metastructures are conducted to validate the proposed theoretical model. In addition, the data set is constructed by using the wave mechanics theoretical model of hull grillage metastructures, and the forward prediction neural network model of vibration transmission characteristics as well as the inverse design neural network model of hull grillage metastructures are established. Results show that compared with periodic hull grillage structures, the proposed hull grillage metastructures possess significant low-frequency flexural wave vibration isolation characteristics which almost completely covers the low-frequency range from 27 Hz to 169 Hz. Both forward prediction and inverse design network models have good performance, which verifies the correctness of the intelligent design method based on deep learning, and provides a new direction for the structural design on demand of low-frequency vibration reduction of ship and offshore structures.]]></description>
      <pubDate>Mon, 11 Mar 2024 16:32:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2322919</guid>
    </item>
    <item>
      <title>Influence analysis of front grille shape on flow field in front cabin of series hybrid electric truck based on large eddy simulation</title>
      <link>https://trid.trb.org/View/2289214</link>
      <description><![CDATA[In view of the influence of front grille design variables on the flow field in the front cabin of series hybrid electric trucks, the cooling system of a certain models simulated calculation. The influence of design variables such as grid shape, spacing and width on the cooling system of series hybrid electric truck engines was studied. The results show that when the front grille is changed to hexagon, vertical strip, horizontal strip, square and diamond, the performance of the cooling system is improved most obviously by the vertical strip grille. Under the condition that the shape and width of the grille remain unchanged, as the grille spacing decreases from 7 mm to 1 mm, the air mass flow rate increases by 5.72%. The width of the grid has little effect on the air mass flow rate of the cooling module.]]></description>
      <pubDate>Thu, 22 Feb 2024 16:14:06 GMT</pubDate>
      <guid>https://trid.trb.org/View/2289214</guid>
    </item>
    <item>
      <title>Intake grille design for an embedded ventilation-and-cooling system in an aircraft</title>
      <link>https://trid.trb.org/View/2010418</link>
      <description><![CDATA[An inlet grille typically needs to be installed at the inlet of the air intake of the ventilation-and-cooling system embedded in airborne electronic equipment to improve pneumatic stealth performance. Here, a typical flying wing model is used as a case study, and a computational fluid dynamics (CFD) simulation is performed. The flow resistance characteristics of the air intake of the opening of the ventilation-and-cooling system on a flat fuselage surface with and without an inlet grille are analyzed at different flow rates and Mach 0.25. The effects of the grille opening shape, diversion angle, thickness, aperture size, and hole shape on the flow resistance characteristics are investigated in detail. The grille is found to effectively guide airflow entry: although the flow resistance at the inlet is increased, the flow resistance at the inlet and outlet of the air intake is significantly reduced. The optimal developments of the outflow and flow resistance characteristics are obtained for a quadrilateral opening. The smaller the diversion angle is, the smoother the airflow entry, and the higher the quality of the internal airflow. The rectification, viscous resistance, and weight exhibit opposing trends with increasing thickness and must be comprehensively considered in designing an optimal scheme. A large-aperture grille ensures good flow patency at low flow rates, whereas a small-aperture grille can reduce flow perturbations and separation at high flow rates by smoothly guiding air into the intake. A grille with round holes has a better spanwise and chordwise balancing effect on the airflow and better flow resistance characteristics than a grille with diamond-shaped holes.]]></description>
      <pubDate>Thu, 27 Oct 2022 13:47:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/2010418</guid>
    </item>
    <item>
      <title>Effect of an Inclined Position on the Aerodynamic Characteristics of Active Grille Shutters</title>
      <link>https://trid.trb.org/View/2004682</link>
      <description><![CDATA[Recently, an aerodynamic theory for active grille shutters (AGS) of road vehicles has been developed that analytically describes the relationship among the flap position, cooling air mass flow, and drag. The experimentally validated theory is based on the assumption of a geometrically simple shutter which is arranged in a straight air duct and is flowed frontally, i.e., perpendicular to the flap plane. In the present work, this theory is extended and it is investigated how an inclined position affects the aerodynamic characteristic of an AGS. The theoretical results are then validated experimentally. Measurements on real vehicles with suitable AGS are used for this purpose. The results show good agreement between the theoretical predictions and experiment. The theoretical and experimental analyses allow conclusions to be drawn about how and under what conditions an inclined position affects the aerodynamic behavior of AGS.]]></description>
