Developing robust behavioral assays to study olfactory-driven behaviors allows for greater insight into the neural mechanisms behind them. Oftentimes, olfactory behavioral assays require a two-choice design, consistent variables, and controlled stimulus application. This can be challenging when working with marine dwelling organisms such as nudibranchs. Extensive work shows the importance of olfaction in both pre-metamorphic larval development and adult stage nudibranchs (Gastropoda, Mollusca). However, there is little research investigating how olfaction plays a role in rapidly developing, post-metamorphic juvenile nudibranchs such as Berghia stephanieae. To study olfactory-associated behaviors in juvenile Berghia, a novel behavioral microfluidic chip was designed which met the requirements for a reliable olfaction assay. Baseline motor behaviors such as general locomotion, turns, and contractions were observed. Despite individuals being raised in the same cohort, animal-to-animal variability was found in relation to their baseline behaviors. Xylene cyanol, a commonly used dye in microfluidics, was found to be aversive at a range of concentrations (0.075% - 0.025%) causing the animal to tightly contract and turn away from the stimulus. Juveniles showed no significant behavioral response to a 0.00125% dilution which was necessary to confirm a constant flow in the microfluidic chip. Juveniles showed a strong preference towards fluid that had been conditioned with their preferred food source odor, the sea anemone Exaiptasia diaphana. This was judged to be an innate preference because it occurred upon the first exposure of these animals to the odor. Serial dilution of Exaiptasia conditioned seawater (ECS) uncovered a threshold for behavioral preference of 60%. In summary, the development of this behavioral provides an opportunity to present controlled olfactory stimuli while observing the juvenile’s behaviors. This will allow future experiments to examine the neural mechanisms behind both aversive and attractive stimuli and provides a method for testing olfactory learning and memory in this species.

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<p>Flow pulsations in subchannel geometries play an important role in homogenization of fluid temperatures within a fuel rod bundle cross-section. As such, there is a strong need to develop accurate integral models that incorporate the underlying physics of these flows for inclusion in the broader safety analysis codes. This research is concerned with using computational fluid dynamics to investigate the flow pulsations in order to develop an enhanced understanding of the flow physics. The vast majority of previous experimental work has been in the turbulent regime, with varying degrees of geometric complexity. Previous numerical work has focused on steady or unsteady simulation of the turbulent experimental results, with the requirement that an appropriate turbulence model must be selected.</p> <p>Recent experimental work by Gosset and Tavoularis in 2006 has indicated that flow pulsations can occur under laminar conditions. Computational modeling of laminar flow pulsations provides an ideal framework for studying the physical mechanisms or instabilities that promote formation of the pulsations. Simulations of their experimental domain were run for a gap height normalized by the rod diameter (δ/D) of 0.3 and Reynolds numbers of 718, 900 and 955. These simulations found frequencies in the same range as Gosset and Tavoularis, as well as qualitatively similar particle tracks to their dye streaks. Analysis of the numerical pulsations showed them to be fluid rotations around the rod. These rotations were shown to be strongly correlated with the axial velocity gradient, which acted to transfer momentum from axial flow to the crossplane rotational pulsatile flow. The pulsations were shown to develop from a purely axial flow through disturbances in the axial velocity gradient, which initially arose near inflection points in the axial velocity profile in the spanwise direction. Under the influence of the axial velocity gradient and fluctuating pressure, these disturbances evolve into a sustained quasi-periodic flow.</p> / Master of Applied Science (MASc)

This thesis describes a simple efficient and robust numerical technique for solving two-dimensional incompressible laminar steady flows at moderate-to-high Reynolds numbers. The method uses an incremental multigrid method and an extrapolation procedure based on minimum residual concepts to accelerate the convergence rate of a robust block-line-Gauss-Seidel solver for the vorticity-stream function equations. Results are presented for the driven cavity flow problem using uniform and nonuniform grids and for the flow past a backward facing step in a channel. / M.S.

