Pressure Spikes Research Articles

Magnetohydrodynamic micropolar nanofluid flow with pulsation in a vertical permeable channel with Brownian motion, thermophoresis, and thermal radiation: a Buongiorno model approach

Abstract The current paper investigates the magnetohydrodynamic pulsating flow of micropolar nanofluid in a vertical porous channel by using Buongiorno’s nanofluids approach and utilizing entropy generation. The effects of thermal radiation, viscous dissipation, Brownian motion, and thermophoresis are considered. This finding holds implications for the fields of biomedical engineering, food processing systems, cancer treatment, pressure spikes, and nano-drug delivery in arteries. In this case, the
governing partial differential equations (PDEs) are converted into ordinary differential equations (ODEs) using the perturbation approach and we used Runge-Kutta fourth order method for the numerical approach. Graphical representations illustrate the
effects of nanoparticle concentration, velocity, temperature, and micro-rotation across various standard physical parameters. Furthermore, analysis and tabular presentation of the heat and mass transfer rates are provided. The data obtained indicate
that while raising the Hartmann number and coupling parameter decreases velocity profiles then increasing the Grashof number enhances velocity. The temperature of a micropolar nanofluid rises with increased Brownian motion and thermophoresis,
and falls with increased magnetic field and thermal radiation. The concentration of micropolar nanofluid is reducing by enhancing the thermophoresis and chemical reaction parameter. The rate of heat transfer is increasing as a result of increases
in thermal radiation, viscous dissipation, thermophoresis, and Brownian motion values. The heat transfer rate rises with increase values of the viscous dissipation, thermal radiation, the Brownian motion, and the thermophoresis parameters. This
study is useful for various real life applications like biological systems, biotechnology, pharmaceutical medicine, nano-drug development, and engineering industries.

Numerical study on the interaction of high-pressure water injection with lead-bismuth in the SGTR accident of LFR

The lead-bismuth cooled fast reactor (LFR) is one of the fourth-generation advanced reactors, which has the advantages of enhanced safety and high efficiency. However, the steam generator tube rupture (SGTR) accident is an important design-based accident in safety analysis, which may cause a severe threat to the integrity of the reactor system. In this paper, a numerical method was established to simulate the interaction of high-pressure water injection with lead-bismuth, and validated against the LIFUS5 experiment. A sensitivity analysis of the effect of water and lead-bismuth parameters on the water flow rate, vapor generation, and pressure evolution was conducted. The results indicated that the vapor generation at the early time was mainly caused by the water flash evaporation, followed by an accelerated vapor generation rate due to the enhanced heat transfer resulting from the vapor bubble fragmentation and the direct contact of lead-bismuth with water. It was found that a significant temperature gradient existed at the vapor and lead-bismuth interface. There was a pressure spike at the impact of water injection to the lead-bismuth, followed by a continuous increase of the overall pressure and the final stable pressure in the lead-bismuth vessel exceeded the initial water injection pressure. Sensitivity analysis results indicated that, as the water injection pressure increased, the water flow rate, vapor mass, and pressure in the vessel increased significantly, but the temperatures of water and lead-bismuth had little influence on the interactions.

