Stochastic Modeling of Reversible Biochemical Reaction-Diffusion Systems and High-Resolution Shock-Capturing Methods for Fluid Interfaces

Thesis (Ph.D.)--University of Washington, 2016-08

Shock Train/Boundary-Layer Interaction in Rectangular Scramjet Isolators

Numerous studies of the dual-mode scramjet isolator, a critical component in preventing inlet unstart and/or vehicle loss by containing a collection of flow disturbances called a shock train, have been performed since the dual-mode propulsion cycle was introduced in the 1960s. Low momentum corner flow and other three-dimensional effects inherent to rectangular isolators have, however, been largely ignored in experimental studies of the boundary layer separation driven isolator shock train dynamics. Furthermore, the use of two dimensional diagnostic techniques in past works, be it single-perspective line-of-sight schlieren/shadowgraphy or single axis wall pressure measurements, have been unable to resolve the three-dimensional flow features inside the rectangular isolator. These flow characteristics need to be thoroughly understood if robust dual-mode scramjet designs are to be fielded. The work presented in this thesis is focused on experimentally analyzing shock train/boundary layer interactions from multiple perspectives in aspect ratio 1.0, 3.0, and 6.0 rectangular isolators with inflow Mach numbers ranging from 2.4 to 2.7. Secondary steady-state Computational Fluid Dynamics studies are performed to compare to the experimental results and to provide additional perspectives of the flow field. Specific issues that remain unresolved after decades of isolator shock train studies that are addressed in this work include the three-dimensional formation of the isolator shock train front, the spatial and temporal low momentum corner flow separation scales, the transient behavior of shock train/boundary layer interaction at specific coordinates along the isolator's lateral axis, and effects of the rectangular geometry on semi-empirical relations for shock train length prediction. A novel multiplane shadowgraph technique is developed to resolve the structure of the shock train along both the minor and major duct axis simultaneously. It is shown that the shock train front is of a hybrid oblique/normal nature. Initial low momentum corner flow separation spawns the formation of oblique shock planes which interact and proceed toward the center flow region, becoming more normal in the process. The hybrid structure becomes more two-dimensional as aspect ratio is increased but corner flow separation precedes center flow separation on the order of 1 duct height for all aspect ratios considered. Additional instantaneous oil flow surface visualization shows the symmetry of the three-dimensional shock train front around the lower wall centerline. Quantitative synthetic schlieren visualization shows the density gradient magnitude approximately double between the corner oblique and center flow normal structures. Fast response pressure measurements acquired near the corner region of the duct show preliminary separation in the outer regions preceding centerline separation on the order of 2 seconds. Non-intrusive Focusing Schlieren Deflectometry Velocimeter measurements reveal that both shock train oscillation frequency and velocity component decrease as measurements are taken away from centerline and towards the side-wall region, along with confirming the more two dimensional shock train front approximation for higher aspect ratios. An updated modification to Waltrup \& Billig's original semi-empirical shock train length relation for circular ducts based on centerline pressure measurements is introduced to account for rectangular isolator aspect ratio, upstream corner separation length scale, and major- and minor-axis boundary layer momentum thickness asymmetry. The latter is derived both experimentally and computationally and it is shown that the major-axis (side-wall) boundary layer has lower momentum thickness compared to the minor-axis (nozzle bounded) boundary layer, making it more separable. Furthermore, it is shown that the updated correlation drastically improves shock train length prediction capabilities in higher aspect ratio isolators. This thesis suggests that performance analysis of rectangular confined supersonic flow fields can no longer be based on observations and measurements obtained along a single axis alone. Knowledge gained by the work performed in this study will allow for the development of more robust shock train leading edge detection techniques and isolator designs which can greatly mitigate the risk of inlet unstart and/or vehicle loss in flight.

Large eddy simulation of shock boundary layer interaction control using micro-vortex generators

