Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “computational structural dynamics”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

SEADYN Analysis of a Tow Line for a High Altitude Towed Glider

The concept of using a system, consisting of a tow aircraft, glider and tow line, which would enable subsonic flight at altitudes above 24 km (78 kft) has previously been investigated. The preliminary results from these studies seem encouraging. Under certain conditions these studies indicate the concept is feasible. However, the previous studies did not accurately take into account the forces acting on the tow line. Therefore in order to investigate the concept further a more detailed analysis was needed. The code that was selected was the SEADYN cable dynamics computer program which was developed at the Naval Facilities Engineering Service Center. The program is a finite element based structural analysis code that was developed over a period of 10 years. The results have been validated by the Navy in both laboratory and at actual sea conditions. This code was used to simulate arbitrarily-configured cable structures subjected to excitations encountered in real-world operations. The Navy's interest was mainly for modeling underwater tow lines, however the code is also usable for tow lines in air when the change in fluid properties is taken into account. For underwater applications the fluid properties are basically constant over the length of the tow line. For the tow aircraft/glider application the change in fluid properties is considerable along the length of the tow line. Therefore the code had to be modified in order to take into account the variation in atmospheric properties that would be encountered in this application. This modification consisted of adding a variable density to the fluid based on the altitude of the node being calculated. This change in the way the code handled the fluid density had no effect on the method of calculation or any other factor related to the codes validation.

Colozza, Anthony J.↗
NASA NTRS2003

Embedded Wing Propulsion Conceptual Study

As a part of distributed propulsion work under NASA's Revolutionary Aeropropulsion Concepts or RAC project, a new propulsion-airframe integrated vehicle concept called Embedded Wing Propulsion (EWP) is developed and examined through system and computational fluid dynamics (CFD) studies. The idea behind the concept is to fully integrate a propulsion system within a wing structure so that the aircraft takes full benefits of coupling of wing aerodynamics and the propulsion thrust stream. The objective of this study is to assess the feasibility of the EWP concept applied to large transport aircraft such as the Blended-Wing-Body aircraft. In this paper, some of early analysis and current status of the study are presented. In addition, other current activities of distributed propulsion under the RAC project are briefly discussed.

Kim, Hyun D.↗
NASA NTRS2002

Signal-to-Noise Ratio Prediction and Validation for Space Shuttle GPS Flight Experiment

A deterministic method for Space Station Global Positioning System (GPS) Signal-To- Noise Ratio (SNR) predictions is proposed. The complex electromagnetic interactions between GPS antennas and surrounding Space Station structures are taken into account by computational electromagnetic technique. This computer simulator is capable of taking into account multipath effects from dynamically changed solar panels and thermal radiators. A comparison with recent collected Space Station GPS system flight experiment data is presented. The simulation results are in close agreement with flight data.

Hwu, Shian U.↗
NASA NTRSDate not supplied

Exploring the Impact of Sideslip Angle on Acoustic Predictions of an Open Rotor System Using Scale-Resolving Simulations

The development of innovative open-rotor propulsion systems that meet performance, fuel efficiency, and noise standards for commercial use depends significantly on the availability of reliable and computationally efficient tools for aerodynamic performance and noise prediction.This investigation demonstrates the capability of the structured curvilinear overset gridComputational Fluid Dynamics solver within the Launch, Ascent, and Vehicle Aerodynamics framework to predict the aerodynamic and aeroacoustic characteristics of a Contra-RotatingOpen Rotor propulsion system under various sideslip angles. In this publication, results obtained using a Hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation-based scale-resolving turbulence closure approach are validated against existing experimental measurements including aerodynamic loads, moments, and tones.

AATT↗
NASA NTRS1991

Computations involving differential operators and their actions on functions

The algorithms derived by Grossmann and Larson (1989) are further developed for rewriting expressions involving differential operators. The differential operators involved arise in the local analysis of nonlinear dynamical systems. These algorithms are extended in two different directions: the algorithms are generalized so that they apply to differential operators on groups and the data structures and algorithms are developed to compute symbolically the action of differential operators on functions. Both of these generalizations are needed for applications.

