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Dimensionless quantity

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is commonly used in fluid mechanics to characterize flow, incorporating both properties of the fluid and the flow. It is interpreted as the ratio of inertial forces to viscous forces and can indicate flow regime as well as correlate to frictional heating in application to flow in
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may be defined as a ratio of volumes (volumetric moisture, m⋅m, dimension L⋅L) or as a ratio of masses (gravimetric moisture, units kg⋅kg, dimension M⋅M); both would be unitless quantities, but of different dimension.
1045:– defined as the ratio of momentum diffusivity (kinematic viscosity) and mass diffusivity, and is used to characterize fluid flows in which there are simultaneous momentum and mass diffusion convection processes. 1479: 474:– they are inversely proportional). If the dimensionless combinations' values changed with the systems of units, then the equation would not be an identity, and Buckingham's theorem would not hold. 1751: 1452: 854:
can be normalized in this fashion. For example, the values of the following constants are independent of the system of units, cannot be defined, and can only be determined experimentally:
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theorem indicates that validity of the laws of physics does not depend on a specific unit system. A statement of this theorem is that any physical law can be expressed as an
1113: 1179: 1146: 985:– parameter used in the context of special relativity for time dilation, length contraction, and relativistic effects between observers moving at different velocities 1080: 652:
of quantities that are not dimensionless, but whose dimensions cancel out in the mathematical operation. Examples of quotients of dimension one include calculating
1082:, is the ratio of the heat release rate of a fire to the enthalpy of the gas flow rate circulating through the fire. Accidental and natural fires usually have a 1039:) is a dimensionless number used in mass-transfer operation. It represents the ratio of the convective mass transfer to the rate of diffusive mass transport. 355:
as a physical unit. The idea was rebutted on the grounds that such a change would raise inconsistencies for both established dimensionless groups, like the
2347: 1694: 1017:(Da) – used in chemical engineering to relate the chemical reaction timescale (reaction rate) to the transport phenomena rate occurring in a system. 372: 219:, the use of dimensionless parameters is evident in geometric relationships and transformations. Physics relies on dimensionless numbers like the 2274: 1335: 240: 470:
involving only dimensionless combinations (ratios or products) of the variables linked by the law (e. g., pressure and volume are linked by
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may represent dimensionless quantities. They can represent discrete quantities, which can also be dimensionless. More specifically,
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There have been periodic proposals to "patch" the SI system to reduce confusion regarding physical dimensions. For example, a 2017
74: 423: 55: 2365: 1023:– describes the relationship between diffusion and reaction rate in porous catalyst pellets with no mass transfer limitations. 81: 2085: 2028: 1987: 1489: 1462: 304:
contributed to the understanding of dimensionless numbers in physics. Building on Rayleigh's method of dimensional analysis,
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such as ppm (= 10), ppb (= 10), and ppt (= 10), or perhaps confusingly as ratios of two identical units (
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Johansson, Ingvar (2010). "Metrological thinking needs the notions of parametric quantities, units and dimensions".
431: 1319: 1266: 971: 803: 70: 1011:– ratio of plasma pressure to magnetic pressure, used in magnetospheric physics as well as fusion plasma physics. 793: 427: 59: 2215: 1294: 888: 17: 322:
Numerous dimensionless numbers, mostly ratios, were coined in the early 1900s, particularly in the areas of
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Webb, J. K.; King, J. A.; Murphy, M. T.; Flambaum, V. V.; Carswell, R. F.; Bainbridge, M. B. (2011-10-31).
516:. For the purposes of the experimenter, different systems that share the same description by dimensionless 874: 1250:
is the measurement of the proportional change of an economic variable in response to a change in another
1979: 1281: 1148:. Fires originating from pressured vessels or pipes, with additional momentum caused by pressure, have 560: 2245: 2219: 1776: 1253: 929: 661: 1085: 95: 724: 412: 267: 177: 1904: 1376: 866: 416: 228: 48: 1151: 1118: 861:, a measure of physical deformation defined as a change in length divided by the initial length. 391: 309: 1256:
is a dimensionless ratio used in epidemiology to quantify the transmissibility of an infection.
