Heavy Fluid Research Articles

Rayleigh–Taylor instability under multi-mode perturbation: Discrete Boltzmann modeling with tracers

The two-dimensional Rayleigh–Taylor Instability (RTI) under multi-mode perturbation in compressible flow is probed via the Discrete Boltzmann Modeling (DBM) with tracers. The distribution of tracers provides clear boundaries between light and heavy fluids in the position space. Besides, the position-velocity phase space offers a new perspective for understanding the flow behavior of RTI with intuitive geometrical correspondence. The effects of viscosity, acceleration, compressibility, and Atwood number on the mixing of material and momentum and the mean non-equilibrium strength at the interfaces are investigated separately based on both the mixedness defined by the tracers and the non-equilibrium strength defined by the DBM. The mixedness increases with viscosity during early stage but decreases with viscosity at the later stage. Acceleration, compressibility, and Atwood number show enhancement effects on mixing based on different mechanisms. After the system relaxes from the initial state, the mean non-equilibrium strength at the interfaces presents an initially increasing and then declining trend, which is jointly determined by the interface length and the macroscopic physical quantity gradient. We conclude that the four factors investigated all significantly affect early evolution behavior of an RTI system, such as the competition between interface length and macroscopic physical quantity gradient. The results contribute to the understanding of the multi-mode RTI evolutionary mechanism and the accompanied kinetic effects.

Experimental and theoretical studies on heavy fluid layers with reshock

The Richtmyer–Meshkov instability of a heavy fluid layer with reshock is investigated experimentally and theoretically, to reveal the mechanisms of the interfacial instabilities and motions of waves and interfaces under reshock conditions. Three kinds of heavy fluid layers with different thicknesses in unperturbed and perturbed cases are considered, highlighting the effects of initial layer thickness on the interface evolution. A general one-dimensional theory for describing the interaction between unperturbed interfaces and waves under reshock conditions is constructed, which supports the instability analysis and theoretical modeling in the perturbed cases. The perturbed fluid-layer results indicate that as the fluid-layer thickness decreases, the inhibition of squeezing effects on perturbation growth is gradually stronger than the promotion of rarefaction-wave effects on perturbation growth. The whole mixing width of fluid layers after reshock acceleration exhibits an approximately linear growth feature, and the reshocked mixing width growth rate is weakly dependent on the initial layer thickness, which is different from the finding before reshock. The linear amplitude growth of the right interface after reshock is promoted by the interface coupling effects but is still smaller than the prediction of the empirical linear model. When the squeezing effects are weak, the nonlinear model, which considers the modification of rarefaction-wave effects, can well predict the perturbation growth during and after the acceleration stage of rarefaction waves.

Lithium isotopic behaviour during high-temperature fluid-rock reactions of metapelites (>200 °C): A case study from the Baiyun orogenic gold deposit, Liaodong Peninsula, North China Craton

