Fluid Wall Research Articles

Growing skull fracture of the orbital roof: case report and literature review

Growing skull fracture (GSF) of the orbital roof is a rare complication of head injury in infancy and early childhood. Analysis of the Medline database between 1983 and 2023 identified 17 articles describing 63 children after surgical treatment of GSF of the orbital roof. We present a 2-year-old child with moderate traumatic brain injury (TBI) complicated by GSF of the orbital roof. Neuroimaging and literature data are described. Severe ophthalmological symptoms in acute period of TBI subsequently partially regressed with persistent swelling of the upper eyelid and hypophthalmos. CT and MRI revealed a linear fracture of the frontal bone extending to superior orbital wall and intraorbital collection of cerebrospinal fluid (pseudomeningocele) mixed with blood. MR signs of GSF of the orbital roof with pseudomeningocele shrinkage were found in 5 weeks after injury. After 6 months, CT and MRI revealed signs of more severe GSF. Surgical treatment implied craniotomy, excision of scars, arachnoid membrane and abnormal brain matter, resection of deformed fracture edges, dura mater sealing and orbital roof reconstruction with bone autograft. Ophthalmological symptoms regressed after 6 months. The follow-up period was 6 years. There were no signs of fracture recurrence. In this case, acute intraorbital pseudomeningocele led to GSF of the orbital roof in 5 weeks after injury. Incomplete regression of ophthalmological symptoms, their aggravation or delayed appearance in children with orbital roof fracture requires a thorough examination including high-resolution CT and MRI, and orbital roof GSF should be considered in the differential diagnosis.

Experimental validation of a heat exchanger model for thermoacoustic applications

Thermoacoustics is a promising technology for energy conversion purposes. Among the bottlenecks limiting a large diffusion of thermoacoustic devices, there are heat exchangers, whose behaviour in oscillatory flows is rather different than those working in stationary flows. Furthermore, the classical linear acoustic theory in the frequency domain cannot predict with high-fidelity the thermo-fluid dynamics of such heat exchangers. In this article, a CFD model based on a standing wave device including a parallel plate heat exchanger is proposed. The setup is inspired by a similar prototype of a thermoacoustic engine in which the performance of the ambient heat exchanger was tested. The results of the CFD model are therefore compared, in terms of the temperature difference between fluid and solid wall in the heat exchanger, average heat flux and Nusselt number, with experimental data showing a satisfying agreement.

On predictive models for the equivalent sand grain roughness for wall-bounded turbulent flows

One of the long-standing goals of rough wall fluid dynamics research is to determine the drag penalty of surfaces based solely on their topographical parameters. The most important length scale or roughness parameter that best describes a surface in relation to friction drag has not been agreed upon yet, despite the many studies that, over the years, have attempted to identify the most appropriate surface parameter. The concept of an equivalent sand-grain roughness (ks) was introduced to standardize different types of roughness in wall-bounded turbulence, serving as an input parameter for predicting the roughness function ΔU+. To anticipate ΔU+ generated by a rough surface under turbulent flow conditions, experts use roughness correlations that establish a correspondence between the topographical characteristics of the surface and ks. Therefore, a chronological compilation of roughness correlations is presented, detailing the parameter ranges and types of roughness used in their development. This study evaluates the effectiveness of predictive correlation functions and aims to formulate a universal function by exploring a comprehensive assortment of three-dimensional (3D) surface textures available in the literature. The results suggest that a correlation based on surface height skewness (ksk) and streamwise effective slope (ESx) can predict the ratio (ks/kq), where kq is the root mean square roughness height for 3D roughness in the fully rough regime. Despite the fact that the correlation is restricted to 3D surface roughness, which is a more realistic representation, the model demonstrated a high level of accuracy in predicting ks for over 120 distinct rough surfaces.

Aqueous Humor Circulation in the Era of Minimally Invasive Surgery for Glaucoma.

