A method to solve minimum-lap-time problems using quasi-steady-state models and free (i.e. not predetermined) trajectory on two-dimensional tracks has been recently proposed. This work describes the ...extension of the method to three-dimensional tracks and builds upon g-g-g diagrams (instead of the standard g-g), to account for the effects of three-dimensionality. The main features of car and motorcycle g-g-g diagrams are discussed, to get insight into the main effects of three-dimensionality and to suggest a convenient parametrisation for the subsequent optimal control problem (OCP), whose size is not affected by the complexity of the vehicle model employed to generate the g-g-g diagrams. The application of the method to the Mugello and Barcelona-Catalunya circuits is given, with vehicle datasets resembling those of a race motorcycle (MotoGP) and a race car (Formula One). The results obtained are in line with those reported in the literature using full-dynamic models, yet such dynamic models are generally associated with the solution of much larger OCP.
Minimum-lap-time simulations with quasi-steady-state models and predefined trajectory have been in use for many years. However, most of the published works deal with two-dimensional roads and employ ...the so-called apex-finding method. This paper focuses on the application to three-dimensional roads, both with an extension of the 'apex-finding' approach to three-dimensional scenarios and with an optimal control method. Both approaches are based on g-g-g diagrams, i.e. the three-dimensional extension of the well-known g-g maps. In addition, under the assumption that the predefined trajectory is determined from noisy data (e.g. logged from the real vehicle), the three-dimensional trajectory reconstruction problem is addressed, to find a smooth and drift-free racing line to be used in the minimum-time simulation - again an optimal control approach is employed for the trajectory reconstruction. Examples of application are given both for a car and a motorcycle.
Three-dimensional road models for vehicular minimum-lap-time manoeuvring are typically based on curvilinear coordinates and generalizations of the Frenet–Serret formulae. These models describe the ...road as a parametrized ‘ribbon’, which can be described in terms of three curvature variables. In this abstraction the road is assumed laterally flat. While this class of road models is appropriate in many situations, this is not always the case. In this research we extend the laterally-flat ribbon-type road model to include lateral curvature. This accommodates the case in which the road camber can change laterally across the track. Lateral-position-dependent camber is introduced as a generalisation that is required for some race tracks. A race track model with lateral curvature is constructed using high-resolution LiDAR measurement data. These ideas are demonstrated on a NASCAR raceway, which is characterized by large changes in lateral camber angle (
≈
10
∘
) on some parts of the track. A free-trajectory optimization is employed to solve a minimum-lap-time optimal control problem. The calculations highlight the practically observed importance of lateral camber variations.
This article presents a new turbulence closure based on the k-ω SST model for predicting turbulent flows of Herschel–Bulkley fluids, including Bingham and power-law fluids. The model has been ...calibrated with direct numerical simulations (DNS) data for fully-developed pipe flow of shear-thinning and viscoplastic fluids. The new model shows good agreement in the mean velocity, average viscosity, mean shear stress budget and friction factor. The latter compares well also against correlations from the literature for a wide range of Reynolds numbers. With the new model, improvements are also observed in the iterative convergence, which is often difficult for calculations with yield-stress fluids. Additionally, three eddy-viscosity models for Newtonian fluids, namely the k-ω SST, k-kL and Spalart–Allmaras model, have been tested on turbulent Herschel–Bulkley flows. Results show that (i) the new model produces the best prediction; (ii) the standard SST model may be considered for simulations of weakly shear-thinning/viscoplastic fluids at high Reynolds numbers; (iii) the k-kL and the Spalart–Allmaras models appear to be unsuitable for turbulent Herschel–Bulkley flows. The new model is simple and appealing for engineering applications concerned with turbulent wall-bounded flows and is presented in a formulation that can be easily adapted to other generalised Newtonian fluids.
•A new RANS model for power-law, Bingham and Herschel–Bulkley fluids is developed.•The performance of the new model is compared with three Newtonian RANS models.•The new model well predicts the mean velocity profile and friction factor.
► Concretes were produced with different levels of fine and coarse aggregates the C&D waste, for different w/c ratios. ► Response surface methodology (RSM) was used to evaluate the mechanical and ...durability properties. ► Use of recycled aggregate increases the w/c ratio, water absorption and carbonation depth of concrete. ► 50% substitution by fine and coarse C&D aggregates are feasible from a technical, economic and environmental point of view.
