GB2411816A

GB2411816A - Surface flow modifiers and swimsuits

Info

Publication number: GB2411816A
Application number: GB0405274A
Authority: GB
Inventors: Luc Bouckaert; Fiona Fairhurst
Original assignee: Speedo International Ltd
Current assignee: Speedo International Ltd
Priority date: 2004-03-09
Filing date: 2004-03-09
Publication date: 2005-09-14
Also published as: GB0405274D0

Abstract

The application describes new structures for influencing fluid flow over a fluid surface, particularly with a view to providing improved performance at the inside forearm of a swimsuit. Arrays of protuberances are described which are directional, having a unique maximum drag direction. They can be arranged on the inside forearm of a swimsuit (21) as a panel (1) having two regions (1a, 1b) whose maximum drag directions are oppositely oriented, to either side of a parting line (3) which leads movement of the arm through the water. In preferred embodiments the individual projections are crescent-shaped, with concave sides steeper than their convex side. They can be arranged in staggered rows.

Description

SURFACE FLOW MODIFIERS AND SWIMSUITS

This invention has to do with new structures for influencing fluid flow over a surface, particularly with a view to inducing turbulence in the fluid to affect drag, and to products and articles carrying such a structure on the surface. We particularly envisage its use in relation to swimsuits.

BACKGROUND

It has previously been proposed to apply shaped structures to the surface of a sporting garment, such as a cycling suit or swimming suit, to influence the flow of air or water over the suit in the athlete's favour. See for example US 5033116, US 5734990 and US 5836016.

Furthermore our own UP 1110464 disclosed a full body suit using a dimpled or heavily ribbed panel on the inside of the forearm, to help control flow past the swimmer's arm during swimming.

We now propose various new structures for surface flow modifiers, particularly in the context of swimsuits but also applicable in other contexts.

A first proposal is in the context of a swimsuit (which, for the avoidance of doubt, covers swimsuits having uses beyond swimming such as biathlon suits) having a region e.g. on an arm and/or leg of the suit carrying an array of flow-modifying projections. In this proposal the projections and array are directional, i.e. so that there is a direction for flow over the array corresponding to a maximum drag, with flow in the opposite relative direction giving a lesser or a minimum drag. In our first proposal the array is divided by a notional leading line into first and second portions lying to either side of the leading line. The maximum drag flow directions of the respective portions are aligned in opposition to one another, preferably directly in opposition i.e. parallel, and preferably perpendicular to the leading line. The leading line may be a straight line. There may be only two said portions. Preferably their directions of maximum drag face the leading line, i.e. so that for flow impacting that portion of the suit at the leading line, a turbulence, drag or resistance is maximized.

In particular, such an array may be provided on the inside forearm of a swimmer. The leading line may then extend along the approximate centre of the inside of the forearm, i.e. that part leading through the water in freestyle or butterfly swimming.

Elements in the array may conveniently be of the same shape. By making these elements having one face more abrupt or steeply sloping than an opposite face of the element, they have directional characteristics relative to flow. The elements may themselves conveniently be symmetrical (in plan) about this directional line, but this is not essential. Preferably the elements are arranged in a regular array, e.g. in rows, and preferably in staggered rows, which have been found to give optimal turbulence. Preferably each of said portions of the array, and/or the array as a whole, has at least 50 and more preferably at least 100 projecting repeat elements. Further optional and preferred features of these flow-modifying arrays are discussed below.

The second aspect of our proposals is a particular element structure for such a flow-modifying array. A first proposed feature, as mentioned above, is the directionality of the projecting elements of the array.

Typically this is represented by one or more faces or the entire face at the front of the element being inclined to the substrate surface less steeply than the oppositely directed rear face(s) of the element. For example one surface may typically be inclined at less than 45 to the substrate, the other at more. Respective angles of between 20 and 40 for one and between 50 and 70 for the other have been found good but these angles are not crucial; also the surfaces need not be planar or straight in cross-section. A second proposed feature is to form the projecting elements (as seen in plan) with a flat or concave side and a convex side, e.g. in a crescent shape.