Glaucoma surgery with implantation of aqueous humor draining microstents may compromise long-term corneal health by disrupting aqueous humor circulation. The effect of stent numbers on this circulation was interrogated to determine the number of stents associated with minimal circulation disruption. An in vitro anterior eye model perfusion system was constructed with multiple exit ports. A 3-D model of the anterior eye was imported into ABAQUS CFD, analyzes were carried out for unsteady laminar flow and solved using Navier-Stokes equations. DT Vision Foundry was used to analyze velocity contour plot images. The field variable results output for the CFD model were fluid wall shear, fluid pressure and fluid velocity. In vitro, "aqueous" fluid flow is high through a single stent and "aqueous" stagnation is greatest in the quadrants 180° away. Increasing stent port numbers, results in an exponential decrease in the stagnant flow locations. High wall shear stress was seen in the single stent model and is markedly reduced after a second and subsequent stents are introduced. We identify two factors potentially contributing to corneal compromise post glaucoma drainage surgery: aqueous humor stagnation, remote to the stent site and higher exit flows imparting increased stent exit shear stress (particularly with a single stent). With 4 stents, there is minimal disruption of anterior chamber circulation (mimicking physiological conditions). Furthermore we propose that aqueous humor circulation disruption via the usual single-exit port approach disrupts aqueous humor circulation with long-term consequences for corneal health.

An NEA/OECD benchmark-experiment for the validation of CFD for mixing and thermal fatigue in T-junction dead leg flows

The current screening criteria for thermal fatigue used in isolated branch lines at nuclear power plants are based on simplified approaches, which, on one hand, tend to be overly conservative, and on the other hand, appear to miss important physics. This is demonstrated by the fact that a number of affected pipes were missed by the current screening methods.The purpose of the present work is to produce novel and accurate experimental data, which can be used for a benchmark of Computational Fluid Dynamics (CFD) in order to advance the prediction capabilities of thermal mixing and fatigue in dead leg T-junctions and improve the accuracy of the screening criteria. The ultimate value creation is increased safety and availability at nuclear power plants. This is of great interest and utmost importance to the nuclear reactor safety community.A new pressurized experimental setup of a T-junction has been designed and constructed for the purpose. The experimental setup, with a temperature difference of 120 °C, more closely resembles plant conditions than in earlier experiments. The boundary conditions in terms of the flowrates and temperatures are controlled and stable within their measurement uncertainty – a prerequisite for CFD-grade experiments.The novelty of the present work is measurements of the temperature fluctuations both in the near wall fluid mixing region and throughout the solid pipe wall material.It has been shown that the interaction between the swirl penetration of hot water and the stratified layer in the cold dead leg has an intermittent character and that random clusters of bursts of hot water penetrate into the stratification and the stagnant cold water below. The average time scale of this process is of the order of hundreds of seconds.The stratification between the hot and the cold water in the dead leg has also shown to have a low frequency oscillation of the order of 0.1 Hz, which wiggles in the circumferential direction. After hot water has penetrated downward and excited the instability, the temperature falls back to the initial one in a manner similar to a damped oscillation.The vertical temperature profiles have shown to be self-similar, for moderate temperatures, when scaled with the temperature difference between the hot and the cold water and with the penetration length.The penetration length increases with the velocity in the hot leg confirming earlier reported correlations.A small (less than 0.1 % of the hot main flow) cold leakage flow into the T-junction is sufficient to suppress the swirl penetration and substantially reduces the penetration length. However, the temperature fluctuations have a larger amplitude and range across the whole mixing zone. The fluid temperature fluctuations are shifted towards a more high frequency content, however, the low frequency nature of the swirl penetration is still present.The obtained novel dataset will be provided for a blind CFD benchmark exercise as part of an OECD/NEA project in 2023 and 2024.

