Liquid Droplet Impact Over Hydrophobic Mesh Surfaces and Assessment of Weber Number Dependent Characteristics

Impacting droplets and droplet ejection from hydrophobic mesh surfaces have interest in biomedicine, heat transfer engineering, and self-cleaning of surfaces. The rate and the size of newborn droplets can vary depending on, the droplet fluid properties, Weber number, mesh geometry, and surface wetting states. In the present study, impacting water droplets onto hydrophobic mesh surface is investigated and impact properties including, spreading, rebounding, and droplet fluid penetration and ejection rates are examined. Droplet behavior is assessed using high recording facilities and predicted in line with the experiments. The findings reveal that the critical Weber number for droplet fluid penetrating/ejecting from mesh screen mainly depends on the droplet fluid capillary length, and hydrophobic mesh size. The contact time of impacting droplet over mesh surface reduces with increasing droplet Weber number, which opposes the case observed for impacting droplets over flat hydrophobic surfaces. The restitution coefficient attains lower values for impacting droplets over mesh surfaces than that of flat surfaces. The rate and diameter of the ejected droplet from the mesh increases as droplet Weber increases. At the onset of impact, streamline curvature is formed inside droplet fluid, which creates a stagnation zone with radially varying pressure at the droplet fluid mesh interface. This reduces the ejected droplet diameter from mesh cells as mesh cells are located away from the impacting vertical axis.

Geomechanical aspects of induced microseismicity during CO2 injection in Illinois Basin

Carbon sequestration activities are increasing in a global effort to mitigate the effects of greenhouse gas emissions on the climate. Injection of wastewater and oil-field fluids is known to induce seismic activity. This makes it important to understand how that risk relates to CO2 injection. Injection of supercritical CO2 into the Cambrian Mt. Simon sandstone in Illinois Basin induced microseismicity that was observed below the reservoir, primarily in the Precambrian crystalline basement. Geomechanical and flow properties of rock samples from the involved formations were measured in the laboratory and compared with geophysical log data and petrographic analysis. The controlling factors for induced microseismicity in the basement seem to be the hydraulic connection between the reservoir and basement rock and reactivation of pre-existing faults or fractures in the basement. Additionally, the presence of a laterally continuous low-permeability layer between reservoir and basement may have prevented downward migration of pore pressure and reactivation of critically stressed planes of weakness in the basement. Results of the geomechanical characterization of this intermediate layer indicate that it may act as an effective barrier for fluid penetration into the basement and that induced microseismicity is likely to be controlled by the pre-existing system of faults. This is because the intact material is not expected to fail under the reservoir stress conditions.

Precision delivery of liquid therapy into the arterial wall for the treatment of peripheral arterial disease

Perfusion catheters have recently emerged as a novel approach to deliver liquid anti-proliferative agents into flow obstructed arterial segments. The purpose of this study was to determine the impact of luminal delivery pressure on liquid drug penetration into the vessel wall. An ex vivo model using harvested porcine carotid arteries and a two-dimensional computational model were utilized to determine the impact of delivery pressure of liquid therapy into the arterial wall. A pig peripheral injury model determined the impact of intra-luminal delivery pressure on drug retention. Ex vivo results demonstrated that depth of fluid penetration varies from 6.93 ± 1.90% at 0 atm to 27.75 ± 6.61% penetration of the medial layer at 0.4 atm. Computational results had similar outcomes, as penetration varied between 4.4% and 22.84%. The in vivo results demonstrated significant increase in drug delivery to the arterial tissue at 0.4 atm versus 0.1 atm at 1 h (23.43 ± 13.59 ng/mg vs. 2.49 ± 1.81 ng/mg, p = 0.026) and 7 days (0.50 ± 0.39 ng/mg vs. 0.018 ± 0.023 ng/mg, p = 0.0496). The result of this study provides an innovative strategic and technical approach to enable targeted liquid therapy.

