Experimental investigation of charged liquid jet efflux from a capillary

The shapes and electrical characteristics of charged liquid (water, ethanol, glycerol, castor oil) jets emitted from a metal capillary have been experimentally studied depending on the applied high voltage. A map of efflux regimes in the flow velocity-applied voltage coordinates is constructed for water. The effects of medium viscosity, surface tension, and charge relaxation time on the laws of jet efflux are analyzed.     

Certain characteristics of the monodisperse disintegration of a liquid jet

We examine the process of the monodisperse disintegration of a capillary jet of water in the presence of transverse oscillations of the outlet orifice. We have determined the values of the parameters at which this process begins; we demonstrate the effect of individual factors on the form of the discrete disintegration of the jet.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 16, No. 3, pp. 536–538, March, 1969.     

Experimental investigation of the effect orifice shape and fluid pressure has on high aspect ratio cross-sectional jet behaviour.

Prevention of major disasters such as Piper Alpha is a concern of oil and gas companies when commissioning a new offshore superstructure. Safety studies are undertaken to identify potential major hazards, risks to personnel and that sufficient precautions have been employed to minimise these. Such an assessment will also include the consideration of the protection from gas leaks such as the optimum positions of gas leak detectors and startup safety procedures after a leak. This requires a comprehensive knowledge of the behaviour of the leaking hydrocarbons as they emerge from the leak into the area of concern. Such leaks are most likely to emanate from a high aspect ratio cross-sectional curved slot in a pipeline. This paper challenges the conventional view that it is sufficient to model such leaks as axisymmetric jets. This paper is therefore concerned with an experimental study carried out on a series of more realistic high aspect ratio cross-sectional jets issuing from a flange orifice. Both high quality photographs in both planes of the jets and some quantitative pressure data is examined for a high aspect ratio cross-sectional jet of air at pressures up to 4.136bar. The effect of changing aspect ratio, fluid pressure and orifice shape will be discussed and put into context with regard to how this relates to offshore analysis studies.     

Theoretical investigation of the signal-to-noise ratio in fluorescence lifetime imaging

We deduce the signal-to-noise ratio for fluorescence lifetime imaging when using frequency-domain methods. We assume mono-exponential decay and quantum-noise-limited performance. The results are compared with Monte Carlo simulations with good agreement. We also compare our results with previous investigations of time-domain methods for fluorescence lifetime imaging. For a given number of detected photons, we find that frequency-domain and time-domain methods are equally good. The correct choice of detection technique and its parameters is important for obtaining good results.     

Propagation characteristics of the dynamic state in a capillary discharge jet

A study is made of the so-called dynamic state of a metastable substance, characterized by the onset of a nonequilibrium energy interaction (interchange), involving various waves, in the excited material. The intensity of the optical emission is used to analyze the dynamic state; an investigation is made of the propagation of its leading and trailing edges. Various propagation characteristics and natural solitary-wave forms are identified; their similarity to ionization waves allows making some assumptions about the essential nature of this process. The observed effects are important for establishing the physical conditions for the formation of the substance of ball lightning and are also interesting for the physics of flames, electrical breakdown, and electrode spots. Pis’ma Zh. Tekh. Fiz. 23, 54–59 (October 12, 1997)     

An experimental investigation of capillary breakup of a liquid metal jet

The limits of influence of oxidation on the capillary breakup of a liquid metal jet is investigated. It is shown that in a region of weak oxidation the disruption of the jet proceeds as is usual for a Newtonian fluid.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 60, No. 4, pp. 554–557, April, 1991.     

Maximum signal-to-noise ratio of a tape recorder

Using the Wiener autocorrelation theorem, the noise power spectrum of the pole strength in a thin lamina of an erased tape is shown to be approximately white. The noise power spectrum of the reproduce head voltage is calculated for a thick tape and compared with the signal power. The wide-band signal-to-noise ratio of a tape recorder equalized flat is deduced and expressed in very simple forms, which are inversely dependent upon the square of a bandwidth. Notably, in this special case the wide-band result is independent of reproduce head-to-tape spacing. Numerical examples demonstrate that this simple theory yields results in excellent agreement with practice.     

