Inlet Characteristics Research Articles

Improvement of forebody/inlet integration for hypersonic vehicle

Results of a numerical (CFD) study of the influence of the forebody shape on local flow parameters at a bottom-mounted inlet entrance are presented. The free-stream Mach number is assumed to be 3.5–7.0. Some recommendations on forebody shape optimization are provided. Main characteristics of the air inlet are evaluated.

Numerical diffusion and the tracking of solute fields in system codes: Part II. Multi-dimensional flows

In Part I of this series, it was shown that high order numerical methods can significantly reduce numerical diffusion during the simulation of 1-dimensional solute transport by system codes. The current paper extends these conclusions to multi-dimensional flows by showing that the use of such methods can greatly improve predictions of the solute transport in a vessel. A high order method, Smolarckievicz's flux corrected method, together with an improved numerical flux limiter, has been implemented in a system code (TRAC-PF1/MOD2) in order to perform the simulation of an experimental dilution transient. The analysis of the results shows that the method is able to predict the main local characteristics of the core inlet and solute concentration field whilst introducing very low numerical diffusion, which is smaller than the experimentally observed turbulent diffusion of the flow. This substantial reduction in numerical diffusion even permits us to see the effect on the core solute distribution by accurate prediction of the multi-dimensional flow field transporting the solute.

Characterization of the Gent Stacked Filter Unit PM10Sampler

ABSTRACT An integral part of several International Atomic Energy Agency sponsored coordinated research programmes involving the sampling and analysis of ambient airborne particules was the development of a PM10 sampler. Each participant was provided with such a sampler so that comparable samples would be obtained by each of the participating groups. Thus, in order to understand the characteristics of this sampler, we undertoke several characterization studies in which we examined the aerodynamic collection characteristics of the impactor inlet and the reproducibility of the sample mass collection. One of the samplers machined in Belgium was compared with one built from the same design in the U.S. and comparable results were obtained. The sampler was operated side-by-side with a commercial PM10 beta gauge and an IMPROVE-design 2.5 μm cut-point cyclone. Although the sampler was not wind tunnel tested as required for certification as a reference sampler, it does provide a collection efficiency that generally follows the guidelines for a PM10 sampler.

Characteristics of particle emissions at paint manufacturing

The handling of pigments and powders in paint manufacturing cause emissions of airborne particles. A great variety of substances occur. Previous studies (Bohgard et al., 1994) of simulations of pouring of pigments, which occur in small scale weighing procedures, showed typically bimodal size distribution including a sub-micron and a super-micron mode.The objective of the study was to get detailed knowledge on the relation between different source processes (depending on production technology, equipment and the manual handling routines) and aerosol characteristics.Super-micron particles were continuously measured with a time-of-flight instrument (Aerodynamic Particle Sizer, APS TSI Inc.) and sub-micron particles with an electric mobility spectrometer (Scanning Mobility Particle Sizer, SMPS TSI Inc.). In addition filter sampling techniques for standardised work-place sampling (so-called total dust filter cassettes, a cyclone sampler for respirable dust and IOM-samplers for inhalable dust) have been used for idealised exposure/area measurements using a rotating mannequin as a carrier of these samplers. The filters were analysed gravimetrically and with Particle Induced X-ray Emission Analysis. The aerosols were measured during manufacturing of batches of paint. Sources and source mechanisms, as pouring pigments from bags, disposal of packages, mixing of powders and pigments and suspected re-suspension sources, were documented simultaneously with the performance of the measurements.Figure 1 shows examples of size distributions obtained with the APS and SMPS. The size distributions have essentially bimodal shapes with median diameters of 0.05 -0.4 [mu ]m and of 2-5 [mu ]m respectively. Rapid variation in concentration occurs.Preliminary results show that several sources occur. Irregular activities and events as disposal of package material, cleaning, leakage from conveyor tubes and re-suspension due to wind velocities from open gates and moving vehicles significantly contribute to the particle concentrations.Filter sampling with the samplers mounted on a mannequin torso, rotating 360 degrees forth and back, is advantageous by giving idealised measures on exposure. Samplers mounted on equal horizontal level will have equal sampling location integrated over time. Furthermore, the sampling procedure emulate sampling in accordance with sampling conventions. Inlet characteristics of samplers mounted on a body differ from characteristics of free-hanging samplers (Vincent, 1989). Higher estimated mass concentrations were obtained with the IOM-samplers for inhalable dust than with the 37 mm open-face [ldquo ]total dust[rdquo ] cassettes.Figure omitted (Less)

