Louis Gagnon

A multibody dynamics model to assess the impact of road unevenness on the efficiency of a semitrailer truck

An open source multibody model of a semi-trailer truck with 331 degrees of freedom was built and within it a dynamic tyre model has been implemented. The truck model was calibrated and validated by an on-road experimental campaign of coastdown tests. The signal from a photodetector and ten accelerometers, the weight distribution, meteorological data, and the longitudinal profile have been collected. The purpose of the model is to obtain the relationships between the longitudinal road profile and fuel consumption, vehicle wear, passenger health, and safety. A subsequent study demonstrated the capacity of the model to fulfil its purpose.

An overview of various new road profile quality evaluation criteria: part 1

A multibody tractor–trailer model specialised in measuring the impact of road surface quality on the efficiency of transport was developed. It was calibrated and validated using a coastdown tests experimental campaign. The model was then used within an extensive profile study that linked specific profiles to their impact on energy consumption, vehicle wear, driver and passenger health, and safety. Two hundred and seventy 1 km long profiles were tested with the multibody vehicle travelling at 100 km/h. It allowed to identify trends in the relationships between various profile rating criteria and the impacts aforementioned. The criteria consist of 19 indices observed on a quarter car model operating on longitudinal road profiles. They yield accurate predictions of profile impacts. For the operating conditions considered, the long wavelengths have a strong effect on health, medium wavelengths on safety and short to medium wavelengths on energy consumption.

Assessment of the relationship between the international roughness index and dynamic loading of heavy vehicles

Abstract Due to imperfect surface profiles, heavy vehicles moving at high speed on flexible pavement structures oscillate in the vertical axis. This phenomenon induces dynamic loads, which oscillate at lower and higher values than the average load associated with static load considered with most pavement analysis and design applications. Higher loads applied to flexible pavements are likely to significantly reduce pavement service life. A new multibody dynamic truck model was used to study heavy vehicle wheel load for various pavement profiles of varying international roughness index (IRI). The modelled heavy vehicle wheel load response were used to calculate the dynamic load coefficient, and a relationship with IRI was proposed. On the basis of this relationship, the evolving pavement surface profile, and thus evolving IRI, was used to determine the evolution of dynamic loading with pavement life. A comparison of pavement service life for the classical static loading and for dynamic loading was made for three highway flexible pavement structures. When dynamic loads are considered, it was found that the pavement service life reduction may be reduced of about 29 and 20% for bottom-up fatigue cracking and structural rutting failure criteria.

Aerodynamic models for cycloidal rotor analysis

Purpose Few modeling approaches exist for cycloidal rotors because they are a prototypal technology. Thus, the purpose of this study was to develop new models for their analysis and validation. These models were used to analyze cycloidal rotors and a helicopter that uses them instead of a tail rotor. Design/methodology/approach Three different models were developed to study the aerodynamic response of cycloidal rotors. They are a simplified analytical model resolved algebraically; a multibody model resolved numerically; and an unsteady computational fluid dynamics (CFD) model. The models were validated using data coming from three different experimental sources, each with rotor spans and radii of roughly 1 m. The CFD model was used to investigate the influence of rotor arms. The efficiency and the stability of the rotor in different configurations were studied. An aeroelastic multibody simulation was used to verify the influence of flexibility on the rotor response. Findings The analyses suggested that cycloidal rotors can increase the efficiency of a helicopter at high velocities while flexibility reduces it and may lead to instabilities. Research limitations/implications These models do not consider the effect of boundary layer friction on the trailing vortices generated by the rotor blades. Practical implications These models allow a four-step aerodynamic optimization procedure. First, a range of optimized configurations is obtained by the analytical model. Second, the multibody model refines that range. Third, the CFD model detects eventual problematic blade interactions. Originality/value The models presented should serve researchers and industrials looking for a means to measure the performance of cycloidal rotors concepts. The results presented also guide an initial cycloidal rotor design.

Influence of Tyre–Road Contact Model on Vehicle Vibration Response

The influence of the tyre–road contact model on the simulated vertical vibration response was analysed. Three contact models were compared: tyre–road point contact model, moving averaged profile and tyre-enveloping model. In total, 1600 real asphalt concrete and Portland cement concrete longitudinal road profiles were processed. The linear planar model of automobile with 12 degrees of freedom (DOF) was used. Five vibration responses as the measures of ride comfort, ride safety and dynamic load of cargo were investigated. The results were calculated as a function of vibration response, vehicle velocity, road quality and road surface type. The marked differences in the dynamic tyre forces and the negligible differences in the ride comfort quantities were observed among the tyre–road contact models. The seat acceleration response for three contact models and 331 DOF multibody model of the truck semi-trailer was compared with the measured response for a known profile of test section.

