Outlet Region Research Articles

Influence of guide vanes on the flow fields and performance of axial pump under unsteady flow conditions: Numerical study

Influence of different guide vanes on structural of flow field and axial pump performance under unsteady flow is carried out using numerical method. A three-dimensional axial flow pump model is numerically simulated using computational fluid dynamics (CFD) method with four number of impeller blades and 3, 4, 5 and 6 guide vanes depend on the SIMPLE code, standard turbulence k-ε model as well as sliding mesh method (SMM). The static, dynamic, total pressures, shear stress, velocity magnitude and turbulent kinetic energy are the important features which affecting instability operation in the pump. By monitoring above parameters and setting different measurement pressure points, the average pressures in the pump are discussed and the effect of guide vanes on the average pressure is analyzed. The results demonstrate that the numerical calculations can provide good accurately prediction for the characteristics of internal flow in the pump. The numerical results are closed to experimental results the minimum errors of pressure differences can reach 2.5% and the maximum errors 6.5%. The guide vanes have more effect on the flow field and pressure variations especially at outlet region in the axial pump. As compared with the using various guide vanes, the pressure increases as number of vanes increase that can lead the performance of pump also increases. Pressure differences in the pump at variety mass flow for vane 6 is higher than other vanes 3, 4 and 5 by 14.13, 11.35 and 3.85% for flow of 5 L/min. Further, the dynamic pressure differences for design flow between different vanes 6, 5, 4 and 3 are about by 2.87, 7.26 and 8.51% respectively.

Is the Whole World Watching? Building a Typology of Protest Coverage on Social Media From Around the World

ABSTRACT Previous research suggests that mainstream media coverage around the world follows a “protest paradigm” that demonizes protesters and marginalizes their causes. Given the recent increase in global protest activity and the growing importance of social media for activism, this paper content analyzes 1,438 protest-related English and Spanish news stories from around the world that were shared on social media, examining framing, sourcing, and marginalizing devices across media outlet type, region, language, and social media platform in order to create a typology of how the protest paradigm operates in an international and social media context. Results showed type of protest, location of protest, and type of media outlet were significantly related to whether news stories adhered to the protest paradigm. Social media shares were predicted by region of media outlet, English-language media, and type of protest.

Microstructure and hydrides in the near rolled-joint regions of ex-service CANDU pressure tube

The regions of CANDU® pressure tubes near the rolled joint (RJ) are the un-supported portions of the inlet and outlet ends just inboard of where the tubes make contact with the 403 stainless steel end fitting sections. Compared to the main body of the pressure tube, in-service conditions are more complex with large gradients in the flux, significant hydrogen isotope concentration profiles and varying operating temperatures. In order to increase the amount of data related to microstructure evolution, the microstructures near rolled-joint regions from an ex-service CANDU pressure tube were investigated. The results show that irradiation-induced effects on the microstructure are more significant than the temperature influence near the inlet rolled-joint region (that operates at lower temperatures). Thermal effects play a more dominant role than the flux near the outlet region (that operates at higher temperatures). Zirconium hydrides aligned in both circumferential and radial directions of the tube have been observed. The zirconium hydrides have an orientation relationship of (0002)αZr//(1¯1¯1)ZrH, and [21¯1¯0]αZr//[011]ZrH with the α-Zr matrix; the hydride phases were identified as gamma (γ) hydride by observing superlattice reflections on the (110) planes in the electron diffraction patterns. The presence of γ hydrides at room temperature in the studied tube may have technical importance because in most of the previous research, δ hydrides were considered as the stable phase that would precipitate during cooling at reactor relevant rates. This assumption has been applied to both delayed hydride cracking (DHC) and fracture toughness experiments and during development of related models. It is critical to elucidate the phases of zirconium hydrides at relevant in-service conditions to enable representative experimental testing and modelling that can be used to verify and/or improve the predictive capability of material evolution and cracking behavior of zirconium alloys in nuclear reactors.

