This thesis provides a comparison of experimental rotordynamic coefficients for laminar, smooth bushing oil seals to theoretical predictions from XLLubeGT and XLAnSeal. The experimental results come from a new test rig developed at the Turbomachinery Laboratory at Texas A&M University. The two software programs were developed to predict the static and dynamic characteristics of seals. XLLubeGT is a Reynolds equation based program while XLAnSeal is based on a bulk-flow Navier- Stokes model that includes temporal and convective acceleration terms. XLAnSeal was used to predict the added-mass terms of the seals since XLLubeGT assumes those terms to be zero or negligible. The data used for input into the two seals code was the actual measured conditions from the test rig. As part of the input parameters, inlet inertia effects and thermal gradients along the seal were included. Both XLLubeGT and XLAnSeal have the capability to analyze straight bore seals with different inlet and outlet clearances – essentially a tapered seal – but seal expansion caused by the radial differential pressure across the seal bushing was not included. Theoretical and experimentally determined dynamic characteristics include stiffness, damping, inertia terms and Whirl Frequency Ratio (WFR). Seal static characteristics are also reported. They include: leakage, shaft center line loci and Reynolds numbers. Test conditions include three shaft speeds: 4000, 7000 and 10,000 rpm, three test pressures: 21, 45 and 69 bar [300, 650, and 1000 psi] and multiple eccentricities from 0.0 to 0.7. The results for the dynamic characteristics show good correlation of the experimental data to the theoretical values up to an eccentricity of about 0.5. At higher eccentricities, the theory generally under-predicts the dynamic characteristics. Inertia terms are greatly under-predicted. The results for the static characteristics also show good correlation to the experimental data, but they also have a tendency to be under-predicted at higher eccentricities.

Systematic parametric studies were performed to better understand seal-inlet rotordynamics. A CFD-perturbation model was employed to compute the seal-inlet flow disturbance quantities. Seal inlet disturbance boundary condition correlations were proposed from the computed seal-inlet quantities using the important parameters. It was found that the cosine component of the seal-inlet swirl velocity disturbance W1C has a substantial impact on the cross-coupled stiffness, and that the correlations for W1C and W1S should be used to replace the historical guess that seal inlet W1C = 0 and W1S = 0. Also, an extremely precise relationship was found between the swirl disturbance W1C and the seal-inlet swirl velocity (ωRsh − ¯W0). Thus, the number of experiments or computer runs needed to determine the effect of spin speed, shaft radius and/or inlet swirl velocity on the cross-coupled stiffness is greatly reduced by plotting the simplified relationship of the cross-coupled stiffness against the swirl slip velocity. The benefits of using the new seal-inlet boundary condition correlations were assessed by implementing them into a CFD-perturbation model. Consistently improved agreement with measurements was obtained for both liquid annular seals and gas labyrinth seals. Further, the well-established CFD-perturbation model with new boundary condition correlations was employed to investigate the rotordynamics of two off-design situations. The first case considered the influence of labyrinth seal teeth damage on the performance and the rotordynamic characteristics of impeller eye seals in centrifugal compressors. The second case considered the influence of rotor-axial-shifting on rotordynamic forces for high-low labyrinth seals in steam turbines during the start-up and shut-down process. The results should provide useful information for labyrinth seal design and fault diagnosis of stability problems in turbines and compressors.

Phocid seals (true seals, Order Carnivora, Family Phocidae) use a diverse array of breeding habitats and strategies, and produce many vocalizations. Therefore, phocids are well suited as subjects for study of reproductive strategies and the role of vocalizations in species mating at sea. However, the amount of information is still limited for aquatically breeding pinnipeds. Using underwater audio and video recordings of Weddell seals (Leptonychotes weddellii) interacting in McMurdo Sound, I compared the frequencies of vocalizations and behaviors of males and females during the mating season. I also investigated differences in these frequencies based on the social context. Finally, I identified patterns of vocalizations and behaviors to help determine the behavioral context of calls and used this information as a basis for considering the degree of ritualization in Weddell seal displays. Mews, growls, knocks, and trills were found to be almost exclusively male-specific. The territorial male produced chirps more often when another male was present in its territory; whereas, mews and growls were more frequent when one or more free-ranging females were present. Several vocal and behavioral padeparture of the territorial male into or from the breathing hole. In the context of an evolutionary-based model of communication, these findings suggest that low-frequency vocalizations and stereotyped displays produced by territorial males may have been favored by sexual selection: they may provide reliable information to females about the fitness of the signaler and influence their choice of mate. They may also help in limiting conflicts between the territorial male and females over access to the breathing hole.

The effects of habitat features on the distribution of ringed seals (Phoca hispada) in the fast ice of Barrow Strait were examined between March and June 1984 to 1986. Breathing hole density in thirty-two, 2-4 km$ sp2$ study plots provided an index of seal abundance. Densities of seal holes were determined using a combination of trained dogs to locate the subnivean breathing holes and removal sampling. / Birth lairs were not seen before 4 April, but the incidence of these structures increased as the season progressed. Structures maintained by male seals were evident in late March, but were not found after mid-May. In 1984, densities of seal holes were correlated with ice thickness. In 1985, no relationship was detected between seal hole density and habitat. In 1986, the highest densities of subnivean structures including birth lairs, were associated with deep snow conditions located in areas of late consolidating ice. No relationship was identified between the density of male structures and any habitat variables. / The mean reproductive rate for females $>$7 years old was 0.64. Between March and June for adult males lost 204 g per day with 72% of this weight being lost from blubber. Pregnant females lost 467 g per day with 68% of the loss occurring from the blubber. In adult seals no differences in body condition were detected between sexes or between years, but juveniles collected in 1986 were in significantly better condition than juveniles collected in 1984 and 1985.

