NUMERICAL SIMULATION OF STEADY FLOW OVER 3D RIPPLED BED

Numerical Simulation Of Steady Flow Over 3D Rippled Bed

Table of Content

INTRODUCTION1

DISCUSSION3

OSCILLATORY WAVE MOTION7

THE NUMERICAL MODEL9

MODEL RESULT12

VILLARET & PERRIER (1992) TEST12

CONCLUSIONS18

REFERENCES20

APPENDICES23

Numerical Simulation Of Steady Flow Over 3D Rippled Bed

Introduction

Advance in the understanding of bed morphology and sediment dynamics under oscillatory flows. Expand the present experimental database of sand bed configuration and evolution under controlled flow conditions in large scale facilities. Improve currently available tools for the prediction of bed configuration.

The literature review is now completed. Twenty seven data sources were colleted and converted to a uniform format to facilitate its analysis. Apart from the mean flow characteristics and basic geometric description of the ripples, information on the planform geometry of the ripples, the crest shape and the existence of superimposed bed forms was included. The available ripple predictors and our own experimental data are being compared to the compiled dataset. LOWST is now fully equipped and the installed equipment includes: A micro-ADV attached to an electronic positioning system, which allows for three-dimensional point velocity measurements along a vertical. An Ultrasound Velocity Profiler with three transducers. This device allows for two dimensional velocity measurements over a vertical. Additionally the UVP has been calibrated to perform suspended sediment concentration estimations. A peristaltic pump to extract suspended sediment samples at two different depths, for the calibration suspended sediment profiles. A pressure transducer connected to two ports at both ends of the tunnel, for global bed friction estimation.

A custom design sonar system has been installed to perform three dimensional surveys of the sand bed. Additional post-processing software to measure suspended sediment and generate synthetic stratigraphy is being developed. A camera connected to a computer to record the bed evolution is also dedicated to the experiments in the LOWST. Experiments are been performed routinely since the beginning of this work. First, exploratory experiments were carried to qualitatively explore the behavior of the selected sediment (250 µm sand). Later, experiments were performed to evaluate the performance and calibrate the installed measuring devices. Finally, a number of experiments to particularly study the bed response under different flow conditions have been performed. These experiments covered a wide range of flow conditions, including large near-bed excursions at different maximum orbital velocities. The collected data is currently being analyzed and compared with the compiled literature data. The new equipment installed in the LWCF and the experiments performed on that facility are reported in the companion Mine Burial by Local Scour and Sand Waves report. Part of the work performed in this facility can be found in Landry and Garcia (2007).

Discussion

The literature review on ripples gave a reference frame for the experimental program design. The preliminary analysis of the collected literature data and some of the performed experiments have shown that the parameters controlling the two or three dimensional configuration of the ripples are different for orbital and anorbital ripples. The particle size and the wave Reynolds number seem to be the controlling parameters in the case of regular ...