Event Title

Optimized Soil Thermal Properties and Water Flux from Penta-needle Heat Pulse Probe Measurements

Presenter Information

Changbing Yang

Location

ECC 216

Event Website

https://water.usu.edu/

Start Date

3-31-2008 7:20 PM

End Date

3-31-2008 7:25 PM

Description

Soil thermal properties and water flux measurements are desired for understanding water and heat transport phenomena in the vadose zone, quantifying infiltration, runoff and subsurface processes and are of great interest in many scientific and engineering applications where water fluxes and temperatures are required. An accurate method for determination of in-situ water flux is the holy grail of hydrologic measurement given the long-standing interest in- and lack of-such a measure. Heat pulse velocity flux has been considered as a surrogate indicator of water flux using multi-needle probes and linesource analytic or numeric models. Here we present an inverse fitting method to estimate thermal diffusivity, thermal conductivity, and heat velocities simultaneously in x- and y- directions. Fitted temperatures are calculated from an analytical solution derived based on an infinite line heat source, which yields a Jacobian matrix using the Marquardt solution. These estimates provide an approximation of water flux within a plane normal to the sensor needles. This inverse method has been implemented in a Fortran program, INVWATFLX. The inverse method was first tested with two synthetic simulations and then applied to a laboratory experiment. Results demonstrate the inverse method provides reliable estimation of soil thermal properties and water flux from temperature measurements of the PHPP. When considering a minimum temperature-time data set (T(t)) for parameter fitting, a minimum cut-off time of 60 seconds is suggested.

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Mar 31st, 7:20 PM Mar 31st, 7:25 PM

Optimized Soil Thermal Properties and Water Flux from Penta-needle Heat Pulse Probe Measurements

ECC 216

Soil thermal properties and water flux measurements are desired for understanding water and heat transport phenomena in the vadose zone, quantifying infiltration, runoff and subsurface processes and are of great interest in many scientific and engineering applications where water fluxes and temperatures are required. An accurate method for determination of in-situ water flux is the holy grail of hydrologic measurement given the long-standing interest in- and lack of-such a measure. Heat pulse velocity flux has been considered as a surrogate indicator of water flux using multi-needle probes and linesource analytic or numeric models. Here we present an inverse fitting method to estimate thermal diffusivity, thermal conductivity, and heat velocities simultaneously in x- and y- directions. Fitted temperatures are calculated from an analytical solution derived based on an infinite line heat source, which yields a Jacobian matrix using the Marquardt solution. These estimates provide an approximation of water flux within a plane normal to the sensor needles. This inverse method has been implemented in a Fortran program, INVWATFLX. The inverse method was first tested with two synthetic simulations and then applied to a laboratory experiment. Results demonstrate the inverse method provides reliable estimation of soil thermal properties and water flux from temperature measurements of the PHPP. When considering a minimum temperature-time data set (T(t)) for parameter fitting, a minimum cut-off time of 60 seconds is suggested.

https://digitalcommons.usu.edu/runoff/2008/Posters/1