# Frost 3D Universal Verification

Frost 3D Universal Has Been Verified Against the Exact Analytical Solution

The generally accepted criterion used to determine the validity of a numerical solution is its coincidence with the known exact analytical solution, and Frost 3D Universal was verified against the analytical solution for the soil freezing problem .

Problem Statement

The 30-day temperature distribution on a section of frozen ground is calculated for the following conditions:
• a +5 oС initial soil temperature
• a constant -10 oС is maintained on the upper surface of the soil
• zero heat flow at the side and bottom surfaces of the soil section due to insulation

Table 1: Thermophysical Properties of Soils

 The Number of Computation Soil Thermal Conductivity, W/(m×°С) Volumetric Heat Capacity of Soil, kJ/(m3×°С) Frost Depth, m T ≥ 0 oС T < 0 oС T ≥ 0 oС T < 0 oС Numerical Computation Analytical Solution 1 0.64 0.7 1600 1470 0.2000 0.2011 2 0.64 0.7 3780 2730 0.1875 0.1879 3 2.73 2.9 1600 1470 0.4125 0.4140 4 2.73 2.9 3780 2730 0.3800 0.3816

The dependence of thermophysical properties on temperature (see Table 1) in compliance with the SNiP “Bases and Foundations on Permafrost” is typical for sand, loamy sand and sandy loam with plasticity index Ip < 0.02.

The comparison (Figure 1–4) of the derived numerical and the exact analytical solution for the soil freezing problem revealed a 0.5% error in the frost depth calculation using Frost 3D Universal, and we observe that mesh refinement makes the error approach zero.

Comparison of the solutions obtained in Frost 3D Universal and the exact analytical solution: Figure 1: Results of 1st numerical experiment Figure 2: Results of 2nd numerical experiment Figure 3: Results of 3rd numerical experiment Figure 4: Results of 4th numerical experiment

Frost 3D Universal Verification Against Experimental Data

The freezing of a cylindrical sample of peat with a moisture content of wtot = 5 kg/kg and density ρd =160 kg/m3 was analyzed . The following thermophysical properties are applied in compliance with SNIP 2.02.04-88 “Bases and Foundations on Permafrost”: volumetric heat capacity of thawed (Cth) and frozen (Cf) states, heat conductivity of thawed (λth) and frozen (λf) states (Table 2).

Table 2: Thermophysical Properties of Soils

 λth, W/(m×°С) λf, W/(m×°С) Cth, kJ/(m3×°С) Cf , kJ/(m3×°С) 0.41 0.70 3320 2100

The dependence of the unfrozen water content on temperature is given for peat in compliance with SP 25.13330.2012 (SNiP 2.02.04-88). From the expression (B.5), the dependence takes the form shown in the Figure 5. Figure 5: Dependence of unfrozen water content on the temperature

The initial temperature of the peat sample is 283 K. Using directional freezing apparatus, the temperature at the end of the cylindrical sample is maintained at 268 K. The experimental temperature distribution data resulting from the freezing of the sample is presented in Figure 6 . Note that this laboratory experiment is comparable to the natural processes of ground freezing. Figure 6: Computational (1, 2) and experimental (1’, 2’ ) temperature distribution and moisture content after freezing: W = 5 kg/kg, ρ = 160 kg/m3, T0 = 283 К, Tc = 268 К, t = 2.0 h 

The computational experiment was conducted in a Frost 3D Universal simulation of the same problem. The computed temperature distribution was compared with the experimental data (figure 7), and the discrepancy between the two for the depth of frost penetration was 5%: a 0.020 m computational value for frost depth against the 0.019 m experimental measurement of the same. Note that the main contribution to the total error is the inaccurate determination of the thermophysical properties of the soil. Figure7: Comparison of computational and experimental data

REFERENCES

1. Kislitsin A.A., Shabarov A.B. Heat and Mass Transfer. – Tyumen: TGU, 2007.
2. Brovka G.P. Interrelated Processes of Heat and Mass Transfer in Dispersive Media. – Minsk: Belarus. Nauka, 2011. ### Software for thermotechnical calculations of:

• Highways and railways
• Thermal stabilization of permafrost
• Artificial ground freezing

Examples of projects: Thermal Analysis of a Road on Permafrost Simulation of Groundwater Flow in Saturated Soil Computer Simulation of Ground Freezing Under Oil Tank Prediction of Ground Thaw Formations Around an Oil Well Thermal Analysis of Oil Pipeline in Permafrost Thermal Analysis of a Lengthy Section of a Gas Pipeline on Permafrost Computer Simulation of Artificial Ground Freezing During the Building of Underground Tunnel Simulation of Ground Freezing Around the Perimeter of the Fukushima Nuclear Power Plant

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