The Experts below are selected from a list of 21018 Experts worldwide ranked by ideXlab platform

P A Andne - One of the best experts on this subject based on the ideXlab platform.

  • Nucleation effects on hydrofoil tip vortex Cavitation
    Australasian Fluid Mechanics Society, 2018
    Co-Authors: Khoo M, J A Venning, Pearce W, P A Andne
    Abstract:

    Tip vortex Cavitation inception about an elliptical planform,NACA 0012 hydrofoil is investigated in Cavitation Tunnel flowsin which Cavitation nuclei are deplete and abundant. Tests wereconducted at fixed Reynolds and Cavitation numbers. The onset, or inception, of Cavitation was induced by increasing theangle of incidence and behaviour was recorded photographically and acoustically. Cavitation inception occurred at a higherincidence in the deplete case compared with the abundant dueto fewer weaker nuclei. It also occurred within a small incidence change for the deplete case, with the appearance of acontinuous, cavitating vortical flow structure. Whereas for theabundant case, inception was intermittent, occurring across alarger incidence range. This was associated with individual nuclei activation events increasing in frequency with increasingincidence. Sound pressure levels increased with inception andcavity development but reduced to a local minimum once thecavity attached to the hydrofoil, increasing thereafter with incidence. Overall sound levels were higher for the abundant casethan for the deplete case

  • artificial thickening and thinning of Cavitation Tunnel boundary layers
    Experimental Thermal and Fluid Science, 2016
    Co-Authors: A Elle, P A Andne, W Pearce, K L De Graaf, D Clarke
    Abstract:

    Measurements of natural, thickened and thinned boundary layer mean velocity profiles on the ceiling of a Cavitation Tunnel test section are presented. The method of thickening investigated is via an array of transverse injected jets and for thinning via ingestion of the natural boundary layer fluid through a perforated plate. Several jet arrays of different geometric configuration and open area were tested over a range of jet to freestream velocity ratios, Reynolds numbers and Cavitation numbers. The thickened and thinned velocity profiles are compared with the laws of the wall and wake using parameters derived from the natural boundary layer profiles. The most significant parameter controlling the degree of thickening is the open area, as predicted by one-dimensional mass and momentum conservation, with improvements achievable depending on the jet array configuration. Of the configurations tested an array of intermediately spaced jets was found more effective for thickening than a single row or either sparsely or closely spaced arrays. The profiles of all configurations were found to compare favourably with the laws of the wall and wake to varying degrees, depending upon the geometry, jet velocity and the streamwise length in terms of the number of boundary layer thicknesses for profile development. The results showed that boundary layers could be artificially thickened from momentum Reynolds numbers of about 30,000 to values of about 100,000, or friction Reynolds numbers from about 10,000 to 35,000. Jet velocity was shown to have a significant effect on Cavitation inception and generated noise, demonstrating this must be minimised to optimise Cavitation limits. Overall the results suggest that a jet array of large open area, to increase thickness and minimise the jet to freestream velocity ratio, with jets distributed with sufficient spacing to promote mixing provides an idealised configuration.

  • complementary cfd study of generic submarine model tests in a Cavitation Tunnel
    20th Australasian Fluid Mechanics Conference (20AFMC), 2016
    Co-Authors: C L Ellis, D Utle, D Clarke, P A Andne
    Abstract:

    Experimental and computational studies were conducted on the widely studied SUBOFF submarine model enabling the benchmarking of the Australian Maritime College (AMC) Cavitation Tunnel for submarine model testing. This paper describes the Computational Fluid Dynamics (CFD) used in conjunction with the SUBOFF experiments in this study. The CFD was used to determine blockage corrections and to provide insight into the development of flow structures that are observed in the wake measurements. The blockage correction was determined using computational domains representative of the test environment and an additional enlarged domain with a low blockage ratio. The simulations of the submarine hull in the former compared well with the uncorrected test measurements. This high level of agreement provides confidence in using the results from the simulations to correct for blockage. These corrections allow the results obtained in the AMC Cavitation Tunnel to be compared with results obtained in other test facilities (e.g. the David Taylor Research Centre); which showed a high level of agreement.

