The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
A. A. Candade - One of the best experts on this subject based on the ideXlab platform.
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Horizontal Tailplane-Tip Mounted Tractor Propeller Interaction Effects
2015Co-Authors: A. A. CandadeAbstract:Advanced Propeller propulsion systems potentially provide a significant reduction in fuel burn compared to traditional turbofans. An alternative to the conventional aft-fuselage mounted pusher layout is the horizontal tailplane-tip mounted tractor Propeller concept. The aim of this thesis is an experimental investigation of the aeroacoustic and aerodynamic interaction effects of the tailplane-tip mounted tractor Propeller configuration, including the effects of elevator deflections. The experimental study was conducted at TU Delft’s Low Speed Laboratory in the Vertical Tunnel and the Low Turbulence Tunnel with two different models. From the aeroacoustic study, it was concluded that the installation of the pylon behind the Propeller affects both the directivity and the tonal levels of the Propeller noise field, with the broadband acoustic levels remaining unchanged. It was determined that the overall sound pressure level (SPL) across the range of directivity angles considered is inversely proportional to the Propeller-pylon spacing. For a spacing of 50% Propeller Diameter, the overall SPL was comparable to the case of the isolated Propeller. A unique characteristic of installation of the pylon was the development of a trough in the directivity for an observer position in the pylon plane caused by the cancelling of the steady noise field by unsteady blade loading noise. This arises due to inflow distortion due to potential effects caused by the pylon. This unsteady blade loading is a function of the Propeller-pylon spacing, and hence the levels in the trough decrease with decreasing Propeller-pylon spacing. For directivity angels in the pylon plane, for spacing below 30% of the Propeller Diameter, the unsteady loading is further influenced by the elevator deflection and was the main mechanism of the interaction noise. For Propeller-pylon spacing’s above 30% of the Propeller Diameter, the interaction of the slipstream (either the Propeller noise field, or the slipstream impingement) with the elevator was determined to be the main interaction mechanism. From the PIV and performance evaluations, it was concluded that for the given Propeller-pylon spacing (43% and 85% Propeller Diameter), there was indeed negligible upstream interaction effect due to the trailing pylon, including the case of the deflected elevator Pylon loads obtained from an external balance showed that for symmetric inflow conditions, operation of the thrusting Propeller increased elevator effectiveness by 20% compared to the case with no Propeller present. A numerical simulation using XROTOR was used for the validation of the test data and had a relative error of 3% with the experimentally evaluated Propeller thrust for the lowest advance ratio. A slipstream propagation model based on the computed Propeller induced velocities showed acceptable trends when compared to the experimentally determined induced Propeller velocity profiles. However, the numerical model overpredicts the velocity profile in the tip region, owing to the tool’s limitation in predicting stall at the blade tip. A VLM based numerical analysis which included the effects of the Propeller slipstream, was able to predict the pylon lift to within 3% of the lift computed from the surface pressure measurements, but failed in the prediction of the drag of the model.
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Horizontal Tailplane-Tip Mounted Tractor Propeller Interaction Aspects: An Aerodynamic and Aeroacoustic Experimental Study
Thesis at Delft University of Technology, 2015Co-Authors: A. A. CandadeAbstract:Advanced Propeller propulsion systems potentially provide a significant reduction in fuel burn compared to traditional turbofans. An alternative to the conventional aft-fuselage mounted pusher layout is the horizontal tailplane-tip mounted tractor Propeller concept. The aim of this thesis is an experimental investigation of the aeroacoustic and aerodynamic interaction effects of the tailplane-tip mounted tractor Propeller configuration, including the effects of elevator deflections. The experimental study was conducted at TU Delft’s Low Speed Laboratory in the Vertical Tunnel and the Low Turbulence Tunnel with two different models. From the aeroacoustic study, it was concluded that the installation of the pylon behind the Propeller affects both the directivity and the tonal levels of the Propeller noise field, with the broadband acoustic levels remaining unchanged. It was determined that the overall sound pressure level (SPL) across the range of directivity angles considered is inversely proportional to the Propeller-pylon spacing. For a spacing of 50% Propeller Diameter, the overall SPL was comparable to the case of the isolated Propeller. A unique characteristic of installation of the pylon was the development of a trough in the directivity for an observer position in the pylon plane caused by the cancelling of the steady noise field by unsteady blade loading noise. This arises due to inflow distortion due to potential effects caused by the pylon. This unsteady blade loading is a function of the Propeller-pylon spacing, and hence the levels in the