      <pubDate>Fri, 19 Aug 2022 09:22:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/2004682</guid>
    </item>
    <item>
      <title>A comparison of geometric imperfection models for collapse analysis of ship-type stiffened plated grillages</title>
      <link>https://trid.trb.org/View/1890974</link>
      <description><![CDATA[The assessment of the buckling and ultimate collapse strength is a mandatory step in the ultimate limit state design of ship structures. The collapse analysis of ship-type stiffened panels under longitudinal compression is highly affected by initial geometric imperfection. Several geometric imperfection models are available in the literature. Broadly speaking, they can be categorised into deterministic and probabilistic approaches. The deterministic approach describes the initial deflection field with a presumed geometric shape and a characteristic maximum distortion magnitude. Several geometric deflection shapes are commonly adopted, including hungry-horse (HH) mode, Admiralty Research Establishment (ARE) mode and critical buckling (CM) mode. Each of these deflection mode shapes is used in conjunction with a characteristic maximum distortion magnitude. Except otherwise specified, an average-level magnitude is usually applied. By contrast, the probabilistic approach evaluates the initial geometric imperfection as a random field, generated based on the prescribed statistics. A comparative study is presented in this study in the light of analysing the uncertainty in ultimate compressive strength of stiffened plated grillages induced by different modelling of geometric imperfection. In addition, the influence of relative deflection in the adjacent panels is analysed. Recommendations for choosing an imperfection model for buckling analysis of ship-type stiffened plated structures are reported.]]></description>
      <pubDate>Tue, 30 Nov 2021 10:23:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/1890974</guid>
    </item>
    <item>
      <title>Fuel Minimization of the Electric Engine Cooling System With Active Grille Shutter by Iterative Quadratic Programming</title>
      <link>https://trid.trb.org/View/1694064</link>
      <description><![CDATA[The electric engine cooling system with the active grille shutter requires intelligent and predictive control to reach its full benefits on fuel economy and thermal management. Conventional control methods regulate the coolant temperature to a fixed value but do not directly minimize the vehicle's fuel/energy consumption. By contrast, the authors design a fuel minimization controller through solving constraint nonlinear optimization problems, whose cost function is the total fuel consumption and constraints are the vehicle's physical limits. To achieve high computational efficiency and sufficient accuracy, the optimization problem is solved by iterative convex quadratic programming and quasilinearization. The advantages of the proposed control method on both fuel economy and engine thermal management are demonstrated by simulations.]]></description>
      <pubDate>Tue, 23 Jun 2020 12:29:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/1694064</guid>
    </item>
    <item>
      <title>Impact of Active-Grille Shutter Position on Vehicle Air-Conditioning System Performance and Energy Consumption in Real World Conditions</title>
      <link>https://trid.trb.org/View/1701962</link>
      <description><![CDATA[Active grille shutter (AGS) in a vehicle provides aerodynamic benefit at high vehicle speed by closing the front-end grille opening. At the same time this causes lesser air flow through the cooling module which includes the condenser. This results in higher refrigerant pressure at the compressor outlet. Higher head pressure causes the compressor to work more, thereby possibly negating the aerodynamic benefits towards vehicle power consumption. This paper uses a numerical method to quantify the compressor power consumed in different scenarios and assesses the impact of AGS closure on total vehicle energy consumption. The goal is to analyze the trade-off between the aerodynamic performance and the compressor power consumption at high vehicle speeds and mid-ambient conditions. These so called real world conditions represent highway driving at mid-ambient temperatures where the air-conditioning (AC) load is not heavy. AC system is modeled using 1D methodology and its performance simulated at system level. Net power consumed by the vehicle is computed for different scenarios using a robust comparison methodology. System model is validated against vehicle drive cell test data. Tests are conducted on a mid-size sport utility vehicle (SUV) equipped with a full face AGS. Simulations are then performed with the validated model using a Design for Six Sigma (DFSS) methodology to compute net power consumed by the vehicle by varying the blower setting, vehicle speed and ambient temperature. This paper provides guidelines regarding when to have the AGS closed or open for different noise factors considered.       ]]></description>