Experimental investigation of the mixing performance of a lobed jet flow

An experimental investigation of flow in a turbulent isothermal air lobed jet is presented. A lobed jet is compared, in the near field, with an isothermal axisymmetric jet with the same exit Reynolds number in terms of dynamics and mixing enhancement. It was found that the streamwise variation of the volumetric flow rate is characterized by a slope is more than twice larger than that for the reference circular jet. This high entrainment rate is governed, at the same time, by the turbulent structures generated by the asymmetric shape of the nozzle and by the high convection in these structures induced by the inner and outer penetration angles of their lobes. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 1, pp. 102–107, February–March, 2008.     

Experimental investigation of a turbulent jet in turbulent cross flow

The characteristics of an axisymmetric turbulent jet propagating in a cross flow with a high degree of turbulence are investigated experimentally.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 2, pp. 225–228, August, 1982.     

小型制冷装置毛细管实验研究

设计并建造了一套小型制冷装置的毛细管实验研究台以及基于Labview的计算机数据采集系统,改变毛细管的组合方式和实验工况,得到了一系列实验数据,并对其进行处理,得出了过冷度、毛细管长度、毛细管进口压力、出口压力等参数与质量流量之间的关系.     

Investigation of the evolution of the spectrum of oscillations of the surface of a jet of liquid with forced capillary breakup

The results of an experimental study of the spectral composition of the surface oscillations of a jet of liquid at different distances from the point of efflux from the head of the apparatus which produces forced capillary breakup of fluid jets are presented.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 60, No. 4, pp. 550–553, April, 1991.     

Experimental measurements of estimator bias and the signal-to-noise ratio for deconvolution from wave-front sensing

Deconvolution from wave-front sensing (DWFS) has been proposed as a method for achieving high-resolution images of astronomical objects from ground-based telescopes. The technique consists of the simultaneous measurement of a short-exposure focal-plane speckled image, as well as the wave front, by use of a Shack-Hartmann sensor placed at the pupil plane. In early studies it was suspected that some problems would occur in poor seeing conditions; however, it was usually assumed that the technique would work well as long as the wave-front sensor subaperture spacing was less than r(0) (L/r(0) < 1). Atmosphere-induced phase errors in the pupil of a telescope imaging system produce both phase errors and magnitude errors in the effective short-exposure optical transfer function (OTF) of the system. Recently it has been shown that the commonly used estimator for this technique produces biased estimates of the magnitude errors. The significance of this bias problem is that one cannot properly estimate or correct for the frame-to-frame fluctuations in the magnitude of the OTF but can do so only for fluctuations in the phase. An auxiliary estimate must also be used to correct for the mean value of the magnitude error. The inability to compensate for the magnitude fluctuations results in a signal-to-noise ratio (SNR) that is less favorable for the technique than was previously thought. In some situations simpler techniques, such as the Knox-Thompson and bispectrum methods, which require only speckle gram data from the focal plane of the imaging system, can produce better results. We present experimental measurements based on observations of bright stars and the Jovian moon Ganymede that confirm previous theoretical predictions.     

Experimental and numerical investigation of the effect of shock wave characteristics on the ejector performance

The entrainment performance and the shock wave structures in a three-dimensional ejector were investigated by Computational Fluid Dynamics (CFD) and Schlieren flow visualization. The ejector performance was evaluated based on the mass flow rates of the primary and secondary flows. The shock wave structures in the ejector mixing chamber were captured by the optical Schlieren measurements. The results show that the expansion waves in the shock train do not reach the mixing chamber wall when the ejector is working at the sub-critical mode. Decreasing of the shock wave wavelength increases the secondary mass flow rate. A three-dimensional CFD model with four turbulence models was then compared with the experimental data. The results show that the RNG k-ε model agrees best with measurements for predictions of both the mass flow rate and shock wave structures.     

