Method for cleaning a surface of a body around which a fluid flows, and cleaning device

Abstract

The invention relates to a method for cleaning a surface (O) of a body around which a fluid (F) flows, in particular a ship's hull around which water flows, wherein at least one movable cleaning device (100) is arranged on the surface (O) of the body and is moved along the surface (O) for successive cleaning operations. According to the invention, the at least one cleaning device (100) acts as a passive vortex generator, so that vortices (W) are formed in the fluid (F) flowing around and the wall shear stress in the fluid-dynamic boundary layer on the surface (O) of the body is locally increased such that the surface (O) is cleaned.

Description

[0001] METHOD FOR CLEANING A BODY SURFACE OVER WHICH A FLUID FLOWS, AND CLEANING DEVICE

[0002] The invention relates to a method for cleaning a surface of a body around which a fluid flows, in particular a ship's hull around which water flows. At least one mobile cleaning device is arranged on the surface of the body and moved along the surface for successive cleaning. The invention further relates to an associated cleaning device.

[0003] STATE OF THE ART

[0004] Technical surfaces of bodies surrounded by fluids, in particular ship hulls or, for example, the inner walls of pipelines, are subject to permanent stresses during operation due to their interaction with the fluid and / or the substances or organisms carried therein.

[0005] contamination processes.

[0006] In the case of ship hulls, organic growth on the surface below the waterline poses a significant problem. This process of unwanted colonization by organisms and communities of organisms, also known as fouling, quickly leads to the formation of macroscopic growth layers, which increase the flow resistance of the ship's hulls and, in extreme cases, cause a significant increase in the weight of the ships, resulting in a significant increase in fuel consumption. Practical examples show that even a biofilm as thin as 0.5 mm, formed over a large area on the ship's hull at an early stage of the fouling process, can increase a ship's fuel consumption by 20-30%.

[0007] To delay the fouling process, for example, biocide-based paints are applied to ship hulls. The time-consuming process of repainting the paint in dry dock is typically only performed at intervals of several years. In between, shipping practices regularly perform mechanical cleaning of the ship's hulls using steel brushes or high-pressure water jets. These aggressive cleaning methods damage and remove the antifouling paint, thus shortening its lifespan and leading to the undesirable release of biocidal paint particles into the biosphere.

[0008] Cleaning is typically carried out while the ship is stationary, for example, manually by professional divers in the harbor basin. Regulations in many regions of the world prohibit the cleaning of ship hulls in harbor basins to prevent the introduction of invasive species into the local ecosystem. Cleaning at anchor can be carried out using cleaning devices or robots, which are typically operated as cable-based systems from the ship's deck. Such cleaning measures also result in undesirably long ship downtimes.

[0009] It is therefore desirable to clean ship hulls while the vessel is underway, preferably on the high seas, and the cleaning process should not damage the protective coating on the hull. In particular, a substantially continuous cleaning process can permanently prevent the formation of macroscopic growth. Continuous cleaning is also desirable because, typically, significant adverse effects on flow become apparent after just a few days of undisturbed growth.

[0010] The document WO 2010 / 059195 A1 discloses a cleaning robot with brushes for cleaning a ship's hull while the ship is traveling, wherein the robot has turbines which can be driven by the water flow and are operatively connected to a generator, so that an energy supply is formed for driving both the cleaning system and the movement of the robot on the ship's hull surface.

[0011] The document DE 102021 103 313 B3 discloses a traversing device for moving along the surface of a body around which a fluid flows, comprising a holding system for adhering the traversing device to the surface, a traction system for tracking, and a drive system for driving the traversing movement on the surface. The drive system has at least one flow body around which the fluid flows, for interacting with the fluid, so that flow energy can be extracted from the surrounding fluid for the traversing device's movement along the surface of the body around which the fluid flows, and can be used to solely drive the traversing movement. The traversing device can be equipped with a mechanical cleaning system and used for cleaning ship hulls while underway.

[0012] DISCLOSURE OF THE INVENTION It is the object of the present invention to propose an alternative method for cleaning a surface of a body around which a fluid flows, in particular a ship's hull around which water flows, by means of a mobile cleaning device, wherein the cleaning process is to be carried out in particular as gently as possible for the surface to be cleaned.

