Pressure-loads produced on a flat-plate wing by rocket jets exhausting in a spanwise direction below the wing and perpendicular to a free-stream flow of Mach number 2.0
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Falanga, Ralph A↗
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Stream Flow Prediction by Remote Sensing and Genetic Programming
A genetic programming (GP)-based, nonlinear modeling structure relates soil moisture with synthetic-aperture-radar (SAR) images to present representative soil moisture estimates at the watershed scale. Surface soil moisture measurement is difficult to obtain over a large area due to a variety of soil permeability values and soil textures. Point measurements can be used on a small-scale area, but it is impossible to acquire such information effectively in large-scale watersheds. This model exhibits the capacity to assimilate SAR images and relevant geoenvironmental parameters to measure soil moisture.
Chang, Ni-Bin↗
Acoustic tests of duct-burning turbofan jet noise simulation
The results of a static acoustic and aerodynamic performance, model-scale test program on coannular unsuppressed and multielement fan suppressed nozzle configurations are summarized. The results of the static acoustic tests show a very beneficial interaction effect. When the measured noise levels were compared with the predicted noise levels of two independent but equivalent conical nozzle flow streams, noise reductions for the unsuppressed coannular nozzles were of the order of 10 PNdB; high levels of suppression (8 PNdB) were still maintained even when only a small amount of core stream flow was used. The multielement fan suppressed coannular nozzle tests showed 15 PNdB noise reductions and up to 18 PNdB noise reductions when a treated ejector was added. The static aerodynamic performance tests showed that the unsuppressed coannular plug nozzles obtained gross thrust coefficients of 0.972, with 1.2 to 1.7 percent lower levels for the multielement fan-suppressed coannular flow nozzles. For the first time anywhere, laser velocimeter velocity profile measurements were made on these types of nozzle configurations and with supersonic heated flow conditions. Measurements showed that a very rapid decay in the mean velocity occurs for the nozzle tested.
Knott, P. R.↗
The effect of inflow velocity profiles on the performance of supersonic ejector nozzles
The design of supersonic nozzles is becoming increasingly complex as conflicting requirements for low noise, higher efficiency, and wider operating range are driving the designer toward more variable geometry and multiple stream flows. Analysis techniques must be modified and expanded to take into account these additional complexities and still retain the rapid computational rate necessary for optimization and design studies. A nozzle analysis must handle more flow streams, more complex geometries, and more highly distorted initial profiles. This paper discusses some modifications to a method for calculating the performance characteristics of supersonic ejector nozzles and demonstrates the improvement in results the modifications provide.
Bishop, A. R.↗
Microwave Sterilization and Depyrogenation System
A fully functional, microgravity-compatible microwave sterilization and depyrogenation system (MSDS) prototype was developed that is capable of producing medical-grade water (MGW) without expendable supplies, using NASA potable water that currently is available aboard the International Space Station (ISS) and will be available for Lunar and planetary missions in the future. The microwave- based, continuous MSDS efficiently couples microwaves to a single-phase, pressurized, flowing water stream that is rapidly heated above 150 C. Under these conditions, water is rapidly sterilized. Endotoxins, significant biological toxins that originate from the cell walls of gram-negative bacteria and which represent another defining MGW requirement, are also deactivated (i.e., depyrogenated) albeit more slowly, with such deactivation representing a more difficult challenge than sterilization. Several innovations culminated in the successful MSDS prototype design. The most significant is the antenna-directed microwave heating of a water stream flowing through a microwave sterilization chamber (MSC). Novel antenna designs were developed to increase microwave transmission efficiency. These improvements resulted in greater than 95-percent absorption of incident microwaves. In addition, incorporation of recuperative heat exchangers (RHxs) in the design reduced the microwave power required to heat a water stream flowing at 15 mL/min to 170 C to only 50 W. Further improvements in energy efficiency involved the employment of a second antenna to redirect reflected microwaves back into the MSC, eliminating the need for a water load and simplifying MSDS design. A quick connect (QC) is another innovation that can be sterilized and depyrogenated at temperature, and then cooled using a unique flow design, allowing collection of MGW at atmospheric pressure and 80 C. The final innovation was the use of in-line mixers incorporated in the flow path to disrupt laminar flow and increase contact time at a given flow rate. These technologies can be employed in small-scale systems for efficient production of MGW in the laboratory or in a range of larger systems that meet various industrial requirements. The microwave antennas can also be adapted to selectively sterilize vulnerable connections to ultra-pure water production facilities or biologically vulnerable systems where microorganisms may intrude.
