Circumstellar disks and planets. Science cases for next-generation optical/infrared long-baseline interferometers

We present a review of the interplay between the evolution of circumstellar disks and the formation of planets, both from the perspective of theoretical models and dedicated observations. Based on this, we identify and discuss fundamental questions concerning the formation and evolution of circumstellar disks and planets which can be addressed in the near future with optical and infrared long-baseline interferometers. Furthermore, the importance of complementary observations with long-baseline (sub)millimeter interferometers and high-sensitivity infrared observatories is outlined.Comment: 83 pages; Accepted for publication in "Astronomy and Astrophysics Review"; The final publication is available at http://www.springerlink.co

Influence of groundwater flow on the estimation of subsurface thermal parameters

We investigated the influence of groundwater flow on the thermal tests performed in borehole heat exchangers to infer the underground thermal properties. Temperature\u2013time signals were simulated with a moving line source (MLS) model under different hypotheses of Darcy velocity. Periodic and random noise was included in the synthetic data obtained with this model in order to mimic high-frequency disturbances caused by several possible sources (e.g. equipment instability and changes in environmental conditions during the experiment) that often occur in real signals. The subsurface thermal conductivity, the Darcy velocity and the borehole thermal resistance were inferred by minimising the root-mean-square error between the synthetic dataset and the model. The calculated thermal and hydraulic parameters were consistent with the \u201ca priori\u201d values. The optimisation procedure results were then tested with the infinite line source (ILS) model. For a Darcy velocity exceeding 10 127 m s 121, ILS largely overestimates thermal conductivity. The approach relying on the MLS model was finally tested with real temperature\u2013time data and produced reliable estimates of thermal conductivity, Darcy velocity and borehole thermal resistance. The inferred groundwater flow was cross checked by means of an independent method based on the analysis of temperature\u2013depth logs recorded under thermal equilibrium conditions. Such a test validates the Darcy velocity inferred with the MLS approach

Limitation of using heat as a groundwater tracer to define aquifer properties: experiment in a large tank model

A large tank (4 × 8 × 1.4 m) filled with loamy sediments and equipped with 26 standard piezometers and 20 multilevel temperature μloggers is used to carry out a thermal monitoring test and investigate the limits of heat as tracer to define aquifer parameters. A constant temperature test was conducted by originating a heat plume using a groundwater heat exchanger and a constant head was used to create a steady state flux. Temperature was monitored continuously during 40 days by data μloggers. To estimate aquifer parameters, a heat transport model was constructed using MT3DMS. Although the boundary conditions are well known, there is still a bias between computed and measured temperatures. Results show that in fine-grained sediments, which are thermal diffusion dominated, it is difficult to precisely distinguish and quantify diffusivity and dispersivity components without also considering solute tracer tests. In this type of alluvial sediments, using heat as groundwater tracer to define aquifer properties can be problematic, since heat transport is relatively insensitive to the longitudinal dispersivity, a relevant parameter for solute transport modeling