WO1991001247A1 - Fluid dynamic surfaces - Google Patents
Fluid dynamic surfaces Download PDFInfo
- Publication number
- WO1991001247A1 WO1991001247A1 PCT/CA1990/000228 CA9000228W WO9101247A1 WO 1991001247 A1 WO1991001247 A1 WO 1991001247A1 CA 9000228 W CA9000228 W CA 9000228W WO 9101247 A1 WO9101247 A1 WO 9101247A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- blade
- depressions
- fluid
- present
- blades
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
- B63B1/32—Other means for varying the inherent hydrodynamic characteristics of hulls
- B63B1/34—Other means for varying the inherent hydrodynamic characteristics of hulls by reducing surface friction
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
- B63B1/32—Other means for varying the inherent hydrodynamic characteristics of hulls
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
- B63B1/32—Other means for varying the inherent hydrodynamic characteristics of hulls
- B63B1/34—Other means for varying the inherent hydrodynamic characteristics of hulls by reducing surface friction
- B63B1/36—Other means for varying the inherent hydrodynamic characteristics of hulls by reducing surface friction using mechanical means
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T70/00—Maritime or waterways transport
- Y02T70/10—Measures concerning design or construction of watercraft hulls
Definitions
- the present invention relates to a device for improving fluid flow across a surface by changing frictional drag effects usually inherent in fluid dynamics. Interior and exterior surfaces adjacent fluids are subject to the non-slip conditions of flow which directly result in the slow down of relative fluid velocity. Great amounts of energy are required to overcome such frictional drag and therefore improving fluid flow velocities would result in improved efficiency.
- axial flow through a marine screw has two main characteristics, namely the diameter of the axial flow and the speed of the axial flow. The larger the diameter of the axial flow and the higher the axial flow velocity, the greater the amount of "push power" or thrust that will be available.
- Screw diameter or perhaps more appropriately "apparent diameter", since it is actually a relationship depending on the amount of active blade surface, pushing or driving surface area that is in issue, depends on actual blade diameter and the number of blades. Increasing either has the effect of concomitantly increasing the amount of frictional drag. It is obvious that the suction side of a blade performs a different function from the driving side, in fact the driving side surface of the blade relies on resistance and surface friction to provide thrust. It is therefore the suction surface side of the blade that is adversely effected by frictional drag and in extreme cases, if the required fluid velocity cannot be maintained over the suction surface to replace fluid displaced by the driving surface, cavitation will occur. Streamlining of the blade face is the approach traditionally taken in order to help control flow behaviour over the suction surface.
- the patent associates this problem with blade failure and excessive noise production, as well as loss of efficiency.
- the patent also discloses the use of blade surface discontinuities arranged along the downstream facing, stator blade surfaces, which discontinuities are effective in dispersing or attenuating pressure waves (with concomitant cavitation effects) reflecting from a succeeding stage of rotar blades.
- the discontinuities are described variously as grooves, ridges protuberances, dimples, or perforated cover plates or elastic, force-absorbing blade overlays.
- the scope of the present invention generally embraces all non-spherical surfaces adapted to be positioned adjacent a fluid moving relative thereto.
- the surfaces include blind, ' discrete surface depressions arranged in a symmetrical pattern over a portion of the surface.
- blind discrete surface depressions includes any shape of surface depression which is blind in the sense that it does not communicate through the surface with an opposite side thereof. Accordingly, slots extending through an airfoil are not within the contemplation of the present invention.
- the surface depressions include discrete, generally spheroidal or spherical concave subsurfaces extending below the surface.
- Generally spherical shapes are especially preferred, although both oblate and prolate shapes are also contemplated.
- Regular shapes have the advantage of dealing uniformly with changing flow patterns, or in other words, are independent of the angle the flow takes across the surface. While not wishing to be necessarily bound to any particular theory of operation it is believed, and this belief forms the basis for at least one aspect of the present invention, that improved fluid velocity over surfaces can be realized by including a device on a surface adapted to be positioned adjacent a fluid in relative motion thereto, with the device being operable to improve fluid flow velocity by changing the boundary layer pattern proximal the surface.
- the surface is arranged with depressions in pattern, which, when in relative motion adjacent a fluid, provides, in the direction of flow, continuous interruptions at the boundary layer level, causing continuous
- the present invention has a broad range of applications.
