Shao-Yiu Hsu

Pore-scale analysis of the effects of contact angle hysteresis on blob mobilisation in a pore doublet

The mobilisation of residual oil blobs in porous media is hampered by the so-called Jamin effect. We studied the Jamin effect experimentally in a pore doublet model and explain it through contact angle hysteresis. We measured the contact angles (in 2D and 3D) and the mean curvatures of a blob trapped in the pore doublet model. Due to gravity effects and hysteresis, the contact angles were initially (subject to zero pressure gradient) non-uniform and exhibited a pronounced altitude dependence. As the pressure gradient was increased, both the altitude dependence and non-uniformity of contact angles decreased, and the mean curvature of the drainage and imbibition interfaces increased and decreased, respectively. The predicted pressure drops inferred from our theory were in line with the directly measured ones. We also developed methods to measure contact angles and mean curvatures in 3D.

The dynamic response of the water retention curve in unsaturated soils during drainage to acoustic excitations

We examined the effects of acoustic excitations on the water retention curve, i.e., the relationship between capillary pressure (PC) and water saturation (SW) in unsaturated porous media, during drainage. The water retention curves were measured under static and dynamic conditions, where water was withdrawn from a sandbox with three different pumping rates, 12.6, 19.7, and 25.2 mL/s. Excitations with frequencies of 75, 100, 125, and 150 Hz were applied. The acoustic excitations had no effect on the static water retention curve but altered the dynamic water retention curve. The acoustic excitations lowered the dynamic PC, especially under the dynamic condition where the pumping rate was 25.2 mL/s and when SW varied between 0.6 and 0.95. The differences between the capillary pressures measured under static and dynamic conditions decreased when acoustic excitations were applied. We link this finding to the change in contact angle induced by the acoustic excitation. The dynamic coefficients, τ, for the dynamic water retention curves that we fitted to the experimental data were smaller with than without acoustic excitations. We attribute the decrease of the dynamic coefficient to the combination of the increase in the permeability and the decline in the air-entry pressure caused by adding acoustic excitations.

Application to Reservoir Operation Rule-Curves

Researches in reservoir operation rules had already been studied more than half a century but much still remains to be done. Besides, as a result of global climate change and many nature or human causes, make the frequency and intensity of a lot of hydrological events such as drought and flood change, the existing reservoir operation rules need to change. This paper aims at reservoir operation rule -curves in detail, and applies to the newly rising evolution alg orithms to optimize reservoir operation systematically. Furthermore, the study detects the drought events by the prediction data and water resource system model, optimizes the double -group rule-curves and makes the water resources more effectively. The LiYuTan reservoir in Taiwan, for example, establish, the up -to-date operation rule.

Effects of liquid layers and distribution patterns on three-phase saturation and relative permeability relationships: a micromodel study

In the current study, we used micromodel experiments to study three-phase fluid flow in porous media. In contrast to previous studies, we simultaneously observed and measured pore-scale fluid behavior and three-phase constitutive relationships with digital image acquisition/analysis, fluid pressure control, and permeability assays. Our results showed that the fluid layers significantly influenced pore-scale, three-phase fluid displacement as well as water relative permeability. At low water saturation, water relative permeability not only depended on water saturation but also on the distributions of air and diesel. The results also indicate that the relative permeability–saturation model proposed by Parker et al. (1987) could not completely describe the experimental data from our three-phase flow experiments because these models ignore the effects of phase distribution. A simple bundle-of-tubes model shows that the water relative permeability was proportional to the number of apparently continuous water paths before the critical stage in which no apparently continuous water flow path could be found. Our findings constitute additional information about the essential constitutive relationships involved in both the understanding and the modeling of three-phase flows in porous media.

Design and implementation of the TAROGE experiment

Taiwan astroparticle radiowave observatory for geo-synchrotron emissions (TAROGE) is an antenna array on the high mountains of Taiwan’s east coast for the detection of ultra-high energy cosmic rays (UHECRs) in an energy above 1018.5eV. The antennas point toward the ocean to detect radiowave signals emitted by the UHECR-induced air-shower as a result of its interaction with the geomagnetic field. Looking down from the coastal mountain, the effective area is enhanced by collecting both direct-emission as well as the ocean-reflected signals. This instrument also provides the capability of detecting earth-skimming tau-neutrino through its subsequent tau-decay induced shower. In order to prove the detection concept, initial two stations were successfully built at 1000m elevation near Heping township, Taiwan, in 2014–2015. Each station consists of 12 log-periodic dipole array antennas for 110–300MHz. The stations have been operating smoothly for radio survey and optimization of instrumental parameters. In this report, we discuss the design of TAROGE, the performance of the prototype station and the future prospect.