Research on rolling stability of the flexible waverider based on computational fluid dynamics/computational structural dynamics/rigid body dynamics coupling methodology

The shape of hypersonic aircrafts represented by waveriders is becoming more slender and flatter, thereby greatly reducing the structural rigidity. This innovation is applied to satisfy the demand of long-range flight. The rolling stability of the waveriders is poor due to the slender shape. Therefore, the effect of the elastic deformation on the rolling stability cannot be ignored. The effect of the elastic deformation on the stability of rolling and forced pitching/free rolling coupling motions of the waveriders is studied through computational fluid dynamics (CFD)/computational structural dynamics (CSD)/rigid body dynamics (RBD) coupling methodology. Comparison results of numerical simulation indicate that the elastic deformation of the structure increases the local angle of attack, thereby enhancing the static stability of the waveriders. The rolling motion of the waveriders changes from point attractor to periodic attractor when the vibration velocity due to elastic deformation is considered. The rolling oscillation frequency of the flexible model is higher than that of the rigid model. For the forced pitching/free rolling motion, stability theory based on the rigid body hypothesis is unsuitable when the elastic effect is taken into consideration.

A Study on Anti-Shock Performance of Marine Diesel Engine Based on Multi-Body Dynamics and Elastohydrodynamic Lubrication

Diesel engine anti-shock performance is important for navy ships. The calculation method is a fast and economic way compared to underwater explosion trial in this field. Researchers of diesel engine anti-shock performance mainly use the spring damping model to simulate the main bearings of a diesel engine. The elastohydrodynamic lubrication method has been continuously used in the main bearings of diesel engines in normal working conditions. This research aims at using the elastohydrodynamic lubrication method in the main bearings of the diesel engine in external shock conditions. The main bearing elastohydrodynamic lubrication and diesel engine multi-body dynamics analysis is based on AVL EXCITE Power Unite software. The external shock is equivalent to the interference on the elastohydrodynamic lubrication calculation. Whether the elastohydrodynamic lubrication algorithm can complete the calculation under interference is the key to the study. By adopting a very small calculation step size, a high number of iterations, and increasing the stiffness of the thrust bearing, the elastohydrodynamic lubrication algorithm can be successfully completed under the external impact environment. The calculation results of the accelerations on engine block feet have a similar trend as the experiment results. Diesel engines with and without shock absorbers in external shock conditions are calculated. This calculation model can also be used for diesel engine dynamics calculations and main bearing lubrication calculations under normal working conditions.

Study on the mechanical effect and wear behaviour of middle trough of a scraper conveyor based on DEM–MBD

Middle trough is the main-force portion of a scraper conveyor during transport, and its performance directly affects the reliability and service life of the scraper conveyor. To investigate the wear of a middle trough, a coupling-wear model of a middle trough was built to analyse the motion state and stress of a scraper, and the wear of the middle trough was analysed according to the wear morphology of the middle plate. The research results demonstrated that the simulation model based on coupling of the discrete element method and multi-body dynamics could effectively simulate the transport conditions of a scraper conveyor. The wear of the middle trough was mainly caused by three-body wear. Formation of three-body wear required that the coal particles between the scraper (chain) and middle plate must be in a certain position and posture, and the coal particles were subjected to the normal force of the scraper (chain) and middle plate. Constant fluctuation in the movement and force of the scraper (chain) resulted in uneven wear of the middle trough and random occurrence of three-body wear. This study provides a theoretical basis for wear prediction of the middle trough of a scraper conveyor and a simulation basis for further research on the wear resistance of a middle trough.