Stage Of Cavitation Research Articles

Synergistic effects of biological stimuli and flexion induce microcavities promote hypertrophy and inhibit chondrogenesis during in vitro culture of human mesenchymal stem cell aggregates.

Interzone/cavitation are key steps in early stage joint formation that have not been successfully developed in vitro. Further, current models of endochondral ossification, an important step in early bone formation, lack key morphology morphological structures such as microcavities found during development in vivo. This is possibly due to the lack of appropriate strategies for incorporating chemical and mechanical stimuli that are thought to be involved in joint development. We designed a bioreactor system and investigated the synergic effect of chemical stimuli (chondrogenesis-inducing [CIM] and hypertrophy-inducing medium [HIM]) and mechanical stimuli (flexion) on the growth of human mesenchymal stem cells (hMSCs) based linear aggregates under different conditions over 4 weeks of perfusion culture. Computational studies were used to evaluate tissue stress qualitatively. After harvesting, both Safranin-O and hematoxylin & eosin (H&E) staining histology demonstrated microcavity structures and void structures in the region of higher stresses for tissue aggregates cultured only in HIM under flexion. In comparison to either HIM treatment or flexion only, increased glycosaminoglycan (GAG) content in the extracellular matrix (ECM) at this region indicates the morphological change resembles the early stage of joint cavitation; while decreased type II collagen (Col II), and increased type X collagen (Col X) and vascular endothelial growth factor (VEGF) with a clear boundary in the staining section indicates it resembles the early stage of ossification. Further, cell alignment analysis indicated that cells were mostly oriented toward the direction of flexion in high-stress region only in HIM under flexion, resembling cell morphology in both joint cavitation and hypertrophic cartilage in growth plate. Collectively, our results suggest that flexion and HIM inhibit chondrogenesis and promote hypertrophy and development of microcavities that resemble the early stage of joint cavitation and endochondral ossification. We believe the tissue model described in this work can be used to develop in vitro models of joint tissue for applications such as pathophysiology and drug discovery.

Investigations on cavitation flow and vorticity transport in a jet pump cavitation reactor with variable area ratios

Hydrodynamic cavitation (HC) has emerged as a promising technology for water disinfection. Interestingly, when subjected to specific cavitation pressures, jet pump cavitation reactors (JPCRs) exhibit effective water treatment capabilities. This study investigated the cavitation flow and vorticty transport in a JPCR with various area ratios by utilizing computational fluid dynamics. The results reveal that cavitation is more likely to occur within the JPCR as the area ratio becomes smaller. While as the area ratio decreases, the limit flow ratio also decreases, leading to a reduced operational range for the JPCR. During the cavitation inception stage, only a few bubbles with limited travel distances are generated at the throat inlet. A stable cavitation layer developed between the throat and downstream wall during the limited cavitation stage. In this phase, the primary flow carried the bubbles towards the outlet. In addition, it was found that the vortex stretching, compression expansion, and baroclinic torque terms primarily influence the vorticity transport equation in this context. This work may provide a reference value to the design of JPCRs for water treatment.

Investigation on formation mechanism of cavitation channel vortex in the runner of Francis turbine

Abstract Cavitation channel vortices generally cause flow state more complex in the runner, leading to the work efficiency is reduced and the cavitation erosion on flow components is enhanced. In this paper, simulation of cavitation flow is carried out for a Francis turbine model, and the evolution of vortices in the runner during cavitation development is analyzed under partial load conditions. The results show that cavitation has a great influence on the morphology and distribution of attached vortices between blades, trailing vortices at the outlet edge of the blades, and vortex near the cone in the runner. With the gradual development of cavitation, the invasion effect of vortex rope in draft tube on the runner is enhanced, and the vortex near runner cone is gradually connected as a whole. Under the effect of the downstream reverse pressure gradient in local low-pressure area, the flow separation area gradually expands to the blade and upstream, and more singular points evolve on flow separation lines, which leads to more trailing vortices at the outlet of the blade and cavitation channel vortices are formed in serious cavitation stage.

