SE178277C1

SE178277C1 -

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Publication number: SE178277C1
Authority: SE
Publication date: 1961-01-01

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Uppfinnare: F W Boggs Prioritet begtird frail den 30 januari 1958 (Arnerikas Forenta Stater) Foreliggande uppfinning hanfor sig till ett salt att minska friktionsmotstandet mot ett foremal, som ror sig i ett fluidum. Uppfinningen ãr speeiellt inriktad pa ett forfarande for dampning air turbulensen ldngs kontaktytan Indian foremalet .och fluidet for uppratthallande UV laminar gransskiktstromning under sadana .forhallanden, att turbulent gransskiktstromning elj est skulle rada. Fluidet kan utgoras air en gas eller vatska. Inventor: F W Boggs Priority Begtird frail January 30, 1958 (United States of America) The present invention relates to a salt for reducing the frictional resistance of an object moving in a fluid. The invention is particularly directed to a process for vaporizing the air turbulence along the contact surface of Indian grinding and the fluid for maintaining UV laminar boundary layer flow under such conditions that turbulent boundary layer flow would otherwise prevail. The fluid can be released into a gas or liquid.

Fluidumpartiklarnas vidhaftning vid ytan pa en fast kropp, som ror sig i angransande resulterar i bildningen am ett sa kallat 'gransskikt. Arten air detta gransskikt langs kroppens yta, exempelvis langs ytan pa ett ,flygplan under flygning eller langs undervattenskroppen till ett fartyg under gang, utgor en avgorande faktor vid bestamning ay ytfriktionen. Om gransskiktet strommar jiamnt eller laminart, blir denna ytfriktion relativt svag. Om gransskiktet emellertid ãr omrort eller turbulent, okas bromsningen air foremalet i 'fluidet avsevart. En ay huvuduppgifterna for aerodynamisk och hydrodynamisk forskning har varit .och ar fortfarande att hindra, att detta gransskikt blir turbulent, eller med andra ord att bibehalla laminar gransskiktstrom intill }foremalets yta. Det generella problemet benamnes gransskiktstabilisering. The adhesion of the fluid particles to the surface of a solid body, which moves in adjacent, results in the formation of a so-called 'boundary layer. The nature of this boundary layer along the surface of the body, for example along the surface of an airplane in flight or along the underwater body of a ship in motion, is a decisive factor in determining surface friction. If the spruce layer flows evenly or laminarly, this surface friction becomes relatively weak. However, if the spruce layer is agitated or turbulent, the braking air formed in the fluid increases considerably. One of the main tasks of aerodynamic and hydrodynamic research has been and still is to prevent this spruce layer from becoming turbulent, or in other words to maintain laminar spruce layer currents adjacent to the surface of the object. The general problem is called spruce layer stabilization.

For node, ddr kroppar dro hell nedsinkta i .ett fluidurn, ãr forhallandet mellan troghetskrafter eller kinetiska krafter och viskosa krafter proportionellt mot en faktor, vii-ken. är kand som Reynolds tal. Arlen am ett verkligt fluidums stromning kan i miss grad bedomas pa grundval air motsvarancle Reynolds tal. Ett lagt sadant tal visar, att de visk5sa krafterna overvaga, medan ett hog Reynolds tal anger, att trOghetskrafterna eller de kinetiska krafterna overvaga. Gransskikt stromningen langs en slat yta iar sasom bekant laminar ailed atfoljande rninsta mojliga friktionsmotstand under ett visst Reynolds tal, vilket kan benamnas del kritiska talet. Over detta ligger en overgangszon, som leder till fullstandig turbulent gransskiktstromning och .darmed starlit iikat .friktionsmotstand. Det ar uppenbart, att man kan vanta sig en drastisk minskning air friktionsmotstandet, em man skulle kanna losa problemet att hindra gransskiktet frail att bli turbulent vid 'hoga Reynolds tal. For node, where bodies tend to sink into a fluid urn, the ratio of forces of inertia or kinetic forces to viscous forces is proportional to a factor, vii-ken. is known as Reynolds' speech. The volume of a real fluid flow can be judged to some extent on the basis of air corresponding to Reynolds' number. An added such number shows that the whispering forces monitor, while a high Reynolds number indicates that the forces of inertia or the kinetic forces monitor. The spruce layer flowing along a smooth surface is, as is well known, laminar ailed following the possible possible frictional resistance during a certain Reynolds speech, which can be called the critical part. Above this is a transition zone, which leads to completely turbulent spruce layer flow and thus rigid frictional resistance. It is obvious that one can expect a drastic reduction in the frictional resistance, if one could solve the problem of preventing the spruce layer from becoming turbulent at 'high Reynolds' speech.

Overgingen 'frail laminar till turbulent stromning fdrorsakas am en gradvis aiidring air sjalva gransskiktets dynamiska stabilitet. \rid relativt Mgt Reynolds tal dampar den relativt starka, inneboende, viskosa friktionen i fluidet intill kroppens yta snabbt alla stOrningar och hailer gransskildstrommen pâfltligt laminar eller stabil. Eftersom emellertid Reynolds tal är proportionellt mot forhallandet mellan troghetskrafter eller kinetiska krafter .och de viskosa krafterna, komma de kinetiska krafterna att overvaga ovanf Or ett visst Reynolds tal. Den automatiska dampningen pa grund ay viskos friktion blir sa.- lunda icke tillracklig ,fdr att utjamna alla storningar intill kroppens yta, ■vilket medf Or en dynamisk instabilitet i gransskiktet. Da denna insta:bilitet liar utvecklats i miss utstrackning, komma smarre storningar .att f Orstarkas, tills hela gransskiktet befinner sig i kraftig rorelse eller turbulens. The transition from frail laminar to turbulent flow is caused by a gradual increase in the dynamic stability of the boundary layer itself. Relatively Much Reynolds' speech quickly vaporizes the relatively strong, inherent, viscous friction in the fluid adjacent to the surface of the body all the disturbances and hails the spruce shield stream noticeably laminar or stable. However, since Reynolds' number is proportional to the ratio of forces of inertia or kinetic forces to the viscous forces, the kinetic forces will oversee a particular Reynolds number. The automatic vaporization due to the friction of the viscose thus becomes insufficient to even out all the disturbances adjacent to the surface of the body, which results in a dynamic instability in the spruce layer. As this instability develops to varying degrees, more severe disturbances occur in Orstarkas, until the entire spruce layer is in strong motion or turbulence.