- the surface is moving and the fluid
- the movement of the fluid provides the relative motion between the surface and the fluid.
- Applications of this type include flow directing surfaces, as in the case of nozzles used in turbomachines.
- Other examples include
- a further example of application of the present invention is an exterior surface of a covering means both
- Yet another example of application of the present invention relates to a surface adjacent a matter other than a fluid, such as the surface of a ploughshear, a cutting knife or a sawblade and the like.
- a surface adjacent a matter other than a fluid such as the surface of a ploughshear, a cutting knife or a sawblade and the like.
- Such surfaces when smooth are subject to great frictional surface drag during operation and reducing such drag would result in improved operation and energy efficiency.
- both the surface and the fluid are moving in generally opposite directions such as in the application of machine surfaces adapted to ingage fluid in a drive connected relation.
- This category includes fluid couplings, continuously lubricated bushings and bearings, propellers, impellers and the like.
- the invention has advantages especially when used in association with rotating blades, generally.
- the present invention provides benefits in the field of aircraft propellers and marine screws, wherein little or no advance has been made in the way of fundamental improvements in operating efficiency for over half a century.
- the desired condition is for the suction surface of a blade to achieve a reduction in frictional drag and increasing fluid velocity towards the rear or driving side of the blade, therefore increasing operating efficiency and decreasing the likelihood of cavitation occurring.
- the solution in accordance with this aspect of the present invention is to provide continuous interruption of the frictional surface drag normally present between the boundary layer and the immediately adjacent laminar flow sublayer, so as to, surprisingly, minimize the drag coefficient of the blade surface.
- an improved turbomachine blade comprising a blade having a symmetrical pattern of surface depressions arranged over the suction side surface thereof.
- the surface depressions are operable with the blade in use to substantially interrupt the frictional drag across the suction surface.
- Figure 1 of the drawings appended hereto depicts a preferred embodiment of the present invention, comprising a symmetrical pattern of discrete spherical depressions on a surface in plan view;
- Figure 2 of the drawings depicts a section through a surface depicted in Figure 1 and illustrating the concave depression arrangment
- Figure 3 of the drawings depicts another embodiment of the present invention, comprising a two-bladed marine screw, shown in an elevated view, and having depressions arranged on the suction side thereof;
- Figure 4 of the drawings depicts a longitudinal cross section through the uppermost blade depicted in Figure 3 and illustrating the concave depression arrangement along the suction side of that blade;
- Figure 5 of the drawings is a graphical representation of the performance of two commerical propellers n comparison with a propeller of the present invention; and in particular a two-bladed propeller having surface depressions arranged on the suction side of the blades thereof;
- Figure 6 of the drawings is a further comparison of the relative performance of the propellers which are described in relation to Figure 5, but taking into account the effect of overall propeller size differences;
- Figure 7 of the drawings is yet another comparison of the relative performance of the propellers dealt with in relation to Figure 5 and 6, this time taking into account the effects of the differences in blade area between the blades under consideration.
- FIG. 1 of the drawings there is shown a surface area 1 in plan view, including a typical symmetrical pattern arrangement of a plurality of discrete, spherical depressions 2, with the relative fluid motion direction as indicated by arrow 3.
- the depressions 2 present surface interruptions of substantially equal shape and proportion to all directions of fluid flow across the surface.
- Figure 2 of the drawings shows an elevated side view through a section of the surface 1, indicating shape and proportion of surface depression 2 relative to the remaining level 4 when the depression is measured at its opening 5.
- area 4 to area 5 depends on the actual application and may vary according to type of surface, type and relative velocity of fluid. For best results however, area 4 should not be more than 50% or less than 5% of area 5.
- FIG. 3 of the drawings shows in an elevated front view, a marine screw 6 of the present invention, including two blades 7, arranged in generally equally spaced apart relation about a common hub 8.
- Each of the blades 7 includes a plurality of surface depressions 2, arranged over the suction side 7a of such blades.
- Hub 9 is engaged in driven relation and known manner on a keyed drive shaft 10. The resulting assembly is adapted to rotate in the direction indicated by arrows 11.
