Effects on miniature filament on flow characteristics

Abstract

In this Final Year Project (FYP), fabrics of varying composition, orientation and elongations were investigated in a wind tunnel. The fabric samples were attached to a cylinder mimicking a bluff body. These tests were conducted over a range of speeds in the wind tunnel. The analysis of these results then done using the surface morphology and the surface texture parameters, employing both the use of a stereo microscope and a profilometer.

The wind tunnel results obtained showed an increasing minimal C_d and an earlier transition Re as the fabric was stretched. Taking the 75% polyester fabric as example, the minimal C_d increased from 0.188 to 0.250 as the fabric was stretched from 0% to 50% stretch. The same fabric also showed an increase in surface texture, having an S_q of 27.1μm at 25% stretch to 28.3μm as at 50% stretch. These two results showed similar trends and were concluded to be closely related. These trends were also observed in the other fabrics tested. The worst performing fabric, the 80% nylon, was thusly observed to have a larger minimal C_d of 0.320 and a higher S_q measurement of 35.8μm. This results thus highlighted how the surface texture affect the aerodynamic properties.

Lastly, recommendations were given to investigate new areas of study to further explain and quantify the change in aerodynamic properties of fabric as it varied in composition, elongation, and orientation.