Internal flowfield characteristics of a scramjet inlet at Mach 10

Internal flowfield characteristics of a scramjet inlet at Mach 10

Langmuir probe measurements during plasma-activated chemical vapor deposition in the system argon/oxygen/Aluminum isopropoxide

A Langmuir probe investigation of Ar/O2/Al(OPr1)3 plasmas is described. The probe contamination depends on the probe position and the flow of tine carrier gases. Whereus far from the working gas inlet characteristics without any hysteresis were obtained, near to the inlet undisturbed characteristics were recorded only for small gas flows or a low vapor pressure of the precursor. Condensation of the precursor ai the probe surface prior to the plasma excitation was the main source of probe contamination. A decrease ire the plasma potential with respect to the ground observed during experiments was attributed to the formation of a dielectric film on the rf electrode. This resulted in a self-bias responsible for the decrease in plasma potential.

Morphodynamics of the stagnating Zwin inlet, The Netherlands

This study investigates the morphodynamical characteristics of the Zwin inlet, Zeeland, southwest Netherlands. Data is based on field measurements of currents and their flow pattern recognition and on study of the intertidal bedform fields. Long-term bathymetric data and coastal monitoring by air photo interpretation were further applied for revealing the main morphological response in the inlet and along its adjacent beaches.Within the spatial segregation of flood- and ebb-dominated flows, seven bedform fields were defined with characteristic spatial organization and clear textural trends. The overall picture demonstrates a stagnating inlet with sand starvation along the Dutch coast and widening of the Belgian beach updrift. The Zwin inlet functions as a sedimentary trap, with its typical ebb-delta features displaced shorewards.

Validation of a one-dimensional wave model for the stratified-to-slug flow regime transition, with consequences for wave growth and slug frequency

A one-dimensional wave model for incompressible flows predicts the transition between the stratified and slug flow regimes in pipes. The one-dimensional wave theory contains less empiricism than the commonly used Taitel-Dukler model for this transition. The empiricism embodied in the Taitel-Dukler analysis leads to the underprediction of the transition velocity at high gas density in large pipes in particular. This paper presents a complete solution methodology for the one-dimensional wave approach for this transition and validates the method by comparison with a wide range of flow regime data at large pipe diameters, at high gas density and in horizontal or inclined pipes. The analysis is extended, by using the method of characteristics, to model wave growth, decay and interaction. Since all waves usually propagate downstream we are led to question the Taitel-Dukler model for slug frequency and to suggest that the inlet characteristics, including compliance, play a role.

Intercomparison of annular denuder and filter pack sampling methods for collection of acidifying species in south east England

Both annular denuder system (ADS) and filter pack (F.P) samplers exhibited a broad agreement. However, the F.P sampler collected higher concentrations of large particles reflecting better inlet characteristics. The F.P sampler also overestimated measurements of NH 3, HCl and HNO 3 primarily due to evaporation of ammonium chloride and ammonium nitrate to their precursor gases. Sulphate particles showed good accord in both samplers. It is very important to stress that these techniques may vary from one place to another.

Study of Tidal‐Inlet Stability

Development of information regarding the hydraulic characteristics of tidal inlets plays an important part in evaluating the safety of navigation and inlet stability. The assembled information is also useful since the design of navigation improvements must be directed towards the goal of reducing the volume of maintenance dredging and improving the navigation safety. Extensive data sets obtained from aerial photography over the past 30 years by the U.S. Corps of Engineers were used to study the relationship between hydraulic variables and its stability. This research concentrated on developing relationships between selected inlet characteristics, inlet width and inlet length, and inlet stability for 51 U.S. tidal inlets.

Sampling and Interpretation Errors in Aerosol Monitoring

The aerosol recorded by simple filter collection or by sophisticated instrument aerosol monitoring may differ considerably from the original, unsampled aerosol. Through use of particle-sizing instruments and computer modeling, the potential biases in sampling, display, and interpretation are demonstrated. The aerosol-size distribution and, therefore, the reported number or mass concentration may be affected by the characteristics of the sampling inlet, the transport to the sensor and the sensor itself. The particle count in specific size ranges determines the precision of the registered particle-size distribution, depending on the weighting chosen. The type of display, by histograms or cumulative plot, focuses on different aspects of the size distribution, and the calibration of the aerosol monitor ma modify it further. Particle-size classification to simulate a specific region of the human respiratory system may be achieved through inertial classification or the sensitivity characteristics of the aerosol sensor. Aerosol monitors using passive sampling register the same aerosol-size distribution as active ones, if the aerosol is transported to the sensor with the same efficiency as in the active mode. The sources of various types of errors are presented using computer simulations of typical aerosol-size distributions, often combined with measurements found in the literature. Presentation of these errors in graphical format allows the health professional to estimate more accurately the health implications of aerosol measurements.