- Figure 4 of the drawings is an elevated side view through a longitudinal section of the marine screw blade of the present invention, taken substantially as indicated in Figure 3 through section line "A-A 1 .
- Figure 4 of the drawings shows the embodiment in which the suction side 7a of blade 7 includes a plurality of surface depressions 2. The direction of travel of the embodiment is indicated by
- Figures 3 and 4 of the drawings show the embodiment of the present invention as it was actually tested for the purposes of comparison as set forth in the description of Figures 5, 6 and 7 below.
- Figure 5 of the drawings is a graph comparing the efficiencies of three different marine screws, coded A, B and C respectively. Note that the same coding is used in presenting the data as illustrated in Figures 6 and 7.
- Marine screw A was manufactured by Evinrude and is a two-bladed screw, having 101 square centimeter blade area and a water contact area of 291 square centimeters. This is the largest of the three marine screws for which data is presented.
- Marine screw B is an embodiment of the present invention, in the form of a two-bladed screw, having only a 30 square centimeter blade area and a 119 square centimeter water contact area.
- Marine screw C was modelled after a Mercury marine screw and was a three-bladed arrangement having an 83 square centimeter blade area and a 249 square centimeter water contact area.
- blade area means the actual total combined size of the blade area, (i.e. number of blades times the area of the blades), and water contact area means the total rotational area of the screw less the area taken up by the screw's hub.
- Figure 6 of the drawings depicts the relative efficiency of the same three marine screws, this time taking into account the total water contact area, which is a function of the diameter of the screw.
- the present invention outperformed the next most efficient, marine screw C, by slightly more than 180%.
Abstract
A device to improve flow characteristics of fluids adjacent non-spherical surfaces in relative motion thereto, said surfaces are provided with a plurality of discrete depressions, arranged so as to change the boundary layer pattern, causing interruptions in frictional surface drag and thereby reducing frictional surface drag.
Description
FLUID DYNAMIC SURFACES
BACKGROUND OP THE INVENTION
The present invention relates to a device for improving fluid flow across a surface by changing frictional drag effects usually inherent in fluid dynamics. Interior and exterior surfaces adjacent fluids are subject to the non-slip conditions of flow which directly result in the slow down of relative fluid velocity. Great amounts of energy are required to overcome such frictional drag and therefore improving fluid flow velocities would result in improved efficiency.
Although the scope of the present invention embraces all surfaces adjacent fluids, one aspect relates to marine screw and propeller applications. Broadly speaking, axial flow through a marine screw has two main characteristics, namely the diameter of the axial flow and the speed of the axial flow. The larger the diameter of the axial flow and the higher the axial flow velocity, the greater the amount of "push power" or thrust that will be available.
The axial flow diameter is controlled through screw design. Screw diameter, or perhaps more appropriately "apparent diameter", since it is actually a relationship depending on the amount of active blade surface, pushing or driving surface area that is in issue, depends on actual blade diameter and the number of blades. Increasing either has the effect of concomitantly increasing the amount of frictional drag. It is obvious that the suction side of a blade performs a different function from the driving side, in fact the driving side surface of the blade relies on resistance and surface friction to provide thrust. It is therefore the suction surface side of the blade that is adversely effected by frictional drag and in extreme cases, if the required fluid velocity cannot be maintained over the suction surface to replace fluid displaced by the driving surface, cavitation will occur. Streamlining of the blade face is the approach traditionally taken in order to help control flow behaviour over the suction surface.
However, streamlining has some inherent limitations.
Streamlining can only be optimally responsive to a single set of operating conditions, and does not respond to changes in such conditions. Streamline design is extremely application specific too, so that the blade faces must be designed for each different application in order to preserve the optimum advantages available through streamline design. US 4,720,239, deals with a problem that is encountered in turbine type turbomachines which utilize adjacent pairs of cascaded rotor and stator blades. The problem itself is quite old and is described in Principles of Turbomachinery, Shepherd, 1956, page 178. This test describes a "pressure defect" corresponding to the regions close to the trailing edges of the blade wakes. The flow between the stator blades is not uniformly deflected or redirected, and this non-uniformity concentrates its effects in the wakes formed behind the blades. In addition to the energy losses that result from the turbulent wakes themselves, there are additional undesirable downstream effects, especially in relation to the succeeding row of blades. The test points out that the local conditions in the blade wakes give rise to vibration of the succeeding row of blades. US 4,720,239 describes the same problem in relation to pressure waves propagated circumferentially with respect to the stator, either rotationally or counterrotationally to the machine's rotation. Reflecting pressure waves are taught by this patent to result in transient or even sustained flow separation from the blades in the vicinity of their trailing edges. This patent associates this problem with blade failure and excessive noise production, as well as loss of efficiency. The patent also discloses the use of blade surface discontinuities arranged along the downstream facing, stator blade surfaces, which discontinuities are effective in dispersing or attenuating pressure waves (with concomitant cavitation effects) reflecting from a succeeding stage of rotar blades. The discontinuities are described variously as grooves, ridges protuberances, dimples, or perforated cover plates or elastic, force-absorbing blade overlays.
