Microscopic modeling of sound waves in granular material: Quarterly progress report, 4/1/87-6/30/87
Preliminary computer simulation studies have been carried out regarding several aspects of sound waves in granular materials. A simulation code has been developed in which irregular frictional particles are composed of clusters of disks, since detection of overlaps and computation of forces is especially straightforward for contacts between disks. Moreover, we anticipate that three-dimensional studies will, in analogy to the present disk simulations, be most easily implemented by the construction of irregular particles out of spherical elements. Two broad categories of the acoustic properties of granular materials have been under investigation. In the first category, a collection of disks is confined under the influence of gravity, to a three-sided test cell. The fourth side of the box, consisting of a lid, or piston, is free to move up and down. The particles are allowed to come to rest after placement in the cell, and then a harmonic excitation in the form of a vertical sinusoidal oscillation is imposed upon the bottom of the test bed. An elastic disturbance propagates upward through the granular media, finally influencing the motion of the piston which rests by virtue of its own weight upon the test-cell particles. In a second line of investigation we are studying pressure fluctuations on the bed of a channel beneath a free surface grain flow. The behavior of the granular material near the wall is related to the behavior in the bulk by the boundary conditions on the flow. Thus detailed modelling of the pressure fluctuation or sound at the wall of a conduit containing flowing granular material has potential as a non-invasive diagnostic tool for grain flow.
- Research Organization:
- California Inst. of Tech., Pasadena (USA)
- DOE Contract Number:
- FG22-86PC90959
- OSTI ID:
- 6364268
- Report Number(s):
- DOE/PC/90959-T2; ON: DE87012409
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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