15 research outputs found
Circle grid fractal plate as a turbulent generator for premixed flame: an overview
This review paper focuses to ascertain a new approach in turbulence generation on the structure of premixed flames and external combustion using a fractal grid pattern. This review paper discusses the relationship between fractal pattern and turbulence flow. Many researchers have explored the fractal pattern as a new concept of turbulence generators, but researchers rarely study fractal turbulence generators on the structure premixed flame. The turbulent flow field characteristics have been studied tand investigated in a premixed combustion application. In terms of turbulence intensity, most researchers used fractal grid that can be tailored so that they can design the characteristic needed in premixed flame. This approach makes it extremely difficult to determine the exact turbulent burning velocity on the velocity fluctuation of the flow. The decision to carry out additional research on the effect circle grid fractal plate as a turbulent generator for premixed flame should depends on the blockage ratio and fractal pattern of the grid.
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Detached Eddy Simulation for Turbulent Flows in a Pipe with a Snowflake Fractal Orifice
Sex- and age-related differences in the management and outcomes of chronic heart failure: an analysis of patients from the ESC HFA EORP Heart Failure Long-Term Registry
Aims: This study aimed to assess age- and sex-related differences in management and 1-year risk for all-cause mortality and hospitalization in chronic heart failure (HF) patients. Methods and results: Of 16 354 patients included in the European Society of Cardiology Heart Failure Long-Term Registry, 9428 chronic HF patients were analysed [median age: 66 years; 28.5% women; mean left ventricular ejection fraction (LVEF) 37%]. Rates of use of guideline-directed medical therapy (GDMT) were high (angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, beta-blockers and mineralocorticoid receptor antagonists: 85.7%, 88.7% and 58.8%, respectively). Crude GDMT utilization rates were lower in women than in men (all differences: P\ua0 64 0.001), and GDMT use became lower with ageing in both sexes, at baseline and at 1-year follow-up. Sex was not an independent predictor of GDMT prescription; however, age >75 years was a significant predictor of GDMT underutilization. Rates of all-cause mortality were lower in women than in men (7.1% vs. 8.7%; P\ua0=\ua00.015), as were rates of all-cause hospitalization (21.9% vs. 27.3%; P\ua075 years. Conclusions: There was a decline in GDMT use with advanced age in both sexes. Sex was not an independent predictor of GDMT or adverse outcomes. However, age >75 years independently predicted lower GDMT use and higher all-cause mortality in patients with LVEF 6445%
Universal hierarchical symmetry for turbulence and general multi-scale fluctuation systems
A diffusion equation to describe scaleâand timeâdependent dimensions of turbulent interfaces
Transition from Euclidean to fractal forms within a scale-covariant process: a turbulent combustion study
Multiscale flame fronts are generated by the combustion of turbulent
flows. Whereas most wrinkled fronts look fractal in a classical scale analysis,
the evolution of their geometry in scale space reveals that they definitely
stand part-way between the Euclidean and the fractal regimes. This intermediate
domain is studied by exploiting the scale-covariance of geometry formation.
An iterative evolution of front roughness from scale to scale is derived.
It corresponds to a deterministic evolution of geometry from the Euclidean
to the fractal regime which reveals a universal feature of this transition
Géométrie des peaux entropiques pour décrire intermittence de la turbulence de paroi
International audienceIn order to describe the phenomenon of intermittency in wall turbulence and, more particularly, the behaviour of moments p r ÎŽV and pr Δ and intermittency exponents ζP with the order p and distance to the wall, we developed a new geometrical framework called âentropic-skins geometryâ based on the notion of scale-entropy which is here applied to an experimental database of boundary layer flows. Each moment has its own spatial multi-scale support âŠp (âskinâ). The model assumes the existence of a hierarchy of multi-scale sets âŠp ranged from the âbulkâ to the âcrestâ. The crest noted characterizes the geometrical support where the most intermittent (the highest) fluctuations in energy dissipation occur; the bulk is the geometrical support for the whole range of fluctuations. The model assumes then the existence of a dynamical flux through the hierarchy of skins. The specific case where skins display a fractal structure is Investigated. Bulk fractal dimension Î f and crest dimension Îâ are linked by a scale-entropy flux defining a reversibility efficiency ( )/( ) f Îł d = Î âÎ âÎ â â (d is the embedding dimension). The model, initially developed for homogeneous and isotropic turbulent flows, is applied here to wall bounded turbulence where intermittency exponents are measured by extended self-similarity. We obtained for intermittency exponents the analytical expression [ ] /3 ( (1 ) 3 2) / 3 (3 )(1 ) pp ζ γγ Îł p = Î â + â + âÎ â â â with Îł â 0.36 in agreement withexperimental results