The performance of supersonic engine inlets and external aerodynamic surfaces can be critically affected by shock wave / boundary layer interactions (SBLIs), whose severe adverse pressure gradients can cause boundary layer separation. Currently such problems are avoided primarily through the use of boundary layer bleed/suction which can be a source of significant performance degradation. This study investigates a novel type of flow control device called micro-vortex generators (µVGs) which may offer similar control benefits without the bleed penalties. µVGs have the ability to alter the near-wall structure of compressible turbulent boundary layers to provide increased mixing of high speed fluid which improves the boundary layer health when subjected to flow disturbance. Due to their small size,µVGs are embedded in the boundary layer which provide reduced drag compared to the traditional vortex generators while they are cost-effective, physically robust and do not require a power source. To examine the potential of µVGs, a detailed experimental and computational study of micro-ramps in a supersonic boundary layer at Mach 3 subjected to an oblique shock was undertaken. The experiments employed a flat plate boundary layer with an impinging oblique shock with downstream total pressure measurements. The moderate Reynolds number of 3,800 based on displacement thickness allowed the computations to use Large Eddy Simulations without the subgrid stress model (LES-nSGS). The LES predictions indicated that the shock changes the structure of the turbulent eddies and the primary vortices generated from the micro-ramp. Furthermore, they generally reproduced the experimentally obtained mean velocity profiles, unlike similarly-resolved RANS computations. The experiments and the LES results indicate that the micro-ramps, whose height is h≈0.5δ, can significantly reduce boundary layer thickness and improve downstream boundary layer health as measured by the incompressible shape factor, H. Regions directly behind the ramp centerline tended to have increased boundary layer thickness indicating the significant three-dimensionality of the flow field. Compared to baseline sizes, smaller micro-ramps yielded improved total pressure recovery. Moving the smaller ramps closer to the shock interaction also reduced the displacement thickness and the separated area. This effect is attributed to decreased wave drag and the closer proximity of the vortex pairs to the wall. In the second part of the study, various types of µVGs are investigated including micro-ramps and micro-vanes. The results showed that vortices generated from µVGs can partially eliminate shock induced flow separation and can continue to entrain high momentum flux for boundary layer recovery downstream. The micro-ramps resulted in thinner downstream displacement thickness in comparison to the micro-vanes. However, the strength of the streamwise vorticity for the micro-ramps decayed faster due to dissipation especially after the shock interaction. In addition, the close spanwise distance between each vortex for the ramp geometry causes the vortex cores to move upwards from the wall due to induced upwash effects. Micro-vanes, on the other hand, yielded an increased spanwise spacing of the streamwise vortices at the point of formation. This resulted in streamwise vortices staying closer to the wall with less circulation decay, and the reduction in overall flow separation is attributed to these effects. Two hybrid concepts, named “thick-vane” and “split-ramp”, were also studied where the former is a vane with side supports and the latter has a uniform spacing along the centerline of the baseline ramp. These geometries behaved similar to the micro-vanes in terms of the streamwise vorticity and the ability to reduce flow separation, but are more physically robust than the thin vanes. Next, Mach number effect on flow past the micro-ramps (h~0.5δ) are examined in a supersonic boundary layer at M=1.4, 2.2 and 3.0, but with no shock waves present. The LES results indicate that micro-ramps have a greater impact at lower Mach number near the device but its influence decays faster than that for the higher Mach number cases. This may be due to the additional dissipation caused by the primary vortices with smaller effective diameter at the lower Mach number such that their coherency is easily lost causing the streamwise vorticity and the turbulent kinetic energy to decay quickly. The normal distance between the vortex core and the wall had similar growth indicating weak correlation with the Mach number; however, the spanwise distance between the two counter-rotating cores further increases with lower Mach number. Finally, various µVGs which include micro-ramp, split-ramp and a new hybrid concept “ramped-vane” are investigated under normal shock conditions at Mach number of 1.3. In particular, the ramped-vane was studied extensively by varying its size, interior spacing of the device and streamwise position respect to the shock. The ramped-vane provided increased vorticity compared to the micro-ramp and the split-ramp. This significantly reduced the separation length downstream of the device centerline where a larger ramped-vane with increased trailing edge gap yielded a fully attached flow at the centerline of separation region. The results from coarse-resolution LES studies show that the larger ramped-vane provided the most reductions in the turbulent kinetic energy and pressure fluctuation compared to other devices downstream of the shock. Additional benefits include negligible drag while the reductions in displacement thickness and shape factor were seen compared to other devices. Increased wall shear stress and pressure recovery were found with the larger ramped-vane in the baseline resolution LES studies which also gave decreased amplitudes of the pressure fluctuations downstream of the shock.

Photoionization upstream of a strong shock wave,

"Sponsored mainly by the Bureau of Naval Weapons, through Contract NOw 62-0604-c under Brown University Subcontract No. 168319."

Investigation of test time at undertailored conditions in a shock tunnel.

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Some properties of shock relaxation in gas flows carrying small particles.

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Solidarity, the network and the history of workers' self-management from the Gdańsk Agreement to shock therapy

