DEVICES, SYSTEMS, AND METHODS FOR REDUCING WATERCRAFT DRAG USING PASSIVE AND ACTIVE AIR INTRODUCTION

Description

RELATED APPLICATIONS

This application is a Continuation-in-Part of PCT Application No. PCT/US24/41229, filed on Aug. 7, 2024, which claims priority to U.S. Provisional Patent Application No. 63/518,087, filed Aug. 7, 2023, entitled “Devices and Methods for Reducing Watercraft Drag.” This application further claims priority to U.S. Provisional Patent Application No. 63/803,445, filed May 9, 2025, entitled “Active Hydrofoil Devices, Systems, and Methods.” The entire contents of each of application identified here are incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

This disclosure is directed generally toward watercrafts, such as surfboards, boats, jet skis, hydrofoils, submarines, drones, and the like. More specifically, this disclosure is directed to introducing air between the watercraft and the water to reduce drag. Even more particularly, the disclosure relates to passive and active systems for reducing hydrodynamic drag by introducing air or other low-drag fluids between a watercraft and surrounding water, including through hull-mounted passages and hydrofoil-based air injection systems.

Description of the Related Art

When a watercraft floats in water with no velocity, much of its bottom, i.e., hull in the context of a boat or board in the context of a surfboard, contacts the water. Upon acceleration, the craft experiences drag, as a result of the interface between the surfaces that are in contact with water. As the craft “planes up,” i.e. a portion of the hull previously in contact with the water is lifted out of the water, the drag associated with the friction between craft and water is reduced. In some watercrafts, such as some boats, hydrofoil tabs are utilized to further lift the hull out of the water. Some watercraft, in the alternative, include one or more hydrofoils designed to generate lift to cause the bottom of the watercraft to rise out of the water, thereby reducing drag. Hydrofoils themselves, though, experience an exponential increase in drag the faster they move through the water and/or the deeper in water they are.

FIG. 1 shows a prior art watercraft 100 utilizing tabs for raising the hull out of the water, such as that offered by Hallett® Boats of Arizona. The tabs of the prior art watercraft 100 comprise two adjustable steel planes that mount to the transom on the rear of the prior art watercraft 100. When adjusted to contact the water, the water exerts a force on the tabs, thereby creating an upward pressure that lifts the hull of the prior art watercraft 100. In doing so, the surface area of the water-hull interface is reduced, and the prior art watercraft 100 can achieve a greater velocity.

FIGS. 1B-1D shows prior art hydrofoil surfboards 1000 having a board 1002 connected to front and rear hydrofoils 1006a, 1006b by a mast 1004. Generally speaking, hydrofoils generate lift by virtue of their geometry and the downward deflection of water, similar to the wings of an airplane. This lift force raises the bottom of the watercraft out of the water, substantially reducing the drag experienced by the watercraft and resulting in increased efficiency and higher top speeds.

In addition to improving efficiency and speed, hydrofoils 1006a, 1006b offer a smoother and more stable ride, especially in turbulent waters. With the bottom lifted above the waves, the impact of surface turbulence is minimized, reducing impact and vibration that users would otherwise feel. Hydrofoils 1006a, 1006b are therefore widely utilized for passenger ferries and racing boats, where comfort, speed, and stability are crucial. They are also used on hydrofoil surfboards, wind surfboards, and kiteboards to substantially reduce drag and achieve faster velocities.

Moreover, smaller waves following a relatively larger set of waves tend to become aerated or “foamy.” Surfboard users have come to realize that these foamy waves enable the board to travel more quickly through the water, due to a layer of air between the surfboard and the water that reduces drag. Similarly, studies of penguins have revealed that, before diving underwater, the birds fluff up their feathers to trap air. When swimming, penguins release the trapped air, thereby reducing drag due to the surrounding air layer, and enabling them to swim at increased velocity.

SUMMARY OF THE DISCLOSURE

The present disclosure relates to watercraft configured to reduce hydrodynamic drag by introducing air into water flowing along the watercraft during use. This disclosure includes watercrafts comprising a body including a hull and a deck; and a means for transferring ambient air under said deck.

In one aspect, the disclosure provides a watercraft having a hull and one or more features that allow air to move from a location exposed to air to a location along or beneath the hull. As the watercraft moves through water, the air introduced along the hull forms air-water interfaces that reduce the amount of hull surface in contact with water and reduce fluid friction, thereby reducing drag.

