- Email: [email protected]
Tomographic method for the reconstruction of local probability density functions
170 Abstracts for The 3rd World Conference concern is the location relative to the TDR probes of air-filled gaps in otherwise integral materials. The transmission line equations were the basis of this analysis. Results show the effect of gap location on the TDR indication.
Tomographic Method for the Reconstruction of Local Probability Density Functions Y. R. Sivathanu J. P. Gore
School of Mechanical Engineering Purdue University W. Lafayette, Indiana Experimental studies of the emission and the absorption properties of turbulent flames involve two major difficulties: (1) nonintrusive measurements yield path-integrated data while improved understanding of physical processes requires information concerning local properties, and (2) intrusive measurements of local properties are possible only in optically thick flames. In the present paper, a novel method of obtaining the probability density function (PDF) of local properties from path-integrated measurements is described. The approach uses the discrete probability function method to infer the PDF of the local transmittance from measurements of the PDFs of the path-integrated transmittance. The local PDFs obtained using the method are compared with those obtained from direct intrusive measurements of local PDFs in propylene/air and ethylene/air diffusion flames. The results of this comparison are very encouraging.
Assessment of Ultrasonics to Infer Moisture Content in Unsaturated Media S. Thota R. F. Boehm
Department of Mechanical Engineering University of Nevada Las Vegas, Nevada The work reported here was designed to evaluate the possibility of using commercially available ultrasonic systems as tools in determining the degree of saturation in unsaturated flows in laboratory studies of geological materials. Experiments were conducted to determine the dependence of elastic wave velocities and amplitudes on the amount of moisture present in simulant systems of moist sand as well as layered ceramic tiles. Compressional wave velocity V and amplitude were measured in transmission studies at a frequency of 0.5 MHz. During the experiment with a sand-water system, V showed no variation as the level of saturation of the moisture varied, except for a slight increase in the velocity at a very high degree of saturation. With tile-water systems, the velocity changed considerably as the gaps between the tiles were filled with water. A simple theoretical model has been developed to estimate velocities and transmitted amplitudes through the tile system, and calculations from this model are compared to the experimental data.
Novel Phenomena, Sensors, and Applications Multiposition Hot-Wire Technique for the Study of Swirling Flows in Vortex Chambers A. Fitouri M. K. Khan H. H. Bruun
Department of Mechanical and Manufacturing Engineering University of Bradford Bradford, England This paper describes a multiposition single-slant hot-wire probe technique for the study of a three-dimensional confined vortex flow. Most of the previously reported observations of confined swirling flows have been obtained by flow visualization or by using relatively large pressure probes. However, swirling flows are extremely sensitive to probe disturbances created by such probes. In addition, when such probes are used in turbulent flows, they are subject to errors caused by turbulent fluctuations. Due to these difficulties, more recent measurements have been made with hot-wire anemometers. The hot-wire probes have the advantage of small size, which causes minimal disturbance to the flow, coupled with a good signal sensitivity and a high-frequency response, which enable the study of the occurring turbulence field. General response equations have been developed between Veff and v 2etf (the mean and fluctuating effective velocities, respectwely). The corresponding derivation of the three main velocity components and six Reynolds stresses was carried out. Velocity and turbulence intensity measurements were taken and are presented (using the derived equations) for different exit conditions. These results demonstrate an extreme sensitivity of the flow regime to the exit conditions.