Olika anordningar och fldrfaranden ha utvecklats tidigare for stabilisering air detta gransskikt, dvs. for att framkalla laminar stromning yid ett Reynolds tal, som ligger ovanfor det vanliga, kritiska talet. AnsattDing ay sugning mot ytan pa en kropp liar visat sig minska gransskikteta tjocklek och darmed ifriktionsmotstandet. Manga under- 2— — sokningar, framfor alit pa vingsektioner, ha genomfOrts under ansattning av sugning genom slitsar i ytan. En av de mest fullstandiga undersOkningarna har utf8rts av Werner Pfenninger, »Investigations on Reductions of Friction on Wings in Particular by Means of Boundary Layer Suction», NAGA TM 1181, 1947. En olagenhet med denna louring ãr, att dessa sugslitsar i ytan maste vara relativt fina med hansyn till ytans jamnhet och salunda sattas igen Offer latt. Various devices and procedures have been developed previously for stabilizing this spruce layer, i.e. to induce laminar flow yid a Reynolds number, which is above the usual, critical number. Employed by sucking against the surface of a body has been shown to reduce the thickness of the spruce layers and thus the frictional resistance. Many examinations, especially on wing sections, have been carried out while applying suction through slots in the surface. One of the most complete investigations has been carried out by Werner Pfenninger, "Investigations on Reductions of Friction on Wings in Particular by Means of Boundary Layer Suction", NAGA TM 1181, 1947. One problem with this louring is that these suction slots in the surface must be relatively fine with hansyn to the smoothness of the surface and salunda set again Sacrifice easily.

En annan utvag for stabilisering ay detta gransskikt har undersokts oeh grundar sig pa principen med energiabsorption med hjalp av artifielell ytdampning. Denna teori har framforts av Max 0. Kramer i uppsatsen »Boundary-Layer Stabilization by Distributed Damping», Journal of the Aeronautical Sciences, juni 1957, s. 459 och 460. Andamalet med detta fors& att losa det alluranna problemet med gransskiktstabilisering ãr att astadkomma en typ av yta .for en fast kropp, vilken verkar automatiskt .och utan ytterligare kraft for att utstracka den laminara gransskiktstrOmningen utover del vanliga overgangsintervallet for Reynolds tal ,och in i den vanliga turbulenszonen. Harvid stiker man astadkomma en yta, som joke .endast bibehaller den laminara stromningen utan även sOker aterstalla denna, da storande ffaktorer ha andrat jamvikten. Another solution for stabilizing this boundary layer has been investigated and is based on the principle of energy absorption by means of artificial surface evaporation. This theory has been put forward by Max 0. Kramer in the essay "Boundary-Layer Stabilization by Distributed Damping", Journal of the Aeronautical Sciences, June 1957, pp. 459 and 460. The purpose of this attempt to solve the all-encompassing problem of spruce layer stabilization is to achieve a type of surface for a solid body which acts automatically and without additional force to extend the laminar boundary layer flow beyond the usual transition interval of Reynolds' speech, and into the ordinary zone of turbulence. In doing so, it is possible to create a surface which, as a joke, only maintains the laminar flow but also seeks to restore it, as disturbing factors have changed the equilibrium.

Kramers losning är grundad pa .det forhallandet, att gransskiktet pa en slat, plan yta, innan det blir turbulent, selektivt forstarker en viss kritisk vagighet, som overgar i en turbulent r5relse, dá den nar en kritisk amplitud. Delta har pavisats av Schubauer och Skramstad i deras uppsats »Laminar Boundary-Layer Oscillations and Stability of Laminar Flow», Journal of Aeronautical Sciences, volym 14, nummer 2, februari 1947, och av Schlichting i »Amplitudenverteilung und Energie Bilanz der kleinen Storungen bei der Plattenstromung», Nachrichten der Gesellschaft der Wissenschaften, Gottingen M.P.K., volym 1, s. 47-78, 1935. Gransskiktets vagighet ger upphov till tryeksvangningar, vid passage farbi en godtycklig punkt pa ytan. Om pa ytan av en nedsankt kropp anbringas ett dampande material, som kan reagera for dessa trycksvangningar, kommer inforandet av denna artificiella dampning att Oka grans- skiktets stabilitet, sa att det kanlami- nart vid hogre Reynolds tal. Utvecklingen av en dampande ythelaggning, som reagerar for dessa utomordentligt sma trycksvangningar och trots detta har en fullstandigt slat yta, ingar i den av Kramer foreslagna lOsningen. Kramer's solution is based on the premise that the spruce layer on a smooth, flat surface, before it becomes turbulent, selectively amplifies a certain critical vagueness, which transitions into a turbulent motion when it reaches a critical amplitude. Delta has been pointed out by Schubauer and Skramstad in their essay "Laminar Boundary-Layer Oscillations and Stability of Laminar Flow", Journal of Aeronautical Sciences, volume 14, number 2, February 1947, and by Schlichting in "Amplitudenverteilung und Energie Bilanz der kleinen Storungen bei der Plattenstromung », Nachrichten der Gesellschaft der Wissenschaften, Gottingen MPK, volym 1, s. 47-78, 1935. Gransskiktets vagighet gives rise to pressure fluctuations, when passing farbi an arbitrary point on the surface. If a vaporizing material is applied to the surface of a submerged body which can react to these pressure fluctuations, the introduction of this artificial vaporization will increase the stability of the spruce layer, so that it is canlaminar at higher Reynolds numbers. The development of a steaming surface coating, which reacts to these extremely small pressure fluctuations and nevertheless has a completely smooth surface, is reflected in the solution proposed by Kramer.

