An implicit finite difference approximation to the one-dimensional transport equation

The properties of an implicit three-level finite difference scheme are investigated. The modified equivalent partial differential equation is used to determine the speed and amplitude characteristics of the scheme, and these are used to determine the optimal value of the weighting between a central difference and an upwind biased difference. Results of numerical experiments that confirm that the predicted value of the weight does minimise the error are presented

MODELING OF A GAS LEAKAGE INCLUDING DROPLET TRANSPORT

ABSTRACT Safety assessment of compressed gas storage and pipeline facilities has to consider accidental leaks to the atmosphere. A major concem for modelling of such accidental leaks is the phase change behaviour of the compressed (liquid) gas. The present study assumes that droplets of the liquid gas are present in the gas leak jet. The effect of the droplet concentration and diameter on the behaviour on the jet is studied using Computational Fluid Dynamics (CFD). The impact of these variables on local gas distribution is analysed and discussed

Calibration of Airframe and Occupant Models for Two Full-Scale Rotorcraft Crash Tests

Two full-scale crash tests of an MD-500 helicopter were conducted in 2009 and 2010 at NASA Langley's Landing and Impact Research Facility in support of NASA s Subsonic Rotary Wing Crashworthiness Project. The first crash test was conducted to evaluate the performance of an externally mounted composite deployable energy absorber under combined impact conditions. In the second crash test, the energy absorber was removed to establish baseline loads that are regarded as severe but survivable. Accelerations and kinematic data collected from the crash tests were compared to a system integrated finite element model of the test article. Results from 19 accelerometers placed throughout the airframe were compared to finite element model responses. The model developed for the purposes of predicting acceleration responses from the first crash test was inadequate when evaluating more severe conditions seen in the second crash test. A newly developed model calibration approach that includes uncertainty estimation, parameter sensitivity, impact shape orthogonality, and numerical optimization was used to calibrate model results for the second full-scale crash test. This combination of heuristic and quantitative methods was used to identify modeling deficiencies, evaluate parameter importance, and propose required model changes. It is shown that the multi-dimensional calibration techniques presented here are particularly effective in identifying model adequacy. Acceleration results for the calibrated model were compared to test results and the original model results. There was a noticeable improvement in the pilot and co-pilot region, a slight improvement in the occupant model response, and an over-stiffening effect in the passenger region. This approach should be adopted early on, in combination with the building-block approaches that are customarily used, for model development and test planning guidance. Complete crash simulations with validated finite element models can be used to satisfy crash certification requirements, thereby reducing overall development costs

Modelo geométrico para construir la ecuación de segundo grado

En este artículo1 se presentan una serie de reflexiones acerca de un trabajo de investigación en el aula realizado en el Centro Distrital John F. Kennedy. El tema de matemáticas sobre el que se centró la investigación fue la construcción de la expresión algebraica de una ecuación de segundo grado aplicando el concepto de área de un rectángulo. Hemos dividido la presentación del trabajo en dos partes. En la primera, se da cuenta de un diagnóstico en el que se indagó acerca del estado de conocimiento de los estudiantes con respecto al tema y también sobre algunas de sus características socio-económicas. En la segunda, se presenta el análisis curricular realizado alrededor del tema y cuyo propósito era apoyar la realización del diseño de una actividad de aula de noventa minutos. En los procesos anteriores se tuvieron en cuenta algunas pautas de análisis didáctico tales como proponer un modelo sobre la estructura matemática del tema, indagar sobre el conocimiento previo de los estudiantes acerca de los prerrequisitos necesarios para abordar el tema y la forma como usualmente se ha enfocado la enseñanza del tema en nuestro contexto

Design of a large scale flow-meter test and calibration facility

The design and set up of a large-scale flowmeter calibration and test facility is presented. The facility was designed to handle flowmeters with diameters between 6” and 14”, flow rates up to 0.3 m3/s and to give results less than 1% accurate. The calibration methodology consisted firstly in calibrating the pattern flowmeters, using volume and time primary measurements, and secondly, comparing the pattern to the flowmeters needing calibration. The design and calculation of the primary calibration device is addressed, including numerical simulations of the outflow manifold and the comparison to experimental data. The calibration facility proved to be accurate and reliable in producing renewed calibration data for various tested flowmeter

Design of a flow deflector for an accurate flow meter calibration facility

The design and test of a flow deflector gate used for controlling the flow deviation toward the primary tank in a flow-meter calibration facility is presented. The deflector gate is pneumatically controlled and permits the flow conduction to either the suction tank or to the primary tank. The deflector is designed to approximately compensate the flow deficit towards the primary tank during the opening, with the flow excess while in the shutting process. Numerical simulations are performed to study the flow hydrodynamics during the deflector operation. Results are compared to experimental data, and used to improve the gate design. The enhanced design proved to guarantee the uniformity of the flow through the calibration section and the dramatic reduction of the error in volume measurement during calibration

Design of a large scale flow-meter test and calibration facility

The design and set up of a large-scale flowmeter calibration and test facility is presented. The facility was designed to handle flowmeters with diameters between 6” and 14”, flow rates up to 0.3 m3/s and to give results less than 1% accurate. The calibration methodology consisted firstly in calibrating the pattern flowmeters, using volume and time primary measurements, and secondly, comparing the pattern to the flowmeters needing calibration. The design and calculation of the primary calibration device is addressed, including numerical simulations of the outflow manifold and the comparison to experimental data. The calibration facility proved to be accurate and reliable in producing renewed calibration data for various tested flowmeter