An Accurate Electrical Probe for Plasma Diagnosis and Simulation of Time-Dependent Sheath Characteristics Seizo Kato Naoki Maruyama Takashi Suzuki Kazuyoshi Hoshino
Department of Mechanical Engineering Mie University Kamihama-cho, Tsu, Mie, Japan A new plasma diagnostic scheme is proposed to determine correct plasma parameters using Langmuir electrical probes and taking the time-dependent sheath characteristics into account. The sawtooth voltage from an external signal generator to provide the periodic voltage ramp that biases the probe is used, and the probe current-voltage curves are obtained at two high- and low-impressed voltage rates defined as the ratio of the probe bias voltage swing to its time period. The scheme encompasses the determination of the plasma potential and saturation electron current from the intersection point of the two curves obtained and the estimation of the electron temperature and density from the curve obtained at the low optimum
Tomographic Method for the Reconstruction of Local Probability Density Functions Y. R. Sivathanu J. P. Gore
School of Mechanical Engineering Purdue University W. Lafayette, Indiana Experimental studies of the emission and the absorption properties of turbulent flames involve two major difficulties: (1) nonintrusive measurements yield path-integrated data while improved understanding of physical processes requires information concerning local properties, and (2) intrusive measurements of local properties are possible only in optically thick flames. In the present paper, a novel method of obtaining the probability density function (PDF) of local properties from path-integrated measurements is described. The approach uses the discrete probability function method to infer the PDF of the local transmittance from measurements of the PDFs of the path-integrated transmittance. The local PDFs obtained using the method are compared with those obtained from direct intrusive measurements of local PDFs in propylene/air and ethylene/air diffusion flames. The results of this comparison are very encouraging.
Assessment of Ultrasonics to Infer Moisture Content in Unsaturated Media S. Thota R. F. Boehm
Department of Mechanical Engineering University of Nevada Las Vegas, Nevada The work reported here was designed to evaluate the possibility of using commercially available ultrasonic systems as tools in determining the degree of saturation in unsaturated flows in laboratory studies of geological materials. Experiments were conducted to determine the dependence of elastic wave velocities and amplitudes on the amount of moisture present in simulant systems of moist sand as well as layered ceramic tiles. Compressional wave velocity V and amplitude were measured in transmission studies at a frequency of 0.5 MHz. During the experiment with a sand-water system, V showed no variation as the level of saturation of the moisture varied, except for a slight increase in the velocity at a very high degree of saturation. With tile-water systems, the velocity changed considerably as the gaps between the tiles were filled with water. A simple theoretical model has been developed to estimate velocities and transmitted amplitudes through the tile system, and calculations from this model are compared to the experimental data.
Novel Phenomena, Sensors, and Applications Multiposition Hot-Wire Technique for the Study of Swirling Flows in Vortex Chambers A. Fitouri M. K. Khan H. H. Bruun
Department of Mechanical and Manufacturing Engineering University of Bradford Bradford, England This paper describes a multiposition single-slant hot-wire probe technique for the study of a three-dimensional confined vortex flow. Most of the previously reported observations of confined swirling flows have been obtained by flow visualization or by using relatively large pressure probes. However, swirling flows are extremely sensitive to probe disturbances created by such probes. In addition, when such probes are used in turbulent flows, they are subject to errors caused by turbulent fluctuations. Due to these difficulties, more recent measurements have been made with hot-wire anemometers. The hot-wire probes have the advantage of small size, which causes minimal disturbance to the flow, coupled with a good signal sensitivity and a high-frequency response, which enable the study of the occurring turbulence field. General response equations have been developed between Veff and v 2etf (the mean and fluctuating effective velocities, respectwely). The corresponding derivation of the three main velocity components and six Reynolds stresses was carried out. Velocity and turbulence intensity measurements were taken and are presented (using the derived equations) for different exit conditions. These results demonstrate an extreme sensitivity of the flow regime to the exit conditions.
An Accurate Electrical Probe for Plasma Diagnosis and Simulation of Time-Dependent Sheath Characteristics Seizo Kato Naoki Maruyama Takashi Suzuki Kazuyoshi Hoshino
Department of Mechanical Engineering Mie University Kamihama-cho, Tsu, Mie, Japan A new plasma diagnostic scheme is proposed to determine correct plasma parameters using Langmuir electrical probes and taking the time-dependent sheath characteristics into account. The sawtooth voltage from an external signal generator to provide the periodic voltage ramp that biases the probe is used, and the probe current-voltage curves are obtained at two high- and low-impressed voltage rates defined as the ratio of the probe bias voltage swing to its time period. The scheme encompasses the determination of the plasma potential and saturation electron current from the intersection point of the two curves obtained and the estimation of the electron temperature and density from the curve obtained at the low optimum