Novel dual-enhanced stimulation for safe and efficient marine hydrate production

The commercial exploitation of natural gas hydrates is currently facing several challenges, including low production rates, limited recovery areas, and brief periods of continuous production. To address these issues, we propose a novel dual-enhanced stimulation (DES) method for marine hydrate reservoirs. This method involves injecting a special slurry that solidifies into porous, high-permeability, and high-strength slurry veins. These veins not only enhance permeability, allowing for faster gas and water flow, but also improve reservoir stability. This study experimentally investigated the split grouting of clayey-silty sediments with dual-enhanced slurry to assess the feasibility of DES and to explore the slurry diffusion mechanism and micro-pore structure of the veins. The results showed that split grouting with dual-enhanced slurry exhibited frequent fracture initiation with quick pressure spikes and sharp declines, suggesting shorter fractures in clayey-silty sediments. As vertical stress increased, the primary diffusion direction of the dual-enhanced slurry shifted from horizontal to vertical, aligning with fracture propagation patterns observed during fracturing. Unlike hydraulic fracturing in hard rocks, split grouting in clayey-silty sediments encountered more difficult conditions. These veins formed through a recurring cycle of splitting into fractures and filling with slurry, occurring more frequently in weaker sediments with slower injection rates and higher vertical stress. Increased vertical stress hindered slurry vein diffusion, easily resulting in compaction grouting near the grouting pipe. Additionally, three-dimensional laser scanning of the veins showed that those formed through split grouting were continuous and stable, with their thickness decreasing as diffusion distance increased. The morphology of these veins was shaped by factors such as grouting rate, formation stress, and elastic modulus, with higher rates and elastic moduli facilitating the formation of complex vein networks. Mercury intrusion porosimetry demonstrated that the DES method resulted in veins with consistent effective porosity between 65% and 70% and median pore sizes of 11–15 μm across different locations. These veins formed a well-connected porous network of smaller pores, significantly enhancing both permeability and sand control. The research findings validate the effectiveness of the DES method for marine hydrate reservoirs, providing a strategy for the safe and efficient exploitation of NGH resources.

Lifestyle modifications and environmental risk factors for glaucoma

Purpose of review To summarize recent evidence about the association between different lifestyle modifications and environmental risk factors and glaucoma. Recent findings Incorporating moderate exercise into the routine of glaucoma patients may help slow the progression of the condition. However, caution should be taken when using swim goggles, and it may be advisable to avoid certain yoga positions and heavy weight-lifting exercises, as they have been linked to intraocular pressure (IOP) spikes and potential risks for glaucoma patients. Various relaxation techniques may lower IOP. The evidence remains inconclusive about the association between vitamins intake and glaucoma. Dietary nitric oxide has been associated with a lower risk of glaucoma. Higher smoking intensity has been linked to faster visual field decline and retinal nerve fiber layer thinning. Additionally, there is currently insufficient evidence to support the use of marijuana in managing glaucoma, with side effects outweighing the proposed benefits. A significant association has been found between air pollutants and ganglion cell layer thinning, as well as a greater burden of glaucoma. Summary Lifestyle and environmental factors are increasingly recognized as significant contributors to glaucoma development and progression. These modifications should be integrated into a comprehensive treatment approach alongside medications or surgical interventions.

Complications after Gonioscopy-Assisted Transluminal Trabeculotomy in glaucoma treatment - literature review.

Glaucoma is a disease that leads to optic nerve damage and irreversible loss of the visual field. Gonioscopy-assisted transluminal trabeculotomy (GATT) is a minimally invasive glaucoma surgery technique, where the surgeon opens the trabecular network and Schlemm's canal to improve the outflow of the aqueous humor. This method has shown efficacy in reducing intraocular pressure in patients with primary and secondary glaucoma. GATT has gained popularity due to its minimally invasive nature, compatibility with cataract surgery and relatively low cost. Despite its advantages, the procedure can be associated with many complications such as hyphema, intraocular pressure spikes and corneal edema. In rare cases, it can lead to Descemet's membrane detachment or cystoid macular edema. The success of GATT procedure mostly depends on the surgeon's skill and experience, but also on the patient's risk factors, including age and preoperative intraocular pressure levels. Further studies are required to understand long outcomes and identify the patients, who may be at higher risk of complications.

New prefilled syringe aflibercept design. A cause of symptomatic IOP spike after aflibercept PFS?

