CAVITATION AND BUBBLE DYNAMICS
OXYGEN WATER SODIUM TOLUENE ETHANE FREON – NITROGEN METHANE HYDROGEN MERCURY HELIUM – FIGURE 1 2 RATIO OF SATURATED LIQUID DENSITY TO SATURATED VAPOR DENSITY AS A FUNCTION OF TEMPERATURE FOR VARIOUS PURE SUBSTANCES WITHIN THE CRYSTAL LATTICE DUE TO THE THERMAL AGITATION THIS KIND OF CREEP, WHICH IS KNOWN AS DIFFUSION CREEP, IS ANALOGOUS TO THE ?UIDITY OBSERVED IN MOST LIQUIDS AND CAN BE CHARACTERIZED BY A SIMPLE NEWTONIAN VISCOSITY FOLLOWING THIS WE MAY ASK WHETHER THE LIQUID STATE POSSESSES AN ELASTICITY EVEN THOUGH SUCH ELASTICITY MAY BE DOMINATED BY THE ?UIDITY OF THE LIQUID IN MANY PHYSI- CAL PROCESSES IN BOTH THE LIQUID AND SOLID STATES ONE MIGHT ENVISAGE A CERTAIN TYPICAL TIME, TM, FOR THE MIGRATION OF A MOLECULE FROM ONE POSITION WITHIN THE STRUCTURE OF THE SUBSTANCE TO A NEIGHBORING POSITION; ALTERNATIVELY ONE MIGHT CONSIDER THIS TYPI- CAL TIME AS CHARACTERIZING THE MIGRATION OF A “HOLE” OR VACANCY FROM ONE POSITION TO ANOTHER WITHIN THE STRUCTURE THEN IF THE TYPICAL TIME, T, ASSOCIATED WITH THE APPLIED FORCE IS SMALL COMPARED WITH TM, THE SUBSTANCE WILL NOT BE CAPABLE OF PERMANENT DEFORMATION DURING THAT PROCESS AND WILL EXHIBIT ELASTICITY RATHER THAN ?UIDITY ON THE OTHER HAND IF T ?TM THE MATERIAL WILL EXHIBIT ?UIDITY THUS, THOUGH THE CON- CLUSION IS OVERLY SIMPLISTIC, ONE CAN CHARACTERIZE A SOLID AS HAVING A LARGE TM AND A LIQUID AS HAVING A SMALL TM RELATIVE TO THE ORDER OF MAGNITUDE OF THE TYPICAL TIME, T, OF THE APPLIED FORCE ONE EXAMPLE OF THIS IS THAT THE EARTH’S MANTLE BEHAVES TO ALL CAVITATION AND BUBBLE DYNAMICS