Improved predictions of thermal fluid pressurization in hydro-thermal models based on consistent incorporation of thermo-mechanical effects in anisotropic porous media. (June 2021)

• Record Type: Journal Article
• Authors: Buchwald, J.; Kaiser, S.; Kolditz, O.; Nagel, T.
• Is Part Of: International journal of heat and mass transfer. Volume 172(2021)
• Publication Date: 2021-06
• Subjects: thermo-hydro-mechanical -- hydro-thermal -- radioactive waste -- geological repository -- specific storage -- model complexity reduction -- OpenGeoSys; 74-10 -- 74F05 -- 74F10 -- 74E10; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2021.121127
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: two thermo-hydro-mechanical models are derived with simplified representations of thermo-mechanical effects exact agreement between both complexity-reduced models and the fully coupled thermo-hydro-mechanical model if basic simplifying assumptions hold good agreement can still be reached if basic simplifying assumptions are violated complexity-reduced models allow for scoping evaluation with computational efficiency of a hydro-thermal model Abstract: Coupled thermo-hydro-mechanical models are commonly used to model the evolution of temperature, pore pressure, and stress in a wide range of geotechnologies such as geothermal applications or around canisters of high-level radioactive waste in deep underground storage facilities. Their numerical modeling is often computationally highly demanding, especially if parameter identification, sensitivity analyses or uncertainty quantification require many model evaluations. Often, the thermally driven pore pressure evolution and the subsequently altered flow processes are the primary targets of an analysis. To benefit from the computational efficiency of hydro-thermal (HT) models while maintaining the accuracy of the thermo-hydro-mechanical (THM) model, we derived two cases of a simplified representation of mechanical deformations in a coupled hydro-thermal model. Deformations induced by pressure as well as temperature changes are consistently incorporated into the mass balance storage terms. We demonstrate the exact coincidence of THM and modified TH formulations in isotropic and orthotropic materials as long as the basic assumptions like constant hydrostatic stress conditions or uniaxial strain hold. By modeling of a point heat source in isotropic or anisotropic porous media it is shown that a good agreement between TH and THM models can be maintained even though the assumptions underlying the simplification are no longer valid exactly. On our test-machine, a significant speed-up could be achieved by the reduction of the problem size when transitioning from a THM to a TH model. The highest speed-ups were achieved when Taylor-Hood elements were employed in order to avoid the problem of spurious pressure oscillations in the fully coupled THM model.