Cavitation Noise Research Articles

Influence of microparticle size on cavitation noise during ultrasonic vibration

The cavitation noise in the ultrasonic vibration system was found to be influenced by the size of microparticles added in water. The SiO2 microparticles with the diameter smaller than 100 μm reduced the cavitation noise, and the reason was attributed to the constrained oscillation of the cavitation bubbles, which were stabilized by the microparticles.

Study of regeneration system of 300 MW power unit based on nondeaerating heat balance diagram at reduced load

More than 30 power units of thermal power stations, based on the nondeaerating heat balance diagram, successfully operate in the former Soviet Union. Most of them are power units with a power of 300 MW, equipped with HTGZ and LMZ turbines. They operate according to a variable electric load curve characterized by deep reductions when undergoing night minimums. Additional extension of the range of power unit adjustment makes it possible to maintain the dispatch load curve and obtain profit for the electric power plant. The objective of this research is to carry out estimated and experimental processing of the operating regimes of the regeneration system of steam-turbine plants within the extended adjustment range and under the conditions when the constraints on the regeneration system and its equipment are removed. Constraints concerning the heat balance diagram that reduce the power unit efficiency when extending the adjustment range have been considered. Test results are presented for the nondeaerating heat balance diagram with the HTGZ turbine. Turbine pump and feed electric pump operation was studied at a power unit load of 120–300 MW. The reliability of feed pump operation is confirmed by a stable vibratory condition and the absence of cavitation noise and vibration at a frequency that characterizes the cavitation condition, as well as by oil temperature maintenance after bearings within normal limits. Cavitation performance of pumps in the studied range of their operation has been determined. Technical solutions are proposed on providing a profitable and stable operation of regeneration systems when extending the range of adjustment of power unit load. A nondeaerating diagram of high-pressure preheater (HPP) condensate discharge to the mixer. A regeneration system has been developed and studied on the operating power unit fitted with a deaeratorless thermal circuit of the system for removing the high-pressure preheater heating steam condensate to the mixer, with extending the range of load adjustment for the 300 MW power unit load.

Flow Field Simulation and Experimental Research on the Triangle Groove Cone Throttle Valve

Aiming at the problems of cavitation noise in the cone throttle valve, triangle groove cone throttle valves with 45, 53, 60 degree were selected as the research objects. Firstly the structure characteristics of the throttle valves were analyzed, then the three-dimensional models and mathematical models were established. By using the finite element simulation software ADINA, the simulation diagrams about pressure and flow velocity of the cone valves were obtained and then verified on the test bench which was about the noise characteristics of throttle valve. The investigation result showed that the flow field of the cone valve was complex, and there were local low pressure areas where were high incidence of cavitation; the valve with 60 degree spool had the minimum noise, which showed the best performance, then the 53 degree spool was a bit poor, and the worst valve was 45 degree spool. Increasing the angles of the triangle groove appropriately could reduce the cavitation noise and improve the performance of the valve. This investigation has great significance on understanding the flow field and controlling the cavitation noise in triangle groove cone throttle valves. Besides it also has a certain reference value to other hydraulic components on the cavitation noise control and structural optimization.

High-intensity focused ultrasound monitoring using harmonic motion imaging for focused ultrasound (HMIFU) under boiling or slow denaturation conditions.

Harmonic motion imaging for focused ultrasound (HMIFU) is a recently developed high-intensity focused ultrasound (HIFU) treatment monitoring method that utilizes an amplitude-modulated therapeutic ultrasound beam to induce an oscillatory radiation force at the HIFU focus and estimates the focal tissue displacement to monitor the HIFU thermal treatment. In this study, the performance of HMIFU under acoustic, thermal, and mechanical effects was investigated. The performance of HMIFU was assessed in ex vivo canine liver specimens (n = 13) under slow denaturation or boiling regimes. A passive cavitation detector (PCD) was used to assess the acoustic cavitation activity, and a bare-wire thermocouple was used to monitor the focal temperature change. During lesioning with slow denaturation, high quality displacements (correlation coefficient above 0.97) were observed under minimum cavitation noise, indicating the tissue initial-softening-then- stiffening property change. During HIFU with boiling, HMIFU monitored a consistent change in lesion-to-background displacement contrast (0.46 ± 0.37) despite the presence of strong cavitation noise due to boiling during lesion formation. Therefore, HMIFU effectively monitored softening-then-stiffening during lesioning under slow denaturation, and detected lesioning under boiling with a distinct change in displacement contrast under boiling in the presence of cavitation. In conclusion, HMIFU was shown under both boiling and slow denaturation regimes to be effective in HIFU monitoring and lesioning identification without being significantly affected by cavitation noise.