Sampling and Interpretation Errors in Aerosol Monitoring

The aerosol recorded by simple filter collection or by sophisticated instrument aerosol monitoring may differ considerably from the original, unsampled aerosol. Through use of particle-sizing instruments and computer modeling, the potential biases in sampling, display, and interpretation are demonstrated. The aerosol-size distribution and, therefore, the reported number or mass concentration may be affected by the characteristics of the sampling inlet, the transport to the sensor and the sensor itself. The particle count in specific size ranges determines the precision of the registered particle-size distribution, depending on the weighting chosen. The type of display, by histograms or cumulative plot, focuses on different aspects of the size distribution, and the calibration of the aerosol monitor may modify it further. Particle-size classification to simulate a specific region of the human respiratory system may be achieved through inertial classification or the sensitivity characteristics of the aerosol sensor. Aerosol monitors using passive sampling register the same aerosol-size distribution as active ones, if the aerosol is transported to the sensor with the same efficiency as in the active mode. The sources of various types of errors are presented using computer simulations of typical aerosol-size distributions, often combined with measurements found in the literature. Presentation of these errors in graphical format allows the health professional to estimate more accurately the health implications of aerosol measurements.

Analysis of atmospheric ammonia and particulate ammonium by a sensitive fluorenscence method

A sensitive fluorescence method for the analysis of atmospheric ammoniaand particulate ammonium is described. The fluorescence of the ammonium-o-phthalaldehyde moiety is utilized in a flow injection system to effect a limit of detection of 204 ng m/sup -3/ (3sigma) for atmospheric ammonia and 27 ng m/sup -3/ (3sigma) for particulate ammonium in 3-h air samples collected respectively on H/sub 3/PO/sub 4/-impregnated Whatman 41 and Teflon filters in a filter pack at 10 L min/sup -1/. The limit of detection for NH/sub 3/ may be reduced to 78 ng m/sup -3/ (3sigma) by use of H/sub 3/PO/sub 4/-impregnated nylon filters. An intercomparison with the indophenol blue method is also described together with collection efficiencies on different impregnated filters. The analytical procedure is applicable also to ammonia collected by a denuder coated with phosphorus acid, with the detection limit of 450 ng m/sup -3/ (3sigma) for a 3-h sample. A comparison of the filter-pack and denuder sampling methods indicated a small degree of evaporation of ammonium salt aerosol in the filter pack, leading to slight overestimation of ammonia concentrations. Ammonium aerosol concentrations measured by the two techniques were virtually identical since the superior inlet characteristics of the filter-pack sampler compensated for evaporativemore » losses of ammonium salts.« less

ソニックインレットの研究

In recent aircraft with high by-pass ratio engines, the major noise source is the forward propagating fan noise from the engine inlet. Reported here is the investigation of the sonic inlet, which drastically reduces the abovementioned forward propagating fan noise. Model sonic inlets of both contracting wall type and translating centerbody type were designed by the newly developed analytical method based on flux analysis, and tested aero-dynamically and acoustically. Criteria for boundary layer separation, total pressure recovery characteristics, and crosswind characteristics of sonic inlet were obtained, and the model sonic inlet of the contracting wall type showed 21 PNdB noise reduction in model engine noise tests. Comparison between the analytical and experimental results proved the usefulness of the newly developed design method.

A thoracic particle inlet ( d50 = 6 μm, do = 10 μm) for the high-volume sampler

We have designed, fabricated and tested a size specific inlet to retrofit the High-Volume Sampler to give a nominal 50-percent effectiveness diameter (d 50) of 6 μm and no transmission of particles 10 μm or larger ( d o = 10 μm). Actual test values were: d 50 = 5.85 μm, σ 16 = 1.32, σ 84 = 1.35, independent of wind speed from 2 to 24 km h −1. The principal collecting surface for oversized particles is a porous material impregnated with oil, thus indefinitely preventing particle bounce or reentrainment. The inlet characteristics were found to be independent of orientation relative to the wind, as well as inadvertent 10 percent variations in flow rate. The mass distribution on the collection substrate is uniform within 3 percent. The inlet totally prevents deposition of particles on the collection substrate when the sampler is not operating.

Inlet Characteristics of River Sagami

Inlet Characteristics of River Sagami