No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

The development of a novel combined 'ultrasonic/thermal' with 'ultrasonic multiple reflections' clamp-on meter for measuring a wide flowrate range of clean liquids in small diameter pipes is presented. Current existing flowmeters based on ultrasound cannot measure very low flowrates for single phase liquids. The ultrasonic/thermal technique can measure single phase flows in the range 0 to 0.6 m s⁻¹ in pipes with diameters as small as 15 mm. It can also detect and measure reverse flows. The minimum flowrate for the ultrasonic multiple reflection technique is about 0.55 m s⁻¹, and theoretically, the measurement accuracy increases with increased flow velocity. The ultrasonic/thermal technique is based on a heating element and transducer pair(s) which can be clamped to the outside of a pipe. With the heaters switched on, the changes in the temperature of the pipe and the liquid inside it result in changes in transit time. The flowrate can be therefore estimated by either the transit time difference across the pipe at the two symmetric locations with respect to the heater centre, or at one location with a heater off/on comparison. The latter approach was felt to be the promising for low flowrate measurements and therefore selected for the numerical and the experimental investigations. The multiple reflection technique was developed based on the conventional transit time flowmeter. This technique extended the measuring range of the flowmeter and provided cross calibration for the ultrasonic/thermal technique. A computer model was developed for the ultrasonic multiple reflection technique. However, there was insufficient experimental data to confirm the computer prediction. Results from computational fluid dynamics (CFD) analysis of the meter are presented. For vertical pipes an axisymmetric model was used, but the presence of buoyancy forces required the use of a 3-D model for horizontal pipes. Temperature and velocity distributions and ultrasonic transit times have been computed and are presented. In order to overcome the problem of mode conversion and refraction at the pipe wall/transducer mounting interface, novel transducers and mounting blocks are presented. A prototype heater and ultrasonic transducer system together with electronics for signal generation and transit time measurement have been designed and constructed. A hydraulic system has also been designed and constructed for testing the developed clamp-on flowmeter. Experimental results from this apparatus are presented and compared with the CFD predictions, and a technique for compensating for variations in inlet temperature is described. The full scale difference between the computed values and experimental results of the meter for low flowrate measurement was about 3.5%.

No description available.

Starting from the dynamic equations of electromagnetics we derive mutual impedance formulas that include the effects of induced polarization (IP) and electromagnetic (EM) coupling. The mutual impedance formulas are given for four geometries: a fullspace, a cylinder in a fullspace, a halfspace, and a layer over a halfspace. IP effects are characterized by a Cole-Cole model, the properties of which are fully investigated. From the general mutual impedance formulas specific limiting forms are defined to characterize the IP and EM effects. Using these limiting forms a framework is developed to justify the addition or multiplication of the two effects. The additive and multiplicative models are compared in the cylinder and layer geometries with the conclusion that the additive model proves to be more accurate over a wider range of frequencies than the multiplicative model. The nature of the IP and EM effects is illustrated in all four geometries showing the effects of relevant parameters. In all cases it is shown that the real part of the mutual impedance contains important IP information that is less influenced by EM effects. Finally the effects of boundaries are illustrated by the cylinder and layer geometries and a theory is developed to incorporate EM effects and IP effects from multiple regions which utilizes frequency dependent real dilution factors. We also include a brief review of some EM "removal" schemes and dilution theory approximations.

This dissertation investigates a method for extending the measurement range of an optical surface profiling instrument. The instrument examined in these experiments is a computer-controlled phase-modulated interference microscope. Because of its ability to measure surfaces with a high degree of vertical resolution as well as excellent lateral resolution, this instrument is one of the most favorable candidates for determining the microtopography of optical surfaces. However, the data acquired by the instrument are restricted to a finite lateral and vertical range. To overcome this restriction, the feasibility of a new testing technique is explored. By overlapping a series of collinear profiles the limited field of view of this instrument can be increased and profiles that contain longer surface wavelengths can be examined. This dissertation also presents a method to augment both the vertical and horizontal dynamic range of the surface profiler by combining multiple subapertures and two-wavelength techniques. The theory, algorithms, error sources, and limitations encountered when concatenating a number of profiles are presented. In particular, the effects of accumulated piston and tilt errors on a measurement are explored. Some practical considerations for implementation and integration into an existing system are presented. Experimental findings and results of Monte Carlo simulations are also studied to explain the effects of random noise, lateral position errors, and defocus across the CCD array on measurement results. These results indicate the extent to which the field of view of the profiler may be augmented. A review of current methods of measuring surface topography is included, to provide for a more coherent text, along with a summary of pertinent measurement parameters for surface characterization. This work concludes with recommendations for future work that would make subaperture-testing techniques more reliable for measuring the microsurface structure of a material over an extended region.