To describe ocular hypertension cases after using a new aflibercept prefilled syringe and to assess the main characteristics of these eyes and their possible association with intraocular pressure (IOP) changes. Case series. We reported all the cases of ocular hypertension following aflibercept prefilled syringes (PFS) treatment in our department between April 2021 and December 2023. A total of 4183 eyes were treated with aflibercept PSF. Thirteen transitory IOP elevations were observed immediately after injection (0.3%). Two eyes had an IOP between 30-35 mmHg, five eyes had an IOP between 36-55 mmHg and three eyes had an IOP > 56 mmHg. The mean IOP was 45.5 mmHg±11.33. Only six eyes needed anterior chamber paracentesis (37.5%). The other patients were treated conservatively (ocular massage and/or IOP-lowering drops). The mean IOP after treatment was 15.71 mmHg±7.20. Visual acuity improved after treatment in all the patients. Compared with other injectors, reports have indicated a higher incidence of moderate and severe IOP spikes with aflibercept PSF. The European Medicine Agency (EMA) has associated this significant increase with incorrect syringe handling, leading to higher injection volumes. Although plunger misalignment seems to play a role in the IOP spikes, some other characteristics of this new injector could play a role. Factors such as syringe diameter, plunger alignment, and injection force may contribute to this issue. The reason some authors found no significant differences in IOP elevation after IVI, with aflibercept PFS, could be due to variations in patient characteristics, which may also play an important role in post-IVI pressure changes. Intraocular pressure spikes after aflibercept PFS can be explained by injector characteristics. The PFS of aflibercept has a domed plunger. Incorrect alignment between the base of the plunger and the black dosing line could cause an increase in the injected volume. Furthermore, the wider syringe diameter of aflibercept PFS could imply a larger injection force, increasing the risk of IOP elevation. Patient characteristics, such as previous VPP, axial length, or glaucoma history, may also play a role. Further studies are required to develop an ideal intravitreal syringe.

Two-Year Retrospective Study of Cataract Surgery and Schlemm Canal Hydrus Microstent in Black and Afro-Latino Patients.

The Hydrus Microstent has been shown to be efficacious in the treatment of Open-angle Glaucoma. We previously reported 1-year results of the Hydrus Microstent in Black and Afro-Latino patients. Here we report two-year results of the Hydrus Microstent in Black and Afro-Latino patients with mild to moderate open-angle glaucoma. This was a retrospective, nonrandomized study that was carried out at two private practices in Harlem, NY and Queens, NY. This study consisted of Black and Afro Latino patients who had a Hydrus Microstent implanted for the treatment of glaucoma. The evaluated parameters were intraocular pressure (IOP), reductions in the number of medications, mean deviation on visual field test and visual acuity. We excluded persons with advanced glaucoma and incomplete data. We included those with mild to moderate glaucoma and had complete two-year follow-up data. The study consisted of 86 patients and 86 eyes. The mean age was 69.The mean pre-op IOP was 14.1 on 2.17 medications. At two years the mean IOP was 14 (p = 0.651) on 0.42 medications (p = 0.000003); 88% of patients were medication free (p = 0.651), The MD on the visual field changed little from -5.73 preoperatively to -5.21 at two years. There were 3 intraocular pressure spikes and 1 case of hyphema that were treated and had complete resolution. No patients required secondary surgery. Our results show that at two years the Hydrus Microstent can maintain low intraocular pressures, reduce medication burden and, in aggregate, experienced little change in visual field Mean Deviation in Black and Afro Latino patients with mild to moderate glaucoma.

Surgical Outcomes of a Human Umbilical Cord Allograft Over the Ahmed Glaucoma Valve Plate for Refractory Glaucoma.

