iii
				TABLE OF CONTENTS
Chapter 									Page
	LIST OF FIGURES 							xi
	LIST OF TABLES     							xvii
I. 	SUMMARY  								1
II. 	INTRODUCTION	    							7
III. 	REVIEW OF THE LITERATURE 						10
	A.  STATIC ENCOUNTERS     						10
		Gas-liquid Systems 						10
		Liquid-liquid Systems 						20
	B.  DYNAMIC ENCOUNTERS    						25
		Liquid-liquid Systems 						25
		Theory for drop collisions in gas-liquid Systems  		28
		Experiments with clouds of droplets 				42
		Studies of drops impacting on flat surfaces 			50
	    EXPERIMENTS WITH PAIRS OF DROPS COLLIDING IN
	    GASEOUS MEDIA 							59
		Qualitative studies 						59
		Studies which took impact angle into account 			77
		Studies in which impact angle was measured 			89
	C.  METHODS OF UNIFORM DROP GENERATION          			111
	D.  TECHNIQUES OF DROP PHOTOGRAPHY 					112
IV. 	OBJECTIVES OF THE INVESTIGATION 					114
V. 	PRELIMINARY EXPERIMENTS 						117
	A.  DEVELOPMENT OF DROP COLLISION CONTROL				117
		Drop generation system 						117
										iv
		Control of gas and water temperatures 				120
		Control of charges on the drops    				121
		Calibrations 							123
	B.  EARLY DROP COLLISION WORK    					125
		Attempts to produce rebound 					125
		Tests on the influence of relative humidity . 			130
		Tests on the influence of drop charge 				131
		Investigation of sunderance 					131
	C.  DEVELOPMENT OF PHOTOGRAPHIC TECHNIQUE				135
		Still photographs 						135
		Motion pictures							138
VI. 	DESCRIPTION OF THE APPARATUS    					143
	A.  EQUIPMENT USED 							143
		Chamber for control of ambient conditions 			143
		Drop generators 						146
		Systems of mechanical support 					152
		General 							154
	B.  PERFORMANCE CHARACTERISTICS          				158
		Uniform generation of drops 					158
		Range of drop sizes 						168
		Range of relative velocities 					168
		Control of other factors    					170
VII. 	EXPERIMENTAL PROCEDURE  	      					171
	A.  CONTROL OF COLLISION CONDITIONS       				171
		Drop liquid 							171
										v
		Drop size 							172
		Relative velocity 						173
		Impact angle 							175
		Charges on the drops 						177
		Water and gas temperatures 					180
		Chamber atmosphere 						182
	B.  PHOTOGRAPHY 							182
		Motion pictures        						183
		Still photographs 						186
	C.  SAMPLE RUN        							187
		Promotion of collisions at the desired conditions		188
		Motion pictures	         					191
		Collision-control data readings					193
		Still photographs 						196
		Additional series of still photographs 				198
		Results 							199
	D.  ANALYSIS OF THE DATA 						202
		Data from the motion pictures 					202
		Data from the still photographs    				209
		Other data 							212
VIII. 	EXPERIMENTAL RESULTS    						214
	A.  TERMS AND SYMBOLS     						214
		Collision 							215
		Rebound 							215
		Coalescence 							215
										vi
		Partial coalescence 						216
		Disruption 							216
		Reflex disjection 						216
		Spatter  							216
		Delay time 							217
		Relative velocity and impact angle 				217
		Mapping symbols and practices 					218
	B.  LARGE DROPS OF 1:1 DIAMETER RATIO    				219
		Collision results by runs					219
		Delay times 							224
		Illustrative composite photographs 				224
	C.  SMALL DROPS OF 1:1 DIAMETER RATIO    				244
		Collision results by runs 					244
		Delay times 							246
		Illustrative composite photographs 				247
	D.  LARGE DROPS OF 2:1 DIAMETER RATIO    				266
		Collision results by runs  					266
		Delay times 							273
		Illustrative composite photographs 				273
	E.  SMALL DROPS OF 2:1 DIAMETER RATIO    				290
		Collision results by runs					290