Use of X-ray computed tomography for understanding localised, along-the-channel degradation of polymer electrolyte fuel cells

The need to understand the effects of degradation in polymer electrolyte fuel cells (PEFCs) has led to the development of in-situ and operando imaging studies of failure mechanisms occurring in their constituent materials, but studies using X-ray computed tomography (X-ray CT) for imaging have focussed primarily on a single region of the PEFC flow channel. Whilst studies have shown local variation in degradation rates using electrochemical techniques, this work employs identical-location X-ray CT imaging to elucidate the local degradation of a membrane electrode assembly (MEA) at various locations along-the-channel of a serpentine flow field. Using a carbon corrosion specific accelerated stress test (AST), in-depth analyses of the catalyst layers (CLs) and crack network allow for quantification of the material’s degradation at the inlet, middle and outlet regions of the flow channel on the cathode side. Imaging of the regions was done after 0, 2000 and 5000 cycles and results show significant regional variation in the extent of degradation of the cathode CL. The order of degradation was found to be outlet > middle > inlet, with the outlet CL found to be thinner than the middle and inlet regions, with a greater extent of cracking. Furthermore, additional land and channel degradation effects were probed, with the land regions found to be less degraded than channel regions. This work further highlights the need to understand and develop ASTs that can promote a more uniform degradation rate across an MEA.

Numerical and Experimental Analysis of the Thermal Performances of SiC/Water and Al2O3/Water Nanofluid Inside a Circular Tube with Constant-Increased-PR Twisted Tape

The simultaneous use of two passive methods (twisted tape and a nanofluid) in a heat transfer system will increase the average Nusselt number (Nu) of the system. However, the presence of inserts and nanoparticles inside the tube will create higher pressure drop (ΔP) in the system, which can eventually affect the overall enhancement ratio (η), especially at higher Reynolds numbers (Re). Several modifications of twisted tapes have been made to reduce ΔP, but most showed a decreasing trend of η as Re increased. The objective of this study is to design a new geometry of twisted tape that yields a larger value of Nu and a smaller value of ΔP, which can result in a larger value of η especially at higher Re. A simulation and experimental analysis are conducted in which Re ranges from 4000–16,000 with two types of nanofluids (SiC/Water and Al2O3/Water) at various values of the volume fraction, (φ) (1–3%). ANSYS FLUENT software with the RNG k-ɛ turbulent model is adopted for the simulation analysis. Three types of twisted tape are used in the analysis: classic twisted tape with a pitch ratio of 2 (TT PR2), constant-increasing-pitch-ratio twisted tape (TT IPR) and constant-decreasing-pitch-ratio twisted tape (TT DPR). The use of TT IPR generates a stronger swirling flow at the inlet of the tube and smaller ∆P, especially near the outlet region. The highest value of η is obtained for 3% SiC/Water nanofluid that is flowing through a smooth circular tube with TT IPR inserts at Re of 10,000.

Structure optimization of granular bed filter for industrial flue gas filtration containing coagulative particles: An experimental and numerical study

A numerical model for the flow and filtration characteristics of industrial flue gas in granular bed filter (GBF) was established and the local filtration efficiency for different granule layers was investigated. Numerical validation results show that the GBF structure with large size granules at the inlet region and small size granules at the outlet region can effectively improve the filtration performance of GBF and the underlying mechanism was revealed. Then an experimental system was built to validate the suitability of the optimized GBF structure for the filtration of industrial flue gas with coagulative particles. The experimental results show that the optimized GBF structure is also suitable and its superiority is more significant with the increase of filtration time. The results show that the pressure drop and filtration efficiency of the experimental system increase with the increase of dust particles concentration. The existing of coagulative particles is conducive to the growth of smaller size dust particles, the pressure drop and filtration efficiency increase significantly. In addition, the pressure drop and filtration efficiency decrease with the increase of cooling rate. The results of this study are expected to be useful for the design and optimization of industrial flue gas purification and waste heat recovery.

Diagnostics of nuclear reactor coolant pump in transition process on performance and vortex dynamics under station blackout accident

A mathematical model for the flowrate and rotation speed of RCP during idling was established. The numerical calculation method and dimensionless method were used to analyze the flow, head, torque and pressure and speed changes under idle conditions. Regularity, using the Q criterion vortex identification judgment method combined with surface flow spectrum morphology analysis to diagnose the vortex dynamic characteristics on RCP blade. On impeller blade, there is two oscillations in the pressure ratio on pressure surface in blade outlet region. The velocity on the suction surface is two times more oscillating than the inlet of blade, and there is an intersection with the velocity ratio curve on pressure surface. On blade of guide vane, the pressure ratio increases along the inlet to outlet direction, and the speed ratio decreases with the increase of idle time. There is a vortex that rotates counterclockwise on the suction surface, and the streamline on the suction surface of blade is subjected to the entrainment and blocking action of the vortex creates a large reverse flow in the main flow region. There are two vortices at the outlet of guide vane suction side and the vortices are in opposite directions.

