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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>Relationship between Mass Burnt Fraction 50% Crank Angle and Low-Frequency Components in Cylinder Pressure When Ignition Timing Was Delayed</title>
      <link>https://trid.trb.org/View/2684136</link>
      <description><![CDATA[When the ignition timing was delayed for the purpose of engine protection or early activation of the exhaust catalyst, cylinder pressure with two peaks might occur. A correlation between the crank angle at 50% mass burnt fraction and the amplitude of the low-order sine wave frequency component (bₖ) was also observed in the cylinder pressure with two peaks. In addition, bₖ might become negative. It is caused by the high cylinder pressure in the calculation section where the part of the bₖ calculation equation is negative.]]></description>
      <pubDate>Tue, 23 Jun 2026 13:53:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2684136</guid>
    </item>
    <item>
      <title>On-board data reduction techniques for in-cylinder pressure transmission in connected vehicle applications</title>
      <link>https://trid.trb.org/View/2679092</link>
      <description><![CDATA[This study explores on-board data reduction techniques for efficient over-the-air transmission of in-cylinder pressure data in connected vehicles. Besides its significance for combustion diagnostics, the in-cylinder pressure signal conveys valuable information about the engine operation that could enhance fleet monitoring and management. However, the high sampling frequency of this signal leads to substantial data volume. In this work, singular value decomposition (SVD) and QR factorization with column pivoting were explored for data reduction in a vehicle equipped with an in-cylinder pressure sensor, and over-the-air transmission of the reduced data to a cloud server was implemented. This work establishes the feasibility of these techniques for in-vehicle applications and the results indicate accurate signal reconstruction with a significant 95% and 97% reduction in data size for SVD and SVD + QR, respectively. The findings suggest that both methods are appropriate for in-cylinder pressure data transmission, although the SVD + QR technique might be preferred in situations where on-board diagnostics solutions are required.]]></description>
      <pubDate>Thu, 11 Jun 2026 09:33:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/2679092</guid>
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    <item>
      <title>Upstream Oxygen Sensor Signal Improvement Using the DFSS and Virtual Validation Approach</title>
      <link>https://trid.trb.org/View/2692151</link>
      <description><![CDATA[Combustion stability and emission control remain key challenges for gasoline engines, requiring robust oxygen sensing strategies. The primary function of the upstream exhaust oxygen sensor is to detect the oxygen concentration in exhaust gas for accurate air–fuel ratio control. However, poor signal visibility from individual cylinders across engine speeds can lead to improper combustion prediction and reduced engine efficiency. This work applies a Design for Six Sigma (DFSS) approach to optimize the upstream oxygen sensor configuration in a 2.0 L four-stroke gasoline engine. Conventionally, sensor placement is completed by iterative testing and calibration, which is both time-consuming and cost intensive. The DFSS framework uses input, output, control, and noise factors. Exhaust gas mass flow rate from engine cylinders at different speeds is treated as the input, while the detected oxygen mass fraction is the output. Design parameters such as pipe length, pipe diameter, sensor orientation, insertion depth, and location are considered control factors. Sensor element position and ambient temperature serve as noise factors, as they cannot be controlled directly by the engineer. The analysis is performed using three-dimensional computational fluid dynamics (CFD) and confirmed through Design of Experiments (DoE) simulations. The optimized configuration achieved improved sensor signal stability and cylinder visibility, enabling more reliable combustion control. This structured approach demonstrates how virtual analysis combined with DFSS principles can guide robust oxygen sensor placement strategies, reducing validation effort while enhancing engine efficiency and emissions performance.]]></description>
      <pubDate>Thu, 28 May 2026 17:09:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692151</guid>
    </item>
    <item>
      <title>Optical diagnostics of fuel induced soot formation: color ratio pyrometry of in-cylinder soot in a DISI engine</title>
      <link>https://trid.trb.org/View/2685702</link>