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International vocabulary of metrology — Basic and general concepts and associated terms (VIM)
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that align with another system, these quantities do not necessitate explicitly defined
138: 2308: 2077: 997:– ratio of the speed of an object or flow relative to the speed of sound in the fluid. 2338: 2320: 2145: 2133: 2129: 2024: 2010: 1983: 1912: 1812: 1804: 1735: 1727: 1622: 1614: 1544: 1485: 1458: 1433: 1429: 1237: 851: 681: 248: 232: 154: 1824: 1356: 359:, and for mathematically distinct entities that happen to have the same units, like 2328: 2304: 2196: 2159: 2125: 2020: 1951: 1900: 1794: 1785: 1747: 1719: 1702: 1674: 1666: 1640: 1606: 1575: 1540: 1536: 1425: 1206: 1029:– characterizes the range of angles over which the system can accept or emit light. 811: 780: 740: 577: 348: 305: 297: 158: 1932:"On Physically Similar Systems; Illustrations of the Use of Dimensional Equations" 1645:"On physically similar systems; illustrations of the use of dimensional equations" 1969: 1649: 1610: 1048: 1032: 839: 831: 807: 637: 625: 601: 573: 356: 323: 316: 220: 1876: 1845: 1405: 2163: 2016:
Development of Mathematical Cognition: Neural Substrates and Genetic Influences
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is a related concept in statistics. The concept may be generalized by allowing
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A History of the Circle: Mathematical Reasoning and the Physical Universe
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having equal dimensions in numerator and denominator are actually only
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is a related linguistics concept. Counting numbers, such as number of
892: 716: 497: 379:", but the idea of just introducing a new SI name for 1 was dropped. 289: 244: 196: 1799: 1780: 1723: 401: 37: 1507:"Indications of a Spatial Variation of the Fine Structure Constant" 900: 673: 553: 517: 513: 204: 2223: 1523: 2185:"Zur Elektrodynamik bewegter Körper [AdP 17, 891 (1905)]" 1564:"Zur Elektrodynamik bewegter Körper [AdP 17, 891 (1905)]" 732: 704: 685: 548: 337: 2216:"NRL Plasma Formulary: Dimensionless Numbers of Fluid Mechanics" 2360: 1481:
EBOOK: Fluid Mechanics Fundamentals and Applications (SI units)
896: 823: 712: 360: 352: 319:'s previous work) to formalize the nature of these quantities. 189: 181: 798:
Certain universal dimensioned physical constants, such as the
604:. In mathematics, the "number of elements" in a set is termed 2054:"ISO 80000-1:2022(en) Quantities and units — Part 1: General" 1357:"SI Brochure: The International System of Units, 9th Edition" 1210: 653: 649: 344: 185: 146: 1870:"BIPM Consultative Committee for Units (CCU), 16th Meeting" 1839:"BIPM Consultative Committee for Units (CCU), 15th Meeting" 827: 819: 719:
are defined as ratios of quantities of the same kind. In
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Dimensionless quantities play a crucial role serving as
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led significant developments in the modern concepts of
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It has been argued that quantities defined as ratios
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ratio of the mass of any given elementary particle,
