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SPRAY STRUCTURE STUDIES Neale Thomas* - FRED Ltd, Aston Sci-Park, Birmingham B7 4BJ nhtFRED@aol / 0121 471 4149 / 0468

SPRAY STRUCTURE STUDIES Neale Thomas* - FRED Ltd, Aston Sci-Park, Birmingham B7 4BJ nhtFRED@aol.com / 0121 471 4149 / 0468 445475. flat fan nozzles - agricultural applications deposition - crop compliance / tortuosity coverage - little drops // control - big drops

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SPRAY STRUCTURE STUDIES Neale Thomas* - FRED Ltd, Aston Sci-Park, Birmingham B7 4BJ nhtFRED@aol / 0121 471 4149 / 0468

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  1. SPRAY STRUCTURE STUDIESNeale Thomas* - FRED Ltd, Aston Sci-Park, Birmingham B7 4BJ nhtFRED@aol.com / 0121 471 4149 / 0468 445475 • flat fan nozzles - agricultural applications • deposition - crop compliance / tortuosity • coverage - little drops // control - big drops • external interaction - wind drift factors • internal formation - drop-size factors • enhancement strategies - internal / external • sheet fragmentation - exploitation avenues • & Duncan Webb with FRED Ltd 1993-97 // ILASS-EUR (UMIST, 7/98)

  2. WIND DRIFT FACTORS • Jeremy Phillips - PhD (1998) project 90-94 • Silsoe (Miller) + DAMTP (Hunt) + Brum (me) • companion study to Ghosht & Hunt theory (JFM 97) • downstream drift data from flat fan triplets • fines scavenging into porosity concentrations • spray sheet edges as sources of scouring vorticity • redispersion via boundary blocked entrained airflow • spanwise nonuniformity and streamwise vorticity

  3. DROP SIZE FACTORS • Quanbao Zhou - PhD (1997) project 93-96 • Silsoe (Miller, Walklate) + Brum (me) • also CFD for internal flows - but rapid straining? • turbulator inserts and drop-size distribution • destabilisation of fan evolution / early break-up • bigger drops / narrower distribution - less drift • complements recent emphasis on properties • surface active agents - Silsoe (?? - Open Day)

  4. ENHANCEMENT - INTERNAL • Bubble nozzles - height of copycat fashion • ? after Lefebrve / Billericay Farm patent (19??) • venturi induction / forced injection (compressor) • hollow drops more than bubbles - thick film • undefined numbers of air inclusions per drop • unspecified impact behaviour - supposedly shatter into suspension of film microdrops but deposition? • bigger drops - less drift? - inertial size not diameter?

  5. ENHANCEMENT - EXTERNAL • Bag boomers - recent top-dog sector fashion • ? originator / Hardi featured product especially • ducted airfan co-flow swamping natural entrainment • blown air sheathes flat fan spray emission • fines migrate due to vorticity shear scavenging • curtain blockage intensifies ambient local wind • exacerbates scour into farfield streamwise contrails • secondary resuspension into ground-blocked airflow

  6. SHEET FRAGMENTATION • vulnerability of incipiently breaking edge • exploitation opportunity unrivalled elsewhere • internal flows intensive - expensive to manipulate • external flows dispersive - expensive to recapture • sheet stretching by focused co-flow airjet • thinner fragmentation - smaller dropsizes • sheet flapping by edge separation galloping • cluster generation - vorticity confined transport

  7. CONCEPT CONVERSION • DTI SMART Awards 92-95 to FRED Ltd • principle + prototype + patent aokay // product? • Environment Award - GB Inventions Fair 1996 • encouragement of flat-fan extensional flow • quasi-coplanar airjet - plus Coanda lock-on? • excitation of flexural+oscillatory deflections • momentum matching of air and liquid sheets • coupling edge-separation + effective elasticity

  8. PROTOPRODUCT PROSPECTS • SPRAY • Stimulated Pulsation Ranging Application deliverY • conceived and created for agrochemical application • generic natural generation of phase-locked clusters • collective character of spray clustering • focus of Candel’s plenary at ICMF 98 Congress • impact on combustion / efficiency / exhaust quality • need for modelling methods for transport transients • simulation of eddy / vorticity scavenging as key feature

  9. MULTIPHASE MECHANICS • Xiaogang Yang - PhD (1996) project 91-95 • Brum (me) /CVCP+FREDucational Foundation • extension of DVM in Sene, Hunt, Thomas (JFM 94) • Lagrangian-Lagrangian transport simulation • DVM suffices for free eddy patterns + stresses • force law with discrete phase density as parameter • complements Crowe’s work in Stokes number limit • Crowe (ICMF ‘98) - DVM as good as LES for spray

  10. AGROCHEMICAL ASPECTS • Compromise on crop coverage + wind drift • 250 micron VMD as unassisted standard basis • 225 effective VMD associated with bubble sprays • 200 VMD controllable with bagged boomers • 125 VMD accessible with airjet SPRAY system • Coverage - a contentious and unclear issue • rough guideline for bio-efficacy is drop number • halving dropsize implies 8-fold saving on chemical

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