Unsteady low-Reynolds number flow control in different regimes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106476/1/AIAA2013-353.pd

A special purpose silicon compiler for designing supercomputing VLSI systems

Design of general/special purpose supercomputing VLSI systems for numeric algorithm execution involves tackling two important aspects, namely their computational and communication complexities. Development of software tools for designing such systems itself becomes complex. Hence a novel design methodology has to be developed. For designing such complex systems a special purpose silicon compiler is needed in which: the computational and communicational structures of different numeric algorithms should be taken into account to simplify the silicon compiler design, the approach is macrocell based, and the software tools at different levels (algorithm down to the VLSI circuit layout) should get integrated. In this paper a special purpose silicon (SPS) compiler based on PACUBE macrocell VLSI arrays for designing supercomputing VLSI systems is presented. It is shown that turn-around time and silicon real estate get reduced over the silicon compilers based on PLA's, SLA's, and gate arrays. The first two silicon compiler characteristics mentioned above enable the SPS compiler to perform systolic mapping (at the macrocell level) of algorithms whose computational structures are of GIPOP (generalized inner product outer product) form. Direct systolic mapping on PLA's, SLA's, and gate arrays is very difficult as they are micro-cell based. A novel GIPOP processor is under development using this special purpose silicon compiler

Integrated Process Chain for Aerostructural Wing Optimization and Application to an NLF Forward Swept Composite Wing

This contribution introduces an integrated process chain for aerostructural wing optimization based on high fidelity simulationmethods. The architecture of this process chain enables two of the most promising future technologies in commercial aircraft design in the context of multidisciplinary design optimization (MDO). These technologies are natural laminar flow (NLF) and aeroelastic tailoring using carbon fiber reinforced plastics (CFRP). With this new approach the application of MDO to an NLF forward swept composite wing will be possible. The main feature of the process chain is the hierarchical decomposition of the optimization problem into two levels. On the highest level the wing planform including twist and airfoil thickness distributions as well as the orthotropy direction of the composite structure will be optimized. The lower optimization level includes the wing box sizing for essential load cases considering the static aeroelastic deformations. Additionally, the airfoil shapes are transferred from a given NLF wing design. The natural laminar flow is considered by prescribing laminar-turbulent transition locations. Results of wing design studies and a wing optimization using the process chain are presented for a forward swept wing aircraft configuration. The wing optimization with 12 design parameters shows a fuel burn reduction in the order of 9% for the design mission

Evaluation of geometric conservation law using pressure-based fluid solver and moving grid technique

The geometric conservation law (GCL) is an important concept for moving grid techniques because it directly regulates the treatments of the fluid flow and grid movement. With the grid movement at every time instant, the Jacobian, associated with the volume of each element in curvilinear co-ordinates, needs to be updated in a conservative manner. In this study, alternative GCL schemes for evaluating the Jacobian have been investigated in the context of a pressure-based Navier-Stokes solver, utilizing moving grid and the first-order implicit time stepping procedure as well as the PISO scheme. GCL-based on first and second-order, implicit as well as time-averaged, time integration schemes were considered. Accuracy and conservative properties were tested on steady-state, laminar flow inside a 2D channel and time dependent, turbulent flow around a 3D elastic wing; both treated with moving grid techniques. It seems that the formal order of accuracy is not a decisive indicator. Instead, the speed of grid movement and the interplay between the flow solver and the GCL treatments make a more noticeable impact

Fluid-structure interaction for aeroelastic applications

The interaction between a flexible structure and the surrounding fluid gives rise to a variety of phenomena with applications in many areas, such as, stability analysis of airplane wings, turbomachinery design, design of bridges, and the flow of blood through arteries. Studying these phenomena requires modeling of both fluid and structure. Many approaches in computational aeroelasticity seek to synthesize independent computational approaches for the aerodynamic and the structural dynamic subsystems. This strategy is known to be fraught with complications associated with the interaction between the two simulation modules. The task is to choosing the appropriate models for fluid and structure based on the application, and to develop an efficient interface to couple the two models. In the present article, we review the recent advancements in the field of fluid-structure interaction, with specific attention to aeroelastic applications. One of the key aspects to developing a robust coupled aeroelastic model is the presence of an efficient moving grid technique to account for structural deformations. Several such techniques are reviewed in this paper. Also, the time scales associated with fluid-structure interaction problems can be very different; hence, appropriate time stepping strategies and/or sub-cycling procedures within the individual field need to be devised. The flutter predictions performed on an AGARD 445.6 wing at different Mach numbers are selected to highlight the state-of-the-art computational and modeling issues. © 2005 Elsevier Ltd. All rights reserved