E SHEET
The second of the abovementioned US patents is US 1,943,934, which pertains to marine screw propellers. This patent teaches the use of grooves, knurlings, scorings or the like on or adjacent the leading edge, on the driving face of the blades. The patent discloses that this modification operates as a brake, curtailing high initial velocities over the driving, or back, face of the blade, that would otherwise produce localized suction and hence cavitation along that face. The patent teaches that this will have the effect of more uniformly distributing suction over the back of the blade thereby producing a gradual transition from the suction at the leading edge thereof to the absolute pressure at the trailing edge thereof. The degree of roughness is taught as being that needed to avoid the formation of vacuous cavities.
Notwithstanding the foregoing, the accepted practice in the art for dealing with cavitation problems involves the use of so-called super-cavitating propellers which can be traced at least as far back as the 1920s. These propellers have blunt, squared trailing edges, so vapour pockets don't collapse, and there is no cavitation induced hammering on the blade surfaces. Since the problem is for the most part confined to high speed operation, these blades are typically found only on propeller driving racing boats. While the avoidance of structural damage resulting from cavitation is a laudable objective, there remains a continuing need in the art for general improvements in efficiency beyond what might incidentally arise in conjunction with the correction of cavitation problems. Shepherd, supra, teaches at page 165 of his test that it is apparent that conditions for a blade section should attempt to approach those for laminar flow over a flat plate, as this gives the lowest possible drag coefficient. Such a state of affairs is obviously impossible because (1) blades must have curvature in order to change the direction of the fluid, and thereby introduce a pressure gradient and a tendency towards flow separation, (2) blades must be a finite thickness from considerations of strength, and (3)
TE SHEET
because the fluid usually has a high turbulence level. These factors impose serious limitations on the efficiency of, for example, marine screw designs.
SUMMARY OF THE INVENTION The scope of the present invention generally embraces all non-spherical surfaces adapted to be positioned adjacent a fluid moving relative thereto. In accordance with the present invention the surfaces include blind,' discrete surface depressions arranged in a symmetrical pattern over a portion of the surface. As used in the context of the present disclosure, the term "blind discrete surface depressions" includes any shape of surface depression which is blind in the sense that it does not communicate through the surface with an opposite side thereof. Accordingly, slots extending through an airfoil are not within the contemplation of the present invention.
Preferably the surface depressions include discrete, generally spheroidal or spherical concave subsurfaces extending below the surface. Generally spherical shapes are especially preferred, although both oblate and prolate shapes are also contemplated. Regular shapes have the advantage of dealing uniformly with changing flow patterns, or in other words, are independent of the angle the flow takes across the surface. While not wishing to be necessarily bound to any particular theory of operation it is believed, and this belief forms the basis for at least one aspect of the present invention, that improved fluid velocity over surfaces can be realized by including a device on a surface adapted to be positioned adjacent a fluid in relative motion thereto, with the device being operable to improve fluid flow velocity by changing the boundary layer pattern proximal the surface.
Preferably, the surface is arranged with depressions in pattern, which, when in relative motion adjacent a fluid, provides, in the direction of flow, continuous interruptions at the boundary layer level, causing continuous
TE SHEET
interruptions of frictional surface drag between such boundary layer and the immediately adjacent laminar flow sublayer.
This results in improvements in fluid flow velocities
5 and therefore in improvements in energy efficiency.
