Acoustic modal analysis with heat release fluctuations using nonlinear eigensolvers

Closed combustion devices like gas turbines and rockets are prone to thermoacoustic instabilities. Design engineers in the industry need tools to accurately identify and remove instabilities early in the design cycle. Many different approaches have been developed by the researchers over the years. In this work we focus on the Helmholtz wave equation based solver which is found to be relatively fast and accurate for most applications. This solver has been a subject of study in many previous works. The Helmholtz wave equation in frequency space reduces to a nonlinear eigenvalue problem which needs to be solved to compute the acoustic modes. Most previous implementations of this solver have relied on linearized solvers and iterative methods which as shown in this work are not very efficient and sometimes inaccurate. In this work we make use of specialized algorithms implemented in SLEPc that are accurate and efficient for computing eigenvalues of nonlinear eigenvalue problems. We make use of the n-tau model to compute the reacting source terms in the Helmholtz equation and describe the steps involved in deriving the Helmholtz eigenvalue equation and obtaining its solution using the SLEPc library

Computationally-Efficient And Scalable Implementation Of Chemistry In Large-Scale Simulations Of Turbulent Combustion

A major challenge in the numerical simulations of turbulent reacting flows involving large numbers of chemical species and reactions is the accurate and computationally-efficient representation of combustion chemistry. Recent advances on the experimental and theoretical fronts of the study of real fuel chemistry have led to more accurate chemical mechanisms of real fuels involving hundreds to thousands of species and thousands of reactions. However, the direct use of such detailed chemistry in large-scale calculations of turbulent reacting flows still remains computationally prohibitive. In our work, we focus on the combined Large-Eddy Simulation (LES)/Probability Density Function (PDF) computations of turbulent reacting flows, in which the thermochemical composition of the fluid is represented by a large number of particles. To reduce the cost of chemistry calculations in large-scale LES/PDF computations, we have developed a combined dimension reduction and tabulation approach in which the chemistry is represented accurately and efficiently in terms of a reduced number of "represented species". In this combined approach, the dimension reduction of combustion chemistry is performed using the Rate-Controlled Constrained-Equilibrium (RCCE) method, followed by tabulation using the In Situ Adaptive Tabulation (ISAT) algorithm. An automated Greedy Algorithm with Local Improvement (GALI) has been developed for selecting good rep- resented species for use in this approach. In addition, we have developed a Partitioned Uniform Random (P-URAN) parallel strategy for the efficient parallel implementation of chemistry in large-scale LES/PDF simulations on multiple cores. This strategy has been tested by performing full-scale LES/PDF simulations of the Sandia Flame D turbulent jet flame on up to 9,216 cores and it is found to achieve good scaling. In this work (1) we describe in detail the implementation of ISAT/RCCE/GALI and the P-URAN parallel strategy; (2) we show that the combined ISAT/RCCE/GALI yields orders of magnitude speed-up with very good error control; (3) we demonstrate that our implementation of RCCE is an accurate, efficient and robust implementation; (4) we show that the P-URAN parallel strategy achieves over 85% relative weak scaling efficiency and around 60% relative strong scaling efficiency on up to 9,216 cores; (5) we show that the combined ISAT/RCCE methodology with P-URAN significantly reduces the simulation time; and (6) a combination of ISAT/RCCE and PURAN algorithms enables us to perform accurate and computationally-efficient large-scale LES/PDF simulations with real fuel chemistry involving hundreds of chemical species

Integration of the environmental management aspect in the optimization of the design and planning of energy systems

The increasing concerns regarding the environmental pollution derived from anthropogenic activities, such as the use of fossil fuels for power generation, has driven many interested parties to seek different alternatives, e.g. use of renewable energy sources, use of “cleaner” fuels and use of more effective technologies, in order to minimize and control the quantity of emissions that are produced during the life cycle of conventional energy sources. In addition to these alternatives, the use of an integrated procedure in which the environmental aspect will be taken into account during the design and planning of energy systems could provide a basis on which emissions reduction will be dealt with a life cycle approach. The work presented in this paper focuses on the examination of the possibilities of integrating the environmental aspects in the preliminary phase of the conventional design and planning of energy systems in conjunction with other parameters, such as financial cost, availability, capacity, location, etc. The integration of the environmental parameter to the design is carried out within a context where Eco-design concepts are applied. Due to the multi-parameter nature of the design procedure, the tools that are used are Life Cycle Analysis and Multi-criteria Analysis. The proposed optimization model examines and identifies optimum available options of the use of different energy sources and technologies for the production of electricity and/or heat by minimizing both the financial cost and the environmental impacts, with regard to a multiple objective optimization subject to a set of specific constraints. Implementation of the proposed model in the form of a case study for the island of Rhodes in Greece revealed that an optimized solution both cost and environmental-wise, would be an almost balanced participation of renewables and non-renewable energy sources in the energy mix

Edible Flowers: Adding a Dash of Flavour

40-41Including edible flowers in the diet can add a dash of flavour and enhance the nutritional value of the food too. However, caution is advised in picking the right kind of flowers under appropriate conditions

Cross species/genera transferability of simple sequence repeat markers, genetic diversity and population structure analysis in gladiolus (Gladiolus × grandiflorus L.) genotypes

Background Genetic analysis of gladiolus germplasm using simple sequence repeat (SSR) markers is largely missing due to scarce genomic information. Hence, microsatellites identified for related genera or species may be utilized to understand the genetic diversity and assess genetic relationships among cultivated gladiolus varieties. Methods In the present investigation, we screened 26 genomic SSRs (Gladiolus palustris, Crocus sativus, Herbertia zebrina, Sysirinchium micranthum), 14 chloroplast SSRs (Gladiolus spp., chloroplast DNA regions) and 25 Iris Expressed Sequence Tags (ESTs) derived SSRs across the 84 gladiolus (Gladiolus × grandiflorus L.) genotypes. Polymorphic markers detected from amplified SSRs were used to calculate genetic diversity estimates, analyze population structure, cluster analysis and principal coordinate analysis (PCoA). Results A total of 41 SSRs showed reproducible amplification pattern among the selected gladiolus cultivars. Among these, 17 highly polymorphic SSRs revealed a total of 58 polymorphic alleles ranging from two to six with an average of 3.41 alleles per marker. Polymorphic information content (PIC) values ranged from 0.11 to 0.71 with an average value of 0.48. A total of 4 SSRs were selectively neutral based on the Ewens–Watterson test. Hence, 66.66% of Gladiolus palustris, 48% of Iris spp. EST, 71.42% of Crocus sativus SSRs showed cross-transferability among the gladiolus genotypes. Analysis of genetic structure of 84 gladiolus genotypes revealed two subpopulations; 35 genotypes were assigned to subpopulation 1, 37 to subpopulation 2 and the remaining 12 genotypes could not be attributed to either subpopulation. Analysis of molecular variance indicated maximum variance (53.59%) among individuals within subpopulations, whereas 36.55% of variation among individuals within the total population. The least variation (9.86%) was noticed between two subpopulations. Moderate (FST = 0.10) genetic differentiation between two subpopulations was observed. The grouping pattern of population structure was consistent with the unweighted pair group method with arithmetic mean (UPGMA) dendrogram based on simple matching dissimilarity coefficient and PCoA. Conclusion SSR markers from the present study can be utilized for cultivar identification, conservation and sustainable utilization of gladiolus genotypes for crop improvement. Genetic relationships assessed among the genotypes of respective clusters may assist the breeders in selecting desirable parents for crossing