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501.
Jon Grant Cedric Bacher Peter J. Cranford Thomas Guyondet Michel Carreau 《Journal of Marine Systems》2008,73(1-2):155-168
A fully-coupled biological–physical–chemical model of a coastal ecosystem was constructed to examine the impact of suspended mussel culture on phytoplankton biomass in Tracadie Bay, Prince Edward Island, Canada. Due to the extent of mussel culture there, we hypothesised that shellfish filtration would control the concentration and distribution of phytoplankton and other suspended particles in the bay. Circulation was delineated with a tidally-driven 2D numerical model and used to drive an ecosystem model with a focus on pelagic components including phytoplankton production, nutrients, detritus, and mussels. The benthos were treated as a sink. Nutrients and seston were forced by tidal exchange and river input, with phytoplankton additionally forced by light. Boundary conditions of seston and nutrients were derived from field studies with an emphasis on the contrast between spring (high river nutrients, low temperature) and summer (low river inputs and high temperatures). Model output was used to map phytoplankton carbon over the bay for each season and in the presence of mussels and river nutrient input. Results indicate severe depletion effects of mussel culture on overall phytoplankton biomass, but no spatial pattern that can be attributed to grazing alone. Primary production generated by nutrient-rich river water created a mid-bay spike in phytoplankton that dominated the spatial pattern of chlorophyll-based carbon. Model results were validated with surveys from a towed sensor array (Acrobat) that confirmed the river influence and indicated bay-wide depletion of 29% between high and low water. Our model results indicate that the farm-scale depletion emphasised in previous studies cannot simply be extrapolated to seston limitation at the ecosystem level. 相似文献
502.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(12):1607-1621
This work presents an approach to rollover prevention that takes advantage of the modular structure and optimisation properties of the control allocation paradigm. It eliminates the need for a stabilising roll controller by introducing rollover prevention as a constraint on the control allocation problem. The major advantage of this approach is the control authority margin that remains with a high-level controller even during interventions for rollover prevention. In this work, the high-level control is assigned to a yaw stabilising controller. It could be replaced by any other controller. The constraint for rollover prevention could be replaced by or extended to different control objectives. This work uses differential braking for actuation. The use of additional or different actuators is possible. The developed control algorithm is computationally efficient and suitable for low-cost automotive electronic control units. The predictive design of the rollover prevention constraint does not require any sensor equipment in addition to the yaw controller. The method is validated using an industrial multi-body vehicle simulation environment. 相似文献
503.
Chao-Tsung?HsiaoEmail author Georges?Chahine 《Journal of Marine Science and Technology》2004,8(3):99-108
A spherical and a nonspherical bubble dynamics models were developed to study cavitation inception, scaling, and dynamics in a vortex flow. The spherical model is a modified Rayleigh–Plesset model to account for bubble slip velocity and for nonuniform pressures around the bubble. The nonspherical model is embedded in an unsteady Reynolds-averaged Navier–Stokes code with appropriate free-surface boundary conditions and a moving chimera grid scheme around the bubble. The effect of nonspherical deformation and bubble/flow interaction on bubble dynamics is illustrated by comparing spherical and nonspherical models. It is shown that nonspherical deformations and bubble/flow interactions are important for an accurate prediction of cavitation inception. The surface-averaged pressure-modified Rayleigh–Plesset scheme is a significant improvement over the conventional spherical model, and is able to capture the volume changes of a bubble during its capture. It is also a fast scheme for studying scaling. In a preliminary study, the scaling effects on cavitation inception were examined using two different Reynolds numbers owing to two different chord lengths. The nuclei-size effect on the prediction of cavitation inception was also studied, and its important effects are highlighted. 相似文献
504.
505.
A semi-empirical dynamic tire model for combined-slip forces 总被引:1,自引:0,他引:1
Jacob Svendenius Magnus G fvert 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2006,44(2):189-208
This article presents a semi-empirical combined-slip tire model including transient behavior. It is assumed that the transient behavior is a result from the dynamic deformation of the tire carcass and that the interaction between the lateral and longitudinal slip, and forces can be explained by the deformation of the rubber treads. The deformation of the tire carcass makes the tread slip deviate from the wheel-rim motion in a way that may be described by differential equations. A method based on brush-model tire mechanics is used to construct the combined-slip forces as nonlinear scalings of corresponding pure-slip forces. 相似文献
506.
车-桥耦合振动分析的模态综合方法 总被引:1,自引:2,他引:1
对车辆与桥梁之间产生的耦合振动进行了全过程分析。首先通过有限元软件对桥梁进行模态分析,在此基础上建立三维车辆模型与桥梁模型组成互动体系的振动时变方程组,然后通过数值逐步积分进行求解。分析方法考虑了桥面平整度、车速等因素。该法不受桥型、跨径等因素的制约,可以模拟多车道和多辆车,有更强的通用性,优化精简了桥梁结构的自由度,提高了计算速度,计算结果准确可靠。 相似文献
507.
CFD simulation of 3-dimensional motion of a ship in waves: application to an advancing ship in regular heading waves 总被引:1,自引:0,他引:1
A new computational fluid dynamics simulation method has been developed for the unsteady motion of a ship advancing in waves.
The objective is to evaluate the added resistance and predict the performance of a ship in waves. In this study, a finite
volume method, in the framework of a boundary-fitted grid system, is employed. The motion of the ship is solved with six degrees
of freedom by using the hydrodynamic forces and moments obtained from the solution of the simulation method. The marker–density–function
method is employed to calculate the nonlinear free surface. This method is applied to the coupled motion problem of heaving
and pitching.
Received for publication on Nov. 15, 1999; accepted on Nov. 18, 1999 相似文献
508.
稳态条件下用于车辆动力学分析的轮胎模型 总被引:2,自引:0,他引:2
本文对稳态条件下可用于车辆动力学分析的轮胎理论模型和半经验模型,包括纵滑侧偏特性、纯纵滑特性和纯侧偏特性模型,进行了综合与分析,并讨论了各种模型间的相互关系。为车辆动力学分析提供了具体的轮胎模型和选用依据。 相似文献
509.
汽车—乘员三维多体系统碰撞仿真研究 总被引:1,自引:0,他引:1
本文以碰撞动力学和多体系动力学中的R-W方法为理论依据,建立了汽车-乘员三维多体系碰撞模型。在此基础上,开发了汽车碰撞计算机仿真软件SVC3D。仿真计算与试验结果的对比证明了模型的合理性及软件的正确性。 相似文献
510.