A National Veterans Strategy: The Economic, Social and Security Imperative

This publication details the foundational logic supporting a call to action, related to a broad-based effort to articulate and institutionalize a National Veterans Strategy. We argue that coordinated, "whole-of-government" action toward this end is essential to meet the nation's most important economic, social, and security obligations. Furthermore, we contend that the second Obama administration, working in close collaboration with executive agencies, Congress, and the private sector, is well-positioned to act on what we perceive to be a historic opportunity -- capitalizing on both the foundations of veteran-focused policy and progress enacted over the past decade and the overwhelming public support for returning veterans and military families -- to craft and institutionalize a National Veterans Strategy.Our purpose is to provide a researched and logically-developed case for action that is grounded in this nation's social and cultural traditions and attuned to the practical realities of our contemporary economic and political climate

Experimental study of low-frequency oscillations and large-scale circulations in turbulent mixed convection

The formation and dynamics of large-scale circulations in forced and mixed convection has been studied at ambient and elevated fluid pressure by means of particle image velocimetry and temperature measurements. The study has been conducted in two rectangular containers of the same shape and aspect ratios of Cxz = 1 and Cyz = 5. For the measurements at high fluid pressure the dimensions of the cell have been scaled down by a factor of 5. Air with Pr = 0.7 has been used as fluid in both configurations. Forced convection has been investigated at Re = 1.01 x 104 and mixed convection has been studied at Ar = 3.3, Re = 1.01 x 10 up4 and Ra = 2.4 x 10 up8. In this configuration low-frequency oscillations in the heat transfer between the inlet and outlet have been found for mixed convection. Instantaneous velocity vector fields obtained from particle image velocimetry have been analysed using proper orthogonal decomposition and an algorithm to detect the core and the core centre position of large-scale circulations

The differential impact of several teaching strategies upon the integration of economic concepts into the mathematics curriculum

This investigation focuses upon two major problems. The first problem is to determine what effect the inclusion of economics in the mathematics curriculum will have upon student attitudes toward and understanding and retention of economics and mathematics. The second problem is to determine whether different methods of instruction will result in significantly different levels of student attitudes toward and understanding and retention of economics and mathematics

Artificial saliva aerosol source and detection system for spreading analysis in indoor environments

In the context of the Corona pandemic the investigation of aerosol spreading is utmost important as the virus is transported by the aerosol particles exhaled by an infected person. Thus, a new aerosol generation and detection system is set up and validated. The system consists of an aerosol source generating a particle size distribution mimicking typical human exhalation with particles sizes between 0.3-2.5 µm and an array of Sensirion SPS30 particulate matter sensors. An accuracy assessment of the SPS30 sensors is conducted using a TSI OPS3330, a high-precision optical particle sizer. Low deviations of ±5 % of the particle concentration measured with the SPS30 with respect to the OPS are reported for concentrations below 2’500/cm³ and +10% for particle densities up to 25’000/cm³. As an application example the system is employed in a short distance single-aisle research aircraft Dornier 728 (Do728) located at DLR Göttingen, to investigate the large-scale aerosol-spreading. With this measurement system a determined spreading distance from an index passenger extending one seat row to the front and two seat rows to the back is determined

Increased Passenger Density in a Long-Range Aircraft Cabin Mock-Up at Mixing Ventilation

Increasing the seating density is a powerful tool to enhance the economic and ecologic performance of a passenger aircraft. However, doing so arises new challenges for cabin ventilation to maintain comfort and air quality. As benchmark case, a generic mixing ventilation (MV), which is state-of-the-art in aircraft cabins, was investigated under static flight conditions in a full-scale twin aisle cabin mock-up with high seating density at various flow rates. Temperature controlled thermal manikins were used in this cabin mock-up to simulate the heat release of the passenger, see Figure 1 left and for details see Lange et. al [1]. The new research facility allows to investigate different, well-defined ventilation concepts under varying thermodynamic boundary conditions, thus reducing cost- and resource-expensive flight testing [2]. Figure 1 left: Interior of cabin mock-up with thermal manikins [1] and right, equivalent temperature for three different cases of seating density. The measurement techniques and the test matrix were selected and designed in order to quantify and evaluate the following parameters: boundary conditions, cabin air temperatures, efficiency of the ventilation concept, local velocities as well as thermal comfort, i.e., equivalent temperatures [3] (Figure 1 right). Two different cases of high seating density (4-5-4 and 4-6-4) are compared to the normal 3-4-3 case. First results obtained at a constant air flow rate show a weak, but existing, effect of the different seating configurations on the body-segment wise equivalent temperatures, i.e. the local thermal comfort, shown in Figure 1 right for an aisle seat. Additional measurements were performed with adjusted flow rates. [1] Lange, P. et al., 2022. Realistic flight conditions on ground new research facility for cabin ventilation. CEAS Aeronautic Journal, 13(3), pp. 719 - 738, doi: 10.1007/s13272-022-00594-2. [2] https://www.dlr.de/as/en/desktopdefault.aspx/tabid-17350/27473_read-69992/, (online), accessed March, 2nd, 2023. [3] ISO 14505-2. 2006. Ergonomics of the thermal environment: Evaluation of thermal environments in vehicles – Part 2: Determination of equivalent temperature, ISO 14505-2:200

Numerical and experimental study of aerosol dispersion in the Do728 aircraft cabin

