β Scribed by J. D. Coleman
No coin nor oath required. For personal study only.
A method is devised for measuring soil thermal diffusivity in situ. It is based on direct experimental simulation of the finite difference approximation to the one-dimensional heat conduction equation.
The method does not require the soil to be homogeneous except between the three thermometers that are used, at depths z + d, z and za! Nor need the energy input curve be sinusoidal. However, it must be fairly smooth for the finite difference approximation to be accurate. Experimental results for London Clay are presented, obtained using thermometers at depths of I, 6 and I I cm to give a mean thermal diffusivity of 0.0074 cmz/s at a depth of 6 cm. This value is consistent with other estimates of diffusivity for clay soils.
The method is capable of automation, and should be suitable for use on engineering sites, at low cost.
The method is capable of generalization to other linear diffusion equations containing one independent parameter. The same limitation also applies to its application to constitutive or geometrical non-linear one dimensional diffusion equations, and each equation requires individual study to assess feasibility of use of the method.
The method in effect uses the usual finite difference approximation, not to prepare a numerical solution, but to design an experiment carried out essentially within the finite difference 'molecule'. The measured parameter of the diffusion equation is the usable product of the method.
π SIMILAR VOLUMES
A time domain unconditionally stable explicit method is presented which may be used to model processes governed by the diffusion equation such as transient heat flow. Unlike the explicit finite difference routine, the method models the diffusion process within the time step (MPWT). Being explicit, t
A parallel numerical finite difference model, employing the self-implicit method, for coupled heat and moisture transfer in unsaturated soil is presented. The model is programmed in Occam and executed on a parallel computing network of transputers. An assessment of the model was achieved via the sim