[0013] This object is achieved by a method according to claim 1 and a device according to claim 4. Advantageous developments of the invention are specified in the dependent claims.

[0014] The invention includes the technical teaching that at least one mobile cleaning device is arranged on the surface of the body and is moved along the surface for successive cleaning, wherein the at least one cleaning device acts as a passive vortex generator so that vortices are formed in the fluid flowing around the body and the wall shear stress in the fluid-dynamic boundary layer at the surface of the body is locally increased such that the surface is cleaned.

[0015] The basic idea of ​​the invention is to carry out a contactless surface treatment for cleaning and in particular to avoid the use of mechanical devices such as brushes. According to the invention, a cleaning effect is achieved by the targeted introduction of vortices into the fluid flow which increase the wall shear stress in the fluid-dynamic boundary layer to such an extent that adhering organic material is detached, at least during the early phase of colonization. The fluid-dynamic boundary layer forms the zone of the fluid flowing along the body surface in which the velocity profile of the flow perpendicular to the surface is significantly influenced by fluid friction. The wall shear stress is the tangential force per unit area exerted by the fluid on the body surface around which it is flowing, i.e. the momentum flow through the volume of fluid adjacent to the surface.An increase in wall shear stress leads to the removal of adhering contaminants, in the case of a ship's hull, of aquatic microorganisms and the resulting biofilm. Disruption of this early colonization phase, in particular, effectively prevents the entire sequence of further growth on the ship's hull.

[0016] According to the invention, the cleaning device acts as a passive vortex generator, i.e. no actively driven device, such as a motor-driven impeller, is used to generate the vortex. In particular, the cleaning device is dedicatedly provided with at least one vortex element around which flow acts as a passive vortex generator when the fluid flows around it. The geometry and dimensions of the at least one vortex element are to be designed such that, on the one hand, a local increase in wall shear stress is generated which is sufficient to clean the body surface, and on the other hand, the flow resistance of the cleaning device does not increase to such an extent that the holding force of the cleaning device on the body surface is exceeded, i.e. that unintentional detachment of the cleaning device from the surface is prevented at all flow velocities relevant in practice.

[0017] The targeted generation of vortices causes a sufficient increase in wall shear stress in the immediate vicinity of and downstream of the cleaning device to achieve a cleaning effect. For example, the at least one vortex element can be configured such that, depending on the flow velocity, a cleaning effect is achieved in a downstream region up to three times the length of the cleaning device. Thus, the method according to the invention makes it possible to treat even hard-to-reach sections of the surface to be cleaned, for example, the sea chests, rudders, water coolers, or propeller shafts of a ship.

[0018] Within the scope of the method according to the invention, a mobile cleaning device is used which is designed to move and preferably navigate on the surface to be cleaned. By means of expedient movement, the entire surface can be cleaned successively. In particular, for cleaning a ship's hull, it is provided that the cleaning device is used continuously while the ship is underway. This makes it possible to keep the ship's hull permanently free of unwanted fouling without having to interrupt regular ferry operations for this purpose. Depending on the size of the ship, it may be expedient to use a plurality of cleaning devices at the same time in order to ensure that the fouling process does not exceed the earliest colonization phase in any section of the ship's hull, i.e. to clean before there is a significant change in the flow resistance orthere is a significant weight gain.

[0019] In a specific embodiment of the method according to the invention, at least two cleaning devices can be used, wherein the cleaning devices are brought into a V-shaped position in pairs to form a passive vortex generator on the surface of the body. In this variant, two cleaning devices are arranged relative to one another in such a way that the housings against which the flow occurs jointly act as a passive vortex generator. In particular, the cleaning devices each have an elongated housing, and in the V-position, the housings enclose an angle in the range of 30° to 45°. The vortices generated during the flow around them can influence the fluid-dynamic boundary layer in a wake area several meters downstream.