Experimental Investigation of In‐plane Performance Variation on Anode Supported Solid Oxide Fuel Cells Using Segmented Cathodes and Reference Electrodes

AbstractIn this study, planar anode‐supported solid oxide fuel cells (5 × 5 cm2) were fabricated with cathode segmentations and tested in a channel type setup. The in‐plane performance variation became significant with an increasing current density (fuel utilization), and impedance analysis on each segment indicated that the poor performance in the outlet region was due to gas conversion overpotential combined with gas concentration overpotential. Pt reference electrodes were embedded in the electrolyte layers of the segments so that the anode and cathode overpotential could be separated for each segment. It was found that the cathode overpotential was dominant for both segments, which suggested that the cathode overpotential determined the overall cell performance. On the other hand, the anode overpotential was responsible for the in‐plane performance variation. Post‐analysis revealed that the Ni anode was partially oxidized and its layer was delaminated in the outlet region. Thus, this study suggests that the anode overpotential related to gas conversion is a critical factor in determining Ni anode stability as well as overall cell performance in planar anode supported cells with a gas channel setup.

Proof-of-Concept for Gas-Entrapping Membranes Derived from Water-Loving SiO2/Si/SiO2 Wafers for Green Desalination.

Desalination through direct contact membrane distillation (DCMD) exploits water-repellent membranes to robustly separate counterflowing streams of hot and salty seawater from cold and pure water, thus allowing only pure water vapor to pass through. To achieve this feat, commercial DCMD membranes are derived from or coated with water-repellent perfluorocarbons such as polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF). However, the use of perfluorocarbons is limiting due to their high cost, non-biodegradability, and vulnerability to harsh operational conditions. Unveiled here is a new class of membranes referred to as gas-entrapping membranes (GEMs) that can robustly entrap air upon immersion in water. GEMs achieve this function by their microstructure rather than their chemical make-up. This work demonstrates a proof-of-concept for GEMs using intrinsically wetting SiO2/Si/SiO2 wafers as the model system; the contact angle of water on SiO2 is θo ≈ 40°. Silica-GEMs had 300 μm-long cylindrical pores whose diameters at the (2 μm-long) inlet and outlet regions were significantly smaller; this geometrically discontinuous structure, with 90° turns at the inlets and outlets, is known as the "reentrant microtexture". The microfabrication protocol for silica-GEMs entails designing, photolithography, chrome sputtering, and isotropic and anisotropic etching. Despite the water loving nature of silica, water does not intrude silica-GEMs on submersion. In fact, they robustly entrap air underwater and keep it intact even after six weeks (>106 seconds). On the other hand, silica membranes with simple cylindrical pores spontaneously imbibe water (< 1 s). These findings highlight the potential of the GEMs architecture for separation processes. While the choice of SiO2/Si/SiO2 wafers for GEMs is limited to demonstrating the proof-of-concept, it is expected that the protocols and concepts presented here will advance the rational design of scalable GEMs using inexpensive common materials for desalination and beyond.

Dynamic Response of the Fluid Mud to a Tropical Storm

AbstractFluid mud (FM) is a unique sedimentary feature in high‐turbidity estuaries, where it can make a rapid contribution to morphodynamics. Insufficient field measurements and fixed‐point monitoring lead to deficient understandings of the formation, transport, and breakdown of the FM under extreme weather conditions. A field survey was conducted in the Changjiang Estuary during the period of turbidity maximum, just after Typhoon Haikui. The measurements captured the formation of the FM beneath the suspended layers, particularly around the lower reach of the North Passage. The thickness of the observed FM gradually decreased landward along the channel, with the maximum value reaching ~0.9 m. The major features of the observed storm‐induced FM were simulated using the Finite‐Volume Community Ocean Model. The results indicated that the initial appearance of the FM was the result of a typhoon‐intensified, salinity‐induced stratification in the outlet region. The subsequent landward propagation of the FM was driven by the combined effects of the FM‐induced mud surface pressure gradient force and saltwater intrusion near the bottom. Weak mixing during the subsequent neap tidal period sustained the FM as it rapidly extended into the middle region of the North Passage. This produced a large velocity shear at the interface of the FM and upper suspension layer, increasing the entrainment from the FM to the upper suspension layer. As a result of the increased tidal mixing, the FM weakened and then finally broke down in the subsequent spring tidal period.

