A numerical study of flow in micro channels and micro pipes is described. The simulations are performed by solving Navier-Stokes equations with a slip velocity boundary condition, using the LU-TVD implicit algorithm. A second-order slipping model incorporating pressure gradient is proposed and investigated. The numerical results obtained using the new slipping model are presented and found to compare well with available experimental data and numerical results from other references.Our computations also show that compressibility and the rarefied effects of gas flows are present in both micro channel and micro pipe flows. It is also found that the effect of rarefaction tends to mitigate the negative curvature of pressure distribution that can be attributed to compressibility.

Depressurization experiments of methane-hydrate-bearing sediments were conducted to measure changes within the hydrate stability region before dissociation started. Pore-filling hydrate with a saturation of about 40% was formed in water-saturated silica sand samples with a porosity of 0.4. The initial pressure was kept constant at around 14.5 MPa, and the initial temperature was varied between 281.3 and 283.7 K. When the samples were depressurized at rates ranging from −1.2 to −3.9 MPa/min, temperature increases of 0.26–0.37 K on average were measured. These were caused by a decreasing aqueous methane solubility as well as the liberation of isolated free gas, leading to additional heat-releasing hydrate formation (ΔH MH‑f = −51.86 kJ mol–1 of CH4 at 280 K). The results suggest that the solubility obeys Henry’s law as long as free methane is present in the pore space. The temperature changes during depressurization shift the equilibrium pressure, leading to an anticipated dissociation during the process. The increase in hydrate saturation, in turn, reduces the effective permeability of the formation, reducing the extent to which a formation can be depressurized by a single vertical wellbore. Sensitivity studies for the above state sediment conditions show that the induced increase in the temperature raises the equilibrium pressure of up to 0.7 MPa and raises the hydrate saturation by 7%, for an initial in situ pressure of 35 MPa and varying temperatures.

This study investigates the Taylor–Couette flow (TCF) with a longitudinal corrugated surface on a stationary outer cylinder and a rotating smooth inner cylinder using large eddy simulation for three values of amplitude to wavelength ratios (A*) (0.1875, 0.2149, and 0.25) to explore the influence of the corrugated surface on the flow structures and the variation of torque for a wider range of Reynolds numbers (Re) (60–650). From the results, four flow regimes are observed. At Re = 60, initially, a pair of secondary vortices appears at the inner wall of the minimum gap region and it evolves to a pair of axisymmetric stationary wall induced vortices (ASSWIVs) in the maximum gap region. As Re increases to 80, 85, and 103 for the three values of A* (0.1875, 0.2149, and 0.25), respectively, another pair of axisymmetric stationary secondary vortices is seen at the minimum gap region of the inner wall. A further increase in Re (Re > 125, 130, and 138 for the three values of A*, respectively) results in the appearance of axisymmetric periodic secondary axial flow. Increasing Re further (Re > 225, 240, and 260 for A* = 0.25, 0.2149, and 0.1875, respectively) leads to the emergence of non-axisymmetric and non-periodic secondary axial flow (NANPSAF) with an azimuthal wave. Generally, the torque in TCF with the corrugated surface is found to be lower than TCF with a smooth surface except for the occurrence of the ASSWIV flow regime and weak axial secondary flow in the NANPSAF regime.

Nowadays, cryogenic fluids are employed in many fields, including health care, aerospace, and maritime industries. As commonly known, these fluids are most often applied as refrigerants. For example, liquid nitrogen (LN) is used for the thermal insulation of high-temperature superconducting transformers [1]. Aside from cooling, the application of cryogenic fluids as fuels and oxidizers provides a unique economic advantage due to their high energy densities. Moreover, such cryogenic fuels as liquefied natural gas (LNG) offer a solution to the problem of growing emissions [2]. Therefore, accurate measurement of cryogenic fluids is a vital component for sustainable development today.Coriolis flowmeter (CFM) is one of the most promising tools for measuring fluids of this type. This is explained by its high accuracy, non-obstructive nature and potential suitability for multiphase metering. Due to the features of cryogenic fluids, however, multiple challenges present themselves. First of all, the non-linearity of CFM material properties is observed for low temperatures. Secondly, the composition of cryogenic fluids may vary due to the origin or the different boiling rates of components. Finally, there are challenges that are inherent for all CFMs, including environment temperature, zero shift, and external vibration influence. The complex of these challenges leads to the lower CFM accuracy for cryogenic fluids than for water, which was reported in [3]. While new CFM configurations may be developed to address these challenges, the calibration of them is required. However, currently, the calibration process is restricted significantly by cost and size limitations of experimental facilities. Therefore, a numerical calibration procedure was developed as an alternative.The presented numerical calibration includes modal and fluid-solid interaction (FSI) simulations. To ensure the reliability of simulations, space and time discretization independence studies were conducted. Additionally, modal analysis was validated by experimental data. It was demonstrated that the accuracy of calculations is acceptable and may be improved by avoiding the material properties assumption. The developed numerical calibration procedure was applied for LNG and LN metering by CFM, what may decrease the costs of experimental calibration and increase the meter application range.Finally, the suitability of developed calibration was demonstrated for the CFM's challenges study. For instance, the measurement error, which is caused by the difference of natural frequencies of empty and filled tubes, was studied. It was concluded that this error is less significant for cryogenic fluids than for water, due to its higher density. Also, the zero shift of CFM, associated with low measurement accuracy [4], was investigated. Results of FSI analysis showed that it is caused by secondary circulation and is higher for cryogenic fluids than for water. This significant increase may be one of the main reasons for the low accuracy of LNG metering. However, the develope...

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