      <description><![CDATA[The rapid diversification of gasoline-derived fuels demands a deep understanding of in-cylinder soot formation mechanisms, especially under the transient and low-temperature conditions characteristic of cold-start operation. Reliable, high-resolution diagnostics enable spatially resolved investigation of soot formation and allow a detailed analysis of mixture formation and soot-generation processes. This study evaluates Color-Ratio-Pyrometry (CRP) as an optical soot-measurement technique in a state of the art direct-injection spark-ignition (DI-SI) engine operating at steady-state load points for both cold-start (engine coolant temperature 20 °C) and warm-engine (95 °C) conditions. Three fuel families were examined: (i) a worst-case low-volatility gasoline (LV-G) representing a high-soot baseline, (ii) a low-soot, alkylate gasoline (ALK-G), and (iii) binary blends of LV-G or ALK-G with ethanol or methanol in mass fractions of up to 30% CRP signals were acquired using high speed imaging through an optical access at cylinder one, synchronized with cylinder pressure and heat release data to validate the temperature estimation. The results of soot volume fractions are compared to particle concentration measurements in the raw exhaust gas using an electric mobility particle spectrometer.]]></description>
      <pubDate>Wed, 29 Apr 2026 17:05:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/2685702</guid>
    </item>
    <item>
      <title>Experimental study on the effects of two-stage direct water injection in-cylinder on combustion characteristics of high compression ratio lean-burn engine</title>
      <link>https://trid.trb.org/View/2663665</link>
      <description><![CDATA[Addressing the global energy crisis and environmental challenges, the development of efficient and clean internal combustion engine technology has become a critical research focus. A two-stage direct water injection in-cylinder (DWI) strategy was proposed to address the issues of knocking and combustion stability in high compression ratio (CR = 17) lean burn gasoline engines. The effects of no injection, single and two-stage DWI on the engine under stoichiometric (λ = 1.0) and lean-burn (λ = 1.4) conditions were also investigated experimentally. The experimental results show that under stoichiometric combustion conditions, the two-stage water injection can significantly suppress knocking by optimizing the second-stage water injection timing (60°CA BTDC), reducing the knocking intensity (KI) to 0.17 bar. Under lean-burn, the single water injection strategy demonstrates a better knocking suppression effect. The two-stage water injection strategy effectively controls the coefficient of variation of indicated mean effective pressure (COVIMEP) below 2.57%, which is 0.4% lower than the single water injection strategy. In terms of thermal efficiency, the lean-burn combined with the water injection strategy increases the indicated thermal efficiency to 43.53%. Regarding emission characteristics, CO₂ emissions are mainly dominated by the λ value, and the water injection strategy has a minor impact. The water injection technology can significantly reduce NOₓ emissions. Under stoichiometric combustion conditions, two-stage water injection reduces NOₓ emissions by 45.4% (to 1305.87 ppm), and under lean-burn conditions, it further reduces them to 454.17 ppm. Notably, single water injection shows the best NOₓ control effect under lean-burn conditions, with the emission maintained at around 300 ppm.]]></description>
      <pubDate>Mon, 27 Apr 2026 16:17:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663665</guid>
    </item>
    <item>
      <title>Effects of intake areas and shapes on the flow field of elliptical rotary engines at different speeds</title>
      <link>https://trid.trb.org/View/2663662</link>
      <description><![CDATA[Due to the special structure, the flow field of elliptical rotor engines (ERE) shows several flow direction reversals, which is important for ERE working. In this research, a three-dimensional simulation model of ERE was developed using the CONVERGE. The turbulence model was validated through Particle Image Velocimetry (PIV) experiments, allowing for an analysis of the scavenging process. Additionally, the study explored the impact of rotational speed, intake port areas and intake shapes on the flow field within the combustion chamber. The findings reveal that complex flows with multiple directional changes is occurred during the exchange process. With the increase of rotational speed, the volumetric efficiency of ERE increases and then decreases, and the highest point occurs at 4000 rpm. The peak of TKE occurs in the early stage of intake stroke at low rotational speeds, and occurs in the high rotational speed when the port is directly aligned with the recess. Variations in the shape of the intake port change the distribution of gas flowing, with regular trapezoidal and elliptical ports enhancing the swirling intensity in the bottom of the chamber. The elliptical intake port exhibits higher flow intensity at low speeds, while the regular trapezoidal intake port has higher flow strength at high speeds. An increase in the port area intensifies the swirl at the bottom of the chamber while simultaneously reducing the peak TKE. The in-cylinder flow of an elliptical rotor engine can be improved by using an appropriate intake shape and intake area, which improves its working process.]]></description>
