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The purpose of these studies was to measure the drag coefficient of a small model submarine to add data to a Reynolds number study. First, a laser Doppler velocimeter (LDV) was used to measure the flow characteristics of the Mississippi State University water tunnel. The velocity and turbulence intensity profiles were measured for a range of freestream velocities of 8.6 m/s to 10.7 m/s. Several wake velocity profiles were taken for a model submarine at downstream distances of x/d = 10 to x/d = 28, with a freestream velocity of 8.6 m/s. A formula for the drag coefficient that uses only mean velocity measurements in the wake was derived for an axisymmetric body using the assumptions of a self-similar wake and a power law behavior of the wake scales. The experimental drag coefficient results are compared to computational fluid dynamic (CFD) solutions.

Submitted by Dilene Paulo (dilene.fatima@ufcg.edu.br) on 2018-02-07T14:27:21Z No. of bitstreams: 1 WALDEMIR SOARES DA COSTA – TESE PPGEP 2015.pdf: 7105919 bytes, checksum: 23f299de189a3af192ed30f53d82a776 (MD5) / Made available in DSpace on 2018-02-07T14:27:21Z (GMT). No. of bitstreams: 1 WALDEMIR SOARES DA COSTA – TESE PPGEP 2015.pdf: 7105919 bytes, checksum: 23f299de189a3af192ed30f53d82a776 (MD5) Previous issue date: 2015-07-17 / Este trabalho tem como objetivo estudar o comportamento da transferência de calor em polpa de jaca acondicionada em recipiente cilíndrico. O estudo apresenta a solução para a equação de difusão com condição de contorno de primeiro tipo variável. Foi desenvolvida uma modelagem físico-matemática para solução de um problema direto de difusão de calor bidimensional, no interior de um recipiente cilíndrico contendo polpa de jaca. O método dos volumes finitos com formulação totalmente implícita foi usado para resolver o problema direto e, por conseguinte, determinar a distribuição de temperatura. O meio pastoso, homogêneo e isotrópico, foi considerado estacionário e, assim, eventuais trocas convectivas e radioativas no interior do meio foram negligenciadas. Dois softwares em Fortran foram desenvolvidos visando, primeiro, à solução do problema de estimativa da difusividade térmica utilizando-se, como função objetivo, o qui-quadrado e o outro para a solução do problema direto. Conjuntamente, foi usado um aparato experimental para a análise inversa (problema inverso). O sistema físico experimental consistiu de dois recipientes cilíndricos de alumínio de dimensões diferentes, que foram preenchidos com polpa de jaca para a qual se estimou a difusividade térmica. Dois termopares conectados a um termômetro digital de dois canais mediram as temperaturas no centro e na interface entre a polpa e o recipiente. As medidas foram enviadas a um computador via RS-232 e salvas em arquivo, através do software Data logger. No que concerne ao problema direto, um modelo de condução de calor bidimensional, com simetria radial e axial, foi usado para obter a resposta transiente das temperaturas medidas no centro e no contorno do cilindro. Quando comparados aos valores da literatura, os resultados obtidos se mostraram coerentes, ou seja, o software desenvolvido neste trabalho pode ser considerado válido, sendo que este pode ser utilizado para outras simulações. Mostraram, também, que a solução proposta representa satisfatoriamente o processo de tratamento térmico de polpa de jaca acondicionada em embalagens cilíndricas proporcionando segurança alimentar com um menor custo de energia. Conhecida a difusividade térmica em função da temperatura local, é possível precisar o tempo adequado de tratamento térmico, tornando desnecessária a realização de experimentos a cada vez que um novo recipiente cilíndrico for utilizado para armazenar o produto. / This work aims to study the heat transfer behavior in jackfruit pulp packed in cylindrical container. The study presents the solution to the diffusion equation type boundary condition for first variable. A physical-mathematical model for solving the problem of a direct two-dimensional diffusion of heat in the interior of a cylindrical container containing jackfruit pulp has been developed. The finite volume method with fully implicit formulation was used to solve the direct problem and therefore, determine the temperature distribution. The medium viscous, homogeneous and isotropic, was considered stationary and thus any radioactive and convective exchanges within the medium they were neglected. Two software in Fortran were developed first to find the solution of the estimated thermal diffusivity problem using as objective function, the chi-square and also for solving the direct problem it self. Together, an experimental apparatus was used to analyze the reverse (inverse problem). The experimental physical system consisted of using two cylindrical aluminum containers of different dimensions, which were filled with jackfruit pulp for which the thermal diffusivity is estimated. Two thermocouples connected to a digital two channel thermometer measured temperatures at the center and at the interface between the pulp and the container. The measures were sent to a computer via RS-232 and saved in a file, through the Data Logger software. Concerning to the direct problem a two-dimensional heat conduction model with radial and axial symmetry it has been used for the transient response of the measured temperatures at the center and the cylinder contour. Compared to literature values, the results obtained were consistent, so, the software developed in this work can be considered valid and this can be used for other simulations the results. Also showed that the proposed solution represents satisfactorily the heat treatment process of wrapped jackfruit pulp in cylindrical packaging providing food security with a lower energy cost. As we know the thermal diffusivity an depending on the local temperature is possible to determine the timing of heat treatment, making it unnecessary to perform experiments each time a new cylindrical container is used to store the product.