Crouch, Peter E.↗
NASA NTRS2002

Hubble Space Telescope Pointing Performance Due to Micro-Dynamic Disturbances from the NICMOS Cryogenic Cooler

The Vibration Admittance Test (VET) was performed to measure the emitted disturbances of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Cryogenic Cooler (NCC) in preparation for NCC installation onboard the Hubble Space Telescope (HST) during Servicing Mission 3B (SM3B). Details of the VET ground-test are described, including facility characteristics, sensor complement and configuration, NCC suspension, and background noise measurements. Kinematic equations used to compute NCC mass center displacements and accelerations from raw measurements are presented, and dynamic equations of motion for the NCC VET system are developed and verified using modal test data. A MIMO linear frequency-domain analysis method is used to compute NCC-induced loads and HST boresight jitter from VET measurements. These results are verified by a nonlinear time-domain analysis approach using a high-fidelity structural dynamics and pointing control simulation for HST. NCC emitted acceleration levels not exceeding 35 micro-g rms were measured in the VET and analysis methods herein predict 3.1 milli-areseconds rms jitter for HST on-orbit. Because the NCC is predicted to become the predominant disturbance source for HST, VET results indicate that HST will continue to meet the 7 milli-arcsecond pointing stability mission requirement in the post-SM3B era.

Clapp, Brian R.↗
NASA NTRS2003

Dynamically Reconfigurable Approach to Multidisciplinary Problems

The complexity and autonomy of the constituent disciplines and the diversity of the disciplinary data formats make the task of integrating simulations into a multidisciplinary design optimization problem extremely time-consuming and difficult. We propose a dynamically reconfigurable approach to MDO problem formulation wherein an appropriate implementation of the disciplinary information results in basic computational components that can be combined into different MDO problem formulations and solution algorithms, including hybrid strategies, with relative ease. The ability to re-use the computational components is due to the special structure of the MDO problem. We believe that this structure can and should be used to formulate and solve optimization problems in the multidisciplinary context. The present work identifies the basic computational components in several MDO problem formulations and examines the dynamically reconfigurable approach in the context of a popular class of optimization methods. We show that if the disciplinary sensitivity information is implemented in a modular fashion, the transfer of sensitivity information among the formulations under study is straightforward. This enables not only experimentation with a variety of problem formations in a research environment, but also the flexible use of formulations in a production design environment.

Alexandrov, Natalie M.↗
NASA NTRS1992

Sub-domain decomposition methods and computational controls for multibody dynamical systems

This paper presents a concurrent methodology to simulate the dynamics of flexible multibody systems with a large number of degrees of freedom. A general class of open-loop structures is treated and a redundant coordinate formulation is adopted. A range space method is used in which the constraint forces are calculated using a preconditioned conjugate gradient method. By using a preconditioner motivated by the regular ordering of the directed graph of the structures, it is shown that the method is order N in the total number of coordinates of the system. The overall formulation has the advantage that it permits fine parallelization and does not rely on system topology to induce concurrency. It can be efficiently implemented on the present generation of parallel computers with a large number of processors. Validation of the method is presented via numerical simulations of space structures incorporating large number of flexible degrees of freedom.

Menon, R. G.↗
NASA NTRS2001

Development of an Innovative Algorithm for Aerodynamics-Structure Interaction Using Lattice Boltzmann Method

The lattice Boltzmann equation (LBE) is a kinetic formulation which offers an alternative computational method capable of solving fluid dynamics for various systems. Major advantages of the method are owing to the fact that the solution for the particle distribution functions is explicit, easy to implement, and the algorithm is natural to parallelize. In this final report, we summarize the works accomplished in the past three years. Since most works have been published, the technical details can be found in the literature. Brief summary will be provided in this report. In this project, a second-order accurate treatment of boundary condition in the LBE method is developed for a curved boundary and tested successfully in various 2-D and 3-D configurations. To evaluate the aerodynamic force on a body in the context of LBE method, several force evaluation schemes have been investigated. A simple momentum exchange method is shown to give reliable and accurate values for the force on a body in both 2-D and 3-D cases. Various 3-D LBE models have been assessed in terms of efficiency, accuracy, and robustness. In general, accurate 3-D results can be obtained using LBE methods. The 3-D 19-bit model is found to be the best one among the 15-bit, 19-bit, and 27-bit LBE models. To achieve desired grid resolution and to accommodate the far field boundary conditions in aerodynamics computations, a multi-block LBE method is developed by dividing the flow field into various blocks each having constant lattice spacing. Substantial contribution to the LBE method is also made through the development of a new, generalized lattice Boltzmann equation constructed in the moment space in order to improve the computational stability, detailed theoretical analysis on the stability, dispersion, and dissipation characteristics of the LBE method, and computational studies of high Reynolds number flows with singular gradients. Finally, a finite difference-based lattice Boltzmann method is developed for inviscid compressible flows.