  • hydrodynamic measurements on the joubert hull in the amc Cavitation Tunnel with cfd determined blockage corrections
    20th Australasian Fluid Mechanics Conference (20AFMC), 2016
    Co-Authors: D Clarke, C L Ellis, D Utle, P A Andne
    Abstract:

    The Joubert generic submarine geometry and its derivatives are currently the subject of computational studies in over six countries interested in comparing simulation techniques for diesel electric submarine hulls. This paper presents the second set of flow measurements at comparable and higher Reynolds numbers to the existing available measurement set. This new data set allows increased confidence in the use of the Joubert generic submarine geometry for Computational Fluid Dynamic (CFD) studies. Measurements were taken in the Australian Maritime College’s (AMC) Cavitation Tunnel on the hull of a 1:52 scale generic bare hull Joubert submarine model, oriented at zero degrees incidence. Surface pressure and skin friction measurements were collected at a range of Reynolds numbers. Boundary layer velocity and turbulence intensity surveys were performed at a number of positions aft of the hull. A wake survey was taken at the propeller plane for the bare hull with, and without, the aft control surfaces. The hull’s cross sectional area created an 8.5% solid blockage ratio in the test section. Blockage corrections were performed using CFD simulations of the bare hull as mounted within the test section and additionally in a low blockage domain. The results from these two CFD domains were used to provide full field blockage corrections to the measurements.

  • hydroacoustic characterisation of the amc Cavitation Tunnel
    Acoustics 2013 Victor Harbor: Science Technology and Amenity, 2013
    Co-Authors: Co J Doola, P A Andne, D Utle, W Pearce, Danielle J Moreau, Laura A Ooks
    Abstract:

    This paper presents recent results from an Industry-University-Defence collaborative project whose aim is to characterise the hydroacoustic environment of the Australian Maritime College Cavitation Tunnel. After summarising the operation of the Tunnel, a methodology for measuring and processing the hydroacoustic measurements is presented that includes a technique for reducing the level of turbulent wall pressure fluctuations on the hydrophone measurement. The background noise levels of the Tunnel are presented for a variety of operating conditions and they compare favourably with other hydroacoustic test faciltities internationally.

D Clarke - One of the best experts on this subject based on the ideXlab platform.

  • artificial thickening and thinning of Cavitation Tunnel boundary layers
    Experimental Thermal and Fluid Science, 2016
    Co-Authors: A Elle, P A Andne, W Pearce, K L De Graaf, D Clarke
    Abstract:

    Measurements of natural, thickened and thinned boundary layer mean velocity profiles on the ceiling of a Cavitation Tunnel test section are presented. The method of thickening investigated is via an array of transverse injected jets and for thinning via ingestion of the natural boundary layer fluid through a perforated plate. Several jet arrays of different geometric configuration and open area were tested over a range of jet to freestream velocity ratios, Reynolds numbers and Cavitation numbers. The thickened and thinned velocity profiles are compared with the laws of the wall and wake using parameters derived from the natural boundary layer profiles. The most significant parameter controlling the degree of thickening is the open area, as predicted by one-dimensional mass and momentum conservation, with improvements achievable depending on the jet array configuration. Of the configurations tested an array of intermediately spaced jets was found more effective for thickening than a single row or either sparsely or closely spaced arrays. The profiles of all configurations were found to compare favourably with the laws of the wall and wake to varying degrees, depending upon the geometry, jet velocity and the streamwise length in terms of the number of boundary layer thicknesses for profile development. The results showed that boundary layers could be artificially thickened from momentum Reynolds numbers of about 30,000 to values of about 100,000, or friction Reynolds numbers from about 10,000 to 35,000. Jet velocity was shown to have a significant effect on Cavitation inception and generated noise, demonstrating this must be minimised to optimise Cavitation limits. Overall the results suggest that a jet array of large open area, to increase thickness and minimise the jet to freestream velocity ratio, with jets distributed with sufficient spacing to promote mixing provides an idealised configuration.