Numerical Simulation of Unsteady Cavitation at the Tongue of a Centrifugal Pump

Abstract The flow separation at the tongue of the centrifugal pump will cause a sharp reduction of local pressure, thus inducing the cavitation phenomenon, which hurts the stable operation of the pump. This article focuses on the centrifugal pump as the research object. The Delayed Detached Eddy Simulation (DDES) method based on the SST turbulence model was employed to numerically simulate the cavitation at the tongue of the centrifugal pump. The typical characteristics and unsteady changes of cavitation were observed and studied, and the pressure at the tongue position was monitored for flow rates of 1.36 Q 0 and 1.54 Q 0. The results show that, in the cloud cavitation stage, the area of the cavitation bubble presents periodic changes, the main frequency of the cavitation area pulsation is twice the axial frequency, the periodic shedding of the cavitation bubble is caused by the attached vortex (re-entrant jet) and the pressure gradient, and the wall attached vortex will periodically shed and break. The high intensity vortices generated by flow separation at the tongue will change periodically with the rotation of the blade. With the increase of inlet flow, the pressure pulsation at the tongue increases, and the shedding and collapse of the cavitation bubble will enhance the pressure pulsation.

Research on the Internal Flow Difference between Peak and Valley Conditions of Water Jet Propulsion Pump during Working at Hump Region

When we tested the water jet propulsion pump, we found that there were significant vibrations in the pump, especially at small flow points that deviated from the design conditions. The water jet propulsion pump is a mixed-flow pump with guide vane, which is commonly employed for water jet propulsion. However, the guide vane mixed-flow pump is susceptible to a phenomenon known as “hump”, which can cause flow disturbances, increased vibration, and noise when the pump operates within the hump region. According to the vibration phenomenon found in our experiment, the mechanism of vibration needs to be revealed. This study focuses on vorticity and turbulence distributions of a mixed flow water jet propulsion pump under the valley and peak operating conditions of the hump region. The research is conducted using experimental and numerical simulation methods. The SST k-ω turbulence model is employed for turbulence calculations. The experiments are conducted on a closed test rig for axial (mixed) flow pumps. A comparison of experimental and numerical simulation results of hydraulic performance curves are conducted to validate the accuracy of the numerical simulation. Cavitation flow structures of the critical cavitation stage under valley conditions and under peak conditions are compared. A comparative analysis is conducted to examine the differences in internal vortex core distribution and turbulence kinetic energy distribution between the valley and peak operating conditions when working within the hump region. The pressure and velocity vectors of the pump impeller blades and the velocity streamline distribution between the impeller and the guide vane blades are compared. To further analyze the flow state in different flow channels under valley and peak conditions, the streamline distribution at Span = 0.5 in the impeller and diffuser basin is extracted. This study provides theoretical foundations and technical support for the design of high-performance, low-vibration water jet propulsion pumps.

Evaluation of the Cavitation Fluid Characteristics of the Bullet across the Medium into the Water at Different Velocities

This paper studies the evolution and fluid distribution characteristics of a high-speed projectile’s cavity in the water based on joint research, a method involving experiment and numerical simulation. Specifically, we develop an experimental platform and a numerical calculation model for a high-speed projectile to observe its initial cavity evolution characteristics in the water at different velocities and close ranges. Additionally, this work investigates the evolution mechanism of the cavitation process and its fluid distribution law inside the cavity and studies the evolution characteristics of the cavitation stage under different velocities. The results reveal that after the projectile enters the water, the cavity is gourd-shaped and symmetrical, with a necking phenomenon at the tail and the cavity falling off. The cavitation process can be divided into the surface closure, saturation, deep closure, and collapse stages according to the fluid distribution changes in the cavity. Suppose the projectile has a certain speed with the water, its velocity increases. In that case, the cavity generation rate decreases, the growth rate of the water vapor volume in the cavity decreases, the peak water vapor volume content reduces, and the volume of air in the saturation phase of the cavity becomes increases having a range of 6% to 9%. Additionally, the cavity surface closure dimensionless time grows logarithmically as the velocity changes from 0 m/s to 500 m/s, the cavity saturation dimensionless time decreases approximately linearly, and the cavity depth closure dimensionless time is unaffected by velocity changes.

Mixed-flow pump cavitation characteristics extraction based on power spectrum density through pressure pulsation signal analysis

Mixed-flow pump is an important machine for transporting fluids, which has the advantages of both centrifugal pump and axial flow pump, but it is prone to cavitation, endangering efficiency and safe operation. A 20 m × 8.5 m high-precision hydraulic mechanical stand and a vertical mixed-flow pumping station device were built for the study of cavitation signals. The detection of pressure pulsation signal is a direct measurement of the cavitation region, and the decay of information is less. In this study, the time domain and frequency domain characteristics of water pressure pulsation signal are analyzed by using fast Fourier transform method. The power spectrum density (PSD) is used to extract the characteristics of each cavitation stage, especially the full cavitation stage with random signal characteristics. The results show that PSD method reflects more information and is more sensitive than traditional time–frequency domain analysis. The characteristic power spectrum (PS) value of the cavitation of the mixed-flow pump machinery can be given through the feature extraction of the PS, which plays a great role in the effective identification and prevention of cavitation.

