Parametric study of cone angle influence on bubble vortex breakdown onset in laminar conical flow at various swirl numbers

The current work studies a swirling laminar viscous pipe flow with a controllable swirl number and varying pipe divergence cone angle. Such flows are widely used in various engineering applications. When a certain level of flow swirl is reached, a phenomenon called vortex breakdown occurs, the characteristics of which depend on the intensity of swirling of the flow and the Reynolds number. However, in addition to these two parameters, an important influence is exerted by the pipe opening angle, which often does not allow generalizing the results obtained in the pipe flow with even slightly different angles. Since experimentally it is quite difficult and expensive to change the pipe angle, especially considering the water as working fluid, this issue could be solved using CFD techniques. Using the design study, 63 different combinations of S and α are considered. The effect of the pipe divergence angle on the position of the bubble vortex breakdown and its properties is demonstrated. It is shown that there is a nonlinear relationship between the position of the bubble breakdown onset and the minimum value of the axial velocity at the axis depending on the opening angle of the cone.

The characters exploration of a piezoelectric pump with fishtail-shaped bluffbody

This paper focuses on a new structure in the valveless piezoelectric pump, which has a combination structure of the conical flow channel and two fishtail-shaped bluffbodies in the chamber of the pump. The fishtail-shaped bluffbody is inspired by the shape of the swimming fish to diminish the backflow and optimize the performance of the pump. The performance is studied by changing the shape and size of the inlet and outlet, the bluff bodies’ height and the space between two bluff bodies. The results show that the 3 mm × 3 mm square inlet, 3 mm diameter round outlet, 3 mm height of bluffbodies, 6.8 mm pitch of bluffbodies has a best performance in all 10 prototypes, which implements a maximum flow rate of 87.5 ml/min at 170 V 40 Hz with a noise of 42.6 dB. This study makes a preliminary investigation and theoretical explanation for the subsequent optimization of this structure, improved the performance of the valveless piezoelectric pump, broaden the thinking of the design for the bluffbody for better performance of the valveless piezoelectric pump.

Shock-less Hypersonic Intakes

The accuracy of CFD for simulating hypersonic air intake flow is verified by calculating the flow inside a Busemann type intake. The CFD results are then compared against the “exact” solution for the Busemann intake as calculated from the Taylor-McColl equations for conical flow. The method proposed by G. Emanuel (the Lens Analogy) for generating an intake shape that transforms parallel and uniform hypersonic (freestream) flow isentropically to another parallel and uniform, less hypersonic, flow has been verified by CFD (SOLVER II) simulation, based on Finite Volume Method (FVM). The shock-less (isentropic) nature of the Lens Analogy (LA) flow shapes has been explored at both on and off-design Mach numbers. The Lens Analogy (LA) method exhibits a limit line (singularity) for low Mach number flows, where the streamlines perform an unrealistic reversal in direction. CFD calculations show no corresponding anomalies.

Shock-less Hypersonic Intakes

The accuracy of CFD for simulating hypersonic air intake flow is verified by calculating the flow inside a Busemann type intake. The CFD results are then compared against the “exact” solution for the Busemann intake as calculated from the Taylor-McColl equations for conical flow. The method proposed by G. Emanuel (the Lens Analogy) for generating an intake shape that transforms parallel and uniform hypersonic (freestream) flow isentropically to another parallel and uniform, less hypersonic, flow has been verified by CFD (SOLVER II) simulation, based on Finite Volume Method (FVM). The shock-less (isentropic) nature of the Lens Analogy (LA) flow shapes has been explored at both on and off-design Mach numbers. The Lens Analogy (LA) method exhibits a limit line (singularity) for low Mach number flows, where the streamlines perform an unrealistic reversal in direction. CFD calculations show no corresponding anomalies.

MusE GAs FLOw and Wind (MEGAFLOW) IV. A two sightline tomography of a galactic wind

ABSTRACT Galactic outflows are thought to eject baryons back out to the circumgalactic medium. Studies based on metal absorption lines (Mg ii in particular) in the spectra of background quasars indicate that the gas is ejected anisotropically, with galactic winds likely leaving the host in a bi-conical flow perpendicular to the galaxy disc. In this paper, we present a detailed analysis of an outflow from a z = 0.7 ‘green-valley’ galaxy [log (M*/M⊙) = 9.8; $\mbox{SFR}=0.5\, \mathrm{M}_{\odot }\, \mathrm{yr}^{-1}$] probed by two background sources from the MusE GAs FLOw and Wind (MEGAFLOW) survey. Thanks to a fortuitous configuration with a background quasar (SDSSJ1358 + 1145) and a bright background galaxy at z = 1.4, both at impact parameters of $\approx\! 15\, \hbox{kpc}$, we can – for the first time – probe both the receding and approaching components of a putative galactic outflow around a distant galaxy. We measure a significant velocity shift between the Mg ii absorption from the two sightlines ($84\pm 17\, \hbox{km~s$^{-1}$}$), which is consistent with the expectation from our simple fiducial wind model, possibly combined with an extended disc contribution.

INVESTIGATIONS OF APPLYING BIOLOGICAL PRODUCT BIOKAL1 ON POTATO CROPS WITH SPECIFIC EQUIPMENT LECHLER DROPLEGUL FOR SPRAYING UNDER THE LEAVES OF CULTURAL PLANTS

The application of insecticides and fungicides on the underside of leaves is performed with a help various technological solutions, seemingly as the application of soil herbicides and liquid mineral fertilizers that are sprayed under the leaves of cultural plants. This task is performed using straight spraying pipes with slit (symmetrical and asymmetrical flow) nozzles, stream conical flow nozzles, or specific curved (e. g. Lechler DroplegUL) nozzles that enable diagonal spraying upwards. The objective of the research was to identify the potato coverage differences spraying the biological product biokal1 with specific equipment Lechler DroplegUL for spraying the biological product under the leaves and various nozzles. In earlier stages of potato growth, the specific equipment Lechler DroplegUL and deflection nozzles Lechler FT 1.0 for spraying the product under the leaves of cultural plants better covers potato stems and the underside of upper leaves. In the control group, where the ultimate slit flat flow nozzles Hardi ISO F/LD-05-110 were used, droplets of the biological product covered 4.8±1.7 % of potato stem area only, the DroplegUL and three nozzles (LU-120-02 from the top and two deflection nozzles Lechler FT 1.0 from the bottom) covered even 55.8±39.1 %. Accordingly, plants of the control group had only 0.1±0.1 % of the underside area of the upper leaves covered with the product, while using DroplegUL and three nozzles such area reached 1.5±1.1 %. In later stages of potato growth, specific equipment Lechler DroplegUL with deflection nozzles Lechler FT 1.0 for spaying under the leaves of cultural plants better covered the underside of upper leaves of potatoes only. The usage of double flow nozzles Lechler DF-120-02 on DroplegUL and ultimate slit flat flow nozzles LU-120-02 on a spraying boom gave rather small differences in coverage of the surface compared the control group, where the ultimate slit flat flow nozzles Hardi ISO F/LD-05-110 were used.

Conical approximation and asymptotic stability

This chapter presents a technique of approximating a hybrid system with a conical hybrid system: a system with conical flow and jump sets and with constant or linear flow and jump maps. The main result here deduces pre-asymptotic stability for the original system from pre-asymptotic stability for the conical approximation. This result generalizes, to a hybrid system, the result that asymptotic stability for the linearization of a differential equation implies asymptotic stability for the differential equation. In many cases, the analysis of the conical approximation is simpler than of the original hybrid system; this is illustrated in several examples later in the chapter.