This PhD thesis is an empirical research project in the field of modern Polish history. The thesis focuses on Solidarity, the Network and the idea of workers’ self-management. In addition, the thesis is based on an in-depth analysis of Solidarity archival material. The Solidarity trade union was born in August 1980 after talks between the communist government and strike leaders at the Gdansk Lenin Shipyards. In 1981 a group called the Network rose up, due to cooperation between Poland’s great industrial factory plants. The Network grew out of Solidarity; it was made up of Solidarity activists, and the group acted as an economic partner to the union. The Network was the base of a grass-roots, nationwide workers’ self-management movement. Solidarity and the self-management movement were crushed by the imposition of Martial Law in December 1981. Solidarity revived itself immediately, and the union created an underground society. The Network also revived in the underground, and it continued to promote self-management activity where this was possible. When Solidarity regained its legal status in April 1989, workers’ self-management no longer had the same importance in the union. Solidarity’s new politico-economic strategy focused on free markets, foreign investment and privatization. This research project ends in July 1990, when the new Solidarity-backed government enacted a privatization law. The government decided to transform the property ownership structure through a centralized privatization process, which was a blow for supporters of workers’ self-management. This PhD thesis provides new insight into the evolution of the Solidarity union from 1980-1990 by analyzing the fate of workers’ self-management. This project also examines the role of the Network throughout the 1980s. There is analysis of the important link between workers’ self-management and the core ideas of Solidarity. In addition, the link between political and economic reform is an important theme in this research project. The Network was aware that authentic workers’ self-management required reforms to the authoritarian political system. Workers’ self-management competed against other politico-economic ideas during the 1980s in Poland. The outcome of this competition between different reform concepts has shaped modern-day Polish politics, economics and society.

Radiation from a D-dimensional collision of shock waves: two-dimensional reduction and Carter–Penrose diagram

We analyze the causal structure of the two-dimensional (2D) reduced background used in the perturbative treatment of a head-on collision of two D-dimensional Aichelburg–Sexl gravitational shock waves. After defining all causal boundaries, namely the future light-cone of the collision and the past light-cone of a future observer, we obtain characteristic coordinates using two independent methods. The first is a geometrical construction of the null rays which define the various light cones, using a parametric representation. The second is a transformation of the 2D reduced wave operator for the problem into a hyperbolic form. The characteristic coordinates are then compactified allowing us to represent all causal light rays in a conformal Carter–Penrose diagram. Our construction holds to all orders in perturbation theory. In particular, we can easily identify the singularities of the source functions and of the Green’s functions appearing in the perturbative expansion, at each order, which is crucial for a successful numerical evaluation of any higher order corrections using this method.

Septic Shock Sera Containing Circulating Histones Induce Dendritic Cell–Regulated Necrosis in Fatal Septic Shock Patients

International audience

Mathematical analysis of maximum power generated by photovoltaic systems and fitting curves for standard test conditions

The rural electrification is characterized by geographical dispersion of the population, low consumption, high investment by consumers and high cost. Moreover, solar radiation constitutes an inexhaustible source of energy and in its conversion into electricity photovoltaic panels are used. In this study, equations were adjusted to field conditions presented by the manufacturer for current and power of small photovoltaic systems. The mathematical analysis was performed on the photovoltaic rural system I- 100 from ISOFOTON, with power 300 Wp, located at the Experimental Farm Lageado of FCA/UNESP. For the development of such equations, the circuitry of photovoltaic cells has been studied to apply iterative numerical methods for the determination of electrical parameters and possible errors in the appropriate equations in the literature to reality. Therefore, a simulation of a photovoltaic panel was proposed through mathematical equations that were adjusted according to the data of local radiation. The results have presented equations that provide real answers to the user and may assist in the design of these systems, once calculated that the maximum power limit ensures a supply of energy generated. This real sizing helps establishing the possible applications of solar energy to the rural producer and informing the real possibilities of generating electricity from the sun.

Circulating leukocyte heat shock protein 70 (HSP70) and oxidative stress markers in rats after a bout of exhaustive exercise

A novel method to measure oxidative stress resulting from exhaustive exercise in rats is presented. In this new procedure we evaluated the erythrocyte antioxidant enzymes, catalase ( CAT) and glutathione reductase (GR), the plasma oxidative attack markers, reactive carbonyl derivatives (RCD) and thiobarbituric reactive substances (TBARS). Muscular tissue damage was evaluated by monitoring plasma creatine kinase (CK) and plasma taurine ( Tau) concentrations. Also, we monitored total sulphydryl groups (TSG) and uric acid (UA), and the level of the 70 kDa heat shock protein (HSP70) in leukocytes as a marker of oxidative stress. In the study we found a correspondence between erythrocyte CAT and GR activities and leukocyte HSP70 levels, principally 3 h after the acute exercise, and this suggested an integrated mechanism of antioxidant defense. The increase in levels of plasma Tau was coincident with the increasing plasma levels of CK and TBARS, principally after two hours of exercise. Thus tissue damage occurred before the expression of any anti-oxidant system markers and the monitoring of Tau, CK or TBARS may be important for the estimation of oxidative stress during exhaustive exercise. Furthermore, the integrated analyses could be of value in a clinical setting to quantify the extent of oxidative stress risk and reduce the need to perform muscle biopsies as a tool of clinical evaluation.

