DROPLET DYNAMICS NEAR THE WALL IN A VERTICAL RECTANGULAR DUCT

Measurements of the droplet behavior near the wall in a vertical recta ngular duct were conducted by a phase Doppler particle analyzer (PDPA) . The test Reynolds number and drop size range is from 18,500 to 89,30 0 and from 5 mum to 110 mum, respectively. Results show that the negat ive slip-velocity of the drops near the free-stream region normally re sults in the reversed slip-velocity phenomenon in the boundary layer r egion. No negative slip-velocity of all drops are discovered for Reyno lds number less than 38,300. This indicates no reversed slip-velocity phenomenon for the test drop size range under low Reynolds number cond itions. However, when the Reynolds number is over 38,300, the free-str eam slip-velocity of the bigger drops becomes negative. It is found th at the negative slip-velocity and, hence, the reversed slip-velocity p henomenon may take place for drop size larger than 52 mum to 90 mum de pending on the flow Reynolds number.