In another aspect, the disclosure provides a watercraft having a hull and one or more submerged components, such as hydrofoils, masts, or connecting structures, with features that introduce air onto or near those submerged components. The air introduced near the submerged components changes how water flows around them, which can reduce drag, improve lift efficiency, and influence cavitation behavior.

In some embodiments, air is introduced along the hull and/or along submerged components. Air may travel through holes, passages, channels, openings, porous sections, or similar features formed in the watercraft, and may originate from ambient air, stored air, or other air sources. The air-introducing features may be formed in or extend through the hull, deck, hydrofoil, mast, or combinations thereof.

This has outlined, rather broadly, the features and technical advantages of the present disclosure so that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further features and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the various exemplary embodiments will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. Where possible, the same reference numerals and characters are used to denote like features, elements, components or portions of the inventive embodiments. It is intended that changes and modifications can be made to the described exemplary embodiments without departing from the true scope and spirit of the inventive embodiments described herein as defined by the claims.

FIG. 1A shows a prior art watercraft 100, such as that available from Hallet® Boats of Arizona;

FIG. 1B shows a prior art watercraft 1000 with hydrofoils;

FIG. 1C shows a mast of a hydrofoil attached to the bottom of a watercraft with a power source connected to a propulsion source;

FIG. 1D shows a different, closer view of the power source attached to the watercraft of FIG. 1C;

FIG. 2 shows a translucent right side view of a watercraft according to one embodiment of the present disclosure;

FIG. 3 shows a translucent top front right perspective view of the watercraft of FIG. 2;

FIG. 4 shows a translucent bottom view of the watercraft of FIG. 2;

FIG. 5 shows a translucent front view of the watercraft of FIG. 2;

FIG. 6 shows a translucent back view of the watercraft of FIG. 2;

FIG. 7 shows a translucent top view of the watercraft of FIG. 2;

FIG. 8 shows another embodiment of a watercraft according to the present disclosure;

FIG. 9 shows another embodiment of a watercraft according to the present disclosure;

FIG. 10A-10C show various views of another embodiment of a watercraft according to the present disclosure;

FIG. 11 shows a side view of another embodiment of a watercraft according to the present disclosure; and

FIGS. 12A-12B show detailed views of the variations of holes that may be utilized in watercrafts according to the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Overview of Air Introduction for Drag Reduction

This disclosure relates to watercraft that reduce hydrodynamic drag by introducing air into water flowing along surfaces of the watercraft during operation. Air introduced along a hull surface, a submerged lifting surface, or both, alters local flow conditions to reduce drag and improve performance. The disclosure includes hull-based hydrofoil-based implementations, and implementations, combinations thereof.

In some embodiments, watercraft 200 described herein generally include one or more holes, passages, or tubes 208 formed through the watercraft 200 from a deck 202 or other above-water surface to a hull 204 or other water-contacting surface. These features allow ambient air to move from a region exposed to air to the underside of the watercraft during operation 210a, 210b.

Other embodiments of watercrafts described herein include one or more hydrofoils connected to the watercraft by one or more masts and one or more injectors to inject fluid, such as for example, air or air bubbles, onto or adjacent to the one or more hydrofoils and/or the one or more masts. The watercraft may be one of a plethora of watercrafts, such as for example a surfboard, a wind surfboard, an engine-driven boat, a sailboat, a drone, a jet ski, a kayak, and many others known in the art. As one of skill in the art would understand, many different types and shapes of hydrofoils are possible, such as for example, anhedral, dihedral, bat wing, surface-piercing, ladder, fully submerged, supercavitating, and others known in the art. The injector may be an air or fluid-pump, a bubbler, or other mechanisms known in the art. In some specific embodiments, the injector is a passive element, e.g., one or more tubes configured to capture air as the watercraft moves through the air. In one specific embodiment, the injector is located on the mast.

Throughout this description, the preferred embodiment and examples illustrated should be considered as exemplars, rather than as limitations on the present disclosure. As used herein, the term “invention,” “device,” “method,” “disclosure,” “present invention,” “present device,” “present method,” or “present disclosure” refers to any one of the embodiments of the invention described herein, and any equivalents. Furthermore, reference to various feature(s) of the “invention,” “device,” “method,” “disclosure,” “present invention,” “present device,” “present method,” or “present disclosure” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature(s).