No description available.

Within pressurised Metered Dose Inhalers (pMDIs) the contact between the valve components and elastomeric seals is of major significance, representing the main contributory factor to the overall system frictional characteristics. Therefore, the seal performance is extremely important and must be optimised to meet the contradictory requirements of preventing leakage and allowing smooth actuation. The environmentally driven trend to HFA formulations as opposed to CFC based ones has deteriorated this problem due to poor lubrication conditions and it has, consequently, increased the frictional losses during the pMDI actuation (hysteresis cycle). Research has been conducted into the key areas of the inhaler mechanism. As such, the contact pressure distribution and resulting reactions have been investigated, with emphasis on the correct treatment of the elastomer (seal) characteristics. The modelling of the device has been conducted within the environment of the multibody dynamics commercial software ADAMS, where a virtual prototype has been built using solid CAD geometries of the valve components. An equation was extrapolated to describe the relation between the characteristics of the ultra thin film contact conditions (sliding velocity, surface geometry, film thickness and reaction force) encountered within the inhaler valve and integrated into the virtual prototype allowing the calculation of friction within the conjuncture (due to viscous shear and adhesion). The latter allowed the analysis and optimisation of key device parameters, such as seal geometry, lubricant properties etc. It has been concluded that the dominant mechanism of friction is adhesion, while boundary lubrication is the prevailing lubrication regime due to the poor surface roughness to film thickness ratio. The multibody dynamics model represents a novel multi physics approach to study the behaviour of pMDIs, including rigid body inertial dynamics, general elasticity, surface interactions (such as adhesion), hydrodynamics and intermolecular surface interactions (such as Van der Waals forces). Good agreement has been obtained against experimental results at component and device level.

Doctor of Philosophy(PhD) / Communication is a fundamental process that allows animals to effectively transfer information between groups or individuals. Recognition plays an essential role in permitting animals to distinguish individuals based upon both communicatory and non-communicatory signals allowing animals to direct suitable behaviours towards them. Several modes of recognition exist and in colonial breeding animals which congregate in large numbers, acoustic signalling is thought to be the most effective as it suffers less from environmental degradation. Otariid seals (fur seals and sea lions) are generally colonial breeding species which congregate at high densities on offshore islands. In contrast to the other Arctocephaline species, the Australian fur seal, Arctocephalus pusillus doriferus, along with its conspecific, the Cape fur seal, A. p. pusillus, display many of the behavioural traits of sea lions. This may have important consequences in terms of its social structure and evolution. The acoustic communication of Australian fur seals was studied on Kanowna Island, Bass Strait, Australia. Analysing the acoustic structure of vocalisations and their use facilitates our understanding of the social function of calls in animal communication. The vocal repertoires of males, females, pups and yearlings were characterised and their behavioural context examined. Call structural variations in males were evident with changes in behavioural context, indicating parallel changes in the emotive state of sender. For a call to be used in vocal recognition it must display stereotypy within callers and variation between them. In Australian fur seal females and pups, individuals were found to have unique calls. Mutual mother-pup recognition has been suggested for otariids and this study supports the potential for this process to occur through the use of vocalisations. Call structural changes in pup vocalisations were also investigated over the progression of the year, from birth to weaning. Vocalisations produced by pups increased in duration, lowered in both the number of parts per call and the harmonic band containing the maximum frequency as they became older, suggesting calls are changing constantly as pups grow toward maturity. It has been suggested through descriptive reports, that the bark call produced by males is important to vocal recognition. The present study quantified this through the analysis of vocalisations produced by male Australian fur seals. Results support descriptive evidence suggesting that male barks can be used to discriminate callers. Traditional playback studies further confirmed that territorial male Australian fur seals respond significantly more to the calls of strangers than to those of neighbours, supporting male vocal recognition. This study modified call features of the bark to determine the importance to vocal recognition. The results indicate that the whole frequency spectrum was important to recognition. There was also an increase in response from males when they heard more bark units, indicating the importance of repetition by a caller. Recognition occurred when males heard between 25-75% of each bark unit, indicating that the whole duration of each bark unit is not necessary for recognition to occur. This may have particular advantages for communication in acoustically complex breeding environments, where parts of calls may be degraded by the environment. The present study examined the life history characteristics of otariids to determine the factors likely to influence and shape its vocal behaviour. Preliminary results indicate that female density, body size and the breeding environment all influence the vocal behaviour of otariids, while duration of lactation and the degree of polygyny do not appear to be influential. Understanding these interactions may help elucidate how vocal recognition and communication have evolved in different pinniped species.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Michigan, 1933. / Includes bibliographical references (p. xv-xvii) and index.

Thesis (Ph. D.)--University of Michigan, 1933. / Includes bibliographical references (p. xv-xvii) and index.