Experimental investigation of laminar and turbulent displacement of residual oil film

Residual oil films on pipe walls are a common occurrence in industrial processes, and their presence can significantly impact system efficiency and performance. However, the mechanisms that govern oil film removal by an immiscible displacing fluid from the internal walls of pipes under different flow regimes, including laminar and turbulent flows, are not yet fully understood. In this study, we investigated the impact of displacing fluid flow regime, injected volume, displacement time, and wall shear stress on the efficiency of residual oil film removal in a pipe. We first verified the applicability of our developed oil film measurement method for the use in vertical pipes, and found that gravity did not significantly affect the long-term oil film removal process. We verified that our results from the laminar cases agree with the theoretical thin-film limit scaling under reasonable assumptions of constant shear stress and negligible surface tension. We then examined the displacement efficiency of residual oil film under laminar and turbulent flow regimes. Our experimental results revealed that the onset of turbulence of displacing fluid played an important role in the efficient removal of residual oil film, with an optimal range of Reynolds numbers (7000–8000) when the injected volume of displacing fluid is limited. Furthermore, we explored the combined effect of wall shear stress and displacement time on the displacement process under different turbulent flow regimes. We found that the intermediate turbulent regime was the most efficient for achieving cleaning in a limited time, while the highly turbulent regime proved to be the most effective for achieving complete cleaning over a longer time period. These findings have important implications for oil recovery and pipeline maintenance and provide valuable insights into optimizing the removal of residual oil film in pipes.

Deformable Biomechanics of DMEK Tissue Scrolls Traveling Through Narrow Lumens: The Inverse Relationships Between Fluid Velocity, Scroll Width, and Wall Contact and Their Clinical Implications for Preloading.

The aim of this study was to evaluate Descemet membrane endothelial keratoplasty (DMEK) scroll width and length in relation to variable velocities as the tissue transits through wide and narrow lumen glass tubes. Sets of DMEK tissue were processed using the Iowa Lions Eye Bank standard DMEK protocol and were passed through 2 glass tube widths at variable speeds. Two hourglass-shaped glass tubes were created, one "wide" and one "narrow." A syringe pump, valve, and pressure gauge were used to modulate tissue speed through each tube. For both tube sizes, DMEK tissue was passed through their lumens with incrementally increasing velocity and visualized with a high-speed camera at frame rates from 1000 to 8000 fps. Scroll width and length were measured using IDT Motion Studio software and digital calipers. There was a significant, indirect correlation between scroll velocity and width in both the wide (R 2 = -0.98, P < 0.001) and narrow (R 2 = -0.84, P < 0.001) tubes. There was a significant, direct correlation between scroll velocity and length in both the wide (R 2 = 0.84, P < 0.001) and narrow (R 2 = 0.83, P < 0.001) tubes. The resting widths of the scrolls were 105% and 207% wider than the wide and narrow tubes, respectively. All transits recorded scroll widths that were equal to or smaller than their respective tube's internal diameter. There is a significant, inverse correlation between DMEK scroll velocity and width as well as a direct correlation between scroll velocity and length, allowing DMEK scrolls to transit through a tube that is narrower than its resting width without sustained lumen wall contact.

Ultrasonographic Findings of Catheter-Related Bloodstream Infection in Pediatric Patients.

