The objective of this research is to construct an efficient global topology optimization method using machine learning technologies. In the conventional design process of mechanical design, the conceptual design is the earliest stage of the design process; and it is carried out based on the designer's own idea/experience. Therefore, it is difficult to obtain innovative and high-quality concepts overwhelming the designer's knowledge since the earliest stage of the design process has the largest impact. In this research, therefore, the black-box function aerodynamic topology optimization algorithm via machine learning technologies (FANTOM) is developed to overcome the problem. In the FANTOM approach, topology optimization problems are solved using/combining two efficient global optimization methods developed by the authors: the efficient global optimization method for discontinuous optimization problems with infeasible regions using classification method, and the efficient global optimization method via clustering/classification methods and exploration strategy. In the present approach, topological optimal designs can be obtained only by setting an objective function and constraint conditions. The validity of the FANTOM approach is demonstrated in an inviscid drag minimization problem at a two-dimensional supersonic flow condition, which provides an optimal topology as the Busemann biplane airfoil. Executing topology optimizations with the variation in freestream Mach number, it is also demonstrated that the FANTOM approach can explore topological optimal designs robustly.
RecA protein catalyzes the DNA annealing and mimics the DNA strand exchange reaction in vitro in the presence of ATP or its non-hydrolyzable analog, adenosine 5'-O-3-thiotriphosphate (ATPgammaS). For these activities RecA coordinates two DNA molecules [Takahashi, M. and Nordén, B. (1994) Adv. Biophys. 30, 1-35]. In order to get a better understanding of how RecA performs the search for sequence complementarity or homology between two DNA molecules, the association and dissociation kinetics of a second DNA molecule to and from RecA in the presence of ATPgammaS have been investigated. The kinetics were monitored by fluorescence measurements of partly etheno-modified poly(dA) assisted by linear dichroism measurements of the flow-oriented complex. The association of the second DNA is fast, regardless of whether the sequence is complementary or not. By contrast, the dissociation kinetics is strongly dependent on sequence complementarity. If the second DNA is complementary to the first, dissociation is extremely slow, whilst that of non-complementary second DNA is fast. In no case does the first DNA leave the RecA fiber. Our findings indicate that the dissociation step is important in the search for homology by RecA.
This paper is concerned with the optimal design simulation on the incompressible viscous flow based on the fictitious domain FEM and the Kriging response surface approach. The Navier-Stokes equation and the equation of continuity are used as a governing equation. In the fictitious domain FEM, a finite element mesh is divided into foreground and background domain. The formulation is carried out based on the Lagrange multiplier method to reflect the physical quantity of the foreground domain to background. The crossing number algorithm is employed for the simulation for the foreground domain to perform the fluid analysis stably. In this study, the flow analysis considering the crossing number algorithm is introduced to the shape optimization. An approximate surface is formed by the Kriging surface approach, and the optimal shape is obtained by the genetic algorithm.
The relationship between optimized blade airfoil shape and effect of flow interaction between blade airfoils is studied on a small, straight Darrieus type vertical axis wind turbine (VAWT). To compare Pareto optimal blade airfoil shapes, a multi-objective shape optimization is performed using a surrogate model-based global optimization approach. The objective functions are the performance of VAWT at one and three blade(s) conditions. These conditions correspond to the cases with and without the flow interaction effect between blade airfoils. The performance is evaluated by 2D unsteady incompressible computational fluid dynamics simulations using ANSYS Fluent. The Pareto optimal airfoil shape at the one blade condition has a thin trailing edge while that at the three blades condition has a thicker airfoil with a rounded outer surface. The rounded airfoil reduces the performance due to spoil higher pressure on outer surface. On the other hand, it also reduces the effect of the wake. It leads to the improvement in the performance with other blade airfoils and the rounded airfoil has best performance as a whole rotor.
The generation of shock waves is inevitable during supersonic cruising, which results in the generation of wave drag as well as sonic boom on the ground. Some innovative concepts, such as the supersonic biplane concept and supersonic twin-body fuselage concept, have been proposed recently to reduce the supersonic wave drag dramatically. In this study, these two concepts are adopted, and then the aerodynamic and sonic boom performance of innovative supersonic transport (SST) wing-body configurations are discussed using numerical approaches. This study is performed to obtain design knowledge for the innovative SST using an optimization method. In this research, the number of design variables is limited to only three in order to obtain fundamental design knowledge of the innovative SST configuration. The three design variables are utilized to deform the wing section shape. The wing section shape of a Busemann-type-biplane/twin-body model is optimized under the conditions of a design Mach number of 1.7 and angle of attack of 2 degrees. The optimized results show the tradeoff relationship between lift-drag ratio and maximum overpressure of sonic boom distribution on the ground. To obtain detailed knowledge of the design space, analysis of variance and visualizations of response surfaces of objective functions are also performed.
