Damper Models for Heavy Vehicle Ride Dynamics

A laboratory rig for testing hydraulic dampers using the 'hardware-in-the-loop' method is described, and the accuracy of the test method is investigated. A mathematical model of a hydraulic shock absorber is then developed. The model is suitable for vehicle simulations and has seven parameters which can be determined by simple dynamic measurements on a test damper. The shock absorber model is validated under realistic operating conditions using the test rig, and the relative importance of various features of the model on the accuracy of vehicle simulations is investigated.     

Vehicle interior noise model based on a power law

Identifying the components of a vehicle’s interior noise is important in many phases of the noise, vibration, and harshness (NVH) development process. Many test methods that have been widely used in the automobile industry to separate noise sources are based on system identification methods in the frequency domain. However, none of the frequency response function-based methods can directly estimate the wind noise component. In this article, an analytical model for the interior noise level based on a simple power law was developed. It was assumed that the mean squared acoustic pressure for the interior noise could be obtained by summing up those of the wind noise, road noise, and background noise. The wind noise and road noise were further assumed to depend only on wind speed and the vehicle’s driving speed, respectively, and to follow a simple power law. The resulting analytical model includes five parameters that can be optimized for the vehicle and the road. The validity of the model was verified by using data obtained from cruise tests performed on a proving ground for cruise speeds ranging from 40 km/h to 130 km/h. The model is applied to the overall and 1/3-octave bands of interior noise and is shown to describe the data trends fairly well. For the test vehicle used in the present work, the overall mean squared pressures for the wind and road noise components are shown to be proportional to the wind speed to the 5.8 power and to the driving speed to the 3.4 power, respectively.     

Origin–destination table disaggregation using biproportional least squares estimation

This paper describes a group of techniques for disaggregating origin–destination tables for travel forecasting that makes explicit use of observed traffic on a network. Five models within the group are presented, each of which uses nonlinear least-squares estimation to obtain row and column factors for splitting trip totals from and to larger geographical areas into smaller ones. The techniques are philosophically similar to Fratar factoring, although the solution method is quite different. The techniques are tested on a full-sized network for Northfield, MN and are found to work effectively.     

An Optimal Self-Tuning Controller for an Active Suspension

An optimal self-tuning control algorithm is presented for vehicle suspension design. The controller, incorporating a weighting controller, state observer and parameter estimator, is designed according to linear optimal control (LQG) theory. Based on the updated estimates of vehicle parameters and states, and the adapted weighting parameters, the LQG controller provides the optimal set of gains over different operating conditions. The feasibility and effectiveness of the proposed self-tuning system was investigated and proved by simulation studies.     

Effect of nozzle orifice diameter on diesel spray tip penetration according to various spray models for CFD simulation with widely varying back pressure

CFD simulations of spray tip penetration with the standard KIVA3V, ‘original gas jet’ and ‘Normal gas jet profile with breakup length formula’ (NGJBL) spray models were performed to investigate the effects of nozzle orifice size and ambient gas density combinations on the spray penetration. The accuracy of the CFD simulation results was estimated by comparing them with available experimental data. The ambient gas density was varied in 12 kg/m³ intervals from 12 to 69 kg/m³ for each nozzle orifice diameter. The nozzle orifice diameters used were 119, 140, 183 and 206 mm. A total of 20 cases in the CFD simulations were considered with combinations of the 4 nozzle orifice diameters and 5 ambient gas densities. CFD simulations with the NGJBL spray model were more accurate than those with either the standard KIVA3V or gas jet spray models as the nozzle orifice diameter and ambient gas density was increased. The NGJBL and original gas jet model is more effective in predicting the spray tip penetration near the nozzle tip region.     

Large-eddy simulation of cross-flow around ship sections

The present work is motivated by phenomena occurring in the flow field around ship-like bodies with an incoming lateral flow (cross-flow, 90 ° drift angle). Three-dimensional unsteady flows around different ship sections are investigated by using computational fluid dynamic (CFD) tools with large-eddy simulation (LES) subgrid-scale turbulence model. The simulation results are compared to measurements at several Reynolds numbers in the 90–200,000 range. Focus in our investigation is on the characterization of the motion of vortex structures generated by the separated flow. Another target in the study is to obtain better knowledge of the hydrodynamic forces acting on the sections. Computed pressure and drag coefficients are compared with experimental measurements. The comparison between simulations and measurements shows that an LES model can predict the flow field around ship sections in detail and the hydrodynamic forces acting on the sections.     