      <pubDate>Tue, 26 May 2020 10:20:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/1701962</guid>
    </item>
    <item>
      <title>Active Grille Shutters Control and Benefits in Medium to Large SUV: A System Engineering Approach</title>
      <link>https://trid.trb.org/View/1701961</link>
      <description><![CDATA[Whilst the primary function of the active grille shutters is to reduce the aerodynamic drag of the car, there are some secondary benefits like improving the warm up time of engine and also retaining engine heat when parked.         In turbocharged IC engines the air is compressed (heated) in the turbo and then cooled by a low temperature cooling system before going into the engine. When the air intake temperature exceeds a threshold value, the engine efficiency falls - this drives the need for the cooling airflow across the radiator in normal operation. Airflow is also required to manage the convective heat transfer across various components in the engine bay for its lifetime thermal durability. Grill shutters can also influence the aerodynamic lift balance thus impacting the vehicle dynamics at high speed. The vehicle HVAC system also relies on the condenser in the front heat exchanger pack disposing the waste heat off in the most efficient way. These requirements of maintaining optimal engine intake charge air temperature, managing condenser heat load, engine bay heat and aerodynamic lift balance pose contradicting challenges in finding the optimal energy balance within the control strategy.         This paper talks about the system engineering approach to the control strategy development of active grille shutters. A combination of 0D (Matlab-Simulink), 1D (GT Suite) and 3D CAE (Dassault Systemes Powerflow) tools were used to define the optimal control strategy. This paper also shows the testing & validation of the thermal results of a Jaguar Land Rover vehicle fitted with active grille shutters, with control strategy optimized to full scale wind tunnel, in a chassis dynamometer environment. The influence of the facility on the test results provides a unique insight into the relation between the facility fan (air handling unit) dimension and the charge air temperature of various different homologation chassis dynamometer emission facilities.       ]]></description>
      <pubDate>Tue, 26 May 2020 10:20:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/1701961</guid>
    </item>
    <item>
      <title>Developing a Theory for Active Grille Shutter Aerodynamics-Part 2: Effect of Flap Thickness and Shape</title>
      <link>https://trid.trb.org/View/1704429</link>
      <description><![CDATA[A recently developed theory for the description of the aerodynamic behaviour of active grille shutters is extended by the influence of the thickness of the cooling air flaps. The analysis of the resulting equations shows that the thickness of the flaps has no influence on the characteristic curve of an active grille shutter. To validate the theoretical results, wind tunnel measurements are carried out on a vehicle with an active grille shutter, and both the thickness and the shape of the flaps are specifically modified. The experimental results confirm the analytical results and show that not the thickness but the shape of the cooling air flaps is the decisive influencing factor. The experiments further show that aerodynamically unfavourable flap shapes, even with small relative thicknesses, lead to a significant change in the characteristic curve and to significant losses in cooling airflow with fully opened flaps. In contrast to this, with flow-optimized flap shapes, relative thicknesses of up to 30% of the flap length are possible without changing the characteristic curves or significantly reducing the cooling airflow rate.       ]]></description>
      <pubDate>Tue, 26 May 2020 10:16:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/1704429</guid>
    </item>
    <item>
      <title>Design Optimization of Engine Cooling Unit Packaging for Commercial Vehicle</title>
      <link>https://trid.trb.org/View/1561895</link>
