Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Dynamic loading”

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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Controllability of Free-piston Stirling Engine/linear Alternator Driving a Dynamic Load

This paper presents the dynamic behavior of a Free-Piston Stirling Engine/linear alternator (FPSE/LA) driving a single-phase fractional horse-power induction motor. The controllability and dynamic stability of the system are discussed by means of sensitivity effects of variations in system parameters, engine controller, operating conditions, and mechanical loading on the induction motor. The approach used expands on a combined mechanical and thermodynamic formulation employed in a previous paper. The application of state-space technique and frequency domain analysis enhances understanding of the dynamic interactions. Engine-alternator parametric sensitivity studies, similar to those of the previous paper, are summarized. Detailed discussions are provided for parametric variations which relate to the engine controller and system operating conditions. The results suggest that the controllability of a FPSE-based power system is enhanced by proper operating conditions and built-in controls.

Kankam, M. David↗
NASA NTRS2003

CFD-based Design of LOX Pump Inlet Duct for Reduced Dynamic Loads

Numerical simulations have been completed for a variety of designs for a 90 deg elbow duct. The objective is to identify a design that minimizes the dynamic load entering a LOX turbopump located at the elbow exit. Designs simulated to date indicate that simpler duct geometries result in lower losses. Benchmark simulations have verified that the compressible flow code used in this study is applicable to these incompressible flow simulations.

Rothermel, Jeffry↗
NASA NTRS2003

CFD-Based Design of Turbopump Inlet Duct for Reduced Dynamic Loads

Numerical simulations have been completed for a variety of designs for a 90 deg elbow duct. The objective is to identify a design that minimizes the dynamic load entering a LOX turbopump located at the elbow exit. Designs simulated to date indicate that simpler duct geometries result in lower losses. Benchmark simulations have verified that the compressible flow codes used in this study are applicable to these incompressible flow simulations.

Rothermel, Jeffry↗
NASA NTRS1979

Dynamic loads analysis system (DYLOFLEX) summary. Volume 1: Engineering formulation

The DYLOFLEX computer program system expands the aeroelastic cycle from that in the FLEXSTAB computer program system to include dynamic loads analyses involving active controls. Two aerodynamic options exist within DYLOFLEX. The analyst can formulate the problem with unsteady aerodynamics calculated using the doublet lattice method or with quasi-steady aerodynamics formulated from either FLEXSTAB or doublet lattice steady state aerodynamics with unsteady effects approximated by indicial lift growth functions. The equations of motion are formulated assuming straight and level flight and small motions. Loads are calculated using the force summation technique. DYLOFLEX consists of nine standalone programs which can be linked with each other by magnetic files used to transmit the required data between programs.

Miller, R. D.↗
NASA NTRS1973

Dynamic loading of aircraft surfaces due to jet exhaust impingement

High-lift wing concepts being considered for application to commercial STOL transports are discussed. The flow patterns which produce dynamic loads on these wings are indicated. Measurements of surface pressure and acceleration on a one-half-scale model of an externally blown double-slotted flap are reported. Root-mean-square values, power spectra, and scaling parameters are shown.

Lansing, D. L.↗
NASA NTRS1987

On dynamic loads in parallel shaft transmissions. 1: Modelling and analysis

A model of a simple parallel-shaft, spur-gear transmission is presented. The model is developed to simulate dynamic loads in power transmissions. Factors affecting these loads are identified. Included are shaft stiffness, local compliance due to contact stress, load sharing, and friction. Governing differential equations are developed and a solution procedure is outlined. A parameter study of the solutions is presented in NASA TM-100181 (AVSCOM TM-87-C-3).

Lin, Edward Hsiang-Hsi↗
NASA NTRS1979

Capabilities and applications of a computer program system for dynamic loads analyses of flexible airplanes with active controls /DYLOFLEX/

This paper describes and illustrates the capabilities of the DYLOFLEX Computer Program System. DYLOFLEX is an integrated system of computer programs for calculating dynamic loads of flexible airplanes with active control systems. A brief discussion of the engineering formulation for each of the nine DYLOFLEX programs is described. The capabilities of the system are illustrated by the analyses of two example configurations.

