Low Pressure Region Research Articles

Modeling Investigation on Gas Backflow Performances in Screw Vacuum Pump

Rotor structure has a great influence on the gas backflow in a screw vacuum pump. The characteristics of the gas main flow along the spiral groove of the screw rotor and the gas reverse flow along the tooth-shaped, tooth side, radial, and circumferential clearances are investigated. A new mathematical model of the pumping flow and backflow involved in a flow balance model is proposed to investigate the actions of the shearing force and pressure difference force. The calculated backflow is verified by comparing the experimental measured results. The relationships of the structural parameters of the screw rotor are established. The effects of the rotor parameters, such as pitch, diameter, and compression ratio, on backflow are revealed. The results show that the rotor diameter and compression ratio remain constant and that the influence of pitch on the backflow is slightly weak, with backflow variations of less than 3%, whereas the pitch, rotor length, and compression ratio are constant and the rotor addendum diameter is directly proportional to the backflow. The addendum diameter of rotor #4 is the largest, and its backflow is about 1.5 times larger than that of rotor #1. When the rotor radial sizes and the pitch of the suction end are constant, the compression ratio is inversely proportional to the backflow in the low-pressure region and proportional to the backflow in the high-pressure regions. Therefore, for a vacuum pump operating in low-pressure areas, the use of the compression ratio of 2.2 or higher is favorable for the reduction in backflow.

Investigation of internal flow and mixing characteristics in dual-orifice atomizers

Dual-orifice atomizers have been developed to overcome the limitations of simplex atomizers—where “simplex” refers to having only a single flow channel—which cannot adjust flow rates over a wide range. This study explores the internal flow and mixing characteristics of dual-orifice atomizers using the Volume of Fluid method. The effects of four key parameters—primary post thickness, primary recess length, secondary swirl number, and mass flow rate ratio—on flow dynamics and atomizer performance, particularly exit film thickness and spray cone angle, are investigated. The results reveal that, before mixing, the low-pressure region created by the swirling flow inside the secondary nozzle increases the primary flow angle and reduces the thickness of the primary liquid film. After mixing, the velocity difference between the primary and secondary flows enhances atomization by promoting greater instability. The impingement position of the primary liquid film is influenced by recess and the low-pressure region inside the secondary nozzle, with longer recess lengths shifting the impingement point upstream. Increases in secondary swirl number, mass flow rate ratio, and primary post thickness further enlarge the low-pressure region, causing the impingement point to move upstream. The mixing regime is defined by the impingement position, with tip mixing creating velocity stratification that increases the instability. The performance of dual-orifice atomizers depends on the impingement position, resulting mixing regime, and secondary flow's swirl intensity. These findings provide valuable insights for optimizing atomizer design to improve performance.

Numerical investigation of pressure measurement by pitot tubes in microscale Taylor–Couette flow with hyper-rotate speed and its correction

As the most classic method in fluid mechanics, pitot tubes have been widely employed to capture gauge pressure. Their effective operation is based on the premise that the measured fluid is ideal, irrotational, and incompressible, and the pitot tubes do not interfere with the measured flow field. However, in microscale Taylor–Couette flow with hyperrotation speed originating from power-to-weight ratio rotating machinery, its correction has never been investigated systematically for the case, in which the scale of the pitot tubes is much larger than the clearance. In this study, the feasibility of using pitot tubes in the measurement of pressure in a microscale Taylor–Couette flow with hyperrotation speed and its correction was considered. First, physical insight into the influence of pitot tubes on shear flow under the scale effect was obtained. The presence of the pitot tubes had less impact on the mean flow field of the shearing flow. In contrast, the sudden expansion induced by the pitot tubes caused additional instability in the shearing flow through the recirculation zone near the connection area. The influence of pitot tubes on the turbulence of the shearing flow is not confined to a local area but extends across the entire clearance between the stator and rotator. Second, the pressure in the clearance cannot fully permeate the cavity where the monitor is located. Therefore, the gauge pressure captured by the pitot tubes is underpredicted in high-pressure while overpredicted in low-pressure regions. The maximum deviation appears near the minimum clearance height. The deviation in the pressure captured by the pitot tubes increases with an increase in the depth and diameter of the pitot tubes, and the influence of the recirculation zone becomes notable. As the clearance height increases, the ratio of the scale in the pitot tubes to the clearance height decreases, degrading the deviation of the pressure captured by the pitot tubes. Within the parametric range studied, the deviation maximum in pressure captured by the pitot tubes is up to 18.5%. Moreover, the pressure captured by the pitot tubes was corrected. The coefficient α, related to the rotational Reynolds number, clearance height, and depth and diameter of the pitot tubes, was deduced. The correction in this study had improved the distribution of pressure, which shows a better agreement.