  • complementary cfd study of generic submarine model tests in a Cavitation Tunnel
    20th Australasian Fluid Mechanics Conference (20AFMC), 2016
    Co-Authors: C L Ellis, D Utle, D Clarke, P A Andne
    Abstract:

    Experimental and computational studies were conducted on the widely studied SUBOFF submarine model enabling the benchmarking of the Australian Maritime College (AMC) Cavitation Tunnel for submarine model testing. This paper describes the Computational Fluid Dynamics (CFD) used in conjunction with the SUBOFF experiments in this study. The CFD was used to determine blockage corrections and to provide insight into the development of flow structures that are observed in the wake measurements. The blockage correction was determined using computational domains representative of the test environment and an additional enlarged domain with a low blockage ratio. The simulations of the submarine hull in the former compared well with the uncorrected test measurements. This high level of agreement provides confidence in using the results from the simulations to correct for blockage. These corrections allow the results obtained in the AMC Cavitation Tunnel to be compared with results obtained in other test facilities (e.g. the David Taylor Research Centre); which showed a high level of agreement.

  • hydrodynamic measurements on the joubert hull in the amc Cavitation Tunnel with cfd determined blockage corrections
    20th Australasian Fluid Mechanics Conference (20AFMC), 2016
    Co-Authors: D Clarke, C L Ellis, D Utle, P A Andne
    Abstract:

    The Joubert generic submarine geometry and its derivatives are currently the subject of computational studies in over six countries interested in comparing simulation techniques for diesel electric submarine hulls. This paper presents the second set of flow measurements at comparable and higher Reynolds numbers to the existing available measurement set. This new data set allows increased confidence in the use of the Joubert generic submarine geometry for Computational Fluid Dynamic (CFD) studies. Measurements were taken in the Australian Maritime College’s (AMC) Cavitation Tunnel on the hull of a 1:52 scale generic bare hull Joubert submarine model, oriented at zero degrees incidence. Surface pressure and skin friction measurements were collected at a range of Reynolds numbers. Boundary layer velocity and turbulence intensity surveys were performed at a number of positions aft of the hull. A wake survey was taken at the propeller plane for the bare hull with, and without, the aft control surfaces. The hull’s cross sectional area created an 8.5% solid blockage ratio in the test section. Blockage corrections were performed using CFD simulations of the bare hull as mounted within the test section and additionally in a low blockage domain. The results from these two CFD domains were used to provide full field blockage corrections to the measurements.

  • development of capabilities for Cavitation Tunnel investigation of transitional flows about underwater bodies
    Pacific 2006 International Maritime Conference, 2006
    Co-Authors: D Clarke, P A Andne, G J Walke
    Abstract:

    This paper provides an overview of the equipment developed and the techniques implemented so boundary layer behaviour may be examined within the Australian Maritime College Cavitation Tunnel. This work was conducted as part of a larger project to understand the flow about Unmanned Underwater Vehicles. A summary of some results for flow about a prolate spheroid is provided and discussed. These tests for the spheroid were conducted at Reynolds Numbers of 1 10{6} to 4 10{6}.

G J Walke - One of the best experts on this subject based on the ideXlab platform.

  • the influence of viscous effects and physical scale on Cavitation Tunnel contraction performance
    Journal of Fluids Engineering-transactions of The Asme, 2008
    Co-Authors: P A Andne, J L Roberts, G J Walke
    Abstract:

    The general performance of an asymmetric Cavitation Tunnel contraction is investigated using computational fluid dynamics (CFD) including the effects of fluid viscosity and physical scale. The horizontal and vertical profiles of the contraction geometry were chosen from a family of four-term sixth-order polynomials based on results from a CFD analysis and a consideration of the wall curvature distribution and its anticipated influence on boundary layer behavior. Inviscid and viscous CFD analyses were performed. The viscous predictions were validated against boundary layer measurements on existing full-scale Cavitation Tunnel test section ceiling and floor and for the chosen contraction geometry against model-scale wind Tunnel tests. The viscous analysis showed the displacement effect of boundary layers to have a fairing effect on the contraction profile that reduced the magnitude of local pressure extrema at the entrance and exit. The maximum pressure gradients and minimum achievable test section Cavitation numbers predicted by the viscous analysis are correspondingly less than those predicted by the inviscid analysis. The prediction of Cavitation onset is discussed in detail. The minimum Cavitation number is shown to be a function of the Froude number based on the test section velocity and height that incorporate the effects of physical scale on Cavitation Tunnel performance.

