Streamlined body for immersion in a liquid at high relative speed

Abstract

The invention is based on the objective of preventing cavitation on streamlined bodies which are immersed in a liquid ( 2 ) at high relative speed (v), permitting their use within wider speed ranges. To this purpose, in a transverse slot ( 4 ) a two-phase mixture of air and water is produced, which forms a two-phase mixture layer ( 9 ) downstream of the slot ( 4 ). The required air is supplied from an external source or precipitated from the air contained in the water in the transverse slot. Even without any air at all a water/water-vapor mixture layer is generated, which behaves in the manner of a two-phase mixture layer on account of the finely distributed vapor bubbles. The Reynold's number derived from the width of the slot ( 4 ) is greater than 20′000 .

1 . Streamlined body immersed in a liquid at high relative speed, embodying a slot ( 4 ) open towards the free-flowing stream, which slot runs largely perpendicular to the direction of flow (A) and in which a two-phase mixture of liquid ( 2 ) and gas ( 7 ) is formed, characterized such that the width (w) of the slot ( 4 ) open towards the free-flowing stream, as measured in the direction of flow (A), is of such dimension that the Reynold's number derived from this width (w) and the speed of flow (v) and the kinematic viscosity v of the liquid ( 2 ) is at least 20′000.  
     
     
         2 . Streamlined body according to  claim 1 , in which the depth (d) of the slot ( 4 ) measured perpendicularly to the direction of flow (A) is greater than the thickness of the boundary layer of the liquid stream immediately upstream of the slot.  
     
     
         3 . Streamlined body according to  claim 1  or  2 , in which the upstream flank ( 15 ) of the slot ( 4 ) meets the outer profile of the streamlined body as a sharp edge.  
     
     
         4 . Streamlined body according to one of the  claims 1  to  3 , in which the downstream flank ( 17 ) of the slot ( 4 ) merges with the outer profile of the streamlined body as a radiussed edge.  
     
     
         5 . Streamlined body according to one of the  claims 1  to  4 , in which it is additionally provided with a channel ( 5 ) for the controlled supply of a gas or a gas/liquid emulsion to the slot. ( 4 )  
     
     
         6 . Streamlined body according to one of the  claims 1  to  5 , in which it is provided with several slots ( 4 ) one behind the other in the direction of flow for the build-up of the two-phase mixture layer in stages.