Numerical Simulation for Droplet Combustion Using Lagrangian Hydrodynamics

A predictive model of spray combustion must incorporate models for the wide variety of physical environments in a practical combustor. In regions where droplets are closely spaced, combustion resembles a diffusion flame; where they are well separated, an envelope or wake flame results. The relative velocity field between the fuel droplets and oxidizer in influences boundary layer development about the droplet, recirculating flow patterns, and droplet shape and stability. A model must encompass these interacting temporal and spatial effects as well as complicated combustor boundaries. The objective of the current work is to develop the triangular gridding method for describing the individual and collective properties of vaporizing and burning fuel droplets

Numerical simulations of fuel droplet flows using a Lagrangian triangular mesh

The incompressible, Lagrangian, triangular grid code, SPLISH, was converted for the study of flows in and around fuel droplets. This involved developing, testing and incorporating algorithms for surface tension and viscosity. The major features of the Lagrangian method and the algorithms are described. Benchmarks of the algorithms are given. Several calculations are presented for kerosene droplets in air. Finally, extensions which make the code compressible and three dimensional are discussed

High discharge rate characteristics of nickel-cadmium batteries for pulse load filtering

Several tests of specially fabricated nickel-cadmium batteries having circular disk type electrodes were considered. These batteries were evaluated as filter elements between a constant current power supply and a five hertz pulsed load demanding approximately twice the power supply current during the load on portion of the cycle. Short tests lasting 10,000 cycles were conducted at up to a 21 C rate and an equivalent energy density of over 40 Joules per pound. In addition, two batteries were subjected to 10 to the 7 charge/discharge cycles, one at a 6.5 C rate and the other at a 13 C rate. Assuming an electrode to battery weight ratio of 0.5, these tests represent an energy density of about 7 and 14 Joules per pound respectively. Energy density, efficiency, capacitance, average voltage, and available capacity were tracked during these tests. After 10 to the 7 cycles, capacity degradation was negligible for one battery and about 20% for the other. Cadmium electrode failure may be the factor limiting lifetime at extremely low depth of discharge cycling. The output was examined and a simple equivalent circuit was proposed

Memory B cells and CD8⁺ lymphocytes do not control seasonal influenza A virus replication after homologous re-challenge of rhesus macaques.

This study sought to define the role of memory lymphocytes in the protection from homologous influenza A virus re-challenge in rhesus macaques. Depleting monoclonal antibodies (mAb) were administered to the animals prior to their second experimental inoculation with a human seasonal influenza A virus strain. Treatment with either anti-CD8α or anti-CD20 mAbs prior to re-challenge had minimal effect on influenza A virus replication. Thus, in non-human primates with pre-existing anti-influenza A antibodies, memory B cells and CD8α⁺ T cells do not contribute to the control of virus replication after re-challenge with a homologous strain of influenza A virus

Infection with host-range mutant adenovirus 5 suppresses innate immunity and induces systemic CD4+ T cell activation in rhesus macaques.

Ad5 is a common cause of respiratory disease and an occasional cause of gastroenteritis and conjunctivitis, and seroconversion before adolescence is common in humans. To gain some insight into how Ad5 infection affects the immune system of rhesus macaques (RM) 18 RM were infected with a host-range mutant Ad5 (Ad5hr) by 3 mucosal inoculations. There was a delay of 2 to 6 weeks after the first inoculation before plasmacytoid dendritic cell (pDC) frequency and function increased in peripheral blood. Primary Ad5hr infection suppressed IFN-γ mRNA expression, but the second Ad5hr exposure induced a rapid increase in IFN-gamma mRNA in peripheral blood mononuclear cells (PBMC). Primary Ad5hr infection suppressed CCL20, TNF and IL-1 mRNA expression in PBMC, and subsequent virus exposures further dampened expression of these pro-inflammatory cytokines. Primary, but not secondary, Ad5hr inoculation increased the frequency of CXCR3+ CD4+ T cells in blood, while secondary, but not primary, Ad5hr infection transiently increased the frequencies of Ki67+, HLADR+ and CD95+/CCR5+ CD4+ T cells in blood. Ad5hr infection induced polyfunctional CD4 and CD8+ T cells specific for the Ad5 hexon protein in all of the animals. Thus, infection with Ad5hr induced a complex pattern of innate and adaptive immunity in RM that included transient systemic CD4+ T cell activation and suppressed innate immunity on re-exposure to the virus. The complex effects of adenovirus infection on the immune system may help to explain the unexpected results of testing Ad5 vector expressing HIV antigens in Ad5 seropositive people

