Experimental analysis of turbulence effect in settling velocity of suspended sediments

Abstract

SETTLING VELOCITIES OF SEDIMENT PARTICLES FOR DIFFERENT SIZE RANGES WERE MEASURED IN THIS WORK USING PIV WITH THE HELP OF DISCRIMINATORY FILTERS. AN EXPERIMENTAL CHANNEL 10'15 CM CROSS SECTION WAS USED IN ORDER TO OBTAIN TWO SET OF TURBULENT CHARACTERISTICS CORRESPONDING WITH TWO DIFFERENT FLOW RATES. THE PURPOSE WAS TO ANALYZE THE EFFECT OF TURBULENCE ON THE SOLIDS SETTLING VELOCITY. THE TECHNIQUE AL LOWED US TO MEA SURE THE INDIVIDUAL SETTLING VELOCITY OF THE PARTICLES AND THE FLOW VELOCITY FIELD OF THE FLUID. CAPTURE AND IMAGE ANALYSIS WAS PER FORMED WITH DIGITAL CAMERAS (CCD) USING THE SOFT WARE SHARP-PROVISION PIV AND THE STATISTICAL CROSS CORRELATION TECHNIQUE. RESULTS SHOWED THAT SETTLING VELOCITY OF PARTICLES IS AFFECTED BY TURBULENCE WHICH ENHANCES THE FLUID DRAG COEFFICIENT. PHYSICALEXPLANATION OF THIS PHENOMENON IS RELATED WITH THE MAGNITUDE OF THE VERTICAL FLUCTUATING VELOCITY OF THE FLUID. HOW EVER, MORE RESEARCH IS NEEDED IN ORDER TO DE FINE SETTLING VELOCITY FORMULAS THAT TAKES INTO ACCOUNT THIS EFFECT.