The dispersion of aerosols originating from one source, the ‘index’ passenger, within the cabin of the aircraft Do728 is studied experimentally using an aerosol-exhaling thermal manikin and in Reynolds-averaged Navier–Stokes simulations (RANS). The overall aim of the present study is the experimental determination of the aerosol spreading for the state-of-the-art mixing ventilation (MV) and to evaluate the potential of alternative ventilation concepts for controlling the aerosol spreading in RANS. For MV, the experiments showed that the ratio of inhaled to exhaled aerosol particles drops below 0.06% (volume ratio) for distances larger than two seat rows from the source. However, within a single row, the observed ratio is higher. Further, the dispersion is much weaker for a standing than for a seated index passenger. High air exchange rates and a wellguided flow prevent a dispersion of the aerosols in high concentrations over larger distances. Additionally, the positive effect of a mask and an increased air flow rate, and especially their combination are shown. In the complementary conducted RANS, the advantages of floor-based cabin displacement ventilation (CDV) which is alternative ventilation concept to MV, regarding spreading lengths and the dwell time of the aerosols in the cabin were determined. The obtained results also underline the importance of the flow field for the aerosol dispersion. Further, additional unsteady RANS (URANS) simulations of the short-term process of the initial aerosol cloud formation highlighted that the momentum decay of the breathing and the evaporation processes take place within a few seconds only

Experimental Simulation of the Human Respiration

In this paper, we present a new mobile respiration simulation system (RSS), which can be connected to existing thermal manikins. With the objective to simulate the human respiration process as realistic as possible, the system was validated on the basis of literature data and results obtained from human subject tests. The RSS reproduces realistic respiration cycles characterized by a sine wave of a typical normal breathing flow rate. The provided flow rates as well as the breathing frequency – representing the time of inhalation and exhalation – were verified by literature values. Since the new system additionally allows to enrich the exhaled air with carbon dioxide (CO2), experimental studies addressing the indoor air quality are also feasible. Here, the amount of CO2 emitted by the RSS corresponds to the average amount of CO2 exhaled by test persons. In addition, the flow characteristics occurring in a human nose are simulated using a self-developed facial mask, in combination with the new system. The result is a breathing thermal manikin based on a mobile respiration simulation system, which can easily be connected to heated passenger models. Accordingly, the system can be installed at any seat within a passenger compartment. This offers the advantage of individually defining the location of the manikin, which can effortlessly be adapted during a measurement campaign. Therefore, the system especially suitable for studies addressing the performance of ventilation systems in passenger compartments and indoor environments

Numerical Simulation of the Aerosol Formation and Spreading in a Train Cabin

In this paper a numerical approach for the prediction of the unsteady aerosol formation and transmission process in a train cabin is presented. For that purposes models to simulate unsteady flows including the transient behaviour of two-phase atomization process and thermal air flow are employed. Results of aerosol distribution for coughing, speaking and breathing (with and without mask) in specified train cabin compartment are discussed. The dispersion of the exhaled droplets was analysed for a double cough, 10 s talking and continuous breathing of one source passenger. The results obtained show that the dispersion of aerosol particles in the cabin after coughing is two times deeper than when speaking, 2.5 times deeper than when free breathing and 17 times deeper than when breathing with a mask. Further, the results revealed that 2 minutes after the end of the coughing, only about 6% of active aerosol particles remain in the compartment and relatively clean air is again in the cabin

Micro-Jet Ventilation – a Novel Ventilation Concept for long-range Aircraft Cabins

Micro-Jet Ventilation (MJV), known from ventilation systems in trains, was experimentally investigated under static flight conditions in a full-scale twin-aisle cabin mock-up as part of the Clean-Sky 2 Joint Undertaking project ADVENT. A jacket cooling system was used to investigate ventilation systems for aircraft cabins with thermodynamically realistic boundary conditions. Temperature-controlled thermal manikins (TMs) make it possible to simulate the heat dissipation and obstruction of real passengers. In this study, six different modifications of MJV with different air inlet configurations are analyzed to determine the optimal parameters for thermal comfort and energy savings. Fluid temperatures as well as velocities in the vicinity of the TMs were investigated using high-resolution local probes. An evaluation of the various MJV configurations was performed based on heat removal efficiency, thermal comfort parameters, and tracer gas analysis. The study clearly shows the near-optimal comfort parameters of two MJV configurations for future aircraft cabins

Impact of Non-Occupied Seats on the Thermal Comfort in Long-Range Aircraft for Novel Ventilation Concepts

Novel ventilation systems for aircraft cabins have attracted the attention of scientists and aircraft manufacturers during the last years. Previous studies demonstrate the potential of energy saving as well as a achieving a higher level of thermal comfort in a single aisle aircraft. To allow for a greener and smarter testing of novel ventilation concepts for future long-range airliners, a full-scale twin aisle cabin mock-up with thermodynamically realistic boundary conditions by means of temperature-controlled fuselage elements was developed at the German Aerospace Center (DLR) in Göttingen. Temperature controlled thermal manikins allow to simulate the heat release and obstruction of real passengers. In this study, ceiling-based ventilation concepts were investigated experimentally with regard to incompletely occupied cabins, which are rather the rule than the exception (passenger load factor 75 to 90%, and even much less during the present pandemic time). Changes of the horizontal temperature distribution by switching off thermal manikins on selected seats for different flight phases were analysed using high-resolution local measurement probes as well as infrared cameras. A comparison with results of non-occupied seats in a single aircraft cabin will be conducted using previous studies and conclusions on the robustness of the ceiling-based concepts will be drawn