[0020] The invention further relates to a cleaning device for cleaning a surface of a body around which a fluid flows, in particular a ship's hull around which water flows, wherein the cleaning device is designed to move along the surface of the body. According to the invention, the cleaning device has at least one vortex element which can be flowed around and which, when the fluid flows around it, acts as a passive vortex generator, so that vortices are formed in the flowing fluid and the wall shear stress in the fluid-dynamic boundary layer on the surface of the body is increased such that local cleaning of the surface occurs. The cleaning device is thus intended for use in the context of the method according to the invention, and the above statements also apply mutatis mutandis to the cleaning device according to the invention.

[0021] In an advantageous embodiment, the cleaning device comprises a streamlined housing with at least two vane elements for generating downforce, wherein the end sections of the vane elements each form a vortex element. In particular, the cleaning device can comprise two pairs of vane elements, with two vane elements each protruding from the housing on opposite sides in the front and rear regions of the cleaning device. The vane profile, sweep, and angle of attack are designed such that, when the fluid flows around it, downforce is generated, whereby the cleaning device is pressed against the surface of the body to be cleaned.The vortices created by the pressure difference between the upper and lower surfaces of the wing elements create wake vortices in the tip region of the wing elements. With appropriate positioning of the wing elements, these vortices act on the fluid-dynamic boundary layer and generate the desired increase in wall shear stress. To promote the formation of such wake vortices, the tip regions of the wing elements preferably do not have "winglets," i.e., sharply angled or fanned-out end sections.

[0022] The housing of a cleaning device designed for use on ship hulls has, for example, a length in the range of 0.5 m to 2 m, a width of 20 cm to 50 cm and a height of 10 cm to 20 cm, without taking into account wing elements or other projecting components.

[0023] In a further embodiment, the cleaning device has a diffuser structure on the underside as a vortex element. The incoming fluid is introduced laterally beneath the cleaning device into the diffuser structure, where pairs of counter-rotating vortices are generated. This achieves the desired cleaning effect on the surface of the body beneath the cleaning device.

[0024] In a further embodiment, the cleaning device has at least one top-side and / or rear-side vortex structure as a vortex element, whereby cleaning of the surface of the body downstream of the cleaning device can be achieved. In the case of a rear-side vortex structure, the remaining sections of the cleaning device act as supports and ensure the necessary adhesive force and mobility, wherein these sections have a hydrodynamic shape so that the rear-side vortex structure experiences as undisturbed an inflow as possible. There is a great deal of freedom with regard to the geometric design of the vortex structure, i.e. the vortex structure can be optimized for the intended function as a passive vortex generator for influencing the fluid-dynamic boundary layer.

[0025] The cleaning device preferably has a holding system for adhesion and movement on the surface of the body, wherein the holding system comprises at least one magnetic wheel and / or at least two wing elements for generating downforce. The wheel has, for example, a circumferentially encircling permanent magnetic section, for example made of a ferrous metal-rare earth alloy, whereby the cleaning device is capable of adhesion to a magnetizable body surface, in particular a steel ship's hull. To further improve the holding force, the holding system can comprise downforce-generating elements such as wing elements. The holding system ensures that the cleaning device generates the holding force required for the respective application on the surface to be cleaned.

[0026] The cleaning device further advantageously has a drive system for driving movement on the surface of the body, wherein the drive system comprises at least one battery-operated electric motor for the at least one magnetic wheel and / or at least one control body around which the fluid can flow, which can be used for direct fluid-dynamic drive by means of momentum transfer from the fluid flowing around it and whose angle of attack is adjustable. By means of the drive system, the cleaning device is capable of automatic movement and can thus be designed, in particular, free of mechanical connections to external drive means and / or external holding means. The use of a control body around which the fluid can flow for direct fluid-dynamic drive is disclosed in the document DE 10 2021 103 313 B3, which is incorporated herein by reference.

[0027] In addition to the application for cleaning ship hulls, the cleaning device according to the invention and the method according to the invention can also be used, for example, for cleaning the inner walls of pipes, in particular pipelines.

