Internal Fluid Research Articles

Internal sound pressure and power radiation from a submerged cylindrical enclosure with interior acoustic excitation

This paper presents the modelling and analysis of the effect of an interior acoustic excitation on a submerged cylindrical enclosure. The enclosure has ring stiffeners and acoustic absorption material on the internal wall. The acoustic excitation generates an incident and scattered sound field inside the enclosure. The incident and scattered sound forms the internal pressure which induces a structural response and, thus, the radiated sound. The previous work (James 1985) with an internal noise source located on the vertical axis is expanded to allow forces and interior acoustic sources at arbitrary locations. The formulation of the internal pressure is developed by solving the unknown coupling term between the internal fluid and the hull. The coupling term was neglected by James (1985). However, this term is significant in magnitude for the internal pressure and must, therefore, be included. The analytical results are compared with numerical finite element/boundary element models with good agreement.

Influence of cellulose nanofiber fluid on flow instability and heat transfer of two-phase closed thermosyphon

In this research, the geyser phenomenon occurring in a small-diameter two-phase closed thermosyphon (TPCT) was observed and the instability of the device was discussed. Geyser phenomena interfere with the natural circulation of internal working fluids, increasing the thermal resistance of the system and contributing to the instability of the device. This study attempts to improve the thermal performance and stability of the system using cellulose nanofiber (CNF) fluid as the working fluid. The use of CNF fluid was observed to reduce the magnitude of temperature change inside the evaporator of the TPCT significantly. Moreover, it improved the local boiling heat transfer coefficient by 3.1 %, 87.3 %, and 181.2 % on average when the filling ratios are 0.25, 0.5, and 0.75, respectively. Studying the local heat transfer performance and instability will be helpful in designing a more stable TPCT efficiently. Additionally, the findings of this study can be applied to solar thermal power generation or heat pipe research for cooling strategies in computing servers, depending on the input heat load.

Effect of Robin boundary conditions on the onset of convective torsional flows in rotating fluid spheres

Torsional flows are preferred at the onset of thermal convection in fluid spheres with stress-free and perfectly conducting boundary conditions, in a narrow region of the parameter space for Prandtl numbers Pr≲0.9 and ratios Pr/Ek=O(10), with Ek being the Ekman number. In this case, the transport of heat to the exterior is supposed instantaneous. When the thermal conductivity of the internal fluid is large, and the external convective heat transfer or radiative emissivity is low, the heat transmission is less efficient, and the thermal energy retained in the interior increases, enhancing the onset of convection. This study is devoted to analyzing the combined influence of the thermal conductivity and external conditions (temperature and resistance to heat transport) on the onset of the torsional convection by taking a Robin boundary condition for the temperature at the surface of the sphere. It is shown, by means of the numerical computation of the curves of simultaneous transitions to torsional flows and Rossby waves, that when the heat flux through the boundary decreases, the region where the axisymmetric flows are preferred shrinks, but it never strangles to an empty set. It has been found that with adequate scalings the curves delimiting the transition to torsional flows, and those of the critical Rayleigh number, Rac, and the frequencies of the modes vs Ek become almost independent of the parameter of the Robin boundary condition.

Vortex-induced vibration characteristics of mining riser under the coupling effect of external ocean current and internal multiphase flow

As an important equipment for deep-sea oil and gas development, riser is prone to failure due to external ocean environmental load and internal fluid in the process of oil and gas exploitation. In this paper, a dynamic analysis model of the riser system under the action of internal and external flow coupling is established. This model is discretized by using the finite element method and solved by Newmark-β method. The vortex-induced vibration characteristics of the mining riser under the action of internal and external flow coupling are analyzed. Results show that compared with the traditional riser containing pure liquid flow, gas–liquid two-phase flow in pipe can reduce the natural frequency of the riser and increase the vibration amplitude and frequency. The natural and vibration response frequencies of the riser decrease with the increase in the discharge rate and the density of the two-phase mixture, and the modal response remains unchanged. With the increase in the air inlet ratio, the natural frequency of the riser decreases, but the vibration frequency increases, and induces the vibration of higher modes of the riser.