To report the surgical outcomes of sterile dehydrated human umbilical cord allograft over the Ahmed glaucoma valve (AGV) plate for refractory glaucoma. Thirty-four eyes of 34 patients with refractory glaucoma who underwent AGV with umbilical cord allograft (AmnioPlast THICK™; Life Cell International Private Limited, Mumbai, India) placed over the AGV plate between September 2021 and 2022 at a tertiary eye care centre were included (group1) and compared with 30 eyes of 30 patients undergoing AGV without amnioblasts (group 2). The intraocular pressure (IOP) at day one, one month, six months, and final IOP; the necessity for medications; or additional surgeries for IOP control were extracted from the hospital database. Success was defined as achieving an IOP below 22 mm Hg with or without glaucoma medications. IOP spikes after surgery were identified as a rise in pressure beyond 22 mm Hg at any point beyond six weeks post-surgery following an initial reduction of pressure exceeding 30% from the baseline pre-surgical IOP. A notable reduction in intraocular pressure (37 ± 7.9 mm Hg preoperative versus 14 ± 3.7 mm Hg at the final follow-up and 28 ± 3.6 mm Hg versus 18 ± 6.7 mm Hg in group 1 and 2, respectively) was observed in all eyes, with successful outcomes observed in 23 out of 34 eyes (67%). Ten eyes experienced a pressure spike, occurring at a median time of 12 months (range: 6-18 months), predominantly beyond six months post-surgery in group 1, while group 2 had similar pressure spikes in 21 of 30 eyes at a median time of two months (range: 1-5 months). No eyes necessitated supplementary glaucoma procedures, concluding with a final IOP of 14 ± 3.7 mm Hg at 1.9 ± 0.8 years. Vision loss occurred in only one of the 11 eyes that failed owing to non-glaucoma-related causes in group 1. The human umbilical cord allograft plate over the AGV plate may help in postponing the onset of intraocular pressure spikes beyond traditionally defined timelines. This helps in reducing and delaying the hypertensive phase occurring due to fibrosis.

Real-world outcomes of micropulse transscleral laser therapy in glaucoma patients: Efficacy of initial and repeated treatment, transient intraocular pressure spikes

PurposeTo investigate the clinical outcomes of micropulse transscleral laser therapy (MP-TLT) in a cohort of glaucoma patients, including safety profile, post-operative transient intraocular pressure (IOP) spikes, long-term efficacy and prognostic factors in terms of IOP-lowering. MethodsThis was a retrospective observational cohort study. Medical records of all patients who consecutively underwent MP-TLT between May 2019 and February 2023 at a tertiary referral centre were scrutinised and relevant data were retrospectively analysed. ResultsA total of 131 patients (138 eyes) with a mean age of 73.2 ± 14.2 years were included. Mean pre-interventional IOP was 24.1 ± 9.1 mmHg. Within 6–12 h following the intervention on the same day, an IOP spike was regularly observed, reaching on average 31.7 ± 10.3 mmHg (p < 0.001 to baseline). Two years after the intervention, mean IOP was 16.1 ± 5.6 mmHg (p < 0.005 to baseline). In 18 eyes, the treatment was repeated, and the IOP lowering effect was more durable after the second intervention compared to the first one (Cox-Mantel test, p=<0.005). Apart from the transient post-interventional IOP spikes, no severe complications were observed. ConclusionsMP-TLT is associated with significant IOP spikes in the first post-operative hours. Thus, close post-interventional IOP monitoring or even preventive (additional) IOP-lowering treatment may be considered. In the long term, the procedure yields favourable outcomes in terms of safety and IOP reduction. Repeated MP-TLT treatment, if necessary, seems to achieve more sustained IOP reduction than the initial treatment.

Complications Following XEN45 Gel Stent and Glaucoma Drainage Device Implantation During Glaucoma Fellowship.