Experimental investigation on diabatic flow of R-134a through spiral capillary tube

The present experimental investigation has been carried out to investigate the effects of various geometric parameters on the mass flow rate of R-134a through diabatic spiral capillary tube. In diabatic flow, the capillary tube is bonded with the compressor suction-line to form a counter-flow exchanger. The lateral type of diabatic capillary tube has been investigated in the present experimental study. The major geometric parameters investigated are capillary tube diameter, capillary tube length and coil pitch. In addition, effect of inlet subcooling on the mass flow rate through diabatic spiral capillary tube is also done. A comparison of the performance of diabatic spiral capillary tube has been made with adiabatic spiral capillary tube. Generalized empirical correlation for diabatic spiral capillary tube has also been proposed. It has been found that the predictions of the proposed correlation lie in the error band of ±7%.     

鹅掌楸树叶气动特性研究

通过摄像统计实验以及风洞天平测力实验来研究真实鹅掌楸树叶气动特性,发现在风洞中随着风速的增加,当达到临界风速时,鹅掌楸树叶会发生状态突变,最后出现形状重构现象;真实鹅掌楸树叶反面作为迎风面时相对于正面作为迎风面时更为稳定;真实鹅掌楸树叶在来流方向的阻力系数随着雷诺数的增加趋近于0.1.     

Experimental investigation of the heat exchange of a subsonic jet from a normally disposed flat obstacle

Results of investigations are processed in the form of dependences for the Nusselt number at the stagnation point taking account of free-stream pulsations. The experiments are compared with a computation by an approximate method [8].     

Experimental investigation of lift and drag on a ball rotated by an inclined water jet

Abstract

The lift and drag of rotating balls with Reynolds numbers from 4500 to 6500 were obtained using a ping‐pong ball impinged by a water jet with inclination angles ranging from θ = 3.43° to 11.3°. Results show that water strikes the ball surface and leaves from the wake region behind the ball, which spins more slowly when a large amount of water stays on the ball surface, causing low lift and low drag forces to be exerted on the ball. In contrast, the ball spins quickly when a small amount of water stays on the ball surface. This causes high lift force to be exerted on the ball, which verifies the Magnus effect of a rotating ball. The drag force increases nonlinearly with the angular speed of the ball because there is a branch flow out from the stretched wake behind the ball. Results also indicate that the lift force of the ball increases with jet exit speed, but the drag force does not change significantly with the jet exit speed. This reveals that the momentum change in the direction parallel to gravity is more significant than that in the direction normal to gravity.     

超空泡流下壳结构模型动态特性实验研究

首次采用首部钢丝绳牵引方式进行了超空泡流下壳结构模型实验。实验模型壳体部分采用聚碳酸酯材料,锥部采用铝合金材料,首部空化器则采用不锈钢制作,最后各部分通过螺纹或者胶水粘结而成。三种不同速度下的超空泡实验结果表明：采用首部钢丝绳牵引方式进行超空泡实验是可行的。位于壳体上相对位置相同的部位其应变曲线趋势一致,超空泡形成后轴向的减阻效果是非常明显的,尾拍振动引起的应变则呈现出周期性的特征。在一定速度下,超空泡形成后轴向力引起的应变和尾拍振动引起的应变处于同一个水平上。随着速度的提高,超空泡减阻的效果更加明显,尾拍振动引起的应变幅值也相应增大。实验结果可为超空泡水下航行体的结构设计提供依据。     

Influence of temperature on the sensitivity and signal-to-noise ratio of a fiber-optic surface-plasmon resonance sensor

We have theoretically analyzed the influence of temperature on the performance of a fiber-optic sensor based on surface-plasmon resonance (SPR). The performance of the sensor has been evaluated in terms of its sensitivity and signal-to-noise ratio (SNR). The theoretical model for temperature dependence includes the thermo-optic effect in the fiber core and sensing layer, and phonon-electron scattering along with electron-electron scattering in the metal layer. The effect of temperature on the SNR and the sensitivity of the sensor with two different metals has been compared. The same comparison is carried out for the sensing layers with positive and negative thermo-optic coefficients. The theoretical model has been analyzed for both the nonremote and remote sensing cases. This detailed analysis of temperature-dependent SNR and sensitivity leads to achieving the best possible performance from a fiber-optic SPR sensor against the temperature variation.