For sin artificiella dampning foreslog Kramer en tryckkanslig ytbelaggning med cellstruktur. Den utmarkte sig f dr ett stort antal inre halrum och. var ,fylld med ett .fluidum av samma allmanna typ som fluidet i gransskiklet, ehuru 1 allmanhet med hogre viskositet. For its artificial steaming, Kramer proposed a pressure-sensitive surface coating with cell structure. It stood out for a large number of inner halls and. was, filled with a fluid of the same general type as the fluid in the spruce shell, although generally of higher viscosity.

Denna fluidumfyllda, flerskiktade ythelaggning var fOrsedd med ett start antal inre kanaler for fortplantningen av tryck i motsvarighet till svangningarna I trycket i gransskiktet under kritiska fOrhallanden. Ytbelagg. ningen var farsedd ,med ett slat, hojligt, tryckkansligt ytskikt eller membran for kontakt med gransskiktet. Kramers fluidumfyllda halrum Toro relativt manga och relativt sma i tvarsnittsarean 1 en ytterzon nara ytskiktet samt voro ,farre och st5rre langre in. Energien avleddes i star utstrackning genom friktionsmotstand till det oscillerande flodet dessa ,fluidumfyllda halrum. Det är uppenbart, att detta innebar en svar ,och dyrbar be-handling av ytan, sarskilt dA det Ar fraga om stora areor. Det skulle salunda vara mycket betungande att fasta en sadan cellformig belaggning pa ytan as en flygplanskropp. This fluid-filled, multilayer surface coating was provided with an initial number of internal channels for the propagation of pressure corresponding to the fluctuations in the pressure in the spruce layer under critical conditions. Surface coating. The surface was sealed, with a smooth, hollow, pressure-sensitive surface layer or membrane for contact with the spruce layer. Kramer's fluid-filled cavities Toro relatively many and relatively small in the cross-sectional area 1 an outer zone near the surface layer and were, farther and larger longer in. The energy was diverted to a large extent by frictional resistance to the oscillating river, these fluid-filled cavities. It is obvious that this meant an answer, and expensive treatment of the surface, especially since it is a question of large areas. It would thus be very onerous to attach such a cellular coating to the surface as an aircraft fuselage.

Andamalet med foreliggande uppfinning är att uppna denna artificiella ytdampning med hjalp av en ytbelaggning, som är Hit och billig att anbringa. Belaggningen okar gransskiktets stabilitet .och gOr det mOjligt for gransskiktet att forbli laminart aven vid hoga Reynolds tal och uppvisar samtidigt den erfordertiga ytjamnheten. The object of the present invention is to achieve this artificial surface evaporation with the aid of a surface coating which is Hit and inexpensive to apply. The coating increases the stability of the spruce layer and makes it possible for the spruce layer to remain laminar even at high Reynolds numbers and at the same time exhibits the required surface evenness.

Enligt uppfinningen foreslas, att gransskiktet skall stabiliseras .och friktionsmotstandet mot ett foremal, som ror sig i ett fluidum salunda minskas genom att pa foremalet anbringas en tunn belaggning av ett ,amne, som i och for sig har onskade aterstudsnings- och elasticitetsegenskaper. Denna enda belaggning kommer salunda att fylla samma uppgifter som Kramers ytbelaggning ,och hans fluidumfyllda underlag. Det har visat sig, att anbringandet av en sadan tunn, elastisk ylbelaggning resulterar i en sensationell minskning av friktionsmotsthndet. According to the invention, it is proposed that the spruce layer be stabilized and the frictional resistance to a mold moving in a fluid thus reduced by applying to the mold a thin coating of a blank which per se has desired rebound and elastic properties. This single coating will thus fill the same tasks as Kramer's surface coating, and his fluid-filled substrate. It has been found that the application of such a thin, elastic wool coating results in a sensational reduction in frictional resistance.

Denna tunna, elastiska ytbelaggning kan besta av en elastomer eller ett gummiartat material. For .absorption av maximum av oscillationsenergi, da. gransskiktstromningen har en benagenhet att sla orn till turbulent, maste detta skikt ha en tjocklek av minst 1,59 nun och fOljande fysikaliska egenskaper: 1) en energiabsorption per studs av 0,5-0,9 och 2) en elasticitetsmodul av c:a 1,75-24,5 kp/cm2. En minskning av friktionsmotstandet pa % her uppnatts i vatten genom installning av den elastiska belaggningens elasticitetsmodul och aterstudsning. En minskning pa upp till 70-80 9-'0 ar teoretiskt an.Ojlig. For uppnaende av denna minskning Or det emellertid nodvandigt, att den elastiska belaggningen har en elasticitetsmodul och energiabsorption inom de angivna granserna. This thin, elastic surface coating can consist of an elastomer or a rubbery material. For .absorption of maximum of oscillation energy, then. The spruce layer flow has a tendency to strike turbulent, this layer must have a thickness of at least 1.59 nun and the following physical properties: 1) an energy absorption per bounce of 0.5-0.9 and 2) a modulus of elasticity of approx. 1.75-24.5 kp / cm2. A reduction of the frictional resistance of% here achieved in water by installing the modulus of elasticity of the elastic coating and rebound. A reduction of up to 70-80 9-'0 is theoretically possible. In order to achieve this reduction, however, it is necessary that the elastic coating has a modulus of elasticity and energy absorption within the specified limits.

