Interactions between viscous and transonic effects in air flow around a laminar wing were investigated computationally by means of the solution of unsteady Reynolds-averaged Navier-Stokes Equations. The subject is important from the point of view of applications of Natural Laminar Flow technology in modern, economically efficient passenger aircraft. The research was focused on simulations and analyses of influence of turbulence induced by micro vortex generators on intensity of harmful transonic phenomena like strong shock waves and buffet. Two ways of modelling of the effects of turbulators-the micro vortex generators were taken into consideration. The first way consisted in resolving the shape and inclination angle of the generator in the grid over airfoil and setting the non-slip wall boundary condition on the surface of the generator. The second way, taking advantage of the BAY model of vortex generator, was implemented on orthogonal grid without the need of resolving the shape of the vortex generator in the grid. Calibration of the BAY model was aimed at producing similar distribution of vorticity and velocity circulation behind the model of the vortex generator, as obtained for the grid-resolved model of the vortex generator. The calibration procedure resulted, however, in overestimated turbulisation of the boundary layer in the BAY model, compared to the effects of the grid-resolved vortex generator. The flow simulations indicated, however, that turbulisation of boundary layer induced by micro vortex generators can reduce or eliminate the oscillation of strong shock wave and buffet in off-design conditions and that further adjusting of the BAY model is an efficient strategy for modelling the interactions between viscous and transonic effects in air flow around a laminar wing.

A relatively large number of calcite-cemented fractures are present in gas-bearing shale formations. During hydraulic fracturing, some of these fractures will be reactivated and may become important flow paths in the resulting stimulated fracture network. On the other hand, the presence of carbonate lamina on fracture surfaces will have a hindering effect on the transport of shale gas from the matrix toward the wellbore. We investigate numerically the effect of low-pH reactive fluids on such fractures, and show that dissolution of the cement proceeds in a highly nonuniform manner. The morphology of the emerging flow paths ("wormholes") strongly depends on the thickness of the calcite layer. For thick carbonate layers, a hierarchical, fractal pattern appears, with highly branched wormhole-like channels competing for an available flow. For thin layers, the pattern is much more diffuse, with less-pronounced wormholes that merge easily with each other. Finally, for intermediate thicknesses, we observe a strong attraction between shorter and longer wormholes, which leads to the formation of islands of carbonate lamina surrounded by the dissolved regions. We argue that the wormholeformation processes are not only important for the increase of shale-gas recovery, but also can be used for retaining the fracture permeability, even in the absence of proppant.2019 SPE Journal 1 is the main driving process behind the cave formation in karst systems (Dreybrodt 1990;Hanna and Rajaram 1998;Cheung and Rajaram 2002;Szymczak and Ladd 2011). All these studies show that the dissolution of rock fractures is a strongly unstable process, with spontaneous focusing of the flow in high-porosity channels (wormholes). The instability here is, in fact, stronger than the corresponding instability in the dissolving porous media (Szymczak and Ladd 2011), with much weaker stabilization caused by diffusion. It needs to be stressed that both experimental and numerical studies of fracture dissolution have considered homogeneous soluble samples, in which aperture growth is potentially unlimited. In shales, the situation is fundamentally different, because the amount of soluble cement at a given place is finite and, thus, after a certain time, the cement fully dissolves, and the dissolution front moves farther downstream. As it turns out, a limited amount of soluble material significantly influences the dissolution patterns in fractures. Nevertheless, as we show in the present study, the dissolution front is still unstable, with an intense wormhole formation in the system. Besides serving as a means to increase the fracture-matrix transport, such a nonuniform dissolution is potentially important for retaining the fracture permeability even in the absence of proppant Wu and Sharma 2015). Whereas a uniformly etched fracture may close tightly under the load of overburden once the fluid pressure is removed, the nonuniform etching will tend to maintain the permeability. The less-dissolved regions will then act as supports to keep more-dissolved regions op...

Our go al was to investigate the postope rative diffe ren ces in hearing between patients who had had their stape dius tendon sa cr ificed and tho se whose stap edius tendon was preserv ed du ring las er stapes surgeryfo rotosclerosis. To that end, we perfonn ed a retrospecti ve review by ma iling exte nsive qu estionnaires to patients who had been operat ed on bet ween 1994 and 1997. We also perform ed routine and special audiom etr ic testin g to au gm eilt the subjective data. Seventy-nine of 124 questionnaires (64 %J were returned. Ofthe respo ndents, 75patients had undergo ne additional p re-and/o r po stop erati ve audiom etri c .testing, including tests to evaluate "h earing in nois e " and to determine the " uncoinfo rtable loudn ess level " (dynamic ran geJ. We fo und no stat istically sig nifi cant diffe rences between the two gro up s with respe et to their subj ective respo nse s and their audiolog ic test result s. The respottses to the qu esti onnaire indteated that in most cases, hearing was improv ed by stapes surgery. We cone lude that the stape dius tendon S /lO U Id be preser ved whenever possible du ring stapes surg ery , provid ed that it does not jeopardize the exposure or outco tne. Fro m the Ear Research Foun dati on, Sara sota, Fia.

The iatrogenic subclavian artery injury is a rare but potentially serious complication of subclavian vein cannulation. The use of endovascular techniques is an alternative to surgical repair especially in patients with concomitant diseases in whom immediate, potentially large surgery would be associated with a high risk of perioperative complications. This article discusses technical aspects of endovascular repair of iatrogenic injury of subclavian artery with implantation of covered stents based on two cases. Author's experience and data from literature suggests that endovascular management including covered stent implantation is safe and effective treatment and should be considered as a method of choice especially among patients in poor general condition and/or major comorbidities.

An important goal of the TFAST project was to study the effect of the location of transition in relation to the shock wave on the separation size, shock structure and unsteadiness of the interaction area. Boundary layer tripping (by wire or roughness) and flow control devices (Vortex Generators and cold plasma) were used for boundary layer transition induction. As flow control devices were used here in the laminar boundary layer for the first time, their effectiveness in transition induction was an important outcome. It was intended to determine in what way the application of these techniques induces transition. These methods should have a significantly different effect on boundary layer receptivity, i.e. the transition location. Apart from an improved understanding of operation control methods, the main objective was to localize the transition as far downstream as possible while ensuring a turbulent character of interaction. The final objective, involving all the partners, was to build a physical model of transition control devices. Establishing of such model would