Detecting Inception of Hydrodynamic Cavitation Noise of Ships using Quadratic Phase Coupling Index as an Indicator

There is ever increasing interest in underwater noise control onboard ships as part of concerted efforts to reduce ship’s radiated noise. Reduction of radiated noise is considered important as it will affect the performance of hydro-acoustic systems such as sonars, echo sounders, towed systems, etc. Out of three major sources of noise onboard ships, viz., machinery, propeller, and hydrodynamic noise, propeller noise is considered a major source beyond certain speed at which propellers cavitate produces cavitation noise. The inception speed of propeller cavitation is generally accompanied by sudden increase in radiated noise level of 8-15 dB when measured using a hydrophone placed on the seabed. This paper attempts to establish the concept of quadratic phase coupling index as an indicator to detect inception of cavitation of ship propellers. This concept was tested on actual ship radiated noise data measured at sea for evaluating its effectiveness.Defence Science Journal, Vol. 65, No. 1, January 2015, pp.53-62, DOI:http://dx.doi.org/10.14429/dsj.65.7885

The limits of operation modes for apparatuses with cavitation excitation

Cavitation in the chamber of a rotor apparatus with flow modulation was considered. A method was proposed for determining the limits of precavitation and cavitation, cavitation and supercavitation operation modes for apparatuses with pulsed cavitation excitation as a key factor of production process stimulation. The experimental dependence of the critical cavitation number on the excess liquid pressure in the chamber of a rotor apparatus was given and showed an insignificant hysteresis of the critical cavitation number. The dependences of the amplitude of the first cavitation pressure pulse on the generalized cavitation number at different rotor apparatus modulator shuttering rates and temperatures of water (up to 99°C) flowing through one stator hole and of the integrated cavitation noise pressure on the excess liquid pressure (up to 2 MPa) in the chamber of a modified rotor apparatus at constant volumetric flow rates (up to 27 m3/h) were also reported.

エンジンとZ ペラ推進器が船舶の騒音に及ぼす影響及びその低減手法の評価に関する研究

Recently, the reduction of ship noise and underwater radiated noise has become animportant issue. Engines and Z-pellers (azimuth thrusters) are considered as major sources of noise, and a quantitative evaluation of each sound source is required. In this paper, the contributions of engine and Z-peller were evaluated by noise and vibration measurement results in a hybrid tug ship. In order to predict the structure-borne noise level from the engine, an excitation force measurement was performed for both rigid and rubber-mounted engines. Underwater radiated noise emitted from the Z-peller was evaluated from cavitation noise tests using a water tank. In these tests, two types of Zpeller configurations were proposed, and the noise reduction effect was confirmed. Theresults are presented in this paper.

Performance test and analysis of the prototype of the electric motor-pump

An electric motor-pump prototype with compact structure has been developed, and a testing system for the prototype has been established to obtain testing data, such as noise, efficiency, and rotational speed. Compared with the performance of the electric-hydraulic power unit, the noise level of the prototype maximally decreases by 13.4 dB, the volumetric efficiency is nearly 1.3% higher during the delivery pressure rising from 0 MPa to 15 MPa. However, the total efficiency of the prototype is 4.9% lower due to the lower rotational speed and the oil-immersed loss. Aiming at the noise abatement and the decline in efficiency, CFD and Ansoft are used to analyze the suction flow field of main pump and the rotational speed, and then the key factors that impact on noise and efficiency of the prototype are presented. The research results show that adopting the charging effect measure, setting a centrifugal charging pump at the inlet of the main pump, can prevent the cavitation noise caused by insufficient oil suction of the main pump. And the electrical resistance of the squirrel-cage rotor has a great impact on the rotational speed and further impacts on the efficiency. Finally, an improved virtual prototype with improved rotor is presented to increase the total efficiency by 2.4%.