Akse, James R.↗
Application of remotely sensed land-use information to improve estimates of streamflow characteristics, volume 8
The author has identified the following significant results. Land use data derived from high altitude photography and satellite imagery were studied for 49 basins in Delaware, and eastern Maryland and Virginia. Applying multiple regression techniques to a network of gaging stations monitoring runoff from 39 of the basins, demonstrated that land use data from high altitude photography provided an effective means of significantly improving estimates of stream flow. Forty stream flow characteristic equations for incorporating remotely sensed land use information, were compared with a control set of equations using map derived land cover. Significant improvement was detected in six equations where level 1 data was added and in five equations where level 2 information was utilized. Only four equations were improved significantly using land use data derived from LANDSAT imagery. Significant losses in accuracy due to the use of remotely sensed land use information were detected only in estimates of flood peaks. Losses in accuracy for flood peaks were probably due to land cover changes associated with temporal differences among the primary land use data sources.
Pluhowski, E. J.↗
Flow-swallowing enthalpy probes in low-density plasma streams.
Flow swallowing enthalpy probes for low density plasma gas flows in constricted arc heated facility, discussing attached shock system
Anderson, L. A.↗
Two-Phase Quality/Flow Meter
A quality and/or flow meter employs a capacitance probe assembly for measuring the dielectric constant of flow stream, particularly a two-phase flow stream including liquid and gas components.ne dielectric constant of the flow stream varies depending upon the volume ratios of its liquid and gas components, and capacitance measurements can therefore be employed to calculate the quality of the flow, which is defined as the volume ratio of liquid in the flow to the total volume ratio of gas and liquid in the flow. By using two spaced capacitance sensors, and cross-correlating the time varying capacitance values of each, the velocity of the flow stream can also be determined. A microcontroller-based processing circuit is employed to measure the capacitance of the probe sensors.The circuit employs high speed timer and counter circuits to provide a high resolution measurement of the time interval required to charge each capacitor in the probe assembly. In this manner, a high resolution, noise resistant, digital representation of each of capacitance value is obtained without the need for a high resolution A/D converter, or a high frequency oscillator circuit. One embodiment of the probe assembly employs a capacitor with two ground plates which provide symmetry to insure that accurate measurements are made thereby.
Moerk, J. Steven↗
Resonance and Tones in Dual-Stream Nozzle Flows
A dual-stream nozzle configuration was studied numerically with the objective of predicting the appearance of tones and study their sources. It was found that some of the tones traced to a coupling between Strouhal shedding from the struts, which held different pieces of the nozzle together, and various duct acoustic modes. A focus of the work was on exploring the nature of the duct modes. First, elements of the numerical procedure were studied for a 4-strut nozzle, validating the results with existing experimental data. The approach was then applied to a 3-strut geometry and four different excitation methods. The predicted tones and associated duct modes are analyzed in detail.
Milanovic, Ivana↗
Enthalpy and stagnation temperature determination of a high temperature laminar flow gas stream Patent
Measuring conductive heat flow and thermal conductivity of laminar gas stream in cylindrical plug to simulate atmospheric reentry
Glawe, G. E.↗
Analytical and experimental investigations of a jet exhausting into an oncoming supersonic stream.
Flow field for single or multiple jets firing forward into oncoming supersonic free stream, noting effect of forward extending cylindrical body
Bender, R. L.↗
Numerical methods in laminar and turbulent flow; Proceedings of the 7th International Conference, Stanford Univ., CA, July 15-19, 1991. Vol. 7, pts. 1 & 2
Consideration is given to the impulse response of a laminar boundary layer and receptivity; numerical transition to turbulence in plane Poiseuille flow; large eddy simulation of turbulent wake flow; a viscous model and loss calculation of a multisplitter cascade; vortex initiation during dynamic stall of an airfoil; a numerical analysis of isothermal flow in a combustion chamber; and compressible flow calculations with a two-equation turbulence model and unstructured grids. Attention is also given to a 2D calculation of a buoyant flow around a burning sphere, a fast multigrid method for 3D turbulent incompressible flows, a streaming flow induced by an oscillating cascade of circular cylinders, an algebraic multigrid scheme for solving the Navier-Stokes equations on unstructured meshes; and nonlinear coupled multigrid solutions to thermal problems employing different nodal grid arrangements and convective transport approximations.
Taylor, C.↗
Capacitance probe for fluid flow and volume measurements
Method and apparatus for making measurements on fluids are disclosed, including the use of a capacitive probe for measuring the flow volume of a material within a flow stream. The capacitance probe has at least two elongate electrodes and, in a specific embodiment of the invention, has three parallel elongate electrodes with the center electrode being an extension of the center conductor of a co-axial cable. A conductance probe is also provided to provide more accurate flow volume data in response to conductivity of the material within the flow stream. A preferred embodiment of the present invention provides for a gas flow stream through a microgravity environment that allows for monitoring a flow volume of a fluid sample, such as a urine sample, that is entrained within the gas flow stream.
