Noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence
Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous...
Ausführliche Beschreibung
Gespeichert in:
| Autor*in: |
Alexander, W. Nathan [verfasserIn] |
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| Format: |
E-Artikel |
|---|---|
| Sprache: |
Englisch |
| Erschienen: |
2017transfer abstract |
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| Schlagwörter: |
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| Umfang: |
14 |
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| Übergeordnetes Werk: |
Enthalten in: Cancer of the uterus and treatment of incontinence (CUTI) - Robison, K.M. ELSEVIER, 2015, London |
|---|---|
| Übergeordnetes Werk: |
volume:409 ; year:2017 ; day:24 ; month:11 ; pages:227-240 ; extent:14 |
| Links: |
|---|
| DOI / URN: |
10.1016/j.jsv.2017.07.056 |
|---|
| Katalog-ID: |
ELV036138126 |
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| 245 | 1 | 0 | |a Noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence |
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| 520 | |a Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. | ||
| 520 | |a Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. | ||
| 650 | 7 | |a Turbulence ingestion |2 Elsevier | |
| 650 | 7 | |a Haystacking |2 Elsevier | |
| 650 | 7 | |a Boundary layer ingestion |2 Elsevier | |
| 700 | 1 | |a Devenport, William J. |4 oth | |
| 700 | 1 | |a Glegg, Stewart A.L. |4 oth | |
| 773 | 0 | 8 | |i Enthalten in |n Academic Press |a Robison, K.M. ELSEVIER |t Cancer of the uterus and treatment of incontinence (CUTI) |d 2015 |g London |w (DE-627)ELV012704822 |
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2017 |
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10.1016/j.jsv.2017.07.056 doi GBVA2017020000002.pica (DE-627)ELV036138126 (ELSEVIER)S0022-460X(17)30589-8 DE-627 ger DE-627 rakwb eng 530 530 DE-600 610 VZ 610 VZ 44.11 bkl Alexander, W. Nathan verfasserin aut Noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence 2017transfer abstract 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Turbulence ingestion Elsevier Haystacking Elsevier Boundary layer ingestion Elsevier Devenport, William J. oth Glegg, Stewart A.L. oth Enthalten in Academic Press Robison, K.M. ELSEVIER Cancer of the uterus and treatment of incontinence (CUTI) 2015 London (DE-627)ELV012704822 volume:409 year:2017 day:24 month:11 pages:227-240 extent:14 https://doi.org/10.1016/j.jsv.2017.07.056 Volltext GBV_USEFLAG_U GBV_ELV SYSFLAG_U SSG-OLC-PHA GBV_ILN_20 GBV_ILN_30 GBV_ILN_40 44.11 Präventivmedizin VZ AR 409 2017 24 1124 227-240 14 045F 530 |
| spelling |
10.1016/j.jsv.2017.07.056 doi GBVA2017020000002.pica (DE-627)ELV036138126 (ELSEVIER)S0022-460X(17)30589-8 DE-627 ger DE-627 rakwb eng 530 530 DE-600 610 VZ 610 VZ 44.11 bkl Alexander, W. Nathan verfasserin aut Noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence 2017transfer abstract 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Turbulence ingestion Elsevier Haystacking Elsevier Boundary layer ingestion Elsevier Devenport, William J. oth Glegg, Stewart A.L. oth Enthalten in Academic Press Robison, K.M. ELSEVIER Cancer of the uterus and treatment of incontinence (CUTI) 2015 London (DE-627)ELV012704822 volume:409 year:2017 day:24 month:11 pages:227-240 extent:14 https://doi.org/10.1016/j.jsv.2017.07.056 Volltext GBV_USEFLAG_U GBV_ELV SYSFLAG_U SSG-OLC-PHA GBV_ILN_20 GBV_ILN_30 GBV_ILN_40 44.11 Präventivmedizin VZ AR 409 2017 24 1124 227-240 14 045F 530 |
| allfields_unstemmed |
10.1016/j.jsv.2017.07.056 doi GBVA2017020000002.pica (DE-627)ELV036138126 (ELSEVIER)S0022-460X(17)30589-8 DE-627 ger DE-627 rakwb eng 530 530 DE-600 610 VZ 610 VZ 44.11 bkl Alexander, W. Nathan verfasserin aut Noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence 2017transfer abstract 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Turbulence ingestion Elsevier Haystacking Elsevier Boundary layer ingestion Elsevier Devenport, William J. oth Glegg, Stewart A.L. oth Enthalten in Academic Press Robison, K.M. ELSEVIER Cancer of the uterus and treatment of incontinence (CUTI) 2015 London (DE-627)ELV012704822 volume:409 year:2017 day:24 month:11 pages:227-240 extent:14 https://doi.org/10.1016/j.jsv.2017.07.056 Volltext GBV_USEFLAG_U GBV_ELV SYSFLAG_U SSG-OLC-PHA GBV_ILN_20 GBV_ILN_30 GBV_ILN_40 44.11 Präventivmedizin VZ AR 409 2017 24 1124 227-240 14 045F 530 |
