## 3 RIM Formulation Summary, Discussion, and Prospects  
### RIM Formulation Summary  
A summary of the solid and liquid materials used for RIM realization is presented according to different application areas and topics in Tables 1-4. These tables are intended for researchers to select materials relevant to their fields. Table 1 summarizes solid and liquid materials in porous media-fluid interaction, focusing mainly on hydraulic engineering. A multitude of solid materials can be used for RIM in this field, e.g., borosilicate glass and hydrogel, among others. \begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt} p{142.3 pt} p{142.3 pt}} \hline \hline
**Topic** & **Solid** & **Liquid** & **References** \\ \hline
1. Turbulent flows over and through rough porous beds & Borosilicate beads & A mixture of 40\% ethanol and 60\% benzyl alcohol by volume (1) KSCN solutions (2) mixtures of Drake and soybean oil with different mass fractions & [1] \\
2. In-situ measurement of the refractive index of a porous medium in RIM experiments & Borosilicate glass beads (Sigma-Aldrich, Z273619) & Borosilicate glass beads (Sigma-Aldrich, Z273619) & (1) KSCN solutions (2) mixtures of Drake and soybean oil with different mass fractions & [46] \\
3. Flow characterization of low aspect ratio randomly packed porous bed & Beads 15 mm diameter (Pyrex®) & Aqueous solution of NH4 SCN & [72] \\
4. Measuring porous flow characteristics & Hydrogel beads & Water & [42] \\
5. Destabilization by localized fluidization of a dense granular material & Hydrogel beads & Water & [73] \\
6. Pore-scale turbulent characteristics in porous media & Polymethyl methacrylate (acrylic) & p-cymene & [43] \\
7. Foam-like porous structure; 3-D print & Epoxy resin (WaterShed® XC 11122) & Epoxy resin (WaterShed® XC 11122) & Anisole (Sigma–Aldrich) & [74] \\
8. Mobile granular layer for the sediment transport of spherical particles & Borosilicate; PMMA & Water (15 wt%)+Triton X\(-\)100 & [75] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Hydraulic/mechanical engineering: porous media-fluid interaction. For applications in geotechnical engineering, choices of transparent soils are listed in Table 2. Glasses (fumed silica, fused quartz, etc.) are widely used due to their low cost and ready availability. In addition, several commercially available synthetic clays facilitate the production of transparent soil. Table 3 provides a summary of the RIM formulations used to study the transport of contaminants in flow or soil. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Topic** & **Solid** & **Liquid** & **References** \\ \hline
9. Inertia dominated, transitional and turbulent flow & PMMA & an aqueous solution of NH4 SCN & [44] \\
10. Map interstitial flow & THV(manufactured by wood, MN, USA)) & Deionized water mixed with 24.2\% glycerin by weight & [76] \\
11. Turbulent flow inside a complex canopy & UOPTIC (manufactured by Forecast 3D) & An aqueous NaI solution & [47] \\
12.The dynamic interplay between surface and subsurface flow in the presence of a permeable boundary & acrylic resin (Crystal Clear 204) & An aqueous NaI solution & [77] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._