This thesis contains solutions to chosen problems of applied mathematics. It comprises examples related to geometrical applications of the double and triple integrals´ theory, ie calculation methods of areas, volumes, mass and coordinates of gravity centres. Each problem´s solution is described in detail and supplemented with a picture. The problems are arranged according to complexity.

The semiconducting compounds CdTe and CdZnTe have important applications in high-energy radiation detectors and as substrates for infrared devices. The materials offer large band gaps, high resistivity, and excellent charge transport properties; however all of these properties rely on very precise control of the material composition. Growing bulk crystals by the travelling heater method (THM) offers excellent compositional control and fewer defects compared to gradient freezing, but it is also much slower and more expensive. A particular challenge is the current need to grow new crystals onto existing seeds of similar size and quality. Simulations and experiments are used in this work to investigate the feasibility of growing these materials by THM without the use of large seed crystals. A new fixed-grid, multiphase finite element model was developed based on the level set method and used to calculate the mass transport regime and interface shapes inside the growth ampoule. The diffusivity of CdTe in liquid tellurium was measured through dissolution experiments, which also served to validate the model. Simulations of tapered THM growth find conditions similar to untapered growth with interface shapes that are sensitive to strong thermosolutal convection. Favourable growth conditions are achievable only if convection can be controlled. In preliminary experiments, tapered GaSb crystals were successfully grown by THM and large CdTe grains were produced by gradient freezing. Beginning with this seed material, 25 mm diameter CdTe and CdZnTe crystals were grown on 10 mm diameter seeds, and 65 mm diameter CdTe on 25 mm seeds. Unseeded THM growth was also investigated, as well as ampoule rotation and a range of thermal conditions and ampoule surface coatings. Outward growth beyond one or two centimeters was achieved only at small diameters and included secondary grains and twin defects; however, limited outward growth of larger seeds and agreement between experimental and numerical results suggest that tapered growth may be achievable in the future. This would require active temperature control at the base of the crystal and reduction of convection through thermal design or by rotation of the ampoule or applied magnetic fields. / Graduate / 0346 / 0794 / 0548 / jordan.roszmann@gmail.com

Ziel der vorliegenden Arbeit ist es, Rühr- und Mischungsvorgänge in Flüssigmetallströmungen zu untersuchen, die mittels rotierender und wandernder Magnetfelder bzw. deren Kombination induziert werden. Im Mittelpunkt steht dabei die Charakterisierung der dreidimensionalen Strömungsstrukturen innerhalb zylindrischer Geometrien bei der Verwendung überkritischer Magnetfelder. Neben der Untersuchung der Strömungseigenschaften stellen die physikalische Modellierung der angreifenden Kräfte, die geeignete Wahl und Validierung eines effizienten numerischen Lösungsverfahrens und dessen Erweiterung für die Durchführung von Large Eddy Simulationen wesentliche Eckpfeiler dieser Arbeit dar.

In this report, we study how finite differences can be used to simulate acoustic wave propagation originating from a point source in the ocean using the Helmholtz equation. How to model sediment layers and the vast size of the ocean is studied in particular. The finite differences are implemented with summation by parts operators with boundary conditions enforced with simultaneous approximation terms and projection. The numerical solver is combined with the WaveHoltz method to improve the performance. Sediment layers are handled with interface conditions and the domain is artificially expanded using absorbing layers. The absorbing layer is implemented with an alternative approach to the super-grid method where the domain expansion is accomplished by altering the wave speed rather than with coordinate transformations. To isolate these issues, other parameters such as variations in the ocean floor are neglected. With this simplification, cylindrical coordinates are used and the angular variation is assumed to be zero. This reduces the problem to a quasi-three-dimensional system. We study how the parameters of the alternative absorbing layer approach affect its quality. The numerical solver is verified on several test cases and appears to work according to theory. Finally, a semi-realistic simulation is carried out and the solution seems correct in this setting.

Ziel der vorliegenden Arbeit ist es, Rühr- und Mischungsvorgänge in Flüssigmetallströmungen zu untersuchen, die mittels rotierender und wandernder Magnetfelder bzw. deren Kombination induziert werden. Im Mittelpunkt steht dabei die Charakterisierung der dreidimensionalen Strömungsstrukturen innerhalb zylindrischer Geometrien bei der Verwendung überkritischer Magnetfelder. Neben der Untersuchung der Strömungseigenschaften stellen die physikalische Modellierung der angreifenden Kräfte, die geeignete Wahl und Validierung eines effizienten numerischen Lösungsverfahrens und dessen Erweiterung für die Durchführung von Large Eddy Simulationen wesentliche Eckpfeiler dieser Arbeit dar.