Human Embryo Live Imaging Reveals Nuclear DNA Shedding During Blastocyst Expansion and Biopsy

ABSTRACT The proportion of babies born from in vitro fertilization (IVF) is rising at an exponential rate, highlighting the importance that we have a comprehensive understanding of human preimplantation development and determinants of embryo quality. The early divisions of the embryo after fertilization but before implantation and resulting mitotic errors have been studied primarily in the mouse embryo; however, thus far we have lacked the technology to characterize these critical steps in humans. Establishing an approach that can bypass genetic manipulation and microinjections of DNA or mRNA into human embryos would allow us to better uncover the processes patterning preimplantation human development. This study aimed to evaluate human blastocyst preimplantation development with noninvasive imaging using membrane permeable fluorescent dyes. First, the dyes SPY650-DNA, which labels genomic DNA, and SPY555-actin, which labels F-actin, were validated in the mouse embryo where they produced high contrast labelling with similar results to microinjection of fluorescent mRNAs and produced offspring at a similar rate to nondyed control embryos. Live imaging data using these dyes enabled 3-dimensional scans of the embryo at 5- to 10-minute intervals of the following central events during preimplantation development: the main phases of mitosis, visualizing the major changes in cell shape that characterize embryo compaction at the 8-cell stage, detecting cell polarization at the 8-cell stage, establishing apical F-actin rings at the 16-cell stage, tracking the expansion and zippering of F-actin rings, detecting the first internalized cells within the 16-cell embryo, and visualizing blastocyst expansion and hatching from the zona pellucida. Cleavage-stage human IVF embryos were then studied using the fluorescent dyes to track early cellular and morphogenetic processes. Early cell-cycle dynamics and mitotic stages revealed that the duration of human mitosis is similar to that of mice, but interphase is 27% ± 4% longer in humans (16.1 ± 0.9 vs 12.7 ± 0.4 hours; P < 0.01). Using live imaging, compaction dynamics such as increased cell-cell contact and angle between apical membranes with a decrease in cell sphericity were observed beginning at the 12-cell stage and differed significantly from development in mice. In comparison to mice, human compaction was found to be more asynchronous and did not have clear links to apical polarization or inner-outer segregation. Next, chromosomal segregation was analyzed to determine if this approach allowed detection of segregation errors in the human embryo leading to aneuploidy. Lagging chromosomes detected in human embryos using SPY-DNA appeared morphologically similar to those found in mouse embryos and had similar segregation dynamics. During blastocyst expansion, a subset of trophectoderm cell nuclei forms protruding bud-like that is shed into cytoplasm producing cytoplasmic DNA structures (cytDNA), suggesting an additional process of DNA loss different from chromosome segregation errors during mitosis. A perinuclear keratin network developing at the early cavitation stage appears to protect from formation of cytDNA structures, and the mechanical stress of blastocyst expansion appeared to disrupt the keratin network in certain cells, increasing DNA shedding. Next, trophectoderm biopsy was conducted in mouse, and human embryos to determine if the mechanical stress would increase DNA shedding. Biopsy of human blastocysts resulted in a significant increase in nuclear budding (6.0% vs 0.70%; P = 0.0022), suggesting a link between mechanical stress and DNA shedding. This study demonstrates the use of fluorescent dyes and live imaging in characterization of key cellular and morphogenetic processes patterning the preimplantation human embryo and describes a process of DNA shedding in response to mechanical stressors that warrants future research.