  • design considerations in the development of a modern Cavitation Tunnel
    16th Australasian Fluid Mechanics Conference (AFMC), 2007
    Co-Authors: P A Andne, Y Lecoffre, G J Walke
    Abstract:

    The specification and overall design of the new Australian Maritime College Cavitation Tunnel is presented. This facility has been funded under the Australian Government Major National Research Facilities Program as part of the Australian Maritime Hydrodynamics Research Centre (AMHRC). The AMHRC is a joint venture between the Australian Maritime College, the Defence Science and Technology Organisation and the University of Tasmania. The facility has been developed for naval hydrodynamics research with particular emphasis on the modelling of cavitating and turbulent flow physics. Development of circuit architecture and components are discussed in detail as well as ancillary systems. The facility’s specific capabilities include the ability to strictly control circuit water gas content (both dissolved and free), continuous high-volume injection and separation of incondensable gases, control of the boundary layer on one wall of the test section, and low background noise and vibration levels.

  • development of capabilities for Cavitation Tunnel investigation of transitional flows about underwater bodies
    Pacific 2006 International Maritime Conference, 2006
    Co-Authors: D Clarke, P A Andne, G J Walke
    Abstract:

    This paper provides an overview of the equipment developed and the techniques implemented so boundary layer behaviour may be examined within the Australian Maritime College Cavitation Tunnel. This work was conducted as part of a larger project to understand the flow about Unmanned Underwater Vehicles. A summary of some results for flow about a prolate spheroid is provided and discussed. These tests for the spheroid were conducted at Reynolds Numbers of 1 10{6} to 4 10{6}.

  • a waterjet test loop for the tom fink Cavitation Tunnel
    Proceedings of the International Conference Waterjet Propulsion III Royal Institution of Naval Architects RINA Gothenburg Sweden paper: P2001-2 Procee, 2001
    Co-Authors: P A Andne, G J Walke
    Abstract:

    The Tom Fink Cavitation Tunnel and waterjet test loop are described. New and developing techniques for improved investigation of viscous and Cavitation phenomena in waterjet flows are discussed. Consideration is given to testing at high Reynolds numbers, hull boundary layer simulation and water quality as related to Cavitation testing. A range of instrumentation and possible measurements, for investigation of waterjet inlet flows, are presented.

Gundo Kim - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Analysis of Unsteady Cavitating Vortex around Two-dimensional Wedge-shaped Submerged Body
    The Korean Society of Ocean Engineers, 2018
    Co-Authors: Ji-hye Kim, So-wo Jeong, Chul-soo Park, Gundo Kim
    Abstract:

    Unlike a slender body, vortices are shed off alternately in the wake of a blunt body. In the case of liquid flows, when the pressure falls below the vapor pressure, Cavitation occurs in the vortex core and affects the formation of the vortex street. This phenomenon is of major importance in many practical cases because the alternate shedding of vortices creates imbalanced forces on the body. Hence, it is very important to determine the shedding frequency of cavitating vortices. In this paper, the unsteady cavitating flow around a two-dimensional wedge-shaped submerged body was simulated using the commercial code STAR-CCM+. A numerical investigation of the structure of cavitating vortices was performed for a model with an apex angle of 20°. The results were validated by comparing them with experimental measurements carried out at a Cavitation Tunnel of Chungnam National University (CNU-CT). It was found that the shedding frequency of the vortex increased by up to 18%, which was strongly affected by the development of Cavitation

  • noise localization method for model tests in a large Cavitation Tunnel using a hydrophone array
    Remote Sensing, 2016
    Co-Authors: Cheolsoo Park, Young Ha Park, Gundo Kim, Keunhwa Lee, Woojae Seong
    Abstract:

    Model tests are performed in order to predict the noise level of a full ship and to control its noise signature. Localizing noise sources in the model test is therefore an important research subject along with measuring noise levels. In this paper, a noise localization method using a hydrophone array in a large Cavitation Tunnel is presented. The 45-channel hydrophone array was designed using a global optimization technique for noise measurement. A set of noise experiments was performed in the KRISO (Korea Research Institute of Ships & Ocean Engineering) large Cavitation Tunnel using scaled models, including a ship with a single propeller, a ship with twin propellers and an underwater vehicle. The incoherent broadband processors defined based on the Bartlett and the minimum variance (MV) processors were applied to the measured data. The results of data analysis and localization are presented in the paper. Finally, it is shown that the mechanical noise, as well as the propeller noise can be successfully localized using the proposed localization method.