1593:Ghosh, Soumyadeep; Johns, Russell T. (2016-09-06). 787: 188:, derived from the universal ratio of 2π times the 62:. Unsourced material may be challenged and removed. 1173: 1140: 1107: 1074: 953: 643: 873:≈ 1/137 which characterizes the magnitude of the 141:in a manner that prevents their aggregation into 137:, or quantities of dimension one, are quantities 2373: 2008: 818:can be normalized to 1 if appropriate units for 373:International Committee for Weights and Measures 161:; its value remains independent of the specific 846:, specifically regarding these five constants, 707: (= 0.001). Some angle units such as 636:to account for fractions of a full item, e.g., 477:Another consequence of the theorem is that the 371:). In another instance in the early 2000s, the 2275:National Institute of Standards and Technology 2048: 2046: 1115:. Flat spread fires such as forest fires have 500:occurring in those variables to give a set of 192:of a circle being equal to its circumference. 2099: 1962: 1477: 991:– wavenumber(spatial frequency) over distance 764:and still have physical dimension defined as 620:, can be compounded with units of frequency ( 1374: 903:. An analogous ratio can be defined for any 648:Dimensionless quantities can be obtained as 280:. In the 19th century, French mathematician 2273:Flater, David (October 2017) . Written at 2164:"How Many Fundamental Constants Are There?" 2043: 1687: 1478:Cengel, Yunus; Cimbala, John (2013-10-16). 684:, which characterizes the concentration of 430:. Unsourced material may be challenged and 215:often involve dimensionless quantities. In 1978:. Key Topics in Semantics and Pragmatics. 1929: 1769: 1639: 1592: 1349: 976: 481:dependence between a certain number (say, 2332: 2105: 1968: 1798: 1678: 1522: 1450: 699:Other common proportions are percentages 624:) to derive units of count rate, such as 450:Learn how and when to remove this message 122:Learn how and when to remove this message 2182: 1561: 1003:Dimensionless numbers in fluid mechanics 584:. The concept is formalized as quantity 2243: 1781:"Don't tamper with SI-unit consistency" 385: 375:discussed naming the unit of 1 as the " 315:(independently of French mathematician 207:, concepts like the unitless ratios in 14: 2374: 2272: 1899: 2246:"Fluid Dynamic Aspects of Room Fires" 2086:Massachusetts Institute of Technology 1775: 1403: 203:in various technical disciplines. In 2213: 2158: 1975:Semantics for Counting and Measuring 428:adding citations to reliable sources 395: 340:(dB) finds widespread use nowadays. 60:adding citations to reliable sources 31: 2052: 1244:in moving from one place to another 489:can be reduced by the number (say, 330:. Measuring logarithm of ratios as 296:. Later work by British physicists 268:Dimensional analysis § History 27:Quantity with no physical dimension 24: 2266: 1844:. 17–18 April 2003. Archived from 1227:(which is sometimes dimensionless) 25: 2393: 2353: 2309:10.1016/j.measurement.2017.05.043 1035:– (also called the mass transfer 272:Quantities having dimension one, 184:serve as dimensionless units for 176:is recognized as a dimensionless 2359: 2222:. pp. 23–25. Archived from 2013:; Koepke, Kathleen Mann (2015). 1267:List of dimensionless quantities 972:List of dimensionless quantities 954:{\textstyle {\sqrt {\hbar c/G}}} 804:universal gravitational constant 788:Dimensionless physical constants 400: 36: 2277:, Gaithersburg, Maryland, USA. 2237: 2207: 2176: 2152: 2070: 2002: 1923: 1893: 1862: 1831: 1757:from the original on 2022-12-21 1633: 1381:"Dimensionless units in the SI" 1231: 794:Dimensionless physical constant 644:Ratios, proportions, and angles 47:needs additional citations for 1586: 1555: 1541:10.1103/PhysRevLett.107.191101 1498: 1471: 1444: 1397: 1368: 1312: 1108:{\displaystyle Q^{*}\approx 1} 1055:Zukoski number, usually noted 13: 1: 1305: 1295:Orders of magnitude (numbers) 889:proton-to-electron mass ratio 660:. Another set of examples is 1611:10.1021/acs.langmuir.6b02666 1457:. Rutgers University Press. 