On Improvement Of New Technology CAE Software ADEM

Particles are widely spread in the actual world: dust in the air, pebble in rivers and cobblestones in the sand are good example of the term “particles”. Also, soy beans, wheat and corn in agriculture production, or steel balls in industrial production can be treated as particles. As a result of such wide spread of particles, we conclude that they are important to people’s daily life.Vast amount of particles reach some steady state by force, either external or between particles. Professor Cundall presented discrete element method(DEM) to research motion of particles. DEM treats every single particle as a single entity, predicting the motion of particles by calculating and gather information about their stress on every time step. Great co mplexity exists when doing such calculation, resulting in the importance of computer science in DEM.In the actual agriculture production, it is supported by much measurement and verification that particles could be treated as ball- like entities so that simulation could be safely made based on the assumption of ball- like particles. Crop particles may be sieved, piled, extracted and transported. Such scenes contain not only inter-particle forces, but also external forces. For example, a barn applies forces to soy beans- under such circumstance, well- made bound checking procedure must be applied to ensure steady piling of particles; when sieving soy beans, forces applied by a rod to the beans may be critical to the success of the sieving procedure; fluids motion and properties of fluids may affect the result of the extraction.After a long effort, our project group has developed rich theory foundation and advanced software system for DEM calculation. However, there are still problems left to be improved: for example, bound checking sometime makes error, causing illegal motion when particles reached the bounds. It is also a problem that many advanced features are still not implemented in the system: the force applied by particles to the rigid body is not considered by now; neither is motion of particles in fluids.This thesis presents some improvement for the original ADEM software system. First, discussions about illegal motion in the old bound checking procedures are given. Local coordinate system, whose feasib ility is proved by presenting new bound checking procedures on 3 basic forms of cone, circular truncated cone and cylinder, is introduced to replace the global coordinate system in ADEM. Second, multi-body kinematics algorithms are introduced based on our project group’s research on multi-body dynamics and DEM interconnection calculation, resulting in a novel dynamic procedure of particles and rigid bodies, which replaces the traditional kinematics procedure. Comprehensiveness of such interconnection calculation are reached by introducing hinge objects and multi-body inverse dynamics. Lastly, discussions about the overall structure of ADEM and the widely used software system Fluent are given to cover the basic operations of ADEM and the intercommunication of ADEM and Fluent.Test cases covering all modifications are given for verification. The test results show that the modified bound checking procedure are more realistic. Feasibility and correctness of multi-body inverse dynamic analysis are verified by step-by-step analysis of stress status of rigid bodies and rigid-body-particle interconnection on every time step. Usability of the software system are reached by introducing the usage of ADEM-Fluent intercommunication in details. Simulation results show that the calculation of our system are satisfiable.