Study on noise induced by cavitation flow in orifice plates

In water supply pipelines, the installation of multiple orifice plates as throttling components can lead to significant noise generation, caused by the cavitation flow downstream, which in turn, can negatively impact the stealth performance of ships and human health. This study aims to investigate the noise reduction characteristics of orifice plates used for throttling. For this purpose, a test rig was established to measure the noise generated by cavitation flow through orifice plates with varying porosity rates, along with the corresponding pressure losses. Additionally, Large Eddy Simulation (LES) and the Zwart-Gerber-Belamri (ZGB) cavitation model were used to numerically simulate the cavitation flow through orifice plates with a porosity rate of β = 0.4. The results show that the pressure loss coefficient is approximately inversely proportional to the porosity rate and follows a power function with the Reynolds number, with the exponent closely related to the porosity rate. During the cavitation stage, the sound pressure level significantly increases in the high-frequency range of 500–8000 Hz, exhibiting broad-spectrum characteristics. During the initial cavitation, bubbles are mainly confined to the surface of the orifice wall. Nevertheless, under conditions of intense cavitation, the generation of bubbles in the shear layer and trail-flowing region is induced by vortex cavitation. Moreover, cavities form at the intersection of the jet and shear layer, which extend towards the orifice plate. To optimize the noise reduction performance of orifice plate throttling components, it is advisable to maintain the porosity rate within the range of 0.40–0.49.

Near-Wall Cavitation Effect: A Molecular Dynamics Study.

Cavitation has been the subject of abundant studies, but the internal mechanism of cavitation is less well known. In this article, a microlevel near-wall model was established by using LAMMPS to present the process of cavitation effect. The results of molecular dynamics simulation revealed the fluctuation process of the liquid near the wall with the change in pressure. Molecular dynamics was also used to evaluate the void volume fraction and density distribution of the system. The results exhibited that the cavitation process can be divided into two stages: the initial cavitation stage and the rapid growth stage. Based on these results, the effects of wettability and initial system temperature on the near-wall cavitation effect were demonstrated. The results indicated that the hydrophobic near-wall forms a gas layer to weaken the density fluctuation, while the hydrophilic wall is opposite. Increasing the temperature could positively affect molecular motion and cavitation. This work provides a theoretical basis for further exploration of the cavitation effect.

Bubble size distribution at early stage of hydrodynamic cloud cavitation

The bubble size distribution (BSD) in hydrodynamic cloud cavitation is poorly understood, in spite of its importance in cavitation erosion and noise. Challenges arise owing to the heterogeneous turbulent flows and high void fraction in the cavitation regime. The use of a fiber optical probe enables us to obtain the BSD in a cavitation cloud. Two distinct power law scalings at the early stage of cloud cavitation are identified. The first generation of bubbles is produced by the fission to the shedding cavitation pocket by large-scale turbulence, whose isotropic part leads to the basic scaling −10/3, while the anisotropic part due to the effect of hydrofoil wall contributes to the deviation. The successive fragmentation of bubbles accompanied with turbulent energy cascade results in the fairly uniform scaling −4/3. The results indicate that turbulence plays a dominant role in bubble breakup at the early stage of cloud cavitation.

Study on pressure pulsations and transient fluid forces in centrifugal pump under different degrees of cavitation

At the early stage of cavitation, the external characteristics and vibration noise of centrifugal pump have not changed significantly, but the flow conditions in the pump have changed markedly. In order to carry out in-depth study on the change characteristics of the flow conditions in centrifugal pump under different degrees of cavitation at the early stage of cavitation, in this paper, the quantitative relation between cavitation degree and pressure pulsation and fluid force was established by means of numerical calculation combined with test and by analyzing the changes in pressure pulsations and fluid forces in the pump under different degrees of cavitation degree. Studies have shown that the pressure pulsation amplitude and range value at the main frequency (shaft frequency and blade frequency) increases with the cavitation degree. The RMS value of pressure pulsation in each frequency band is positively correlated with cavitation development. In case of severe cavitation, the pressure pulsations in high frequency bands are greatly affected by cavitation. The radial force on pump volute and impeller fluctuates more significantly with the increase of cavitation degree.

Cavitation state recognition for control valve using AlexNet-type neural networks with three-channel images transformed by time series

The control valve is a crucial component with high switching frequency in coal liquefaction systems. Its performance exerts a great influence on the long-term operations in the coal chemical technology. Cavitation is a key factor affecting the control accuracy and surface morphology of the control valve; hence, it will further shorten the service life of the control valve. A cavitation state recognition model based on vibration acceleration time series is proposed in this paper, and the cavitation stage in the valve is identified accurately. Three vibration acceleration sensors are attached to the valve seat to measure cavitation-induced vibration data. The collected time series is divided into fragments based on the non-overlap moving window method, and these fragments are converted into feature maps using the Gramian angular field transform. These feature maps are then input into AlexNet to train the cavitation state recognition model. The experimental results show that recognition accuracy could be improved effectively upon the increase in the length of the time series fragment, and the proposed model has a similar prediction accuracy on unfamiliar datasets. Compared with no noise, the recognition accuracy could reach to 95% when the moving window length is 150 and the signal-to-noise ratio is equal to 5 dB. Furthermore, the proposed model could still achieve good recognition results under mixed open conditions.

