Wind effects on dual probe heat pulse method measured soil thermal properties

Abstract

<p>When a dual probe heat pulse (DPHP) sensor is installed in soil near the soil-atmosphere interface, the basic assumptions of the infinite line heat source (ILS) model and its improvement, the infinite line heat source model with an adiabatic boundary condition (ILS-ABC), might not be satisfied because of wind. This study aims at exploring the effects of wind on DPHP measurements and comparing the performance of the ILS and ILS-ABC models with different values of wind velocity (υ) and burial depth (d). Our study shows that the results of laboratory experiments, COMSOL simulations, and field experiments are consistent with each other. For dry sand with d ≤ 4 mm, the effects of wind is non-negligible when υ ≥ 3.5 m s-1, and the DPHP method does not provide accurate estimations whether the ILS model or the ILS-ABC model is used. Field experiments are prone to large background temperature fluctuations which can cause the linear de-trend method of Jury and Bellantuoni (1976) to perform poorly. In general, υ is less than 2.7 m s-1 in field and for d = 5 mm the ILS-ABC model provides more accurate estimations with relative error < 15% in thermal conductivity (λ) and relative error < 9% in heat capacity (c).</p>