Ethane Triggered Gate-Opening in a Flexible-Robust Metal-Organic Framework for Ultra-high Purity Ethylene Purification.

Priority recognition separation of inert and larger ethane molecules from high-concentration ethylene mixtures instead of traditional thermodynamic or size sieving strategy is a fundamental challenge. Herein, we report the ethane triggered gate-opening in the flexible-robust metal-organic framework Zn(ad)(min), the 3-methylisonicotinic acid ligand can spin as a flexible gate when adsorbing the cross-section well-matched ethane molecule, thus achieving the unprecedent ethane adsorption capacity (62.6cm3 g-1) and ethane/ethylene uptake ratio (3.34) under low-pressure region (0.1 bar and 298 K). The ethane-induced structural transition behavior is uncovered by a collaboration of single-crystal X-ray diffraction, in-situ variable pressure X-ray diffraction and theoretical calculations, elucidating the synergetic mechanism of cross-section matching and multiple supramolecular interactions within the tailor-made pore channels. Dynamic breakthrough experiments revealed the outstanding separation performance of Zn(ad)(min) in the production of ultra-high purity ethylene (> 99.995%) with a productivity of up to 39.2 L/kg under ambient conditions.

Prediction and evaluation of key parameters in coalbed methane pre-extraction based on transformer and inversion model

Accurate parameter prediction in the coalbed methane (CBM) pre-extraction process is crucial for formulating effective control measures and preventing CBM-related accidents. Traditional prediction methods rely on feature extraction or complex physical model parameter calculations, which require extensive manual intervention and have limited practical applicability. Additionally, simple neural network methods are prone to overfitting and gradient vanishing when handling parameters, and they lack the capability to dynamically monitor gas pressure during extraction, leading to inefficient and blind extraction operations. This study proposes a CBM pre-extraction parameter and completion time prediction method based on the Transformer model. By integrating autoregressive models and wavelet denoising techniques, the approach effectively captures temporal features and long-term dependencies in CBM data. Experimental results demonstrate that the proposed model outperforms traditional methods in short-, medium-, and long-term predictions, with a median R2 value of 0.99072, and 76% of the training results exceeding 0.9. Furthermore, a CBM pressure inversion model was developed, combining dimensional analysis and physical similarity principles with the Transformer model, enabling the dynamic detection of high- and low-pressure regions in coal seams. In single borehole compliance time predictions, the median compliance time for the first stage is 4 days, with an average of 49 days and a maximum of 277 days, providing adjustment guidance for boreholes with extended compliance times. The proposed model significantly improves prediction accuracy and stability, offering critical support for developing scientifically sustainable pre-extraction plans and advancing intelligent CBM management.

Analysis of flow and energy dissipation in pump turbine with small guide vane opening

In this study, a detailed flow state analysis of a reversible pump turbine (RPT) under small guide vane opening conditions was conducted using both numerical simulation and experimental methods on three analysis planes at 0.5 span. The entropy production rate (EPR) in entropy production theory was utilized to visualize the location and magnitude of energy losses in the flow process. The focus was placed on the coherent vortex structures in the volute, stay vane, guide vane, and runner flow path. The results demonstrate that, throughout the runner’s cycle, the leading edge of the guide vane experiences low-pressure regions with uneven pressure distribution within the runner channel. Velocity streamlines reveal flow separation and vortex generation at the typical guide vane trailing edge, with a maximum velocity reaching 49.7. Analysis of radial force and torque on typical guide vanes and the runner indicates that radial force and torque on the guide vanes do not significantly change, with the radial force coefficient CF r−x varying between 0.254 and 1.3. Major energy losses are concentrated behind the trailing edge of the guide vane, primarily in the form of jet wake. Coherent vortex structures are observed in the volute, stay vane, guide vane, and runner flow path, with slight turbulent wake at the trailing edge of the stay vane, clear shedding vortex streets, and vortex build-up in the bladeless area between the guide vane and the runner.

Modulator-Directed Counterintuitive Catenation Control for Crafting Highly Porous and Robust Metal-Organic Frameworks with Record High SO2 Uptake Capacity.