Purpose XEN45 Gel Stent and glaucoma drainage device (GDD) implantation is safe and effective for glaucoma treatment and should be taught during glaucoma fellowship training. However, complications may still occur, with potentially sight-threatening consequences. The purpose of this study is to describe the management of complications following a series of XEN45 Gel Stent and GDDsurgeries performed over the course of glaucoma fellowship training. Methods This is a retrospective case series of XEN45 Gel Stent surgeries performed on 16 eyes and GDD surgeries performed on seven eyes. Patient demographics, disease characteristics, and complications are reviewed. The intra- and postoperative course of five select cases with complications are described in detail. Results The most frequent complications following XEN45 implantation were transient hypotony (10 eyes, 63%), reduced visual acuity (VA) (five eyes, 31%), choroidal effusion (three eyes, 19%), hyphema (two eyes, 13%), and intraocular pressure (IOP) spike (two eyes, 13%). Thirteen eyes (81%) required bleb needling, and three eyes (19%) required XEN45 replacement. Complications following GDD implantation included hypotony (three eyes, 43%), reduced VA (two eyes, 29%), choroidal effusion (two eyes, 29%), IOP spike (two eyes, 29%), implant exposure (two eyes, 29%), and shallow anterior chamber (one eye, 14%). Three eyes (43%) required revision or explantation with a secondary glaucoma surgery. One choroidal effusion following XEN45 surgery and one following GDD surgery were hemorrhagic choroidal effusions requiring surgical drainage. Conclusion Significant and potentially sight-threatening complications may occur following XEN45 Gel Stent and GDD implantation performed over the course of fellowship training. Glaucoma fellows should be ably equipped to recognize, diagnose, and manage these complications both intra- and postoperatively.

Best-estimate water hammer simulations to avoid the calculation of unrealistically high loads or unphysical pressure and force peaks

For safety-related systems fluid loads due to fluid transients have to be quantified for subsequent structural analyses to ensure their integrity or function, as required. Usually transient fluid loads in pipe systems are determined with one-dimensional water hammer software. For single-phase liquid flow, the method of characteristics (MOC) is often used that gives in this case appropriate results. For the consideration of local vapor bubbles, the MOC is combined with the discrete vapor cavity model (DVC). The DVC model may generate unrealistic pressure spikes due to the calculation of the collapse of multi-cavities in scenarios, where only one vapor bubble should actually occur. The application of a two-phase code may improve the calculation results. One requirement for the latter codes is the ability to calculate the propagation of steep gradients without suffering from numerical diffusion to exclude the underestimation of fluid loads. This is commonly attained by applying higher-order numerical schemes. However, the application of a numerical method of pure 2nd order leads to the calculation of unphysical oscillations at steep gradients causing severe problems during the solution. To exclude this, numerical methods with flux limiters can be used. With their application, the calculation of unrealistically high loads due to numerical deficiencies can be minimized. In addition, the consideration of further physical effects, that lead to the reduction of loads during transient flow processes, allows for a more realistic calculation of the loads. These are unsteady friction, widening of the pipe caused by pressure increase, fluid-structure interaction at junctions and due to friction, degassing of gas that is initially dissolved physically in a liquid and thermodynamic non-equilibrium during vapor bubble collapse. The in-house code DYVRO applies a second-order accurate scheme with flux limiters based on the Godunov method and can account for the above-described physical phenomena. It is shown by comparison of calculation results obtained by DYVRO with experimental data from literature that with modeling of these physical effects the loads can be calculated more realistically. Generally, these loads are lower than the results calculated by simplified models, which do not account for these effects. Considering that these loads are applied in subsequent structural analyses, cost-intensive oversizing of pipes and their supports can be avoided, by ensuring the necessary safety.

Delayed interface fluid syndrome in a post laser-assisted in situ keratomileusis: A rare complication

Interface fluid syndrome (IFS) is a rare complication seen post-laser-assisted in situ keratomileusis (post-LASIK). This report describes two unusual cases in which patients underwent ocular surgeries and developed delayed onset interface fluid. Both the patients had undergone uneventful laser-assisted in situ keratomileusis (LASIK) decades ago; case 1 underwent uneventful phacoemulsification and vitrectomy with gas tamponade and case 2 underwent uneventful phacoemulsification with intraocular lens implantation. Possible causes of IFS could be steroid-induced intraocular pressure (IOP) spike, intraocular inflammation, or both. IFS can be seen any time after refractive surgeries and can be a lifelong complication after LASIK surgery. Inaccurate IOP measurement due to underestimation should be borne in mind while measuring IOP in such patients. This report highlights the challenges in diagnosing IFS and the importance of correct IOP measurement in such cases to avoid irreversible vision loss.