[0028] EMBODIMENTS OF THE INVENTION

[0029] Further measures improving the invention are presented in more detail below, together with the description of exemplary embodiments of the invention, with reference to the figures. It shows:

[0030] Fig. 1 : a first embodiment of the inventive

[0031] Cleaning device when carrying out the method according to the invention,

[0032] Fig. 2: a second embodiment,

[0033] Fig. 3 a third embodiment, and

[0034] Fig. 4 shows a variant of the invention

[0035] procedure.

[0036] The figures show schematic representations of different exemplary embodiments of the cleaning device 100 according to the invention during the implementation of the method according to the invention for cleaning a surface O of a body around which a fluid F flows, in particular a ship's hull around which water flows. The dashed arrows representing the fluid F also indicate the main flow direction of the fluid F. The cleaning devices 100 are mobile and move forward on the surface O for successive cleaning. The cleaning devices 100 are designed free of mechanical connections to external drive means and / or external holding means, for example by means of a cable connection to a ship's deck, and are capable of independent movement on the surface O to be cleaned.

[0037] The illustrated embodiments of the cleaning device 100 each have a holding system for adhesion and movement on the surface 0, wherein the holding system comprises two pairs of magnetic wheels 5 (see the illustration of the underside of the cleaning device 100 in Fig. 2) and two pairs of laterally projecting wing elements 2 for generating downforce when flowing around the fluid F. The magnetic wheels 5, which are formed at least in sections from a permanent magnetic material, ensure adhesion to the surface of magnetizable bodies, in particular to steel ship hulls.

[0038] The cleaning devices 100 also have a drive system comprising a battery-operated electric motor accommodated in the housing 1 for driving the magnetic wheels 5, as well as at least one control body 6 around which flow occurs on the top side of the housing 1. The control bodies 6 serve for direct fluid-dynamic propulsion by means of momentum transfer from the surrounding fluid F. The angle of attack of the control bodies 6 relative to the flow is adjustable, for example by means of electric motors accommodated in the housing 1, so that the control bodies 6 can contribute to the maneuverability of the cleaning devices 100 on the surface O around which flow occurs.

[0039] According to the invention, the cleaning devices 100 act as passive vortex generators, so that vortices W are formed in the flowing fluid F, in particular the water flowing around the ship's hull, and the wall shear stress in the fluid-dynamic boundary layer at the surface 0 of the body is locally increased such that the surface 0 is cleaned. When used on a ship's hull, the cleaning effect particularly relates to the removal of biofilms formed in the early phase of organic colonization, and with a permanent, continuous process, the fouling process can thus be effectively suppressed.

[0040] Fig. 1 shows a first embodiment of the cleaning device 100, and the illustration shows that the end sections of the laterally projecting wing elements 2 each form vortex elements 10, at which the schematically illustrated trailing vortices W form in the surrounding fluid F. These vortices W lead locally to the required increase in the wall shear stress in the fluid-dynamic boundary layer at the surface O in the region behind the wing elements 2 and thus ensure the removal of adhering contaminants, for example biofilms. Depending on the flow velocity, direction of flow, and detailed design of the wing elements 2, a significant cleaning effect can be achieved downstream of the wing elements 2 in a region with an extension of up to three times the length of the cleaning device 100.

[0041] The vortices W shown in Fig. 1 starting from the end sections of the wing elements 2 are not shown in the other figures for the sake of better clarity.

[0042] Fig. 2 shows a second embodiment of the cleaning device 100 with a diffuser structure 3 on the underside as the vortex element 10. The illustration shows a perspective view of the underside of the cleaning device 100, and the body surface to be cleaned is hidden in the illustration. The diffuser structure 3 comprises a channel that continuously widens towards the rear of the cleaning device 100, into which the fluid F can flow laterally in the front area. As it flows through the diffuser structure 3, the schematically illustrated vortices W are generated in the fluid F, thereby achieving the intended cleaning effect in the area of ​​the surface beneath the diffuser structure 3.

[0043] Fig. 3 shows a third embodiment of the cleaning device 100 with the upper-side vortex structure 4 as the vortex element 10, which enables cleaning of the surface O downstream of the cleaning device 100. The vortex structure 4 is formed by two fin-like elements that extend continuously upwards toward the rear along the longitudinal direction of the housing 1. The schematically illustrated vortices W are imprinted on the fluid F flowing through the vortex structure 4.