Mei, Ren-Wei↗
NASA NTRS1988

Software engineering and Ada (Trademark) training: An implementation model for NASA

The choice of Ada for software engineering for projects such as the Space Station has resulted in government and industrial groups considering training programs that help workers become familiar with both a software culture and the intricacies of a new computer language. The questions of how much time it takes to learn software engineering with Ada, how much an organization should invest in such training, and how the training should be structured are considered. Software engineering is an emerging, dynamic discipline. It is defined by the author as the establishment and application of sound engineering environments, tools, methods, models, principles, and concepts combined with appropriate standards, guidelines, and practices to support computing which is correct, modifiable, reliable and safe, efficient, and understandable throughout the life cycle of the application. Neither the training programs needed, nor the content of such programs, have been well established. This study addresses the requirements for training for NASA personnel and recommends an implementation plan. A curriculum and a means of delivery are recommended. It is further suggested that a knowledgeable programmer may be able to learn Ada in 5 days, but that it takes 6 to 9 months to evolve into a software engineer who uses the language correctly and effectively. The curriculum and implementation plan can be adapted for each NASA Center according to the needs dictated by each project.

Legrand, Sue↗
NASA NTRS2004

Deep Moonquakes: Remaining Problems

We have recently reexamined more than 9000 United States previously unidentified seismic events catalogued during the Apollo landing missions and positively identified for the first time about 30 deep moonquake nests on the far side of the Moon. Although only a few of them are currently locatable, the relative arrival times among stations for the rest and presence or absence of seismic signals at particular stations suggest that either (a) the region within about $40\deg$ of the antipode is aseismic or (b) the deep interior of the Moon severely attenuates or deflects seismic waves. Aside from the obvious question of how to distinguish between such hypothetical models, this effort raised several more general questions concerning the use of deep moonquake signals to infer the structure and dynamics of the deep interior of the Moon. Among more important ones are: (1) How reliable are the seismic arrival picks from which to compute the seismic velocity variations in the Moon? (2) How do the possible lateral variations in seismic velocity affect the computed radial variation in seismic velocity at depth? (3) Can we tell more about the distribution and mechanism of deep moonquakes from the newly expanded database of identified deep moonquakes? Questions (1) and (2) are especially important because the inferred deep internal structure of the Moon depends critically on their answers. Answering these questions may demand additional data collected on future lunar missions, but some may be resolved with further examination of the existing data.

Nakamura, Y.↗
NASA NTRS1990

Construction of dynamic stochastic simulation models using knowledge-based techniques

Over the past three decades, computer-based simulation models have proven themselves to be cost-effective alternatives to the more structured deterministic methods of systems analysis. During this time, many techniques, tools and languages for constructing computer-based simulation models have been developed. More recently, advances in knowledge-based system technology have led many researchers to note the similarities between knowledge-based programming and simulation technologies and to investigate the potential application of knowledge-based programming techniques to simulation modeling. The integration of conventional simulation techniques with knowledge-based programming techniques is discussed to provide a development environment for constructing knowledge-based simulation models. A comparison of the techniques used in the construction of dynamic stochastic simulation models and those used in the construction of knowledge-based systems provides the requirements for the environment. This leads to the design and implementation of a knowledge-based simulation development environment. These techniques were used in the construction of several knowledge-based simulation models including the Advanced Launch System Model (ALSYM).

Williams, M. Douglas↗
NASA NTRS2006

Integrated Modeling of Advanced Opto-Mechanical Systems

The design of optical hardware for space applications is particularly challenging when developing high performance, novel systems that have no precedent. Integrated modeling and analysis of such opto-mechanical systems seeks to describe the end-to-end performance of the hardware using mission-relevant metrics. This multidisciplinary analysis might start with thermal disturbances from observation maneuvers, compute the system temperatures, compute the distorted positions and shapes of the hardware and compute the resulting optical performance. Dynamic disturbances such as reaction wheel imbalance or inertia imbalance of optical delay lines might be applied to a structural dynamic model and used in a guidance and control analysis. Mission-relevant science metrics might include wavefront quality, pointing error or imaging stability. Assembling a tool chain that can be both nimble and effective when scaled to the high fidelity models of detail design has been challenging. An integrated thermal, mechanical and optical analysis capability suitable for detail design has been developed and verified through experimental measurement. This capability was used in the design of flight-like breadboard hardware and development of a test apparatus that established both the level of performance of the hardware and the validity of the analysis. The analysis includes prediction of the thermal environment of the test chamber, detailed temperature distributions on the breadboard hardware, fine scale deformations of the optical elements, and computation of the wavefront quality using geometric optics. A battery of tests were conducted to assess the experiment data acquisition, measurement and control system and to establish the performance of the hardware design and accuracy of the integrated modeling. Thermal loads that represent operational observing maneuvers were imposed and the hardware optical performance was measured and compared to analytical predictions.

optomechanical analysis↗
NASA NTRS1980

A symmetric modal formulation of fluid-structure interaction, including a static approximation to higher order fluid modes

A method of fluid-structure coupling which provides symmetrical matrix equations of standard form solved by existing finite element computer programs is presented. The method postulates that the uncoupled vibration modes of the fluid or the structure be calculated before the coupled analysis. A numerical solution of vibration modes in an axisymmetric container demonstrated that a static approximation to higher order fluid modes can improve the accuracy of dynamic response computations using modal methods.