The concave side is preferably the relatively abrupt side, and preferably uses a steeper surface as mentioned for the first feature above. The concave/convex structure can be achieved with linear contours, but the crescent or arcuate shape has good overall flow properties. (A

Preferably elements as discussed are arranged in rows, with the ends of each element (ends of the crescents) adjacent each other. Strongly preferably adjacent rows are staggered, with the centre of elements in one row aligned with the meeting or nearest approach of two adjacent elements in the next row. Or, the stagger may be less than half an element per row, but the half-element stagger is preferred.

A further refinement is to provide a further sub projection immediately in front of the concave leading face of each main projection. These further sub projections may have simple shapes, or they may themselves be concave/convex e.g. curved or crescent shaped projections which may match or correspond with the shape of the main element. They may have a line of symmetry aligned with that of the main element. In a preferred version a still further and smaller subsidiary element may project up e.g. in front of the mentioned sub-projection and this again may take a similar shape if wished.

In an array of rows of these projecting elements, with adjacent rows staggered, the space immediately in front of a main element is directed onto the junction or boundary between the two elements in the row in front.

This space naturally converges forwardly to that junction, because the surfaces are convex in plan. A series of one or more subsidiary projections of successfully smaller size can fit into this space in a forward sequence. This has been found to increase the creation of turbulence adjacent the surface among the projecting elements. This turbulence is such as to maximise drag for flow over the surface from the front (as described).

A surface formation as described is an independent aspect of the invention, irrespective of the substrate to which it is applied or on which it is formed. However we particularly envisage using it on fabric substrates for swimming costumes; in particular we envisage using it on a panel on a sleeve or leg of a swimsuit, particularly an inner forearm panel, and preferably with a bi-directional arrangement as described above for the first aspect.

Desirably the projections (at least for a sporting garment use) project less than 2 mm from the underlying surface. Preferred height is in the range 0.2 to 1.5 mm.

Obviously for other applications these dimensions may differ. The typical repeat width (i.e. across the predetermined flow direction) is preferably from 2 to 8 mm. The element length in the flow direction may be e.g. in the same range. This may apply also to the row to row spacing. Preferably adjacent elements are closely juxtaposed, e.g. with a spacing less than 0. 5 mm or less than 0.2 mm between adjacent elements.

Preferably the projecting elements are of polymeric material, and when applied to fabric substrates, distinct from the fabric and held onto it by a bond. Rubbery polymers are preferred, so that they can flex and stretch with the underlying fabric. Printing or embossing methods may be used for application of the elements.

Principles and examples are now described with reference to the accompanying drawings, in which: Fig. 1 shows an array of projecting elements; Fig. 2 shows array portions providing a "gripper" panel on the inside forearm of a swimsuit; Fig. 3 shows an element of the array in plane view enlarged; Fig. 4 shows a few elements of the array enlarged; Fig. 5 is a schematic cross-section perpendicular to the substrate for a single main element, and Fig. 6 is a schematic perspective view of a simplified version of the array constituting a variant; Figs. 7 and 9 show a further variant, and Figs. 8 and 10 show a still further variant.

With reference to Figs. 1 to 3, a swimsuit sleeve 21 carries on its inner forearm a local applied array 1 of repeating projecting elements 11. Each element 11 is made from a rubbery polymer bonded onto the stretch fabric surface. Considering them initially in plan, each element consists of a main projection 111, a secondary projection 112 and a tertiary projection 113. In this embodiment each of these has a crescent shape, their mirror axes being aligned, and arranged in decreasing order of size in front of the concave side of the main element 111. Preferred dimensions are a = 5 mm, b = 2.3 mm, c = 3 mm, d = 1.9 mm. In the array (see Fig. 1) each element 11 is positioned closely adjacent its neighbours, tip to tip (clearance 0.1 mm) in rows, the rows being staggered at the half length, and the forward tips of each of the secondary and tertiary elements approaching to within 0.1 mm of the outer convexity of the main element 11 in front. In the array applied to the swimsuit (Fig. 2) a first region la and a second region lb of the array are oppositely aligned around a median line 3 constituting a leading line or parting line. This is the anticipated position of the part of the arm leading its movement through the water. Flow over the array 1 is therefore expected to be in the directions marked A, B in Fig. 2, i.e. away from the parting line 3.