The boundary layer equations for a quasi-equilibrium flow of dissociating air past a flat plate have been solved on an electronic digital computer. The solution is based upon a modification of Crocco's method, which takes into consideration the variation of the Prandtl, Schmidt and Lewis numbers. The thermodynamic and transport properties of dissociating air have been evaluated utilizing the closed form expressions evolved by Hansen for approximate partition functions. This method of analysis permits the use of the most valid variations available for dissociating air properties with temperature. Air is treated as a mixture of oxygen and nitrogen in the ratio of one to four. The calculated shear function for dissociation air exceeds, by a maximum of 7.1 percent, the values obtained by Van Driest for non-dissociating air. The calculated enthalpy distribution varies considerably from that computed by Van Driest for a Prandt number of 0.75; the maximum variation being 10.6 percent greater than the calculated value. Results obtained here indicate that the enthalpy distribution is virtually independent of the variation of the product µρ, viscosity times density, with enthalpy. / M.S.

A theoretical study of convective heat transfer is presented for a laminar flow subjected to an axial variation in the external heat transfer coefficient (or dimensionless Biot number). Since conventional techniques fail for a variable boundary condition parameter, a variable eigenfunction approach is developed. An analysis is carried out for a periodic heat transfer coefficient, which serves as a model for heat transfer from a duct fitted with an array of evenly spaced fins. Three solution methods for the variable eigenfunction technique are examined: an Nth order approximation method, an iterative method and a stepwise periodic method. The stepwise periodic method provides the most convenient and accurate solution for a stepwise periodic Biot number. Graphical results match exactly to ones obtained by Charmchi and Sparrow from a finite-difference scheme. A connected region technique is also developed to provide limited exact results to test the validity of the three solution methods. The study of a finned duct by a stepwise periodic Biot number is carried out via a parametric study, an average (constant) Biot number approximation and an assumed velocity profile analysis. Results for the parametric study show that external finning yields substantial heat transfer enhancement over an unfinned duct, especially when the Biot number of the unfinned regions is low. A decrease in the interfin spacing causes increased enhancement. Variations of the period of the Biot number causes relatively small changes in enhancement as long as the ratio of finned to unfinned surface remains unchanged. An average (constant) Biot number approximation for a specified finned tube is compared to the stepwise periodic Biot number solution. The results show that the constant Biot number approximation provides accurate results. Finally, the results for the influence of the assumed velocity profile demonstrate that a constant velocity flow provides increased heat transfer and more effective enhancement by external finning than a laminar fully developed flow, especially at high Biot numbers. This study provides insight into heat transfer enhancement due to finning and also develops a solution methodology for problems involving variable boundary condition parameters. / M.S.

The two-dimensional, confined, laminar flow over a downstream facing step was studied using a finite element, Navier-Stokes equation solver. The weak form of the stationary, incompressible Navier-Stokes equations in primitive variable form was obtained using the conventional Galerkin technique for mixed problems. Biquadratic Lagrange interpolating polynomials were used to construct the basis functions that generated the finite-dimensional subspace containing the approximate solutions to the velocity field, while the pressure field was represented by a discontinuous, piecewise-linear approximation. This particular combination of solution subspaces was previously shown in a mathematically rigorous fashion to yield stable, consistent solutions to the Navier-Stokes equations. The results of the computations were benchmarked against the experimental data of Denham and Patrick, and also compared to earlier calculations by Ecer and Thomas, both of whom utilized alternative, unconventional formulations. These comparisons indicate that with the proper choice of basis functions, a conventional Galerkin scheme can yield results that are in as good and in many cases better agreement with the available experimental data than those of unconventional schemes that rely upon an infusion of artificial dissipation to enhance their numerical stability. The computational algorithm was also used to ascertain the cause of the noticeable lack of development and skewness that characterized the experimental data of Denham and Patrick both at and upstream of the step. The results of this study indicated that as suspected by Denham and Patrick, the skewness as well as the lack of development of the velocity profiles near the step were caused by the geometry of the test apparatus upstream of the step rather than by the presence of the step itself. The numerical experiments conducted here have been carefully documented so as to facilitate future comparisons intended to assess the relative efficiency of the present method of computation. / Doctor of Philosophy