An experimental investigation of the primary breakup of round nonturbulent liquid jets in gaseous crossflow is described. Pulsed shadowgraph and holograph observations were made to determine the following breakup properties: primary breakup regimes, conditions required for the onset of ligament and drop formation, ligament and drop sizes along the liquid surface, drop velocities after breakup, rates of liquid breakup along the liquid surface, conditions required for the breakup of the liquid column as a whole, and liquid column trajectories. These observations were made for round nonturbulent liquid jets in subsonic crossflow at normal temperature and pressure. The results suggest qualitative similarities between the primary breakup of nonturbulent round liquid jets in gaseous crossflow and the secondary breakup of drops subjected to shock wave disturbances. Phenomenological analyses were effective to help interpret and correlate the new measurements of the primary breakup properties of nonturbulent round liquid jets in gaseous crossflow. Nomenclature C D = drag coefficient C = empirical constant for the shear layer thickness; Eq. (15) C i = empirical constant for the onset of ligament formation; Eq. (4) C pi = empirical constant for the onset of drop formation; Eq. (5) C t = empirical constant for the time of onset of ligament formation; Eq. (11) C xb = empirical constant for the cross stream penetration of the liquid column; Eq. (23) C yb = empirical constant for the time of breakup of the liquid column; Eq. (21) d i = streamwise jet diameter at onset of drop formation d inj = injector passage diameter d j = liquid jet diameter at jet exit d = diameter of ligaments along the liquid jet surface d p = diameter of drops formed by primary breakup L = injector passage length L b = liquid jet breakup length Oh = liquid jet Ohnesorge number, µ Lshear layer thickness ε = surface efficiency factor; Eq. (27) = wavelength of liquid surface waves µ = molecular viscosity ν = kinematic viscosity ρ = density σ = surface tension Subscripts b = location of breakup of entire liquid jet G = gas property i = location of onset of breakup j = jet exit property L = liquid property = ligament property p = property of drops formed by primary breakup ∞ = ambient gas property

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An experimental investigation of the deformation and breakup properties of turbulent round liquid jets in uniform gaseous crossflows is described. Pulsed shadowgraph and holograph observations were obtained for turbulent round liquid jets injected normal to air crossflow in a shock tube. Crossflow velocities of the air behind the shock wave relative to the liquid jet were subsonic (36-90 m=s) and the air in this region was at normal temperature and pressure. Liquid injection was done by a pressure feed system through round tubes having inside diameters of 1 and 2 mm and length-to-diameter ratios greater than 100 to provide fully developed turbulent pipe flow at the jet exit. Test conditions were as follows: water and ethyl alcohol as test liquids, crossflow Weber numbers based on gas properties of 0-282, streamwise Weber numbers based on liquid properties of 1400-32,200, liquid/gas density ratios of 683 and 845, and jet exit Reynolds numbers based on liquid properties of 7100-48,200, all at conditions in which direct effects of liquid viscosity were small (Ohnesorge numbers were less than 0.12). Measurements were carried out to determine conditions required for the onset of breakup, ligament and drop sizes along the liquid surface, drop velocities after breakup, liquid column breakup as whole, rates of turbulent primary breakup, and liquid column trajectories. Phenomenological theories proved to be quite successful in interpreting and correlating the measurements.

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The formation of ligaments and drops at the liquid surface during primary breakup of turbulent liquid jets in still air, that is, during turbulent primary breakup, was studied experimentally using pulsed shadowgraphy and holography. Experimental conditions included round and plane (the latter actually being annular with a large aspect ratio) turbulent liquid jets in still air at normal temperature and pressure for noncavitating water and ethanol ows, long length/hydraulic-diameter (greater than 40:1) injector passages to provide fully developed turbulent pipe ow at the jet exit, jet exit Reynolds numbers of 6 £ £ 10 3 -4:24 £ £ 10 5 , jet exit Weber numbers of 200-300,000, and liquid/gas density ratios of 690 and 860 at conditions where direct effects of liquid viscosity were small (for example, jet exit Ohnesorge numbers were smaller than 0.0053). Measured properties included liquid surface velocities, conditions at the onset of ligament and drop formation, ligament and drop sizes along the surface, and ligament and drop velocities along the surface and rates of drop formation along the surface. Simpli ed phenomenological theories were used to help interpret and correlate the measurements. Nomenclaturecient of the Sauter mean diameter at onset of drop formation (SMD i ) correlation C s x = coef cient of the SMD(x) correlation C xr = coef cient of the .x i ¡ x`i /=.u 0 t r i / correlation d = round jet exit diameter d h = jet exit hydraulic diameter d`= ligament effective diameter; Eq. (1) d`i = d`at onset of ligament formation L a = aerodynamic ligament breakup length L c = mean ligament breakup length L`= ligament length at breakup P m 00 f = mass ux of drops relative to surface Oh f d = jet exit Ohnesorge number, ¹ f =.½ f d h ¾ / 1=2 Re f d = jet exit Reynolds number, ½ f u 0 d h =¹ f Re f`= ligament Reynolds number, ½ f u`d`=¹ f t a = aerodynamic ligament breakup time t`i = ligament breakup time at onset of ligament formation t r = Rayleigh breakup time of a ligament of diameter dt r i = Rayleigh breakup time at onset of drop formation u`= velocity along ligament axis N u s = mean streamwise surface velocity u 0 = average streamwise velocity at jet exit Q u = mass averaged streamwise drop velocity v`i = velocity of characteristic eddy at onset of ligament formation Q v r = mass average cross stream drop velocity relative to surface N v 0 0 = average rms cross stream velocity uctuation at jet exit

An experimental and computational investigation of the primary breakup of nonturbulent and turbulent round liquid jets in gas crossflow is described. Pulsed shadowgraph and holograph observations of jet primary breakup regimes, conditions for the onset of breakup, properties of waves observed along the liquid surface, drop size and velocity properties resulting from breakup and conditions required for the breakup of the liquid column as a whole, were obtained for air crossflows at normal temperature and pressure. The test range included crossflow Weber numbers of 0-2000, liquid/gas momentum ratios of 100-8000, liquid/gas density ratios of 683-1021, Ohnesorge numbers of 0.003-0.12, jet Reynolds numbers of 300-300,000. The results suggest qualitative similarities between the primary breakup of nonturbulent round liquid jets in crossflows and the secondary breakup of drops subjected to shock wave disturbances with relatively little effect of the liquid/gas momentum ratio on breakup properties over the present test range. The breakup of turbulent liquid jets was influenced by a new dimensionless number in terms of liquid/gas momentum ratio and the jet Weber number. Effects of liquid viscosity were small for present observations where Ohnesorge numbers were less than 0.4. Phenomenological analyses were successful for helping to interpret and correlate the measurements.