Perry, B., III↗
NASA NTRS1995

Multithreaded Model for Dynamic Load Balancing Parallel Adaptive PDE Computations

We present a multithreaded model for the dynamic load-balancing of numerical, adaptive computations required for the solution of Partial Differential Equations (PDE's) on multiprocessors. Multithreading is used as a means of exploring concurrency in the processor level in order to tolerate synchronization costs inherent to traditional (non-threaded) parallel adaptive PDE solvers. Our preliminary analysis for parallel, adaptive PDE solvers indicates that multithreading can be used an a mechanism to mask overheads required for the dynamic balancing of processor workloads with computations required for the actual numerical solution of the PDE's. Also, multithreading can simplify the implementation of dynamic load-balancing algorithms, a task that is very difficult for traditional data parallel adaptive PDE computations. Unfortunately, multithreading does not always simplify program complexity, often makes code re-usability not an easy task, and increases software complexity.

Chrisochoides, Nikos↗
NASA NTRS1978

Automated time-resolved data acquisition during static and dynamic loading of composite materials

This paper reports the development of two new nondestructive techniques for precise determination of the nature and extent of complex damage and the consequent redistribution of stress in composite materials during quasi-static and cyclic or dynamic loading. The two methods incorporate video-thermography and four-component tensor elastic modulus determination. The experimental and analytical aspects of these two methods are discussed and data is presented.

Reifsnieder, K. L.↗
NASA NTRS1987

Visual display and alarm system for wind tunnel static and dynamic loads

A wind tunnel balance monitor and alarm system developed at NASA Ames Research Center will produce several beneficial results. The costs of wind tunnel delays because of inadvertent balance damage and the costs of balance repair or replacement can be greatly reduced or eliminated with better real-time information on the balance static and dynamic loading. The wind tunnel itself will have enhanced utility with the elimination of overly cautious limits on test conditions. The microprocessor-based system features automatic scaling and 16 multicolored LED bargraphs to indicate both static and dynamic components of the signals from eight individual channels. Five individually programmable alarm levels are available with relay closures for internal or external visual and audible warning devices and other functions such as automatic activation of external recording devices, model positioning mechanisms, or tunnel shutdown.

Hanly, Richard D.↗
NASA NTRS1987

Visual display and alarm system for wind tunnel static and dynamic loads

A wind tunnel balance monitor and alarm system developed at NASA Ames Research Center will produce several beneficial results. The costs of wind tunnel delays because of inadvertent balance damage and the costs of balance repair or replacement can be greatly reduced or eliminated with better real-time information on the balance static and dynamic loading. The wind tunnel itself will have enhanced utility with the elimination of overly cautious limits on test conditions. The microprocessor-based system features automatic scaling and 16 multicolored LED bargraphs to indicate both static and dynamic components of the signals from eight individual channels. Five individually programmable alarm levels are available with relay closures for internal or external visual and audible warning devices and other functions such as automatic activation of external recording devices, model positioning mechanism, or tunnel shutdown.

Hanly, Richard D.↗
NASA NTRS1976

Results of tests CS4 and CS5 to investigate dynamic loads and pressures on 0.03-scale models (Ax1319-3/4 and 45-0) of mated 747 cam and space shuttle orbiter in the Boeing transonic wind tunnel

A 0.03-scale model of the 747 CAM/Orbiter was tested in an 8 x 12 foot transonic wind tunnel. Dynamic loads, pressure, and empennage flow field data were obtained using pressure transducers, strain gages, and a split film anemometer. The test variables included Mach number, angle of attack, sideslip angle, orbiter tailcone on and off, orbiter partial tailcone, orbiter nozzle air scoops, orbiter body flap angle, and orbiter elevon angle.

