Influence Of Aerodynamic Loads Research Articles

Research on sliding mode controller of the high-speed maglev train under aerodynamic load

The high-speed maglev train will be subjected to extremely obvious aerodynamic load and instantaneous aerodynamic impact during passing another train, which brings significant challenges to the train’s suspension stability and safe operation. It’s necessary to consider the influence of aerodynamic load and shock waves in the design of suspension control algorithms. Traditional proportion integration differentiation (PID) control cannot follow the change of vehicle parameters or external disturbance, which is easy to cause suspension fluctuation and instability. To improve the suspension stability and vibration suppression of the high-speed maglev train under aerodynamic load and impact, we design a siding mode controller introducing the primary suspension’s deformation to replace the aerodynamic load on the electromagnet. Furthermore, we establish the train’s dynamic simulation model with three vehicles and compare the designed controller and the PID controller for their performance in controlling the model suspension stability in the presence of the train operating in open air. Simulation results show that the sliding mode control (SMC) method proposed in this paper can effectively restrain the electromagnet fluctuation of the train under aerodynamic loads.

The Influence of Aerodynamic Loads on Carbody Low-Frequency Hunting of High-Speed Trains

Low-frequency hunting problems of high-speed railway vehicles frequently occur due to the complex operating environment and degradation of wheel–rail contact conditions, which significantly affect the running safety and ride comfort of high-speed trains (HSTs). This paper presents a numerical investigation of the influence of aerodynamic loads on the carbody low-frequency hunting behaviors of HST. Considering the effect of aerodynamic loads, a multi-body system dynamics model for a HST train is formulated and applied to reproduce the carbody low-frequency hunting behavior. The influence of aerodynamic loads and wheel–rail contact conditions on the nonlinear stability of HST is analyzed. The range of aerodynamic coefficients of different aerodynamic loads which can stimulate the low-frequency hunting behavior of HST is proposed. The results show that the aerodynamic loads have a prominent effect on the nonlinear stability of HSTs. The low-frequency hunting motion of the HST tail car can be motivated by the lift airflow generated during service operation with a high traveling speed. The running stability of HSTs is more easily influenced by the aerodynamic loads when wheels are reprofiled.

Nonlinear hunting stability of high-speed railway vehicle on a curved track under steady aerodynamic load

ABSTRACTThis paper investigates the nonlinear hunting stability of a high-speed vehicle on a curved track under steady aerodynamic load. We first established a nonlinear dynamic model of high-speed vehicle on a curved track while considering the effect of aerodynamic load. Then, we wrote a numerical simulation programme and verified the validity. The following two types of aerodynamic conditions were concerned in this study: considering only the aerodynamic lift and considering the crosswind loads. The influence of aerodynamic load on the creep force, the restoring force and moment generated by gravity, and the equilibrium position of the vehicle on the curved track can all change the hunting stability. We calculated bifurcation diagrams, limit cycle motions, nonlinear critical speeds, and frequency spectrum considering those two types of aerodynamic conditions, then compared with those without considering the aerodynamic effects. The results show that multiple frequencies including double frequency, triple frequency, quadruple frequency, and high frequencies will appear in addition to the fundamental frequency when hunting motion occurs. The higher frequencies which are even times of fundamental frequency are caused by the deviation of equilibrium position from track centre, while the deviation of equilibrium position is generated by curve track or crosswind load. Additionally, a positive aerodynamic lift and a crosswind load in the centrifugal direction will decrease the vehicle’s motion stability, while a negative aerodynamic lift and a crosswind load in the centripetal direction can improve the stability.

Study on wheel/rail adhesion force and its control of high-speed trains considering aerodynamic loads and track excitations

The wheel/rail vertical loads are strongly affected by the aerodynamic loads and track excitations, and will further influence the wheel/rail adhesion forces. With the increasing of train speed, the influence of aerodynamic loads becomes more and more significant. In order to probe into this problem, a simplified train dynamic model with three vehicles is established in which each vehicle system has 14 degrees of freedom. The track irregularity spectrum of a high speed line in China and steady aerodynamic loads are taken as the inputs to the vehicle system. Numerical simulation is carried out by using MATLAB. It is found that the aerodynamic loads obviously affect the wheel/rail contact forces for the high-speed train. Under the same train speed, with the increasing of crosswind velocity, the wheel/rail contact forces for cars at different positions in the train set are reduced gradually. Under the same crosswind velocity, the impact of aerodynamic loads on the different-position vehicle is different. The model of wheel/rail adhesion fuzzy control is built and preliminary analysis is conducted. The strategy of predictive control based on the vehicle system is introduced.

On the performance of ground vehicles under the influence of stochastic wind loads

AbstractThe influence of aerodynamic loads on the performance of ground vehicles is an important economical, safety and comfort issue. For the safety and comfort matters, especially the crosswind behavior of the ground vehicles is of great interest, as strong lateral winds can cause major accidents or at least make the driver and the passengers feel very uncomfortable and insecure.Two different failure scenarios dominate the safety aspect. The most important one is the risk of overturning, which happens not very often but if it occurs it leads in most cases to serious personal damages and the second one is the sudden lane change of road vehicles and the associated driving instabilities because of unforeseen gusts.As most of the design and excitation parameters of the system are uncertain, they are recognized as stochastic variables. Taking the mentioned failure scenarios into account the probability of failure of a freight vehicle has been computed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of Aerodynamic Loading on Rotor-Stator Aerodynamic Interaction in a Two-Stage Low Pressure Research Turbine

The unsteady flow within a two-stage low-pressure research turbine equipped with high lift profiles has been investigated in detail for three different aerodynamic loading conditions. Experiments have been carried out at low speed. Velocity and turbulence intensity in the blade-to-blade plane at midspan have been measured by means of a crossed hot-wire probe, upstream and downstream of each blade row. The probe has been traversed circumferentially over 1.5 bladings pitch and the phase-locked data acquisition and ensemble average technique have been used to reconstruct the flow in space and time. The effects of multistage configuration have been identified and analyzed by considering the velocity components and turbulence intensity. Potential interaction from the downstream blading in relative motion, periodic wake perturbations from the upstream blading and preceding stage perturbations make the flow in the second stage extremely complex. Overall the flow downstream of rotors is perturbed in space by upstream and downstream stators, while flow downstream of stators is mostly perturbed in time by rotor effects. As expected, high lift profiles are significantly sensitive to incidence variation, with this effect further enhanced by the multistage cumulative interactions.

Influence of aerodynamic loads on flight trajectory of spinning spherical projectile

Influence of aerodynamic loads on flight trajectory of spinning spherical projectile

Influence of Aerodynamic Loads on Flight Trajectory of Spinning Spherical Projectile

The effect of lift and drag forces and aerodynamic moment on the flight of a spinning projectile in the atmosphere is investigated. The influence of the spin rate of the projectile on the range and height of flight is also studied, taking into consideration the progressive decay in the spin rate during the flight. The governing equations of motion of the projectile have been solved numerically, and the results are presented graphically. The effect of various parameters such as angle of projection, initial velocity, and spin on the flight of projectiles are plotted. From the results it can be concluded that the lift and drag forces and the aerodynamic moment, which are dependent on the spin rate of the projectile, influence the range and height of the trajectory significantly. Only planar motion of the projectile is considered