Oscillation Times in Water Hammer Signatures: New Insights for the Evaluation of Diversion Effectiveness in Field Cases

Diversion is a crucial technique for effectively improving shale reservoir production by creating more complex fracture networks. Evaluating diversion effectiveness is necessary to optimize the parameters in hydraulic fracturing. Water hammer diagnostics, an emerging fracturing diagnosis technique, evaluate diversion effectiveness by analyzing water hammer signals. The water hammer attenuation, as indicated by the oscillation time, correlates with the complexity of fracture networks. However, it remains unclear whether the oscillation time is associated with diversion effectiveness. This paper elucidates the relationship between the water hammer oscillation time and diversion effectiveness by taking the probability of diversion and the treating pressure response as the evaluation criteria. Initially, a high-frequency pressure sensor was installed at the wellhead to sample the water hammer signals. Next, the oscillation times were determined using the feature extraction method. Simultaneously, the probability of diversion and the treating pressure response were calculated using the cepstrum error function and treating pressure curve, respectively. Then, the relationship between the oscillation time and diversion effectiveness was analyzed. Finally, a rapid judgment method for evaluating diversion effectiveness based on the water hammer oscillation time was proposed. The results indicated a negative correlation between the probability of diversion and the oscillation time, with higher probabilities resulting in lower oscillation times. The oscillation times exhibited a negative correlation with the treating pressure response, including the treating pressure increases and diversion pressure spikes, wherein a greater pressure differential led to lower oscillation times. Drawing from the statistics of a shale gas horizontal well in Sichuan, a better diversion effectiveness is associated with fewer oscillations, demonstrating a negative correlation between the diversion effectiveness and the oscillation time in water hammer signatures. Finally, a rapid judgment method for evaluating diversion effectiveness was proposed, utilizing the 95% confidence interval of the mean oscillation time. This paper offers useful insights into evaluating diversion performance in field cases.

Adaptive Processing Enabled by Sodium Alginate Based Complementary Memristor for Neuromorphic Sensory System.

Adaptive processing allows sensory systems to autonomically adjust their sensitivity with exposure to a constant sensory stimulus and thus organisms to adapt to environmental variations. Bioinspiredelectronics with adaptive functions are highly desirable for the development of neuromorphic sensory systems (NSSs). Herein, the functions of desensitization and sensitivity changing with background intensity (i.e., Weber's law), as two fundamental cues of sensory adaptation, are biorealistically demonstrated in an Ag nanowire (NW)-embedded sodium alginate (SA) based complementary memristor. In particular, Weber's law is experimentally emulated in a single complementary memristor. Furthermore, three types of adaptive NSS unit are constructed to realize a multiple perceptual capability that processes the stimuli of illuminance, temperature, and pressure signals. Taking neuromorphic vision as an example, scotopic and photopic adaptation functions are well reproduced for image enhancement against dark and bright backgrounds. Importantly, an NSS system with multisensory integration function is demonstrated by combining light and pressure spikes, where the accuracy of pattern recognition is obviously enhanced relative to that of an individual sense. This work offers a new strategy for developing neuromorphic electronics with adaptive functions and paves the way toward developing a highly efficient NSS.

Consequences of Clot Formation and Hyphema Post-Internal Trabeculotomy for Glaucoma.