Energiabsorptionen per studs eller aterstuds utgor ett matt pa mekanisk hysteresis. Den kan exempelvis 'bestammas genom att man slapper en stalkula pa ett tjockt provstycke av det material, .av vilket belaggningen skall tillverkas, och mater aterstudsningen. En - 178 aterstudsning pa 0,10 svarar mot en energiabsorption pa 0,90. Ifragavarande varden ha erhallits vid slappning av en kula pa 20 g med en diameter av 12,7 mm I ett glasror !frail en hojd av 101,6 mm pa de overdragna ytorna av modellerna. Den forsta studsens hojd mattes. Sankningen av hojden 1 forhallande till den ursprungliga5jden utgor 'ett matt pa den absorberade energien enligt ekvationen energiabsorption = 1 -- aterstudsning/urspunglig Elasticitetsmodulen utgor forhallandet mellan den spanning, som en kropp kan utharda, och den patryckta spanningen. I detta sam.- manhang definieras den pa foljande satt: begynnelselutningen av spannings-tojningskurvan extrapoleras fran borjan till den punkt pa abscissan, sam representerar 100 % forlangning. Vardet pa den spanning, som svarar mot .denna punkt, utgor »modulen» I detta .sammanhang. Denna modul benamnes ibland »tangent»-modulen. The energy absorption per bounce or rebound constitutes a measure of mechanical hysteresis. It can be determined, for example, by releasing a steel ball on a thick sample of the material from which the coating is to be made, and feeding the rebound. A - 178 rebound of 0.10 corresponds to an energy absorption of 0.90. The value in question was obtained when slackening a ball of 20 g with a diameter of 12.7 mm in a glass tube from a height of 101.6 mm on the coated surfaces of the models. The height of the first spigot is matted. The lowering of the height 1 relative to the original height is a measure of the absorbed energy according to the equation energy absorption = 1 - rebound / original The modulus of elasticity is the ratio between the voltage that a body can withstand and the printed voltage. In this context, it is defined as follows: the initial slope of the stress-strain curve is extrapolated from the beginning to the point on the abscissa, which represents 100% elongation. The value of the voltage corresponding to this point constitutes the "module" in this context. This module is sometimes referred to as the "key" module.

Uppfinningen kommer i det foljande 'att beskrivas narmare med hanvisning till bifogade ritning. Fig. 1 visar schematiskt en model', som har anvants vid stadium av detta fonfarande for gransskiktstabildsering. Fig. 2 utgor ett diagram i logaritmisk skala och visar variationerna i ,motstandskoefficienten CD ,som en funktion av Reynolds tal R for olika typer av ytbelaggningar. Fig. 3 Sr ett diagram i logaritmisk skala, vilket visar den teoretiska andringen av motstandskoefficienten CD uttryckt i Reynolds tal R Over ett mycket storre intervall samt for fullstandigt laminar och fullstandigt turbulent str5mning. Fig. 4 Sr ,ett diagram, som visar andringen av motstandskoefficienten CD for en yta med ett elastiskt overdrag 1 forhallande till en hard yta som en funktion av det inverterade vardet av ,elastieitetsmodulen for den elastiska belaggningen vid olika Reynolds tal. The invention will be described in more detail below with reference to the accompanying drawing. Fig. 1 schematically shows a model which has been used at the stage of this form procedure for boundary layer formation. Fig. 2 is a diagram on a logarithmic scale and shows the variations in, the coefficient of resistance CD, as a function of Reynolds number R for different types of coatings. Fig. 3 is a diagram on a logarithmic scale, showing the theoretical change of the coefficient of resistance CD expressed in Reynolds' number R over a much larger range and for completely laminar and completely turbulent flow. Fig. 4 Sr, a diagram showing the change of the coefficient of resistance CD for a surface with an elastic coating 1 relating to a hard surface as a function of the inverted value of, the modulus of elasticity of the elastic coating at different Reynolds numbers.

For belysning av ifordelarna med den enligt fOreliggande uppfinning foreslagna ytbelaggningen tillverkades en modell enligt fig. 1. Dennas totala langd L var 94,7 cm och den cylindriska delens langd a var 67,3 cm. Spetsens langd b var 27,4 cm. Den cylindriska de-lens ytterdiameter d var 6,35 cm oberoende av ytbelaggningens typ. Olika ytbelaggningar anbragtes endast Mom det skuggade omradet. Detta borjade ph ett stycke e av 2,54 cm fran modellens akterande och dess framre ande lag ett stycke e av 0,32 cm akter cm spetsdelens akterande. Den cylindriska delens framande var gangad for inskruvning av en noskon av solid nylon. Noskonens form vat-des sa, att dess gransskikt skulle vara stabiliserat vid en negativ tryckgradient och ett yerkligt laminart gransskikt med sakerhet skulle overfOras till det cylindriska roret. Noskonens exakta dimensioner frarnga av 15Ijande tabell: 277 31,7 mm 276,3 mm 26,7 » 259,0 » 22,1 » 234,0 » 17,9 » 208,0 14,1 » 183,0 10,8 » 157,3 7,9 » 132,0 5,» 106,8 3,» 81,2 1,9 » 55,9 0,9 » 30, 0,2 » 5,1 Krokningsradien yid y = 276,3 mm var 2,54. To illustrate the advantages of the surface coating proposed according to the present invention, a model according to Fig. 1 was manufactured. Its total length L was 94.7 cm and the length a of the cylindrical part was 67.3 cm. The length b of the tip was 27.4 cm. The outer diameter d of the cylindrical part was 6.35 cm, regardless of the type of surface coating. Various coatings were applied only Mom the shaded area. This started ph a piece e of 2.54 cm from the stern of the model and its front layer a piece e of 0.32 cm aft cm stern of the tip part. The front of the cylindrical part was threaded to screw in a nylon cone made of solid nylon. The shape of the nose cone was watered so that its spruce layer would be stabilized at a negative pressure gradient and a truly laminar spruce layer would be securely transferred to the cylindrical tube. The exact dimensions of the nose cone differ from the following table: 277 31.7 mm 276.3 mm 26.7 »259.0» 22.1 »234.0» 17.9 »208.0 14.1» 183.0 10.8 »157.3 7.9» 132.0 5, »106.8 3,» 81.2 1.9 »55.9 0.9» 30, 0.2 »5.1 Curving radius yid y = 276.3 mm was 2.54.