Stationary cavitation bubbles forming on a delta wing vortex

Vortex cavitation forming in the leading-edge vortices of a delta wing was examined to determine how the individual cavitation bubbles incepted, grew, interacted with the underlying vortical flow and produced acoustic tones. The non-cavitating vortical flow over the delta wing was chosen to be similar to those previously reported in the literature. It was found that vortex breakdown was unaffected by the presence of incipient and developed vortex cavitation bubbles in the vortex core. While some cavitation bubbles incepted, grew, and collapsed relatively quickly, others reached an equilibrium position wherein the bubble tip was stationary in the laboratory frame at a particular location along the vortex axis. For a given attack angle, the equilibrium location moved upstream with a reduction in free stream cavitation number. It is shown that the existence of these stationary vortex bubbles is possible when there is a balance between the axial growth of the bubble along the vortex axis and the opposite motion of the axial jetting flow in the vortex core, and only a single equilibrium position is possible along the axially evolving vortex for a given free stream cavitation number. These transient and stationary vortex bubbles emit significant cavitation noise upon inception, growth, and collapse. The spectral content of the noise produced was expected to be related to the interaction of the bubble with the surrounding vortical flow in a manner similar to that reported in previous studies, where sustained tones were similar to the underlying vortex frequency. However, in the present study, the dominant frequency and higher harmonics of the tones occur at a higher frequency than that of the underlying vortex. Hence, it is likely that the highly elongated stationary bubbles have higher-order volume oscillations compared to the two-dimensional radial mode of the vortex cores of vortex cavitation bubbles with much smaller diameter-to-length ratios.

Image-guided sonothrombolysis in a stroke model with a cavitation delivery and monitoring system

Microbubbles (MB) and ultrasound (US) can dissolve intra-arterial thrombi. In order to reproducibly deliver the correct cavitation dose and ensure treatment efficacy and safety, we designed a therapeutic US mode with cavitation monitoring. Therapy delivery and recording of the MB signal are achieved with a sector imaging probe. Monitoring is achieved by spectrally analyzing the MB signal: ultraharmonics are a marker of stable cavitation (SC) and broadband noise characterizes inertial cavitation (IC). We used the system in a pig model. Thrombotic occlusions were created by injecting 4-hour old clots bilaterally into the internal carotids. Forty pigs were randomized to either 2.4 MI, 5 μs pulses with MBs; 1.7 MI, 20 μs pulses with MBs; and 2.4 MI, 5 μs pulses without MBs. Angiographic recanalization rates were compared. Cavitation as a function of MI was estimated in vivo. Dominant SC started at an applied MI of 0.6 (0.3MI in situ after derating by skull attenuation). Dominant IC was estimated to start at an applied MI of 0.9 (0.6 in situ). Thus, all therapy settings were in the IC regime. The 2.4MI + MB setting was the most effective (100% recanalization) vs 38% for the 1.7MI + MB and 50% for 2.4 MI without MBs (both p<0.05 compared to 2.4MI + MB). No signs of hemorrhage were found in any animal. In conclusion, higher IC levels are most effective for thrombus dissolution. Spectral analysis techniques can be used to plan and monitor the therapy.

Cavitation its Use and Mathematical Modelling

The problem of cavitation is highly discussed and published phenomenon not only in a negative sense, but in the positive use also. In hydraulic systems the cavitation is undesirable phenomena specific by cavitation wear and noise. These systems operate at ever-increasing operating conditions (pressure and flow). For this reason, this phenomenon occurs in many technical applications. The problem cavitation is very large, so it is necessary to define the area of scientific interest. Currently, there is an increasing interest in the fields of mathematical and experimental research in hydraulic elements and systems engineering practice. The paper is focused on modelling of shape of cavitation area and influence of air content primarily on the simple geometry of plane nozzle, where the water is flowing.

