A B C D
DALL TUBE DALTON'S LAW DALTON'S LAW OF PARTIAL PRESSURES DAMAGE INTERFACE DAMPING, OF HEAT EXCHANGER TUBES DARCY EQUATION DARCY FREE CONVECTION DARCY NUMBER DARCY'S LAW DARCY-PRANDTL NUMBER Data for molecules of practical interest DATING OF ARCHAEOLOGICAL SAMPLES DDT, DEFLAGRATION TO DETONATION TRANSITION DE LAVAL NOZZLES DE-ICING DEBORAH NUMBER DEBYE TEMPERATURE DECANTATION DECANTERS DECELERATING DROPS DECONVOLUTION, OPTICS DEEP SHAFT DEFINITE INTEGRALS DEFLAGRATION DEFLAGRATION TO DETONATION TRANSITION, DDT DEGENERACY DEGREES OF FREEDOM DEHYDRATION DELIQUESCENCE DELTA FUNCTION DENDRITE LAYER DENDRITIC CRYSTALS DENSITY GAS MODEL DENSITY MAXIMUM OF WATER DENSITY MEASUREMENT DENSITY OF GASES DENSITY OF LIQUIDS DENSITY, HOMOGENEOUS DENSITY, OF THE ATMOSPHERE DENSITY-WAVE OSCILLATIONS DEPARTMENT OF THE ENVIRONMENT, DoE DEPARTURE FROM FILM BOILING DEPARTURE FROM NUCLEATE BOILING, DNB DEPHLEGMATOR DEPOSITION DEPOSITION OF HOMO- AND HETERO-EPITAXIAL SILICON THICK FILMS BY MESO-PLASMA CVD DEPOSITION OF PARTICLES DEPOSITION RATE OF DROPLETS IN ANNULAR FLOW DERIAZ TURBINES Derivative (derived) unit of measurement DESALINATION DESALINATION OF OIL DESALINATION, FLASH EVAPORATION FOR DESICCANTS DESICCATION DESIGN BASIS ACCIDENT DESTRUCTION OF SURFACES DETECTION OF CHEMICAL AND BIOLOGICAL AEROSOLIZED POLLUTANTS DETERGENTS DETERMINANTS Determination of material properties: optical tomography applications DETERMINISTIC CHAOS DETONATION DETONATION WAVE DEUTERIUM DEUTERIUM OXIDE DEUTSCH-ANDERSON EQUATION DEVIATORIC STRESS DEVOLATIZATION OF COAL PARTICLES DEW POINT DEWAR DEWATERING DIAMETER, HYDRAULIC DIAMOND-SHAPED CYLINDER BUNDLE DIAPHRAGM GAUGE DIE DIE-CASTING DIELECTRIC HEATING DIELECTROPHORETIC FORCES DIESEL CONDITIONS DIESEL ENGINES DIESEL FUEL DIESEL JET DESTRUCTION DIESEL SPRAY DIESEL-EMITTED PARTICLES Differential approximations DIFFERENTIAL CONDENSATION CURVE DIFFERENTIAL EQUATIONS DIFFERENTIAL PRESSURE FLOWMETERS DIFFERENTIAL PRESSURE TRANSDUCERS DIFFRACTION DIFFUSER DIFFUSION DIFFUSION APPROXIMATION IN MULTIDIMENSIONAL RADIATIVE TRANSFER PROBLEMS DIFFUSION COEFFICIENT DIFFUSION COEFFICIENT OF GASES DIFFUSION EQUATIONS DIFFUSION FLAMES DIFFUSION IN ELECTROLYTE SOLUTION DIFFUSION LAW DIFFUSION PUMP DIFFUSIVE CONVECTION DILATANCY DILATANT FLUIDS DILATION OF GRANULAR MATERIAL DILUTANT FLUIDS DILUTE SUSPENSION Dimension (of a secondary quantity with respect to a given primary quantity) Dimensional Analysis Dimensional Analysis and Similarity Dimensional equation DIMENSIONAL MATRIX Dimensional quantity (variable) DIMENSIONAL STABLE ANODES, DSAS DIMENSIONALLY HOMOGENEOUS EQUATIONS DIMENSIONLESS GROUPS Dimensionless Parameters Dimensionless quantity (Dimensionless variable) DIMERS DIOXINS DIPHENYL DIPOLE MOMENT DIRAC DELTA FUNCTION DIRECT CONTACT CONDENSERS DIRECT CONTACT EVAPORATORS DIRECT CONTACT HEAT EXCHANGERS DIRECT CONTACT HEAT TRANSFER DIRECT CONTACT MASS TRANSFER DIRECT INVERSION OPTICAL TECHNIQUE DIRECT NUMERICAL SIMULATIONS, DNS DIRICHLET CONDITIONS DIRICHLET'S PROBLEM DISCHARGE COEFFICIENT DISCRETE ENERGY DISCRETE ORDINATE APPROXIMATION Discrete ordinates and finite volume methods Discrete ordinates method Discrete ordinates method for one-dimensional problems DISK AND DOUGHNUT BAFFLES DISK TYPE CENTRIFUGE DISK TYPE STEAM TURBINE DISORDER Dispersed Flow DISPERSED FLOW, IN NOZZLES DISPERSED LIQUID FLOWS DISPERSION IN POROUS MEDIA DISPERSION OF PARTICLES DISPERSION RELATIONSHIPS, FOR WAVES IN FLUIDS DISPLACEMENT CHROMATOGRAPHY Displacement thickness DISPLACEMENT THICKNESS, OF BOUNDARY LAYER DISSIPATION OF HEAT FROM EARTH'S SURFACE DISSIPATIVE SYSTEMS DISSOLVED AIR FLOTATION, DAF DISSOLVED SOLIDS DISTILLATION DISTILLATION REBOILERS DISTRIBUTIONS DISTURBANCE WAVES, IN ANNULAR FLOW DISYMMETRY OF SCATTERED LIGHT DITTUS-BOELTER CORRELATION DITTUS-BOELTER EQUATION DNB, DEPARTURE FROM NUCLEATE BOILING DOE DOLINSKII, A.A. DOMESTIC WATER HEATER DONNEN EFFECT DOPING DOPPLER ANEMOMETRY DOPPLER BROADENING DOPPLER BURST DOPPLER EFFECT DOPPLER GLOBAL VELOCIMETRY DOPPLER SHIFT DOUBLE DIFFUSIVE CONVECTION IN A ROTATING POROUS LAYER DOUBLE EXPOSURE HOLOGRAPHY DOUBLE FLASH METHODS DOUBLE-DIFFUSIVE MAGNETOCONVECTION DOUBLE-PIPE EXCHANGERS DOUBLING TIME DOUBLY STRATIFIED DARCY POROUS MEDIUM DOWTHERM DRAFT TUBE MIXER DRAG Drag Coefficient DRAG FORCE DRAG FORCE ON PARTICLES DRAG INDUCED FLOW DRAG ON A PARTICLE DRAG ON PARTICLES AND SPHERES DRAG ON REACTOR DRAG ON SOLID SPHERES AND BUBBLES DRAG REDUCTION DRAINING INTENSELY EVAPORATED WAVE FILMS DREITSER, G.A. DRIFT FLUX Drift flux models DRIFT VELOCITY DROP FORMATION DROP SHAPES DROP SPLITTING DROP TOWERS DROPLET COLLISION DROPLET DEPOSITION AND ENTRAINMENT, IN ANNULAR FLOW DROPLET DETECTION DROPLET GENERATION DROPLET MEASUREMENTS DROPLET SIZE DISTRIBUTION DROPLET SPRAYS DROPLET STREAM DROPLET SURFACE TENSION DROPLET/LIQUID SEPARATION DROPLETS Drops DROPS, MASS TRANSFER TO AND FROM Dropsize measurement DROPWISE CONDENSATION DROPWISE PROMOTERS DROWNING OUT DRUM TYPE STEAM TURBINE DRY CONTAINMENTS, FOR NUCLEAR REACTORS DRY-BULB TEMPERATURE DRYERS DRYING DRYING CHAMBERS DRYOUT DUAL-PURPOSE HEAT PUMPS DUBOIS' BODY SURFACE DUCTILE FRACTURE DUCTS, NONCIRCULAR, FLOW IN DUFOUR EFFECT DUNE FLOW DUST, AS AN AIR POLLUTANT DUSTS DUSTY PLASMAS DWARF GALAXIES DYE LASERS DYNAMIC INSTABILITIES IN TWO-PHASE SYSTEMS Dynamic Pressure DYNAMIC WAVES DYNAMICAL SIMILARITY DYNAMICS
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DIMENSIONLESS GROUPS