Investigation on the pressure and flow characteristics for a high-speed bullet in high-altitude flight

The pressure analysis and flow characteristics during the flight of a high-speed bullet are significant for aerodynamic performance, flight trajectory control, safety and reliability, performance optimization, guidance and navigation. To accurately monitor the pressure variation for a high-speed bullet in the high-altitude flight, a novel local fluid domain method is introduced in current study. This method overcomes the limitations of conventional global fluid domain simulation methods, which often suffer from poor convergence and stability issues. On the basis, the force analysis is conducted and the mathematical model for the theoretical trajectory is established, which is applied to simulate the flight trajectory and construct fluid domain for the high-speed bullet. The findings reveal that monitoring points within the bullet hole are influenced by both cavity flow and the collision of forward airflows during the high-altitude flight. Furthermore, it is observed that the absolute total pressure and reference pressure at these monitoring points within the bullet hole are influenced by altitude variations. Subsequently, the factors affecting the absolute total pressure within the hole are explored, including the hole depth, the hole diameter, the hole position, and the bullet orientation. The results indicate that modifying the bullet structure to incorporate 45° angled hole, as opposed to standard holes, can lead to a 13.6% reduction in absolute total pressure variation. Additionally, mitigating the interaction between the external and internal fluids emerges as a critical factor in reducing absolute total pressure within the hole. This research not only presents a fresh perspective for pressure monitoring within the bullet hole, but also establishes a theoretical foundation for the precise guidance of high-altitude bullets.

Design and numerical study of active cooling system of measurement while drilling for high temperature based on supersonic

Measurement while drilling (MWD) plays an important role in controlling well trajectory, improving drilling efficiency and saving drilling cost. In recent years, a large number of high-temperature wells have appeared, which makes the traditional MWD instruments no longer applicable. So far, no active cooling method has been successfully applied to MWD instruments for high-temperature oil and gas wells. This paper presents a new active cooling method for air drilling by utilizing the throttling and cooling of drilling gas, and the cooling system is designed. An axisymmetric numerical model of internal fluid is established, and different drilling gas flow channel design methods are discussed. The research results indicate that the wall temperature of the cooling section is much higher than the center fluid temperature, but lower than the ambient temperature, and can be used for active cooling of downhole drilling instruments. Compared with other design methods, the supersonic nozzle designed using the Bezier method has better parallelism of the gas in cooling section. The diffusion capability of straight wall diffuser is better than that of curved wall diffuser, and it can withstand greater back pressure. For straight wall diffuser, increasing the throat length and reducing the contraction and expansion angle can improve the diffusion capacity, but they also lead to a longer diffuser.

Investigation of cross-scale characterization of porous structure and fluid index in bituminous coal via microwave-LN2 freeze-thaw cycles

Microwave-LN2 cyclic processing (MLCP) is a clean and high-efficiency anhydrous fracturing technology. The change in the porous structure of coal after freeze-thaw cycles significantly affects development efficiency of coalbed methane (CBM) in low porosity and permeability reservoirs, while there is a lack of in-depth macro-meso-micro studies. The damage mechanism of coal under microwave-LN2 cold and thermal shock and the evolution of pore fluid reservoir space is based on cross-scale pore characterisation. This paper evaluates the multi-scale porous structure variations of coal before and after MLCP was assessed by hydrogen nuclear magnetic resonance (1H NNR) and field emission scanning electron microscopy (FE-SEM). The evolutionary trends in coal pore fluid fugacity space under freeze-thaw cycles was indirectly characterised by T1-T2 spectra. Additionally, utilizing T2 distribution, peak area and pore throat changes reflect the evolution trend of coal pore space. The results indicate that as the cycles increased, the coal free water and total fluid reservoir space gradually expanded beyond the cycle threshold (n > 10), the free-fluid index rose to 25.68 %, and the free fluid saturation increased by 20.39 %. Additionally, the NMR permeability of the coal increased by 98.37–1471.65 %, and the pore throat distribution increased by 28.05 %. Comprehensive analysis showed that as the cycles progressed, the free water space in the pore space increased significantly, the proportion of bound water gradually decreased, and the internal pores and fluid space of the coal were improved. This study provides fundamental support for multidimensional evaluation of the porous structure of microwave-LN2 freeze-thaw cycles.