Catheter removal is essential for treating catheter-related bloodstream infection (CRBSI); however, clinicians are sometimes hesitant to remove catheters in pediatric patients due to the difficulty of securing vascular access. Confirming the diagnosis of CRBSI is important to justify catheter removal. The purpose of this study was to describe the sonographic findings of CRBSI. We included patients with a central venous catheter (CVC) or peripherally inserted central catheter (PICC) who had a positive blood culture and underwent ultrasound. The patients were classified as with or without CRBSI. Sonographic findings, such as the presence/absence of thrombus, venous wall thickening, hyperechogenicity, and fluid collection around the vein were compared using Fisher's exact test. Of the 58 patients, 38 (66%) were diagnosed with CRBSI. The presence of thrombus (19/38 vs 3/20, P = .011); and hyperechogenicity around the vein (14/38 vs 2/20, P = .035) differed significantly, but There was no significant difference in the presence of venous wall thickening (10/38 vs 1/20, P = .077), and fluid collection around the vein (5/38 vs 0/20, P = .153), did not differ significantly in patients with and without CRBSI, respectively. One-third of patients with CRBSI, including 11 (42.3%) patients with CVC, and 2 (16.7%) patients with PICC, did not have abnormal sonographic findings. Ultrasound findings are useful for diagnosing CRBSI. However, the sensitivity of sonographic findings is low and abnormal sonographic findings are sometimes absent in children with CRBSI; therefore, physicians should not rule out CRBSI based on normal sonographic findings, especially in patients a CVC and a positive blood culture.

FRI230 Cystic Pheochromocytoma

Abstract Disclosure: S. Saberi: None. A 67-year-old woman presented with right abdominal tenderness, abdominal distention, gas and belching. Her blood pressure was 134/70, pulse 84 with no palpable abdominal mass. Her medical history includes depression and anxiety which developed 17 years prior and later resolved. She was diagnosed with hypertension approximately 20 years earlier initially well-controlled with candesartan-hydrochlorothiazide 16-12.5 mg daily and metoprolol succinate ER 50 mg daily. Two years prior to presentation her blood pressure rose to the 180s/90s requiring doubling of her candesartan-hydrocholorothiazide. An abdominal ultrasound was obtained which showed an abdominal mass. Subsequently, a CT of the abdomen and MRI of the abdomen with and without contrast were obtained revealing a 10 cm predominantly cystic adrenal mass with partial irregular wall thickening and nodularity causing mass effect on the inferior vena cava, liver and right kidney. Results of lab testing revealed an elevated plasma free metanephrines 1187 pg/ml (normal &amp;lt; 57 pg/ml), plasma free normetanephrines 1911 pg/ml (normal &amp;lt; 148 pg/ml), total free metanephrines and normetanephrines 3098 pg/ml (normal &amp;lt; 205 pg/ml). Her other adrenal biochemical evaluation was normal. She underwent open right adrenalectomy after adequate pre-operative blockade. Post-operatively her plasma free normetanephrines decreased to 0.47 nmol/L (normal &amp;lt; 0.90 nmol/L) and plasma free metanephrines were less than 0.20 nmol/L (normal &amp;lt; 0.50 nmol/L). Cystic Pheochromoctyoma: Spontaneous rupture of cystic pheochromocytoma can cause an adrenergic crisis. Cystic pheochromocytoma may develop due to hemorrhage within the lesion, necrosis and subsequent cyst formation (1). Patients may present with abdominal pain, GI symptoms or palpable masses rather than classic symptoms of pheochromocytoma (2).The differential diagnosis of cystic adrenal lesions includes lymphangiomas, pseudocysts of other surrounding structures (such as liver, pancreas, kidney, spleen, retroperitoneal and urachal and mesenteric cysts), dermoids, adrenal carcinoma, hydatid cysts of the adrenal glands (3).Small case series report the incidence of adrenal cysts in adrenal disease as 5.1% (4). A female predominance has been reported in prior studies (4). More commonly cystic adrenal lesions are unilateral and present in persons aged 30s-50s (2). Adrenal cysts are classified based on their origin as endothelial cysts derived from malformation of the lymphatic or arteriovenous systems, pseudocysts derived from prior hemorrhage, epithelial cysts with thin wall and serous fluid, or parasitic cysts. Necrosis and liquefaction in the adrenal lesion may lead to fluid accumulation and a cystic appearance. Large cysts are at risk for hemorrhage and rupture. All adrenal cysts require biochemical evaluation. Particular attention should be paid to predominantly cystic masses with any solid component as up to 7% of these may be malignant (5). Uniform guidelines for surgical management of these lesions have not been well established. Patients with symptoms such as abdominal pain, biochemical abnormalities, complications such as pressure on adjacent organs or rupture with cyst content leakage, suspicion of malignancy, cysts larger than 5 cm or increasing size of the cyst should be considered for surgical intervention (5, 6). In patients presenting with abdominal pain and hypertension who are found to have a cystic adrenal lesion pheochromocytoma should be considered. Presentation: Friday, June 16, 2023

Next-generation sequencing of pancreatic cyst wall specimens obtained using micro-forceps for improving diagnostic accuracy.

