Carlos F. Lange

H2O at the Phoenix Landing Site

Phoenix Ascending The Phoenix mission landed on Mars in March 2008 with the goal of studying the ice-rich soil of the planets northern arctic region. Phoenix included a robotic arm, with a camera attached to it, with the capacity to excavate through the soil to the ice layer beneath it, scoop up soil and water ice samples, and deliver them to a combination of other instruments—including a wet chemistry lab and a high-temperature oven combined with a mass spectrometer—for chemical and geological analysis. Using this setup, Smith et al. (p. 58) found a layer of ice at depths of 5 to 15 centimeters, Boynton et al. (p. 61) found evidence for the presence of calcium carbonate in the soil, and Hecht et al. (p. 64) found that most of the soluble chlorine at the surface is in the form of perchlorate. Together these results suggest that the soil at the Phoenix landing site must have suffered alteration through the action of liquid water in geologically the recent past. The analysis revealed an alkaline environment, in contrast to that found by the Mars Exploration Rovers, indicating that many different environments have existed on Mars. Phoenix also carried a lidar, an instrument that sends laser light upward into the atmosphere and detects the light scattered back by clouds and dust. An analysis of the data by Whiteway et al. (p. 68) showed that clouds of ice crystals that precipitated back to the surface formed on a daily basis, providing a mechanism to place ice at the surface. A water ice layer was found 5 to 15 centimeters beneath the soil of the north polar region of Mars. The Phoenix mission investigated patterned ground and weather in the northern arctic region of Mars for 5 months starting 25 May 2008 (solar longitude between 76.5° and 148°). A shallow ice table was uncovered by the robotic arm in the center and edge of a nearby polygon at depths of 5 to 18 centimeters. In late summer, snowfall and frost blanketed the surface at night; H2O ice and vapor constantly interacted with the soil. The soil was alkaline (pH = 7.7) and contained CaCO3, aqueous minerals, and salts up to several weight percent in the indurated surface soil. Their formation likely required the presence of water.

Improved numerical simulation of aerosol deposition in an idealized mouth–throat

Abstract The deposition of monodisperse particles (1.0– 26.0 μm diameter) in an idealized mouth–throat geometry has been studied numerically. The continuous phase flow is solved using a RANS (Reynolds averaged Navier–Stokes) turbulence model at inhalation flow rates of 90.0 and 30.0 l / min . The particulate phase is simulated using a random-walk/Lagrangian stochastic eddy-interaction model (EIM). Without near-wall corrections in the EIM, poor agreement is seen with experimental data on deposition. However, when a new near-wall correction in the EIM is implemented, the particle deposition results in the idealized mouth–throat geometry are in relatively good agreement when compared with measured data obtained in separate experiments.

Momentum and heat transfer from cylinders in laminar crossflow at 10-4 ≤ Re ≤ 200

Abstract A summary of results of numerical investigations of the two-dimensional flow around a heated circular cylinder located in a laminar crossflow is presented. Numerical investigations were carried out for the Reynolds number range 10 −4 ⩽ Re ⩽ 200 and for temperature loadings of 1.003–1.5. The computations yield information on Nu and C D variation with Reynolds number. The temperature dependence of the fluid properties (air) was taken into account and this resulted in a temperature dependence of the Nu – Re and C D – Re results. Information is also provided on the Strouhal number dependence on the Re number and on the critical Re number where vortex shedding starts.