      <pubDate>Mon, 27 Apr 2026 15:00:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663662</guid>
    </item>
    <item>
      <title>Wheel cylinder pressure estimation for hydraulic braking system based on multi-model fusion of apply valve characteristic</title>
      <link>https://trid.trb.org/View/2691744</link>
      <description><![CDATA[Estimating the wheel cylinder pressure accurately with the hydraulic model of the apply valve is quite challenging due to the narrow linear control range of the pulse-width-modulation (PWM) apply valve in the hydraulic braking system. Considering this characteristic of the apply valve, this paper proposes a wheel cylinder pressure estimation method based on a fusion model through combing the linear and the switching hydraulic models. Firstly, the key parameters and the linear range of the apply valve are determined through experimental measurements, as well as the linear and the switching hydraulic models of the apply valve are established. Secondly, these two models are integrated using fuzzy rules to create a high-precision fusion hydraulic model that can accurately calculate the flow rate of the apply valve. Then, the wheel cylinder pressure is estimated by the measured P-V characteristic. Finally, the wheel cylinder pressure estimation-based pressure closed-loop test is carried out by the hardware-in-the-loop bench, and results indicate that the proposed method can significantly improve the dynamic accuracy of the hydraulic model-based wheel cylinder pressure estimation, with the estimation error below 0.5 MPa.]]></description>
      <pubDate>Thu, 23 Apr 2026 09:39:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/2691744</guid>
    </item>
    <item>
      <title>Modifications in the wake of a transversely oscillating circular cylinder by additional rotational motions</title>
      <link>https://trid.trb.org/View/2653086</link>
      <description><![CDATA[Modifications in the wake of a transversely oscillating circular cylinder by additional oscillatory or uniform rotational motions are presented. Wake of a purely translating (Ty) cylinder is characterized by: Lock-in region (matching of vortex shedding and excitation frequencies), symmetric vortex shedding, high drag, low fluctuations in the moment with zero average and dependence of energy transfer on excitation amplitude & frequency. Additional oscillatory rotation (Rₒ) causes: early (at lower excitation frequency) entry and exit of Lock-in, increment in drag, amplified fluctuations in the moment with zero average, dependence of energy transfer on a competition between viscous damping & flow inertia and quasi-periodic flow. Additional uniform rotation (Rᵤ) causes: early exit of Lock-in, loss of symmetric vortex shedding with negative average lift, decrement in drag, low fluctuations in the moment with negative average and energy transfer dictated by flow inertia. It may be proposed that Ty+Rₒ has higher potential to modify the wake than Ty+Rᵤ. This study predicts the wake characteristics of the corresponding Vortex-Induced Vibration (VIV).]]></description>
      <pubDate>Wed, 08 Apr 2026 13:57:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2653086</guid>
    </item>
    <item>
      <title>Analytical Control of the Mass of Injected Fuel into Diesel Engine Cylinder</title>
      <link>https://trid.trb.org/View/2676066</link>
      <description><![CDATA[In real operating conditions, the engine indicator diagram is the most common source of data for analyzing its current technical condition. Despite this, it is not possible to determine all diagnostic parameters directly from it, for example, the mass of fuel injected into the cylinder. To determine the fuel supply, it is possible to use the calculation of heat release in the cylinder or by solving a system of differential equations describing the working process in the cylinder. However, in those cases, the approximate value of the average temperature of the cylinder walls is unknown, as well as which of the empirical formulas for calculating the heat transfer from the gases to the cylinder walls should be used. Therefore, an additional method for calculating the mass of fuel injected into the cylinder was developed, in which the actual working process, under certain assumptions, was represented by a calculated cycle with isochoric and isobaric sections of fuel combustion. As a result, two systems of algebraic equations were compiled, the solutions of which can be used to find the mass of injected fuel. During the research, the process of solving equations was modernized, which allowed for a significant increase in accuracy.]]></description>
      <pubDate>Wed, 25 Mar 2026 11:44:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/2676066</guid>
    </item>
    <item>
      <title>Far-field aerodynamic noise reduction of a circular cylinder by longitudinal grooves: Effect of groove profile, size ratio and number</title>
      <link>https://trid.trb.org/View/2676129</link>