Sulfur dioxide (SO2) is an important industrial feedstock that can be directly utilized or catalytically transformed to value-added chemicals such as sulfuric acid. The development of regenerable porous sorbents for the highly efficient storage and energy-minimal release of toxic SO2 operating under ambient conditions has attracted growing interest. Herein, we report the topology-guided construction of highly porous acs-type metal-organic frameworks (MOFs) through a counterintuitive modulator-directed catenation control approach. In contrast to the conventional modulator facilitated coordination competition that favors the thermodynamic catenated phase, we show that the elevation of modulator concentration can promote the formation of the noncatenated phase probably through a sublattice dissolution pathway. The assembly of a custom-designed trigonal prismatic triptycene-quinoxaline linker and trinuclear Fe3O cluster affords either the threefold catenated SJTU-219 or noncatenated SJTU-220 with desired acs net. Impressively, the synthetic approach is applicable to various metal ions, including Al3+, V3+, and even Ti4+. The noncatenated SJTU-220 exhibits an extraordinary SO2 sorption capacity of 29.6 mmol g-1 at 298 K and 1 bar, surpassing all reported solid sorbents. The uptake capacity can be further raised to 35.6 mmol g-1 via the replacement of Fe3+ with kinetically more inert Cr3+, resulting in a staggering ∼329-fold volume reduction compared with free ideal SO2 gas. Computational simulations suggest that unique Fe3+···S(SO2) interactions dominate the SO2 seeding process, facilitating the efficient packing of SO2 molecules in the large channels. Besides, the exceptionally low uptake at the low pressure region implies global weak framework-SO2 interactions, which offer great potential for practically implementing an "easy-on/easy-off" SO2 delivery system.

Experimental and numerical the effect of cavitation detection on hydraulic performance of the centrifugal pump based on different geometrical configurations

The cavitation phenomena and its experimental evaluation of hydraulic pump performance are the subjects of this study. Both qualitative and quantitative assessments of a pump's flow structure were carried out. The unsteady flow in a pump with various impeller geometry characteristics was investigated numerically. In-depth examinations of the local flow parameters for the static pressure, pump head, vapour volume variation fraction, and pressure fluctuations in the time and frequency domains were conducted. The findings showed that the low-pressure region that closed the impeller eye close to the leading edge of the blade is where the cavitation phenomena takes place. Additionally, the results showed that the blade passing frequency (BPF) and the pump's rotational frequency (RF) are two significant dominant frequencies in the device. Furthermore, the numerical results show that modest cavitation occurred at the design mass flow for Z=3, 4, 5, 6, and 7 impeller blades.

Aerodynamic Performance and Numerical Validation Study of a Scaled-Down and Full-Scale Wind Turbine Models

Understanding the aerodynamic performance of scaled-down models is vital for providing crucial insights into wind energy optimization. In this study, the aerodynamic performance of a scaled-down model (12%) was investigated. This validates the findings of the unsteady aerodynamic experiment (UAE) test sequence H. UAE tests provide information on the configuration and conditions of wind tunnel testing to measure the pressure coefficient distribution on the blade surface and the aerodynamic performance of the wind turbine. The computational simulations used shear stress transport and kinetic energy (SST K-Omega) and transitional shear stress transport (SST) turbulence models, with wind speeds ranging from 5 m/s to 25 m/s for the National Renewable Energy Laboratory (NREL) Phase VI and 4 m/s to 14 m/s for the 12% scaled-down model. The aerodynamic performance of both cases was assessed at representative wind speeds of 7 m/s for low, 10 m/s for medium, and 20 m/s for high flow speeds for NREL Phase VI and 7 m/s for low, 9 m/s medium, and 12 m/s for the scaled-down model. The results of the SST K-Omega and transitional SST models were aligned with experimental test measurement data at low wind speeds. However, the SST K-Omega torque values exhibited a slight deviation. The transitional SST and SST K-Omega models yielded aerodynamic properties that were comparable to those of the 12% scaled-down model. The torque values obtained from the simulation for the full-scale NREL Phase VI and the scaled-down model were 1686.5 Nm and 0.8349 Nm, respectively. Both turbulence models reliably predicted torque and pressure coefficient values that were consistent with the experimental data, considering specific flow regimes. The pressure coefficient was maximum at the leading edge of the wind turbine blade on the windward side and minimum on the leeward side. For the 12% scaled-down model, the flow simulation results bordering the low-pressure region of the blade varied slightly.