| allfieldsGer |
10.1016/j.jsv.2017.07.056 doi GBVA2017020000002.pica (DE-627)ELV036138126 (ELSEVIER)S0022-460X(17)30589-8 DE-627 ger DE-627 rakwb eng 530 530 DE-600 610 VZ 610 VZ 44.11 bkl Alexander, W. Nathan verfasserin aut Noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence 2017transfer abstract 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Turbulence ingestion Elsevier Haystacking Elsevier Boundary layer ingestion Elsevier Devenport, William J. oth Glegg, Stewart A.L. oth Enthalten in Academic Press Robison, K.M. ELSEVIER Cancer of the uterus and treatment of incontinence (CUTI) 2015 London (DE-627)ELV012704822 volume:409 year:2017 day:24 month:11 pages:227-240 extent:14 https://doi.org/10.1016/j.jsv.2017.07.056 Volltext GBV_USEFLAG_U GBV_ELV SYSFLAG_U SSG-OLC-PHA GBV_ILN_20 GBV_ILN_30 GBV_ILN_40 44.11 Präventivmedizin VZ AR 409 2017 24 1124 227-240 14 045F 530 |
| allfieldsSound |
10.1016/j.jsv.2017.07.056 doi GBVA2017020000002.pica (DE-627)ELV036138126 (ELSEVIER)S0022-460X(17)30589-8 DE-627 ger DE-627 rakwb eng 530 530 DE-600 610 VZ 610 VZ 44.11 bkl Alexander, W. Nathan verfasserin aut Noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence 2017transfer abstract 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. Turbulence ingestion Elsevier Haystacking Elsevier Boundary layer ingestion Elsevier Devenport, William J. oth Glegg, Stewart A.L. oth Enthalten in Academic Press Robison, K.M. ELSEVIER Cancer of the uterus and treatment of incontinence (CUTI) 2015 London (DE-627)ELV012704822 volume:409 year:2017 day:24 month:11 pages:227-240 extent:14 https://doi.org/10.1016/j.jsv.2017.07.056 Volltext GBV_USEFLAG_U GBV_ELV SYSFLAG_U SSG-OLC-PHA GBV_ILN_20 GBV_ILN_30 GBV_ILN_40 44.11 Präventivmedizin VZ AR 409 2017 24 1124 227-240 14 045F 530 |
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Enthalten in Cancer of the uterus and treatment of incontinence (CUTI) London volume:409 year:2017 day:24 month:11 pages:227-240 extent:14 |
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Enthalten in Cancer of the uterus and treatment of incontinence (CUTI) London volume:409 year:2017 day:24 month:11 pages:227-240 extent:14 |
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noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence |
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Noise from a rotor ingesting a thick boundary layer and relation to measurements of ingested turbulence |
| abstract |
Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. |
| abstractGer |
Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. |
| abstract_unstemmed |
Haystacked peaks in rotor noise spectra are produced by the correlated unsteady loading on neighboring blades. This noise can be predicted with knowledge of the turbulent inflow and blade response function, but this is not trivial, especially for complex turbulent inflows that are both inhomogeneous and anisotropic. This paper details the radiated noise and direct measurement of the unsteady upwash correlation in the rotating frame of a 10-bladed, 457mm diameter rotor immersed in planar wall boundary layers of different thickness at non-thrusting and thrusting advance ratios. At low thrust conditions, the measured upwash correlation can be predicted using the fixed frame space-time correlation function of the undisturbed inflow. However, as the advance ratio is lowered, predictions progressively deviate from measurements. This is shown to be due to both the distortion of the approaching turbulence and the formation of a separation region on the wall beneath the rotor. At these low advance ratios, haystacks at the blade passage frequency and harmonics are observed in the blade-to-blade upwash coherence spectra at spanwise locations near the blade tips. Also, a lateral contraction of the turbulence is not observed in measurement of the spanwise coherence with increasing thrust. Finally, increasing the boundary layer thickness increases spectral levels of the radiated noise at higher advance ratios near zero thrust by a factor similar to the increase in boundary layer thickness. At low advance ratios, peaks in the measured noise have the same approximate magnitude for similar rotational and freestream velocities regardless of the boundary layer thickness as these are likely produced by interaction with vortex structures in the separated region. |
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