The air flow around a clothed cylinder. Part 1. An experiment on the outher flow field.

Abstract

An experiment was conducted for revealing the aerodynamic characteristics of cylinders clothed with fabrics. Pressure distributions on the outer and inner surfaces of cylinders and velocity distributions around these cylinders were measured. The results showed that the outer pressure distributions on the cylinders clothed with different fabrics were identical, but that they were different from that on a naked cylinder. This is because the air flow around the clothed cylinder separates from the surface earlier than that around the naked one. The inner pressure distribution were strongly affected by the fabrics of low permeability, but they were scarcely influenced in the case of high permeability. Measured velocity distributions indicated the forward shift of the separation point and they were found to be influenced seriously by the fabrics of high permeability; the boundary layer on the outer surface became thick and the turbulence level in the layer was high. In the case of low permeability, however, the velocity distribution was hardly influenced by clothing except the shift of the separation point.

Aerodynamic drag reduction in winter sports: The quest for “free speed”

“…37 Oggiano et al 32 also noted that in some sports, such as downhill skiing, the interaction between snow and skis can cause significant vibrations that can interact with flow-induced vibrations to cause an abrupt change in the wake state and drag on the body; 6. fabric air permeability and stretch-Nilsson et al 38 reported that at velocities of 42 m/s, fabric air permeability had little effect on the insulative value of clothing. Both Watanabe et al 39 and Holden 40 found that downhill ski suits with higher permeability had higher drag. Bardal and Reid 41 noted only a weak dependence of flow transition on air permeability in tests of fabric-covered cylinders.…”

1112 Aerodynamic Characteristics of Sports Apparel

“…Watanabe et al (1989) tested the pressure distribution around several fabric covered cylinders in a series of low velocity air flow tests (Re < 3 x 14). These authors found that the boundary layer was considerably thicker around a fabric of high air permeability (Tweed) than around a fabric of low permeability fabric (Denim) and that the point of flow separation was advanced to the wind facing region on all fabric covered cylinders.…”

The velocity distribution in the inner flow field around a clothed cylinder.

“…1, the details of which have velocity is the sum of the circumferential (0-) and radial (r-) velocity components. The cylinder was covered with various clothes in the same manner as described in the previous paper (1). Two adhesive tapes were inserted between the cylinder surface and the inner surface of the cloth to prevent the hot-wire from touching the cloth surface.…”

“…The clothes used as covering materials are knitted, tweed, flannel and denim fabrics, the details of which were given in the previous paper(1). The permeability was adopted to represent the aerodynamic characteristics of clothing materials as reported in the refrence (1). Reynolds number of the mean flow was 3.0 X 10" based on the diameter of the acrylic cylinder.…”

“…It was pointed out that the flow field could be divided into three regions: the outer field of the clothed cylinder, the field in the cloth, and the field between the inner surface of the cloth and the surface of the cylinder, and the first one of these, the outer flow field, had been mainly discussed. In the present study, the third region, i. e., the inner flow field, was investigated through a hot-wire anemometry similar to the one used in the previous experiment (1). The inner field corresponds to the contact layer that Takeuchi et al (2) first introduced and investigated as a field which might play an important role for the heat transfer of a clothed cylinder in a forced convective flow field.…”