      <description><![CDATA[An engine cooling system is required to maintain stable operating temperature for the engine and prevent it from overheating. Thermal distortion of engine parts can take place if proper cooling is not maintained and engine may loss efficiency. One of the major problem in this domain is to incorporate separate cooling systems for the different variants of engines (different power rating). A single optimized cooling unit is desired to manage the entire range of engine rated power. The factors that affect the cooling system are front end grill opening area, air recirculation, location of snorkel inlet, radiator core size, which need to be tuned to get appropriate results. The above parameters are tuned to obtain appropriate results using the Computational Fluid Dynamics (CFD) simulations. In the next stage, on road cooling trials are performed and real time data is collected. A correlation is established between physical trials and CFD results which may be helpful in future projects as well.         From experimental results we observed a sufficient temperature drop in both heat exchangers (radiator and intercooler) and efficient heat rejection is made possible through the heat exchanger to maintain proper functioning temperature of engine. All trials are performed at extreme conditions i.e. full throttle, 100% load and high gradient conditions, to obtain maximum possible heat rejection to coolant fluid.       ]]></description>
      <pubDate>Mon, 03 Feb 2020 07:56:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/1561895</guid>
    </item>
    <item>
      <title>Aerodynamic Investigation of Cooling Drag of a Production Pickup Truck Part 1: Test Results</title>
      <link>https://trid.trb.org/View/1561107</link>
      <description><![CDATA[The airflow that enters the front grille of a ground vehicle for the purpose of component cooling has a significant effect on aerodynamic drag. This drag component is commonly referred to as cooling drag, which denotes the difference in drag measured between open grille and closed grille conditions. When the front grille is closed, the airflow that would have entered the front grille is redirected around the body. This airflow is commonly referred to as cooling interference airflow. Consequently, cooling interference airflow can lead to differences in vehicle component drag; this component of cooling drag is known as cooling interference drag. One mechanism that has been commonly utilized to directly influence the cooling drag, by reducing the engine airflow, is active grille shutters (AGS). For certain driving conditions, the AGS system can restrict airflow from passing through the heat exchangers, which significantly reduces cooling drag. The difference in drag between the AGS vanes being open and closed is referred to as AGS drag. Another vehicle component that influences the cooling drag is chin spoilers. Chin spoilers are components that lie within cooling interference airflow paths for many vehicles and can be used/designed to affect cooling drag. This study focuses on the influence of the chin spoiler on cooling and AGS drag of a production-level F-150 in a wind tunnel test environment. The chin spoiler variables tested were height and curvature (sweep). All experiments were conducted in both stationary and moving ground wind tunnel conditions at 80 MPH between yaw angles of ±7°. In addition to overall vehicle drag coefficients, surface pressures at discrete locations and cooling pack airflow rates were measured to provide better insight into the internal and external airflow behavior. Ground and yaw conditions were shown to heavily influence chin spoiler design. Cooling and AGS drag were also strongly influenced by chin spoiler face height at 0° yaw; at higher angles of yaw this influence was lessened but was still present. Chin spoiler sweep was shown to have a significantly lesser (though non-negligible) impact than chin spoiler face height on all metrics in all conditions.       ]]></description>
      <pubDate>Mon, 23 Dec 2019 07:46:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1561107</guid>
    </item>
    <item>
      <title>Efficient Two-Way Shear Grillage Model Solution for Bridge RC Four-Pile Caps under Wall Loading</title>
      <link>https://trid.trb.org/View/1606329</link>
      <description><![CDATA[Reinforced concrete four-pile caps under wall loading occur in heavily loaded foundations in bridge construction. The failure mode of shear across the full width of the cap may occur in these deep structural elements. A statically determinate two-way grillage model, comprising orthogonal deep beam grillage elements obeying a predetermined test observing deflection pattern and boundary conditions, is established to solve the structure’s shear capacity. The model gives more accurate and faster solutions than the traditional strut-and-tie method and commercial nonlinear numerical modeling. A key step to solving the model is a linear constitutive (load-deflection) relationship developed for the grillage elements. The grillage model is verified against laboratory experiments for nine pile caps at the University of Southampton (UoS) with the results of a numerical modeling parametric study. A Visual Basic Userform-based design software is developed, incorporating the model and enabling engineers to obtain the shear capacity, full-field reinforcement stress distribution, and cap deflections within seconds.]]></description>
      <pubDate>Tue, 28 May 2019 16:52:59 GMT</pubDate>
      <guid>https://trid.trb.org/View/1606329</guid>
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