Olika elastiska belaggningar, sam voro valda for att belysa 'foreliggande uppfinning, anbragtes pa modellerna pa ,foljande satt: ett cylindriskt ror, vars ,utvandiga diameter var lika mycket mindre an den slutliga provmodellens ytterdiameter som tvâ ganger belaggningens avsedda tjocklek, anbragtes koaxiellt i en cylindrisk form med samma langd forsedd med lamplig tillslutning i ena anden. En elastomer, sasom flytande polyuretangummi, halides sedan i detta ringformiga mellanrum 'och fick hardas till fast tillstand in situ. Ytterformen avlagsnades sedan. Den hade fore gjuLningen behandlats med ett slappmedel, sasom en kiselolja, sa att gummit hindrades ;frau att fastna. Sasom bekant aro elastomera polyuretanmaterial vanligen baserade pa polyestrar eller polyetrar i kombination med ett diisoeyanat, sasom belyses i det foljande I samband flied beskrivningen av provmodell 1. Som exempel pa en lamplig polyester kan namnas den, som bildas genom forestring av 27 'moler adipinsyra med 28 ,moler dietylenglykol och 2 moler trimetyloletan, vilken har tillsatts fOr att medfora en viss natbildning, sa att det bildades en polyester ,med en molvikt av c:a 2000, ,ett syratal ay c:a 65 och ett hydroxyltal ay c:a 2. Various elastic coatings, selected to illustrate the present invention, were applied to the models as follows: a cylindrical tube, the outer diameter of which was as much smaller as the outer diameter of the final test model as twice the intended thickness of the coating, was placed coaxially in a cylindrical shape of the same length provided with a suitable closure in one end. An elastomer, such as liquid polyurethane rubber, is then halided in this annular space and allowed to solidify in situ in situ. The outer mold was then removed. It had previously been treated with a laxative, such as a silicone oil, so that the rubber was prevented from sticking. As is known, elastomeric polyurethane materials are usually based on polyesters or polyethers in combination with a diisoyanate, as illustrated in the following In connection with the description of sample model 1. Examples of a suitable polyester are those formed by esterification of 27 'moles of adipic acid with 28, moles of diethylene glycol and 2 moles of trimethylolethane, which has been added to cause a certain night formation, so that a polyester was formed, having a molecular weight of about 2000,, an acid number of about 65 and a hydroxyl number of about 2.

Tre provmodeller ,och en obelagd kontrollmodell tillverkades for att belysa fordelarna med .foreliggande uppfinning. Den belaggning, som anvandes f or provmodell loch visade sig vara sarskilt effektiv, utgjordes av ett polyuretangummi framstallt genom blandning av 700 g av en polyester, vilken forsaljes under benamningen »Multron R-2'6», har ett hydroxyltal av 63 och ett syratal ay 1,4. Denna polyester Sr framstalld ay adipinsyra och dietylenglykol med en ringa mangd av en trihydroxiforening, i huvudsak sasom har beskrivits ovan, och 55,9 g toluendiisocyanat vid 1° C. Denna blandning halides i en form enligt ovan och hardades Over natten vid 135° C. Den salunda framstallda gummibelaggningen hade en elasticitetsmodul ay 10, kp/cm2 och en energiabsorption per studs av 0,70, sa att den gott och vSl foil Mom de foreskrivna granserna. Belaggningen var 4,76 mm tjock. Three sample models, and an uncoated control model, were fabricated to illustrate the benefits of the present invention. The coating used for the test model and proved to be particularly effective was a polyurethane rubber made by mixing 700 g of a polyester, which is pre-sold under the name "Multron R-2'6", has a hydroxyl number of 63 and an acid number ay 1.4. This polyester Sr is prepared from adipic acid and diethylene glycol with a small amount of a trihydroxy compound, essentially as described above, and 55.9 g of toluene diisocyanate at 1 ° C. This mixture is halided in a mold as above and cured overnight at 135 ° C. The thus produced rubber coating had a modulus of elasticity ay of 10, kp / cm2 and an energy absorption per bounce of 0.70, so that it well and vSl foil Mom the prescribed limits. The coating was 4.76 mm thick.

