LDA-Measurements of Transitional Flows Induced by a Square Rib

Becker, Stefan; Stoots, C. M.; Condie, K. G.; Durst, F.; McEligot, Donald M.

doi:10.1115/1.1446067

Cited by 13 publications

(16 citation statements)

References 18 publications

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“…The refractive index of the fluid is maintained at the desired value by a parallel temperature control system, which maintains a constant temperature in the test section within ± 0.05ºC. In measurements in an experiment on transition induced by a square rib, meaningful velocity and turbulence data were obtained as close to the surface as y + = (y u / ) 0.1 and less (Becker et al, 2002).…”

Section: Inl Mir Flow Systemmentioning

confidence: 99%

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Estimated Uncertainties in the Idaho National Laboratory Matched-Index-of-Refraction Lower Plenum Experiment

McEligot¹,

McIlroy²,

Johnson³

2007

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The purpose of the fluid dynamics experiments in the MIR (Matched-Index-of-Refraction) flow system at Idaho National Laboratory (INL) is to develop benchmark databases for the assessment of Computational Fluid Dynamics (CFD) solutions of the momentum equations, scalar mixing, and turbulence models for typical Very High Temperature Reactor (VHTR) plenum geometries in the limiting case of negligible buoyancy and constant fluid properties. The experiments use optical techniques, primarily particle image velocimetry (PIV) in the INL MIR flow system. The benefit of the MIR technique is that it permits optical measurements to determine flow characteristics in passages and around objects to be obtained without locating a disturbing transducer in the flow field and without distortion of the optical paths. The objective of the present report is to develop understanding of the magnitudes of experimental uncertainties in the results to be obtained in such experiments. Unheated MIR experiments are first steps when the geometry is complicated. One does not want to use a computational technique, which will not even handle constant properties properly. This report addresses the general background, requirements for benchmark databases, estimation of experimental uncertainties in mean velocities and turbulence quantities, the MIR experiment, PIV uncertainties, positioning uncertainties, and other contributing measurement uncertainties.The accuracy of the velocity field determination is ultimately limited by the ability of the scattering particles to follow the unsteady motion of the continuous phase. For the particles in the MIR VHTR experiment, the estimated cutoff frequency is about 40 kHz. The frequency of shedding from the posts in the MIR model is estimated to be of the order of 1 Hz and, therefore, the particles should follow the flow.Based on review of the literature, we estimate that the random uncertainty in measured particle displacement for our system and experiment is about 0.3 pixel for a single realization away from the walls. As an example, we estimated the uncertainties in measurements for the maximum velocity in an inlet jet flow operating at about its minimum flow rate. Consequently, this example would provide worst-case estimates in some senses. For the uncertainty in the mean velocity at this location, one could report With the current MIR model and the 3D PIV system, McIlroy and colleagues examined the effects of sample size for a typical set of measurements. Trends were generally as observed by Uzol and Camci. Preliminary conclusions were that (for this view and processing parameters) about 750 images should be collected to reduce the scatter in mean velocity statistics to between 0.4 and 10% v for velocities greater than about 2 m/s. The trends predicted by an uncertainty analysis are consistent with the observations, but, for the most part, the expected values are less than the scatter observed. Preliminary conclusions from the comparisons are that (1) more samples should be collected than predict...

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Section: Inl Mir Flow Systemmentioning

confidence: 99%

“…The MIR technique is not new; Corino and Brodkey (1969) employed it to measure turbulence structure in a circular tube. Recent applications of the technique include, but are not limited to, those of Durst, Jovanovic, and Sender (1993), Parker and Merati (1996), Cui and Adrian (1997), and Becker et al (2002).…”

Section: Inl Mir Flow Systemmentioning

confidence: 99%

Estimated Uncertainties in the Idaho National Laboratory Matched-Index-of-Refraction Lower Plenum Experiment

McEligot¹,

McIlroy²,

Johnson³

2007

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“…The design flow rate can give Reynolds numbers up to about 10 5 based on the cross section of the MIR test section. The refractive index of the fluid is maintained at the desired value by a parallel temperature control system which maintains a constant temperature in the test section to within 0.1 C. In measurements in an experiment on transition induced by a square rib, meaningful velocity and turbulence data were obtained as close to the surface as y + = (y u / ) 0.1 and less [Becker et al, 2002].…”

Section: Not Matched Matchedmentioning

confidence: 99%

“…The MIR technique is not new itself; Corino and Brodkey [1969] employed it to measure turbulence structure in a circular tube earlier. Recent applications of the technique include, but are not limited to, those of Durst, Jovanovic and Sender [1993], Parker and Merati [1996], Cui and Adrian [1997] and Becker et al [2002]. [Thompson, Bouchery and Lowney, 1995] and a simple demonstration of the benefits with transparent models having curved interfaces…”

Section: Ineel Matched-index-of-refraction Flow Systemmentioning

confidence: 99%

Development Of An Experiment For Measuring Flow Phenomena Occurring In A Lower Plenum For VHTR CFD Assessment