Observational Evidence of Wave Ducting and Evanescence in the Mesosphere

A collaborative radar and imaging study of gravity waves over the Hawaiian Islands was performed during October 1993 as part of the Airborne Lidar and Observations of Hawaiian Airglow 1993/Coupling and Dynamics of Regions Equatorial (ALOHA-93/CADRE) campaign to investigate the propagation characteristics of short-period (\u3c1 hour) waves at nightglow altitudes. The horizontal wavelengths and apparent phase speeds of quasi-monochromatic wave events were measured in four separate nightglow emissions using data obtained by a high-resolution CCD imager. This information was correlated with simultaneous MF radar wind measurements over the same height interval (∼80–100 km) to infer intrinsic wave parameters in each case. Correlating the two data sets allowed the determination of the local vertical wavenumber for each event, in particular whether it be real (indicative of freely propagating waves) or imaginary (indicative of ducted or evanescent waves). The results of this study indicate a preponderance of ducted or evanescent waves at 80–100 km during the time of the observations, with up to ∼75% of the events recorded exhibiting ducted or evanescent behavior. Also noted was a tendency for ducted behavior to be more prevalent among waves with shorter horizontal wavelengths, in agreement with Doppler ducting theory. These results suggest that ducted waves are relatively common in the upper mesosphere and lower thermosphere region, at least over the mid-Pacific Ocean. As small-scale waves which are ducted have the potential to travel much longer horizontal distances than freely propagating waves, the frequency of their occurrence should be taken into account in efforts to quantify gravity wave effects at these altitudes

Determination of Horizontal and Vertical Structure of a Novel Pattern of Short Period Gravity Waves Imaged During ALOHA-93

An all‐sky CCD imager has been used to measure the properties of short period gravity waves present over the Hawaiian Islands during the ALOHA‐93 campaign. Observations of emissions from four different altitudes provided a capability to describe the vertical as well as the horizontal structure of the wave field. On several occasions during this campaign an unusual morphology wave pattern was detected that consisted of a group of small‐scale waves oriented in the same direction. These were most noticeable in the OI (557.7 nm) emission, altitude ∼96 km, and were usually observed in association with a larger scale gravity wave. This paper presents a preliminary analysis of data recorded on the night of 22 October during which both types of waves were prominent. The small‐scale waves exhibited highly coherent phase structures at each emission altitude, consistent with a ducted wave motion. The spatial intensity and phase modulation of this display is indicative of interference between two waves with similar characteristics and slightly different propagation directions. The larger scale wave motion was observed to propagate perpendicular to the small‐scale waves, and showed evidence of phase progression with altitude, implying upward energy propagation. These data have been interpreted in the context of simultaneous wind measurements from an MF radar

Gravity wave activity in the lower atmosphere: Seasonal and latitudinal variations

A climatology of gravity wave activity in the lower atmosphere based on high-resolution radiosonde measurements provided by the Australian Bureau of Meteorology is presented. These data are ideal for investigating gravity wave activity and its variation with position and time. Observations from 18 meteorological stations within Australia and Antarctica, covering a latitude range of 12°S – 68°S and a longitude range of 78°E – 159°E, are discussed. Vertical wavenumber power spectra of normalized temperature fluctuations are calculated within both the troposphere and the lower stratosphere and are compared with the predictions of current gravity wave saturation theories. Estimates of important model parameters such as the total gravity wave energy per unit mass are also presented. The vertical wavenumber power spectra are found to remain approximately invariant with time and geographic location with only one significant exception. Spectral amplitudes observed within the lower stratosphere are found to be consistent with theoretical expectations but the amplitudes observed within the troposphere are consistently larger than expected, often by as much as a factor of about 3. Seasonal variations of stratospheric wave energy per unit mass are identified with maxima occurring during the low-latitude wet season and during the midlatitude winter. These variations do not exceed a factor of about 2. Similar variations are not found in the troposphere where temperature fluctuations are likely to be contaminated by convection and inversions. The largest values of wave energy density are typically found near the tropopause.Simon J. Allen and Robert A. Vincen