Quantitative two-dimensional instantaneous Raman concentration measurements in a laminar methane jet

We have achieved quantitative two-dimensional Raman measurements of the concentration of methane in a laminar methane jet into nitrogen without multipassing the incident laser sheet with a coaxial flash-lamp-pumped dye laser. The measurements are compared with the results of direct numerical simulation for the particular flow field. We conclude that the accuracy of the technique is determined by limitations in the dynamic range and in the spatial resolution of the data acquired with an intensified camera.     

Three-dimensional simulation of a plasma jet with transverse particle and carrier gas injection

In the present paper, three-dimensional modeling results are presented concerning the turbulent thermal plasma jet with transversely injected carrier gas and metal particles at atmospheric pressure. The standard K− model is employed for the numerical simulation of the turbulent plasma flow in coupling with the variable-property continuity, momentum and energy equations. For predicting the motion of the injected particles in the turbulent flow field, an improved particle stochastic-trajectory model is adopted in the calculation. The heating histories of the injected particles are also calculated in their moving processes. The modeling results show that including the effect of carrier gas on jet and particle behavior is very important. The plasma jet is deflected from its geometrical axis due to the transverse injection of carrier gas, and the particle trajectories are also appreciably changed by the carrier gas injection. The particles disperse around their average trajectories in the turbulent flow field.     

Enzyme kinetic measurements using a droplet-based microfluidic system with a concentration gradient

In this paper, we propose a microfluidic device that is capable of generating a concentration gradient followed by parallel droplet formation within channels with a simple T-junction geometry. Linear concentration gradient profiles can be obtained based on fluid diffusion under laminar flow. Optimized conditions for generating a linear concentration gradient and parallel droplet formation were investigated using fluorescent dye. The concentration gradient profile under diffusive mixing was dominated by the flow rate at sample inlets, while parallel droplet formation was affected by the channel geometry at both the inlet and outlet. The microfluidic device was experimentally characterized using optimal layout and operating conditions selected through a design process. Furthermore, in situ enzyme kinetic measurements of the β-galactosidase-catalyzed hydrolysis of resorufin-β-d-galactopyranoside were performed to demonstrate the application potential of our simple, time-effective, and low sample volume microfluidic device. We expect that, in addition to enzyme kinetics, drug screening and clinical diagnostic tests can be rapidly and accurately performed using this droplet-based microfluidic system.     

New seeding methodology for gas concentration measurements

This paper presents the first demonstration of the pulsed laser ablation technique to seed a laminar non-reacting gaseous jet at atmospheric pressure. The focused, second harmonic from a pulsed Nd : YAG laser is used to ablate a neutral indium rod at atmospheric pressure and temperature. The ablation products generated with the new seeding method are used to seed the jet, as a marker of the scalar field. The neutral indium atoms so generated are found to be stable and survive a convection time of the order of tens of seconds before entering the interrogation region. The measurements of planar laser-induced fluorescence (PLIF) with indium and laser nephelometry measurements with the ablation products are both reported. The resulting average and root mean square (RMS) of the measurements are found to agree reasonably well although some differences are found. The results show that the pulsed laser ablation method has potential to provide scalar measurement for mixing studies.     

Propagation of a gas jet in a liquid

Results are generalized from an experimental study of the dynamics of a gas jet in a liquid, the structure of the region of interaction, and the regimes of discharge from the submerged nozzle with different degrees of gas assimilation.     

Experimental study of a real gas jet

The author has experimentally investigated liquid jets propagating in a gas flow at mixing chamber pressures and temperatures of the components such that they may be assumed single-phase.     

Hydrodynamics of interaction of a gas jet and a liquid

The author investigates regimes of interaction between a liquid and jets of gas discharging from immersed nozzles, and the dimensions of the gas volumes generated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 4, pp. 550–558, October, 1984.     

Diffusion of inertial particles in a turbulent gas jet

An algorithm is proposed and a mathematical experiment is performed on the diffusion of high-density particles in a turbulent gas jet. The problem is solved with the impurity particle action on the carrier phase characteristics taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 3, pp. 367–375, September, 1989.     

Three-dimensional creep measurements in young concrete

Creep tests are reported in which sealed concrete specimens were loaded at the early age of 1 day and maintained under load for a further 61 days. Three systems of compressive stress were applied, uniaxial, equal biaxial and hydrostatic, all principal stresses being less than 50 percent of the uniaxial strength. It was found that Poisson's ratio for total strain (elastic+creep) remained sensibly constant throughout the test and was little affected by the system of loading. In general, the characteristics of creep and creep recovery under the multiaxial stress systems are the same as those observed in older concrete. A further test with stresses of 70–100 percent of the uniaxial strength resulted in increased unit strains, even under hydrostatic stress.     