Background and study aims Pancreatic cysts are common incidental findings, with an estimated prevalence of 13% to 15% in imaging done for other reasons. Diagnosis often relies on collection of cyst fluid, but tissue sampling using micro-forceps may allow for a more reliable diagnosis and higher yield of DNA for next-generation sequencing (NGS). The primary aim was to assess the performance of NGS in identifying mucinous cyst. The secondary aims were to assess DNA yield between the cyst fluid and cyst wall tissue, complication rate and performance of conventional investigations. Patients and methods Twenty-four patients referred for endoscopic ultrasound were recruited. Biopsies were taken using micro-forceps and the AmpliSeq Cancer Hotspot panel was used for NGS, a polymerase chain reaction assay targeting several hotspots within 50 genes, including GNAS , KRAS and VHL . Results The concentration of DNA extracted from 24 cyst wall samples was significantly higher than in the nine of 24 available matched cyst fluid samples. The sensitivity, specificity, and diagnostic accuracy of NGS for diagnosing mucinous cyst were 93%, 50% and 84%; for standard of care, they were -66.6%, 50% and 63.1%; and for standard of care with NGS, they were 100%, 50%, and 89.4% respectively. Cyst wall biopsy was able to diagnose 19 of 24 cysts (4 high risk, 7 intraductal papillary mucinous neoplasms, 4 cysts of mucinous origin, and 4 benign). Conclusions NGS data correlate well with histology and may aid in diagnosis and risk stratification of pancreatic cysts. Cyst wall biopsy performs well in diagnosing cysts but was inadequate in five of 24 patients.

Effects of viscoelastic fluid on noise reduction of the flow over a circular cylinder

Viscoelastic fluid can suppress instabilities of vortices around a circular cylinder, and has a wide application prospect in flow noise reduction. The effects of elasticity and the maximum polymer extensibility of dilute polymer solution on the noise reduction of flow around a circular cylinder were investigated. FENE−P model was used to simulate flow noise of two-dimensional flow through two different sound source extraction methods with Reynolds number of 100, Weissenberg number of 0 to 40, and the maximum polymer extensibility of 10 to 100. Results show that viscoelastic fluid can inhibit the formation of vortices, reduce the fluid pulsation around cylinder, and reduce intensity of dipole sound source on cylindrical surface. With appropriate maximum polymer extensibility, flow noise is particularly reduced, and elasticity will enhance the noise reduction effect. On condition that the Weissenberg number remains unchanged, a moderate increase in the maximum polymer extensibility can further reduce dipole intensity as well as drag of cylindrical surface, and flow noise will be further reduced. However, if the maximum extensibility of the polymer is too high, solid-like behavior will occur around the cylinder, greatly increasing drag and elastic stress and creating a new dipole around the fluid wall. Finally, noise increases. This study analyses the influence of various parameters in a viscoelastic fluid on noise and provides an idea with promising applications for flow noise reduction.