1288:, the analogous concepts in 1200: 7: 2244:Zukoski, Edward E. (1986). 2183:Einstein, A. (2005-02-23). 1562:Einstein, A. (2005-02-23). 1260: 875:electromagnetic interaction 735:and is used to measure the 703: (= 0.01),   523: 512:independent, dimensionless 351:argued for formalizing the 10: 2398: 2130:10.1088/0026-1394/47/3/012 2078:"7.3 Dimensionless groups" 1980:Cambridge University Press 1777:Wendl, Michael Christopher 1451:Zebrowski, Ernest (1999). 1430:10.1088/0026-1394/31/6/013 1282:Normalization (statistics) 1174:{\displaystyle Q^{*}\gg 1} 1141:{\displaystyle Q^{*}<1} 1000: 969: 838:are chosen. The resulting 791: 389: 265: 261: 2220:Naval Research Laboratory 1710:(7666): 135. 2017-08-10. 1700:. This Week: Editorials. 1404:Mills, I. M. (May 1995). 1326:quantity of dimension one 1254:Basic reproduction number 559: 547: 535: 530: 145:. Typically expressed as 2382:Dimensionless quantities 2214:Huba, Joseph D. (2007). 1377:Phillips, William Daniel 725:coefficient of variation 274:dimensionless quantities 169:per milliliter (mL/mL). 135:Dimensionless quantities 71:"Dimensionless quantity" 1930:Buckingham, E. (1914). 1511:Physical Review Letters 1365:ISBN 978-92-822-2272-0. 1328:dimensionless quantity" 977:Physics and engineering 965: 899:divided by that of the 867:fine-structure constant 658:unit conversion factors 580:can be used to express 284:and Scottish physicist 229:fine-structure constant 2201:10.1002/andp.200590006 1580:10.1002/andp.200590006 1220:Standard atomic weight 1209:– density relative to 1175: 1142: 1109: 1076: 955: 692:, could be written as 668:, often written using 336:in the (derived) unit 201:differential equations 2366:Dimensionless numbers 2251:. Fire Safety Science 1956:10.1103/physrev.4.345 1671:10.1103/PhysRev.4.345 1176: 1143: 1110: 1077: 1075:{\displaystyle Q^{*}} 1009:Beta (plasma physics) 1001:Further information: 956: 217:differential geometry 2368:at Wikimedia Commons 1277:Dimensional analysis 1225:Equilibrium constant 1216:Relative atomic mass 1152: 1119: 1086: 1059: 930: 891:. This ratio is the 727:is the ratio of the 680:/mol). For example, 582:countable quantities 424:improve this section 392:Buckingham π theorem 386:Buckingham π theorem 278:dimensional analysis 256:concentration ratios 186:angular measurements 143:units of measurement 56:improve this article 2301:2017Meas..109..105F 2122:2010Metro..47..219J 1948:1914PhRv....4..345B 1716:2017Natur.548R.135. 1663:1914PhRv....4..345B 1533:2011PhRvL.107s1101W 1422:1995Metro..31..537M 1286:standardized moment 905:elementary particle 850:. However, not all 762:unitless quantities 640:equal to one half. 634:non-integer numbers 598:number of particles 596:. Examples include 367:) versus energy (a 286:James Clerk Maxwell 258:are dimensionless. 251:and ratios such as 157:(ABV) represents a 2189:Annalen der Physik 2011:Geary, David Cyril 2009:Berch, Daniel B.; 1779:(September 2017). 1680:10338.dmlcz/101743 1568:Annalen der Physik 1300:Similitude (model) 1171: 1138: 1105: 1072: 1027:Numerical aperture 951: 913:coupling strength 877:between electrons. 