      <description><![CDATA[This paper presents an experimental investigation into the aerodynamic noise characteristics of grooved circular cylinders conducted in an acoustic wind tunnel. It investigates the influence of groove profile—specifically, triangular, circular, and rectangular—as well as groove number and size on the far-field noise generated by the flow. Aerodynamic noise was measured employing far-field microphone arrays. The acoustic results demonstrate that, at a wind speed of 30 m/s, the maximum SPL at the far-field noise monitoring point is reduced by up to 10 dB compared to a smooth circular cylinder when the groove profile is triangular, with 30 grooves and a groove size of h/D = 0.01. At an inlet velocity of 40 m/s, with a circular groove profile, 30 grooves, and a groove size of h/D = 0.01, the far-field noise reduction can reach up to 14 dB relative to the baseline model. Flow characteristics were investigated using particle image velocimetry (PIV) techniques. The PIV results indicate that the noise reduction in the far field is predominantly attributed to the reduced vortex intensity in the flow field. The investigation into the far-field noise characteristics of partially grooved cylinders offers preliminary evidence that the groove structure delays boundary-layer separation around the cylinder, thereby contributing to a reduction in far-field noise. These findings can provide valuable insights for the development of noise control strategies in various engineering applications.]]></description>
      <pubDate>Wed, 25 Mar 2026 11:44:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/2676129</guid>
    </item>
    <item>
      <title>IDDES simulation of side-by-side cylinder flow with different turbulence intensities at subcritical Reynolds number</title>
      <link>https://trid.trb.org/View/2634147</link>
      <description><![CDATA[In the present study, the OpenFOAM single-flow solver based on the Improved Delayed Detached Eddy Simulation (IDDES) is used to simulate the side-by-side cylinder flow at a subcritical Reynolds number  under different turbulence intensities () and space ratios (, where  is the center-to-center distance between cylinders and  is the diameter). We analyzed the time-averaged flow characteristics, transient flow characteristics, and hydrodynamic parameter distributions of the side-by-side cylinder flow under different space ratios and turbulence intensities. Results show that (1) When , the increase in turbulence intensity changes the size of the time-averaged wake region and the length of the shear layer behind the cylinders, but has no effect on the shape of the distribution contour. (2) As the I increases, the peak velocity position in the gap side between the two cylinders moves away from the cylinder surfaces. The curvature of the velocity distribution curve decreases, and the curve tends toward symmetry about the x-axis. (3) The increase in turbulence intensity changes the law of variation in the time history of drag coefficients and lift coefficients for side-by-side cylinders, and I is one of the main reasons for the random flip-flop of gap flow, resulting in bistable characteristics. (4) The increase in I changes the magnitude and distribution pattern of the time and space averaged pressure coefficient on the cylinder surface, and delays flow separation on both sides of the side-by-side cylinders. However, it does not affect the time-averaged pressure stagnation angle.]]></description>
      <pubDate>Tue, 10 Mar 2026 09:55:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/2634147</guid>
    </item>
    <item>
      <title>Flow-induced vibrations of a wake cylinder at a low mass-damping ratio</title>
      <link>https://trid.trb.org/View/2660750</link>
      <description><![CDATA[This study experimentally investigates flow-induced vibrations of an elastically mounted cylinder (diameter D) in a wake, at a low mass-damping ratio of m∗ζ = 0.163. This work focuses on the influence of reduced velocity Ur (= 1.51 − 16.82), streamwise spacing ratio L/D (= 2.0 − 6.0), and transverse spacing ratio T/D (= 0 − 3.0) between the cylinders on vibration responses, frequency responses, forces, added mass, and phase lag between lift and displacement. Five distinct vibration branches − initial branch (IB), upper branch (UB), lower branch (LB), desynchronized branch (DB), and galloping branch (GB) − are identified and discussed with respect to T/D, L/D, and Ur space. The cylinder undergoes combined vortex-induced vibration (VIV) and galloping for T/D < 0.37 − 0.75 (depending on L/D). At 0.37 − 0.75 <T/D < 1.75, where two wakes of different sizes are formed, galloping is absent, leaving strong VIV only in the vibrations. The added mass associated with the cylinder oscillation declines progressively from IB to GB with a rapid decrease in IB. The added mass is positive for IB and UB, but negative for LB and GB. The connection between vibration responses and flow structures around fixed cylinders is established.]]></description>
      <pubDate>Wed, 11 Feb 2026 15:10:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2660750</guid>
    </item>
    <item>