Growing concern with the preservation of non-renewable natural resources has led to the development of studies on the use of recycled aggregates in concrete production. In view of the diversity and variability of these aggregates there is a lack of consensus on the performance of these concretes. This study uses response surface methodology (RSM), to jointly evaluate the mechanical and durability properties (water absorption and carbonation depth) of concretes produced with different levels of fine and coarse aggregates, the C&D waste, for different w/c ratios. Concrete production costs were also evaluated. The results show that the increasing of the recycled aggregate, both fine and coarse, increases the w/c ratio, water absorption and carbonation depth of concrete. Coarse recycled aggregate has a greater influence on the mechanical properties, while fine recycled aggregate affects the concrete durability properties. Fifty percentage of substitution by fine and coarse C&D aggregates is feasible from a technical, economic and environmental point of view.
The presence of mud layers on the bottom of ports and waterways can have negative effects on the hydrodynamic behaviour of marine vessels. This numerical study investigates the effect of muddy ...seabeds on the full-scale resistance of an oil tanker sailing straight ahead. The objective is to determine the influence of factors such as the densimetric Froude number, UKC and mud rheology at speeds between 3 and 9 knots. The numerical study is conducted using a finite-volume Reynolds-Averaged Navier–Stokes (RANS) flow solver combined with the Volume-Of-Fluid (VOF) method to capture the mud–water interface. At certain critical speeds, the presence of mud increased the ship’s total resistance by up to 15 times compared to the case with solid bottoms. The non-Newtonian rheology of mud was found to influence the ship’s resistance mainly at low speeds and when sailing through the mud layer. This article also shows that, when sailing through mud, the computed resistance at high speeds may be underestimated because of two effects, namely ‘water lubrication’ and ‘numerical ventilation’.
•Effect of mud on the resistance of KVLCC2 is numerically investigated.•CFD simulations are performed using a finite-volume RANS flow solver.•Mud is modelled both as Newtonian and non-Newtonian (Bingham) fluid.•Resistance is influenced by internal waves at critical speeds.•Resistance is influenced by mud rheology when sailing through mud at low speeds.
When investigating the effect of muddy seabeds on marine vessels using Computational Fluid Dynamics (CFD) software, one challenge is to adequately describe the complex non-Newtonian fluid behaviour ...of mud. Although a number of rheological models have been proposed in the past, mud sediments are often simply regarded either as highly viscous Newtonian fluids or as Bingham fluids in many engineering applications. In this study, we investigate the accuracy of the Bingham model for numerical predictions of the viscous forces on a plate moving through fluid mud in laminar regime. In this context, a plate could be regarded as the flat bottom of a ship hull. The aim is to provide CFD practitioners with information about the accuracy of the Bingham model for the prediction of the frictional resistance of a ship sailing through fluid mud. This work presents a comparison of experimental and numerical data on the resistance of a plate moving through fluid mud from the Europoort area (Netherlands). Results suggest that the regularised Bingham model can be a reasonable compromise between simplicity and accuracy for CFD simulations to investigate the effect of muddy seabeds on marine vessels. A comparison between CFD data and analytical formulas is also presented.
•CFD data of the resistance of a plate moving through mud is compared with experiments.•Numerical simulations are performed using the Bingham model.•Towing tank experiments are carried out using fluid mud from the harbour.•The regularised Bingham model seems a good compromise between simplicity and accuracy.•CFD data are well predicted by analytical formulas.
An active steering assistant (ActiSA) system for powered two wheelers is introduced in this work, with the aim of enhancing the stability and safety of PTW. The proposed technology is alternative to ...steer-by-wire systems, which have a number of safety issues related to the removal of the mechanical connection between the handlebar and the front frame, and gyroscopic stabilizer, which tend to be heavy, expensive and energy-intensive. The paper illustrates the design and realisation of a steering assistant prototype and the integration in a light electric powered two wheeler. The prototype features an electric motor that provides the (assistant) steering torque to the front frame, which adds to the torque applied by the rider; a custom-steering torque sensor, aimed at monitoring the rider's effort on the handlebar; and a number of off-the-shelf sensors, which monitor the vehicle motion – steering angle, suspensions travel, angular velocity and accelerations of the main frame, rear wheel spin and GPS. Results from functional tests and performance assessment are also discussed.
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