Twenty-First Symposium on Naval Hydrodynamics (1997) / Chapter Skim
Currently Skimming:
Spray Formation at the Free Surface of Turbulent Bow Sheets
Spray Formation at the Free Surface of Turbulent Bow Sheets
Pages 490-505
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 490... ...
Transition to a roughened liquid surface could be correlated by associating die Sickness of He growing turbulent boundary layer along the was with He thickness of the wall jet Drop sizes at He onset of turbulent primary breakup could be correlated by equating He surface energy required to form a drop to He k~nenc energy of an eddy of corresponding size. Finally, the location of He onset of turbulent primary breakup could be correlated In teens of Be distance convected at He mean vel~ty of He was jet for a time needed to Spate He Rayleigh breakup of the ligaments prodding from He liquid surface Hat produce drops at the onset of turbulent primary breakup.
|
From page 491... ...
~ the liquid surface, or its development along the surface, with He subsequent appearance of a t;urbuTence-wrir~cled interface between the liquid and gas and eventually tile fonnation of drops due to turbulent primary breakup at the liquid surface. An important issue concerning Be Mansions of turbulent bow sheets is the origin of the turbulence near He liquid surface, e.g., whether this turbulence mainly is caused by motion along the bow surface or whether it mainly results from aerodynamic forces at He liquid surface.
|
From page 492... ...
I The liquid flow along He surface Ten involves a relatively inconsequential lalIlinaIe boundary layer, followed by a growing turbulent boundary layere The onset of liquid surface roughness END OF PRIMARY °''..o°;° BREAKUP (TYP.)
|
From page 493... ...
The present measurements considered the onset condi~aons for a roughened liquid surface, Me location of the onset of turbulent primary breakup along the surface, and the drop sizes produced at Me onset of turbulent primary breakup. The experiments involved various liquids injected as was jets into still air at NTP, wig Me flows observed using pulsed photography, shadowgraphy and holography.
|
From page 494... ...
Pulsed shadowgraph photography was used to measure turbulent primary breakup properties near the onset of breakup as wed as He s~eamwise location of He onset of breakup. The holocamera was used for this purpose with He reference beam blocked to Beet a shadowgraph rather Han a hologram.
|
From page 495... ...
For these conditions, He boundary layer along the wall is lacunas prior to reaching He gripping wire as well, wig growth of a turbulent boundary layer beginning along He wall at He location of He Hipping wire. Bow transitions of interest during He present ~nvestiga~aon onset of a roughened liquid surface and onset of turbulent primary breakup can be seen in He flash photographs of Fig.
|
From page 496... ...
Ripped turbulent boundary layer reaches We surface first. Boundary layer development within He was layer will be simplified considerably for present analysis of this problem, as follows: effects of He Bee surface on boundary layer growth will be ignored; variation of wall jet mean velocity and thickness win be ignored because values of xib are modest for bow present test conditions and most practical bow sheets (x/b ~ 1001; aerodynamic effects m11 be ignored as discussed earlier, He wall surface win be assumed to be smooth; and liquid properties will be assumed to be constant.
|
From page 497... ...
proceeded ~ two stages, involving consideration of die vacation of x, with Rep, and evaluation of die varia~aon of xr with Upping wire properties. The latter considerations showed that the onset of liquid surface roughness due to a turbulent boundary layer along He wall was not significantly affected by Upping wire `2' properties as long as U*
|
From page 498... ...
Except for low values of ReD, where poorly developed turbulence ~ He boundary layer probably retards the appearance of a wrinkled liquid surface (24) , a correlation based on mpped turbulent boundary layer predictions of equation (5)
|
From page 499... ...
wnnkled liquid surface. This suggested Rat Be wall jet is reasonably turbulent at the onset of turbulent primary breakup so Tat tile turbulence properties of Be was jet can be taken to be Be same as a fury-developed turbulent pipe flow for Be same hydraulic diameter ReD (5,61.
|
From page 500... ...
For fillly-developed turbulent pipe flow, v/is a constant (5,61; therefore, SEA should only be a function of Wee for present test conditions. Finally, analogous to Me earlier studies of turbulent primary breakup for round turbulent free jets (22,23)
|
From page 501... ...
He distance required for We onset of turbulent primary breakup is Men obtained relanve to the fist appearance of significant effects of turbulence at Me liquid surface? as follows: hi- X ~ UoTi An expression for xi - xr is subsequently found by subsutu~g equation (14)
|
From page 502... ...
For present conditions, where turbulent bounder,, layer growth was ideated by a s02 Dip wire, distances to tile onset of a roughened liquid surface could be correlated based on a turbulent boundary layer thickness expression, see equation (6~. Drop sizes at the onset of turbulent primary bqeahlp along the liquid surface could be correlated by equating die surface energy required to form a drop to tile lcine~ac energy of an eddy of corresponding size thin He Herbal region of He turbulence spectrum, see equation (13~.
|
From page 503... ...
In addition, the streammse evolution of drop sizes and velocities produced by turbulent primary breakup, and the rate of liquid removal from the wall jet due to turbulent primary breakup, are issues that meet Atkinson in He future. ACKNOWLEDGMENTS This research was sponsored by He Office of Naval Research Grant No.
|
From page 504... ...
23. Wu, P.-K., and Faeth, G.M., "Aerodynamic Effects in Primary Breakup of Turbulent Liquids," Atomization and Sprays, Vol.
|
From page 505... ...
The presence of a developing turbulent boundary layer along the surface of the wall jets is fundamentally important because the surface only becomes roughened (which is a prerequisite for turbulent primary breakup) when the outer edge of this boundary layer reaches He surface.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.