A coupled level-set and volume-of-fluid (CLSVOF) method for prediction of microgravity flow boiling with low inlet subcooling on the international space station

The present study is part of a series of NASA-supported investigations of flow boiling of n-perfluorohexane (n-PFH, C6F14) under microgravity on the International Space Station (ISS). The fluid physics and heat transfer characteristics of flow boiling with low inlet subcooling are explored using the Flow Boiling and Condensation Experiment (FBCE) (which is actual name of the test facility), the largest endeavor in microgravity two-phase research conducted to date. Experimental data are collected from the FBCE's Flow Boiling Module (FBM), which features a rectangular channel with 5.0-mm x 2.5-mm cross-section and 114.6-mm heated length. Results for three flow rates are used to explore the effects of mass velocity on flow structure and heat transfer characteristics in the absence of the body force. A Computational Fluid Dynamics (CFD) model is constructed to predict the measured FBM results. The CFD model employs the Coupled Level-Set and Volume-of-Fluid (CLSVOF) method, which is modified with improved interface capture and additional force terms in the momentum equation to determine the bubble dynamics more accurately. Validity of the CFD model is assessed in two ways, by comparing predictions against video-captured interfacial behavior and heat transfer data. The CFD model shows good ability to capture detailed evolution of the interfacial structure both across and along the flow channel, including bubble nucleation, growth, departure, and coalescence, as well as axial development of dominant flow patterns. Details of the flow structure are examined via axial development of both flow velocity and void fraction profiles. Similarly, heat transfer results are presented in terms of streamwise variations of both wall temperature and fluid temperature, which are also predicted accurately with the CFD model. Overall, this study proves the CFD model is an effective method for both design and performance assessment of flow boiling subsystems in space vehicles.

Analysis of transient characteristics of droplets in the DFFB regime during single-rod channel reflood experiment

This study aims to explore the dynamic distribution and hydrodynamic characteristics of droplets during the highly transient process of reflood. However, the quasi-steady state analysis is generally adopted in existing studies reported in the literature, ignoring the dependence of droplet formation and breaking mechanism in the Dispersed flow film boiling (DFFB) mechanism on the time-related historical behaviors such as the propagation of the quench front. A series of reflood cooling visualization experiments of zirconium alloy high-temperature rod-shaped heating surface were carried out to achieve this research goal. The wall surface and fluid temperature history curves were recorded, and the parameters, such as the size and velocity of DFFB regime droplets, were quantitatively extracted by visual image processing technology. Based on the formation and breakup mechanism of droplets in the dispersed flow, the reasons for droplet size distribution and velocity change with input heat flux, initial wall temperature, inlet subcooling, and inlet flow rate are well analyzed and explained. At the same time, the experimental results also show a strong correlation between droplet behavior and the reflood process in time. This study can provide more detailed physical support for the subsequent development of droplet behavior models more suitable for the strong transient reflood process and the evaluation of existing models.

Flows in fluid-walled conduits driven by Laplace pressure

In conventional microfluidic devices, fluids are often confined behind solid plastic walls that restrict access and trap gas bubbles; in open microfluidics some solid walls are replaced by fluid ones (i.e. interfaces with immiscible fluids). In both cases, flows are usually driven by external pumps or gravity. An innovative open technology has been developed in which two-dimensional patterns of cell-culture medium in standard Petri dishes are confined by fluid walls made of an immiscible and bio-inert fluorocarbon (FC40). To provide refreshing media flows to cells in such circuits, an established pumping system that exploits differences in Laplace pressure across open interfaces has been applied to drive flow without using external pumps: a source drop autonomously empties through a straight conduit into the rest of the dish (the sink). Whereas conduits with solid walls have unchanging boundaries and flows within them are well understood, the challenge is to predict flows in circuits where fluid walls morph as pressures change. Numerical and semi-analytical equations enabling the prediction of changing flows are developed, and predictions validated experimentally.