High-frequency alternating nucleate boiling of water enabled by microslot arrays in microchannels

Flow boiling in parallel and isolated microchannels has been extensively studied. In this study, five parallel microchannels (W = 200 µm, H = 250 µm, L = 10 mm) are interconnected by 28 micro-slots (20 µm wide and 250 µm deep) starting from the outlet. These micro-slots serve as nucleation sites to greatly enhance nucleate boiling. More importantly, the alternating and enhanced nucleate boiling in neighboring microchannels can generate additional pressure drop during the bubble growth-departure cycle and hence enable highly desirable periodic rewetting inside channels, particularly near outlet regions. This new microchannel configuration can substantially enhance nucleate boiling during flow boiling processes. Coupling with the enhanced nucleate boiling and the induced thin film evaporation, heat transfer coefficient (HTC) in present microchannel configuration can be enhanced up to ~107.6% at mass flux 250 kg/m2∙s with a ~17% higher critical heat flux (CHF) compared to the plain-wall microchannels with inlet restrictors (IRs). In addition, we achieve a CHF value of 810 W/cm2 at a moderate mass flux of 430 kg/m2∙s. All these enhancements are realized without compromising two-phase pressure drop compared to plain wall microchannels with inlet restrictors (IRs). Two-phase flow instabilities in terms of temperature and pressure drop fluctuations are also significantly suppressed.

Lubricated steady sliding of a rigid sphere on a soft elastic substrate: hydrodynamic friction in the Hertz limit.

Lubricated sliding on soft elastic substrates occurs in a variety of natural and technological settings. It very often occurs in the iso-viscous elasto-hydrodynamic lubrication (EHL) regime (e.g., soft solid, low pressure). In this regime, for sliding of a smooth sphere on a soft solid, a "Hertz-like" effective contact region forms. Much of the fluid is squeezed out of the contact region although enough is retained to keep the solid surfaces fully separated. This is accompanied by complex deformation of the soft solid. The behavior of such soft lubricated contacts is controlled by a single dimensionless parameter 1/β that can be interpreted as a normalized sliding velocity. Solving this fundamental soft-lubrication problem poses significant computational difficulty for large β, which is the limit relevant for soft solids. As a consequence, little is known about the structure of the flow field under soft lubrication in the intake and outlet regions. Here we present a new solution of this soft lubrication problem focusing on the "Hertz" limit. We develop a formulation in polar coordinates that handles difficult computational issues much better than previous methods. We study how hydrodynamic pressure, film thickness and hydrodynamic friction vary with β. Scaling laws for these relationships are given in closed form for a range of β not previously accessible theoretically but that is typical in applications. The computational method presented here can be used to study other soft lubrication problems.

ГЕОМЕТРИЧНЕ МОДЕЛЮВАННЯ ПРОФІЛЮ ЛОПАТКИ ОСЬОВОГО КОМПРЕСОРА S-ПОДІБНОЇ ФОРМИ

Пропонується метод геометричного моделювання профілю лопатки осьового компресора S-подібної форми, який передбачає розподіл добре відпрацьованого симетричного аеродинамічного профілю вздовж середньої лінії з її перегином у вихідній ділянці модельованого профілю. Середня лінія профілю подається складеною кривою та формується з двох ділянок. Обидві ділянки складеної кривої моделюються у натуральній параметризації, де параметром виступає довжина дуги лінії, а також застосуванні певних законів розподілу кривини. Кривина першої ділянки підпорядковується квадратичній залежності від довжини дуги, друга ділянка моделюється із застосуванням поліноміальної залежності п’ятого степеня. В точці стикування ділянок, розташованій в місці максимального підйому середньої лінії, забезпечується третій порядок гладкості, який передбачає в цій точці рівність значень функцій, її похідних, кривини та похідних від кривини по довжині дуги. Вихідними даними для моделювання середньої лінії виступають координати чотирьох точок, дві з яких знаходяться в початковій та кінцевій точках модельованої кривої, третя точка – в місці максимального підйому середньої лінії, четверта точка – в місці розташування перегину кривої. В початковій та кінцевій точках задаються кути нахилу дотичних, які визначаються в газодинамічному розрахунку осьового компресора та враховують кут установки профілю. В точці максимального підйому лінії кут нахилу дотичної дорівнює нулю. В точці перегину середньої лінії, що надає профілю S-подібність, кут нахилу дотичної не задається, оскільки він визначається в процесі моделювання кривої. Також у процесі моделювання ділянок кривої знаходяться невідомі коефіцієнти залежностей розподілу кривини та довжини дуг. Це реалізується шляхом мінімізації відхилення проміжно отриманих точок від заданих базових точок. На першій ділянці задача мінімізації є однокритеріальною, на другій – двокритеріальною, оскільки модельована лінія має пройти через задану проектантом точку перегину середньої лінії. Саме наявність перегину середньої лінії дозволяє отримувати профілі лопаток осьових компресорів S-подібної форми.