  • performance trial test of the full scale driving pump for the large Cavitation Tunnel lct
    Journal of The Society of Naval Architects of Korea, 2015
    Co-Authors: Gundo Kim, Kisup Kim, Young Ha Park
    Abstract:

    The objective of the present study is to analyze the results of the trial-test for the full-scale driving pump, which is arranged in the LCT (Large Cavitation Tunnel). Firstly, the reasons of selecting the final design pump are introduced in terms of the performance analysis in model tests. The trial-test items for the full-scale driving pump are measurements of output current/voltage at the inverter of the main motor and the flow velocity in the LCT test section. The test results show the increase in flow rate of about 10.7% and the decrease in pump head of about 26%, compared with those of final design-pump specification. The motor power has the margin of about 22%. The performance analysis for the full-scale pump is conducted using the commercial code (CFX-10). The delivered power calculated with CFX-10 shows good agreement with that extracted from the full-scale pump test. It is found that CFX-10 is useful to analyze a full-scale pump.

  • a study on hydrophone array design optimization for Cavitation Tunnel noise measurements
    The Journal of the Acoustical Society of Korea, 2013
    Co-Authors: Cheolsoo Park, Hanshi Seol, Gundo Kim, Young Ha Park
    Abstract:

    This paper proposes a hydrophone array design optimization technique for Cavitation Tunnel noise measurements. The optimization technique comprises of design parameters, an objective function and an optimization algorithm. The design parameters are defined for circular, spiral and multi-spiral arrays. The objective function is defined so as to consider the mainlobe beamwidth and the maximum sidelobe level simultaneously. A global optimization scheme is applied to the array design using very fast simulated reannealing (VFSR). After applying the optimization technique to arrays respectively, the peak sidelobe level and the mainlobe beamwidth of optimum arrays are analyzed. Finally the array patterns considering multiple reflections in the Cavitation Tunnel are evaluated to validate the proposed method.

  • development of the driving pump for the low noise large Cavitation Tunnel
    Journal of The Society of Naval Architects of Korea, 2008
    Co-Authors: Gundo Kim, Kisup Kim, Jintae Lee, Hanshi Seol
    Abstract:

    AbstractIt is reported to develop the driving pump for the Low Noise La rge Cavitation Tunnel(LOCAT) which is under construction at Maritime & Ocean E ngineering Research Institute(MOERI). For low background noise condition of the LO CAT, it is crucial not only the best pump efficiency but also no cavity occurrence at any operating conditions. Design condition of the pump is determined by considering the required pump headrise, flow quantity, shaft rotation velocity and pump diameter. Performanc e analysis of the pump is conducted using commercial CFD codes (BladeGen + , CFX-10), and the predicted results are verified by a series of model tests. Cavity was not observe d at any operating condition in the model test, which were conducted at the midium Cavitation Tunnel of MOERI. The optimum pump for LOCAT, named as LP-11, was successfully developed through a series of pump design processes composed of blade design, perfo rmance analysis and model test. ※Keywords: Driving pump(구동펌프), Low noise(저소음), Cavitation(캐비테이션), Required headrise(요구양정)

W M J Atte - One of the best experts on this subject based on the ideXlab platform.

  • power and thrust measurements of marine current turbines under various hydrodynamic flow conditions in a Cavitation Tunnel and a towing tank
    Renewable Energy, 2007
    Co-Authors: A S Ahaj, A F Molland, J R Chapli, W M J Atte
    Abstract:

    The results of Cavitation Tunnel and tank tests on an 800mm diameter model of a marine current turbine (MCT) are presented. The tests were carried out in a 2.4m×1.2m Cavitation Tunnel and the 60m towing tank. Results for power and thrust coefficients are presented for a range of tip speed ratio and pitch settings for various conditions. The results of this investigation provided an insight into the operation of a singe turbine in straight or yawed flow, the effect on performance of changes in the tip immersion of the rotor, the interference between twin rotors and the likely areas of Cavitation inception. In addition, the analysed results presented provide useful information for the hydrodynamic design of MCTs and detailed data for the validation of numerical models.