Aerodynamic and Aeroelastic Analysis of a Cycloidal Rotor

This work presents aerodynamic and aeroelastic models used to investigate the behaviorof a cycloidal rotor scaled for personal transportation applications. Three different modelsare considered. The impact of solidity on performance is evaluated using a two-dimensionalRANS viscous flow model with the boundary layer fully resolved. An aeroelastic multibodymodel is used to further evaluate the effects of aeroelasticity on the performance of therotor.

Parametric Analysis of a Large-scale Cycloidal Rotor in Hovering Conditions

In this work, four key design parameters of cycloidal rotors, namely the airfoil section; the number of blades; the chord-to-radius ratio; and the pitching axis location, are addressed. The four parameters, which have a strong effect on the rotor aerodynamic efficiency are analyzed with an analytical model and a numerical approach. The numerical method is based on a finite-volume discretization of two-dimensional Unsteady Reynolds Averaged Navier-Stokes equations on a multiple sliding mesh, are proposed and validated against experimental data. A parametric analysis is then carried out considering a large-scale cyclogyro, suitable for payloads above 100 kg, in hovering conditions. Results demonstrate that the airfoil thickness significantly affects the rotor performance; such a result is partly in contrast with previous findings for small- and micro-scale configurations. Moreover, it will be shown that increasing the number of blades could result in a decrease of the rotor efficiency. The effect of chord-to-radius will demonstrate that values of around 0.5 result in higher efficiency. Finally it is found out that for these large systems, in contrast with micro-scale cyclogyros, the generated thrust increases as the pitching axis is located away from the leading edge, up to 35% of chord length. Further the shortcomings of using simplified analytical tools in the prediction of thrust and power in non-ideal flow conditions will be highlighted and discussed.

The Process of Making an Aerodynamically Efficient Car Body for the SAE Supermileage Competition

In the summer of 2010, a new body shell for the SAE Supermileage car of Laval University was designed. The complete shell design process included, amongst other steps, the generation of a shape through the parametric shape modeling software Unigraphics NX7 and the evaluation of aerodynamic forces acting on the chassis using the open source Computational Fluid Dynamics (CFD) software OpenFOAM. The CFD analyses were ran at steady-state using a k-omega-SST turbulence model and roughly 2.5 million cells. An efficient method for evaluating the effect of ambient wind conditions and vehicle trajectory on the track was developed. It considers the proportion of time that the car operates at each combination of velocity and wind yaw angle and computes the overall energy demand of the shell. An iterative process was conducted over a significant number of different shapes, which were generated by joining formula-based guide curves using intersection and tangency conditions. The new shell has a 25 % larger frontal area due to modified design constraints. When aerodynamically compared to the smaller and already highly efficient old vehicle, reductions of 50 % of the negative lift, 15 % of the energy demand when driving forward, and 5 % of the energy demand when turning are achieved by the new design. Also, the drag coefficient is reduced by 20 %. These improvements come from the quasi-NACA profiles on the side and top walls; a reduction of cavities to prevent redundant frontal areas; a short vehicle and smother wheel cover closures; and a thorough study of the nose and tail. This paper describes numerical flow simulations and the changes that were brought to the vehicle body to make it as aerodynamically efficient as possible.

Aeroelastic Analysis of a Cycloidal Rotor Under Various Operating Conditions

The aeroelasticity of a cycloidal rotor in forward flight is investigated using an analytical and a numerical model; the latter is based on a multibody dynamics approach. Three experimental sources are used to validate the multibody model. The influence of the number of blades, their stiffnesses, and their skin thicknesses are investigated. At high pitch angles, before stall and flexibility effects occur, increasing the number of blades produces more thrust for the same power. Flexibility and skin thickness considerably affect the required pivot rod strength and blade deformation. Simply supported blades exhibit severe deformations when compared to clamped blades. Thrust and power are both influenced in a similar and moderate way by flexibility. The rotor response to wind gusts is also analyzed. The angular velocity of the rotor significantly affects the response of the rotor to wind gusts. The direction of the gusting wind has an important influence on power, whereas thrust increases regardless of wind direction. Finally, the rotor response lags minimally behind the arrival of the gust.

Improving the calibrated fMRI estimation of CMRO 2 with oxygen-sensitive Two-Photon Microscopy

We improved the accuracy of calibrated fMRI by using Two-Photon microscopic measurements of cortical microvasculature together with first principle Monte Carlo simulations of proton diffusion across the two-photon volumes.