— — Provmodell 2 hade en belaggning, som ocksa var gjuten enligt ovan, hade en elasticitetsmodul av 2,45 kp/cm2, energiabsorption per studs av 0,88 samt en tjocklek av 4,76 mm. Aven derma belaggning foil Mora de uvan angivna granserna. For jamforelse framstalldes provm.odell 3 med en 4,76 mm tjock belaggning med en elasticitetsmodul av endast 1,05 kp/cm2, varfar den salunda fon utanfor ramen enligt uppfinningen, och en energiabsorplion per studs av 0,88. - - Test model 2 had a coating, which was also cast as above, had a modulus of elasticity of 2.45 kp / cm2, energy absorption per bounce of 0.88 and a thickness of 4.76 mm. Also this coating foil Mora the above stated boundaries. For comparison, sample model 3 was prepared with a 4.76 mm thick coating with a modulus of elasticity of only 1.05 kp / cm 2, which rotates outside the frame according to the invention, and an energy absorption per bounce of 0.88.

De .ovan beskrivna gummibelaggningarna Otos av bekvamlighetsskal ur .flytande polyuretangummi. De kunde emellertid lika val ha framstallts genam formpressning .och ytbehandling, av fast polyuretangummi eller av nagot natur- eller konstgummi, som kan modereras sa, att det far lamplig elastieitetsmodul .och mekanisk hysteresis. Det liar visat sig, .att den uppnadda minskningen av friktionsmotstandet endast beror pa den elastiska belaggningens fysikaliska egenskaper, sarskilt elasticitetsmodulen och aterstudsningen, och icke pa nagot slit pa gummits kemiska sammansattning eller det salt, pa vilket gummit har anbragts. Belaggningen maste ha en tjocklek av minst 1,59 mm for ,att vara verksam. The Otos rubber coatings described above of convenience shells made of liquid polyurethane rubber. However, they could equally well have been produced by compression molding and surface treatment, of solid polyurethane rubber or of some natural or artificial rubber, which can be moderated so that it has a suitable modulus of elasticity and mechanical hysteresis. It has been found that the reduction in frictional resistance achieved depends only on the physical properties of the elastic coating, in particular the modulus of elasticity and the rebound, and not on any wear on the chemical composition of the rubber or the salt on which the rubber has been applied. The coating must have a thickness of at least 1.59 mm in order to be effective.

Provmodellen enligt fig. 1 bogserades genom vatten med olika hastighet .och motstandet mattes. En modell med samma dimensioner och hard yta anvandes som kontroll. Fors5ksresultaten aterges i fig. 2 genom avsattning av motstandskoefficienten CD mot Reynolds tal R. Reynolds tal R beraknas enligt formeln R L Ho) ft I vilken L = modellens langd U. = modellens hastighet i .fluidet fluidets densitet roch fluidets viskositet Matstandskoefficienten CD beralinas enligt ekvationen CD == A 9912 Up2 vilken D = uppmatt motstand °eh. A = modellens friktionsyta. The test model of Fig. 1 was towed through water at different speeds, and the resistance was reduced. A model with the same dimensions and hard surface was used as a control. The test results are shown in Fig. 2 by plotting the coefficient of resistance CD against Reynolds number R. Reynolds number R is calculated according to the formula RL Ho) ft In which L = model length U. = model velocity in fluid fluid density and fluid viscosity Food coefficient CD is calculated according to the equation CD == A 9912 Up2 which D = measured resistance ° eh. A = friction surface of the model.

I fig. 2 visas forutom resultaten fran de genomforda .forsiiken Oven den klassiska CD- kurvan avsatt mot R-kurvan far fullstandigt turbulent och fullstandigt laminar stromning Mom ifragavarande zon. Dessa bagge kurvor visa liksom fig. 3, att de teoretiska fakta betraffande forhallandet Indian motstandskoefficienten CD .och Reynolds tal R aro valkanda. De teoretiska kurvorna beskriva den friktion, sam erhalles mellan slata, plana och harda ytor och de vatskor eller gaser, i vilka de aro nedsankta. Denna friktion uttryckt i motstandskoefficienten CD utgor en ren funktion av Reynolds tal R och stromningens lanainara eller turbulenta typ. Sasom framgar air fig. 3 foljer under c:a R = 6 friktionskoefficienten CD-lagen for laminar friktion och sjunker med okande Reynolds tal. Over ungefar R = 0 blir gransskiktet plotsligt turbulent, vilket medlar en hastig Mining och en mycket langsammare sankning av friktionskoefficienten CD, .da Reynolds tal Okar. Vid ett Reynolds tal av c:a 6 Or det verkliga friktionsmutstandet i turbulent stromning 15 ganger stone An det skulle vara, om gransskiktet skulle kunna farbli laminart upp till detta Reynolds tal. Vid viktiga tillampningar Mom aerodynamiken och hydrodynamiken, sasom flygplans och fartygs rOrelser i motsvarande fluida, Or det fraga om Reynolds tal av c:a 7 till , sasom framgar av fig. 3. Det Ar uppenbart, att man vid alla dessa tillampningar skulle kunna draga stor nytta av at-Order, som skulle ge laminar gransskiktstromning Mom det angivna intervallet far Reynolds tal. Fig. 2 shows, in addition to the results from the experiments carried out, that the classical CD curve plotted against the R-curve has a completely turbulent and completely laminar flow in the zone in question. These ram curves show, as in Fig. 3, that the theoretical facts concerning the ratio Indian resistance coefficient CD .and Reynolds number R aro valkanda. The theoretical curves describe the friction obtained between smooth, flat and hard surfaces and the liquids or gases in which they are immersed. This friction expressed in the coefficient of resistance CD constitutes a pure function of Reynolds number R and the lanainara or turbulent type of the flow. As shown in Fig. 3, below the approximate R = 6 coefficient of friction, the CD law for laminar friction follows and decreases with increasing Reynolds number. Over approximately R = 0, the spruce layer suddenly becomes turbulent, which mediates a rapid Mining and a much slower decrease in the coefficient of friction CD, .da Reynolds tal Okar. At a Reynolds number of about 6 Or the actual frictional resistance in turbulent flow 15 times stone It would be if the spruce layer could become laminar up to this Reynolds number. In important applications, including aerodynamics and hydrodynamics, such as the movements of airplanes and ships in corresponding fluids, or the question of Reynolds' speech of c. 7 to, as shown in Fig. 3. It is obvious that in all these applications it would be possible to draw great benefit of at-Order, which would give laminar spruce layer flow Mom the specified interval father Reynolds speech.