Mixing of low δ7Li sediment components (δ7Li(‰) = 1000 × [(7Li/6Li)sample/(7Li /6Li)L-SVEC − 1]) with high δ7Li altered oceanic crusts can explain the MORB-like Li isotopic signature of arc lavas. However, marine sediments with low δ7Li values have rarely been reported. The metasomatism of metasedimentary rocks in mélange zones may induce large Li isotopic fractionation; however, the Li isotopic behaviour of metasedimentary rocks during high-temperature fluid-rock reactions remains poorly understood. In this study, an integrated Li-O-Sr-Nd isotopic investigation was conducted on the Baiyun orogenic gold deposit, which represents a relatively simplified high-T hydrothermal system, to explore the Li isotopic behaviour during high-T metasomatism (>200 °C) of metapelites. The main host rocks in Baiyun are lithologically monotonous schists, with alterations including K-feldspathization, sericitization, and carbonation. The Nd isotopes identified host rock samples that could best represent the protolith of the altered schists in Baiyun. The Sr and O isotopic modelling yielded consistent water/rock ratios of 0.1–7.6 and 0.6–5.9, respectively, suggesting that relatively small volumes of fluids were infiltrated. There is no correlation among Li, Sr, and O isotopes; instead, a negative Li-K2O correlation and a positive δ7Li-K2O correlation of the altered schists are observed, suggesting that potassic metasomatism controlled Li concentrations and Li isotopes. The δ7Li values of altered schists in Baiyun can be classified into Group I, having lower Li concentrations (3.2–22.2 ppm) and δ7Li values (−3.8–0.4‰) than the protolith (31.6–47.9 ppm, 0.9–2.8‰), and Group II, having significantly lower Li concentrations (0.9–2.5 ppm) and overlapped or higher δ7Li values (1.0–4.5‰) than the protolith. Fluid leaching during high-T alteration removes Li and more 7Li than 6Li, which accounts for the lower Li concentrations and δ7Li values of Group I. When there is little Li remaining in rocks owing to progressive fluid leaching, the Li isotopes of the altered schists are equilibrated with heavy fluid Li (fluid buffering), which leads to higher δ7Li values observed in Group II. Based on a case study in Baiyun, this study proposes that similar high-T metasomatism of metasedimentary rocks in mélange zones could result in low δ7Li sediment inputs. Mixing of flux-modified isotopically light sediment inputs with isotopically heavy, altered oceanic crusts could account for the MORB-like Li isotopes of arc lavas.

A non-overlapping high accuracy parallel subdomain closure for compact scheme: Onset of Rayleigh-Taylor instability by ultrasonic waves

Rayleigh-Taylor instability (RTI) occurs at the interface of two media when the heavier fluid is accelerated into the lighter fluid and is a prototypical hydrodynamic event present in many physical events. In high energy physics, this manifests itself across a wide range of length scales from nuclear confinement fusion at micron-scale to supernova explosion at terra scales. RTI can also be viewed as a baroclinic instability prevalent in engineering, geophysics, and astrophysics, a pedagogic description of which is given in Sengupta et al. (2021) [12] with respect to the experimental results of Read (1984) [22]. Here, a recently proposed non-overlapping parallel algorithm is used to solve this three-dimensional canonical problem, having the unique property of not distinguishing between sequential and parallel computing, using 4.19 billion points and a refined time step of 7.69×10−8s. The problem achieves the required density gradient by considering two volumes of air at different temperatures (with a temperature difference of 200 K) separated by a non-conducting, impermeable partition at the onset of the experiment, which is removed impulsively at t=0. The resulting buoyancy force at the interface acting from top to bottom is the seed of the baroclinic instability. Present high precision computation enables one to capture the ensuing RTI triggered by ultrasonic waves created at the interface.

On the Rayleigh–Taylor instability for the two-phase Navier–Stokes equations in cylindrical domains

We are considering the two-phase Navier–Stokes equations with surface tension, modelling the dynamic behaviour of two immiscible and incompressible fluids in a cylindrical domain, which are separated by a sharp interface forming a contact angle with the fixed boundary. In the case that the heavy fluid is situated on top of the light fluid, one expects the effect which is known as Rayleigh–Taylor instability . Our main result implies the existence of a critical surface tension with the following property: In the case that the surface tension of the interface separating the two fluids is smaller than the critical surface tension, Rayleigh–Taylor instability occurs. On the contrary, if the surface tension of the interface is larger than the critical value, one has exponential stability of the flat interfaces. The last part of this article is concerned with the bifurcation of nontrivial equilibria in multiple eigenvalues. The invariance of the corresponding bifurcation equation with respect to rotations and reflections yields the existence of bifurcating subcritical equilibria.