trough decrease with decreasing Propeller-pylon spacing. For directivity angels in the pylon plane, for spacing below 30% of the Propeller Diameter, the unsteady loading is further influenced by the elevator deflection and was the main mechanism of the interaction noise. For Propeller-pylon spacing’s above 30% of the Propeller Diameter, the interaction of the slipstream (either the Propeller noise field, or the slipstream impingement) with the elevator was determined to be the main interaction mechanism. From the PIV and performance evaluations, it was concluded that for the given Propeller-pylon spacing (43% and 85% Propeller Diameter), there was indeed negligible upstream interaction effect due to the trailing pylon, including the case of the deflected elevator Pylon loads obtained from an external balance showed that for symmetric inflow conditions, operation of the thrusting Propeller increased elevator effectiveness by 20% compared to the case with no Propeller present. A numerical simulation using XROTOR was used for the validation of the test data and had a relative error of 3% with the experimentally evaluated Propeller thrust for the lowest advance ratio. A slipstream propagation model based on the computed Propeller induced velocities showed acceptable trends when compared to the experimentally determined induced Propeller velocity profiles. However, the numerical model overpredicts the velocity profile in the tip region, owing to the tool’s limitation in predicting stall at the blade tip. A VLM based numerical analysis which included the effects of the Propeller slipstream, was able to predict the pylon lift to within 3% of the lift computed from the surface pressure measurements, but failed in the prediction of the drag of the model.
Hassan Ghassemi - One of the best experts on this subject based on the ideXlab platform.
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Boundary element method applied to added mass coefficient calculation of the skewed marine Propellers
Polish Maritime Research, 2016Co-Authors: Ehsan Yari, Hassan GhassemiAbstract:Abstract The paper mainly aims to study computation of added mass coefficients for marine Propellers. A three-dimensional boundary element method (BEM) is developed to predict the Propeller added mass and moment of inertia coefficients. Actually, only few experimental data sets are available as the validation reference. Here the method is validated with experimental measurements of the B-series marine Propeller. The behavior of the added mass coefficients predicted based on variation of geometric and flow parameters of the Propeller is calculated and analyzed. BEM is more accurate in obtaining added mass coefficients than other fast numerical methods. All added mass coefficients are nondimensionalized by fluid density, Propeller Diameter, and rotational velocity. The obtained results reveal that the Diameter, expanded area ratio, and thickness have dominant influence on the increase of the added mass coefficients.
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Boundary element method applied to added mass coefficient calculation of the skewed marine Propellers
Polish Maritime Research, 2016Co-Authors: Ehsan Yari, Hassan GhassemiAbstract:© 2016 Ehsan Yari et al., published by De Gruyter Open 2016. The paper mainly aims to study computation of added mass coefficients for marine Propellers. A three-dimensional boundary element method (BEM) is developed to predict the Propeller added mass and moment of inertia coefficients. Actually, only few experimental data sets are available as the validation reference. Here the method is validated with experimental measurements of the B-series marine Propeller. The behavior of the added mass coefficients predicted based on variation of geometric and flow parameters of the Propeller is calculated and analyzed. BEM is more accurate in obtaining added mass coefficients than other fast numerical methods. All added mass coefficients are nondimensionalized by fluid density, Propeller Diameter, and rotational velocity. The obtained results reveal that the Diameter, expanded area ratio, and thickness have dominant influence on the increase of the added mass coefficients.
B G Paik - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the performance characteristics of the flexible Propellers
Ocean Engineering, 2013Co-Authors: B G Paik, Han Shin Seol, Beom-soo Hyun, Young Rae JungAbstract:The objective of the present study is to fabricate three kinds of flexible Propellers and to compare their performance characteristics. The flexibility of the flexible Propeller is strongly dependent on the thrust produced at the blade and the variation in the advance ratio. The largest deflection over 0.03D (D is Propeller Diameter) occurs in the glass/epoxy composite Propeller. The stability of the tip vortex cavitation is inversely proportional to the thrust of the flexible Propeller. The thrust produced by the Propeller's blade reduces the blade's pitch. The wake velocity distributions of the flexible Propellers in the slipstream are considered to be corresponded to their pitch distribution. The relaxation of the contraction of the slipstream is related to the high flexibility of its blade. Acoustic noise is also measured to examine the relation between the blade's flexibility and Propeller-induced noise. The sound pressure level is proportional to the thrust, and it is effectively controlled using a tailoring method.
