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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenTue, 16 Apr 2024 15:50:24 +0000An Experimental and Theoretical Investigation of Two-Dimensional Centrifugal Pump Impellers
https://resolver.caltech.edu/CaltechETD:etd-04072003-091659
Authors: {'items': [{'id': 'Acosta-Allan-James', 'name': {'family': 'Acosta', 'given': 'Allan James'}, 'show_email': 'NO'}]}
Year: 1952
DOI: 10.7907/159P-SA35
<p>An experimental and theoretical investigation on a series of three centrifugal pump impellers has been made in order to determine the usefulness and validity of tyro-dimensional potential theory for the description of the flow. Computed values of the developed head and distribution of pressure on the vane surfaces are compared with measurements an two-, four-, and six- bladed impellers which have 30° logarithmic spiral vanes and a radius ratio of about one-half.</p>
<p>It is found that for operating points where the influence on the flow into the impeller by the inlet turn is least, the agreement between the observed and predicted values is reasonably good, while for other flow rates large discrepancies occur. Although the impeller efficiency is relatively high when the flow is least disturbed by the inlet, the slope of the work coefficient line is steeper than the theoretically predicted value. This deviation is attributed to boundary layers which are observed on the vane surfaces.</p>https://thesis.library.caltech.edu/id/eprint/1282Flow Generated by Suddenly Heated Flat Plate
https://resolver.caltech.edu/CaltechETD:etd-10052004-163535
Authors: {'items': [{'email': 'susanwu5@comcast.net', 'id': 'Wu-Ying-Chu-Lin-Susan', 'name': {'family': 'Wu', 'given': 'Ying-Chu Lin Susan'}, 'show_email': 'NO'}]}
Year: 1963
DOI: 10.7907/CPQD-RQ29
<p>By employing the two-sided Maxwellian in Maxwell's moment method a kinetic theory description is obtained of the flow generated by a step-function increase in the temperature of an infinite flat plate. Four moments are employed in order to satisfy the three conservation equations, plus one additional equation involving the heat flux in the direction normal to the plate. For a small temperature rise the equations are linearized, and closed-form solutions are obtained for small and large time in terms of the average collision time.</p>
<p>Initially the disturbances propagate along two distinct characteristics, but the discontinuities across these waves damp out as time increases. At large time the main disturbance propagates with the isentropic sound speed. Solutions for mean normal velocity and temperature show the transition from the nearly collision-free regime to the Navier-Stokes-Fourier regime, which is characterized by a boundary layer near the plate surface merging into a diffuse "wave". The classical continuum equations, plus a temperature jump boundary condition, seem to be perfectly adequate to describe the flow beyond a few collision times, provided one accounts properly for the interaction between the inner thermal layer and the outer diffuse wave.</p>https://thesis.library.caltech.edu/id/eprint/3925A study of CsCl type intermediate phases involving rare earth elements
https://resolver.caltech.edu/CaltechETD:etd-09112002-171500
Authors: {'items': [{'id': 'Chao-Chang-Chih', 'name': {'family': 'Chao', 'given': 'Chang-Chih'}, 'show_email': 'NO'}]}
Year: 1965
DOI: 10.7907/EKPF-2Q83
This thesis presents the results of a systematic study of CsCl type phases in binary alloys of rare earth elements with other metals. Thirty-nine new phases of this type have been found. The linear variation of the lattice parameter of CsCl phases with the trivalent ionic radius of the rare earth metal previously established for a limited number of alloys, has been extended to seventy-nine phases. This linear relationship leads to some interesting qualitative arguments on the ionic size of the non-rare earth element in these phases. The electrical resistivities of nineteen CsCl type phases of rare earths with copper, silver and gold were measured between 4.2 [degrees] K and about 260 [degrees] K. With the exception of the yttrium-silver phase, all others exhibited an anomaly in the resistivity-temperature curve which is attributed to an antiferromagnetic transition. This conclusion is confirmed by previously published results of neutron diffraction experiments and magnetic susceptibility measurements. A qualitative interpretation of the resistivity results based on the indirect exchange interaction between the ions of the same type (magnetic or non-magnetic) and between the ions of the different type (magnetic and non-magnetic) is proposed.https://thesis.library.caltech.edu/id/eprint/3451Viscous and nonlinear effects in the oscillations of drops and bubbles
https://resolver.caltech.edu/CaltechETD:etd-11072006-111631
Authors: {'items': [{'email': 'prosperetti@jhu.edu', 'id': 'Prosperetti-A', 'name': {'family': 'Prosperetti', 'given': 'Andrea'}, 'show_email': 'YES'}]}
Year: 1974
DOI: 10.7907/FRDP-DV27
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
The thesis is divided into three parts. In Part I the nonlinear oscillations of a spherical gas bubble in an incompressible, viscous liquid are investigated analytically by means of an asymptotic method. The effect of surface tension is included, and it is shown that thermal and acoustic damping can be accounted for by the suitable redefinition of one parameter. Approximate analytical solutions for the steady state oscillations are presented for the fundamental mode as well as for the first and second subharmonic and for the first and second harmonic. The transient behaviour is also briefly considered. The first subharmonic is studied in particular detail, and a new explanation of its connection with acoustic cavitation is proposed. The approximate analytical results are compared with some numerical ones and a good agreement is found.
