Instability development of a viscous liquid drop impacting a smooth substrate

We study the instability development during a viscous liquid drop impacting a smooth substrate, using high speed photography. The onset time of the instability highly depends on the surrounding air pressure and the liquid viscosity: it decreases with air pressure with the power of minus two, and increases linearly with the liquid viscosity. From the real-time dynamics measurements, we construct a model which compares the destabilizing stress from air with the stabilizing stress from liquid viscosity. Under this model, our experimental results indicate that at the instability onset time, the two stresses balance each other. This model also illustrates the different mechanisms for the inviscid and viscous regimes previously observed: the inviscid regime is stabilized by the surface tension and the viscous regime is stabilized by the liquid viscosity.Comment: 4 pages, 5 figure

Splashing of liquids: interplay of surface roughness with surrounding gas

We investigate the interplay between substrate roughness and surrounding gas pressure in controlling the dynamics of splashing when a liquid drop hits a dry solid surface. We associate two distinct forms of splashing with each of these control parameters: prompt splashing is due to surface roughness and corona splashing is due to instabilities produced by the surrounding gas. The size distribution of ejected droplets reveals the length scales of the underlying droplet-creation process in both cases.Comment: 6 pages, 6 figure

Creation of prompt and thin-sheet splashing by varying surface roughness or increasing air pressure

A liquid drop impacting a solid surface may splash by emitting a thin liquid sheet that subsequently breaks apart or by promptly ejecting droplets from the advancing liquid-solid contact line. Using high-speed imaging, we show that air pressure and surface roughness influence both splash mechanisms. Roughness increases prompt splashing at the advancing contact line but inhibits the formation of the thin sheet. If the air pressure is lowered, droplet ejection is suppressed not only during thin-sheet formation but for prompt splashing as well. The threshold pressure depends on impact velocity, liquid viscosity and surface roughness

Liquid drop splashing on smooth, rough and textured surfaces

Splashing occurs when a liquid drop hits a dry solid surface at high velocity. This paper reports experimental studies of how the splash depends on the roughness and the texture of the surfaces as well as the viscosity of the liquid. For smooth surfaces, there is a "corona" splash caused by the presence of air surrounding the drop. There are several regimes that occur as the velocity and liquid viscosity are varied. There is also a "prompt" splash that depends on the roughness and texture of the surfaces. A measurement of the size distribution of the ejected droplets is sensitive to the surface roughness. For a textured surface in which pillars are arranged in a square lattice, experiment shows that the splashing has a four-fold symmetry. The splash occurs predominantly along the diagonal directions. In this geometry, two factors affect splashing the most: the pillar height and spacing between pillars.Comment: 9 pages, 11 figure

Estudio comparativo de métodos analíticos para la determinación de nitratos en aguas

Se ha realizado una puesta a punto y estudio comparativo de los métodos analíticos propuestos por la legislación española para la determinación de ión nitrato en aguas potables y el método ionométrico que utiliza electrodo selectivo de nitratos. El resultado de este estudio es favorable a la utilización del método ionométrico al ser más preciso y de mayor fiabilidad.A comparative study has been made between methods for deterrnjning the presence of N03- in drinking water, that proposed by Spanish legislation, and the ionornetric rnethod which uses a selective nitrate electrode. The result of this study ours the use of the ionometric method as being the most precise and of greater reliability

Determinación de nitratos en aguas de bebida en la provincia de Granada

Se ha realizado un estudio de los niveles de nitratos en las aguas de bebida de 107 poblaciones de la provincia de Granada agrupadas de acuerdo con la cuenca de abastecimiento. Se han seguido los métodos espectrofotométricos recomendados por la legislación española, comparándolos con un método ionométrico. Todas las muestras presentan niveles aceptables de nitratos.A study has been carried on of the nitrate levels in the drinking water of 107 villages. in Granada province. The samples are grouped according to a water supplys's basin. The methods recommended by the Spanish legislation were followed and compared with the ionometric method. All samples have a good concentration of nitrates

We-T classification of diesel fuel droplet impact regimes

A combined experimental and computational investigation of micrometric diesel droplets impacting on a heated aluminium substrate is presented. Dual view high-speed imaging has been employed to visualize the evolution of the impact process at various conditions. The parameters investigated include wall-surface temperature ranging from 140 to 400°C, impact Weber and Reynolds numbers of 19–490 and 141–827, respectively, and ambient pressure of 1 and 2 bar. Six possible post-impact regimes were identified, termed as Stick, Splash, Partial-Rebound, Rebound, Breakup-Rebound and Breakup-Stick, and plotted on the We-T map. Additionally, the temporal variation of the apparent dynamic contact angle and spreading factor have been determined as a function of the impact Weber number and surface temperature. Numerical simulations have also been performed using a two-phase flow model with interface capturing, phase-change and variable physical properties. Increased surface temperature resulted to increased maximum spreading diameter and induced quicker and stronger recoiling behaviour, mostly attributed to the change of liquid viscosity

Determinación de nitratos en aguas de bebida en la provincia de Granada

A study has been carried on of the nitrate levels in the drinking water of 107 villages. in Granada province. The samples are grouped according to a water supplys's basin. The methods recommended by the Spanish legislation were followed and compared with the ionometric method. All samples have a good concentration of nitrates.Se ha realizado un estudio de los niveles de nitratos en las aguas de bebida de 107 poblaciones de la provincia de Granada agrupadas de acuerdo con la cuenca de abastecimiento. Se han seguido los métodos espectrofotométricos recomendados por la legislación española, comparándolos con un método ionométrico. Todas las muestras presentan niveles aceptables de nitratos

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Se ha realizado una puesta a punto y estudio comparativo de los métodos analíticos propuestos por la legislación española para la determinación de ión nitrato en aguas potables y el método ionométrico que utiliza electrodo selectivo de nitratos. El resultado de este estudio es favorable a la utilización del método ionométrico al ser más preciso y de mayor fiabilidad.A comparative study has been made between methods for deterrnjning the presence of N03- in drinking water, that proposed by Spanish legislation, and the ionornetric rnethod which uses a selective nitrate electrode. The result of this study ours the use of the ionometric method as being the most precise and of greater reliability

Decidability of Univariate Real Algebra with Predicates for Rational and Integer Powers

We prove decidability of univariate real algebra extended with predicates for rational and integer powers, i.e., $(x^n \in \mathbb{Q})$ and $(x^n \in \mathbb{Z})$. Our decision procedure combines computation over real algebraic cells with the rational root theorem and witness construction via algebraic number density arguments.Comment: To appear in CADE-25: 25th International Conference on Automated Deduction, 2015. Proceedings to be published by Springer-Verla