Probe measurements in submerged rarefied plasma jet

A method for processing the results of probe experiments is developed for systems where a jet of rarefied plasma moves through a rarefied background plasma with comparable levels of charged particle concentrations in the jet and background. Results of a probe experiment with a submerged rarefied jet plasma efflux from a stationary plasma thruster are presented.     

Some velocity measurements in a swirling jet and a swirling flame with strong recirculation

The complete flow fields of a swirling jet and a swirling H₂ flame with strong recirculation including all Reynolds-stress tensor components are measured with a three component LDV system. The swirl jet with and without combustion have the same co-flow volume flow rate, momentum ratio, and similar swirl number. The exist profiles of both jets, which are important boundary conditions, are also provided. The main objective of the presented results is to supply a complete flow field data-base for development and assessment of numerical combustion models with focus on turbulence sub-models for flows with recirculation. M. Sc.T. C. Cheng; Dr.-Ing.E.P. Hassel and Prof. Dr.-Ing.J. Janicka, Fuchgebiet Energie- und Kraftwerkstechnik, TH Darmstadt     

Temperature measurements in a laminar plasma jet generated at reduced pressure

Double electrostatic probe method and Boltzmann-plot method are applied to measure the electron temperature and the excitation temperature of a DC laminar argon plasma jet generated at reduced pressure. Attempts are also made to measure the gas temperature by using a pair of WRe-5/26 thermocouple. Experimental results show that the measured excitation temperature at the jet center increases with the vacuum chamber pressure and the arc current, but is appreciably lower than the measured electron temperature, indicating that the plasma jet under study is evidently deviated from the LTE state. The temperature indicated by the thermocouple probe is much lower than the measured excitation temperature and electron temperature. Theoretical analysis shows that the thermocouple method intended for gas temperature measurement contains very large errors due to rarefied-gas heat transfer effects, and thus is unsuitable for this purpose.     

Temperature field and dynamics of a vertical gas jet in a fluidized bed

Experimental results are presented on the determination of the range of a jet and the boundaries of temperature variation of a fluidized bed in its vicinity.     

Gas distribution in a packed bed with jet gas injection

This article examines the distribution of gas flows in the vicinity of a jet entering a packed bed. A qualitative explanation of the character of particle motion around the cavity is given.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 1, pp. 10–15, January, 1987.     

Stopped-flow technique for transit time measurement in a gas jet

A “stopped-flow” technique for the measurement of transit time of reaction products in a gas jet is described. The method involved establishing the gas flow through the jet system when the reactor is operating steadily and allowing the pressure to reach equilibrium values. The gas flow is stopped by means of electrically operated valves. The transit-time measurement is achieved by opening the valves and initiating the multiscaling of total activity simultaneously. The value obtained agrees well with the transit time measured by pulsing the reactor. The “stopped-flow” technique allows on-line measurement of transit time in any gas jet system where the physical transportation time is the major component of the transit time. This technique is especially useful for systems installed in reactors which do not have pulsing capability.     

Flow of a thin film of a viscous liquid in a gas jet

An approximate formulation is considered for the steady-state wave flow of a thin film of viscous liquid subject to tangential frictional stresses at the boundary. Measurements have been made on the stability limit for droplet detachment, and it has been found that the detachment rate and fractional composition of the droplets are dependent on the boundary conditions.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 4, pp. 622–630, April, 1981.     

Accelerator internal target experiments using a supersonic gas jet

Internal gas jet targets allow a high degree of flexibility in the design of experiments to study beam-target interactions in circular accelerators. Ultra-thin targets in the range 1–100 ng/cm² can be produced at essentially any available beam energy. Since the beam passes through the target approximately 10⁵ times per second, the effective target thickness can be comparable to that of a typical thin foil. We have performed a number of experiments at both FNAL and the Brookhaven AGS utilizing mixed and pure gas jet targets to study proton-nucleus collisions. With thousands of hours of experience using a variety of pure and mixed gas targets, we have demonstrated that such a target facility is not only readily adapted to the physical constraints of the accelerator but also offers a wide choice of targets and detector array possibilities. In addition, a target normalization technique is presented utilizing p-p elastic scattering from the hydrogen component of the mixed gas targets.