859:engineering strain 852:physical constants 816:Boltzmann constant 729:standard deviation 690:alcoholic beverage 670:parts-per notation 586:number of entities 531:Number of entities 139:implicitly defined 2364:Media related to 2160:Baez, John Carlos 2030:978-0-12-801909-2 1989:978-1-107-00127-5 1641:Buckingham, Edgar 1605:(35): 8969–8979. 1491:978-0-07-717359-3 1464:978-0-8135-2898-4 1406:"Unity as a Unit" 1238:Cost of transport 1015:Damköhler numbers 949: 682:alcohol by volume 571: 570: 460: 459: 452: 233:quantum mechanics 165:used, such as in 155:alcohol by volume 132: 131: 124: 106: 16:(Redirected from 2389: 2363: 2346: 2336: 2260: 2259: 2257: 2256: 2250: 2241: 2235: 2234: 2232: 2231: 2211: 2205: 2204: 2180: 2174: 2173: 2171: 2170: 2156: 2150: 2149: 2103: 2097: 2096: 2094: 2093: 2082: 2074: 2068: 2067: 2065: 2064: 2050: 2041: 2040: 2038: 2037: 2021:Elsevier Science 2006: 2000: 1999: 1997: 1996: 1970:Rothstein, Susan 1966: 1960: 1959: 1927: 1921: 1920: 1897: 1891: 1890: 1888: 1887: 1881: 1875:. Archived from 1874: 1866: 1860: 1859: 1857: 1856: 1850: 1843: 1835: 1829: 1828: 1802: 1773: 1767: 1765: 1763: 1762: 1756: 1699: 1691: 1685: 1684: 1682: 1637: 1631: 1630: 1590: 1584: 1583: 1559: 1553: 1552: 1526: 1502: 1496: 1495: 1475: 1469: 1468: 1448: 1442: 1441: 1401: 1395: 1394: 1375:Mohr, Peter J.; 1372: 1366: 1364: 1353: 1347: 1346: 1344: 1343: 1316: 1207:Relative density 1180: 1178: 1177: 1172: 1164: 1163: 1147: 1145: 1144: 1139: 1131: 1130: 1114: 1112: 1111: 1106: 1098: 1097: 1081: 1079: 1078: 1073: 1071: 1070: 960: 958: 957: 952: 950: 945: 934: 842:is known as the 812:Coulomb constant 781:moisture content 778: 759: 695: 578:counting numbers 528: 527: 520:are equivalent. 465: 455: 448: 444: 441: 435: 404: 396: 312: 306:Edgar Buckingham 298:Osborne Reynolds 249:state properties 159:volumetric ratio 153:. For instance, 127: 120: 116: 113: 107: 105: 64: 40: 32: 21: 2397: 2396: 2392: 2391: 2390: 2388: 2387: 2386: 2372: 2371: 2356: 2345:. NIHMS1633436. 2269: 2267:Further reading 2264: 2263: 2254: 2252: 2248: 2242: 2238: 2229: 2227: 2212: 2208: 2195:(S1): 194–224. 2181: 2177: 2168: 2166: 2157: 2153: 2104: 2100: 2091: 2089: 2080: 2076: 2075: 2071: 2062: 2060: 2051: 2044: 2035: 2033: 2031: 2007: 2003: 1994: 1992: 1990: 1982:. p. 206. 1967: 1963: 1936:Physical Review 1928: 1924: 1898: 1894: 1885: 1883: 1879: 1872: 1868: 1867: 1863: 1854: 1852: 1848: 1841: 1837: 1836: 1832: 1800:10.1038/549160d 1774: 1770: 1760: 1758: 1754: 1724:10.1038/548135b 1697: 1693: 1692: 1688: 1650:Physical Review 1638: 1634: 1591: 1587: 1574:(S1): 194–224. 1560: 1556: 1503: 1499: 1492: 1484:. 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London, UK: 2268: 2265: 2262: 2261: 2236: 2206: 2175: 2162:(2011-04-22). 2151: 2116:(3): 219–230. 2098: 2069: 2042: 2029: 2023:. p. 13. 2001: 1988: 1961: 1942:(4): 345–376. 1922: 1911:(117): 1–210. 1892: 1861: 1830: 1768: 1686: 1657:(4): 345–376. 1632: 1585: 1554: 1517:(19): 191101. 1497: 1490: 1470: 1463: 1443: 1416:(6): 537–541. 1396: 1379:(2015-06-01). 1367: 1348: 1310: 1309: 1307: 1304: 1303: 1302: 1297: 1292: 1279: 1274: 1272:Arbitrary unit 1269: 1262: 1259: 1258: 1257: 1251: 1245: 1233: 1230: 1229: 1228: 1222: 1213: 1202: 1199: 1198: 1197: 1195:Grashof number 1192: 1187: 1182: 1170: 1167: 1162: 1158: 1137: 1134: 1129: 1125: 1104: 1101: 1096: 1092: 1069: 1065: 1053: 1046: 1043:Schmidt number 1040: 1037:Nusselt number 1030: 1024: 1021:Thiele modulus 1018: 1012: 999: 998: 992: 989:Fresnel number 986: 983:Lorentz Factor 978: 975: 970:Main article: 967: 964: 963: 962: 948: 944: 940: 937: 921: 917: 908: 887:) ≈ 1836, the 878: 863: 862: 800:speed