Atypical plug formation in internal elastoviscoplastic fluid flows over non-smooth topologies

An experimental and computational investigation of the internal flow of elastoviscoplastic fluids over non-smooth topologies is presented in two complimentary studies. In the first study, we visualize the creeping flow of a Carbopol gel over a cavity embedded in a thin slot using Optical Coherence Tomography (OCT) and confocal microscopy. We measure the size and shape of the plug as a function of Bingham and Weissenberg numbers. An asymmetry in the plug shape is observed which is also evident in our second study—numerical simulations using adaptive finite element method based upon an augmented Lagrangian scheme. We quantify the asymmetry and present the results as a function of the product of the Weissenberg and Bingham numbers which collapse onto a single curve for each of these geometries. These findings underscore the theoretical underpinnings of the synergy between elasticity and plasticity of these complex fluids.

Nonlinear dynamics of pipes composed of Mooney-Rivlin hyperelastic materials conveying unsteady fluid flow

In the present study, a mathematical model for the nonlinear dynamics of a Mooney-Rivlin type hyperelastic pipe conveying unsteady fluid flow is established. The internal fluid velocity is assumed to comprise an average component superimposed on a harmonically varying component. Subsequently, various numerical methods are employed to investigate the nonlinear responses of the pipe through the forms of amplitude-response, disturbance-response, global bifurcation diagrams, phase trajectories, Poincaré maps, and power spectral densities (PSD). Additionally, the contributions of the Coriolis force and geometric nonlinearity are examined. The results reveal that, in comparison to linearelastic pipes, the combined effect of nonlinear geometric relation and nonlinear constitutive relation introduces specific nonlinear terms, leading to distinct dynamical phenomena. With small disturbed coefficient, the asymmetric period-1 and symmetric period-2 oscillations are respectively observed in the primary and sub-critical regimes. Furthermore, the hyperelasticity and fluid-structure interactions (FSI) play significant, unequal, and competitive roles in influencing the dynamic responses of the pipe by affecting either linear or nonlinear stiffness. Additionally, abundant dynamical phenomena are captured within the system versus system parameters with large disturbed coefficient. The study also demonstrates that the combined effect of nonlinear geometric relation and nonlinear constitutive relation ultimately results in weaker hardening behaviors for Mooney-Rivlin type pipes compared to linearelastic ones.

NIR-activated acid-response “four-in-one” nanomotor for photothermal therapy, chemodynamic therapy and hypoxic-activated chemotherapy

The dense extracellular matrix (ECM) and internal fluid pressure (IFP) seriously alter the effective delivery of nanodrugs in tumour tissue. In order to solve this problem, a photothermal driven nanomotor was designed (PB@ZIF-8@TPZ, PZT), performing the function of “four in one” on the premise of minimum composition. The nanomotor can simultaneously realise PTT/CDT/hypoxia-activation-CT, GSH consumption and photothermal-driven, among which prussian blue (PB) was first found to be able to simultaneously realise photothermal-driven, GSH consumption and PTT/CDT’s “four in one” function. Nanomotor has the advantages of good stability, low cost, easy synthesis, excellent ability for deep puncture and a high anti-tumour effect.

Concentration and Thermal Analysis of immiscible Tangent hyperbolic fluid with distinct viscosity through horizontal asymmetric channel: Theoretical and Observational study

This study examines cilia induced Tangent hyperbolic fluid flow with distinct viscosity, density in addition to thermal conductivity through horizontal asymmetric channel in two adjacent layers. The impact of mass and heat transfer in two adjacent layers with continuity at the interface is considered. The governing equations for double-layer fluid flow was modelled and simplified via well-known approximation long wavelength and small Reynolds number. The subsequent equations with boundary conditions provide exact solution for the velocity profile, temperature field and concentration distribution in both layers. The outcomes of occurring parameters on temperature, velocity and concentration field are explained graphically. The major findings show that velocity field and temperature field are extreme in internal fluid layer and concentration distribution is highest at external fluid layers. In both the layers by rising viscosities, thermal conductivities, fluid parameters and temperature profile increases. Potential applications for the current work include mucus clearance from respiratory tract, microfluidics, oesophageal transport, bio fluid mechanism and other fields of physiology.