层状边坡渐进破裂与失稳过程数值模拟探讨

运用岩石破裂与失稳过程分析RFPA^2D系统，以含层理弱层边坡的渐进破裂与失稳分析为例，通过对边坡渐进破裂与失稳发生孕育机制及其锚固控制规律的数值模拟，数值模拟再现了含层理弱层和锚固边坡渐进破坏与失稳的发生、发展过程，模拟结果表明，复杂结构边坡的渐进破坏与失稳现象是一些简单机理的演化结果。     

Patterns in diversity and community structure of epipelagic copepods from the Brazil–Malvinas Confluence area, south-western Atlantic

Diversity and structure of epipelagic copepod communities were investigated using 70 zooplankton samples collected from the top 50 m of the Brazil–Malvinas Confluence area between 35° and 55°S. Biogeographic patterns were investigated using multivariate analysis. Biodiversity patterns were examined using different univariate indexes. Representatives of 35 species of copepods from 23 genera and 13 families were found. Two zones were delimited based on their copepod composition, one in the subtropical waters of the Brazil current, and the other in the subantarctic waters of the Malvinas current. Both environments displayed contrasting patterns of biodiversity depending upon which element is measured (regional species richness as well as mean point species richness were significantly higher in the subtropical group of stations, whereas taxonomic distinctness was significantly higher in the subantarctic community). Based on these contrasting results, we suggest the use of both kind of indexes when defining priority areas for conservation.     

Vibration reduction of H/Shaft using an electromagnetic damper with mode change

The objective of this study is to develop a damper that can reduce the amplitude of vibration in various frequency ranges. Previous H/Shaft vibration reduction methods work in a passive way. A dynamic damper reduces the amplitude of vibration at its first mode, but vibration still appears at the second mode. A mass damper or hollow shaft can shift the natural frequency to a lower or higher region. The fixed operating frequency prevents vibration from being reduced outside the operating frequency range. The proposed damper uses electromagnets as either masses or actuators to change the damper mode between dynamic damper mode and mass damper mode. The electromagnetic damper (EMD) can change its mode to respond to the vibration excitation at both low and high frequencies. The vibration reduction performance was evaluated by FRF tests in laboratory and vehicle conditions. The results were compared with those of a dynamic damper and indicate that the amplitude of vibration is reduced by 95.6 % when the EMD is implemented on an H/Shaft, whereas only 61.9 % vibration reduction is achieved by the dynamic damper.     

Engine performance and toxic gas analysis of biobutanol-blended gasoline as a vehicle fuel

A comprehensive study evaluating the performance of biobutanol-blended gasoline in passenger cars was conducted because biobutanol is considered a better biofuel than bioethanol as it has no water solubility and it has a higher caloric value, giving it a higher energy value. Several kinds of samples—suboctane gasoline, 8 volume percentage and 16 volume percentage biobutanol—blended gasoline, and a 10 volume percentage MTBE-blended market sample (as the oxygencontaining gasoline)-were tested to evaluate the engine performance in terms of the detergency of the intake valves and combustion chambers, power, emissions, and fuel efficiency. Additionally, the toxicity of the emissions from these biobutanolblended samples was tested in order to assess the viability of biobutanol as one of the competitive potential substitutes for MTBE as an oxygenator in the near future. The results show that biobutanol-blended gasoline samples had relatively better detergency, relatively higher power, and similar levels of emissions compared with those of MTBE-blended gasoline. Formaldehyde was emitted from all of the samples at almost the same levels and within the error range, whereas biobutanolblended gasoline samples emitted approximately three times the amount of acetaldehyde than did the suboctane gasoline. This study shows that biobutanol is one of the best alternative bioalcohol fuels for use in the near future.