In situ imaging of oxidation dynamics within aluminum laser induced plasmas.

Investigation of hydraulic performance and internal flow in a lead-bismuth coolant pump for nuclear reactors

Solid rocket motors (SRMs) have limited propulsion performance due to their short fuel combustion duration and low specific impulse. The supplementary combustion nozzle (SCN) injects air into the nozzle expansion section to promote secondary combustion of unburned exhaust gases, providing a novel solution to the aforementioned problems. This study fills the knowledge gap in coupled inlet-nozzle interactions using a comprehensive computational framework. The framework constructs the coupled internal and external flow fields of the SCN. It solves these fields using 2D axisymmetric compressible Navier-Stokes equations and the k-ε turbulence model. This allows for a systematic study of key inlet parameters, including outflow angle, outflow position, and mass flow rate. The obtained results demonstrate that an outflow angle of 0° provides a balance between the combustion efficiency and inlet total pressure recovery coefficient, representing the optimal configuration. A proximal inlet positioning near the throat increases the thrust gain, which results in inducing significant backpressure surges. This requires comprehensive design trade-offs taking into consideration that a peak net thrust gain occurs at an air-to-gas mass flow ratio of 1.23. After conducting a multi-parameter coupled optimization, the SCN achieves a net thrust gain of 8.18%, significantly outperforming conventional nozzles. This study provides theoretical insights for high-specific-impulse design in SRMs.

Numerical analysis of unsteady vortex evolution and internal flow mechanisms in a three-twisted-blade pump using OpenFOAM

Internal flow characteristics and performance evaluation of centripetal turbines in ocean thermal energy conversion

Synergistic thermal performance control of internal flow using Al2O3-TiO2/water hybrid nanofluids in liquid cooling jacket of brushless direct current motors for electric vehicles

Lost circulation is one of the most common and costly drilling problems, especially in formations with weak rock strength, natural fractures, or high permeability. If drilling fluid losses are not controlled quickly, they can lead to serious operational complications such as wellbore instability, stuck pipe, reduced drilling efficiency, and in extreme cases, well control risks. For this reason, predicting and managing potential lost circulation zones is a key part of safe and efficient drilling planning. One effective method used by drilling engineers is evaluating the mud weight window, which helps identify intervals where the formation is more likely to absorb drilling fluid. The mud weight window represents the safe range of drilling fluid density between pore pressure and fracture pressure. Maintaining mud weight within this window allows the well to be drilled with sufficient pressure control while avoiding formation breakdown. When mud weight or equivalent circulating density exceeds the fracture pressure, the formation may crack and begin to take fluid. This is especially critical in narrow mud weight windows, where even small changes in density or circulating pressure can trigger losses. By analyzing the mud weight window before drilling, engineers can estimate which depths have a higher risk of losses and prepare mitigation plans in advance. In zones where losses are expected, a common preventive practice is to prepare a Lost Circulation Material (LCM) pill and keep it ready in the active mud system. This approach reduces response time, allowing the drilling crew to treat losses immediately once they are detected. LCM pills are specially designed mixtures containing materials that bridge and seal fractures, pores, and weak intervals in the formation. Depending on the formation type and the severity of the losses, LCM blends may include fibrous, granular, and flaky components. These materials work together to create an effective sealing barrier, restoring circulation and reducing further mud losses. Selecting the correct LCM blend requires careful consideration of both formation characteristics and drilling equipment limitations. The type of loss zone, estimated fracture size, mud system compatibility, and past offset well experience all influence material selection. Additionally, particle size is a critical factor when downhole tools such as mud motors, MWD (Measurement While Drilling), and LWD (Logging While Drilling) systems are present in the bottom hole assembly. Oversized LCM particles can plug internal flow passages, damage tool components, and cause motor or sensor failures. Therefore, many LCM pills are designed as “tool-safe” blends, ensuring particles can pass through the smallest tool restrictions while still providing effective sealing performance. Overall, combining mud weight window analysis with proactive LCM preparation offers a practical and efficient strategy for lost circulation management. This integrated approach improves operational readiness, minimizes non-productive time, protects expensive downhole equipment, and enhances drilling safety. By identifying risky intervals early and applying appropriate preventive and corrective measures, drilling teams can significantly reduce the impact of lost circulation and improve the overall success of drilling operations. Keywords: Mud weight window, LCM, ECD, mud motor, MWD, LWD.