Defrosting frozen stars: Spectrum of internal fluid modes

Defrosting frozen stars: Spectrum of internal fluid modes

Assessment of Lubrication Property and Machining Performance of Nanofluid Composite Electrostatic Spraying (NCES) Using Different Types of Vegetable Oils as Base Fluids of External Fluid

The current study of minimum quantity lubrication (MQL) concentrates on its performance improvement. By contrast with nanofluid MQL and electrostatic atomization (EA), the proposed nanofluid composite electrostatic spraying (NCES) can enhance the performance of MQL more comprehensively. However, it is largely influenced by the base fluid of external fluid. In this paper, the lubrication property and machining performance of NCES with different types of vegetable oils (castor, palm, soybean, rapeseed, and LB2000 oil) as the base fluids of external fluid were compared and evaluated by friction and milling tests under different flow ratios of external and internal fluids. The spraying current and electrowetting angle were tested to analyze the influence of vegetable oil type as the base fluid of external fluid on NCES performances. The friction test results show that relative to NCES with other vegetable oils as the base fluids of external fluid, NCES with LB2000 as the base fluid of external fluid reduced the friction coefficient and wear loss by 9.4%-27.7% and 7.6%-26.5%, respectively. The milling test results display that the milling force and milling temperature for NCES with LB2000 as the base fluid of external fluid were 1.4%-13.2% and 3.6%-11.2% lower than those for NCES with other vegetable oils as the base fluids of external fluid, respectively. When LB2000/multi-walled carbon nanotube (MWCNT) water-based nanofluid was used as the external/internal fluid and the flow ratio of external and internal fluids was 2:1, NCES showed the best milling performance. This study provides theoretical and technical support for the selection of the base fluid of NCES external fluid.

A Study on the Mechanism of Casing Deformation and Its Control Strategies in Shale Oil Hydraulic Fracturing

The problem of casing deformation caused by large-scale hydraulic fracturing in shale oil wells severely restricts the efficient development of Gulong shale oil. In order to clarify the mechanism of casing deformation in shale oil wells, comprehensive analysis was conducted on engineering factors, multi-arm caliper logging, seismic attributes, and the distribution characteristics of casing deformations. This study shows that casing strength, cementing quality, and wellbore curvature are not the main controlling factors for casing deformation. Casing deformation is caused by the communication between hydraulic fractures and natural fractures during the fracturing process, which increases the fluid pressure in the natural fracture and induces shear slip, resulting in casing deformation due to shear stress. Based on the understanding of the mechanism of casing deformation in shale oil wells, two targeted casing deformation prevention and control methods are proposed. First, temporary plugging was implemented during the hydraulic fracturing process when the fluid volume reached 1000 m3, and the pumping rate was reduced to below 16 m3/min to reduce the internal fluid pressure of the fractures and control fracture slip, thereby minimizing the risk of casing deformation. Second, hollow particles were added to the cement to enhance the consolidation effect of the cement sheath and mitigate casing deformation caused by fracture slip. Research indicates that a hollow particle content of 15% can meet the requirements for casing deformation control in Gulong shale oil. These research results can provide important references for the prediction and prevention of casing deformation risks in shale oil and similar unconventional reservoirs during hydraulic fracturing.

Data-driven modelling with coarse-grid network models

We propose to use a conventional simulator, formulated on the topology of a coarse volumetric 3D grid, as a data-driven network model that seeks to reproduce observed and predict future well responses. The conceptual difference from standard history matching is that the tunable network parameters are calibrated freely without regard to the physical interpretation of their calibrated values. The simplest version uses a minimal rectilinear mesh covering the assumed map outline and base/top surface of the reservoir. The resulting CGNet models fit immediately in any standard simulator and are very fast to evaluate because of the low cell count. We show that surprisingly accurate network models can be developed using grids with a few tens or hundreds of cells. Compared with similar interwell network models (e.g., Ren et al., 2019, 10.2118/193855-MS), a typical CGNet model has fewer computational cells but a richer connection graph and more tunable parameters. In our experience, CGNet models therefore calibrate better and are simpler to set up to reflect known fluid contacts, etc. For cases with poor vertical connection or internal fluid contacts, it is advantageous if the model has several horizontal layers in the network topology. We also show that starting with a good ballpark estimate of the reservoir volume is a precursor to a good calibration.

Ultrasonic Experimental Evaluation of the Numerical Model of the Internal Fluid Flow in the Kidney Cooling Jacket

Ultrasonic Experimental Evaluation of the Numerical Model of the Internal Fluid Flow in the Kidney Cooling Jacket