Winds at the Phoenix landing site

[1] Wind speeds and directions were measured on the Phoenix Lander by a mechanical anemometer, the so-called Telltale wind indicator. Analysis of images of the instrument taken with the onboard imager allowed for evaluation of wind speeds and directions. Daily characteristics of the wind data are highly turbulent behavior during midday due to daytime turbulence with more stable conditions during nighttime. From L s ~77°-123° winds were generally ~4 m s -1 from the east, with 360° rotation during midday. From L s ~123°-148° daytime wind speeds increased to an average of 6-10 m s -1 and were generally from the west. The highest wind speed recorded was 16 m s -1 seen on L s ~147°. Estimates of the surface roughness height are calculated from the smearing of the Kapton part of the Telltale during image exposure due to a 3 Hz turbulence and nighttime wind variability. These estimates yield 6 ± 3 mm and 5 ± 3 mm, respectively. The Telltale wind data are used to suggest that Heimdal crater is a source of nighttime temperature fluctuations. Deviations between temperatures measured at various heights are explained as being due to winds passing over the Phoenix Lander. Events concerning sample delivery and frost formation are described and discussed. Two different mechanisms of dust lifting affecting the Phoenix site are proposed based on observations made with Mars Color Imager on Mars Reconnaissance Orbiter and the Telltale. The first is related to evaporation of the seasonal CO 2 ice and is observed up to L s ~95°. These events are not associated with increased wind speeds. The second mechanism is observed after L s ~111° and is related to the passing of weather systems characterized by condensate clouds in orbital images and higher wind speeds as measured with the Telltale.

Initial analysis of air temperature and related data from the Phoenix MET station and their use in estimating turbulent heat fluxes

[1] Thermocouples at three levels on a I m mast on the deck of the Phoenix Lander provided temperature data throughout the 151 sol Phoenix mission. Air temperatures showed a large diurnal cycle which showed little sol to sol variation, especially over the first 90 sols of the mission. Daytime temperatures at the top (2 m) level typically rose to about 243 K (-30°C) in early afternoon and had large (10°) turbulent fluctuations. These are analyzed and used to estimate heat fluxes. Late afternoon conditions were relatively calm with minimal temperature fluctuations but CFD computations show that heating from the lander deck and instruments have influenced temperatures measured at the lowest level (0.25 m above the deck) on the mast.

Simulation of particle deposition in an idealized mouth with different small diameter inlets

The deposition of monodisperse particles (1.0-12.5 w m diameter) in an idealized mouth geometry has been studied numerically for three different inlet diameters (3.0, 5.0, and 8.0 mm). The continuous phase flow is solved using a RANS (Reynolds Averaged Navier-Stokes) k m y turbulence model at an inhalation flow rate of 16.3, 21.7, and 32.2 L/min. The particulate phase is simulated using a random-walk/Lagrangian stochastic eddy-interaction model (EIM). When optimized near-wall corrections are included in the EIM, the particle deposition results in the idealized mouth geometry are in relatively good agreement with measured data obtained in separate experiments. Without the near-wall corrections in the EIM, poor agreement with experiment is seen.

Wall effects on heat losses from hot-wires

Abstract A thorough numerical investigation of the two-dimensional heat transfer and laminar flow around a single circular cylinder was performed. The main interest of this study was the flow configuration of a heated cylinder in the vicinity of a wall under conditions that resemble the flow past a hot-wire anemometry (HWA) probe. A finite volume Navier–Stokes solver enhanced by local block refinement and multigrid acceleration guaranteed highly accurate and efficient computational results. As a reference for the influence of the Reynolds and Prandtl numbers on the drag coefficient C D and Nusselt number Nu, the limiting case of a cylinder in free stream with a very small temperature loading ( T =1.003) was analyzed first. Calculations were performed in the Re range 10 −4 to 10 2 . All the results agreed well with available analytical/numerical and experimental results. By comparison with the reference results, the influence of the temperature dependence of the fluid properties on C D and Nu was determined. After these extensive verification predictions a study on the influence of the wall proximity in near-wall HWA measurements was tackled based on two limiting cases, a highly conducting and an insulating wall. The investigation allowed an estimate of the velocity correction needed by HWA data. The results for a highly conducting wall agreed well with available experimental results. A new form of bounded velocity correction was proposed for this case. The results for the case of an insulating wall were unexpected and contradictory to previous experimental observations. A detailed analysis of the numerical solution revealed new aspects of this complex flow situation. Existing experimental results with “nonconducting” wall materials were shown to reflect a combination of the extreme situations computed numerically.