With reference to Fig. 5, showing one of the main elements 111, the concave face 14 is more steeply inclined than the convex face 15. In this embodiment the concave face (leading face) 14 inclines at 60 to the substrate, the convex trailing face at 30 . A forwardly angled crest 16 is provided at the top edge. Elements of this shape, and arranged in this kind of array, have been shown to produce selectively a greater drag for the flow direction onto the leading face, by means of induced turbulence. The height of the main element may be e.g. from 0.5 to 1.5 mm. The secondary and tertiary elements are progressively lower.

Fig. 4 shows parts of the two array regions la,lb adjacent the parting line 3. ( ) 8

Fig. 6 shows a simplified form of the array having only the main crescent elements 111, similarly arranged but without the secondary and tertiary elements filling in the intervening spaces. This still works, but the amount of drag is somewhat less.

Figs. 7 and 9 show an intermediate form with only a secondary crescent provided. The drag is better than in the Fig. 6 version. Figs. 8 and 10 show a further form with a tertiary element but in the form of a small stud or pimple, rather than a congruent crescent as in the first embodiment.

Claims

Claims 1. A swimsuit having a region, e.g. on an arm and/or leg portion of

the suit carrying a local array of flow modifying projections, in which the projections and array are directional so that there is a predetermined direction for flow over the array corresponding to a maximum drag, with flow in the opposite relative direction giving a lesser or minimum drag, and in which the array is divided by a leading line into first and second portions lying to either side of the leading line, the maximum drag flow directions of the respective portions being aligned in opposition to one another.
2. A swimsuit according to claim 1 in which the maximum drag flow directions of the respective portions are parallel.
3. A swimsuit according to claim 2 in which the maximum drag flow directions are perpendicular to the leading line.
4. A swimsuit according to any one of the preceding claims in which the leading line is a straight line.
5. A swimsuit according to any one of the preceding claims in which the local array is provided on an inner forearm region.
b. A swimsuit according to claim 5 in which the leading line extends along the inside of the forearm.
7. A swimsuit according to any one of the preceding claims in which the elements in the array have one face more abrupt or steeply sloping than the opposite face, to contribute to said directional drag flow characteristics.
8. A swimsuit according to claim 7 in which each of said portions of the array has at least fifty projecting repeat elements.
9. A swimsuit according to any one of the preceding claims in which projecting elements of the array are crescent-shaped.
10. A swimsuit according to claim 9 in which the concave sides of the crescent-shaped elements are more abrupt or steeply sloping than the convex sides thereof.
11. A swimsuit having a region, e.g. on an arm and/or leg of the suit, carrying an array of flow-modifying projections, in which array the projections and array are directional so that there is a predetermined direction for flow over the array corresponding to a maximum drag, with flow in the opposite relative direction giving a lesser or minimum drag, and wherein one or more faces at aligned fronts of the projecting elements are inclined the swimsuit surface less steeply than oppositely- directed rear faces of the elements.
12. A swimsuit according to claim 11 in which the projecting elements seen in plan have a crescent shape, with the concave side of the crescent being steeper than the convex side.
13. A swimsuit according to claim 12 in which, in the array, subprojections protrude immediately in front of the concave leading faces of the crescent projections.
14. A swimsuit according to claim 13 in which the sub projections have lines of symmetry aligned with those of the main crescent projections.
15. A swimsuit according to claim 14 in which the sub projections are themselves crescent-shaped.
16. A swimsuit according to any one of the preceding claims in which the projections of the array are provided in rows, and projection in successive rows are staggered relative to one another, with respect to the maximum drag direction.
17. A swimsuit according to any one of the preceding claims in which the projecting elements are of polymeric material.
18. A swimsuit or surface flow modifier substantially as described herein with reference to the accompanying drawings.