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Investigation on the performance characteristics of the flexible Propellers
Ocean Engineering, 2013Co-Authors: B G Paik, Han Shin Seol, Gun Do Kim, Beom-soo Hyun, Sang Gab Lee, Kyung Youl Kim, Young Rae JungAbstract:The objective of the present study is to fabricate three kinds of flexible Propellers and to compare their performance characteristics. The flexibility of the flexible Propeller is strongly dependent on the thrust produced at the blade and the variation in the advance ratio. The largest deflection over 0.03D (D is Propeller Diameter) occurs in the glass/epoxy composite Propeller. The stability of the tip vortex cavitation is inversely proportional to the thrust of the flexible Propeller. The thrust produced by the Propeller's blade reduces the blade's pitch. The wake velocity distributions of the flexible Propellers in the slipstream are considered to be corresponded to their pitch distribution. The relaxation of the contraction of the slipstream is related to the high flexibility of its blade. Acoustic noise is also measured to examine the relation between the blade's flexibility and Propeller-induced noise. The sound pressure level is proportional to the thrust, and it is effectively controlled using a tailoring method. ?? 2013 Elsevier Ltd.
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Investigation on the vortex structure of Propeller wake influenced by loading on the blade
Journal of Marine Science and Technology, 2007Co-Authors: B G Paik, Young-ha ParkAbstract:The vortex structure of the wake behind a marine Propeller was investigated in terms of loading variation by using particle image velocimetry. One hundred and fifty instantaneous velocity fields were ensemble averaged to study the spatial evolution of the wake and the behavior of the tip vortices in the region ranging from the trailing edge to one Propeller Diameter downstream. The trailing vorticity was found to be related to the radial velocity jump, and the viscous wake was affected by the boundary layers developed on the blade surfaces. A vortex identification method using the swirling strength was employed to extract the location of the tip vortex. The loading on the blade made a clear difference to the contraction angles. Slipstream contraction occurred in the very near wake region, and unstable oscillation occurred because of reduced interaction between the tip vortex and the wake sheet behind the maximum contraction point for each loading condition. The maximum tangential velocity around the tip vortex center revealed the average radius of its core, which was used for calculating the vortex strength. Additionally, variation of the average radius of tip vortices with the change of blade loading was related to vortex tube stretching in the wake region. The nearly constant vortex strength continued up to one Diameter downstream for light loading and design loading conditions.
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Analysis of wake behind a rotating Propeller using PIV technique in a cavitation tunnel
Ocean Engineering, 2007Co-Authors: B G Paik, Young-ha Park, Kwon-kyu YuAbstract:Abstract A two-frame particle image velocimetry (PIV) technique is used to investigate the wake characteristics behind a marine Propeller with 4 blades at high Reynolds number. For each of 9 different blade phases from 0° to 80°, 150 instantaneous velocity fields are measured. They are ensemble averaged to study the spatial evolution of the Propeller wake in the region ranging from the trailing edge to one Propeller Diameter (D) downstream location. The phase-averaged mean velocity shows that the trailing vorticity is related to radial velocity jump, and the viscous wake is affected by boundary layers developed on the blade surfaces and centrifugal force. Both Galilean decomposition method and vortex identification method using swirling strength calculation are very useful for the study of vortex behaviors in the Propeller wake region. The slipstream contraction occurs in the near-wake region up to about X/D=0.53 downstream. Thereafter, unstable oscillation occurs because of the reduction of interaction between the tip vortex and the wake sheet behind the maximum contraction point.
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three component velocity field measurements of Propeller wake using a stereoscopic piv technique
Experiments in Fluids, 2004Co-Authors: Sang Joon Lee, B G Paik, Jong Hwan Yoon, Choung Mook LeeAbstract:A stereoscopic PIV (Particle Image Velocimetry) technique was used to measure the three-dimensional flow structure of the turbulent wake behind a marine Propeller with five blades. The out-of-plane velocity component was determined using two CCD cameras with an angular displacement configuration. Four hundred instantaneous velocity fields were measured for each of four different blade phases, and ensemble averaged in order to find the spatial evolution of the Propeller wake in the region from the trailing edge up to one Propeller Diameter (D) downstream. The influence of Propeller loading conditions on the wake structure was also investigated by measuring the velocity fields at three advance ratios (J=0.59, 0.72 and 0.88). The phase-averaged velocity fields revealed that a viscous wake formed by the boundary layers developed along the blade surfaces. Tip vortices were generated periodically and the slipstream contracted in the near-wake region. The out-of-plane velocity component and strain rate had large values at the locations of the tip and trailing vortices. As the flow moved downstream, the turbulence intensity, the strength of the tip vortices, and the magnitude of the out-of-plane velocity component at trailing vortices all decreased due to effects such as viscous dissipation, turbulence diffusion, and blade-to-blade interaction.
