Role of computational fluid dynamics in unsteady aerodynamics for aeroelasticity

In the last two decades there have been extensive developments in computational unsteady transonic aerodynamics. Such developments are essential since the transonic regime plays an important role in the design of modern aircraft. Therefore, there has been a large effort to develop computational tools with which to accurately perform flutter analysis at transonic speeds. In the area of Computational Fluid Dynamics (CFD), unsteady transonic aerodynamics are characterized by the feature of modeling the motion of shock waves over aerodynamic bodies, such as wings. This modeling requires the solution of nonlinear partial differential equations. Most advanced codes such as XTRAN3S use the transonic small perturbation equation. Currently, XTRAN3S is being used for generic research in unsteady aerodynamics and aeroelasticity of almost full aircraft configurations. Use of Euler/Navier Stokes equations for simple typical sections has just begun. A brief history of the development of CFD for aeroelastic applications is summarized. The development of unsteady transonic aerodynamics and aeroelasticity are also summarized

Computational, unsteady transonic aerodynamics and aeroelasticity about airfoils and wings

Research in the area of computational, unsteady transonic flows about airfoils and wings, including aeroelastic effects is reviewed. In the last decade, there have been extensive developments in computational methods in response to the need for computer codes with which to study fundamental aerodynamic and aeroelastic problems in the critical transonic regime. For example, large commercial aircraft cruise most effectively in the transonic flight regime and computational fluid dynamics (CDF) provides a new tool, which can be used in combination with test facilities to reduce the costs, time, and risks of aircraft development

Transonic unsteady aerodynamic and aeroelastic calculations about airfoils and wings

Research in the area of computational unsteady transonic flows about airfoils and wings, including aeroelastic effects was surveyed. In the last decade, there were extensive developments in computational methods in response to the need for computer codes with which to study fundamental aerodynamic and aeroelastic problems in the critical transonic regime. For example, large commercial aircraft cruise most effectively in the transonic flight regime and computational fluid dynamics (CFD) provides a new tool, which can be used in combination with test facilities to reduce the costs, time, and risks of aircraft development

Extension of a streamwise upwind algorithm to a moving grid system

A new streamwise upwind algorithm was derived to compute unsteady flow fields with the use of a moving-grid system. The temporally nonconservative LU-ADI (lower-upper-factored, alternating-direction-implicit) method was applied for time marching computations. A comparison of the temporally nonconservative method with a time-conservative implicit upwind method indicates that the solutions are insensitive to the conservative properties of the implicit solvers when practical time steps are used. Using this new method, computations were made for an oscillating wing at a transonic Mach number. The computed results confirm that the present upwind scheme captures the shock motion better than the central-difference scheme based on the beam-warming algorithm. The new upwind option of the code allows larger time-steps and thus is more efficient, even though it requires slightly more computational time per time step than the central-difference option

Efficient Quality of Service Support in Multimedia Computer Operating Systems

This report describes our approach towards providing quality of service (QoS) guarantees for network communication within the endsystems to support multimedia applications. We first address the problem of QoS specification by identifying a set of application classes and their QoS parameters that cover the communication requirements of most applications. We then describe the QoS mapping problem, and show how requirements for resources (such as the CPU, the network interface adaptor and network connections) can be automatically derived from the application QoS parameters. We then deal with the QoS enforcement issue in which we describe techniques for scheduling protocol processing threads in order to reduce context switching overhead, as well as derive sufficiency conditions in order to provide predictable performance. We integrate all these solutions in a protocol implementation model. The key feature of the model is that protocols are part of the application process and are processed using protocol threads with individual scheduling attributes derived using our QoS mapping method. We propose several performance improvement techniques for application level protocol implementations that can reduce the high cost of data movement and context switching in these implementations. A significant component of this work will consist of implementation and experimentation which will result in significant contributions of practical utility

Distributed Data Layout, Scheduling and Playout Control in a Large Scale Multimedia Storage Server

this paper, we will consider only a retrieval environment and primarily focus on the strong interaction between the architecture, data layout, data compression, and scheduling. In particular, we will present distributed multilevel data layout, scheduling and playout control schemes developed in conjunction with our architecture. These schemes allow all clients to access the same data without data replication and support both buffered as well as bufferless clients. Also, they provide strict Large Scale Multimedia Servers 2 deterministic guarantees to each active client during normal playout as well as a full spectrum of interactive stream control operations (namely, fast forward, rewind, frame advance, slow play, slow rewind, pause, stop-and-return and stop). Our implementation of the stream control operations requires no extra bandwidth reservation and provides acceptable operation latency of a few hundread milliseconds. The rest of this paper is organized as follows: Various service models that are possible for a ondemand multimedia server are illustrated in Section 2. The basics of our prototype implementation of a large scale server are presented in Section 3. Section 4 describes the distributed and hierarchical data layout scheme. Next, our basic multilevel scheduling scheme is illustrated in Section 5. Various ways of implementing playout control operations and their implications on scheduling are described in Section 6. This section also presents modifications that must be made in the basic scheduling scheme to achieve smooth transition between normal playout and operations such as ff and rw

Design and Implementation of Visual Cryptography System for Transmission of Secure Data

In recent period of time security of the transmitted data is most critical problem, as network technology is greatly advanced and heaps of information is transmitted via net. Visual cryptography strategy is one of the most secure technique for privacy auspices, that allow the encryption of secret image or data by transferring it into the secure percentage and such a strategy is able to recover the secret image or data. This behavior makes visual cryptography especially useful for the low computation load requirement. In this paper, we are providing the information regarding information security by using Visual Cryptography scheme by making use of exclusive new technique of splitting of images along with their pixels rotation with the help of generated random number. We also have made an attempt to overcome some of the disadvantages of preexisting techniques of encryption and decryption. Finally, successful transmission of the message from transmitting end to receiving end without any interception was done. Most importantly, it is very difficult to hack by use of any professional hacking techniques as the message is encrypted twice. Hence the data is highly secured under transmission pat