		Delay times 							292
		Illustrative composite photographs 				293
	F.  LARGE DROPS OF 3:1 DIAMETER RATIO    				305
		Collision results by runs					305
										vii
		Delay times 							310
		Illustrative composite photographs 				311
	C.  SMALL DROPS OF 3:1 DIAMETER RATIO    				325
		Collision results by runs					325
		Delay times 							327
		Illustrative composite photographs 				328
	H.  DROPS OF OTHER SIZES 						336
		Rebound between drops of 3:2 diameter ratio			336
		Attempted illustrative films of partial coalescence		339
		Illustrative photographs of spatter 				342
		Impacts between drops and flat surfaces  			345
IX. 	DISCUSSION OF RESULTS      						360
	A. THE POSSIBLE COLLISION OUTCOMES      				360
	B.  INFLUENCE OF MINOR FACTORS ON COLLISION OUTCOMES        		363
		Relative humidity and electrical fields or charges		364
		Physical properties 						365
		Dissolved gas and impurities 					368
		Effects on mapping 						369
	C.  EXPERIMENTAL ERROR     						370
		Drop diameters and diameter ratio 				370
		Relative velocity 						373
		Impact angle 							375
		Damping of drop oscillations 					379
		Charges carried by the drops 					380
		Water conductivity 						382
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		Temperatures 							383
		Particles in the water and gas 					385
		Relative humidity 						385
		Pressure 							387
		Gaps in the data 						388
	D.  DISCUSSION OF EXPERIMENTAL RESULTS           			390
		Positioning of boundary curves 					390
		Correlation of the data						391
		Convetitions adopted for the combined mapping of outcomes 	393
		Results of mapping at Wes > 5 					394
		Results of mapping at Wes < 5 					398
		Influence of drop size 						400
		Influence of drop diameter ratio				402
		Delay times 							406
		Aerodynamic conditions of collision 				413
	E.  COMPARISON WITH QUANTITATIVE RESULTS OF OTHER
	     EXPERIMENTERS 							419
		Plotting of data collected from the literature 			419
		The collected results 						423
		Studies utilizing a supported drop 				426
		Studies in which pairs of drops collided in free flight		435
	F.  POSSIBLE APPROACHES TO THE THEORETICAL PREDICTION OF
	     BRIDGING 								452
		Intervening gas film 						453
		Flat-plate models for film thinning 				455
										ix
		Damon's model 							459
		Surface microphysics 						463
		Bridging-stage ratios 						465
		Impact-induced oscillations 					468
	G.  SUNDERANCE THEORY     						472
		Partial coalescence 						472
		Theoretical treatments of disjection 				478
		Model for the coalescence-disruption transition			490
	H.  IMPLICATIONS OF RESULTS      					506
X.  	CONCLUSIONS       							517
XI. 	RECOMMENDATIONS FOR FUTURE RESEARCH ON DROP COLLISION
	BEHAVIOR 								522
	A.  FURTHER MAPPING OF OUTCOMES          				522
		Variation of relative velocity and impact angle			522
	            Variation of drop size and diameter ratio			524
	B.  SIMILAR INVESTIGATIONS YIELDING INFORMATION IN OTHER
	     AREAS 								525
		Influence of minor factors 					526
		Other liquids 							528
		Delay times 							528
		Post-bridging data 						529
	C.  OTHER RELATED INVESTIGATIONS            				530
		Surface microphysics 						530
		Theory and related experiments 					531
	BIBLIOGRAPHY         							534
	APPENDIX       								565
										x
	A.  DERIVATIONS OF EQUATIONS       					565
		Equivalent spherical diameter of a spheroidal drop 		565
		Relative velocity and the angle β				566
		Impact-angle measurement in high-velocity collisions 		567
		Actual impact angle in an out-of-plane collision		568
	B.  DATA TABLES 							570