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A dimensionless group is a combination of dimensional or dimensionless quantities having zero overall dimension. In a system of coherent units, it can therefore be represented by a pure number.

The value of dimensionless groups for generalizing experiemental data has been long recognized. Over a hundred years ago, G. G. Stokes demonstrated the importance of the group now known as Reynolds Number as a criterion for similarity of fluid behavior under different conditions [Stokes, (1966)]. It was Helmholtz who showed the significance of the groups now known as Froude Number and Mach Number. Initially, the dimensionless groups did not have specific names, and the first to attach names was M. G. Weber in 1919, when he allocated the titles Froude, Reynolds and Cauchy to groups.

The naming of numbers is an informal process, and there are several cases where the same dimensionless group has been given more than one name, e.g., Froude and Boussinesq, Bond and Eötvös. On the other hand, some savants have been honored by a multiplicity of numbers; Lagrange for instance has three, and Damköhler, no less than five. There does however seem to be one law which, though unwritten, is broken only rarely; that is, that dimensionless titles are awarded posthumously.

The following table lists the dimensionless groups most relevant to heat and mass transfer.

Table 1. Dimensionless groups

REFERENCES

Catchpole, J. P. and Fulford, D., Dimensionless Groups, Ind. Eng. Chem. 58(3):46, 1966 and 60(3):71 (1968).

Stokes, G. G. (1966) Mathematical and Physical Papers 2nd ed, vol. 3.

References

  1. Catchpole, J. P. and Fulford, D., Dimensionless Groups, Ind. Eng. Chem. 58(3):46, 1966 and 60(3):71 (1968).
  2. Stokes, G. G. (1966) Mathematical and Physical Papers 2nd ed, vol. 3.

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