In Part II the characteristics of subharmonic and ultraharmonic modes appearing in the forced, steady state oscillations of weakly nonlinear systems are considered from the physical, rather than mathematical, viewpoint. A simple explanation of the differences between the two modes, and in particular of the threshold effect usually exhibited by subharmonic oscillations, is presented. The principal resonance in the case of weak excitation is also briefly considered.
Finally, in Part III the problem of two viscous, incompressible fluids separated by a nearly spherical free surface is considered in general terms as an initial value problem to first order in the perturbation of the spherical symmetry. As an example of the applications of the theory, the free oscillations of a viscous drop are studied in some detail. In particular, it is shown that the normal mode analysis of this problem available in the literature does not furnish a solution correct for all times, but only an asymptotic one valid as [...].https://thesis.library.caltech.edu/id/eprint/4443Extension of Rayleigh-Taylor Instability Theory with Applications
https://resolver.caltech.edu/CaltechTHESIS:02032021-213518907
Authors: {'items': [{'id': 'Whipple-Christopher-George', 'name': {'family': 'Whipple', 'given': 'Christopher George'}, 'show_email': 'NO'}]}
Year: 1974
DOI: 10.7907/5bc3-w217
<p>A theoretical derivation is presented for interfacial waves, both stable and unstable, which includes viscosity and surface tension. This result is extended to the case where one fluid has a finite thickness and is bounded by a rigid boundary or a free surface. As these solutions present formidable algebraic difficulties, approximate forms of solutions, which are motivated by physical arguments, are also given, and, through the use of a computer, the full theoretical result is shown to be fairly accurately reproduced by these approximations. The theory is used to give an explanation of the bioconvection patterns which have been observed with cultures of microorganisms which have negative geotaxis. Since such organisms tend to collect at the surface of a culture and since they are heavier than the culture medium the conditions for Rayleigh-Taylor instability are met. It is shown that the observed patterns are quite accurately explained by the theory. Similar observations with a viscous liquid loaded with small glass spheres are described. A behavior similar to the bioconvective patterns with microorganisms is found and the results are also explained quantitatively by Rayleigh-Taylor instability theory with viscosity. Further physical considerations of the bioconvection demonstrate the validity of the Rayleigh-Taylor instability model, and describe the steady state circulation of microorganisms. An approximate solution to a viscous fluid of finite depth with an exponential density gradient is developed, and the applicability of this result to certain bioconvective situations is discussed.</p>https://thesis.library.caltech.edu/id/eprint/14075I. Experimental observations of the microlayer in vapor bubble growth on a heated solid. II. An investigation of the theory of evaporation and condensation
https://resolver.caltech.edu/CaltechETD:etd-12082006-131228
Authors: {'items': [{'email': 'larry.koffman@srnl.doe.gov', 'id': 'Koffman-L-D', 'name': {'family': 'Koffman', 'given': 'Larry Douglas'}, 'show_email': 'NO'}]}
Year: 1980
DOI: 10.7907/M1H1-S690
Two fundamental problems related to the evaporation of the microlayer formed beneath growing vapor bubbles on a solid surface are investigated. First, experimental measurements of microlayer formation and evaporation have been obtained for nucleate boiling of water and ethanol using laser interferometry combined with high speed photography. For pool boiling of water at atmospheric pressure with low subcooling, the initial microlayer profile is wedge-like with a thickness of 1.85 µm at a radius of 0.25 mm; the thickness for ethanol is approximately 1.6 times that for water. The measured evaporation rates from the microlayer correspond to local heat fluxes of the order of 1000 kW/m2 over the bubble lifetime. The measurement technique of laser interferometry is discussed in detail with emphasis on the difficulties encountered in interpretation of the fringe patterns. In the second investigation, the theory of evaporation and condensation is considered from a kinetic theory approach. The moment method of Lees is used to solve the problem of the flow of vapor between a hot liquid surface and a cold liquid surface. A result of the theory is that the temperature profile in the vapor for the continuum problem is inverted from what would seem physically reasonable. Because of this behavior, the theory is questioned on physical grounds leading to the conclusion that the usually assumed boundary conditions for emission of molecules from a liquid surface are probably incorrect.https://thesis.library.caltech.edu/id/eprint/4869