      <title>Experimental and numerical study of a pitching airfoil interacting with the vortical wake of an upstream cylinder</title>
      <link>https://trid.trb.org/View/2660743</link>
      <description><![CDATA[The turbulence properties of the upstream flow have a significant impact on the aerodynamic behavior of an airfoil in various applications. Two key parameters in the upstream flow are the presence of vortices and changes in flow direction. Studying these parameters is crucial when analyzing airfoil-based shapes in real-world scenarios. In this study, a vortical environment is created using a circular cylinder, and changes in flow direction are simulated using a pitching airfoil. The vortical flow passed a pitching airfoil is analyzed experimentally and numerically at different reduced frequencies (kf), the ratio of the gap to the cylinder diameter(G/D), and pitching oscillation amplitude(α0). The flow behavior is presented in experimental terms of the mean streamwise velocity (U‾), turbulence intensity (Ti), and power spectral density (PSD) downstream of the pitching airfoil, and numerical contours of velocity field, turbulence intensity, and vorticity. The current study confirms the change in time and frequency domain parameters and provides new insight into the unsteady airfoils. The results show a change in the shedding mechanism in the case of G/D=2, emerging two periodic vortical streets in the wake of pitching airfoil in the case of G/D=6and10, and replacing cylinder vortex shedding frequency with pitching frequency of airfoils.]]></description>
      <pubDate>Wed, 11 Feb 2026 15:10:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2660743</guid>
    </item>
    <item>
      <title>Study on the lock-in delay coefficient in the mathematical model of transversal vortex-induced vibration for a rigid circular cylinder</title>
      <link>https://trid.trb.org/View/2660674</link>
      <description><![CDATA[This study revisits the definition of the lock-in delay coefficient and the interpretation of lock-in delay. A one-degree-of-freedom structural model, along with the classical van der Pol wake oscillator equation, is employed to investigate the inconsistency between the definition and the interpretation. To resolve this issue, the lock-in delay coefficient is redefined, and an improved mathematical model is proposed. This model implies that the corrected Strouhal number solely influences the structure of the wake equation. Two objective functions and two sets of initial empirical coefficients are established for eight distinct mass ratios. The pattern search algorithm in conjunction with published experimental data is utilized to calibrate the new model. The calibrated models are capable of effectively predicting the displacement amplitudes of the cylinder subjected to transversal vortex-induced vibration. To mitigate the high computational costs associated with calibrating the model for all mass ratios using the optimization algorithm, a weighting method is proposed. This method leverages the calibrated empirical coefficients obtained at specific partial mass ratios to extrapolate the empirical coefficients for other mass ratios. Comparative analyses with published experimental data indicate that the calibrated models, derived from the weighting method, provide acceptable predictions for cross-flow oscillations.]]></description>
      <pubDate>Wed, 11 Feb 2026 15:10:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2660674</guid>
    </item>
    <item>
      <title>Near wake control of a square cylinder by screen shrouds</title>
      <link>https://trid.trb.org/View/2661459</link>
      <description><![CDATA[This study investigates the influence of screen shrouds with varying permeability on the wake dynamics of a square cylinder at a Reynolds number of Re = 13600. High-resolution Particle Image Velocimetry (PIV) measurements were conducted in a closed-loop water channel using screen shrouds with permeability ratios of β = 0.46, 0.63, and 0.7 concentrically mounted around the square cylinder. The shrouds acted as passive flow control elements by altering the momentum distribution and delaying the interaction of separated shear layers. The experimental results indicate that moderate permeability (β = 0.63) showed effective flow control. The peak turbulent kinetic energy and Reynolds shear stress were reduced by 30 % and 25 %, respectively, compared to the square cylinder. In this configuration, the vortex formation length increased by 137.2 %, while the shear layer length increased by 62.8 %, and wake width narrowed by 17.3 %, indicating stabilized near-wake turbulence and delayed vortex roll-up. These findings demonstrate that applying a screen shroud with an appropriate permeability not only suppresses the influence of fluctuating components but also delays the interaction of shear layers, confirming the effectiveness of this passive flow control approach.]]></description>
      <pubDate>Wed, 11 Feb 2026 15:10:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2661459</guid>
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