Analysis of the regeneration behavior of high temperature polymer electrolyte membrane fuel cells after hydrogen starvation

Two high temperature polymer exchange membrane fuel cells (HT-PEM FCs) were operated under repeated starvation/regeneration steps for 550 min (DPS-1) and 12 days (DPS-2). Concerning the investigation of the irreversible degradation under fuel (H2) starvation the focus was put on the electrochemical characteristics during regeneration, since during this step the system operates under normal conditions. Electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis were used as electrochemical characterization methods. DRT analysis of selected impedance spectra during regeneration steps for the first seven days revealed an intensity increase of the charge transfer kinetics of the cathode (ca. 10 Hz) and the anode (ca. 100 Hz). From day 3 on, an additional peak at 300–800 Hz appeared likely pointing to the formation of surface oxides at the anode side. The EIS and DRT results were verified with Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM), Microcomputed Tomography (μ-CT) and Transmission Electron Microscopy (TEM). While TEM indicated advanced Pt particle agglomeration pointing to carbon corrosion, μ-CT measurements showed an increase of void volume fraction and a decrease of the tortuosity value. The combined results show that the anode gas outlet region of the FC is more degraded than the inlet region.

LapdMouse: associating lung anatomy with local particle deposition in mice.

To facilitate computational toxicology, we developed an approach for generating high-resolution lung-anatomy and particle-deposition mouse models. Major processing steps of our method include mouse preparation, serial block-face cryomicrotome imaging, and highly automated image analysis for generating three-dimensional (3D) mesh-based models and volume-based models of lung anatomy (airways, lobes, sublobes, and near-acini structures) that are linked to local particle-deposition measurements. Analysis resulted in 34 mouse models covering 4 different mouse strains (B6C3F1: 8, BALB/C: 11, C57Bl/6: 8, and CD-1: 7) as well as both sexes (16 male and 18 female) and different particle sizes [2 μm (n = 15), 1 μm (n = 16), and 0.5 μm (n = 3)]. On average, resulting mouse airway models had 1,616.9 ± 298.1 segments, a centerline length of 597.6 ± 59.8 mm, and 1,968.9 ± 296.3 outlet regions. In addition to 3D geometric lung models, matching detailed relative particle-deposition measurements are provided. All data sets are available online in the lapdMouse archive for download. The presented approach enables linking relative particle deposition to anatomical structures like airways. This will in turn improve the understanding of site-specific airflows and how they affect drug, environmental, or biological aerosol deposition.NEW & NOTEWORTHY Computer simulations of particle deposition in mouse lungs play an important role in computational toxicology. Until now, a limiting factor was the lack of high-resolution mouse lung models and measured local particle-deposition information, which are required for developing accurate modeling approaches (e.g., computational fluid dynamics). With the developed imaging and analysis approach, we address this issue and provide all of the raw and processed data in a publicly accessible repository.

Supercapillary Architecture-Activated Two-Phase Boundary Layer Structures for Highly Stable and Efficient Flow Boiling Heat Transfer.

Development of smaller, faster, and more powerful electronic devices requires effective cooling strategies to efficiently remove ever-greater heat. Phase-change heat transfer such as boiling and evaporation has been widely exploited in various water-energy industries owing to its efficient heat transfer mode. Despite extensive progress, it remains challenging to achieve the physical limit of flow boiling due to highly transitional and chaotic nature of multiphase flows as well as unfavorable boundary layer structures. Herein, a new strategy that promises to approach the physical limit of flow boiling heat transfer is reported. The flow boiling device with multiple channels is characterized with the design of micropinfin fences, which fundamentally transforms the boundary layer structures and imparts significantly higher heat transfer coefficient even at high heat flux conditions, in which boiling heat transfer is usually deteriorated due to the development of dryout starting from outlet regions and severe two-phase flow instabilities. Moreover, the approaching of physical limit is achieved without elevating pressure drop.