The development of high-efficiency energy dissipation devices is crucial for mitigating the significant threat posed by seismic loads to modern buildings. Therefore, the purpose of this work is to design a novel fluid viscous inerter damper (FVID) and systematically investigate its mechanical performance through theoretical derivations, experiments, and finite element simulations. Furthermore, the impact of FVIDs on the seismic performance of structures is comprehensively evaluated. The advantage of FVID is that under external excitation, the fluid can flow through multiple channels, thereby generating inertial and damping forces to dissipate energy. The theoretical model of FVID’s output force is determined based on FVID’s construction and fluid flow characteristics. The hysteresis performance of the FVID is evaluated through cyclic loading tests, and the influence of the cross-sectional radius and number of turns of the helical tube on its output force is analyzed. By performing finite element simulations of the internal flow field of FVID, the distributions of fluid pressure and velocity at different positions within FVID are analyzed. Based on Simulink, the focus is on investigating the control effect of FVID on structural responses under non-pulse near-field ground motions, pulse-type near-field ground motions, and far-field ground motions. The results indicate that the FVID has a strong energy-dissipation capacity and can effectively reduce structural responses under different types of earthquakes. The cross-sectional radius of the helical tube is a key design parameter that determines the damper’s output force. For highly destructive pulse-type near-field ground motions, FVIDs still exhibit excellent comprehensive performance in the structure.

ABSTRACT Subaerial Pyroclastic Density Currents (PDCs) and Subaqueous Eruption‐Fed Density Currents (SEFDCs) produced during volcanic eruptions can present major hazards to surrounding communities and ecosystems. The bedforms deposited by these volcanic density currents can provide insights into the nature of transport and depositional processes, which can aid in hazard prediction. Most existing models for the deposits of volcanic density currents have been developed from turbidite systems using numerous outcrop, seafloor and experimental observations. However, little work has been done to study the nature of deposition and bedform development under supercritical conditions in PDCs or SEFDCs. Here, we review our current knowledge of the nature of supercritical flow in subaerial PDCs and SEFDCs, as well as the character of backstepping bedforms that develop in these systems. We aim to address the following questions: (1) what are the effects of the ambient fluid (i.e. water vs. air) on flow dynamics in volcanic density currents, (2) how does the role of the ambient fluid affect deposition, (3) what are the alternative mechanisms for the formation of backstepping bedding in volcanic density currents, (4) what are the criteria for differentiating between deposits in the subaerial and subaqueous realm and (5) what are the criteria for differentiating between backstepping bedding formed under supercritical flow conditions and backstepping bedding formed under alternate mechanisms. We show that SEFDC deposits generally conform with established models for deposits of supercritical flow in subaqueous systems, as Froude‐supercritical conditions are favoured in the subaqueous realm due to the dynamic viscosity and density of the ambient fluid. We further show that the internal character and flow dynamics of subaerial PDCs are much more variable and do not promote the development of large, laterally continuous structures. We compare and contrast these findings and suggest future directions for research.

ABSTRACT To investigate the influence of cracks on the response characteristics of explosive columns under drop-weight impact, a finite element simulation model of a drop-weight impacting an RDX-based aluminized explosive column was established. Columns without cracks, with a close fit, with 1 mm cracks, and with 1.5 mm cracks were prepared, and drop-weight impact loading experiments were conducted. The computational results indicate that the crack edge is the point of maximum stress during drop-weight loading, and the radial displacement of nodes around the crack is significant. Compared to intact and close-fit columns, columns with cracks exhibit a significant increase in the internal maximum stress, stress rate, strain, strain rate, and radial flow velocity, with the magnitude of increase being greater for wider cracks. Drop-weight loading experiments show that the ignition thresholds for aluminized explosive columns under impact are essentially equivalent under no-crack and close-fit conditions. When a crack is present, the ignition threshold under impact significantly decreases. A flow phenomenon of internal material from high-density to low-density regions was observed at the half-radius position along the column axis. The experimental results show good consistency with the simulation results.

The marine centrifugal pump is one of the most energy-intensive pieces of equipment in ship auxiliary machinery, and the efficient design of its hydraulic components can effectively reduce the total energy consumption of the ship system. Aiming at the complex three-dimensional twisted blade profile structure of the marine centrifugal pump, this paper optimized the clonal selection algorithm and constructed an automatic hydraulic optimization design method for the high-efficiency centrifugal pump impeller. Considering the multi-condition operation characteristics of the marine centrifugal pump, a performance test platform for the marine centrifugal pump was built, and the actual operating conditions of the model pump were tested to obtain its performance characteristics under operating conditions. The numerical simulation method was employed to capture and analyze the internal flow field and flow characteristics of the model pump. Addressing the design challenges of the marine centrifugal pump impeller, which involve multiple parameters with significant interactions, a traditional clonal selection algorithm was enhanced using a Slime Mold Algorithm, and a hybrid Clonal Selection Algorithm integrated with Slime Mold and Tangent Flight mechanisms was established. Based on the MATLAB and ANSYS platforms, an automated hydraulic optimization design framework for the centrifugal pump impeller was established. Using the optimized clonal selection algorithm, with the operational efficiency of the model pump as the optimization objective and controlling ten key geometric parameters of the blade profile through Bézier curves, the blade profile optimization design was achieved. The pump hydraulic efficiency under the rated flow condition increased by 7%. The unsteady internal flow efficiency of the optimized marine centrifugal pump was significantly improved. The blade optimization alleviated flow separation phenomena on the tangential surface of the impeller and in partial regions of the volute, reduced the flow loss area, and significantly decreased overall flow losses.