Numerical simulations on aerodynamic drag reduction of a 25° Ahmed body by jet flow

In this work, for the aerodynamic characteristics of a 25° Ahmed body, I reduce its aerodynamic drag by adding airflow nozzles at the rear of its model and carrying out computational fluid dynamics simulations and analyses under the flow velocity of the jet port of 10, 20, and 30 m/s respectively, and meanwhile set up the airflow outlets at different locations of the model slope for simulation analyses under the flow velocity of the jet port of 20 m/s. The best up to 16.4% drag reduction rate is achieved in the simulations. The results show that the best drag reduction effect is achieved when the velocity of the jet outlet is 10 m/s. In contrast, the increase in the velocity of the jet outlet will lead to the early separation of the boundary layer, which in turn enhances its aerodynamic drag. As for different airflow outlets, while injecting airflow into the low-pressure region on the slope surface due to the boundary layer separation, moderately moving the jet port downward to enhance the pressure on the front and back of the model can achieve a better drag reduction effect.

Explosion limits of binary mixtures of ammonia and additives (hydrogen, natural gas, and diethyl ether)

This study investigates the explosion limits of ammonia (NH3) and the effect of three different active fuels, hydrogen (H2), natural gas (NG), and diethyl ether (C2H5OC2H5, DEE), on the explosive characteristics of NH3 through comprehensive chemical kinetics analysis. The results reveal that the explosion limits of NH3 exhibit the narrowest explosive range and display comparatively weakest explosive reactivity among the four fuels, presenting a monotonic changing trend. Reaction pathway analysis unveils that with increasing temperature, NH2 tends to oxidize more predominantly through the NH-N2H2-NNH-N2 pathway, while the conversion of NH2 to H2NO pathway decreases. Therefore, the introduction of active fuels significantly enhances the explosive reactivity of NH3. However, their impact under various temperature-pressure conditions presents nuanced and diversified characteristics. When a 0.5 % mole fraction of active fuel is added to NH3, DEE exhibits the most significant enhancement in medium to high-pressure conditions, while H2 predominates at low pressure, with NG consistently demonstrating the least pronounced enhancement. Upon the active fuel proportion being increased to 20 %, the promoting effect of DEE remains the most significant in the medium to high-pressure region, while NG has surpassed H2 as the secondary dominant fuel. In the low-pressure region, NH3-H2 still demonstrates the highest reactivity, followed by NH3-DEE, while NH3-NG exhibits the least reactivity. These findings provide valuable insights into the widespread utilization and scientific exploration of ammonia as a fuel source.

Simulating the Rising Air Bubbles Stream through Heavy Fuel Oil Residue Bubble Column Reactor using COMSOL

Several industrial operations rely on the rise of air bubbles through heavy fuel oil residue (HFOr), including oil recovery and wastewater treatment. In order to increase efficiency and decrease expenses, it is necessary to understand the peculiarities of this process. With the help of COMSOL Multiphysics, we numerically simulate the ascent of a single air bubble via HFOr in this article. The dimensions of the container used in the simulations were (100) mm in diameter and (200) mm in height, with an air bubble diameter of 4.5 mm. For an air bubble ascending through an HFOr column, the predicted numerical outcomes are contrasted with nine experimental versions. As the bubble rose higher, the region with the greatest number of vortices was located on its side. The remaining vortex is contained inside the bubble. In addition, since drag decreases the flow, a lighter fluid usually exhibits a region of strong vortex and low pressure. Because of the oscillation effect, the results reveal that the rising velocity initially rises and then gradually falls between 0.6 and 0.65 s. The air bubbles' wavy motion is caused by the high fluid density, which becomes worse as the air velocity gets higher. The values of the drag coefficient rise sharply with decreasing air extrusion speed. It turns out that the height of the fluid has an inverse relationship with the pressure.

Flame propagation, explosion hazard, and pollutant emission characterization of typical clean fuels leaks in plateau low-pressure region