Experimental investigation of induced vibrations in horizontal Gas-Liquid flow

One of the governing contributors to offshore structures' (e.g., pipelines and deep-water risers) accumulative long-term fatigue damage is the internal flow-induced vibrations caused by slug flow. Due to the complexity of the numerical modeling of the internal flow and fluid–structure interaction, experimental campaigns are often performed to predict the asset response and provide a benchmark for numerical model validation. In this study, an experimental campaign was conducted which included a unique computer vision data acquisition system and a large-scale facility designed to mimic industry field conditions. This study aims to relate flow parameters to structural response and explain the mechanisms that govern the relationship between both domains.The presented results reveal that the gravitational forces of the fluid dominate the transverse deflections of the pipe and, therefore, the slug liquid holdup, film liquid holdup, and slug length showed strong correlations to pipe deflections. However, centrifugal forces were observed to have significant contributions to pipe deflection for high translational velocity slugs. Additionally, it was found that for most of the test conditions, the primary pipe excitation frequency correlates to the slug frequency. It was discovered that no-slip liquid holdup has a positive correlation to both the magnitude and range of pipe deflection and that increases in superficial gas and liquid velocities led to decreases and increases in pipe deflection, respectively. Furthermore, it was observed that the measured frequency responses of the structure tended to increase with increasing gas velocity until the flow pattern in the pipe began to transition to annular flow.

The use of MCDM techniques to assess fluid pressure on the bending quality of AA6063 heat-treated tubes

This paper investigates the bending of aluminum tubes under different fluid pressure and heat treatment conditions. The application of multi-criteria decision-making (MCDM) methods was evaluated for selecting the best forming condition considering cross-section ovality, thinning, and thickening of the bent tubes. Analytic hierarchy process (AHP) was used for criteria weighting, and technique for order of preference by similarity to ideal solution (TOPSIS) and multi-objective optimization on the basis of ratio analysis (MOORA) were used for alternative ranking. A combination of various types of AA6063 tubes, including as-received (R), annealed (O), and artificial aged (T6), with different fluid pressures (0, 1, 1.8, 3.2, and 3.6 MPa) were assumed to be as the alternatives (forming conditions). The results demonstrate that the ovality and thickening of the bent tubes decrease by increasing the internal fluid pressure. On the other hand, increasing the internal fluid pressure gives rise to an increase in thinning of bent tubes. The O sample has the lowest ovality and thickening while the T6 sample has the lowest thinning. MCDM analysis revealed that the O samples at higher pressures show better bendability.

Giant sacral schwannoma in a neurofibromatosis type 2 patient

BackgroundNeurofibromatosis type 2 is an autosomal dominant disorder, mainly characterized by multiple neurological lesions, such as schwannomas, meningiomas, neurofibromas and intramedullary ependymomas. Schwannomas are usually small circumscribed lesion. Sacral location of a schwannoma with cystic change is a very rare finding. We are presenting one such case with giant cystic schwannoma with fluid–fluid levels in sacral region.Case presentationWe present a case of 13-year-old female patient, presenting with pelvic pain and gradually progressive bilateral lower limb weakness. On MRI, giant cystic schwannoma with internal fluid–fluid levels was noted in sacral region, extending anteriorly into the presacral region, causing mass effects on pelvic organs, which explained the cause of her symptoms. She also showed the presence of bilateral vestibular schwannoma and multiple small cerebral lesions, leading to the diagnosis of neurofibromatosis type 2.ConclusionsOur current case of neurofibromatosis type 2, diagnosed by presence of bilateral vestibular schwannoma, shows atypically large sacral cystic schwannomas and cerebral subcortical lesions, probably representing glial microhamartomas. Sacral schwannomas can be of giant size with cystic changes and fluid–fluid levels, mimicking aneurismal bone cyst, as in current case.

A Methodology to Assess the Sloshing Effect of Fluid Storage Tanks on the Global Response of FLNG Vessels

The sloshing effect of fluid storage tanks of a Floating Liquefied Natural Gas (FLNG) vessel causes variations in its global motion response. These acceleration and motion alterations can affect the safe performance of the FLNG vessels. The classification societies’ rules are employed to standardize the storage tanks’ configuration of FLNG vessels. Herein, we report a methodology to assess the sloshing effect on the global motion response of an FLNG vessel considering four geometrical arrangements of tanks and different fluid filling fractions. This methodology includes the hydrodynamic effect in operating and storm conditions from the Gulf of Mexico using a return period of 100 years. In addition, our methodology considers the influence of the internal fluid of each tank to estimate the accelerations and motions of the vessel. This methodology can be implemented to estimate the stability of an FLNG vessel under different environmental conditions. Thereby, the naval engineers could choose the best geometrical configuration of the storage tanks for safe behavior of a vessel under different operating and extreme environmental conditions.