Investigation of pressure pulsation induced by quasi-steady cavitation in a centrifugal pump

To study the pressure pulsations induced by quasi-steady cavitation in a centrifugal pump, the pressure pulsations at the pump inlet and outlet were experimentally investigated with the development of cavitation. Moreover, the internal flow characteristics in the pump during the process were numerically determined. The numerical simulation results agreed well with the results obtained from the experimental test, verifying the accuracy of the numerical simulation. Furthermore, the cavitation-induced pump inlet and outlet pressure pulsations of the centrifugal pump were analyzed by wavelet analysis and fast Fourier transform, and the cavitation incipient point and occurrence of the unstable cavitation point were obtained. The results of both wavelet analysis and fast Fourier transform show that in the quasi-steady cavitation stage of the centrifugal pump at the design flow rate, the pump inlet and outlet pressure pulsations are significantly increased at twice the axial frequency, while the other axial frequency components are weak and the internal flow is stable. With the development of cavitation in the pump, the pump inlet and outlet pressure pulsations at the axial frequency and its multiples afford some obvious broadband pulsations. To investigate the mechanism of quasi-steady cavitation-induced pressure pulsation in the centrifugal pump, the dynamic mode decomposition was used for internal flow field analysis. The results show that different inflow states lead to obvious differences in the internal flow and unsteady flow structures. There are complex pressure pulsation characteristics dominated by different frequencies in the centrifugal pump. Blade passing frequency plays an important role in the entire flow field, and its mechanism has been analyzed. This research will provide experimental and theoretical support for quasi-steady cavitation recognition and help researchers improve the operation stability of the centrifugal pump.

Surface cavitation flow characterization of jet hydrofoils based on vortex identification method

The vortex structure is a typically coherent structure. The influence of hydrofoil jets with different chordal positions on the vortex structure in the hydrofoil flow field is investigated to improve the suppression mechanism of cavitation by jet hydrofoils. The investigation is based on a vortex identification method and the chordal position with the best suppression effect on the large-scale vortex on the hydrofoil surface is explored. In addition, the dynamics of the vortex structure in different cavitation states are analyzed by means of vortex transport equations based on the optimal chordwise position. The results show that the U-shaped vortex is the main morphology of the hydrofoil surface bubble shedding; the results show that the U-shaped vortex is the main form of cavitation shedding on the hydrofoil surface; compared with the original hydrofoil and other jet positions, the shedding of large-scale vortex structure can be suppressed better when the jet is located at 0.6c; the dominant vorticity transport terms are different in various cavitation stages. In the primary cavitation stage, the vorticity dilatation term is dominant. In contrast, during the development, maturation, and shedding phases, the vortex stretching term dominates, reducing the pressure gradient in the hydrofoil flow field and suppressing the strength of the return jet.

Study on external performance and internal flow characteristics in a centrifugal pump under different degrees of cavitation

Cavitation as a form of unsteady flow within centrifugal pumps can cause the reduced performance of pumps, disordered internal flow regimes, and flow loss. The present criterion used for determining the occurrence of cavitation is a 3% head drop. However, in most cases, pump cavitation already occurs with less than a 1%–2% head drop due to significant changes in the internal flow status. To examine changing patterns in internal flow characteristics as the degree of cavitation deepens in the early stage of cavitation in centrifugal pumps when the head curve does not show significant fluctuation, this paper focuses on a low specific speed centrifugal pump to analyze distributions of total internal pressure, speed, bubble volume, vortex structure, and entropy generation across different degrees of cavitation and obtain internal flow characteristics and flow loss patterns of pumps, with an aim of providing preferences for anti-cavitation hydraulic design of centrifugal pumps.

Stage-Specific L-Proline Uptake by Amino Acid Transporter Slc6a19/B0AT1 Is Required for Optimal Preimplantation Embryo Development in Mice.

