in fluid mechanics and heat transfer* Name Definition Ratio of Significance Gravitational force Archimedes number P, - P) Viscous force L. AR = Length L. Length Aspect ratio or Width Diameter hl. Internal thermal resistance Biot number Surface thermal resistance Gravitational force Bond number Bo = Surface tension farce P- P, Pressure - Vapor pressure Cavitation number Ca (sometimes o)- Inertial pressure 2(P - РЭ Sometimes 87, Wall friction force Darcy friction factor Inertial force Fo Drag force Drag coefficient devA Dynamic force Kinetic energy Eckert number Enthalpy AP sometimes AP Pressure difference Euler number Eu = Dynamic preнsre 2r. G= Wall friction force Fanning frietion factor Incrtial force Physical time at Fo (sometimes t) - Fourier number Thermal diffusion time Inertial force Froude number Sometimes Gravitational force Gr = ATIL' Висуancy force Grashof number Viscous force G,(T - T) Ja = Sensible energy Jakob number Latent energy Mean free path length Characteristic length Knudsen number Kn = Thermal diffusion Lewis number Le = pe,Da Das Species diffusion F. Lift force Lift coefficient Dynamic force (continued) Name Definition Ratio of Significance Flow speed Speed of sound Mach number Ma (sometimes M) Convection heat transfer Nusselt number Nu= Conduction heat transfer pL.Vc, LV Bulk heat transfer Peclet number Conduction heat transfer Power Power number N.- pD'a Rotational inertia Viscous diffusion Prandtl number Thermal diffusion Static pressure difference Pressure coefficient Dynamic pressure RPIATEc, Висуancy force Viscous force Rayleigh numbeer ku pVL VI. Inertial force Reynelds number Re = Viscous force Висуаnсy foree Richardson number Ri = Inertial force Viscous diffusion Schmidt number Se DAn Species diffusion VI. Overall mass diffusion Sherwood number Species diffusion Enthalpy Internal energy Specifie heat ratio k (sometimes y) = Convection heat transfer Stanton number St = pr,V Thermal capacity Stk (sometimes St) = 18ul. Particle relaxation time Characteristic flow time Stokes number Characteristic flow time St (scmetimes Sor Sr) =4 Strouhal number Period of oscillation pVI. Inertial force Weber number We Surface tension force *Ais a characteristic ares, Disa caracteristic diameter, fisa characteristic froquency (Hz, Lisa characteristic length, risa characteristic time, Tisa characteristic (absotute) temperature, Visa daracteristic velocity, Wis a characteristic with Weecharacteristie nower ais a charatoristie anenter welovity drsd Other arametor end uidemneeties in