Analysis of the Effects of Biological Activities on some Structures in Cross River State and the Federal Capital Territory, Abuja, Nigeria

Engineering structures are constantly subject to damage caused by biological activities such as the action of insects, penetration of roots and fluids. Because of this, we conducted a critical study on how these activities contribute to the collapse of these structures in Nigeria. The damage caused by biological activities was evaluated in fifteen buildings in Cross River State, of these buildings six showed damage caused by termites, two of the failed engineering structures were linked to development of roots of plants, and the remaining seven were linked to poor quality building materials, poor compaction, lack of supervision, poor engineering design. Others ten structurally failed buildings were examined in the Federal Capital Territory Abuja, Nigeria, of these four were linked to biological activities of termites, with subsurface porosity showing evidence of surface water discharge zones, two of the failed structures were linked to the growth activities of roots of trees, and four to poor construction design. The road that links Cross River State to Abuja had more than 80 points of failure, the majority of which were linked to poor compaction of road foundation, root of plants and fluid interference. Such damage could be prevented through: thorough investigation of biological activities existing and likely to exist around the environment before the establishment of the engineering structure and over the years; use of bio-resistant materials, such as nano materials incorporated coatings with novel functionalities should be used in the construction of structures; protection of engineering structures from fluid penetration into foundations; and engineering structures must follow the global best practices guide lines, provided by ‘Society of Structural Engineers’.

Numerical Investigation of Wellbore Stability in Deepwater Shallow Sediments

An elaborate poro-elastoplastic numerical model has been developed in this paper to explore the stability characteristics of wellbore in shallow sediments of deepwater oil/gas wells. The combined Drucker-Prager/cap plasticity model is employed to characterize the mechanical behavior of the weakly consolidated or unconsolidated shallow sediments, by which both plastic compaction deformation and plastic shear deformation can be considered. Possible penetration of drilling fluid into the formation and its coupling to deformation have also been accounted for in the model. Using this model, deformation, stress evolution, and failure characteristics of the formation around the wellbore are analyzed in detail. Results presented in this paper demonstrate the necessity of considering the plastic compaction capability of the formation during the wellbore stability analysis of shallow sediments in deepwater. For mud pressures lower than the in situ horizontal stress, excessive wellbore shrinkage may occur if the mud pressure is too low, which, however, can be effectively mitigated through properly increasing the mud pressure even fluid penetration into the near-wellbore region may occur. It is also evidenced that, if penetration of drilling fluid into the formation is prevented, fracturing of the wellbore will not occur even the mud pressure is very high. Instead, the wellbore will expand substantially due to plastic compaction, and the deformed wellbore radius could be several times larger than the original value. However, if drilling fluid can penetrate into the formation, high pore pressure will develop within the near-wellbore region, resulting in tensile hoop stress at the wellbore and thus fracturing of the wellbore along the radial direction. The numerical results and implications in this paper are anticipated to be beneficial for the drilling operation in the shallow portion of deepwater oil/gas wells.

Study on Penetration Grouting Mechanism Based on Newton Fluid of Time-Dependent Behavior of Rheological Parameters

Grouting mechanism is one of the important factors on the grouting effects of practical projects. At present, the vast majority of Newton fluid penetration grouting mechanisms are considering that the viscosity of Newton fluid during the grouting whole process was constant, so the theoretical diffusion radius calculated by them is far greater than the actual measurements in the grouting engineering. Carrying out theoretical analysis and experimental research, the rheological equation and seepage motion equation for Newton fluid of time-dependent behavior of rheological parameters were established; then, the penetration grouting mechanism of them was deduced. What is more, they were validated by means of designing the grouting verifying experiments. Experiment results show that the theoretical diffusion radius calculated by the formula of diffusion radius of penetration grouting mechanism based on Newton fluid of time-dependent behavior of rheological parameters was in accordance with the change regulation of the actual measurement diffusion radius by grouting experiments. Their difference within the range of 15% is far less than about 80% change between the theoretical diffusion radius calculated by the Maag formula and the actual measurement radius. In general, it can reflect the grout infiltration laws that Newton fluid changes with time. Therefore, research achievements may not only be able to provide a strong theoretical basis for perfecting the penetration grouting mechanism but also play a reference guiding role for the theoretical research, design, and construction in the grouting technique.