In fact, a blunt body equipped with a smooth exterior surface, when travelling through fluid, drags behind a large low pressure area. Frictional surface drag reduces fluid flow velocity over its surface to such a degree as to
16 prevent fluid from reaching said low pressure area in time to re-fill it. This results in major additional energy consumption. The same body with a surface equipped with the device according to the present invention could show an increase of energy efficiency of up to 500%. However, the
15 more streamlined the shape of the body, the less drastic the effect.
As already mentioned, the present invention has a broad range of applications. In accordance with one aspect of the invention, for example, the surface is moving and the fluid
20 is generally stationary. Examples of this aspect of the invention include exterior surfaces of airborne, waterborne, land, rail and space vehicles. Within the contemplation of the present invention, this would include particularly applications on exterior surfaces of vessels, both above and
25 especially below the waterline, submarines and torpedoes, aircrafts, ballistic bodies, missiles, simple projectiles, high speed rail vehicles, trucks and other land vehicles. In addition to the foregoing the applications of the present invention are not necessarily restricted to use in
30 connection with moving bodies. In one aspect of the invention the movement of the fluid provides the relative motion between the surface and the fluid. Applications of this type include flow directing surfaces, as in the case of nozzles used in turbomachines. Other examples include
- - interior surfaces of fluid conduits such as pipelines, exhaust and intake manifolds and the like.
A further example of application of the present invention is an exterior surface of a covering means both
SUBSTITUTE SHEET
flat or with curvature such as on structures, buildings and towers.
Yet another example of application of the present invention relates to a surface adjacent a matter other than a fluid, such as the surface of a ploughshear, a cutting knife or a sawblade and the like. Such surfaces when smooth are subject to great frictional surface drag during operation and reducing such drag would result in improved operation and energy efficiency. in another aspect of the invention, both the surface and the fluid are moving in generally opposite directions such as in the application of machine surfaces adapted to ingage fluid in a drive connected relation. This category includes fluid couplings, continuously lubricated bushings and bearings, propellers, impellers and the like. The invention has advantages especially when used in association with rotating blades, generally. In particular, the present invention provides benefits in the field of aircraft propellers and marine screws, wherein little or no advance has been made in the way of fundamental improvements in operating efficiency for over half a century.
It has been found in connection with the present invention, and this finding forms the basis for one aspect thereof, that improved operating efficiency of turbomachine blades can be realized by changing the boundary layer pattern of the surface on the suction side of the blade.
The desired condition is for the suction surface of a blade to achieve a reduction in frictional drag and increasing fluid velocity towards the rear or driving side of the blade, therefore increasing operating efficiency and decreasing the likelihood of cavitation occurring.
The solution in accordance with this aspect of the present invention is to provide continuous interruption of the frictional surface drag normally present between the boundary layer and the immediately adjacent laminar flow sublayer, so as to, surprisingly, minimize the drag coefficient of the blade surface.
In accordance therefore, without being limited by any
STITUTE SHEET
particular theory of operation or effect, there is provided, as one aspect of the present invention, an improved turbomachine blade, comprising a blade having a symmetrical pattern of surface depressions arranged over the suction side surface thereof. The surface depressions are operable with the blade in use to substantially interrupt the frictional drag across the suction surface. Experimental work in this regard has demonstrated that there is a highly surprising degree of increased blade efficiency.
INTRODUCTION TO THE DRAWINGS
Figure 1 of the drawings appended hereto depicts a preferred embodiment of the present invention, comprising a symmetrical pattern of discrete spherical depressions on a surface in plan view;
Figure 2 of the drawings depicts a section through a surface depicted in Figure 1 and illustrating the concave depression arrangment;
Figure 3 of the drawings depicts another embodiment of the present invention, comprising a two-bladed marine screw, shown in an elevated view, and having depressions arranged on the suction side thereof;
Figure 4 of the drawings depicts a longitudinal cross section through the uppermost blade depicted in Figure 3 and illustrating the concave depression arrangement along the suction side of that blade;
Figure 5 of the drawings is a graphical representation of the performance of two commerical propellers n comparison with a propeller of the present invention; and in particular a two-bladed propeller having surface depressions arranged on the suction side of the blades thereof;
Figure 6 of the drawings is a further comparison of the relative performance of the propellers which are described in relation to Figure 5, but taking into account the effect of overall propeller size differences;
Figure 7 of the drawings is yet another comparison of the relative performance of the propellers dealt with in relation to Figure 5 and 6, this time taking into account
the effects of the differences in blade area between the blades under consideration.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to Figure 1 of the drawings, there is shown a surface area 1 in plan view, including a typical symmetrical pattern arrangement of a plurality of discrete, spherical depressions 2, with the relative fluid motion direction as indicated by arrow 3. The depressions 2 present surface interruptions of substantially equal shape and proportion to all directions of fluid flow across the surface.