Computational fluid dynamics-based prediction of aortic aneurysm rupture in a patient with chronic aortic dissection

BackgroundThe indication of additional aortic arch surgery for residual aortic dissection remains controversial as some patients experience aneurysm rupture at a smaller diameter of 55 mm.MethodAn 84-year-old woman, who underwent total arch replacement for chronic dissection, developed rupture of a residual aneurysm of with a diameter of 48 mm. Computational fluid dynamics simulated pressure and wall shear stress comparing pre- and post-total arch replacement.ResultsAfter total arch replacement, false lumen pressure in the distal aortic arch increased (pre, 138.5 mmHg; post, 148.2 mmHg). Wall shear stress also increased in the distal aortic arch (pre, 10.5 Pa; post, 16.9 Pa).ConclusionComputational fluid dynamics could retrospectively predict a significant postoperative increase in false lumen pressure and wall shear stress of chronic dissections after total arch replacement, potentially leading to aneurysm rupture.

Enhancing latent heat storage systems: The impact of PCM volumetric ratios on energy storage rates with auxiliary fluid assistance

The present study investigates the effect of different volume ratios of PCM on the melting process and energy storage in the improved thermal energy storage (TES) system using auxiliary fluid. The purpose of using the auxiliary fluid is to benefit from the density difference between the auxiliary fluid and the PCM, which improves the convection heat transfer in the auxiliary fluid and increases the melting speed of the PCM. The auxiliary fluid, which has a higher density, is placed on the solid PCM at the beginning of the melting process and takes the place of the melted PCM during the melting process. This displacement causes better heat transfer between auxiliary fluid, PCM, and hot wall. Five different PCM/auxiliary fluid volume ratios are studied, including 30, 40, 50, 60, and 70% of PCM. The rate of energy storage in the system increases to 0.341 kW/kg, the highest rate of energy stored in the system and in PCM, corresponding to a volume ratio of 30% of PCM. Although the total energy stored in the system increases with an increase in the PCM volume ratio, the energy storage rate in the system increases with a decrease in the PCM volume ratio. Therefore, the optimal use of the most appropriate volume ratio of PCM is of great importance.

A new wormhole mechanistic model for radial acid flow geometry using novel 3D flow correlations

In carbonate reservoirs, matrix acidizing is used to improve well performance by creating conductive channels called wormholes. Predicting wormhole propagation rate in radial acid flow geometry up to the real wellbore scale is the main problem regarding designing field operations in previous studies which are still challenging. In this study, a new mechanistic approach is presented to predict the radial flow acidizing up to near wellbore scale by considering the vital effects of porous media size and geometrical parameters of wormhole patterns.Accordingly, wormhole tip velocity and wormhole wall fluid loss rate will be introduced as the scale transferring parameters between different porous media sizes which are correlated in terms of rock diameter and wellbore height, wormhole size and density. These novel correlations are extracted from the large databank of flux distribution between rock matrix and wormhole channel obtained in 60 different 3D FEM flow simulations for various patterns of wormhole propagating and different wellbore sizes. In addition, an HPHT radial acid flooding setup is designed and constructed to perform radial acid coreflood on ultra-low permeable rocks (k«1md) for model validation. During the experiments, the breakthrough pore volume, pressure behavior and CT scan of samples are closely monitored. The results showed that due to the tight window of pore size distribution, faster breakthroughs with 1.23 and 1.45 pore volumes occurred in these tight samples compared to those reported already which are confirmed by developed model prediction. Besides, the model results showed that increasing the rock height (open-hole interval) would increase wormhole tip velocity and decrease acid breakthrough time. In addition, the higher temperature shifted the acid response curve to the right, toward higher acid breakthrough volume and higher acid concentration shifted it toward lower breakthrough volumes. The model is validated using radial acid experiments and previous radial acid models for different rock sizes with good agreement (R2 = 0.9547, MSE = 0.02161 and RMSE = 0.14701). The new radial acidizing model is capable to quickly predict wormhole propagation rate up to wellbore scale without requiring excess up-scaling data due to considering wide ranges of porous rock sizes from (25.4–152.4 cm) diameter and (5–25.4 cm) pay zone height (sufficient size for considering repetitive wormhole patterns). This technique can be utilized for tuning parameters of various radial cases to predict the acid tests results leading to reduce the number of required experiments.

