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Current Experiments
The M​atched-Index-of-Refraction flow system will explore coolant channel flow and bypass gap flow for the Very High Temperature Reactor program.

​​​​​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 the flow ratios between coolant channels and bypass gaps in the interstitial regions of typical prismatic standard fuel element or upper reflector block geometries of typical Very High Temperature Reactors (VHTR)  in the limiting case of negligible buoyancy and constant fluid properties. The MIR VHTR Bypass Flow Experiment will measure flow characteristics in the coolant channels and interstitial gaps between typical prismatic block standard fuel elements or upper reflector blocks. 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. Unheated MIR experiments are first steps when the geometry is complicated.

Images of experimental model:

Image showing the region of interest of a VHTR gas-cooled reactor, the way the fuel elements fit into the core and how the coolant flows through the coolant channels and also through the interstitial gaps between fuel blocks.


Experimental model graphic
An image of the experimental model that will be fabricated and installed in the MIR flow system test section.

Flow through model
Image showing flow (green arrows) into and through the model.​