Basalt Mo isotope evidence for crustal recycling in continental subduction zone

Highly variable molybdenum (Mo) isotope compositions are common in mafic arc magmas above oceanic subduction zones, but Mo isotopes of mafic magmas related to continental deep subduction have not yet been documented. Here, we report for the first time the Mo isotope composition of mafic igneous rocks above a typical continental subduction zone in east-central China, where the North China Block was subducted by the South China Block in the Triassic. Continental basalts of Early Cretaceous age show negative δ98Mo values of −0.98 to −0.16 ‰, significantly lower than the normal mantle value of −0.20 ± 0.01 ‰. These basalts also exhibit arc-like trace element compositions, high (87Sr/86Sr)i ratios of 0.7050 to 0.7058, negative εNd(t) values of −15.2 to −10.4, and negative εHf(t) values of −18.7 to −7.9. The light Mo isotope signatures are associated with enrichments in not only radiogenic Sr-Nd-Hf isotopes but also melt-mobile incompatible elements in the basalts. This indicates that the mantle source of these basalts would be generated by metasomatic reaction of the mantle wedge peridotite with felsic melts derived from partial melting of the deeply subducted continental crust. Given that continental crust usually exhibits heavy Mo isotope compositions, it would be dehydrated during its subduction to subarc depths. While the dehydration would have released isotopically heavy Mo fluids from the subducting crust, it leaves isotopically light Mo in the residual crust. The dehydrated continental crust underwent partial melting at subarc depths to produce felsic melts with low δ98Mo values, transferring the light Mo isotope signature into the mantle source of the basalts. Therefore, Mo isotopes in mafic igneous rocks are a powerful means to decipher the recycling of crustal components at convergent plate margins. Our study provides the first insight into Mo isotope recycling in continental subduction zones.

Tungsten isotopic fractionation at the Mariana arc and constraints on the redox conditions of subduction zone fluids

Fluid release from subducting slabs during recycling of oceanic lithosphere plays an important role in concentrating select elements near the Earth’s surface. Yet the extent to which these fluids are oxidising or reducing (fO2), one of the key characteristics that controls element mobility, remains poorly understood. Additionally, it is unclear whether the fO2 signature of arc fluids is generated deep within the slab during subduction or if it reflects later, shallower subarc crustal processes. Previous experimental work has shown that the extent to which highly incompatible W partitions into aqueous fluids depends on the temperature and fO2 conditions of the fluids. In the subducting slab, W partitions into rutile with a different coordination number to that which it exhibits in fluids, a process which may generate stable W isotopic fractionation. Therefore, if the competition between partitioning into aqueous fluids versus rutile is controlled by the conditions within the subducting slab, the elemental and stable W isotopic systematics of arc lavas may provide a novel tool with which to investigate subduction zones. We present isotopic compositions of a well characterised suite of arc lavas from the central island province of the Mariana arc (W. Pacific), and rutile separates from exhumed fragments of subducted, depleted, mafic oceanic crust from the Raspas Complex, Ecuador. Our data show that lavas from Guguan that exhibit the strongest geochemical signature of subduction zone fluids (e.g., high Ba/Th, Mo/Ce, Pb/Ce), contain the highest abundances of W compared to similarly magmatically incompatible Th, in agreement with anticipated fluid mobile behaviour. These Guguan lavas have distinct, heavy stable W isotopic compositions (δ186/184W = +0.134 to +0.156 ‰) compared to MORB (δ186/184W = +0.078 to +0.099 ‰) and those from sediments-dominated islands like Uracas and Agrigan (δ186/184W = +0.080 to +0.111 ‰). The W isotopic compositions of sediments off-board the Mariana arc are more variable, with the volcaniclastic sediments having δ186/184W values closest to those of the sediment dominated arc lavas. We show that rutile from representative subducting mafic crust incorporates isotopically light W, consistent with a coordination change from tetrahedral in fluids and melts to octahedral in the structure of rutile. We suggest that isotopically heavy fluids, complementary to the residual rutile in the mafic crust, account for the high δ186/184W of the fluid-dominated Guguan lavas, a process previously invoked to control Mo systematics in the same samples. Combining our new elemental and isotopic W data with these existing Mo data, we model the influence of oxygen fugacity on fluid compositions in equilibrium with the mafic crust, and the fraction of such fluids required to be added to the mantle wedge to reproduce the Mo-W systematics of erupted arc lavas. Our models show that more fluid is required (F = 6 %) than can be generated internally in the mafic oceanic crust, and that this fluid must be oxidised, perhaps as high as FMQ +5. We suggest that these requirements document the interaction of subducted mafic crust with an external source of oxidising fluids sourced from dehydration of underlying serpentinites.