Source record↗
NASA NTRS1994

Dynamic Load Balancing for Finite Element Calculations on Parallel Computers

Computational requirements of full scale computational fluid dynamics change as computation progresses on a parallel machine. The change in computational intensity causes workload imbalance of processors, which in turn requires a large amount of data movement at runtime. If parallel CFD is to be successful on a parallel or massively parallel machine, balancing of the runtime load is indispensable. Here a frame work is presented for dynamic load balancing for CFD applications, called Jove. One processor is designated as a decision maker Jove while others are assigned to computational fluid dynamics. Processors running CFD send flags to Jove in a predetermined number of iterations to initiate load balancing. Jove starts working on load balancing while other processors continue working with the current data and load distribution. Jove goes through several steps to decide if the new data should be taken, including preliminary evaluate, partition, processor reassignment, cost evaluation, and decision. Jove running on a single SP2 node has been completely implemented. Preliminary experimental results show that the Jove approach to dynamic load balancing can be effective for full scale grid partitioning on the target machine SP2.

Pramono, Eddy↗
NASA NTRSDate not supplied

Crashworthiness of a Lift Plus Cruise eVTOL Vehicle Design within Dynamic Loading Environments

To aid in the development of electric Vertical Take-off and Landing (eVTOL) technology, the National Aeronautics and Space Administration has undertaken research initiatives to evaluate and optimize design features of eVTOL aircraft. One such initiative has been to develop energy attenuating design mechanisms to improve eVTOL vehicle crashworthiness. In this study, crashworthiness design mechanisms, implemented within a six-passenger lift plus cruise (LPC) eVTOL concept vehicle, were evaluated under multi-axis dynamic loading conditions. This work builds upon crashworthiness design concepts previously optimized within a simplified vehicle-loading environment. The results of this study found the effectiveness of energy attenuating design mechanisms to be dependent on the complexity of load environment in which they were employed. An increase in off-axis loading resulted in a decrease in occupant protective capability. These results indicate the necessity for evaluating vehicle design across the range of possible dynamic impact conditions to characterize crashworthiness. This work provides preliminary methodology for implementing energy attenuating design mechanisms and evaluating crashworthiness for future UAM markets.

Jacob Putnam↗
NASA NTRS1986

A comparative analysis of static and dynamic load balancing strategies

The problem of uniformly distributing the load of a parallel program over a multiprocessor system was considered. A program was analyzed whose structure permits the computation of the optimal static solution. Then four strategies for load balancing were described and their performance compared. The strategies are: (1) the optimal static assignment algorithm which is guaranteed to yield the best static solution, (2) the static binary dissection method which is very fast but suboptimal, (3) the greedy algorithm, a static fully polynomial time approximation scheme, which estimates the optimal solution to arbitrary accuracy, and (4) the predictive dynamic load balancing heuristic which uses information on the precedence relationships within the program and outperforms any of the static methods. It is also shown that the overhead incurred by the dynamic heuristic is reduced considerably if it is started off with a static assignment provided by either of the three strategies.

Iqbal, M. Ashraf↗
NASA NTRS1986

Performance tradeoffs in static and dynamic load balancing strategies

The problem of uniformly distributing the load of a parallel program over a multiprocessor system was considered. A program was analyzed whose structure permits the computation of the optimal static solution. Then four strategies for load balancing were described and their performance compared. The strategies are: (1) the optimal static assignment algorithm which is guaranteed to yield the best static solution, (2) the static binary dissection method which is very fast but sub-optimal, (3) the greedy algorithm, a static fully polynomial time approximation scheme, which estimates the optimal solution to arbitrary accuracy, and (4) the predictive dynamic load balancing heuristic which uses information on the precedence relationships within the program and outperforms any of the static methods. It is also shown that the overhead incurred by the dynamic heuristic is reduced considerably if it is started off with a static assignment provided by either of the other three strategies.

Iqbal, M. A.↗
NASA NTRS1991

On the numerical solution of the dynamically loaded hydrodynamic lubrication of the point contact

A numerical transient solution of the hydrodynamically lubricated point contact problem is obtained using the ball-on-plane model. Results, which include the variation of the minimum film thickness and phase-lag with time as functions of excitation frequency, are compared with the analytic solution of the transient step bearing problem with the same dynamic loading function.

Lim, Sang G.↗