Figure 2 of the drawings shows an elevated side view through a section of the surface 1, indicating shape and proportion of surface depression 2 relative to the remaining level 4 when the depression is measured at its opening 5. The relationship of area 4 to area 5 depends on the actual application and may vary according to type of surface, type and relative velocity of fluid. For best results however, area 4 should not be more than 50% or less than 5% of area 5.
Figure 3 of the drawings shows in an elevated front view, a marine screw 6 of the present invention, including two blades 7, arranged in generally equally spaced apart relation about a common hub 8. Each of the blades 7 includes a plurality of surface depressions 2, arranged over the suction side 7a of such blades. Hub 9 is engaged in driven relation and known manner on a keyed drive shaft 10. The resulting assembly is adapted to rotate in the direction indicated by arrows 11.
Figure 4 of the drawings is an elevated side view through a longitudinal section of the marine screw blade of the present invention, taken substantially as indicated in Figure 3 through section line "A-A1. Figure 4 of the drawings shows the embodiment in which the suction side 7a of blade 7 includes a plurality of surface depressions 2. The direction of travel of the embodiment is indicated by
SUBSTITUTE SHEET
arrow 12. Figures 3 and 4 of the drawings show the embodiment of the present invention as it was actually tested for the purposes of comparison as set forth in the description of Figures 5, 6 and 7 below. Figure 5 of the drawings is a graph comparing the efficiencies of three different marine screws, coded A, B and C respectively. Note that the same coding is used in presenting the data as illustrated in Figures 6 and 7.
Marine screw A was manufactured by Evinrude and is a two-bladed screw, having 101 square centimeter blade area and a water contact area of 291 square centimeters. This is the largest of the three marine screws for which data is presented.
Marine screw B is an embodiment of the present invention, in the form of a two-bladed screw, having only a 30 square centimeter blade area and a 119 square centimeter water contact area.
Marine screw C was modelled after a Mercury marine screw and was a three-bladed arrangement having an 83 square centimeter blade area and a 249 square centimeter water contact area.
As these terms are employed in this disclosure, blade area means the actual total combined size of the blade area, (i.e. number of blades times the area of the blades), and water contact area means the total rotational area of the screw less the area taken up by the screw's hub.
In gathering the data depicted herein, the marine screws were each in turn attached to a direct current electric marine motor in a water filled test tank. Figure 5 of the drawings illustrates the comparative efficiencies of the three above-mentioned marine screws under low and high speed operating conditions. High speed operating efficiency is in each case shown with the cross hatched bars, while low speed efficiencies are shown in the overlaying plain bars. While each marine screw showed improved efficiency at higher operating speeds, the marine screw according to the present invention consistently outperformed both the much larger marine screw A and the
SUBSTITUTE SHEET
three bladed marine screw C. On average, marine screw B was almost 14.6% more efficient than the average performance of the next best performing screw, marine screw C, without taking into account any differences in the size of the two blades.
Figure 6 of the drawings depicts the relative efficiency of the same three marine screws, this time taking into account the total water contact area, which is a function of the diameter of the screw. In this comparison, the present invention outperformed the next most efficient, marine screw C, by slightly more than 180%.
Finally, as shown in Figure 7, when only the total blade area is considered, the screw of the present invention outperformed marine screw C by over 360%. Moreover, note that the screw of the present invention was surprisingly more efficient at low speed than at high speed. This clearly demonstrated that the benefits of the present invention are not necessarily attributable to avoiding cavitation effects, which would be more likely to manifest at high rather than at low speed operation.
Claims
1. A device to improve flow characteristics of fluids adjacent non-spherical surfaces in relative motion thereto, said surfaces are provided with a plurality of discrete depressions, arranged to change the boundary layer pattern, causing interruptions in frictional surface drag and thereby reducing frictional surface drag.
