1、Letter symbols for physical quantities Symbols for use in fluid mechanics Formelzeichen; Formelzeichen fr die Strmungsmechanik. DIN 7 1304 Part 5 Supersedes DIN 5492, November 1965 edition. Contents Page Page 1 Scope and field of application . 1 2.5 Subscripts and superscripts 4 2 Tables 1 2.1 Geome
2、trical parameters 1 Standards referred to 5 2.2 Fluid kinematics . 1 Other relevant standards 5 2.3 Fluid dynamics 2 Previous edition . 5 2.4 Coefficients, ratios and characteristic numbers . 3 Amendments . 5 1 In conjunction with DIN 1304 Part 1, this standard specifies letter symbols for quantitie
3、s specific to fluid mechanics. Letter symbols specified in DIN 1304 Part 1 have been included here only as far as their meaning differs or has been restricted. Scope and field of application 2 Tables See clause 3 of DIN 1301 Part 1, March 1994 edition, for rules of using letter symbols. 2.1 Geometri
4、cal parameters Table 1 No. Symbol Quantity 1.1 T, q, z cylindrical coordinates 1.2 d, hydraulic diameter, equivalent diameter 1.3 k hydraulic roughness SI unit m, rad, m m m unit vector in the direction of the normal to the surface 1 2.2 Fluid kinematics Table 2 I No. I Symbol I Quantity 2.1 v flow
5、velocity 2.2 u, v, w Cartesian coordinates of flow velocity 2.3 5 mean flow velocity 2.4 V turbulent main flow velocity passed and U is the wetted perimeter. Particle diameter of the associated sand roughness standard. I For a closed surface: in the direction of the exterior normal to the surface. S
6、I unit Remarks mfs mis I m/s I Mean value over time or area. m/s I (continued) Continued on pages 2 to 5. luth Verlag GmbH. Berlin, has the exclusive right of sale for German Standards(D1N-Normen). DIN 1304 Part 5 Engl. Price group 7 05.95 Sales No. O1 07 Page 2 DIN 1304 Part 5 SI unit Remarks No. I
7、 Symbol 1 Quantity 2.5 2.6 2.7 2.8 2.9 m/s I v fluctuation in turbulent flow ve- locity v, Laval velocity Y,D shear rate 0 vorticity vector D rate of deformation tensor m/s S- Local rate of fluid flow the magnitude of which is equal to the local speed of sound. Cf. DIN 1342 Part 2. S-1 10 = (rot v)/
8、2 (rot = rotation of u) 2.11 S-1 52 rotation tensor D = (grad v + (grad v)T)/2 T means transposed; cf. DIN 1303, No. 4.7. 2.16 2.17 2.10 I D, I coordinates of D r circulation qv,V volume flow rate S-1 m2/s m3/s D is symmetrical: Dg = Di, where i, j = 1, ., 3. R = (grad v - (grad )/2 r = fv. ds, wher
9、e ds is the line element around the closed curve C. qv = a dA, where qv is the volume per unit time cross- ing the cross-sectional area, A, in the direction of the nor- mal to the surface, n. C A S-1 - No. 3.1 - - 3.2 - 3.3 3.4 - - 3.5 3.6 3.7 - - - 3.8 Symbol FA Quantity SI unit Remarks buoyancy fo
10、rce N Static force equal to the weight of the fluid displaced by an object and acting in the vertical opposite to gravity. pressure gradient in the main flow direction Pa/m Sij coordinates of S s stress vector N/m2 S- R is antisymmetrical: sZij = - Qji, where i, j = 1, ., 3. components of Q, coordin
11、ates mz/S IFor rot v = O, v can be expressed as grad 4j. velocity potential stream function (for laminar m2/s For div v= O, the cartesian coordinates of v can be ex- pressed as u = away, v = - aY/ax, and w = o (div v = divergence of v). I I 2.15 I g 1 is the characteristic length; Ap is the differen
12、tial pressure; v is the characteristic speed; Y is the kinematic viscosity; u surface tension. U is the acceleration due to gravity; 4.1 1 Sr Il Strouhal number 4.12 We 2.5 Subscripts and superscripts Table 5 No. 5.1 - - 5.2 - 5.3 5.4 5.5 - - Quantity Example po eo p., ambient pressure v, free strea
13、m speed Re* critical Reynolds number pressure in air at rest. air density at ground level. Symbol O m *, crit A D state of rest reference value far from a wall or an obstacle undisturbed state for free stream quantities critical bu o y an cy PA buoyancy force vD diffusion velocity qD viscosity in ex
14、tension diffusion extension 5.6 fl fluid pfl fluid density 5.7 id ideal (frictionless) Apid symbols for general use DIN 1342 Pari 2 Viscosity of Newtonian fluids DIN 4895 Part 1 Orthogonal coordinate systems: general concepts IS0 31-12: 1992 Quantities and units. Part 12: Characteristic numbers Othe
15、r relevant standards DIN 1304 Part2 Letter symbols for physical quantities; symbols for use in meteorology and geophysics DIN 1304 Part 3 Letter symbols for physical quantities; symbols for use in electric power engineering DIN 1304 Part 4 (at present at the stage of draft) Letter symbols for physic
16、al quantities: symbols for use in acoustics DIN 1304 Pari 7 Letter symbols for physical quantities; symbols for electrical machinery Previous edition DIN 5492: 11.65. Amendments The following amendments have been made to DIN 5492, November 1965 edition. a) The standard number has been changed (now, DIN 1304 Part 5). b) All letter symbols now specified in DIN 1304 Part 1 have been omitted. c) The standard has been completely revised. international Patent Classification GO1 1/00 G O1 V 1/00