L-proline (Pro) has previously been shown to support normal development of mouse embryos. Recently we have shown that Pro improves subsequent embryo development when added to fertilisation medium during in vitro fertilisation of mouse oocytes. The mechanisms by which Pro improves embryo development are still being elucidated but likely involve signalling pathways that have been observed in Pro-mediated differentiation of mouse embryonic stem cells. In this study, we show that B0AT1, a neutral amino acid transporter that accepts Pro, is expressed in mouse preimplantation embryos, along with the accessory protein ACE2. B0AT1 knockout (Slc6a19-/-) mice have decreased fertility, in terms of litter size and preimplantation embryo development in vitro. In embryos from wild-type (WT) mice, excess unlabelled Pro inhibited radiolabelled Pro uptake in oocytes and 4-8-cell stage embryos. Radiolabelled Pro uptake was reduced in 4-8-cell stage embryos, but not in oocytes, from Slc6a19-/- mice compared to those from WT mice. Other B0AT1 substrates, such as alanine and leucine, reduced uptake of Pro in WT but not in B0AT1 knockout embryos. Addition of Pro to culture medium improved embryo development. In WT embryos, Pro increased development to the cavitation stage (on day 4); whereas in B0AT1 knockout embryos Pro improved development to the 5-8-cell (day 3) and blastocyst stages (day 6) but not at cavitation (day 4), suggesting B0AT1 is the main contributor to Pro uptake on day 4 of development. Our results highlight transporter redundancy in the preimplantation embryo.

Orientation-induced anisotropy of plasticity and damage behavior in monocrystalline tantalum under shock compression

In this work, the role of crystallographic orientation on dynamic mechanical response in single-crystalline tantalum subjected to impact loading is investigated using non-equilibrium molecular dynamics simulations. Interestingly, the correlation of spall strength with void distribution is characterized statistically. Moreover, it is discovered that the entanglement of dislocation lines plays an important role in void nucleation, and then high dislocation density is beneficial to the increase in potential void nucleation sites. Oppositely, the movement of dislocation lines is deteriorated by voids, and then the dislocation density within the spall region dramatically drops after void nucleation in each orientation. There is a strong sensitivity of dislocation line evolution to void growth and coalescence in the later stage of cavitation. For [100], fewer potential void nucleation sites are found to occur in narrower spall zone, and then the existing voids are easier to be aggregated. Consequently, dislocation lines cannot be absorbed by surrounding voids. In contrast, the void distribution area is wider enough to facilitate to annihilate more dislocation lines through voids in [110]. Particularly, the decrease of dislocation density is inclined to the fact that the space for dislocation line survival is preoccupied by void nucleation sites along the [111] direction.

Study on Distribution Law of Gas Phase and Cavitation in the Pressurization Unit of Helical Axial Flow Multiphase Pump

Due to the irregular change of gas void fraction (GVF) in multiphase pumps, the pressure distribution in the pump is often uneven, which leads to the formation of low-pressure area and thus the occurrence of cavitation. In order to study the gas phase and cavitation distribution in the impeller region of a multiphase pump under different cavitation stages and GVF conditions, this study used numerical calculations as the main method and experimental verification as a secondary method to investigate the cavitation phenomenon in the pump under different stages and GVF conditions. The results showed that at different stages, both the volume fraction and the covering area of the gas phase were reduced to a certain extent with the increase in blade height, and the distribution law of the gas phase on the blade changed with the development of the cavitation stage, especially on the blade surface. At different GVFs, cavitation first occurred at the inlet of the blade SS and then extended along the blade streamline from the inlet to outlet, with the volume fraction and distribution of cavitation gradually increasing and then extending to the blade PS. The results showed that the presence of the gas phase inhibited the development of cavitation in the multiphase pump to some extent, and the cavitation performance of the multiphase pump was better in the presence of the gas phase than in pure water conditions. The results of this study provide a theoretical basis for improving the cavitation performance of multiphase pumps.

Experimental investigation of cavitation-induced noise and vibration in a centrifugal pump

Cavitation has become a serious concern threatening operational stability as the need for high-speed machinery has grown. In this study, noise (sound pressure level) and vibrations (structural) were measured in a radial flow centrifugal pump for design and off-design conditions under cavitation. Because the structure of a particular noise/vibration spectrum (as well as its total level) is affected by the operating conditions and stage of cavitation within the pump, a detailed analysis the noise/vibration spectra during the pumping process was carried out to detect of the cavitation phenomenon's progression. We aim to identify the association between noise/vibration and the corresponding net positive suction head value at different flow rates. The results showed that the cavitation structure affects the vibration/noise behavior of the pump. Moreover, total noise level measurements at partial flow rates cannot be used to diagnose full cavitation breakdown, whereas total noise level measurements can be used to detect cavitation intensity at higher flow rates than the optimum operating point.