1 special topics
1.1 compressibility
1.2 reynolds number
1.3 viscosity
1.4 turbulence
1.5 boundary layer
1.6 maximum entropy principle
1.7 thermodynamic equilibrium
special topics
compressibility
compressibility factors air.
thermodynamicists use factor (z) alter ideal gas equation account compressibility effects of real gases. factor represents ratio of actual ideal specific volumes. referred fudge-factor or correction expand useful range of ideal gas law design purposes. z value close unity. compressibility factor image illustrates how z varies on range of cold temperatures.
reynolds number
in fluid mechanics, reynolds number ratio of inertial forces (vsρ) viscous forces (μ/l). 1 of important dimensionless numbers in fluid dynamics , used, along other dimensionless numbers, provide criterion determining dynamic similitude. such, reynolds number provides link between modeling results (design) , full-scale actual conditions. can used characterize flow.
viscosity
satellite view of weather pattern in vicinity of robinson crusoe islands on 15 september 1999, shows unique turbulent cloud pattern called kármán vortex street
viscosity, physical property, measure of how adjacent molecules stick 1 another. solid can withstand shearing force due strength of these sticky intermolecular forces. fluid continuously deform when subjected similar load. while gas has lower value of viscosity liquid, still observable property. if gases had no viscosity, not stick surface of wing , form boundary layer. study of delta wing in schlieren image reveals gas particles stick 1 (see boundary layer section).
turbulence
delta wing in wind tunnel. shadows form indices of refraction change within gas compresses on leading edge of wing.
in fluid dynamics, turbulence or turbulent flow flow regime characterized chaotic, stochastic property changes. includes low momentum diffusion, high momentum convection, , rapid variation of pressure , velocity in space , time. satellite view of weather around robinson crusoe islands illustrates 1 example.
boundary layer
particles will, in effect, stick surface of object moving through it. layer of particles called boundary layer. @ surface of object, static due friction of surface. object, boundary layer new shape of object rest of molecules see object approaches. boundary layer can separate surface, creating new surface , changing flow path. classical example of stalling airfoil. delta wing image shows boundary layer thickening gas flows right left along leading edge.
maximum entropy principle
as total number of degrees of freedom approaches infinity, system found in macrostate corresponds highest multiplicity. in order illustrate principle, observe skin temperature of frozen metal bar. using thermal image of skin temperature, note temperature distribution on surface. initial observation of temperature represents microstate . @ future time, second observation of skin temperature produces second microstate. continuing observation process, possible produce series of microstates illustrate thermal history of bar s surface. characterization of historical series of microstates possible choosing macrostate classifies them single grouping.
thermodynamic equilibrium
when energy transfer ceases system, condition referred thermodynamic equilibrium. condition implies system , surroundings @ same temperature heat no longer transfers between them. implies external forces balanced (volume not change), , chemical reactions within system complete. timeline varies these events depending on system in question. container of ice allowed melt @ room temperature takes hours, while in semiconductors heat transfer occurs in device transition on off state on order of few nanoseconds.
Comments
Post a Comment