Tracer simulations

Mahlman, J.D., and W.J. Moxim, Tracer simulation using a global general circulation model Results from a mid-latitude instantaneous source experiment. J Atmos Sci ... 

Tracer simulations entail injecting labelled particles in the bottom stage during a given time and detecting the number of these particles at different level in the colunm. The model enables to track the position of any labelled particle during its residence time in the riser. 

The simulation of the X-ray transform is implemented by the simple linear ray tracer model given by ... 

To prepare simulated free-of-noise 3D images of a complex body For this target the image of an internal pore in the real welding joint with extracted noise was used. The ray tracer model was applied for the simulation of five projections of the selected image. 

Measurements have been made in a static laboratory set-up. A simulation model for generating supplementary data has been developed and verified. A statistical data treatment method has been applied to estimate tracer concentration from detector measurements. Accuracy in parameter estimation in the range of 5-10% has been obtained. 

In the demonstration survey leaks were simulated by placing minor amounts of tracer outside the pipeline at difterent positions. 

The engineer is offered a large variety of flow-modeling methods, whose complexity ranges from simple order-of-magnitude analysis to direct numerical simulation. Up to now, the methods of choice have ordinarily been experimental and semi-theoretical, such as cold flow simulations and tracer studies. 

The average age of air for all air molecules in the complete room can be found by performing a step-up tracer gas experiment, and by measuring tracer gas concentration Q in the exhaust opening. The same procedure can be used for CFD simulations. The definition for average age of air in the room is... 

Research has been conducted to evaluate the effectiveness of several LVHV nozzle configurations for capturing tracer aerosols for simulated industrial operations.Studies have been conducted to evaluate dust capture for LVHV nozzles on hand-held tools, and have demonstrated over 90% collection efficiencies for operations such as grinding and sanding. 

In the case of gaseous contaminants, the tracer gas is selected to simu late as well as possible the properties (density, temperature) and momentum of the real contaminant. It is essential to ensure that the tracers arc nontoxic, chemically nonreactive, nonadsorptive on indoor surfaces, and inexpensive. The mixing of the tracer with the actual gaseous contaminant before its release or the release of the tracer with a density near that of the air will improve the validity of the simulation. With tracers, the most difficult task in practice is the relationship of the discharge between the tracer and the real contaminant. Case-by-case techniques to release the tracer are necessary in practice. With tracer gases, the procedure for capture efficiency is described in detail in the European Standard. - The tracer gas concentrations are measured in the exhaust duct for two release locations as illustrated in Fig. 10.108. 

Experiments on the scale of 1 to 1 are often used to study the local ventilation around an operator s workplace. Tracer gas is used to simulate the contaminant transport, and a high concentration level of the model tracer gas makes it possible to work with a convenient level of concentration for the measurements. Figure 12.31 shows an enclosure with an emission source S and a laboratory. setup with a model source 5,. The dimensionless concentration c/cg is... 

The advantage of the simulations compared to the experiments is that the correspondence between the tracer diffusion coefficient and the internal states of the chains can be investigated without additional assumptions. In order to perform a more complete analysis of the data one has to look at the quench-rate and chain-length dependence of the glass transition temperature for a given density [43]. A detailed discussion of these effects is far beyond the scope of this review. Here we just want to discuss a characteristic quantity which one can analyze in this context. 

Heimann, M. and Keeling, C. D. (1989). A three-dimensional model of atmospheric CO2 transport based on observed winds 2. Model description and simulated tracer experiments. In "Aspects of Climate Variability in the Pacific and Western Americas," Geophys. Monogr. Ser. vol. 55 (D. H. Peterson, ed.), pp. 237-275, AGU, Washington, DC. 

As mentioned in Section 11.3, fluidized-bed reactors are difficult to scale. One approach is to build a cold-flow model of the process. This is a unit in which the solids are fluidized to simulate the proposed plant, but at ambient temperature and with plain air as the fluidizing gas. The objective is to determine the gas and solid flow patterns. Experiments using both adsorbed and nonadsorbed tracers can be used in this determination. The nonadsorbed tracer determines the gas-phase residence time using the methods of Chapter 15. The adsorbed tracer also measures time spent on the solid surface, from which the contact time distribution can be estimated. See Section 15.4.2. 

These can be solved by classical methods (i.e., eliminate Sout to obtain a second-order ODE in Cout), by Laplace transformation techniques, or by numerical integration. The initial conditions for the washout experiment are that the entire system is full of tracer at unit concentration, Cout = Sout = L Figure 15.7 shows the result of a numerical simulation. The difference between the model curve and that for a normal CSTR is subtle, and would not normally be detected by a washout experiment. The semilog plot in Figure 15.8 clearly shows the two time constants for the system, but the second one emerges at such low values of W t) that it would be missed using experiments of ordinary accuracy. 

Setting k = 0, simulate the tracer response (F-curves) for 3 perfectly-stirred tanks in series. 

This program is designed to simulate tracer experiments for residence time distributions based on a cascade of 1 to 8 tanks-in-series. An nth-order reaction can be run, and the steady-state conversion can be obtained. The important parameters to change are as follows for the tracer experiments k, CAINIT, and CAO ( = 0 for E curve, = 1 for F curve). For reaction studies, the parameters to change are n, k, CAO, and CAINIT. 

Figure 5.88. A pulse of tracer was simulated by setting k = 0 and setting = 0 for a duration of AT = 1. The residence time TAU in each tank was 20, or 160 for the entire 8-tank system.

Simulated tracer experiments can be performed on either program by setting Ki a = 0 and starting with suitable initial conditions and inlet... 

TRACER so that he can compare the simulated and observed movement of a conservative substance such as chloride. Finally, he may turn TRACER off and PEST on, to simulate up to 3 pesticides. 

In Section 11.1.3.2 we considered a model of reactor performance in which the actual reactor is simulated by a cascade of equal-sized continuous stirred tank reactors operating in series. We indicated how the residence time distribution function can be used to determine the number of tanks that best model the tracer measurement data. Once this parameter has been determined, the techniques discussed in Section 8.3.2 can be used to determine the effluent conversion level. 

Studies of the transfer of radiocerium into various plant parts via the soil-root pathway are summarized in Table 6. Other laboratory and field studies employing tracer radiocerium or nuclear weapons fallout simulants are summarized in Tables 7 and 8. In general, the cereal grains and vegetable pulp showed plant-to-soil concentration factors (radioactivity per gram of dry plant material/radioactivity per gram of... 

Horowitz L, Walters S, Mauzerall D, Emmons L, Rasch P, Granier C, Tie X, Lamarque J, Schultz M, Tyndall G, Orlando J, Brasseur G (2003) A global simulation of tropospheric ozone and related tracers Description and evaluation of MOZART, version 2. Journal of Geophysical Research 108(D24), DOI 10.1029/2002JD002853... 

Fig. 6 Numerical simulation experiment with tracer. The Ebro River water is indicated by water with salinity equal to 0.1 psu and that of the Segre River equal to 0 psu...

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