Numerical and Experimental Investigation of Thermal Signatures of Buried Landmines in Dry Soil

[+] Author and Article Information
F. Moukalled, H. Kabbani, N. Khalid

Faculty of Engineering and Architecture,  American University of Beirut, Beirut, Lebanon

N. Ghaddar1

Faculty of Engineering and Architecture,  American University of Beirut, Beirut, Lebanonfarah@aub.edu.lb

Z. Fawaz

 Ryerson University, School Aerospace Engineering, Toronto, Canada, M5B 2K3


Corresponding author.

J. Heat Transfer 128(5), 484-494 (Oct 25, 2005) (11 pages) doi:10.1115/1.2176681 History: Received April 27, 2005; Revised October 25, 2005

This paper reports a numerical and experimental investigation conducted to study the thermal signature of buried landmines on soil surface. A finite-volume-based numerical model was developed to solve the unsteady three-dimensional heat transport equation in dry homogeneous soil with a buried mine. Numerical predictions of soil thermal response were validated by comparison with published analytical and numerical values in addition to data obtained experimentally. Experiments were performed inside an environmental chamber and soil temperatures were measured during cooling, using two measurement techniques, after exposing the soil surface to a radiant heat flux for a specified period. In the first technique, the temporal variation of the surface and internal soil temperatures were recorded using thermocouples. In the second technique, the soil surface temperature was measured using an infrared camera that revealed the thermal signature of the mine. The transient temperature profiles generated numerically agreed with measurements, and the difference between predicted and measured values was less than 0.3°C at both the soil surface and in depth. The accurate matching of numerical and IR images at the surfaces was found to strongly depend on the use of a smaller soil thermal conductivity at the surface than at greater depths. The numerical model was used to predict the dependence of the peak thermal contrast on time, depth, and heating period. The thermographic analysis, when combined with numerical predictions, holds promise as a method for detecting shallowly buried land mines.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

The soil bed and the embedded mine

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Figure 2

A schematic showing the treatment of the diffusion term

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Figure 3

A plot showing (a) comparison of soil temperature profiles generated numerically and analytically for the semi-infinite heat conduction problem, (b) comparison of predicted soil temperature profiles in the presence of a buried mine against those reported by Khanafer and Vafai (12)

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Figure 4

A schematic of (a) the side view of the experimental setup and (b) the top view of the soil bed

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Figure 5

The computational domain

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Figure 6

The variation in time of the predicted and measured temperatures at the center of the mine surface at z=0.01m, and the soil surface at the reference point at depths of 0.45cm, 1.05cm, 1.8cm, and 4.5cm for a test conducted in the environmental chamber while heating the soil bed for a period of 5min and then cooling by (a) radiation and forced convection with the fan turned on and (b) radiation and natural convection with the fan turned off

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Figure 7

The test results of the soil surface temperature above the mine center predicted by the numerical model and measured by the infrared camera at 1min intervals for a mine burial depths of 0.005m, and 0.01m with a heating period of 5min and a burial depth of 0.0075m with a heating period of 10min

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Figure 8

(a) The soil bed reference image at steady conditions of the environmental chamber, and the IR camera image during the cooling period, and the temperature distribution plot along a line on the surface of the soil for the experiment whose data were discussed and shown in Fig. 6; (b) the IR camera image, the 3-D temperature distribution of the surface as generated by the mapping algorithm from the IR images at 5min and 10min from the onset of cooling, and the corresponding surface images generated by the numerical model. (Heating period=5min, mine depth=0.01m, T∞=25°C, RH=50%.)

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Figure 9

A plot of the predicted thermal contrast, and the measured thermal contrast using the IR images and the thermocouples’ readings as a function of time for (a) burial depth of 0.005m (5min heating), and 0.0075m (10min heating) and (b) burial depth of 0.01m (5min heating)

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Figure 10

A plot of the thermal contrast as a function of time for (a) a heating period of 5min, (b) a heating period of 20min at different mine depths, and (c) different heating periods at fixed mine depth for the same climatic conditions of the indoor experiments considered in this work

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Figure 11

The variation with depth of (a) the peak thermal contrast and (b) the time of the peak occurrence




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