Macneal, R. H.↗
NASA NTRS1992

Adaptive methods in computational fluid dynamics

A review is conducted of the basic components of adaptive methods applicable to very complex problems in fluid dynamics. Attention is given to ways of changing the structure of an approximation to reduce error, techniques for estimating the evolution of error in a CFD calculation, and the range of algorithms that are currently available for mesh-changing functions. Available numerical results which demonstrate the viability of these approaches are discussed.

Oden, J. T.↗
NASA NTRSDate not supplied

Development of Slat-gap and Slat-cove Filler Treatments for Noise Reduction Assessment on the High Lift Common Research Model in the NASA LaRC 14x22

Airframe noise is an important issue during the approach and landing phases of flight because engines are throttled back, and airframe sources become an equal or greater contributor to environmental noise. The leading-edge slat component of the high-lift system for transport aircraft has been identified as a prominent source of airframe noise. Noise production mechanisms and potential treatments to mitigate airframe noise have been areas of active research for nearly three decades. Two promising technologies for slat noise reduction are the slat-gap filler (SGF) and slat-cove filler (SCF). Previous work was done using a 2D section of a transport class aircraft wing to demonstrate their feasibility via benchtop and computational models. A wind tunnel test campaign was recently undertaken to test the SGF and SCF technologies in a flight-like environment by installing dynamically scaled treatments on the 10%-scale High-Lift Common Research Model (CRM-HL), which is representative of a commercial twin-aisle transport aircraft. Advancement of the SGF and SCF technologies to overcome challenges of integration with 3D airframe structures, computational simulations of the CRM-HL predicting the aerodynamic and aeroacoustic performance and structural loads, and design of wind tunnel model hardware with features accommodating noise treatments were conducted in parallel. Details of innovations in the SGF and SCF technologies for 3D airframe feasibility will be described. The loads the treatments must sustain in flight and the influence of those loads on the design is also discussed. Finally, the design of wing leading-edge assemblies to treat the 10% CRM-HL with dynamically scaled SGF and SCF components is presented. The treatments were successfully tested in 2020/2021 providing a demonstration of leading-edge noise reduction using components that would allow slat articulation.

airframe noise reduction↗
NASA NTRS1993

Integrated modeling of advanced optical systems

This poster session paper describes an integrated modeling and analysis capability being developed at JPL under funding provided by the JPL Director's Discretionary Fund and the JPL Control/Structure Interaction Program (CSI). The posters briefly summarize the program capabilities and illustrate them with an example problem. The computer programs developed under this effort will provide an unprecedented capability for integrated modeling and design of high performance optical spacecraft. The engineering disciplines supported include structural dynamics, controls, optics and thermodynamics. Such tools are needed in order to evaluate the end-to-end system performance of spacecraft such as OSI, POINTS, and SMMM. This paper illustrates the proof-of-concept tools that have been developed to establish the technology requirements and demonstrate the new features of integrated modeling and design. The current program also includes implementation of a prototype tool based upon the CAESY environment being developed under the NASA Guidance and Control Research and Technology Computational Controls Program. This prototype will be available late in FY-92. The development plan proposes a major software production effort to fabricate, deliver, support and maintain a national-class tool from FY-93 through FY-95.

Briggs, Hugh C.↗
NASA NTRS1991

Thermally-induced structural dynamic response of flexural configurations influenced by linear/non-linear thermal effects

The thermally-induced strucural dynamic response of flexural configurations influenced by linear/nonlinear thermal effects is presented in conjunction with 'unified' transient approaches for effectively tackling this class of interdisciplinary problems. For illustrative purposes, the flexural structural models are assumed to be of the Euler-Bernoulli type. The purpose of the present paper is to not only provide an understanding of the influence of general linear/nonlinear thermal effects on flexural configurations, but also to provide to the analyst effective computational tools which help preserve a unified technology for the interdisciplinary areas encompassing structural mechanics/dynamics and thermal sciences. Several numerical test models illustrate the representative thermally-induced structural dynamic response of flexural configurations subjected to general linear/nonlinear temperature effects.

Namburu, Raju R.↗