Diffusion with chemical reaction: An attempt to explain number density anomalies in experiments involving alkali vapor

The mutual diffusion of two reacting gases is examined which takes place in a bath of inert gas atoms. Solutions are obtained between concentric spheres, each sphere acting as a source for one of the reactants. The calculational model is used to illustrate severe number density gradients observed in absorption experiments with alkali vapor. Severe gradients result when sq root k/D R is approximately 5 where k, D, and R are respectively the second order rate constant, the multicomponent diffusion constant, and the geometrical dimension of the experiment

Apparatus for experimental investigation of aerodynamic radiation with absorption by ablation products

A description is given and calibration procedures are presented for an apparatus that is used to simulate aerodynamic radiant heating during planetary entry. The primary function of the apparatus is to simulate the spectral distribution of shock layer radiation and to determine absorption effects of simulated ablation products which are injected into the stagnation region flow field. An electric arc heater is used to heat gas mixtures that represent the planetary atmospheres of interest. Spectral measurements are made with a vacuum ultraviolet scanning monochromator

Investigation of light source and scattering medium related to vapor-screen flow visualization in a supersonic wind tunnel

Methods for increasing the radiant in light sheets used for vapor screen set-ups were investigated. Both high-pressure mercury arc lamps and lasers were considered. Pulsed operation of the air-cooled 1-kW lamps increased the light output but decreased reliability. An ellipsoidal mirror improved the output of the air-cooled lamps by concentrating the light but increased the complexity of the housing. Water-cooled-4-kW lamps coupled with high-aperture Fresnel lenses provided reasonable improvements over the air-cooled lamps. Fanned laser beams measurements of scattered light versus dew point made in conjunction with successful attempts to control the fluid injection. A number of smoke generators are described and test results comparing smoke and vapor screens are shown. Finally, one test included a periscope system to relay the image to a camera outside the flow

Recent flow visualization studies in the 0.3-m TCT

Light beams are altered by refractive index changes; flow induced refractive index changes provide the impetus for conventional visualization techniques such as schlieren and shadowgraph. Unfortunately effects related to the flow can be masked by refractive index inhomogeneities external to the test section. A simple shadowgraph scheme was used to assess the flow quality of the Langley 0.3 meter Transonic Cryogenic Tunnel. When the penetration tubes were evacuated the quality of the shadowgraph improved dramatically

Section properties for cellular decks subjected to negative bending

Cellular decks are formed by attaching cold-formed “hat-shaped” deck sections on top of cold-formed steel sheets. The attachment is typically made using resistance spot welds spaced at a specific interval. The void left underneath the deck flutes and above the steel sheet provides a convenient means for the distribution of wiring and data cables throughout building systems. The section properties of cellular decks subjected to positive bending can be determined using the provisions of Chapter B of the 2001 AISI Specification (AISI, 2001). However, the provisions of Chapter B do not apply to cellular decks subjected to negative bending unless a specific weld spacing requirement is met. This requirement, set by Section D1.2 Spacing of Connections in Compression Elements (AISI, 2001), limits weld spacing so as to completely prevent column-like buckling between welds and provide adequate resistance to horizontal shear forces. Using section D1.2 limits weld spacing to a range of 1 in. to 2 in. for most cellular decks. It is standard industry practice to space cellular deck welds at 4 in. to 8 in. on center, exceeding the limits of Section D1.2. If the spacing limits of Section D1.2 are exceeded, the 2001 AISI Specification requires that the steel sheet be neglected when determining the section properties of cellular deck in negative bending. This is done because column-like buckling is likely to occur in the sheet when it is subjected to compression forces. Although the 2001 AISI Specification has provisions in place to account for the effects of local buckling, it has no provisions in place to account for the post column-like buckling strength of the steel sheet. However, a procedure for determining the post-buckling strength of cellular decks was developed by Luttrell and Balaji (1992), and is based on the results of 82 negative bending tests performed on six cellular deck profiles. The procedure developed by Luttrell and Balaji (1992) utilizes a dimensional reduction factor, ρm, which is used to determine the effective width of the steel sheet when column-like buckling is an issue. The factors having the greatest influence on ρm include steel sheet thickness, steel sheet yield strength, weld spacing, and the depth of the deck. Although the method correlated well with the 82 bending tests performed, a ballot containing his method was not passed by AISI. The principal reason for its rejection was 2 that the reduction factor, ρm, was dimensional, which violates an AISI directive that all equations be non-dimensional so they apply to both US Standard and SI units. The primary objective of this research was to modify the method developed by Luttrell and Balaji such that the dimensional reduction factor is non-dimensional. Using Luttrell\u27s method, section properties for 49 of the 82 cellular decks tested in negative bending were determined. Section properties were not determined for the remaining 33 ECP266 and EPC3 cellular decks due to a lack of information with regard to the deck dimensions. However, a dimensionless reduction factor was developed based on the section properties of the EP-type cellular deck. The equation used to predict the reduction factor was optimized so as to reduce the error between observed and theoretical bending strength to a minimum

Seeing through flows in Langley's 0.3-meter Transonic Cryogenic Tunnel

Viewing problems associated with the measurement of model deformation in cryogenic wind tunnels are discussed. Tests were conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel to assess viewing capabilities thru the flow field. The effects of condensation and turbulent boundary layers are discussed and a modelling procedure for image degradation is described

Video model deformation system for the National Transonic Facility

A photogrammetric closed circuit television system to measure model deformation at the National Transonic Facility is described. The photogrammetric approach was chosen because of its inherent rapid data recording of the entire object field. Video cameras are used to acquire data instead of film cameras due to the inaccessibility of cameras which must be housed within the cryogenic, high pressure plenum of this facility. A rudimentary theory section is followed by a description of the video-based system and control measures required to protect cameras from the hostile environment. Preliminary results obtained with the same camera placement as planned for NTF are presented and plans for facility testing with a specially designed test wing are discussed

ICONA: Inter Cluster ONOS Network Application

Several Network Operating Systems (NOS) have been proposed in the last few years for Software Defined Networks; however, a few of them are currently offering the resiliency, scalability and high availability required for production environments. Open Networking Operating System (ONOS) is an open source NOS, designed to be reliable and to scale up to thousands of managed devices. It supports multiple concurrent instances (a cluster of controllers) with distributed data stores. A tight requirement of ONOS is that all instances must be close enough to have negligible communication delays, which means they are typically installed within a single datacenter or a LAN network. However in certain wide area network scenarios, this constraint may limit the speed of responsiveness of the controller toward network events like failures or congested links, an important requirement from the point of view of a Service Provider. This paper presents ICONA, a tool developed on top of ONOS and designed in order to extend ONOS capability in network scenarios where there are stringent requirements in term of control plane responsiveness. In particular the paper describes the architecture behind ICONA and provides some initial evaluation obtained on a preliminary version of the tool.Comment: Paper submitted to a conferenc