The Effect of Breathing Pattern on Nebulizer Drug Delivery

The significance of using breathing patterns with simplified functional shapes in vented jet nebulizer research is examined. This study is comprised of three parts: (1) The measurement and analysis of human breathing patterns, (2) the subsequent in vitro testing of the effects of breathing pattern differences using a consistent bench test method, and (3) a computer modeling of these effects on the estimated regional drug deposition in the human lung. Breathing through a Pari LC-Star nebulizer caused statistically significant changes (p < or = 0.05) in measured human breathing patterns when compared to normal breathing. Observed changes included an increase in the tidal volume (34%) and period (39%). Additionally, the average duty cycle shifted 12% towards a more symmetrical breath due to the unequal increase in the inhalation and exhalation times (55% and 28%, respectively). The position of the point of maximum flow in each breath phase shifted towards the beginning and end of the breath for the inhale and exhale by 28% and 48%, respectively. The bench testing revealed that breathing pattern shape variation caused statistically significant differences in nebulizer output only in two cases. Decreasing duty cycles and shifting the point of maximum flow towards the beginning of the breath both result in a decrease in output efficiency. Square flow patterns produced slight but consistently higher output efficiencies (average 2.1% higher) and a constant output particle size over the course of each breath, different from the other non-square patterns. Numerical simulations revealed no significant dosage differences resulting from breathing pattern shape variations. However, square wave patterns consistently produced slight overpredictions in comparison with real nebulizer patterns. In contrast, sine wave patterns were found to produce essentially the same results as nebulizer patterns in both the bench tests and in the deposition simulations. This suggests that sine wave shapes are preferable for simulating breathing when bench testing drug delivery using vented jet nebulizers.

In vitro effect of a holding chamber on the mouth-throat deposition of QVAR (hydrofluoroalkane-beclomethasone dipropionate).

Experimental work has been conducted on the effect of an add-on holding chamber (Aerochamber) on the characteristics of deposition in a mouth-throat model using 100-microg hydrofluoroalkane-beclomethazone dipropionate (QVAR) metered dose inhalers at inhalation flow rates of 28.3, 60, and 90 L/min. A filter or cascade impactor downstream of the mouth-throat collected aerosol not depositing. The results emphasize the important well documented effect of a valved holding chamber (VHC), in reducing drug deposition in the mouth-throat. This reduction is largest (24% of nominal dose) at the lowest flow rate tested, becoming insignificant at 60 L/min. Total amount of drug delivered distal to the mouth-throat increases with flow rate both with and without a holding chamber, increasing from 42% to 69% of the nominal dose without a VHC as the inspiratory flow rate increases from 28.3 to 90 L/min. The effect of the holding chamber on post mouth-throat delivery was small, reaching significance only at the highest flow rate (90 L/min), where an increase by 8% of the nominal dose was observed. No significant effect on MMAD of beclomethasone-dipropionate occurred when the holding chamber was used. An argument based on the interaction between induced turbulence and particle inertia is used to shed light on the above observations.

Cough aerosol in healthy participants: fundamental knowledge to optimize droplet-spread infectious respiratory disease management

BackgroundThe Influenza A H1N1 virus can be transmitted via direct, indirect, and airborne route to non-infected subjects when an infected patient coughs, which expels a number of different sized droplets to the surrounding environment as an aerosol. The objective of the current study was to characterize the human cough aerosol pattern with the aim of developing a standard human cough bioaerosol model for Influenza Pandemic control.Method45 healthy non-smokers participated in the open bench study by giving their best effort cough. A laser diffraction system was used to obtain accurate, time-dependent, quantitative measurements of the size and number of droplets expelled by the cough aerosol.ResultsVoluntary coughs generated droplets ranging from 0.1 - 900 microns in size. Droplets of less than one-micron size represent 97% of the total number of measured droplets contained in the cough aerosol. Age, sex, weight, height and corporal mass have no statistically significant effect on the aerosol composition in terms of size and number of droplets.ConclusionsWe have developed a standard human cough aerosol model. We have quantitatively characterized the pattern, size, and number of droplets present in the most important mode of person-to-person transmission of IRD: the cough bioaerosol. Small size droplets (< 1 μm) predominated the total number of droplets expelled when coughing. The cough aerosol is the single source of direct, indirect and/or airborne transmission of respiratory infections like the Influenza A H1N1 virus.Study designOpen bench, Observational, Cough, Aerosol study