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V delu smo numerično modelirali plinsko fokusirani mikro-curek za dostavo vzorcev v femtosekundni kristalografiji. Obravnavali smo standardno obliko mikro-šobe in nominalni pretok plina (helij) 10,8 mg/min (Reg = 198,1 in Weg = 19,3) in kapljevine (voda) 43,2 µl/min (Rel = 111,2 in Wel = 19,0 ) pri Ca = 0,16. Dvofazni sistem kapljevina-plin je bil obravnavan kot nestisljiva idealna mešanica v osni simetriji. Reologija kapljevine je bila obravnavana v okviru potenčne nenewtonske formulacije. Fokusirni plin je bil obravnavan kot idealni plin. V delu je obravnavan newtonski tok in nenewtonski strižno-redčeni tok (^ od 0 do 0,5) in strižno-zgoščevani tok (^ od 1 do 1,5), s ^ = 1,0 ? 10?6 m2/s. Sistem enačb za ohranitev mase in gibalne količine je bil numerično rešen na podlagi metode kontrolnih volumnov. Medfazni rob med plinom in kapljevino je bil določen na podlagi metode volumna tekočine. Pri newtonski tekočini je premer curka 9 µm, dolžina 1538 µm in povprečna hitrost 18,98 m/s. V primerjavi z newtonsko tekočino ima strižno redčeni primer (^ = 0,5) za 6 % večji premer, za 59 % krajši curek in 22 % počasnejši curek, strižno zgoščevana tekočina z ^ = 1,5 pa 33 % večji premer, 43 % daljši in 40 % počasnejši curek. A gas-focused micro-jet used for sample delivery in femtosecond crystallography was numerically modelled. We considered a standard micro-nozzle and a nominal flow rate of gas (helium) 10.8 mg/min (Re^ = 198.1 and We^ = 19.3) and liquid (water) 43.2 µl/min (Re^ = 111.2 and We^ = 19.0) at Ca = 0.16. The two-phase liquid-gas system was considered an incompressible ideal mixture in axial symmetry. The rheology of the liquid was considered in the power law non-Newtonian formulation framework. The focusing gas was considered ideal. The work deals with Newtonian and non-Newtonian shear thinning (^ from 0 to 0.5) and shear thickening (^ from 1 to 1.5) flow, with ^ = 1.0 ⠙ 10⠒6 m2/s . The system of equations for conservation of mass and momentum was numerically solved with the finite volume method. The interface boundary between the gas and the liquid was determined with the volume of fluid method. Newtonian fluid has a jet diameter of 9 µm, length of 1538 µm and average velocity of 19.76 m/s. Compared to the Newtonian fluid, the shear thinning case (^ = 0,5) has a 6 % larger diameter, 59 % shorter jet and a 22 % slower jet, while the shear thickening liquid (^ = 1,5) has a 33 % larger diameter, 43 % longer and 40 % slower jet. |