It is also understood that when an element or feature is referred to as being “on” or “adjacent” to another element or feature, it can be directly on or adjacent the other element or feature or intervening elements or features may also be present. It is also understood that when an element is referred to as being “attached,” “connected” or “coupled” to another element, it can be directly attached, connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly attached,” “directly connected” or “directly coupled” to another element, there are no intervening elements present.

Relative terms such as “outer,” “above,” “lower,” “below,” “horizontal,” “vertical” and similar terms, may be used herein to describe a relationship of one feature to another. It is understood that these terms are intended to encompass different orientations in addition to the orientation depicted in the figures.

Although the terms first, second, etc. may be used herein to describe various elements or components, these elements or components should not be limited by these terms. These terms are only used to distinguish one element or component from another element or component. Thus, a first element or component discussed below could be termed a second element or component without departing from the teachings of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated list items.

The terminology used herein is for describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” and similar terms, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Embodiments of the disclosure are described herein with reference to different views and illustrations that are schematic illustrations of idealized embodiments of the disclosure. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances are expected. Embodiments of the disclosure should not be construed as limited to the particular shapes of the regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Like elements among embodiments are referenced herein with the same reference numerals, except where differences are articulated.

It is understood that while the present application is written using the terms “watercraft,” “surfboard,” and “boat” and with watersports, boating, and nautical activities generally in mind, the devices, methods, and concepts herein could be applied to fields other than watersports and nautical activities, as would be understood by one of skill in the art.

Physics of Air-Water Interaction, Lift, and Drag Reduction

The embodiments described herein rely on fundamental principles of fluid dynamics governing air-water interaction, boundary layers, lift, drag, and cavitation. These principles apply generally to watercraft surfaces and submerged lifting structures and are independent of the specific mechanisms used to introduce air.

When a watercraft moves through water, a viscous boundary layer forms along wetted surfaces, producing skin-friction drag and pressure drag. Drag force scales with fluid density, velocity, wetted surface area, and a drag coefficient associated with surface conditions and flow regime. Introducing air adjacent to a wetted surface replaces or disrupts portions of the water boundary layer with a lower-density, lower-viscosity medium, thereby reducing effective drag coefficient and frictional resistance.

Similarly, lift-generating structures such as hydrofoils produce lift through pressure differentials and fluid deflection. While lift increases with velocity, drag associated with submerged lifting surfaces increases due to viscous losses, induced drag, and cavitation. Introducing air along or near such structures alters local flow conditions, reduces drag for a given lift force, and may enable equivalent lift at lower velocities.

The drag force acting on an objection moving through a fluid can be expressed as:

F D = 1 2 ⁢ ρ ⁢ v 2 ⁢ C D ⁢ A ,

where F_D is the drag force, ρ is the fluid density, v is the velocity of the object relative to the fluid, C_D is the drag coefficient, and A is the effective wetted surface area of the object.

For watercraft operating in water, the density term ρ is relatively high, and the wetted surface area A can be substantial, particularly along hull surfaces and submerged components. As velocity increases, drag increases approximately with the square of velocity, meaning even small reductions in effective density, drag coefficient, or wetted surface area can produce significant reductions in total drag.

The systems and methods described herein reduce drag by intentionally introducing air into regions of water flow adjacent to the watercraft. Air has a substantially lower density and viscosity than water. When air is introduced along a hull surface or near a submerged structure, portions of the water boundary layer are displaced or disrupted by air, effectively reducing the local fluid density ρ acting on the surface, reducing the effective drag coefficient C_D, and reducing the portion of the surface area A that is in direct contact with water.

Similar principles apply to lift-generating structures such as hydrofoils. Lift force is also dependent on fluid density and velocity. By modifying the local flow environment around a hydrofoil through the introduction of air, the disclosed embodiments reduce drag associated with lift generation and, in some cases, enable equivalent lift to be achieved with reduced surface area or at lower speeds.

The lift force acting on a body moving through a fluid can be expressed as:

F L = 1 2 ⁢ ρ ⁢ v 2 ⁢ C L ⁢ A ,

where F_L is the lift force, C_L is the lift coefficient, and A is the effective lifting surface area.

For watercraft employing submerged lifting surfaces such as hydrofoils, lift is used to raise portions of the craft out of the water, thereby reducing wetted surface area and drag. However, achieving sufficient lift typically requires increased velocity, increased surface area, or operation at greater depth, all of which increase drag and energy consumption.