[0044] Fig. 4 shows an embodiment of the method according to the invention based on a cooperative use of two cleaning devices 100.1, 100.2 according to the invention. In this case, the cleaning devices 100.1, 100.2 have assumed a V-shaped position to form a passive vortex generator on the surface O, ie a position relative to one another such that each cleaning device 100.1, 100.2 forms one leg of a "V", wherein the tip of the "V" is oriented substantially opposite to the flow direction of the surrounding fluid F. This arrangement acts as an additional vortex generator for generating larger-scale vortices W, which overlap with the vortices formed by the individual cleaning devices 100.1, 100.2 and can thus bring about an intensified cleaning effect.For example, it may be useful to use this process variant to clean areas of the surface to be cleaned that are particularly susceptible to soiling or difficult to access.

[0045] G

[0046] 10 Vortex element

[0047] 1 housing

[0048] 2 wing element

[0049] 3 Diffuser structure

[0050] 4 Vertebral structure

[0051] 5 magnetic wheel

[0052] 6 control bodies

[0053] F Fluid

[0054] 0 surface

[0055] W vertebrae

Claims

Claims:

1. A method for cleaning a surface (0) of a body around which a fluid (F) flows, in particular a ship's hull around which water flows, wherein at least one mobile cleaning device (100) is arranged on the surface (0) of the body and is moved along the surface (0) for successive cleaning, characterized in that the at least one cleaning device (100) acts as a passive vortex generator, so that vortices (W) are formed in the surrounding fluid (F) and the wall shear stress in the fluid-dynamic boundary layer on the surface (0) of the body is locally increased such that the surface (0) is cleaned.

2. Method according to claim 1, characterized in that the cleaning device (100) is provided with at least one vortex element around which flow can occur, the vortex element acting as a passive vortex generator when the fluid (F) flows around it.

3. Method according to claim 1 or 2, characterized in that at least two cleaning devices (100.1, 100.2) are used, wherein the cleaning devices (100.1, 100.2) are brought into a V-shaped position in pairs to form a passive vortex generator on the surface (O) of the body.

4. Cleaning device (100) for cleaning a surface (O) of a body around which a fluid (F) flows, in particular a ship's hull around which water flows, wherein the cleaning device (100) is designed to move on the surface (O) of the body, characterized in that the cleaning device (100) has at least one vortex element (10) around which flow can take place, which acts as a passive vortex generator when the fluid (F) flows around it, so that vortices (W) are formed in the flowing fluid (F) and the wall shear stress in the fluid-dynamic boundary layer on the surface (O) of the body is locally increased such that the surface (O) is cleaned.

5. Cleaning device (100) according to claim 4, characterized in that the cleaning device (100) has a streamlined housing (1) with at least two wing elements (2) for generating downforce, wherein the end sections of the wing elements (2) each form a vortex element (10).

6. Cleaning device (100) according to claim 4 or 5, characterized in that the cleaning device (100) has a diffuser structure (3) on the underside as a vortex element (10).

7. Cleaning device (100) according to one of claims 4 to 6, characterized in that the cleaning device (100) has at least one upper and / or rear vortex structure (4) as a vortex element (10) whereby cleaning of the surface (0) of the body downstream of the cleaning device (100) can be achieved.

8. Cleaning device (100) according to one of claims 4 to 7, characterized in that the cleaning device (100) has a holding system for adhesion and movement on the surface (O) of the body, wherein the holding system comprises at least one magnetic wheel (5) and / or at least two wing elements (2) for generating downforce.

9. Cleaning device (100) according to one of claims 4 to 8, characterized in that the cleaning device (100) has a drive system for driving the movement on the surface (O) of the body, wherein the drive system comprises at least one battery-operated electric motor for the at least one magnetic wheel (5) and / or at least one control body (6) which can be flowed around and which can be used for direct fluid-dynamic drive by means of momentum transfer from the flowing fluid (F) and whose angle of attack is adjustable.

10. Cleaning device (100) according to one of claims 4 to 9, characterized in that the cleaning device (100) is designed free of mechanical connections to external drive means and / or external holding means.

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