IMPROVING FLUID FLOW IN TUBING

Abstract: There is disclosed a method for configuring or reconfiguring branches in tubing in which the axes of at least two components of the branched structure are arranged askew.

Description: Improving Fluid Flow in Tubing This invention relates to fluid flow in tubes, particularly, but by no means essentially, blood flow tubing and other tubing carrying fluids essential to life. In WO 00/38591 is described tubing adapted to induce helical flow in such fashion as to eliminate or reduce turbulence and/or eliminate or reduce dead flow regions in the tubing. The tubing has internal helical grooving or ridging or other measures designed having regard to the dimensions of the tubing and the density, viscosity and velocity of the flow. Particular problems arise in connection with branched tubing, in which fluid flows from a main trunk into two or more branches, or, alternatively, flows from two or more branches into a main trunk. Certain blood carrying vessels as well as air passages in human or animal bodies experience such branching. When such branched tubing is repaired or replaced, as in vascular grafting, heart bypasses and so forth, it may be advantageous to reconfigure such tubing to improve fluid flow at such branch. One way of reconfiguring the tubing would be to introduce helical ridging or grooving in the manner taught in WO 00/38591, but this is not always possible. The present invention provides a method for configuring or reconfiguring branches in tubing to improve fluid flow at or in the region of such branches. The invention comprises a method for configuring or reconfiguring branches in tubing in which the axes of at least two components of the branched structure are arranged skew. The axis of a circular section tube is, of course, well defined. More generally, the axis of a non-circular section tube is taken for present purposes to be the locus of the centres of gravity of adjacent lengthwise slices through the lumen of the tube. An axis may, then, not be a straight line, as the branch may be curved. At least one of the components of the branched structure may itself have internal helical configuration adapted to reduce or eliminate turbulence and/or dead regions in the flow, and this may be adapted to cooperate with the skew arrangement of any components of the branched structure - if, for example, the skew arrangement is intended to produce a clockwise rotary component in the flow, viewed along the direction of flow, then the internal helical configuration of at least one component of the branched structure may also be arranged to produce a clockwise component. To avoid the creation of incidental turbulence, it may be arranged that internal surfaces of the branched structure are themselves smooth and that there are no sharp edges. Embodiments of branched tubular configurations according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is an elevation of a first embodiment; Figure 2 is a view on Arrow 2 of Figure 1 ; Figure 3 is a view on Arrow 3 of Figure 1; and Figure 4 is a lengthwise section through a second embodiment. The drawings illustrate methods for configuring branched tubular structures 11, each comprising a main trunk portion and two branches. Figures 1 to 3 illustrate a structure in which fluid flow is into the main trunk 12 from two branches 13. The offset arrangement of the branches 13 causes rotational flow in the main trunk 12, as indicated by the flow arrows. As the general idea is to reduce or eliminate turbulence and/or dead spaces, the branched structure will need to be configured as to the dimensions of the tubes, especially the relative flow capacities of the trunk 12 and branches 13, the viscosity and density of the fluid flowing in them and the flow velocities, to optimise the flow characteristics. It may be that this can all be worked out by computational fluid dynamics, or it may be dealt with on a trial and error basis in which a range of configurations is investigated. Figure 4 illustrates a branched structure in which the fluid is flowing from the main trunk 12 into the branches 13. Here, the flow is prepared in advance of the junction to have a rotational component in the correct sense by means of internal helical ridging and/or grooving 14 in the inner wall of the trunk 12. Of course, structures of more complex geometry can be contemplated, for example a trunk dividing into three or more branches, a structure in which two or more branches flow into two or more further branches, and so forth, all of which can be dealt with by offsetting the branches as above described. The invention may have particular relevance in relation to tubing in which body fluids flow, such for example as veins and arteries, for the avoidance or reduction of tendency to atherosclerosis and the formation of clots that can break away leading to strokes. The design of artificial vascular grafts and particularly patches for coronary bypass surgery may benefit from the teachings herein. A particularly important branched structure is the respiratory system, and, while surgical intervention may not bring about structures that were not already in place, at least the teachings herein may serve to avoid the creation of structures which create unwanted turbulence and/or dead spaces in the system. The invention, however, will find many applications outside of the clinical field, in, for example, the design of pipework in manufacturing plant, in oil delivery pipelines and in air conditioning and central heating systems.

Claims: CLAIMS 1. A method for configuring or reconfiguring branches in tubing in which the axes of at least two components of the branched structure are arranged askew. 2. A method according to claim 1, in which at least one of the components of the branched structure itself has an internal helical configuration adapted to reduce or eliminate turbulence and/or dead regions in flow through the tubing. 3. A method according to claim 2, in which the said internal helical configuration is adapted to co-operate with the skew arrangement. 4. A method according to any one of claim 1 to 3, in which internal surfaces of the branched structure are configured or reconfigured to be smooth, with no sharp edges. 5. Tubing configured or reconfigured according to a method according to any one of claims 1 to 4. 6. Tubing according to claim 5, being blood flow tubing.

Inventors: DICK JOHN B C, HOUSTON J GRAEME, STONEBRIDGE PETER A, DICK, JOHN, B., C.,, HOUSTON, J., GRAEME, STONEBRIDGE, PETER, A.
Applicants: DICK JOHN B C, HOUSTON J GRAEME, STONEBRIDGE PETER A, TAYSIDE FLOW TECHNOLOGIES LTD, DICK, JOHN, B., C.,, HOUSTON, J., GRAEME, STONEBRIDGE, PETER, A., TAYSIDE FLOW TECHNOLOGIES LIMITED
Application year: 2001
Main classification: A61F
IPC codes: A61F2