The introduction of air as described herein modifies the local flow environment around lifting surfaces by reducing effective fluid density, altering boundary-layer behavior, and changing pressure distributions. These effects allow a desired lift force F_L to be achieved with reduced drag, reduced surface area A, or at lower velocities v than would otherwise be required. In some embodiments, air introduction enables stable lift while simultaneously reducing parasitic drag and mitigating cavitation-related losses.

From a fluid-dynamics perspective, lift and drag forces acting on submerged bodies depend on the density of the surrounding fluid, the velocity of the flow, and pressure distributions established along the body surfaces. Introducing air into water flowing along a submerged surface lowers the effective fluid density and alters boundary-layer behavior, which in turn modifies local pressure fields force generation. In the case of submerged hydrofoils, these effects may be used to selectively influence draft and lift characteristics of the hydrofoil and associated submerged structures. When air is introduced along an upper surface of a hydrofoil, the modified flow conditions can increase pressure differentials across the hydrofoil and increase lift for a given velocity or angle of attack. Conversely, introducing air along a lower surface of a hydrofoil may reduce effective fluid density beneath the hydrofoil and decrease in life, which some embodiments may be used to control lift magnitude, trim, or stability of the watercraft. In addition to lifting surfaces, introducing air along non-lifting submerged components such as masts, struts, or other support structures reduces skin-friction drag acting on those components, thereby increasing overall speed and hydrodynamic efficiency of the watercraft.

In some operating regimes, air introduced along a surface forms discrete bubbles or thin air films that reduce skin-friction drag. In other regimes, air introduction produces stable or semi-stable air-water interfaces or cavities that partially or fully separate the solid surface from liquid water. In certain embodiments, controlled cavitation or supercavitation is achieved, further reducing drag by substantially isolating portions of the watercraft from liquid water.

Hull-Based Air Introduction

Watercraft described herein may include one or more holes, passages, or tubes formed through the watercraft from a deck or other above-water surface to a hull or other water-contacting surface. These holes or passages allow ambient air to move from a region exposed to air to the underside of the watercraft during movement.

FIGS. 2-7 show various views of an embodiment of a watercraft 200 according to the present disclosure. FIG. 2 shows this embodiment floating on water 214. The watercraft 200 has a deck 202, a hull 204, and holes 208 formed from the deck 202 to the hull 204. In some embodiments, the watercraft 200 may also have fins (not pictured in FIGS. 2-7). It is understood that some watercrafts do not contain fins. While the watercraft 200 as shown in FIG. 2 is a surfboard, it is understood that other watercraft, such as boats, jet skis, and watercraft with hydrofoils, may make use of the concepts described herein. Shown is a simple surfboard, but it also understood that watercraft with additional features, such as fins, hydrofoils, etc., may make use of the concepts described herein. Further, while 26 holes 208 are shown in FIGS. 3-7, it is understood that more or less holes 208 are possible such as, for example 1, or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, and so on. It is understood that these are exemplary in nature and do not limit this disclosure.

In some embodiments, the holes or passages are positioned and oriented such that movement of the watercraft through water creates a pressure differential between the deck region and the underside of the hull. Water flowing beneath the hull produces regions of reduced pressure that draw air through the holes or passages and release the air beneath the hull. The released air forms a layer, film, or distribution of air between the hull and the surrounding water, reducing direct water-surface contact and reducing hydrodynamic drag.

As shown in FIGS. 2 and 3, the holes 208 enable ambient air to flow from the deck 202 down to the hull 204, thereby creating a layer of air between the hull 204 and the water 214 in which the watercraft 200 ordinarily floats. When the watercraft 200 is at rest and mostly submerged under the water 214, the holes 208 will be mostly water-filled. However, once the watercraft 200 is moving (e.g., much of the surface area above the water 214), the water 214 rushing underneath the hull 204 will create a vacuum that draws air from the deck 202 to under the hull 204, through the holes 208. This layer of air reduces the total surface area of the hull 204 that contacts the water 214, in turn reducing drag and allowing for greater velocity utilizing the same amount of energy. The arrows 210a, 210b illustrate the direction of ambient airflow from the deck 202 to the hull 2024 of the watercraft 200.