Influence of land use and rainfall on the optical properties of dissolved organic matter in a key drinking water reservoir in China

The concentration, source and composition of dissolved organic matter (DOM) in aquatic ecosystems are associated with land use and hydrological connectivity between terrestrial and aquatic systems. However, direct evidence of the effects of rainfall and land use on the variability of DOM in aquatic ecosystems is very limited. In this study, chromophoric DOM (CDOM) absorption and fluorescence spectroscopy were used to elucidate how rainfall and land use affect the variability of CDOM in the watershed of Lake Tianmu, a key drinking water reservoir in the Yangtze River Delta. The mean values of the fluorescence intensity (Fmax) of parallel factor analysis-derived humic-like components (C1, C3, C6) and tryptophan-like components C5 were higher in the southeastern inflowing river mouths than those downstream of the lake outlet regions. The upstream tributaries were mainly dominated by humic-like materials, while the lake was mainly dominated by protein-like materials. The Fmax values of four humic-like components and two tryptophan-like components all increased significantly as the %woodland decreased, but %anthropogenic land use (%cropland+%urban construction area) increased. The Fmax of the humic-like components at the inflowing tributaries and the lake increased with increasing rainfall during storm events, and the value was especially pronounced at the inflowing river mouths. We concluded that land use and hydrological conditions play an important role in influencing the CDOM source and optical composition, and these findings provide insights for the understanding of aquatic ecosystem metabolism and reservoir water quality management.

Lubrication analysis for the piston ring of a two-stroke marine diesel engine taking account of the oil supply

The piston ring is one of the most important parts of a two-stroke marine diesel engine. It is lubricated by a special mode in which the lubricating oil is directly injected into the liner’s inner surface. In this article, taking account of the oil supply, a piston ring lubrication model is developed based on oil mass conservation. The lubrication region of this piston ring–cylinder liner is divided into inlet, core lubrication, and outlet regions, with the oil supply being converted into an oil film. The impact of the width of the core lubrication region on squeezing of the oil is considered. To verify the model, friction force measurements are performed in a reciprocating bench test under fully flooded conditions, and the model is further validated by comparing the minimum oil film thickness with data from the literature. The model is applied to the top ring of a two-stroke marine diesel engine, and the impacts of the oil supply and its design parameters are analyzed.

Design of a hot air discharge channel for temperature control of the electronic chips on printed circuit boards

Depending on the increase in speed and performance requirements of electronic devices, the temperature of electronic chips on printed circuit boards increase, which can lead to damage. There are many experimental and numerical studies involving different cooling methods for cooling electronic devices. In this study, discharge of rising hot air from the system with a channel by utilizing pressure difference in airflow was analyzed numerically. At the cases with and without discharge channel, numerical analyses were carried out for different Reynolds numbers (Re), different angles of the circuit boards (α), and different ratios of narrowing of the air outlet region (h/W). Numerical results revealed that the use of hot air discharge channel was more effective by the increasing pressure difference in the airflow and placing of the printed circuit boards horizontally, at the conditions that the natural convection predominated. As a result of using hot air discharge channel, the highest average percentage of the temperature drops on the third and fourth heater rows were obtained 11% and 17% for the narrowing ratio of h/W = 0.4. Findings were presented in detail with the graphs involving temperature variations in the electronic chips and pressure drop between the air inlet and outlet zones depending on the different parameter values.

Unsteady flow characteristics and cavitation prediction in the double-suction centrifugal pump using a novel approach

The recent advances in centrifugal pump design do not only require a better suction performance but also there have been attempts to reduce design time at a lower cost. The traditional trial-and-error optimization design method, however, depends on the designer's experience, which requires longer cycles. This is because the computational process of calculating the net positive suction head required (NPSHr) involves several calculation steps and this consumes a lot of computational time. An investigation was therefore carried out to test a novel NPSHr prediction method in a double-suction centrifugal pump using unsteady numerical simulations. In the new approach, a new boundary pair was introduced and an algorithm was used to estimate a good value for a static pressure value that correlates to a 3% drop in pump head to determine the critical cavitation point. Experiments were conducted to validate the hydraulic performance and the cavitation model. The NPSHr and the characteristic “sudden” head-drop were very well predicted by the novel approach in only three simulation steps. The internal flow analysis showed that for 0.6 Q d, the flow around the volute tongue was uneven at NPSH = 10.06 m, inducing flow separation and recirculation at the tongue region. Attached cavities were also observed around the suction ring in the spiral suction domain. The pressure fluctuations were analyzed also and the dominant frequency at the pump outlet and tongue region was the blade passing frequency. Consequently, the novel approach proved very robust and efficient in NPSHr prediction and would be a good alternative to shorten simulation time during cavitation optimization design process in centrifugal pumps.