Precise control of thin liquid film deposition is crucial in applications where film stability and internal liquid flow significantly impact the dry film shape or the efficiency of sample or drug delivery. No prior work has automated the extraction and measurement uncertainty quantification of film geometric parameters from dual-view optical visualization with minimal user input. We present Python-based software that extracts time-resolved film thickness, width, and the positions of three contact lines from visual data using computer vision. The utility of such analysis is demonstrated by depositing 30% glycerol on a flexible tape through a circular nozzle orifice. The nozzle is positioned at a distance of h = 0.3 mm from the tape at an angle of attack α = 45°, with deposition controlled at a volume flow rate V˙ = 30 μL min−1 and tape velocity v = 1.0 mm s−1. Expanded measurement uncertainties are 21 μm, 22 μm, and 53 μm for the upstream static, downstream static, and upstream dynamic contact line positions, respectively, with maximum relative uncertainties of 10.3% and 8.2% for film thickness and width. Static contact line oscillations remain within measurement uncertainty, whereas the upstream dynamic contact line exhibits resolvable oscillations. This dual-view framework provides high-resolution insights into liquid film dynamics, which is crucial for comprehensive control of liquid film deposition.

Spreading dynamics of drops on a solid surface submerged in different outer fluids.

We conducted a prospective interventional before-after study to evaluate the effect of left stellate ganglion block on left internal mammary artery diameter and blood flow in patients undergoing myocardial revascularization surgery. The aim was to assess the change in left internal mammary artery diameter and blood flow by ultrasound before and after left stellate ganglion block. In 45 patients undergoing coronary artery bypass grafting surgery, left stellate ganglion block was given under ultrasonographic guidance with 10ml of 0.25% bupivacaine. Left internal mammary artery diameter and velocity time integral were measured using ultrasonography, and compared before and 20min after the block at the level of the 2nd or 3rd rib. Heart rate (HR), systolic, diastolic, and mean arterial blood pressures were recorded before and 20min after the block. Inadequacy of left internal mammary artery flow, demonstrable by electrocardiographic changes, regional wall motion abnormalities, or angiographically if indicated postoperatively, was recorded. Incidence of in-hospital mortality and significant cardiac arrhythmias were also noted. There was a statistically significant increase in the left internal mammary artery diameter and blood flow before and after left stellate ganglion block and a decrease in HR, systolic, diastolic, and mean arterial blood pressures. The frequency and percentage of significant cardiac arrhythmias in the intra- and postoperative periods was 6 (13.3%). Ultrasound-guided left stellate ganglion block consistently increased left internal mammary artery diameter and blood flow in patients undergoing myocardial revascularization.Central figure. The online version contains supplementary material available at 10.1007/s12055-025-02091-7.

Numerical investigation of internal flow dynamics and heat transfer in injection-driven chamber

Research on the influence of gas-ingested flow on internal flow characteristics in reactor coolant pumps

Research on internal flow behavior of bulb tubular pump under stall conditions using DDES turbulence model

Modeling droplet size in two-phase internal flow atomization based on bubble-film burst hypothesis

Abstract This study investigates the influence of nozzle opening arc angle on internal flow recirculation and performance of a Banki turbine using two-dimensional CFD. Using ANSYS Fluent with a VOF multiphase formulation and a four-equation SST transition turbulence model, transient simulations were performed on a previously optimized turbine geometry for nozzle arc angles of 50°, 80°, 90°, 100°, and 110°. Mesh sizes ranged ∼60,000–80,000 elements; boundary conditions included a total-pressure inlet (18,688.05 Pa) and pressure outlets representing vertical free-surface and horizontal discharge. Convergence used residuals of 1e-3 with up to 200 iterations per timestep. Results show a clear optimum at a 90° nozzle arc: peak efficiency ≈70.5% at 300 rpm and a predicted maximum of 71.07% near 325 rpm, compared with ∼59.98% for the existing 50° nozzle. Larger arcs increase the number of effective energy-converting blades (from six to eight), but excessive discharge at 110° reduces efficiency. Flow-field analysis attributes the 90° advantage to reduced recirculation eddy viscosity, a more isotropic vortex core, and lower turbulence kinetic energy dissipation near the second-stage blades. The optimized design aligns with several prior studies and narrows the gap with experimental findings (≈2% difference for the 90° case). These CFD results support adopting a 90° nozzle arc to minimize internal recirculation losses and improve Banki turbine performance.

Energy-efficiency optimization and internal flow characteristics with a variable outlet width strategy in large-scale centrifugal impeller system