To accelerate energy transformation and sustainable development, various countries are rushing to lay hydrogen doped natural gas pipelines. However, the installation of pipelines will pass through plateau low-pressure region, and the impact of low-pressure environments on the flame propagation, explosion hazards, and pollutant emission characteristics of hydrogen doped natural gas is not yet clear. To solve this problem, a combination of constant volume combustion experiment and numerical simulations is used. The characterization parameters of flame, explosion and pollutant concentration of natural gas/H2/air under low-pressure environment are obtained, and their chemical reaction kinetics are analyzed. When the pressure drops, the laminar burning velocity (LBV) of them increases, and the Lewis number (Le) gradually increases by more than 1. Thermal diffusion is stronger than mass diffusion, and the growth rate of flame thickness exceeds 26 %. The effect of hydrodynamic instability enhances, causing an increment in the average size of flame cells, the critical instability radius, and the Markstein length (Lu). At the equivalent ratio (φ) of 1, there is a change from negative to positive in the Lu, and flame stability continuously strengthens. The explosion overpressure is reduced by 78 % to 90 %, the explosion temperature by 16 % to 20 %. As the φ increases, the LBV exhibits an inverted U-shaped relationship, reaching its maximum value near “φ = 1″. The flame stability first weakens and then strengthens. The explosion hazard is strongest in the range of ”φ = 1–1.2″. With a decrease in pressure, the total reaction rate of fuel consumption is reduced by more than 50 %. The continuous reaction distance is extended by 12 %. Changes in pressure have a relatively weak impact on the content of CO and CO2. The increase in the φ results in an increase in CO content of over 7 %. The content of CO2 reaches its maximum value around “φ = 1″. It is an essential reference for the safe delivery of hydrogen energy and the reduction of environmental pollution.

Coanda Effect Displayed in a Giant Intracranial Aneurysm.

The Coanda effect is a fluid dynamics phenomenon in which a fluid jet adheres to a convex or flat surface. This effect occurs when a liquid or gas jet emerging from an orifice clings to an adjacent surface and entrains the surrounding fluid, creating a lower-pressure region along its path that maintains its attachment to the surface. The Coanda effect accounts for the behavior of blood flow in the fetal right atrium and the dispersion of eccentric mitral regurgitation jets along atrial walls. This series of interesting images depicting a large 4 × 3.75 cm saccular intracranial aneurysm suggests that the Coanda effect may play a role in the pathophysiology of intracranial aneurysms and could be an underlying factor in their formation, progression, or rupture.

Exploring cavitation dynamics and noise reduction in hydraulic machinery with bionic leading edge impeller

Cavitation and induced noise are common issues in the operation of mixed-flow pumps, affecting their stability. Studying these phenomena is of both academic and engineering interest. Previous research has mainly focused on modifying the impeller blade profile or optimizing the pump structure to reduce cavitation and noise. In this paper, we apply a bionic design to the mixed-flow pump impeller by mimicking the natural shape of a humpback whale's pectoral fin on the leading edge of the blade. We compare the cavitation suppression and noise reduction effects of this design with those of a conventional mixed-flow pump. Unsteady flow calculations for the original pump at different flow rates revealed that at its rated speed, increasing flow rates led to lower pressure in the low-pressure region on the suction surface of the impeller, expanding the cavitation-prone area. By applying the bionic design, we studied the unsteady cavitation flow and its induced noise. Results showed that the impeller and guide vane experienced larger pressure pulsations at the rotation frequency and its multiples. The bionic modification increased the cavitation initiation speed and reduced the cavity volume within the runner. With an NPSH (net positive suction head) of 6.76, the void volume in the bionic pump was only 79% of that in the original pump, and the head increased by 16%. Additionally, the bionic design reduced the maximum far-field sound pressure level by 12.5%, achieving significant noise reduction. This study demonstrates that the bionic design effectively controls dynamic flow separation, reduces flow-induced noise, and enhances the mixed-flow pump's performance. These findings have important theoretical and practical implications for optimizing mixed-flow pump design, improving energy efficiency, and reducing noise.

Numerical investigation of vehicle water entry with angle of attack

This paper investigates the water entry of a vehicle with angle of attack (AOA) through numerical methods, employing the volume-of-fluid multiphase flow model and overset grid technique. The validity of the numerical model is confirmed through experimental verification. Building upon this, the study analyzes the motion characteristics, cavity evolution, and flow field distribution of the vehicle during water entry, considering the influence of AOA and falling velocity. Numerical findings indicate that the collapse of the right side of the cavity induces a transient lateral force on the vehicle, resulting in vehicle tilting. Moreover, an increase in initial velocity delays vehicle tilt, while an increase in AOA reduces vehicle motion stability, leading to earlier tilting. Initially, the vehicle rotates counterclockwise around the Oz axis of the projectile coordinate system. Subsequent to cavity collapse, the vehicle experiences an opposing moment, leading to a reduction in rotation speed and eventual rotation in the opposite direction. Water impact triggers sudden changes in the vehicle's lift and drag coefficients, while cavity sticking induces a minor abrupt change in the lift coefficient. Following cavity collapse, both lift and drag coefficients exhibit significant oscillations. Unlike typical cavity collapse phenomena, the flow field on the right side of the vehicle undergoes alternating high-pressure and low-pressure regions.