of light 792:Main article: 789: 786: 666:mole fractions 662:mass fractions 645: 642: 622:inverse second 569: 568: 563: 557: 556: 551: 545: 544: 539: 537:Common symbols 536: 533: 532: 525: 522: 458: 457: 408: 406: 399: 390:Main article: 387: 384: 369:scalar product 365:vector product 282:Joseph Fourier 263: 260: 253:mole fractions 237:Lorentz factor 225:fluid dynamics 130: 129: 44: 42: 35: 26: 9: 6: 4: 3: 2: 2394: 2383: 2380: 2379: 2377: 2367: 2362: 2358: 2357: 2348: 2344: 2340: 2335: 2330: 2326: 2322: 2318: 2314: 2310: 2306: 2302: 2298: 2294: 2293:Elsevier Ltd. 2290: 2286: 2285: 2280: 2276: 2271: 2270: 2247: 2240: 2226:on 2021-04-27 2225: 2221: 2217: 2210: 2202: 2198: 2194: 2190: 2186: 2179: 2165: 2161: 2155: 2147: 2143: 2139: 2135: 2131: 2127: 2123: 2119: 2115: 2111: 2110: 2102: 2088: 2087: 2079: 2073: 2059: 2055: 2049: 2047: 2032: 2026: 2022: 2018: 2017: 2012: 2005: 1991: 1985: 1981: 1977: 1976: 1971: 1965: 1957: 1953: 1949: 1945: 1941: 1937: 1933: 1926: 1918: 1914: 1910: 1906: 1902: 1896: 1882:on 2006-11-30 1878: 1871: 1865: 1851:on 2006-11-30 1847: 1840: 1834: 1826: 1822: 1818: 1814: 1810: 1806: 1801: 1796: 1793:(7671): 160. 1792: 1788: 1787: 1782: 1778: 1772: 1753: 1749: 1745: 1741: 1737: 1733: 1729: 1725: 1721: 1717: 1713: 1709: 1705: 1704: 1696: 1690: 1681: 1676: 1672: 1668: 1664: 1660: 1656: 1652: 1651: 1646: 1642: 1636: 1628: 1624: 1620: 1616: 1612: 1608: 1604: 1600: 1596: 1589: 1581: 1577: 1573: 1569: 1565: 1558: 1550: 1546: 1542: 1538: 1534: 1530: 1525: 1520: 1516: 1512: 1508: 1501: 1493: 1487: 1483: 1482: 1474: 1466: 1460: 1456: 1455: 1447: 1439: 1435: 1431: 1427: 1423: 1419: 1415: 1411: 1407: 1400: 1392: 1388: 1387: 1382: 1378: 1371: 1362: 1358: 1352: 1337: 1333: 1329: 1327: 1323: 1315: 1311: 1301: 1298: 1296: 1293: 1291: 1287: 1283: 1280: 1278: 1275: 1273: 1270: 1268: 1265: 1264: 1255: 1252: 1249: 1246: 1243: 1239: 1236: 1235: 1226: 1223: 1221: 1217: 1214: 1212: 1208: 1205: 1204: 1196: 1193: 1191: 1188: 1186: 1185:Eckert number 1183: 1168: 1165: 1160: 1156: 1135: 1132: 1127: 1123: 1102: 1099: 1094: 1090: 1067: 1063: 1054: 1050: 1047: 1044: 1041: 1038: 1034: 1031: 1028: 1025: 1022: 1019: 1016: 1013: 1010: 1007: 1006: 1004: 996: 993: 990: 987: 984: 981: 980: 973: 946: 942: 938: 935: 925: 922: 916: 912: 909: 906: 902: 898: 894: 890: 886: 882: 879: 876: 872: 868: 865: 864: 860: 857: 856: 855: 853: 849: 845: 844:natural units 841: 837: 833: 829: 825: 821: 817: 813: 809: 805: 801: 795: 785: 782: 777: 773: 769: 763: 758: 754: 750: 744: 742: 738: 734: 730: 726: 722: 718: 714: 710: 706: 702: 697: 691: 687: 683: 679: 675: 671: 667: 663: 659: 655: 651: 641: 639: 635: 631: 627: 623: 619: 615: 614: 609: 608: 603: 599: 595: 591: 587: 583: 579: 575: 567: 564: 562: 558: 555: 552: 550: 546: 543: 540: 534: 529: 521: 519: 515: 511: 507: 503: 499: 496: 492: 488: 484: 480: 475: 473: 469: 454: 451: 443: 433: 429: 425: 419: 418: 414: 409:This section 407: 403: 398: 397: 393: 383: 380: 378: 374: 370: 366: 362: 358: 354: 350: 346: 341: 339: 335: 334: 329: 328:heat transfer 325: 320: 318: 314: 307: 303: 302:Lord Rayleigh 299: 295: 291: 287: 283: 279: 275: 269: 259: 257: 254: 250: 246: 242: 238: 234: 230: 226: 222: 218: 214: 210: 206: 202: 198: 193: 191: 187: 183: 179: 178:base quantity 175: 170: 168: 164: 160: 156: 152: 148: 144: 140: 136: 126: 123: 115: 104: 101: 97: 94: 90: 87: 83: 80: 76: 73: –  72: 68: 67:Find sources: 61: 57: 51: 50: 45:This article 43: 39: 34: 33: 30: 19: 18:Dimensionless 2288: 2282: 2253:. 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