scispace - formally typeset
Search or ask a question
Institution

Langley Research Center

FacilityHampton, Virginia, United States
About: Langley Research Center is a facility organization based out in Hampton, Virginia, United States. It is known for research contribution in the topics: Mach number & Wind tunnel. The organization has 15945 authors who have published 37602 publications receiving 821623 citations. The organization is also known as: NASA Langley & NASA Langley Research Center.


Papers
More filters
Journal ArticleDOI
TL;DR: Numerical results of simulations of the plane Poiseuille flow driven either by pressure gradient or a fixed velocity profile at entrance as well as of the 2D Womersley flow are presented and are found to be in excellent agreement with theory.
Abstract: In this paper a lattice Boltzmann (LB) model to simulate incompressible flow is developed. The main idea is to explicitly eliminate the terms of o(M 2), where M is the Mach number, due to the density fluctuation in the existing LB models. In the proposed incompressible LB model, the pressure p instead of the mass density ρ is the independent dynamic variable. The incompressible Navier–Stokes equations are derived from the incompressible LB model via Chapman–Enskog procedure. Numerical results of simulations of the plane Poiseuille flow driven either by pressure gradient or a fixed velocity profile at entrance as well as of the 2D Womersley flow are presented. The numerical results are found to be in excellent agreement with theory.

1,115 citations

Book
01 Jan 1994
TL;DR: In this paper, the authors introduce the concept of Frequency Domain System ID (FDSI) and Frequency Response Functions (FRF) for time-domain models, as well as Frequency-Domain Models with Random Variables and Kalman Filter.
Abstract: 1. Introduction. 2. Time-Domain Models. 3. Frequency-Domain Models. 4. Frequency Response Functions. 5. System Realization. 6. Observer Identification. 7. Frequency Domain System ID. 8. Observer/Controller ID. 9. Recursive Techniques. Appendix A: Fundamental Matrix Algebra. Appendix B: Random Variables and Kalman Filter. Appendix C: Data Acquisition.

1,079 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present an introduction to ionic polymer-metal composites and some mathematical modeling pertaining to them and discuss a number of recent findings in connection with ion-exchange polymer metal composites (IPMCS) as biomimetic sensors and actuators.
Abstract: This paper presents an introduction to ionic polymer-metal composites and some mathematical modeling pertaining to them. It further discusses a number of recent findings in connection with ion-exchange polymer-metal composites (IPMCS) as biomimetic sensors and actuators. Strips of these composites can undergo large bending and flapping displacement if an electric field is imposed across their thickness. Thus, in this sense they are large motion actuators. Conversely by bending the composite strip, either quasi-statically or dynamically, a voltage is produced across the thickness of the strip. Thus, they are also large motion sensors. The output voltage can be calibrated for a standard size sensor and correlated to the applied loads or stresses. They can be manufactured and cut in any size and shape. In this paper first the sensing capability of these materials is reported. The preliminary results show the existence of a linear relationship between the output voltage and the imposed displacement for almost all cases. Furthermore, the ability of these IPMCs as large motion actuators and robotic manipulators is presented. Several muscle configurations are constructed to demonstrate the capabilities of these IPMC actuators. This paper further identifies key parameters involving the vibrational and resonance characteristics of sensors and actuators made with IPMCS. When the applied signal frequency varies, so does the displacement up to a critical frequency called the resonant frequency where maximum deformation is observed, beyond which the actuator response is diminished. A data acquisition system was used to measure the parameters involved and record the results in real time basis. Also the load characterizations of the IPMCs were measured and it was shown that these actuators exhibit good force to weight characteristics in the presence of low applied voltages. Finally reported are the cryogenic properties of these muscles for potential utilization in an outer space environment of a few Torrs and temperatures of the order of - 140 degrees Celsius. These muscles are shown to work quite well in such harsh cryogenic environments and thus present a great potential as sensors and actuators that can operate at cryogenic temperatures.

1,050 citations

Journal ArticleDOI
TL;DR: A survey of recent publications in the field of aerospace where interest in MDO has been particularly intense is presented, focused on the interaction of the structures discipline with other disciplines.
Abstract: The increasing complexity of engineering systems has sparked increasing interest in multidisciplinary optimization (MDO). This paper presents a survey of recent publications in the field of aerospace where interest in MDO has been particularly intense. The two main challenges of MDO are computational expense and organizational complexity. Accordingly the survey is focused on various ways different researchers use to deal with these challenges. The survey is organized by a breakdown of MDO into its conceptual components. Accordingly, the survey includes sections on Mathematical Modeling, Design- oriented Analysis, Approximation Concepts, Optimization Procedures, System Sensitivity, and Human Interface. With the authors'' main expertise being in the structures area, the bulk of the references focus on the interaction of the structures discipline with other disciplines. In particular, two sections at the end focus on two such interactions that have recently been pursued with a particular vigor: Simultaneous Optimization of Structures and Aerodynamics, and Simultaneous Optimization of Structures Combined With Active Control.

1,049 citations

Journal ArticleDOI
TL;DR: This work investigates the use of kriging models as alternatives to traditional second-order polynomial response surfaces for constructing global approximations for use in a real aerospace engineering application, namely, the design of an aerospike nozzle.
Abstract: Response surface methods have been used for a variety of applications in aerospace engineering, particularly in multidisciplinary design optimization. We investigate the use of kriging models as alternatives to traditional second-order polynomial response surfaces for constructing global approximations for use in a real aerospace engineering application, namely, the design of an aerospike nozzle. Our objective is to examine the difeculties in building and using kriging models to create accurate global approximations to facilitate multidisciplinary design optimization. Error analysis of the response surface and kriging models is performed, along with a graphical comparison of the approximations. Four optimization problems are also formulated and solved using both sets of approximation models to gain insight into their use for multidisciplinary design optimization. We end that the kriging models, which use only a constant “global” model and a Gaussian correlation function, yield global approximations that are slightly more accurate than the response surface models.

1,040 citations


Authors

Showing all 16015 results

NameH-indexPapersCitations
Daniel J. Jacob16265676530
Donald R. Blake11872749697
Veerabhadran Ramanathan10030147561
Raja Parasuraman9140241455
Robert W. Platt8863831918
James M. Russell8769129383
Daniel J. Inman8391837920
Antony Jameson7947431518
Ya-Ping Sun7927728722
Patrick M. Crill7922820850
Richard B. Miles7875925239
Patrick Minnis7749023403
Robert W. Talbot7729719783
Raphael T. Haftka7677328111
Jack E. Dibb7534418399
Network Information
Related Institutions (5)
Ames Research Center
35.8K papers, 1.3M citations

89% related

German Aerospace Center
26.7K papers, 553.3K citations

89% related

Air Force Research Laboratory
24.6K papers, 493.8K citations

87% related

United States Naval Research Laboratory
45.4K papers, 1.5M citations

85% related

Jet Propulsion Laboratory
14.3K papers, 548.1K citations

85% related

Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202335
202286
2021571
2020540
2019669
2018797