Sensitivity analysis in optimized parametric curve fitting

Purpose – Curve fitting from unordered noisy point samples is needed for surface reconstruction in many applications -- In the literature, several approaches have been proposed to solve this problem -- However, previous works lack formal characterization of the curve fitting problem and assessment on the effect of several parameters (i.e. scalars that remain constant in the optimization problem), such as control points number (m), curve degree (b), knot vector composition (U), norm degree (k), and point sample size (r) on the optimized curve reconstruction measured by a penalty function (f) -- The paper aims to discuss these issues -- Design/methodology/approach - A numerical sensitivity analysis of the effect of m, b, k and r on f and a characterization of the fitting procedure from the mathematical viewpoint are performed -- Also, the spectral (frequency) analysis of the derivative of the angle of the fitted curve with respect to u as a means to detect spurious curls and peaks is explored -- Findings - It is more effective to find optimum values for m than k or b in order to obtain good results because the topological faithfulness of the resulting curve strongly depends on m -- Furthermore, when an exaggerate number of control points is used the resulting curve presents spurious curls and peaks -- The authors were able to detect the presence of such spurious features with spectral analysis -- Also, the authors found that the method for curve fitting is robust to significant decimation of the point sample -- Research limitations/implications - The authors have addressed important voids of previous works in this field -- The authors determined, among the curve fitting parameters m, b and k, which of them influenced the most the results and how -- Also, the authors performed a characterization of the curve fitting problem from the optimization perspective -- And finally, the authors devised a method to detect spurious features in the fitting curve -- Practical implications – This paper provides a methodology to select the important tuning parameters in a formal manner -- Originality/value - Up to the best of the knowledge, no previous work has been conducted in the formal mathematical evaluation of the sensitivity of the goodness of the curve fit with respect to different possible tuning parameters (curve degree, number of control points, norm degree, etc.)

Shock anafiláctico con manzana: síndrome LTP

Presentamos el caso de una paciente atendida en urgencias del centro de salud por un cuadro clínico de shock anafiláctico desencadenado tras la ingesta de manzana y realización posterior de ejercicio físico. En alergia a alimentos, hay que tener presente que en algunas personas es necesaria la presencia de determinados cofactores como el ejercicio físico o la ingesta de determinados fármacos como los AINEs para que suceda una reacción alérgica. Se sospecha que el mecanismo responsable consiste en que aceleren la absorción del alimento en el intestino y así lleguen a modular la severidad de los síntomas. Por este motivo cuando las LTP (proteína de transferencia de lípidos) están implicadas, si los cofactores no se detectan y previenen, pueden representar un serio riesgo para el desarrollo de episodios de anafilaxia severos o fatales.

Fitting phase type distribution to service process with sequential phases

The work of this thesis is concerned with fitting Hypo-exponential and Erlang phase type distributions for modeling real life processes with non-exponential service time. There exist situations where exponential distributions cannot explain the distribution of service time properly. This thesis presents the application of two traditional statistical estimation techniques to approximate the service distributions of processes with coefficient of variation less than one. It also presents an algorithm to fit Hypo-exponential distribution for complex situations which can’t be handled properly with traditional estimation techniques. The result shows the effect of variation of sample size and other parameters on the efficiency of the estimation techniques by comparing their respective outputs. Furthermore it checks how accurately the proposed algorithm approximates a given distribution.

Estudo da molhabilidade de ligas de adição à base de prata sobre insertos cerâmicos para aplicação em brocas perfuração de poços de petróleo

Metal-ceramic interfaces are present in tricone drill bits with hard ceramic inserts for oil well drilling operations. The combination of actions of cutting, crushing and breaking up of rocks results in the degradation of tricone drill bits by wear, total or partial rupture of the drill bit body or the ceramic inserts, thermal shock and corrosion. Also the improper pressfitting of the ceramic inserts on the bit body may cause its total detachment, and promote serious damages to the drill bit. The improvement on the production process of metal-ceramic interfaces can eliminate or minimize some of above-mentioned failures presented in tricone drill bits, optimizing their lifetime and so reducing drilling metric cost. Brazing is a widely established technique to join metal-ceramic materials, and may be an excellent alternative to the common mechanical press fitting process of hard ceramic inserts on the steel bit body for tricone drill bit. Wetting phenomena plays an essential role in the production of metal/ceramic interfaces when a liquid phase is present in the process. In this work, 72Silver-28Copper eutectic based brazing alloys were melted onto zirconia, silicon nitride and tungsten carbide/Co substrates under high vacuum. Contact angle evolution was measured and graphically plotted, and the interfaces produced were analysed by SEM-EDX. The AgCu eutectic alloy did not wet any ceramic substrates, showing high contact angles, and so without chemical interaction between the materials. Better results were found for the systemns containing 3%wt of titanium in the AgCu alloy. The presence os titanium as a solute in the alloy produces wettable cand termodinamically stable compounds, increasing the ceramics wetting beahviour