McEligot¹,

Condie²,

Creery³

et al. 2005

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The objective of the present report is to document the design of our first experiment to measure generic flow phenomena expected to occur in the lower plenum of a typical prismatic VHTR (Very High Temperature Reactor) concept. In the process, fabrication sketches are provided for the use of CFD (computational fluid dynamics) analysts wishing to employ the data for assessment of their proposed codes. The general approach of the project is to develop new benchmark experiments for assessment in parallel with CFD and coupled CFD/systems code calculations for the same geometry. One aspect of the complex flow in a prismatic VHTR is being addressed: flow and thermal mixing in the lower plenum ("hot streaking" issue). Current prismatic VHTR concepts were examined to identify their proposed flow conditions and geometries over the range from normal operation to decay heat removal in a pressurized cooldown. Approximate analyses were applied to determine key non-dimensional parameters and their magnitudes over this operating range. The flow in the lower plenum can locally be considered to be a situation of multiple jets into a confined crossflow --with obstructions. Flow is expected to be turbulent with momentum-dominated turbulent jets entering; buoyancy influences are estimated to be negligible in normal full power operation. Experiments are needed for the combined features of the lower plenum flows. Missing from the typical jet experiments available are interactions with nearby circular posts and with vertical posts in the vicinity of vertical walls -with near stagnant surroundings at one extreme and significant crossflow at the other.Unheated MIR (Matched-Index-of-Refraction) experiments are first steps when the geometry is complicated. One does not want to use a computational technique which will not even handle constant properties properly. The purpose of the fluid dynamics experiments is to develop benchmark databases for the assessment of CFD solutions of the momentum equations, scalar mixing and turbulence models for typical VHTR plenum geometries in the limiting case of negligible buoyancy and constant fluid properties. As indicated by the scaling studies, in normal full power operation of a typical VHTR conceptual design, buoyancy influences should be negligible in the lower plenum. The MIR experiment will simulate flow features of the paths of jets as they mix in flowing through the array of posts in a lower plenum en route to the single exit duct. The conceptual design for such an experiment is described and the development of the final apparatus is presented. Fabrication sketches are provided in Appendix A for the use of CFD analysts wishing to employ the data for assessment of their proposed codes. iv v

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Section: Ineel Matched-index-of-refraction Flow Systemmentioning

confidence: 99%

Measurements of Fundamental Fluid Physics of SNF Storage Canisters

Condie¹,

Creery²,

McEligot³

2001

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SummaryWith the University of Idaho, Ohio State University and Clarksean Associates, this research program has the long-term goal to develop reliable predictive techniques for the energy, mass and momentum transfer plus chemical reactions in drying / passivation (surface oxidation) operations in the transfer and storage of spent nuclear fuel (SNF) from wet to dry storage. Such techniques are needed to assist in design of future transfer and storage systems, prediction of the performance of existing and proposed systems and safety (re)evaluation of systems as necessary at later dates.Many fuel element geometries and configurations are accommodated in the storage of spent nuclear fuel. Consequently, there is no one generic fuel element / assembly, storage basket or canister and, therefore, no single generic fuel storage configuration. One can, however, identify generic flow phenomena or processes which may be present during drying or passivation in SNF canisters. The objective of the INEEL tasks was to obtain fundamental measurements of these flow processes in appropriate parameter ranges.With the University of Idaho, an idealization of a combined drying and passivation approach has been defined in order to investigate the generic flow processes. This simulation includes flow phenomena that occur in canisters for high-enrichment and medium-enrichment fuels, where fuel element spacing in the canister is increased as compared with low enrichment fuel. Canister diameter was taken as 46 cm (18 in.) and a single basket of about 1.3 meters (4 ft.) length was considered. A long central tube ("dip tube") served as the inlet as in one earlier concept for a passivation process; while this concept apparently has not yet been selected for application, it provides an excellent example of the coupled, complex phenomena which may be present in canister flows. Suggested design flow rates for this hypothesized application indicate that the Reynolds number in the inlet tube would be expected to be between 2500 and 5000, i.e., relatively low.The local distributions of convective mass transfer characteristics (drying/passivation) are expected to depend on the freestream turbulence in the flow around stored fuel elements. The magnitudes of this turbulence depend on the turbulence distributions on the upstream side of the perforated basket support plate ("inlet plenum") and, in turn, in the impinging jet and in the inlet tube. This information can assist engineers in understanding variations of surface drying and passivation through an array and approaches to modify designs to counter non-uniformities and to improve iii distribution, as well as providing bases for assessment of computational fluid dynamics codes proposed for the purpose.A water-flow experiment with a 3/4-scale model (relative to the idealized canister) has been used for overall flow visualization and velocity measurements, with and without an array of simulated fuel elements. Observations have been made with perforated plates (representing basket support plates) having...

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LDA-Measurements of Transitional Flows Induced by a Square Rib

Cited by 13 publications

References 18 publications

Estimated Uncertainties in the Idaho National Laboratory Matched-Index-of-Refraction Lower Plenum Experiment

Estimated Uncertainties in the Idaho National Laboratory Matched-Index-of-Refraction Lower Plenum Experiment

Development Of An Experiment For Measuring Flow Phenomena Occurring In A Lower Plenum For VHTR CFD Assessment

Measurements of Fundamental Fluid Physics of SNF Storage Canisters

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