1,721,072 research outputs found
Drop shape visualization and contact angle measurement on curved surfaces
No full textThe shape and contact angles of drops on curved surfaces is experimentally investigated. Image processing, spline fitting and numerical integration are used to extract the drop contour in a number of cross-sections. The three-dimensional surfaces which describe the surface-air and drop-air interfaces can be visualized and a simple procedure to determine the equilibrium contact angle starting from measurements on curved surfaces is proposed. Contact angles on flat surfaces serve as a reference term and a procedure to measure them is proposed. Such procedure is not as accurate as the axisymmetric drop shape analysis algorithms, but it has the advantage of requiring only a side view of the drop-surface couple and no further information. It can therefore be used also for fluids with unknown surface tension and there is no need to measure the drop volume. Examples of application of the proposed techniques for distilled water drops on gemstones confirm that they can be useful for drop shape analysis and contact angle measurement on three-dimensional sculptured surfaces
Some relationships among void fraction, flow complexity and the governing parameters in adiabatic gas-liquid flows
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Flow rates measurement in a gas-liquid mixture by means of phase density signals
No full textAdiabatic two-phase flow in horizontal ducts of 60 mm i.d., 200 diameters long, flowing in plug and slug region, is
investigated by means of 9500 phase density signals captured by local probes. An appropriate processing of phase density
signal puts in evidence the well-known void fraction a and the flow complexity cf. According to considerations concerning the
flow structure and the liquid phase kinetic energy, a correlation among a, cf, UL (UL being the liquid velocity) is expected and
experimentally confirmed. A particular aspect of such correlation is the possibility of measuring the mean flow rates of each
phase of the gas-liquid mixture. The analysis, carried out on data acquired in different experimental campaigns, confirms the
validity of the present method, supplying a good evaluation of phases flow rates. Nevertheless such method is affected by a
difficult and time-consuming experimental detection which prevents practical applications. To overcome this drawback, the
cross section average values of a and cf are determined through few points vertically placed, properly weighting the
experimental values. Such approach allows the continuous, real time, measurement of the flow rates of gas and liquid phases
by means of a single multi-tip probe vertically placed in the duct
Local, Area-averaged and Section-averaged Analysis of Two-phase Flows in Horizontal Ducts with Sudden Section Expansions
No full textRisultati preliminari dell'effetto di una singolarità geometrica asimmetrica sulla struttura di un flusso bifase acqua-aria in condotto orizzontale
No full textA correlation between void fraction, liquid superficial velocity and flow complexity for two-phase flows in ducts with singularities
No full textThe relationships between the cross-section averaged values of void fraction and flow complexity and the values of the other
governing parameters was analysed for adiabatic gas-liquid flows in horizontal ducts with uniform section and with sudden
section changes. Density function signals were acquired using local probes and the cross-sectional values of void fraction and
flow complexity were calculated by area averaging. Correlations were found between the liquid velocity, the void fraction and
the flow complexit
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