2. A device according to claim 1 wherein said surface depressions are spherical in shape.
3. A device according to claim 1 wherein said surface depressions are other than spherical in shape.
4. A device according to claim 1 wherein said surface depressions are arranged in a symmetrical pattern.
5. A device according to claim 1 wherein said surface depressions are arranged in an asymmetrical pattern.
6. A device according to claim 1 wherein said relative fluid motion across the surface exceeds the motion against the surface.
7. A device according to claim 1 wherein said depressions, to be most effective, represent not more than 95% and not less than 50% of total surface area, where applied.
8. A device according to claim 1 wherein said surface s adjacent other than fluids.
ET
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US38462789A | 1989-07-25 | 1989-07-25 | |
US384,627 | 1989-07-25 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1991001247A1 true WO1991001247A1 (en) | 1991-02-07 |
Family
ID=23518079
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/CA1990/000228 WO1991001247A1 (en) | 1989-07-25 | 1990-07-23 | Fluid dynamic surfaces |
Country Status (2)
Country | Link |
---|---|
AU (1) | AU6037390A (en) |
WO (1) | WO1991001247A1 (en) |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1994002744A1 (en) * | 1991-07-18 | 1994-02-03 | Velke Willi H | A device to reduce drag over the surface of mast and boom of a sailcraft |
US5540406A (en) * | 1993-10-25 | 1996-07-30 | Occhipinti; Anthony C. | Hydrofoils and airfoils |
US5971326A (en) * | 1996-12-05 | 1999-10-26 | Deutsch Forschungsanstalt Fur Luft-Und Raumfahrt E.V. | Surface for a wall subject to a turbulent flow showing a main direction of flow |
WO2004012987A2 (en) * | 2002-04-26 | 2004-02-12 | Board Of Regents | Methods for reducing the viscous drag on a surface and drag reducing device |
WO2007100281A1 (en) * | 2006-03-03 | 2007-09-07 | Ragnar Winberg | Procedure to provide a propeller with ridges |
EP2447153A1 (en) * | 2010-10-28 | 2012-05-02 | Zuei-Ling Lin | Method of enhancing the output efficiency of a propeller and reducing the noise thereof |
US20140014780A1 (en) * | 2011-03-30 | 2014-01-16 | Kawasaki Jukogyo Kabushiki Kaisha | High-lift device of flight vehicle |
WO2016083977A1 (en) * | 2014-11-24 | 2016-06-02 | Elenco De Qualidade Equipamentos De Controlo Unipessoal, Lda | Hull for vessel or board having hydrodynamic elements formed as recesses |
US10539157B2 (en) | 2015-04-08 | 2020-01-21 | Horton, Inc. | Fan blade surface features |
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FR2547269A1 (en) * | 1983-06-09 | 1984-12-14 | Delplanque Jean Claude | Novel aerodynamic lift device |
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- 1990-07-23 AU AU60373/90A patent/AU6037390A/en not_active Abandoned
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WO1994002744A1 (en) * | 1991-07-18 | 1994-02-03 | Velke Willi H | A device to reduce drag over the surface of mast and boom of a sailcraft |
US5540406A (en) * | 1993-10-25 | 1996-07-30 | Occhipinti; Anthony C. | Hydrofoils and airfoils |
US5971326A (en) * | 1996-12-05 | 1999-10-26 | Deutsch Forschungsanstalt Fur Luft-Und Raumfahrt E.V. | Surface for a wall subject to a turbulent flow showing a main direction of flow |
WO2004012987A2 (en) * | 2002-04-26 | 2004-02-12 | Board Of Regents | Methods for reducing the viscous drag on a surface and drag reducing device |
WO2004012987A3 (en) * | 2002-04-26 | 2004-06-10 | Regents Board Of | Methods for reducing the viscous drag on a surface and drag reducing device |
US7044073B2 (en) | 2002-04-26 | 2006-05-16 | Board Of Regents Of The University Of Texas System | Methods for reducing the viscous drag on a surface and drag reducing device |
WO2007100281A1 (en) * | 2006-03-03 | 2007-09-07 | Ragnar Winberg | Procedure to provide a propeller with ridges |
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