Free Vibrations of Bernoulli-Euler Nanobeams with Point Mass Interacting with Heavy Fluid Using Nonlocal Elasticity.

Eigenfrequencies of a nanobeam with a point mass interacting with a heavy fluid are calculated using Bernoulli-Euler kinematics and consistent nonlocal elasticity model. The proposed approach is applicable to a variety of nanotechnology materials and structures, especially mass nanosensors. Eigenfrequencies are compared with those of local theory and conclusions are drawn. Influence of nonlocal effects, heavy fluid interaction and added point mass on dynamic responses is analyzed and the results are documented. Size phenomena are noted and discussed.

Heavy δ26Mg values in carbonate indicate a magmatic-hydrothermal origin of Carlin-type Au deposit

The Carlin-type Au deposits in Youjiang Basin, SW China, (referred to as Guizhou Carlin-type Au deposits) are the second largest Carlin-type Au province in the world after Nevada, USA. To date, the source of ore fluids that formed the Guizhou deposits remains controversial, hampering the formulation of a genetic model. Compared to Nevada Carlin-type Au deposits, a significant difference is that the Guizhou Carlin-type Au deposits contain abundant ore-stage dolomite in the ore. Herein, we present carbonate Mg isotopes combined with C-O isotopes from the giant Shuiyindong deposit to provide new insights into the source of ore fluids and to constrain the ore genesis of the Guizhou Carlin-type Au deposits.Petrographic observation shows that from least altered bioclastic limestone to high-grade ore, dolomite increased significantly, suggesting that dolomite formed as part of the Au mineralization process. Chemical analyses reflect a small amount of Mg in the ore fluids was variably added to ore during Au mineralization, and this added Mg was fixed in the dolomite. Although most ore-stage dolomite formed from the sulfidation of Fe in Fe-dolomite, some ore-stage dolomite formed by the combination of host rock calcite with Mg from ore fluids.The δ26Mg values of carbonate, primarily dolomite, range from −3.49‰ to −0.07‰, with a median value of −1.01‰. The δ18O values range from 21.7‰ to 27.6‰, with a median value of 23.2‰. The δ13C values vary from −14.6‰ to 1.2‰, with a median value of −0.7‰. The δ26Mg values exhibit a positive correlation trend with MgO, S, SiO2, and Carlin-suite elements (Au, As, Hg, Sb, Tl, and Cu), and a negative correlation trend with CaO. Comparison of Mg isotopes data from this study with the major Mg reservoirs indicates that the Shuiyindong samples contain heavier Mg isotopes that drifts towards the heavy Mg reservoirs (magmatic and metamorphic rocks) compared with normal carbonate rocks. Two mechanisms, namely heavy Mg addition from ore fluids and isotopic exchange reaction with heavy Mg-rich ore fluids, could have attributed to heavy Mg in carbonates in the Shuiyindong deposit.The Mg isotopes results, combined with other isotopes (e.g., S, Hg, and He-Ar) and geologic evidence, support a magmatic-hydrothermal origin for the ore fluids. The thick Devonian-Triassic sedimentary sequence and weak extension following sedimentation prevented igneous activity from reaching the surface. However, buoyant ore fluids released from the deep-seated intrusions are interpreted to have ascended along basement-penetrating faults and eventually produced the Guizhou Carlin-type Au deposits at shallow levels. This study implies that Mg isotopes are a novel proxy to infer ore fluids source and evolution, and that they can provide significant constraints on the genesis of hydrothermal deposit.

