Sizing and Scaling Requirements of a Large-Scale Physical Model for Code Validation
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SIZING AND SCALING REQUIREMENTS OF A LARGE-SCALE PHYSICAL MODEL FOR CODE VALIDATION R. KHALEEL AND T. LEGORE
Westinghouse Hanford Company, Richland, WA 99352 ABSTRACT Scaling considerations relevant to porous media flow are reviewed. An analysis approach is presented for determining the sizing requirements of a large-scale, hydrology physical model. The physical model will be used to validate performance assessment codes that evaluate the long-term behavior of the repository isolation system. Numerical simulation results for sizing requirements are presented for a porous medium model in which the media properties are spatially uncorrelated. INTRODUCTION Model validation is an important consideration in application of a code for performance assessment and therefore in assessing the long-term behavior of the engineered and natural barriers of a geologic repository. Although verification (i.e., comparison to analytical solutions, code-to-code intercomparison) is an important part of determining model acceptability, it does not establish that the model is a reasonable approximation to physical reality. This is accomplished in the validation step in which model calculations are compared with data from controlled experiments. A successful comparison of model simulations with experimental data indicate that the model is a reasonable description of the actual physical situation and accurately incorporates the interrelationships among the various processes. Thus, validation of mathematical models and associated computer codes using data from a controlled experiment provides the basis for the need of a physical model. Sizing and scaling requirements of a large-scale physical model for hydrological testing are presented. First, the scaling relationships describing the behavior of a heterogeneous, laboratory-scale experiment to that of a natural, heterogeneous medium of similar structure are reviewed. Second, a set of numerical experiments are conducted to determine a representative size for a heterogeneous, laboratory-scale experiment. Once the laboratory model is appropriately sized, the results obtained can be scaled up to the prototype system. PROPOSED HYDROLOGY PHYSICAL MODEL A schematic of the proposed hydrology physical model is shown in Figure 1. The purpose of the proposed hydrology physical modeling is to provide for the investigation and characterization of the physical processes involved in groundwater flow and transport at scales larger than what has been attempted before. Specifically, the objectives of the proposed physical modeling are two-fold: (a) develop, design, and construct a physical model (analog) to examine processes of groundwater flow and mass transport existing in an aquifer system (prototype); and (b) utilize the data obtained from the physical model to validate the three-dimensional numerical models of groundwater flow and mass transport as used in the performance assessment evaluation of a nuclear waste repository. The physical model is proposed to be a large tank containing media with varying h
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