In some embodiments according to the present disclosure, the holes 208 are angled relative to the axis normal to the deck 202 or other upper surface. This axis is shown in FIG. 2 as an arrow 212. In such embodiments, air is encouraged to flow down through the holes 208 as the watercraft 200 is propelled through the water. In some embodiments, the angle is between about 1 degree and about 90 degrees relative to the surface normal. In other embodiments, the angle is between about 10 degrees and about 80 degrees, between about 20 degrees and about 70 degrees, or between about 30 degrees and about 60 degrees. In one illustrative embodiment, the angle is approximately 45 degrees relative to the surface normal. Such angled orientations promote airflow through the holes during movement of the watercraft and influence the direction and distribution of air released beneath the hull. In some embodiments, different holes may have different orientations or angles relative to the deck 202.

It is understood that, while the holes 208 pictured in FIG. 2 are shown towards the rear of the watercraft 200, the holes 208 may be formed in other positions on the watercraft 200. In some embodiments, the holes or passages are distributed along a longitudinal extent of the hull. One or more holes may be located closer to a trailing end of the hull than to a leading end, while other holes may be positioned between the leading and trailing ends or distributed at multiple longitudinal locations. The holes may be formed towards the middle of the watercraft. Placement may be selected to coincide with regions of reduced pressure beneath the hull during operation. It is understood that many positions are possible. For example, in FIG. 11, the embodiment shown has holes distributed throughout the watercraft 900.

FIGS. 3-7 best illustrate an embodiment in which a plurality of holes 208—specifically 26—are arranged in multiple rows—in this example, 4 rows—extending across the hull. The holes 208 are not limited to a single location or edge of the hull and are instead distributed such that air is introduced at multiple points across the hull surface.

This distributed arrangement enables air released beneath the hull to interact with water flowing along the hull over an extended region, rather than being confined to a localized area immediately adjacent an individual opening. As the watercraft 200 moves through the water, air introduced through the holes 208 is carrier by the water flow along the hull surface, contributing to the formation of an air-water interface that extends along a region of the hull downstream of the openings.

The use of a plurality of holes 208—again, in the embodiment shown in FIGS. 3-7, a total of 26—arranged in rows or patterns allows the air-water interface to be sustained across a broader portion of the hull than would be achieved by a single opening or a small number of openings (i.e., 6 or less). This distributed introduction of air reduces sensitivity to the precise geometry of any individual opening and promotes hull-scale drag reduction.

In some embodiments, a region of the hull adjacent one or more holes or passages is shaped to retain air beneath the hull during movement of the watercraft. Such regions may be concave, recessed, stepped, or otherwise shaped to support formation and retention of an air-water interface while maintaining stability and control of the watercraft.

In some embodiments, the holes or passages have a substantially uniform cross-sectional size from the deck to the hull. In other embodiments, the holes or passages have a larger cross-sectional size at the hull than at the deck to promote air release beneath the hull. Hole sizes and shapes may be selected based on the size, weight, and intended operating conditions of the watercraft.

With reference to FIG. 12A, some watercraft 900a according to the present disclosure have holes 908a are about or the same diameter throughout starting at the deck 902a and through to the hull 904a. In other embodiments 900b, as shown in FIG. 12B, the holes 908b are larger in diameter on the hull 904b relative to their respective diameters on the deck 902b. The holes 908a may have a diameter or diameters throughout between 0.01 inches and 1 inch. It is understood that other diameters and diameter range are possible. For example, with larger watercraft (e.g., major vessels), the upper limit of the diameter range may be 100 inches.

FIG. 8 shows another embodiment of a watercraft 800 according to the present disclosure. Like the watercraft 200 shown in FIGS. 2-7, the watercraft 800 shown in FIG. 8 contains a deck 802 (not pictured), which may be the same as or similar to the deck 202; and a hull 804, which may be the same as or similar to the hull 204. The watercraft 800 further contains hole markers 808, which indicate where holes—which may be the same as or similar to the holes 208—would be formed. While 16 hole markers 808 are shown in FIG. 8, it is understood that other numbers of hole markers are contemplated disclosure such as, for example, between 1 and 30, 5 and 25, 10 and 20, and 12 and 17. One of skill in the art would understand that these ranges are purely exemplary in nature and do not limit this disclosure.

