Optimization of clamped circular piezoelectric composite actuators

This paper addresses the design of clamped circular piezoceramic composite unimorph and bimorph configurations, specifically the conflicting requirements of maximum volume displacement for a prescribed bandwidth.Anoptimization problem is formulatedthatimplements analytical solutions for unimorph and bimorph configurations using laminated plate theory, including the use of oppositely polarized piezoceramic patches. A range of actuator geometric parameters are studied, and bounds for volume displacement and natural frequency of optimal designs are determined and presented via design curves. In the selected design space, Pareto optimization results for unimorph and bimorph configurations show that optimal volume displacement is related to the bandwidth by a universal power law such that the product of the square of the natural frequency and the displaced volume, a “gain-bandwidth” product, is a constant. Characteristic trends are also described that are independent of the actuator radius for the Pareto optimal piezoceramic patch thickness and radius versus normalized bandwidth. The results are relevant, for example, in the design of zero-net mass-flux or synthetic jet actuators used in flow control applications

Shape optimization of supersonic turbines using global approximation methods

There is growing interest to adopt supersonic turbines for rocket propulsion. However, this technology has not been actively investigated in the United States for the last three decades. To aid design improvement, a global optimization framework combining the radial-basis neural network (NN) and the polynomial response surface (RS) method is constructed for shape optimization of a two-stage supersonic turbine, involving (script O)(10) design variables. The design of the experiment approach is adopted to reduce the data size needed by the optimization task. The combined NN and RS techniques are employed. A major merit of the RS approach is that it enables one to revise the design space to perform multiple optimization cycles. This benefit is realized when an optimal design approaches the boundary of a predefined design space. Furthermore, by inspecting the influence of each design variable, one can also gain insight into the existence of multiple design choices and select the optimum design based on other factors such as stress and materials consideration

Computational-fluid-dynamics-based design optimization for single-element rocket injector

A computational-fluid-dynamics-based design optimization approach, utilizing the response surface method, has been proposed for a single-element rocket injector. The overall goal of the effort is to demonstrate the integration of a set of computational and optimization tools to enable the injector designer to objectively determine the trades between performance and life during the design cycle. Using design of experiment techniques, 54 cases are selected, and computational solutions based on the Navier-Stokes equations, finite rate chemistry, and the k-ε turbulence closure are obtained. The response surface methodology is employed as the optimization tool. Four independent design variables are selected, namely, H2 flow angle, H2 and O2 flow areas with fixed flow rates, and O 2 posttip thickness. Design optimization is guided by four design objectives. The maximum temperature on the injector element oxidizer posttip, the maximum temperature on the injector face, and a combustion chamber wall temperature are chosen as life indicators. The length of the combustion zone is selected as an indicator of mixing and performance. In the context of this effort, the design optimization tools performed efficiently and reliably. In addition to establishing optimum designs by varying emphasis on the individual objectives, better insight into the interplay between design variables and their impact on the design objectives is gained. The need to include environmental design objectives early in the design phase is clearly established

Remote resupply systems for unmanned FCS-related vehicles

The refueling systems for unmanned future combat system (FCS)-related vehicles were discussed. A resupply (RS) system was defined as an autonomous robotic platform, which interacts with a combat vehicles (CV). The impact of emerging technologies on RS was also considered. The important enabling technologies are range sensing and terrain reasoning

Global design optimization for aerodynamics and rocket propulsion components

Modern computational and experimental tools for aerodynamics and propulsion applications have matured to a stage where they can provide substantial insight into engineering processes involving fluid flows, and can be fruitfully utilized to help improve the design of practical devices. In particular, rapid and continuous development in aerospace engineering demands that new design concepts be regularly proposed to meet goals for increased performance, robustness and safety while concurrently decreasing cost. To date, the majority of the effort in design optimization of fluid dynamics has relied on gradient-based search algorithms. Global optimization methods can utilize the information collected from various sources and by different tools. These methods offer multi-criterion optimization, handle the existence of multiple design points and trade-offs via insight into the entire design space, can easily perform tasks in parallel, and are often effective in filtering the noise intrinsic to numerical and experimental data. However, a successful application of the global optimization method needs to address issues related to data requirements with an increase in the number of design variables, and methods for predicting the model performance. In this article, we review recent progress made in establishing suitable global optimization techniques employing neural-network- and polynomial-based response surface methodologies. Issues addressed include techniques for construction of the response surface, design of experiment techniques for supplying information in an economical manner, optimization procedures and multi-level techniques, and assessment of relative performance between polynomials and neural networks. Examples drawn from wing aerodynamics, turbulent diffuser flows, gas-gas injectors, and supersonic turbines are employed to help demonstrate the issues involved in an engineering design context. Both the usefulness of the existing knowledge to aid current design practices and the need for future research are identified