Author(s)

A. Dwivedi, B. Melville, E. Akeila & Z. Salcic

Abstract

Design of ‘Smart’ pebble for sediment entrainment study A. Dwivedi1, B. Melville1, E. Akeila2 & Z. Salcic2 1Department of Civil & Environmental Engineering, The University of Auckland, Auckland, New Zealand 2Department of Electrical and Computer Engineering, The University of Auckland, Auckland, New Zealand Abstract The ‘Smart’ pebble is a small self-equipped datalogger having a 40 mm outer diameter with a built-in sensor for acceleration and rotation measurements. This pebble has the capability to detect instantaneous acceleration due to turbulence in fluid, which is indicative of hydrodynamic forces acting on the pebble. The pebble stores the data continuously in its internal memory. These data can subsequently be transferred by serial port to a computer for detailed analysis. Test runs using the smart pebble have been carried out to validate accurate functioning of the acceleration and gyro sensor. The acceleration of the smart pebble was compared to the acceleration of the shake table. The results show the excellent capability of the pebble to record the instantaneous forces acting on the pebble during its entrainment. Keywords: entrainment, hydrodynamic forces, accelerometer, gyroscope. 1 Introduction In order to understand the processes causing particle entrainment, the stability of the separate particles must be evaluated. The hydrodynamic forces on the particles are very important for understanding this stability. Figure 1 (a) shows the hydrodynamic forces acting on the sediment particle. Figure 1 (b) shows the test arrangement of smart pebble. This research has been aimed at improving the present level of understanding of the physical processes involved in the transport of individual sediment particles in the near bed region of a turbulent open channel flow by the use of smart pebble.

Keywords

entrainment, hydrodynamic forces, accelerometer, gyroscope.