In some embodiments according to the present disclosure, the watercraft 800 contains fin slots 806, in which fins (not pictured) can be fastened to the watercraft 800. While five fin slots 806 are depicted in FIG. 8, it is understood that more or less fin slots 806 are possible such as, for example, one or more, two or more, three or more, and four or more. It is further understood that these ranges are exemplary in nature and not intended to limit this disclosure. Moreover, it is understood that some watercraft 800 do not contain fin slots 806, and instead may be either outfitted with permanent fins or no fins at all.

FIG. 8 further illustrates an embodiment in which the openings of the holes 808 may differ in shape, size, and placement across the watercraft 800. In this embodiment, the holes 808 are not uniformly sized and not arranged in a regular grid or pattern. Instead, the openings are positioned at selected locations based on anticipated flow conditions along the hull 804 of the watercraft 800 based on anticipated flow conditions along the hull 804 during operation.

Varying the size and placement of the holes allow different amounts of air to be introduced at different regions of the hull 804, enabling control over how the air-water interface develops and persists as water flows along the hull 804 surface. In some regions, larger openings may supply greater volumes of air, while in other regions smaller openings may supplement or maintain the air-water interface.

FIGS. 9-10C show another embodiment of a watercraft 900 according to the present disclosure. Like the watercraft 200, the watercraft 900 contains a deck 902, which may be the same as or similar to the deck 202, 802; a hull 904, which may be the same as or similar to the hull 204, 804; fins 906 (shown in FIG. 10A); and holes 908, which may be the same as holes 208.

As best shown in FIG. 10A, a portion 910 of the hull 904 is concave to create an air-water interface zone beneath the watercraft 900. In such embodiments, a plurality of holes are positioned within or adjacent to the concave portion 910 such that air introduced beneath the hull 904 during movement of the watercraft 900 is received and retained within the concave portion 910.

As the watercraft 900 moves through the water, water flowing along the hull 904 cooperates with the concave portion 910 to carry and maintain air beneath the hull 904, thereby supporting formation of an air-water interface along a region of the hull that extends beyond the individual openings themselves. The concave portion 910 functions as a flow-shaped region that promotes persistence of the air-water interface.

To prevent instability, the concave portion 910 does not extend across the entire width of the watercraft 900, and thus, at least the edges of the hull 904 maintain contact with the water when the watercraft 900 is in use.

In some embodiments, air delivered beneath the hull is supplied solely by air drawn through the holes during movement of the watercraft. In other embodiments, air may additionally be supplied by a device such as a pump, blower, or compressor that is fluidly coupled to one or more of the holes or passages.

While deck-to-hull holes or passages are one illustrative way of introducing air, the disclosure is not limited to any particular geometry or configuration. Air may be introduced through any suitable structure that allows air to reach regions of water flow adjacent to the watercraft.

Airflow Around Hydrofoils and Submerged Structures

In some embodiments, the watercraft includes one or more hydrofoils coupled to the hull by one or more masts or connecting structures. The hydrofoils are submerged during operation and generate lift to raise at least a portion of the hull out of the water.

Air introduced to hydrofoils and air introduced to hull surfaces may be supplied by common air-transfer structures or air sources, reflecting the shared physical principles underlying both implementations.

In certain embodiments, one or more openings, passages, or channels convey air from a region exposed to air to a region adjacent to a hydrofoil during movement of the watercraft. Water flow around the hydrofoil during operation creates regions of reduced pressure along portions of the hydrofoil surface, particularly near leading-edge regions, along pressure-side surfaces, along suction-side surfaces, or some combination thereof. In some operating regimes, the introduced air forms discrete bubbles or thin air films, while in other regimes it forms a more continuous air-water interface or cavity. These reduced-pressure regions receive air conveyed through the openings, passages, or channels.

The conveyed air forms an air-water interface along at least a portion of the hydrofoil, reducing direct contact between the hydrofoil surface and liquid water. This reduces skin-friction drag acting on the hydrofoil and, in some embodiments, modifies pressure distribution along the hydrofoil to improve lift efficiency or delay flow separation.

In some embodiments, air is conveyed to the hydrofoil through passages extending through a mast that connects the hydrofoil to the hull. The mast may be hollow or may include one or more internal channels configured to carry air. In other embodiments, air is conveyed through external conduits or channels coupled to the hydrofoil.

