Analytical and experimental investigation of circulation control by means of a turbulent Coanda jet

An analytical and experimental investigation of circulation control on a circular cylinder by means of tangential blowing (Coanda effect) is presented. The analytical method developed has also been used to estimate the blowing coefficients required for achieving potential flow on airfoils with flaps. The analysis is presented for conditions for which the flow in the boundary layer ahead of the jet exit is turbulent. The turbulent boundary layer and the jet layer on the upper surface, and the turbulent boundary layer on the lower surface are computed by a multi-strip integral method. The region of integration is between the correponding transition and separation points on each surface. Longitudinal curvature effects, which give rise to a radial pressure gradient across the jet layer and to an additional adverse tangential pressure gradient just upstream of the separation point, are included in the jet layer analysis in an approximate manner. The longitudinal curvature effect is found to have a pronounced influence on the separation of the jet layer

Nonlinear lift and pressure distribution of slender conical bodies with strakes at low speeds

Nonlinear lift and pressure distribution of slender conical bodies with strakes at low spee

Nonconical theory of flow past slender wing bodies with leading-edge separation

Nonconical theory of flow past slender wing bodies with leading edge separatio

Evans Medicine

Newsletter of the Evans Memorial Department of Clinical Research and Preventive Medicine at University Hospital

Evans Medicine

Newsletter of the Evans Memorial Department of Clinical Research and Preventive Medicine at University Hospital

Evans Medicine

Newsletter of the Evans Memorial Department of Clinical Research and Preventive Medicine at University Hospital

Evans Medicine

Newsletter of the Evans Memorial Department of Clinical Research and Preventive Medicine at University Hospital

Flashback, burning velocities and hydrogen admixture:Domestic appliance approval, gas regulation and appliance development

Introducing natural gas/hydrogen mixtures to an installed population of domestic natural gas appliances necessarily implies considering the risk of flashback. Previously, we quantified this risk via an interchangeability analysis using calculated laminar burning velocities. With an increasing contribution of renewable energy, still higher hydrogen fractions will become of interest to improve the economic viability in power-to-gas chains. To extend the possibilities for hydrogen admixture beyond the limits given by extant ranges of Wobbe Index and burning velocity, appliance approval standards and gas regulations must be examined to assess the degree to which higher hydrogen fractions are, or can be, justified. However, the current standards and regulations do not consider the risk of flashback in terms of the laminar burning velocity explicitly, leaving the justification of higher hydrogen fractions to empirical observations followed when the approval standards were codified. Here, we reframe the approval and regulation standards in terms of the calculated laminar burning velocity, which quantifies the notion of a 'safety margin' to safeguard appliance performance with respect to flashback, for a group of natural gases that is commonplace in the European Union (EU) but representative for many international situations. The method presented can be applied for any local regulatory area. In plots of burning velocity vs. equivalence ratio, ranges of regulated gas qualities are represented as a curve for natural gases, while for natural gas/hydrogen mixtures they appear as areas indicating the variations in hydrogen fraction for different gas compositions that do not increase the risk of flashback. To quantify the safety margin, the approval gas used in the EU for flashback (G222) is taken as an example, because of the many decades of experience in using this gas to safeguard appliance performance. Using the assumed range of gas quality and approval gas as an example, for appliances whose primary equivalence ratio is fuel rich (at greatest risk for flashback), a safety margin of 11.5 cm/s is determined and used in analyses for determining the composition of flashback limit gases in approval standards for a situation in which higher hydrogen fractions are desired. Situations considering both variable and constant fractions of hydrogen in natural gas are examined. The end-use demand for a minimum degree of thermal comfort, by having a minimum Wobbe Index in the regulated range of gas quality, automatically complicates grid management schemes for hydrogen addition: the maximum hydrogen admixture is necessarily coupled to the composition of the natural gas to which it is added. The only solution for having a constant hydrogen fraction without regard to the gas composition is by relaxing this demand on thermal comfort; in the example used here, 20% hydrogen admixture reduces the thermal comfort in the worst case by 4.7%. Fuel suppliers, grid operators and end users must agree to this loss of fitness for purpose to maximize the decarbonization of the gas supply by hydrogen admixture

Spectroscopy of Chemically Linked Dimers:1,3-(1,1’-Dinaphthyl)propane in a Naphthalene Host

Results of absorption, fluorescence and selective-excitation experiments on the chemically linked dimer 1,3-(1,1'-dinaphthyl)propane in a naphthalene host at 1.8 K are presented. This system is shown to consist of two translationally inequivalent pairs of the naphthalene moiety, occupying non-substitutional sites in the host lattice. This gives rise to two sets of dimer absorptions, split by 40 and 97 cm -1

Objects as battlefields in the struggle for civil rights: The archaeology and analysis of contemporary material culture and heritage in Chile

In October of 2019 began, as a manifestation of growing discontent, in Santiago de Chile a movement of social protests popularly known as “Estallido social”. This movement marched against social inequality and high cost of living, targeting the neoliberal system established during the dictatorship of Augusto Pinochet as responsible. Although Chile has been a democracy since 1990, inequality and social injustice has perpetuated  in democracy. We reflect on the role of the contemporary objects, their contexts and the position of archaeology in revealing current struggle discourse of civil rights, social diversity and social conflicts. Likewise, we analyze the transformation process of cultural heritage meanings through time, observable both in the appropriation of quotidian objects as way as protest as the resignification of the traditional monuments erected in the city