The evolution of a cavitation zone in a focused ultrasonic field

We have experimentally studied the generation of sonoluminescence (SL) and cavitation noise in the field of a focusing ultrasonic radiator during a gradual smooth increase in the applied voltage. In addition to the SL signal, we have recorded the output signal of a hydrophone situated behind the focal region of the radiator and measured the cavitation-noise spectrum. Four stages in the development of a cavitation zone have been distinguished as manifested by the specific character of dependences of the measured parameters on the voltage applied to the radiator. Spectral signs of the cavitation-noise characteristic of each stage of development of the cavitation zone.

Interactions between poppet vibration and cavitation in relief valve

Poppet vibration and cavitation, two representative phenomena in relief valves, are considered as the roots of the violent noise, erosion, and structure damage. In this paper, the interactions between the poppet vibration characteristics and cavitation property in relief valves with the unconfined poppet are investigated experimentally. Tests have been performed in stable and unstable valves under cavitation and noncavitation conditions. The valve housing is fabricated by Perspex for flow visualization. As for the influence of cavitation on vibration characteristics, it is found that the generated cavitation bubbles in the downstream circuit decrease the flow coefficient and fluid viscosity, and decrease the hydrodynamic spring in turn. The location of cavitating flow, characterized by the low local pressure, changes the thrust on poppet and poppet lift, affecting the radial stiffnesses of mechanical spring and hydrodynamic spring, respectively. On the other hand, as for the influence of vibration on cavitation property, it is found that the poppet vibration leads to a dramatic increase of the noise comparing to the fixed poppet conditions. Spectrum analysis shows that augmented noise in unstable valves mainly comes from the intensification of cavitation noise. A reason for this is that the vibration of poppet leads to a quick and violent collapse of large amount of cavities developed from the throttling region, which should be performed as attached cavities and avoided from collapse in the stable poppet conditions.

Murray Strasberg's contributions to the Navy's ship silencing programs

Murray's long career with the U.S. Navy, extended over seven decades 1942–2012, and began when he joined the David Taylor Model Basin (DTMB), now the Carderock Division of the Naval Surface Warfare Center), in 1942. Soon after joining DTMB he was assigned to making cavitation noise measurements on World War II submarines or with model propellers in water tunnels. This lead to his long standing interest in cavitation and bubble noise, matters to be discussed by others in this session. I will discuss his work in structural acoustics, which grew out of his involvement with a propeller related signature source and ultimately proved to be one of his most significant contributions to the Navy's submarine silencing efforts.

Murray Strasberg—A lifetime dedicated to the Acoustical Society of America

Murray Strasberg received the Gold Medal in 2000 “for contributions to hydroacoustics, acoustic cavitation and cavitation noise, and for dedicated service to the Society” when he was 83 years old. He should have received it much earlier, but the classified nature of his work prevented the preparation of a complete nomination dossier. In addition, most members did not fully realize how much Murray did for the Society as his contributions were spread over a half-century. While serving as President (1974–1975), the Society was faced a critical emergency when Wallace Waterfall, the Society's mainstay and current treasurer passed away. Murray stepped in and worked with others to handle the financial operations of the Society until a new Treasurer was selected. He also served in many other Society roles including Associate Editor of JASA, chair of the committee that set the groundwork for the Congressional Science and Engineering Fellowship Program, and as Secretary from 1987 to 1990. We will share some personal stories about Murray recalled from the many decades working with him as a colleague and wise counsel.

Low-frequency propeller forces and sound—Murray Strasberg's legacy

In the early 1960s, Murray Strasberg, after having already made significant contributions to the field of hydroacoustics in the areas of propeller cavitation noise and general hydrodynamic sources of sound, turned his attention toward low-frequency forces that are generated by propellers, which ingest non-uniform flow. Dr. Strasberg developed an elegantly simplistic approach to estimate the propeller unsteady thrust by actually measuring the sound pressure radiation from a prototype propeller installed in a wind tunnel test section. Murray's approach required that the propeller be acoustically compact, thereby allowing the propeller to be treated as a single dipole sound source. This approach offered by Murray, for which a U.S. patent was awarded in 1982, served as a simpler alternative to the more traditional and complicated approach of force dynamometry. Dr. Strasberg focused his efforts on measuring propeller thrust at the blade passage frequency tonals, but he did, however, encourage Maurice Sevik to perform his seminal propeller turbulence ingestion thrust research in the 1960s and 1970s, which truly ushered in the modern era of propeller turbulence ingestion research that continues today. In this presentation, we will describe Murray Strasberg's novel propeller unsteady thrust measurement approach, and we will discuss how researchers over the years have built upon Murray's foundational concept.