Clot formation and hyphema following internal trabeculotomy represent distinct clinical entities. The eyes with clot formation exhibited a more pronounced postsurgical intraocular pressure spike, longer residual intracameral bleeding, and a higher risk of reoperation. The aim of this study was to investigate the consequences of clot formation and hyphema in the anterior chamber after internal trabeculotomy. In this retrospective interventional comparative study, we investigated the surgical outcomes of internal trabeculotomy in 142 eyes of 142 patients at Sensho-kai Eye Institute. Concurrent clot formation and L≥2 hyphema (height of hyphema ≥1mm) was observed in 22 eyes. In these cases, the postsurgical IOP was 29.3mmHg at 1 week, significantly higher than the 16.1mmHg in eyes that had L≥2 hyphema but without clot formation ( P =0.0002). However, the 1-week postsurgical IOP in L≥2 hyphema and clot (-) eyes, which measured 16.1mmHg was not significantly greater than that in L<2 hyphema and clot (-) eyes, which measured 18.7mmHg ( P =0.162). Thus, clot formation was identified as a significant factor contributing to high postsurgical IOP at 1 week. The resolution time for anterior chamber bleeding in eyes with concurrent clot formation and L≥2 hyphema was 12.3 days, longer than the 5.8 days observed in L≥2 hyphema eyes without clot formation ( P =0.016). Among the 22 eyes with concurrent L≥2 hyphema and clot formation, 8 required anterior chamber washout. Three of the 10 eyes that underwent washout necessitated additional trabeculectomy, a rate significantly higher than that in nonwashout eyes ( P <0.001). After internal trabeculotomy, the sequelae of concurrent clot formation and L≥2 hyphema in the anterior chamber were more severe than those of simple hyphema without clots. Clot formation negatively affected postoperative IOP.

Snap-induced flow in a closed channel

Snap-through is a buckling instability that allows slender objects, including those in plant and biological systems, to generate rapid motion that would be impossible if they were to use their internal forces exclusively. In microfluidic devices, such as micromechanical switches and pumps, this phenomenon has practical applications for manipulating fluids at small scales. The onset of this elastic instability often drives the surrounding fluid into motion – a process known as snap-induced flow. To analyse the complex dynamics resulting from the interaction between a sheet and a fluid, we develop a prototypical model of a thin sheet that is compressed between the two sides of a closed channel filled with an inviscid fluid. At first, the sheet bends towards the upstream direction and the system is at rest. However, once the pressure difference in the channel exceeds a critical value, the sheet snaps to the opposite side and drives the fluid dynamics. We formulate an analytical model that combines the elasticity of thin sheets with the hydrodynamics of inviscid fluids to explore how external pressure differences, material properties and geometric factors influence the system's behaviour. To analyse the early stages of the evolution, we perform a linear stability analysis and obtain the growth rate and the critical pressure difference for the onset of the instability. A weakly nonlinear analysis suggests that the system can exhibit a pressure spike in the vicinity of the inverted configuration.

New thermal solver for mitigating surface temperature instability in laser-induced heating

An accepted approach to computing laser-induced peak surface temperature is to employ the enthalpy formulation of the transient heat conduction equation [Grigoropoulos et al., Adv. Heat Transfer 28, 75–144 (1996); Sawyer et al., J. Laser Appl. 29, 022212 (2017)]. This approach is generally implemented using an explicit numerical scheme to solve the thermal transport equation. While it offers the advantage of modeling the solid-melt phase transition automatically, the approach results in instability-like behavior in the computed surface temperature. When laser-induced ablation becomes significant, the heating rate in the surface cell becomes unrealistically large. This results in spikes in the computed peak surface temperature due to large errors in calculating the heating rate. In this paper, we present a new approach, which we refer to as the Moving Frame Solver, that employs a moving-coordinate frame of reference, located at the receding evaporating surface. We also use an analytical representation for the phase transition region of the enthalpy-temperature relationship. The Moving Frame Solver combined with an implicit scheme leads to a stable solution without surface temperature, pressure, or velocity spikes. In other words, any instability in these computed parameters due to use of an explicit scheme (such as Dufort–Frankel) has been eliminated. Details of the new thermal solver and example calculations are presented. Numerical experiments suggest that the surface cell size needs to be small, ∼0.1 μm, to obtain a highly accurate solution with a typical metal such as aluminum. Using the Moving Frame Solver with a refined grid near the surface, but coarse elsewhere, enables accurate and stable surface temperature computation.