Arndt, G. Dickey↗
The preparation of calcium superoxide in a flowing gas stream and fluidized bed
Superoxides can be used as sources of chemically stored oxygen in emergency breathing apparatus. The work reported here describes the use of a low-pressure nitrogen gas sweep through the reactant bed, for temperature control and water vapor removal. For a given set of gas temperature, bed thickness, and reaction time values, the highest purity calcium superoxide, Ca(O2)2, was obtained at the highest space velocity of the nitrogen gas sweep. The purity of the product was further increased by flow conditions that resulted in the fluidization of the reactant bed. However, scale-up of the low-pressure fluidized bed process was limited to the formation of agglomerates of reactant particles, which hindered thermal control by the flowing gas stream. A radiofrequency flow discharge inside the reaction chamber prevented agglomeration, presumably by dissipation of the static charges on the fluidized particles.
Wood, P. C.↗
Capacitance Probe for Fluid Flow and Volume Measurements
Method and apparatus for making measurements on fluids are disclosed, including the use of a capacitive probe for measuring the flow volume of a material within a flow stream. The capacitance probe has at least two elongate electrodes and, in a specific embodiment of the invention, has three parallel elongate electrodes with the center electrode being an extension of the center conductor of a co-axial cable. A conductance probe is also provided to provide more accurate flow volume data in response to conductivity of the material within the flow stream. A preferred embodiment of the present invention provides for a gas flow stream through a micro-gravity environment that allows for monitoring a flow volume of a fluid sample, such as a urine sample, that is entrained within the gas flow stream.
Arndt, G. Dickey↗
Evaluating LSM-Based Water Budgets Over a West African Basin Assisted with a River Routing Scheme
Within the framework of the African Monsoon Multidisciplinary Analysis (AMMA) Land Surface Model Intercomparison Project phase 2 (ALMIP-2), this study evaluates the water balance simulated by the Interactions between Soil, Biosphere, and Atmosphere (ISBA) over the upper Oum River basin, in Benin, using a mesoscale river routing scheme (RRS). The RRS is based on the nonlinear Muskingum Cunge method coupled with two linear reservoirs that simulate the time delay of both surface runoff and base flow that are produced by land surface models. On the basis of the evidence of a deep water-table recharge in that region,a reservoir representing the deep-water infiltration (DWI) is introduced. The hydrological processes of the basin are simulated for the 2005-08 AMMA field campaign period during which rainfall and stream flow data were intensively collected over the study area. Optimal RRS parameter sets were determined for three optimization experiments that were performed using daily stream flow at five gauges within the basin. Results demonstrate that the RRS simulates stream flow at all gauges with relative errors varying from -22% to 3% and Nash-Sutcliffe coefficients varying from 0.62 to 0.90. DWI varies from 24% to 67% of the base flow as a function of the sub-basin. The relatively simple reservoir DWI approach is quite robust, and further improvements would likely necessitate more complex solutions (e.g., considering seasonality and soil type in ISBA); thus, such modifications are recommended for future studies. Although the evaluation shows that the simulated stream flows are generally satisfactory, further field investigations are necessary to confirm some of the model assumptions.
Multidisciplinary↗
Role of Vibration-Induced Streaming in Float-Zone Crystal Growth
This presentation will examine in detail the role of vibration-induced streaming flow in the context of float-zone crystal growth. It is very well known that during float-zone materials processing, the naturally occurring temperature gradients along the zone surface impose a thermocapillary flow in the zone. Under certain processing conditions, the thermocapillary flow can also become nonsteady (oscillatory). The presence of thermocapillary flow is detrimental to crystal quality, for it can promote non-uniform dopant distribution and crystal striations. To null this effect we have imposed a counter streaming flow in the zone, via end-wall vibration. This technique has been adapted to float-zone processing of Sodium Nitrate-Barium Nitrate eutectic alloys, under both steady and nonsteady thermocapillary flow conditions. The beneficial effects of counter streaming flow have been clearly brought out through the before and after comparisons of the crystal microstructure. In addition, we are also examining the theoretical underpinnings of the balancing of thermocapillary flows with vibration-driven counter flows in float-zones.
Anilkumar, A. V.↗
Role of Vibration-Induced Streaming in Float-Zone Crystal Growth
This presentation will examine in detail the role of vibration-induced streaming flow in the context of float-zone crystal growth. It is very well known that during float-zone materials processing, the naturally occurring temperature gradients along the zone surface impose a thermocapillary flow in the zone. Under certain processing conditions, the thermocapillary flow can also become nonsteady (oscillatory). The presence of thermocapillary flow is detrimental to crystal quality, for it can promote non-uniform dopant distribution and crystal striations. To null this effect we have imposed a counter streaming flow in the zone, via end-wall vibration. This technique has been adapted to float-zone processing of Sodium Nitrate-Barium Nitrate eutectic alloys, under both steady and nonsteady thermocapillary flow conditions. The beneficial effects of counter streaming flow have been clearly brought out through the before and after comparisons of the crystal microstructure. In addition, we are also examining the theoretical underpinnings of the balancing of thermocapillary flows with vibration-driven counter flows in float-zones.
Anikumar, A. V.↗