Characteristic correlation between propellers cavitating wake and cavitation noise

The characteristic correlation between the propellers cavitating wake and their cavitation noise has been studied. Based on the viscous multiphase flow theory, the Navier–Stokes equations, a turbulence model and a cavitation model were applied to predict numerically the vapor volume fraction and the pressure in the wake. Compared with experimental results, the numerical predictions of the sheet cavitation and the tip vortex cavitation are in agreement with the corresponding experimental data, which indicates the numerical method in present paper is feasible. The characteristic of the low line spectra of the numerical pressure fluctuation signals and the measured noise signals for uniform inflow and wake flow is analyzed, and the characteristic correlation of the two line spectra is also validated. Therefore, it can be concluded that due to the wake and the radiated noise both modulated by the revolving propeller blades, the features of the low line spectra for noise signals and the pressure signals in the wake are close to each other.

Prototype and Laboratory Low-Level Outlet Air Demand Comparison for Small-to-Medium-Sized Embankment Dams

AbstractLow-level outlet works through dams are typically used to provide irrigation, reservoir sediment flushing, reservoir draw down, and/or minimum downstream flows to meet biological needs. To reduce the likelihood of negative pressure development downstream of the control gate, which may lead to cavitation noise, vibration, and damage, air vents are typically installed downstream of the gate. Undersized air vents may allow vapor pressure and cavitation to occur; oversized air vents have a negative economic impact. Air demand design criteria have been developed for vertical control gates (common to larger dams). The guidance for sizing air vents for an inclined slide gate, which are common for small-to-medium-sized embankment dam geometries, however, is limited. This study compares laboratory-scale and prototype-scale air-demand data. The influences of conduit slope, hydraulic jump presence, and air delivery system geometry on air demand were found to influence air demand. A method for estimating the ...

Design of Choking Cavitator and its Feasibility Study in Wastewater Treatment

A new cavitator-choking cavitator is designed on the basis of analyzing the choking cavitation phenomena that occurs in gas-liquid mixed flow of straight pipe ,in jet pump under operating limits and in steady adiabatic flashing flow of stepped circular tube as well as in a cylindrical pipe with a sharp edged-corner for the steady and unsteady flows. The feasibility preliminary research of choking cavitator is carried out with analysis the signals of cavitation noise and treating simulated wastewater (phenol solution). The results offers a new approach in cavitator development field at home and abroad because of the effect that treating simulated wastewater with choking cavitator is preferable,and the cavitation per energy produced by choking cavitator is higher than that by self-oscillated chamber nozzle.

Boiling detection in a LMFBR using autoregressive models and SVM

This paper deals with acoustic detection of sodium boiling in a Liquid Metal Fast Breeder Reactor (LMFBR) cooled by liquid sodium. As sodium boiling induces acoustic emission, the method consists in real time analysis of acoustic signals measured through wave guides. Auto Regressive (AR) models are estimated on sliding windows and are classified in boiling or non-boiling models using Support Vector Machines (SVM). One of the difficulties to cope with is disturbances due to the influence of some environment noises like the liquid coolant cavitation, vortex flow, shaft vibration and mechanical pump noise. These disturbances can generate false alarms or mask the boiling. The proposed method is designed to be robust toward these disturbances. Furthermore, the SVM are designed to be robust toward the operating mode changing. The application for online monitoring is made on data obtained from French nuclear power plant Phenix and boiling sound signals generated from laboratory experiments. Different acoustic boiling sound levels are used and the effectiveness of the method is shown by the good detection rate and its low false alarm rate even for low acoustic boiling sound level.