In hydrofoil-specific embodiments, air introduction is applied selectively to different regions of the hydrofoil and associated submerged structures to achieve desired performance outcomes during operation. Air conveyed to a hydrofoil may be directed to an upper surface, a lower surface, or both depending on whether increased lift, reduced lift, or drag reduction is desired under particular operating conditions. For example, directing air along an upper surface (typically the suction-side) of a submerged hydrofoil may be used to increase lift or maintain lift at lower velocities, while directing air along a lower surface (typically the pressure side) may be used to moderate lift, adjust trim, or enhance stability. In addition to the hydrofoil itself, air may be delivered along non-lifting submerged components such as masts, struts, or fuselage structures to reduce parasitic drag associated with those components without materially affecting lift generation.

Some embodiments of a watercraft according to the present disclosure inject a fluid with a lower drag coefficient relative to the fluid environment to reduce the drag experienced by the watercraft for a given cross-sectional area. In specific embodiments, the fluid is injected on or adjacent to at least a portion of the one or more hydrofoils, such as for example on their leading edge or adjacent to an upper surface. In other embodiments, the fluid is injected on or adjacent to the masts. In yet other embodiments, the fluid may be injected on or adjacent to both the hydrofoils and the masts. It is understood that the fluid may be injected on or adjacent to other components, such as for example, a fuselage, hull, and/or other components known in the art. Additionally, many combinations are possible, and it is understood that selective injection is possible, e.g., one may select injection of fluid on specific components, all components, or no components.

In some embodiments, the mast is hollow such that the injector can inject the fluid through the mast as a conduit. In some such embodiments, the mast may include a hole, channel, aperture, or other opening to permit ingress of air into the mast. In some of these such embodiments, the hole(s), channel(s), aperture(s), or other opening(s) may also permit egress of air or fluid to the leading edge of the mast. In another specific embodiment, the injector injects air onto or adjacent to the leading edge(s) of one or more hydrofoils. The injection of fluid may be powered by a battery or other power source attached to the watercraft and/or the mast.

Injecting a fluid with a lower drag coefficient on or adjacent to the hydrofoil, the masts, and/or other components can improve the efficiency of the watercraft and, in some embodiments, can enable the same lift force with a smaller hydrofoil surface area. This increased efficiency becomes more dramatic the deeper the hydrofoil is submerged, given that a deeper submerged hydrofoil encounters increased resistance. Conversely, injecting a fluid with a higher lift coefficient can enable the same lift force with a lower velocity. It is understood that, in embodiments in which the fluid is air, an air-water interface will be created upon injection, which will reduce friction and drag.

Some embodiments of watercraft according to the present disclosure also contain a motor connected to a propeller, which can be used to propel the watercraft through the water. In some embodiments, the power source for the motor is shared with a power source for the injector.

Additionally, in some embodiments according to the present disclosure, the injection of fluid onto or around the hydrofoil, masts, and/or other components results in controlled cavitation or supercavitation, eliminating or mitigating the negative effects of cavitation for hydrofoil geometries that could not otherwise achieve a supercavitation state. Such regimes may substantially isolate portions of the hydrofoil or mast from liquid water, reducing drag at higher speeds or greater depths. In specific embodiments, the one or more injectors can be tuned, e.g., through modifying location, orientation, flow rate, nozzle geometry, etc., to achieve stable supercavitation.

The various exemplary inventive embodiments described herein are intended to be merely illustrative of the principles underlying the inventive concept. It is therefore contemplated that various modifications of the disclosed embodiments will without departing from the inventive spirit and scope be apparent to persons of ordinary skill in the art. They are not intended to limit the various exemplary inventive embodiments to any precise form described. Other variations and inventive embodiments are possible in light of the above teachings, and it is not intended that the inventive scope be limited by this specification, but rather by the claims following herein.

Although the present disclosure has been described in detail with reference to certain preferred configurations thereof, other versions are possible. Embodiments of the present disclosure can comprise any combination of compatible features shown in the various figures, and these embodiments should not be limited to those expressly illustrated and discussed. Therefore, the spirit and scope of the disclosure should not be limited to the versions described above. Moreover, it is contemplated that combinations of features, elements, and steps from the appended claims may be combined with one another as if the claims had been written in multiple dependent form and depended from all prior claims. Combination of the various devices, components, and steps described above and in the appended claims are within the scope of this disclosure. The foregoing is intended to cover all modifications and alternative constructions falling within the spirit and scope the disclosure.