Spatial correlations and risk transmission of virtual water flow at city scale: A case study of the Yellow River Basin

By introducing virtual water (VW) flow correlation coefficients and risk indicators, this study examines the VW transmission relationship between urban agglomerations and cities in the Yellow River Basin (YRB) and its impact on regional water resources pressure. The results show that: except for the Shandong Peninsula Urban Agglomeration (SPUA) and Central Plains Urban Agglomeration (CPUA), the other urban agglomerations primarily act as VW exporting regions, while virtual water-importing cities are concentrated in the eastern regions. Notably, the Ningxia Urban Agglomeration (NUA) demonstrates significantly higher values in VW impact and sensitivity coefficients than the remaining six urban agglomerations. First-tier cities generally display lower virtual water impact and sensitivity coefficients, whereas emerging cities exhibit the opposite trend. Additionally, we observe uneven risk variations between VW importing and exporting regions. Taking NUA as an example, the risk increase resulting from VW exports significantly exceeds the risk reduction associated with VW imports in the corresponding regions. It's important to highlight that first-tier cities consistently decrease water resource risk through VW imports in both study years. However, among second and third-tier cities, only 38.9% experience reduced water resource risk through VW imports. Therefore, we recommend a focused examination of VW imports and exports in western region urban agglomerations, cities, and second and third-tier cities within the watershed. Leveraging virtual water's asymmetric and high-value transfer can alleviate water resource pressure and scarcity risks in high-pressure regions by shifting them to lower-pressure regions, thus mitigating water resource stress across regions.

A coordination polymer based on ionic-type ligand for efficient separation of C2H2/C2H4 and C3H4/C3H6 mixtures

C2–C3 alkyne/alkene adsorption and separation is a critical process in industrial production, but it remains challenging due to the similar size of gas molecules. Herein, based on an ionic-type ligand, a porous coordination polymer with inherent positive charged sites has been successfully constructed by 1D chains through non-conventional CH···O hydrogen bonds. The flexible framework shows adsorption ability for C2H2 while negligible adsorption of C2H4; and a much earlier steep increase for C3H4 isotherm compared to C3H6 isotherm in the low-pressure region. Ideal adsorbed solution theory further illustrated that the framework has the ability to separate C2H2/C2H4 and C3H4/C3H6 mixtures.

Analysis on the Influence of Duct Casing Geometry on the Performance of a Ducted Fan

This paper aims to evaluate the influence of an electric ducted fan’s (EDF) geometry on its performance through parameter correlation analysis. Sample data was first built by generating new EDF models with varying duct casing geometries through optimal space-filling (OSF) sampling method. Afterwards, each model was numerically solved with computational fluid dynamics (CFD) analysis to obtain each model’s thrust, required power, and efficiency. It is found that the casing’s inlet lip diameter displays the greatest influence on the EDF’s total thrust, as the inlet diameter determines the casing’s surface area affected by the low-pressure region ahead of the rotating fan blades. Additionally, it is found that length of the casing’s exhaust lip affects the EDF’s efficiency, while the exhaust lip diameter displays the highest correlation with the fan’s required power.

Dynamics of a single cavitation bubble near a cylindrical blind hole

Cavitation bubble dynamics, such as microjets and moving shock waves, are strongly influenced by their surroundings. We investigated the complex bubble behavior during the growth and collapse stages near a blind hole. The simultaneous study, which is a combination of experiment and numerical methods, was performed. The single bubble was induced by a laser focus beam near a blind hole in the cuvette and measured by a high-speed camera with an image processing method. Numerical predictions were conducted for a detailed further investigation of the pressure and velocity fields near and inside the bubble. A fully compressible two-phase Navier-Stokes solver based on the homogeneous flow assumption was used. Both experimental and numerical results showed good agreement with each other. Strong deformation of the bottom bubble surface evolution was observed at low standoffs above the hole entrance. An extremely high-velocity microjet with a mushroom cap-shaped bubble was predicted under high standoffs below the hole entrance. Secondary cavitation in the blind hole was observed experimentally, and we discussed the low-pressure region caused by the interaction among the shock wave, bubble, and blind hole. Consequently, the tendencies of maximum microjet velocity and time-dependent surface pressure in the collapse phase are suggested.