# US 5,346,745 A · Elastic micro-fabricated surface layer for reducing turbulence and drag on an object while it moves through a fluid medium > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,346,745 A - Document ID: US5346745A - Status: Granted - Kind: A - Application number: 08/069,820 - Filed: 1993-06-01 - Granted: 1994-09-13 - Earliest claimed: 1993-06-01 - Assignees: The United States of America as represented by the Secretary of the Navy - Inventors: Promode R. Bandyopadhyay - Web page: https://patentgrep.com/patent/US5346745A ## CPC - F42B 19/125: {Torpedoes provided with drag-reducing means (projectiles with drag-reducing means F42B10/38)} - B63B 1/34: by reducing surface friction - B64C 21/10: using other surface properties, e.g. roughness - F15D 1/12: by influencing the boundary layer - Y02T 50/10: Drag reduction - Y02T 70/10: Measures concerning design or construction of watercraft hulls - Y10T 428/24314: Slit or elongated - Y10T 428/24479: including variation in thickness - Y10T 428/2457: Parallel ribs and/or grooves - Y10T 428/24744: Longitudinal or transverse tubular cavity or cell - F42B: EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION (explosive compositions C06B; fuzes F42C; blasting F42D) - B63B: SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING (arrangements of vessel ventilation, heating, cooling, or air-conditioning B63J2/00; floating substructures as supports of dredgers or soil-shifting machines E02F9/06) - B64C: AEROPLANES; HELICOPTERS - F15D: FLUID DYNAMICS, i.e. METHODS OR MEANS FOR INFLUENCING THE FLOW OF GASES OR LIQUIDS - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A surface for use in connection with an object in relative motion through a luid medium includes a plurality of surface elements arranged in rows on the surface, with surface elements of each row being arranged generally orthogonal to the direction of relative motion of the object in a medium. Each surface element includes means defining a cavity, the means including a bottom surface layer, sidewalls, and an upper lip supported along an upstream edge in a cantilevered manner and extending in a downstream direction over the cavity to define a gap permitting fluid communication between the medium and the cavity. The lip is flexible so as to facilitate deflection in response to differentials between pressure inside the cavity and outside the cavity. The cavities of the surface elements in each row are interconnected by means of passageways thereby to facilitate fluid communication therebetween. It is believed that, in the surface layer, in response to local variations in pressure of the medium over surface elements in a row, due to the passage of vortices overhead, the lips of the surface elements deflect to permit equalization of fluid pressure between the medium proximate the surface elements and the respective cavity. The passageways interconnecting the cavities of the surface elements facilitate equalization of pressure between cavities of surface elements in each row, thereby reducing pressure variations, and thereby also reducing turbulence of the medium around the object. ## Claims ### Claim 1 For use in reducing turbulence in connection with motion of an object relative to a fluid medium, a surface layer mounted on said object comprising: (A) a plurality of surface elements arranged in rows on said surface, surface elements of each row being arranged generally orthogonal to the direction of relative motion, each surface element comprising means defining a cavity, said means including a bottom surface layer, sidewalls, and an upper lip supported along an upstream edge in a cantilevered manner and extending in a downstream direction over said cavity to define a gap permitting fluid communication between said medium and said cavity, said lip being flexible so as to facilitate deflection in response to differentials between pressure inside said cavity and outside said cavity; and (B) means defining fluid communication passageways for facilitating fluid communication between cavities of adjacent surface elements in each row. ### Claim 2 (depends on 1) A surface layer as defined in claim 1 in which, in response to local variations in pressure of said medium over surface elements in a row, the lips of the surface elements deflect to permit equalization of fluid pressure between the medium proximate the surface elements and the respective cavity, and the fluid communication passageways facilitate equalization of pressure between cavities of surface elements in each row, thereby reducing pressure variations, and thereby also reducing turbulence of the medium around the object. ### Claim 3 (depends on 1) A surface layer as defined in claim 1 in which surface elements are arranged in a plurality of adjacent rows, with the surface elements of adjacent rows being staggered. ### Claim 4 (depends on 3) A surface layer as defined in claim 3 in which the surface elements all have a common width, the surface elements in each row being separated by a distance corresponding to the width. ### Claim 5 (depends on 1) A surface layer as defined in claim 1 in which the fluid communication passageways between cavities of adjacent surface elements are formed adjacent the bottom surface layer of the cavities. ### Claim 6 (depends on 1) A surface layer as defined in claim 1 in which the surface layer is formed from silicon wafers using micro-machining techniques. ### Claim 7 (depends on 1) A surface layer as defined in claim 1 in which the surface layer is formed from a doped semi-conductive material to permit dissipation of electrical charges. ### Claim 8 (depends on 1) A surface layer as defined in claim 1 further comprising means defining inter-row fluid communication passageways for facilitating fluid communication between cavities of surface elements of adjacent rows.