Rayleigh–Taylor instability in strongly coupled plasma

Rayleigh–Taylor instability (RTI) is the prominent energy mixing mechanism when heavy fluid lies on top of light fluid under the gravity. In this work, the RTI is studied in strongly coupled plasmas using two-dimensional molecular dynamics simulations. The motivation is to understand the evolution of the instability with the increasing correlation (Coulomb coupling) that happens when the average Coulombic potential energy becomes comparable to the average thermal energy. We report the suppression of the RTI due to a decrease in growth rate with increasing coupling strength. The caging effect is expected a physical mechanism for the growth suppression observed in both the exponential and the quadratic growth regimes. We also report that the increase in shielding due to background charges increases the growth rate of the instability. Moreover, the increase in the Atwood number, an entity to quantify the density gradient, shows the enhancement of the growth of the instability. The dispersion relation obtained from the molecular dynamics simulation of strongly coupled plasma shows a slight growth enhancement compared to the hydrodynamic viscous fluid. The RTI and its eventual impact on turbulent mixing can be significant in energy dumping mechanisms in inertial confinement fusion where, during the compressed phases, the coupling strength approaches unity.

Механический аналог движений неоднородной жидкости

The article considers the homogeneous vortex motion of an inhomogeneous fluid in a stationary ellipsoidal cavity arbitrarily oriented with respect to the direction of a uniform gravity field using the Lagrange variables. Uniform vortex motion of a fluid is a motion in which the rotor speed for all particles has the same value, and depends only on time. The article shows that the equations of homogeneous vortex motion of a heavy inhomogeneous fluid are possible in an ellipsoidal cavity with a linear density distribution and proposes a geometric interpretation of fluid motion. Using the Lagrange variables, the equations of motion of an inhomogeneous fluid are obtained, coinciding with the equations of a heavy rigid body motion around a fixed point, written in a fixed coordinate system arbitrarily located relative to the direction of a homogeneous gravity field.

Modal-interaction approach to the strong structural–acoustic coupling of an elastic Helmholtz resonator and an acoustic cavity containing a heavy fluid

This paper focuses on the development of a method for the accurate representation of the strong structural–acoustic coupling between an elastic Helmholtz resonator, a heavy fluid and an impedance tube. The Helmholtz resonator has an elastic wall and is connected to the impedance tube, yielding a system with two acoustic cavities coupled through a neck and the fluid–structure interaction between a liquid medium and a plate. The proposed analytical formulation is based on the modal superposition method in combination with a lumped parameter model of the neck. The effect of the evanescent waves is taken into account in the form of both the inertial attached length of the neck and the terms of the evanescent pressure modes in the governing equations, which are omitted in other methods. The formulation of the evanescent pressure field is redefined to include the reflected waves, thus expanding the application to the acoustic cavity of an arbitrary shape. Strong coupling between the heavy fluid and the plate is accomplished with the implementation of the non-resonant acoustic modes. Furthermore, the improved performance of the model for moderately thick plates is achieved with the combined approach of the Mindlin–Reissner theory mode shapes and the Kirchhoff–Love theory governing equations. The proposed model is validated with FEA simulations of three different resonator configurations and compared to other applicable methods. The results demonstrate substantially increased accuracy in the predicted response of the coupled structural–acoustic system.

A rare pediatric case report: Salvage transcatheter closure of atrial septal defect before parent‐to‐offspring living‐donor liver transplantation