Ehsan Yari - One of the best experts on this subject based on the ideXlab platform.
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Boundary element method applied to added mass coefficient calculation of the skewed marine Propellers
Polish Maritime Research, 2016Co-Authors: Ehsan Yari, Hassan GhassemiAbstract:Abstract The paper mainly aims to study computation of added mass coefficients for marine Propellers. A three-dimensional boundary element method (BEM) is developed to predict the Propeller added mass and moment of inertia coefficients. Actually, only few experimental data sets are available as the validation reference. Here the method is validated with experimental measurements of the B-series marine Propeller. The behavior of the added mass coefficients predicted based on variation of geometric and flow parameters of the Propeller is calculated and analyzed. BEM is more accurate in obtaining added mass coefficients than other fast numerical methods. All added mass coefficients are nondimensionalized by fluid density, Propeller Diameter, and rotational velocity. The obtained results reveal that the Diameter, expanded area ratio, and thickness have dominant influence on the increase of the added mass coefficients.
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Boundary element method applied to added mass coefficient calculation of the skewed marine Propellers
Polish Maritime Research, 2016Co-Authors: Ehsan Yari, Hassan GhassemiAbstract:© 2016 Ehsan Yari et al., published by De Gruyter Open 2016. The paper mainly aims to study computation of added mass coefficients for marine Propellers. A three-dimensional boundary element method (BEM) is developed to predict the Propeller added mass and moment of inertia coefficients. Actually, only few experimental data sets are available as the validation reference. Here the method is validated with experimental measurements of the B-series marine Propeller. The behavior of the added mass coefficients predicted based on variation of geometric and flow parameters of the Propeller is calculated and analyzed. BEM is more accurate in obtaining added mass coefficients than other fast numerical methods. All added mass coefficients are nondimensionalized by fluid density, Propeller Diameter, and rotational velocity. The obtained results reveal that the Diameter, expanded area ratio, and thickness have dominant influence on the increase of the added mass coefficients.
Young Rae Jung - One of the best experts on this subject based on the ideXlab platform.
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Investigation on the performance characteristics of the flexible Propellers
Ocean Engineering, 2013Co-Authors: B G Paik, Han Shin Seol, Beom-soo Hyun, Young Rae JungAbstract:The objective of the present study is to fabricate three kinds of flexible Propellers and to compare their performance characteristics. The flexibility of the flexible Propeller is strongly dependent on the thrust produced at the blade and the variation in the advance ratio. The largest deflection over 0.03D (D is Propeller Diameter) occurs in the glass/epoxy composite Propeller. The stability of the tip vortex cavitation is inversely proportional to the thrust of the flexible Propeller. The thrust produced by the Propeller's blade reduces the blade's pitch. The wake velocity distributions of the flexible Propellers in the slipstream are considered to be corresponded to their pitch distribution. The relaxation of the contraction of the slipstream is related to the high flexibility of its blade. Acoustic noise is also measured to examine the relation between the blade's flexibility and Propeller-induced noise. The sound pressure level is proportional to the thrust, and it is effectively controlled using a tailoring method.
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Investigation on the performance characteristics of the flexible Propellers
Ocean Engineering, 2013Co-Authors: B G Paik, Han Shin Seol, Gun Do Kim, Beom-soo Hyun, Sang Gab Lee, Kyung Youl Kim, Young Rae JungAbstract:The objective of the present study is to fabricate three kinds of flexible Propellers and to compare their performance characteristics. The flexibility of the flexible Propeller is strongly dependent on the thrust produced at the blade and the variation in the advance ratio. The largest deflection over 0.03D (D is Propeller Diameter) occurs in the glass/epoxy composite Propeller. The stability of the tip vortex cavitation is inversely proportional to the thrust of the flexible Propeller. The thrust produced by the Propeller's blade reduces the blade's pitch. The wake velocity distributions of the flexible Propellers in the slipstream are considered to be corresponded to their pitch distribution. The relaxation of the contraction of the slipstream is related to the high flexibility of its blade. Acoustic noise is also measured to examine the relation between the blade's flexibility and Propeller-induced noise. The sound pressure level is proportional to the thrust, and it is effectively controlled using a tailoring method. ?? 2013 Elsevier Ltd.
