Aerodynamic Shape Optimization using Simultaneous Pseudo-Timestepping

The paper deals with a numerical method for aerodynamic shape optimization. It is based on simultaneous pseudo-timestepping in which stationary states are obtained by solving the non-stationary system of equations representing the state, costate and design equations. The main advantages of this method are that it requires no additional globalization techniques and that a preconditioner can be used for convergence acceleration which stems from the reduced SQP method. A design example for drag reduction for an RAE2822 airfoil, keeping its thickness fixed, is included. The overall cost of computation is less than 4 times that of the forward simulation run

Aerodynamic shape optimization using simultaneous pseudo-timestepping

The paper deals with a numerical method for aerodynamic shape optimization. It is based on simultaneous pseudo-timestepping in which stationary states are obtained by solving the non-stationary system of equations representing the state, costate and design equations. The main advantages of this method are that it requires no additional globalization techniques and that a preconditioner can be used for convergence acceleration which stems from the reduced SQP method. A design example for drag reduction for an RAE2822 airfoil, keeping its thickness fixed, is included. The overall cost of computation is less than four times that of the forward simulation run

Optimal Aerodynamic Design under Uncertainty

Recently, optimization has become an integral part of the aerodynamic design process chain. However, because of uncertainties with respect to the flight conditions and geometry uncertainties, a design optimized by a traditional design optimization method seeking only optimality may not achieve its expected performance. Robust optimization deals with optimal designs, which are robust with respect to small (or even large) perturbations of the optimization setpoint conditions. That means, the optimal designs computed should still be good designs, even if the input parameters for the optimization problem formulation are changed by a non-negligible amount. Thus even more experimental or numerical effort can be saved. In this paper, we aim at an improvement of existing simulation and optimization technology, developed in the German collaborative effort MEGADESIGN1, so that numerical uncertainties are identified, quantized and included in the overall optimization procedure, thus making robust design in this sense possible. We introduce two robust formulations of the aerodynamic optimization problem which we numerically compare in a 2d testcase under uncertain flight conditions. Beside the scalar valued uncertainties we consider the shape itself as an uncertainty source and apply a Karhunen-Loève expansion to approximate the infinite-dimensional probability space. To overcome the curse of dimensionality an adaptively refined sparse grid is used in order to compute statistics of the solution

Microphytoplankton species assemblages, species-specific carbon stock and nutrient stoichiometry in the shallow continental shelf of the northern Bay of Bengal during winter

1827-1835Microphytoplankton species composition, diversity, abundance and biomass (chlorophyll-a) was studied for the first time in the shallow continental shelf (Thalassionema frauenfeldii was the most abundant species, followed by Thalassionema nitzschioides and Coscinodiscus radiatus. Highest cell chlorophyll and carbon content was found in Coscinodiscus gigas. Dinoflagellate species were found to comprise 15.55% of the total taxa. Amongst the dinoflagellates, Ceratium furca had the highest abundance, whereas Ceratium symmetricum had the maximum species-specific chlorophyll and carbon stock. The nutrient stoichiometry was highly deviated from the standard Redfield ratio of Si: N: P (16:16:1)