Numerical Simulation of UVA Ramjet/Scramjet Hypersonic Engine with Hydrogen-Air Combustion Using Wind-US

The internal flowpath of University of Virginia\u27s Mach 5, direct-connect, dual-mode scramjet engine was simulated using Wind-US, a density-based Reynolds-Averaged Navier-Stokes flow solver. Detailed flowfield simulation results are directly compared to experimental data to evaluate the accuracy of the numerical model and to provide insight into the flowfield behavior. Four hydrogen-air reaction mechanisms were initially assessed using the Burrows-Kurkov case. An Evans-Schexnayder, 7-specie, 8-reaction set with third body efficiencies was then selected for the scramjet simulations. The scramjet simulations included one fuel-off case and two reacting cases with different equivalence ratios, all with clean, non-vitiated air supply. The strong sensitivity of the simulation results to the choice of turbulent Schmidt number is demonstrated. For low equivalence ratio, excellent agreement with experimental data is achieved. For high equivalence ratio, the results agree with that of experiment, however, this case shows large numerical and combustion instabilities

Evaluation and Correlation of Some Properties of Coal

Mining is one of the oldest profession in world. The development and enrichment of society and mankind have experienced a direct relationship with it. The excavation of mineral resources comes with its complexities. The advancement of knowledge and technology have helped to address a lot of issues, yet many challenges remain because of the uncertainties in the earth materials. One of the major challenges is to select the right tool. Typically the selection of tools depend on the characteristics of earth materials. Rock mass is highly heterogeneous. Investigations and research in the field of rock mechanics and applied geology help in evaluating the influence of basic rock parameters such as strength, durability, crushability, etc. in effective mine designing and planning. There exists many approaches to correlate the different parameters of the rock mass so that the major influencing parameter can be predicted from a few other parameters that require relatively inexpensive processes at insitu conditions. This investigation was an attempt to determine a few strength parameters of coal and develop interrelationship among those. Coal samples from six different surface locations are collected and their unconfined compressive strength, Brazilian tensile strength, point load index, slake durability, impact strength index as well as the moisture content values have been determined at laboratory. Unconfined compressive strength of rock material is a major parameter that influence the selection of cutting tool. Correlation between these parameters are developed statistically to find the best fit equation. Applicability of a few established criteria as Broch and Franklin (1972), Bieniawski (1975), D’Andrea et al. (1964), Cargill and Shakoor (1990), Rusnak and Mark (2000), Fener et al. (2005), Kahraman et al. (2012) and Altindag and Guney (2010) have been evaluated and the predicted values were compared with those obtained by the laboratory tests

Dynamics of spheroids in pressure driven flows of shear thinning fluids

Particles in inertialess flows of shear thinning fluids are a model representation for several systems in biology, ecology, and micro-fluidics.In this paper, we analyze the motion of a spheroid in a pressure driven flow of a shear thinning fluid.The shear thinning rheology is characterized by the Carreau model.We use a combination of perturbative techniques and the reciprocal theorem to delineate the kinematics of prolate and oblate spheroids.There are two perturbative strategies adopted, one near the zero shear Newtonian plateau and the other near the infinite shear Newtonian plateau.In both limits, we find that a reduction in effective viscosity decreases the spheroid's rotational time period in pressure driven flows.The extent to which shear thinning alters the kinematics is a function of the particle shape.For a prolate particle, the effect of shear thinning is most prominent when the spheroid projector is aligned in the direction of the velocity gradient, while for an oblate particle the effect is most prominent when the projector is aligned along the flow direction.Lastly, we compare the tumbling behavior of spheroids in pressure driven flow to those in simple shear flow.While the time period decreases monotonically with Carreau number for pressure driven flows, the trend is non monotonic for shear flows where time period first increases at low Carreau number and then decreases at high Carreau numbers.Shear thinning does not resolve the degeneracy of Jefferey's orbits

Transient compressible flow in a compliant viscoelastic tube

Motivated by problems arising in the pneumatic actuation of controllers for micro-electromechanical systems (MEMS), labs-on-a-chip or biomimetic soft robots, and the study of microrheology of both gases and soft solids, we analyze the transient fluid--structure interaction (FSIs) between a viscoelastic tube conveying compressible flow at low Reynolds number. We express the density of the fluid as a linear function of the pressure, and we use the lubrication approximation to further simplify the fluid dynamics problem. On the other hand, the structural mechanics is governed by a modified Donnell shell theory accounting for Kelvin--Voigt-type linearly viscoelastic mechanical response. The fluid and structural mechanics problems are coupled through the tube's radial deformation and the hydrodynamic pressure. For small compressibility numbers and weak coupling, the equations are solved analytically via a perturbation expansion. Three illustrative problems are analyzed. First, we obtain exact (but implicit) solutions for the pressure for steady flow conditions. Second, we solve the transient problem of impulsive pressurization of the tube's inlet. Third, we analyze the transient response to an oscillatory inlet pressure. We show that an oscillatory inlet pressure leads to acoustic streaming in the tube, attributed to the nonlinear pressure gradient induced by the interplay of FSI and compressibility. Furthermore, we demonstrate an enhancement in the volumetric flow rate due to FSI coupling. The hydrodynamic pressure oscillations are shown to exhibit a low-pass frequency response (when averaging over the period of oscillations), while the frequency response of the tube deformation is similar to that of a band-pass filter.Comment: 27 pages, 11 figures; v2 revision removes Knudsen number effects and clarifies a few points; accepted for publication in Physics of Fluid

Right sided infective endocarditis: a forgotten complication of septic abortion

Right-sided native valve infective endocarditis (IE) refers to IE involving the tricuspid or pulmonic valve. In developing countries, septic abortion is still prevalent due to instrumental delivery by untrained personnel. We report a case of a 22-year-old lady with right-sided IE and pulmonary septic embolization complicating septic abortion. The patient was treated with IV antibiotics, however, she succumbed to the illness following worsening respiratory distress and cardiac arrest

An unusual case of hypopituitarism

Lymphocytic hypophysitis represents a difficult diagnostic and therapeutic challenge. The clinical presentation of this inflammatory condition may mimic that of a pituitary adenoma with apoplexy. We report a case of a 45 years old male patient with acute adrenal crisis complicating chronic hypopituitarism secondary to lymphocytic hypophysitis. The patient was managed acutely with high dose steroids and supportive measures, and is currently doing well