1. Case presentationA 4‐month‐old female infant was admitted to our clinical ward in May 2021 due to her skin manifestation of the jaundice since birth. Her symptoms aggravated progressively despite various medications (e.g. Ursodeoxycholic Acid, Stronger Neo‐Minophagen C Tablets) were prescribed. Initial Work‐up. The admission abdominal ultrasound demonstrated contracted gallbladder, with no sign of common bile duct. Two weeks ago, she was admitted into Pediatric ICU, where her conditions worsened to coagulation dysfunction, digestive tract hemorrhage and hypotension. Diagnosis and Management. With initial work‐ups, the patient was diagnosed with congenital biliary atresia, liver cirrhosis, respiratory failure secondary to severe pneumonia (aspergillus and mycoplasma infections), secundum atrial septal defect (ASDII, 9.7mm) and hypoalbuminemia. Accordingly, CPAP‐assisted ventilation, injections of meropenem, vancomycin, and carprofen, as well as IVIG (2g/kg) and vitamin K1 were admitted. Echocardiogram confirmed pulmonary artery hypertension (PAH), right atrial enlargement, and portal hypertension. Further, she exhibited right heart failure (HF) symptoms, such as abdominal effusion, lower extremity edema. An urgent percutaneous ASD closure was scheduled prior to the parent‐to‐offspring liver transplantation, thereby reducing the high risk of right HF and PAH during the surgery.2. Surgical proceduresBriefly, a venous access was probed in groin area under local anesthesia (1% lidocaine). Upon bleeding, a 6F venous sheath tube (FAST‐CATHTM, ST.JUDE Medical) was gently inserted into the right femoral vein, followed by a Cordis MPA catheter (Cordis 6F, Johnson & Johnson Inc), which was further threaded through the vessel into heart. Once MPA catheter reached the left superior pulmonary vein through ASD, we released the guidewire and retracted the venous sheath tube simultaneously. (Fig. 1) Next, we inserted a 9F delivery sheath tube to transport the 10mm MemoPart™ ASD Occluder (FQFDQ‐I 10, SHSMA Corp) into anatomical left atrium through the interatrial hole. Once the umbrella at both atrial sides was released consecutively forming a sandwich‐like skeleton, the closure was successfully completed along with retraction of the occluder. (Fig.2)3. Follow‐upOne week after ASD closure, she received a living‐donor liver transplantation, and her liver function returned to normal shortly, with no further cirrhosis‐associated complications. Before discharge, echocardiogram demonstrated no shunt exist. (Fig.3)4. DiscussionStatistically, 15.8% of liver‐transplant recipients are having cardiovascular diseases, among whom 30% are diagnosed with ASD.Most children with ASD remain asymptomatic and their physical activities are typically unaffected till adolescence. Congestive HF and PAH will occur in patients with medium‐to‐large ASD around the age of 20‐30 years. In our case, the child was very young, yet with an extremely complicated condition requiring multiple resuscitation procedures. The large left‐to‐right shunt volume in the 9.7mm ASD was further exacerbated by heavy fluid loads formed during the rescues. Thus, transcatheter ASD occlusion was performed before liver transplantation to effectively manage the hemodynamic stability in perioperative period.

Commentary: Retinal detachment in eyes treated with Aurolab aqueous drainage implant for refractory glaucoma - Incidence and outcomes