De vid forsok med provmodellerna 1-3 och kontrollmodellen erhallna resultaten visas i fig. 2 med kurvor med den angivna inneborden. SjAlva forsOksvardena Oro Oven utsatta. Provmodell 1 visade sig ha hattre motstandskoeffielent On kontrollmodellen -yid alla undersakta hastigheter och uppvisade en minskning av friktionsmotstandet pa upp till a:a 20 %. Provmodell 2 visade en minskning av friktionsmotstandet vid lag hastighet och en mindre okning av motstandet vid hogre hastighet. Provmodell 3, som faller utanfor ramen ,for foreliggande uppfinning, eftersom doss elastieitetsmodul var endast 1,05 kp/cm2, var ineffektiv betraffande minskningen air friktionsmotstandet Sasom framgar air fig. 2 fororsakade den tvart .om en stark Ruing air friktionsmotstandet. Det Or salunda uppenhart, att den lagsta elasticitetsmodul, som kan medfora en minskning air friktionsmotstandet, Or c:a 1,75 kp/cm2. The results obtained in experiments with the test models 1-3 and the control model are shown in Fig. 2 with curves with the indicated inner tables. The Forsvksvardena Oro Oven themselves exposed. Sample model 1 was found to have a higher resistance coefficient on the control model -yid all investigated velocities and showed a reduction of the frictional resistance of up to about 20%. Test model 2 showed a decrease in the frictional resistance at low speed and a smaller increase in the resistance at higher speed. Sample model 3, which falls outside the scope of the present invention, since the modulus of elasticity was only 1.05 kp / cm 2, was ineffective in reducing the air frictional resistance. As shown in Fig. 2, it caused the opposite of a strong Ruing air frictional resistance. It is thus clear that the lowest modulus of elasticity which can lead to a reduction in the frictional resistance is about 1.75 kp / cm2.

I fig. 4 visas motstandskoefficientens variation vid olika Reynolds tal for en yta med en elastisk belaggning i forhallande till dess variation for en hard yta, kontrollmodellen, som en funktion air det inverterade vardet .for den elastiska belaggningens elasticitetsmodul. Da elasticitetsmodulen narmar sig aandligheten, den teoretiskt harda belaggningen, narmar sig elasticitetsmodulens inverterade varde 0 och narmar sig ordinatan vardet 1,0, sasom visas i fig. 4. Am diagrammet framgar, att motstandskoefficienten CD gar genom ett minimum -vid en viss elasticitetsmodul och att laget for delta minimum beror pa. Reynolds Lal. Bestamningen air den basta elastieitetsmodulen beror salunda pa Reynolds tal, varvid generellt hogre Reynolds tal krava belaggningar med hOgre modul. Air diagrammet framgar vidare, att ytbelaggningar, for vilka elastieitetsmodulens inverterade varde Egger — — vid c:a 0,04-0,003 Aro verksamma vid minskning av friktionsmotstandet vid de Rey- nolds tal, som are av intresse i delta sammanhang. Man har foljaktligen -valt gransvardena 1,7,och 24,5 kp/cm2 for det foredragna intervallet for ythelaggningens elasticitetsmodul. Fig. 4 shows the variation of the coefficient of resistance at different Reynolds numbers for a surface with an elastic coating in relation to its variation for a hard surface, the control model, as a function of the inverted value for the modulus of elasticity of the elastic coating. As the modulus of elasticity approaches the spirituality, the theoretically hard coating approaches the inverted value 0 of the modulus of elasticity and approaches the ordinate value of 1.0, as shown in Fig. 4. The diagram shows that the coefficient of resistance CD passes through a minimum at a certain modulus of elasticity. that the team for participating minimum depends on. Reynolds Lal. The determination of the best modulus of elasticity thus depends on Reynolds 'number, with generally higher Reynolds' numbers requiring coatings with higher modulus. The air diagram further shows that surface coatings for which the modulus of elasticity inverted were Egger - - at about 0.04-0.003 Aro are effective in reducing the frictional resistance at de Reynolds numbers, which are of interest in delta contexts. Accordingly, the spruce values 1.7 and 24.5 kp / cm2 have been selected for the preferred range for the modulus of elasticity of the surface layer.

Om ,optimala resultat skola erhallas, bor Oven energiabsorptionen per studs Ras, dã Reynolds tal stiger. Det optimala intervallet fOr energiabsorption per studs ligger vid 0,5 ---0,9. If optimal results are to be obtained, the energy absorption per bounce Ras should increase, as Reynolds' number increases. The optimal range for energy absorption per bounce is 0.5 --- 0.9.

Ytbelaggningarna enligt foreliggande uppfinning Oro verksamma Oven i andra medier An vatten, exempelyis laft, ,och vid vida varierande Reynolds tal, sasom det intervall, som visas d fig. 2 (3X8 till 1,1X7). The coatings of the present invention are also active in other media. In water, for example, and at widely varying Reynolds numbers, such as the range shown in Fig. 2 (3x8 to 1.1x7).