A Review on the Modelling Techniques of Liquid Storage Tanks Considering Fluid–Structure–Soil Interaction Effects with a Focus on the Mitigation of Seismic Effects through Base Isolation Techniques

Globally, tanks play a major part in the provision of access to clean drinking water to the human population. Beyond aiding in the supply of fresh water, tanks are also essential for ensuring good sanitary conditions for people and for livestock. Many countries have realized that a robust water supply and a robust sanitation infrastructure are necessary for sustainable growth. Therefore, there is large demand for the construction of storage tanks. Further, liquid storage tanks are crucial structures which must continue to be operational even after a catastrophic natural event, such as an earthquake, to support rehabilitation efforts. From an engineering point of view, the various forces acting on the tanks and the behaviour of the tanks under various loads are important issues which need to be addressed for a safe design. Analyses of the tanks are challenging due to the interaction between the fluid and tank wall. Thus, researchers have conducted several investigations to understand the performance of storage tanks subjected to earthquakes by considering this interaction. This paper discusses the historical development of various modelling techniques of storage tanks. The interaction with the soil also influences the behaviour of the tanks, and hence, in this paper, various modelling approaches for soil structure interaction are also reviewed. Further, a brief history of various systems of base isolation and modelling approaches of base-isolated structures are also discussed in this article.

Inertial migration of a neutrally buoyant finite sized sphere in a pipe with streamwise periodic corrugations

A finite sized neutrally buoyant object migrates radially under the action of inertial lift in a smooth circular pipe due to the hydrodynamic coupling between the object and the surrounding fluid. Decorating the pipe walls with periodic corrugations alters the deformation of the fluid locally, thereby modifies the object’s migration pattern. This study investigates inertial migration of a finite sized neutrally buoyant sphere in a pipe with streamwise periodic corrugations of a size comparable to the sphere diameter. Fully resolved simulations are performed using smoothed particle hydrodynamics (SPH) to investigate the effect of Reynolds number, streamwise arrangement of corrugations as well as the corrugation topology on the inertial coupling of fluid and solid domains and long-time dynamics of suspended particles. The results show that periodicity in corrugation arrangement causes near wall fluid to deform periodically, this is reflected on the migrating sphere as oscillating linear and radial accelerations. These oscillations result in the object to spin around an axis perpendicular to its primary rotation axis. This secondary rotation permits the object to escape locally active flow regions and results in it to follow an oscillatory path. The rate and strength of such oscillations, thus its migratory behavior can be orchestrated by controlling the corrugation arrangement and/or topology.

Demand-driven active droplet generation and sorting based on positive pressure-controlled fluid wall.

Droplet microfluidics is a rapidly advancing area of microfluidic technology, which offers numerous advantages for cell analysis, such as isolation and accumulation of signals, by confining cells within droplets. However, controlling cell numbers in droplets is challenging due to the uncertainty of random encapsulation which result in many empty droplets. Therefore, more precise control techniques are needed to achieve efficient encapsulation of cells within droplets. Here, an innovative microfluidic droplet manipulation platform had been developed, which employed positive pressure as a stable and controllable driving force for manipulating fluid within chips. The air cylinder, electro-pneumatics proportional valve, and the microfluidic chip were connected through a capillary, which enabled the formation of a fluid wall by creating a difference in hydrodynamic resistance between two fluid streams at the channel junction. Lowering the pressure of the driving oil phase eliminates hydrodynamic resistance and breaks the fluid wall. Regulating the duration of the fluid wall breakage controls the volume of the introduced fluid. Several important droplet microfluidic manipulations were demonstrated on this microfluidic platform, such as sorting of cells/droplets, sorting of droplets co-encapsulated cells and hydrogels, and active generation of droplets encapsulated with cells in a responsive manner. The simple, on-demand microfluidic platform was featured with high stability, good controllability, and compatibility with other droplet microfluidic technologies.