The principal indication for glaucoma drainage devices (GDDs) is usually glaucoma refractory to filtering surgery.[1] Currently, commonly available GDDs are either valved like the Ahmed glaucoma valve (AGV; New World Medical Inc., Rancho Cucamonga, CA, USA) or non-valved GDDs like the Baerveldt glaucoma implant (BGI; Abbott Medical Optics, Abbott Park, IL, USA) and Aurolab aqueous drainage implant (AADI; Aurolab, Aravind Eye Hospital, Madurai, India), which have been shown to be safe and effective in both pediatric and adult populations. AADI has certain advantages over AGV. Since it is indigenously manufactured, it is highly cost-effective when compared to AGV. Studies have shown that it has a higher success rate, achieves significantly lower intraocular pressure (IOP), and the patients require less number of anti-glaucoma medications postoperatively. Some studies also indicate that the long-term IOP control is better with AADI when compared to that with AGV.[123] Postoperative posterior segment complications that may arise after usage of GDDs are hypotony and its consequences like hypotony maculopathy, serous choroidal effusion, choroidal detachment, suprachoroidal hemorrhage, retinal detachment, and endophthalmitis.[45] Overall, retinal complications have been described in 14%-50% of eyes with GDD implantation and majority occur within 35 days after GDD implantation.[5] Rhegmatogenous retinal detachment (RRD) occurs in approximately 5% of eyes after aqueous humor shunt implantation, with most occurring within 4 months of surgery.[6] Khan et al.[7] reported the incidence of RRD after AADI and AGV implantation to be 5.4% and 4.3%, respectively. The present authors analyzed the outcomes of 10 cases of RRD/1158 (0.86%) cases after AADI implantation.[8] Few points are to be kept in mind in these cases. As has been pointed out by the authors, some predisposing factors for the development of retinal detachment may have been there, such as uveitis, vitreous incarceration, scleral perforation, and retinal dialysis after pars plana tube placement. Nowadays, vitrectomy is often the preferred mode of treatment than scleral buckling procedure. Intraoperative choroidal drainage is often required as these RRDs are frequently associated with choroidal detachment. Rarely, suprachoroidal hemorrhage (SCH) is also a concomitant complication and intraoperative drainage of SCH is sometimes required. Moreover, retinal detachment after appositional choroidal effusion or expulsive hemorrhage can result in retinal adhesions, which are to be tackled meticulously. Use of heavy fluid perfluorocarbon liquid is particularly beneficial for retinal reattachment. Silicone oil is the preferred mode of endotamponade and it is recommended to use it at the end of surgery. Postoperative visual prognosis is often compromised as the chance of recurrence of retinal detachment is high. The present authors have also highlighted that poor visual recovery is primarily due to recurrent RRD as well as preexisting glaucoma. Tube blockade by silicone oil droplets may result in rise of IOP postoperatively, further worsening the glaucoma status. Many times, migration of emulsified silicone oil particles into the subconjunctival space through both the valved and non-valved devices has been reported.[910] When a scleral buckle is to be placed in a case with a preexisting GDD, utmost care should be taken to avoid the displacement of the tube placed in the anterior chamber. Studies have also shown the occurrence of phthisis bulbi following aqueous humor shunt implantation.[11] So, as has been concluded by the authors, vitrectomy with silicone oil tamponade appears to be the preferred approach in the management of these eyes, with IOP being well controlled post-vitrectomy, but it should be kept in mind that the visual outcomes are largely unsatisfactory due to recurrent RRD and preexisting advanced glaucoma.

From breakup to coiling and buckling regimes in buoyant viscoplastic injections

We study the injection flow of a heavy viscoplastic fluid into a light Newtonian fluid, via modelling and experiments. The injection is carried out downward, via an eccentric inner pipe inside a vertical closed-end outer pipe. This configuration results in a core viscoplastic fluid surrounded by an annular Newtonian fluid. The flow is structured and mixing is negligible. As the injection rate increases in a typical experiment, we observe three distinct flow regimes, associated with the core fluid behaviour, namely the breakup, coiling and buckling (bulging) regimes. In the breakup regime, the core fluid is yielded due to the extension caused by buoyancy, while in the buckling regime the yielding occurs due to the compression promoted by the pressure and the interfacial shear stress applied by the upward flow of the annular fluid. For the coiling regime, the core fluid remains largely unyielded until it exhibits a coiling behaviour. We develop a lubrication approximation model, using the Herschel–Bulkley constitutive equation, with dimensionless flow parameters including the Bingham number, the power-law index, the buoyancy number, the viscosity ratio, the diameter ratio, the eccentricity and the aspect ratio. Based on a reasonable prediction to the yielding onset, the model allows us to classify the flow regimes versus an elegant combination of the dimensionless numbers.

On the Stokes Nonlinear Waves in 2D

The Stokes nonlinear waves associated with the nonlinear problem of a free boundary with peaks in incompressible heavy fluid are studied in 2D. In the early works of the author by using the conformal mapping method this problem was reduced to the nonlinear integral equation with the weakly singular kernel. In this paper one parameter of the mapping is chosen sufficiently small and the equation is linearized. The approximate solution of the linearized equation is obtained. The profile of the free boundary is plotted by means of Maple-12.

