On modeling the behavior of a granular medium under vibration

Abstract

This article describes experimental studies of harmonic motion of a granular material layer (sand) in a vessel under vertical harmonic vibrations. The experiments were aimed to establish the application limits for the simplest model of the vibrational displacement theory to predict material motion. In this model, the material layer is represented by a particle moving without air resistance. Such a model is often used when designing screens and other vibrational transportation and process vibration machines. Even with this simplest model, numerous conditions must be considered and complex calculations must be made. The duration of granular material layer separation from the supporting surface is taken as the main parameter characterizing model applicability as it dictates the material vibrational transportation rate and energy consumption for the process. The separation duration was recorded using pressure oscillograms generated by a sensor installed at the bottom of the vessel. It has been experimentally established that this duration is somewhat lower than the calculated value due to the resistance of air filtered through the layer. The model is found applicable when this differential is not excessive. The paper identifies areas of change in the material layer thickness and vibration intensity within which the simplest model may be applied. These correspond to rather thick layers of a granular medium (up to 200 mm) at relatively low overload factors and to very thin layers (up to 35 mm) at high overload values. Outside these areas, more complex models should be used. Other experimental results are also discussed. It may be expected that, for a freely permeable support surface, such as the screening surface of a vibrating screen, the simplest model would be applicable under broader conditions.The authors are grateful to Professor I. I. Blekhman for the idea of the work, discussion of the results, and critical remarks.The work was carried out within the framework of the state task of the Ministry of Science and Higher Education of the Russian Federation (Subject No. 121112500313-6).