Needle goniotomy decreases early intraocular pressure spike compared with phacoemulsification alone

PurposeTo evaluate the effect of needle goniotomy during phacoemulsification cataract surgery on early IOP spikes in patients with glaucoma compared with phacoemulsification alone. DesignRetrospective case control series MethodsCataract surgeries with concurrent goniotomy for glaucoma (n = 46) were compared with controls (n = 115) with and without glaucoma. IOP was measured prior to surgery and monitored through six months postoperatively. Between-group differences in IOP and postoperative IOP reduction were tested with ANOVA and Welch's 2-sided t-tests. Demographic, clinical, and intraoperative variables were also analyzed for significant association with postoperative IOP using univariate analysis. The incidence of IOP spike was evaluated according to two criteria: IOP > 30 mmHg or IOP > 10 mmHg above baseline. ResultsPhaco-goniotomy significantly lowered IOP at postoperative day one and month six. Following goniotomy, IOP was reduced on average 28 % (95 % CI [21, 36]) at month six compared with baseline, a mean reduction of -6.3 mmHg (95 % CI [-8.6, -4.0]), and a significantly greater reduction than in glaucoma controls (1 %, 95 % CI [-9, 7] and -0.3 mmHg, 95 % CI [-1.7, 1.1], p < 0.05). The average month six IOP following phaco-goniotomy was 12.9 mmHg (95 % CI [11.6, 14.1]), significantly lower than for glaucoma controls (15.6 mmHg, 95 % CI [14.0, 17.3], p < 0.05). The incidence of early IOP spike was significantly higher in glaucoma controls (23.1 %) than in the phaco-goniotomy cohort (6.0 %) (OR = 4.5, p < 0.05). There were no associations between CDE, ultrasound and aspiration time, or irrigation volumes on postoperative IOP. We showed that preoperative IOP was the only significant contributor to postoperative IOP reduction after phaco-goniotomy. ConclusionIncidence of early postoperative IOP elevation after phacoemulsification alone was 4.5 times higher than after phaco-goniotomy. Needle goniotomy may be a consideration for IOP lowering in glaucomatous eyes having cataract surgery.

Impact of the meteorological storm in the Moscow region in May 2017 on variations in upper atmosphere parameters

A numerical simulation of atmospheric wave propagation ahead of a strong pressure spike during a squall in Moscow on May 29, 2017, was performed using a three-dimensional version of the high-resolution nonlinear numerical model AtmoSym. The meteorological source was specified based on experimental observations of a network of 4 microbarographs located in the Moscow region. Wave perturbations in the upper atmosphere caused by the generation of internal gravity waves by the meteorological source were estimated.

Computational Study of Fluidic-Valve Injectors for Detonation Engines

The performance of detonation engines depends on propellant injectors. This study investigates a fluidic-valve injector mounted to a detonation tube. The injector is equipped with a recessed cavity connecting to the fuel plenum. After verifying the theoretical and numerical framework, three cases (I, II, and III) are analyzed, each representing different combinations of initial injector conditions and fuel supply setups. In all cases, a detonation wave is initiated near the headend of the detonation tube. It propagates through the initial section of the tube and undergoes diffraction and deformation at the flush-wall orifice. Among the considered cases, Case III, featuring a pre-pressurized initial injector flowfield and a total-pressure-inlet boundary, demonstrates the best agreement with the experimental results. It reveals a strong interaction between the longitudinally traveling detonation wave and the transverse propellant plume expanding from the orifice, causing the detonation wave to split. One part continues within the tube, while the other diffracts into the injector, creating a recirculation zone. Shock waves propagate within the injector and reflect at the base of the cavity, generating pressure spikes similar to the experimental observations. However, the contact surface separating the burnt products and fresh propellant reaches only a limited distance into the injector, suggesting a short interruption time and rapid recovery of the propellant supply.