A semi-analytic model for vibro-acoustic analysis of functionally graded shells of revolution

A semi-analytic model with wider applications is developed for vibro-acoustics of submerged functionally graded material (FGM) shells of revolution, and independent or coupled FGM shells are specific cases. For structural model, the shell is divided to many narrow segments treated as conical shells. Materials vary continuously in thickness direction according to the four-parameter power-law distributions about volume fractions of two constituents. Based on the first-order shear deformation theory (FSDT), differential equations are solved via expanding displacements as power series and Fourier series in meridional and circumferential directions, respectively. Continuity and boundary conditions are assembled to vibration governing equation. For acoustic model, Helmholtz integral equation is simplified to one line integral after expanding velocity and acoustic pressure as Fourier series in circumferential direction, and the pressure is further expressed as displacements of the shell. Then, structural and acoustic models are coupled as adding the acoustic pressure to continuity conditions. Through comparing results of developed model with the ones of literature and coupled finite element–boundary element method for some FGM shells, rapid convergence and high accuracy are demonstrated. Furthermore, discrepancies between vibro-acoustic responses of FGM, homogeneous and layered shells are slight, and effects of heavy fluid become more obvious as the volume fraction of the material with large stiffness decreases.

Hydrodynamics of horizontal heated buoyant jet in linearly stratified fluids

Horizontal buoyant jets in stratified fluids are investigated by employing a computational fluid dynamic model validated by experimental data. The characteristics of time mean flow, turbulence, and entrainment are quantified. We observed that turbulence parameters such as the turbulent kinetic energy, the turbulence dissipation rate, and turbulent viscosity attained their maximum values in the horizontal region. Here, the entrainment coefficient also reaches the maximum due to the instantaneous instability of the flow. The ascent region consists of the acceleration and deceleration stages due to the stratified ambience reversing the sign of buoyancy flux. In the acceleration ascent region, the entrainment coefficient stabilizes around 0.05. In the deceleration stage, the transition of the flow regime from plume- to jet-like regulates the entrainment. At the end of the ascent region, the jet reaches the maximum rise height (Hmax), which can be well predicted by a semiempirical function at a given Richardson number, buoyancy frequency, and Reynolds number. An enhancement of turbulent parameters is observed near the Hmax and could be attributed to overshooting and shearing between the up- and downflow. Analysis of density and velocity profiles shows the heavy fluids on the lower side of the jet core vertically separating from the center fluids, which drifted the velocity profile from a Gauss to a fat-tailed distribution and broke the self-similarity.

Исследование товарных форм тяжелых жидкостей глушения плотностью до 1600 и 1800 кг/м3 для оценки возможности применения в условиях месторождений «Газпром нефти»

Исследование товарных форм тяжелых жидкостей глушения плотностью до 1600 и 1800 кг/м3 для оценки возможности применения в условиях месторождений «Газпром нефти»

Relaxation of the Boussinesq system and applications to the Rayleigh\u2013Taylor instability

We consider the evolution of two incompressible fluids with homogeneous densities rho _{-}<rho _+ subject to gravity described by the inviscid Boussinesq equations and provide the explicit relaxation of the associated differential inclusion. The existence of a subsolution to the relaxation allows one to conclude the existence of turbulently mixing solutions to the original Boussinesq system. As a specific application we investigate subsolutions emanating from the classical Rayleigh-Taylor initial configuration where the two fluids are separated by a horizontal interface with the heavier fluid being on top of the lighter. It turns out that among all self-similar subsolutions the criterion of maximal initial energy dissipation selects a linear density profile and a quadratic growth of the mixing zone. The subsolution selected this way can be extended in an admissible way to exist for all times. We provide two possible extensions with different long-time limits. The first one corresponds to a total mixture of the two fluids, the second corresponds to a full separation with the lighter fluid on top of the heavier. There is no motion in either of the limit states.