Detta satt att stabilisera gransskiktet kan tillampas ph mama olika ,omrhden i praktiken. Torpeders, undervattensrobotars ,och undervattenshatars friktionsmotstand minskas vid tillampning air principerna enligt foreliggande uppfinning. I samband med undervattensbatar Or denna typ av gransskiktsstabilisering air sarskilt intresse av en annan orsak. Forutom att minska motstandet yid hog hastighet andrar den Oven undervattensbatens akustiska egenskaper. Ph grund air elimineringen ay det turbulenta gransskiktet minskas starkt det huller, som fiirorsakas genom undervattensbatens rOrelse. Samtidigt minskas reflektionen av ljudsignaler, sarskilt om dessa tratif a undervattensbaten ungefar parallellt med dem langdaxel. Derma akastiska verkan Or sh framtradande, att en undervattensbat .forsedd med en belaggning enligt föreliggande uppfinning bl'ir »osynlig» Mr undervattensavlyssning och samtidigt utsander sh ringa ljudmangd, att den passiva malfoljning, som grundar sig ph det ljud, sum utAndes av malet, Oven blir oanvandbar. This way of stabilizing the spruce layer can be applied to ph mama different, areas in practice. The frictional resistance of torpedoes, underwater robots, and underwater haters is reduced upon application of the air principles of the present invention. In connection with underwater benefits Or this type of spruce layer stabilization air particular interest for another reason. In addition to reducing resistance at high speeds, the Oven's underwater acoustic properties change. Due to the air elimination of the turbulent spruce layer, the gaps caused by the movement of the underwater bath are greatly reduced. At the same time, the reflection of sound signals is reduced, especially if these tratif a submarine boat approximately parallel to them long axis. This acoustic effect is that an underwater bath provided with a coating according to the present invention becomes "invisible" underwater listening and at the same time emits a small amount of sound, that the passive moth tracking, which is based on the sound emitted by the grind, The oven becomes unusable.

Undervattenskroppen ph segelbhtar ,och motorbatar kan, ,om den forses med en ytbelaggning i enlighet med foreliggande uppfinning, bibringas avsevart mindre motstand. Surfbrador ,och vattenskidor forbattras Oven. The underwater body ph sail boats, and engine boats can, if provided with a surface coating in accordance with the present invention, be imparted considerably less resistance. Surf boards and water skis are improved.

Detta satt att minska motstandet kan a-ven anvandas for att skara ned friktionsmotstandet for stora gummibehallare, vilka ,anvandas for transport av bensin ,och olja under vattnet. In order to reduce the resistance, it can also be used to cut down the frictional resistance of large rubber containers, which are used for transporting petrol and oil underwater.

De inre ytor i pumpar och rorledningar, som komma I kontakt med fluidum, kunna Oven behandlas for okning air effektiviteten. The internal surfaces of pumps and pipelines that come into contact with fluid can also be treated to increase air efficiency.

Uppfinningen kan tillampas pa ,flygplan yid bade underljud- och overljudhastighet. Gransskiktstabiliseringen kommer att forbattra underljudhastighetsplan genom minskning av friktionsmotstandet. Overljudplan ‘forbattras icke endast betraffande minskningen av frik tionsmotstandet utan Oven genom minskning av det varme, sum alstras av detsamma. Eftersom den sa. kallade vanrnebarriaren, som upptrader vid tiverljudhastigheter, torde utOra det .allvarligaste, tekniska hindret vid utveckling av overljudplan, kommer detta f Or-f arande for stabilisering av gransskiktet att bill alit viktigare. The invention can be applied to aircraft with both sonic and supersonic speeds. The spruce layer stabilization will improve the subsonic velocity plane by reducing the frictional resistance. Noise planes' are improved not only in terms of reducing the frictional resistance but also by reducing the heat generated by it. Because it said. The so-called water barrier, which occurs at supersonic speeds, is likely to be the most serious technical obstacle to the development of supersonic planes, and this will make the stabilization of the spruce layer more important.

I vissa fall kan det vara lampligt att Overdraga ytbelaggningen enligt foreliggande uppfinning med en tunn hud air gummi, exempelvis neopren, som Or bestandigt mot oxide-ring roch notning. Denna tunna had komplicerar uppfinningen endast obetydligt och kan vissa fall ge.en battre och anvandbarare produkt. In some cases, it may be appropriate to coat the coating of the present invention with a thin skin air rubber, for example neoprene, which is resistant to oxidation and abrasion. This thin hair complicates the invention only insignificantly and can in some cases give a better and more usable product.

Claims

Patent claim:

A method of reducing air frictional resistance to a mold moving in a fluid, characterized in that a thin, elastic coating with an energy absorption per bounce of air 0.5-0 is applied to the surface of the mold which comes into contact with the fluid. 9, and a modulus of elasticity in the range of 1,7524.5 kp / cm2.

2. A method according to claim 1, characterized in that an elastomeric coating is used for the elastic coating.

Procedure according to patent claim 2, characterized in that the elastomeric coating is made at least 1.6 frames thick.

4. Procedure according to any prior patent claim, characterized in that the flow of fluid around the form is characterized by Reynolds' number Mom, ranging from 3X6 to 1.1X7.

5. A device according to any one of the preceding claims, set forth to reduce the frictional resistance of a mold while moving in a fluid, characterized by a thin, elastic coating applied to the surface of the forearm which comes into contact with the fluid, the coating having an energy absorption per bounce of 0.5-0.9 and a modulus of elasticity in the range 1.75-24.5 kp / cm2.

Device according to claim 5, characterized in that the elastic coating is made of an elastomeric coating.

7. Device according to patent claim 6, characterized in that the elastomeric coating Or at least 1.6 mm * at.

Device according to claim 5, characterized in that the fluid flow around the foremal is characterized by Reynolds' number in the range from 3X6 to 1.1X7. Request publications: