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52. Novel liner concepts

Author

Bake, Friedrich and Knobloch, Karsten

Subjects
Wall treatment, Structure (mathematical logic), Computer science, Triebwerksakustik, Aerospace Engineering, Mechanical engineering, Transportation, Ranging, Range (mathematics), Proof of concept, Broadband, Aeroacoustics, Acoustic damping, Liner, Novel liner concepts
Abstract

Modern, low-emission aero-engine concepts, such as, for instance, Ultrahigh-Bypass Ratio (UHBR) designs, claim higher demands on the damping performance of acoustic wall treatment, called liner, installed in the engine. New liner concepts are needed providing a more broadband damping efficiency ranging explicitly to the low-frequency range. However, space and weight constrains are still also one of the crucial criteria which need to be fulfilled by the liner structure. To overcome this challenge, two novel liner concepts are presented here. One concept, the hybrid ZML, combines the classical Single-Degree-of-Freedom (SDOF) liner with a Zero-Massflow-Liner (ZML) principle. The other one, the FlexiS concept, takes advantage of the intrinsic material damping of flexible walls within the liner structure. A proof of concepts study of both novel concepts is provided highlighting the enhanced damping performance with respect to broadband capacity and low-frequency damping.

Published
2019
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60. Swirl–nozzle interaction experiment: quasi-steady model-based analysis

Author

Hirschberg, L. (author), Bake, Friedrich (author), Knobloch, Karsten (author), Rudolphi, Angelo (author), Kruck, Sebastian (author), Klose, Oliver (author), Hulshoff, S.J. (author), Hirschberg, L. (author), Bake, Friedrich (author), Knobloch, Karsten (author), Rudolphi, Angelo (author), Kruck, Sebastian (author), Klose, Oliver (author), and Hulshoff, S.J. (author)

Abstract

Measurements of sound due to swirl–nozzle interaction are presented. In the experiment a swirl structure was generated by means of unsteady tangential injection into a steady swirl-free flow upstream from a choked convergent–divergent nozzle. Ingestion of swirl by the choked nozzle caused a mass-flow rate change, which resulted in a downstream-measured acoustic response. The downstream acoustic pressure was found to remain negative as long as the swirl is maintained and reflections from the open downstream pipe termination do not interfere. The amplitude of this initial acoustic response was found to be proportional to the square of the tangential mass-flow rate used to generate swirl. When the tangential injection valve was closed, the mass-flow rate through the nozzle increased, resulting in an increase of the downstream acoustic pressure. This increase in signal was compared to the prediction of an empirical quasi-steady model, constructed from steady-state flow measurements. As the opening time of the valve was varied, the signal due to swirl evacuation showed an initial overshoot with respect to quasi-steady behavior, after which it gradually decayed to quasi-steady behavior for tangential injection times long compared to the convection time in the pipe upstream of the nozzle. This demonstrates that the acoustic signal can be used to obtain quantitative information concerning the time dependence of the swirl in the system. This could be useful for understanding the dynamics of flow in engines with swirl-stabilized combustion. Graphic abstract: [Figure not available: see fulltext.]., Aerodynamics

Published
2021
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61. Swirl-Nozzle Interaction Experiments: Influence of Injection-Reservoir Pressure and Injection Time

Author

Hirschberg, L. (author), Bake, F. (author), Knobloch, Karsten (author), Hulshoff, S.J. (author), Hirschberg, L. (author), Bake, F. (author), Knobloch, Karsten (author), and Hulshoff, S.J. (author)

Abstract

View Video Presentation: https://doi-org.tudelft.idm.oclc.org/10.2514/6.2021-2286.vid Quantitative measurements of sound due to swirl-nozzle interaction are presented for the first time. In the experiment a swirl structure was generated by means of tangential injection into a steady swirl-free flow upstream from a choked convergent-divergent nozzle. Ingestion of swirl by the choked nozzle caused a mass-flow rate change, which resulted in a downstream measured acoustic response. The amplitude of this acoustic response was found to be proportional to the square of the tangential mass-flow rate used to generate swirl. This was, assuming that the upstream generated swirl intensity is proportional to the tangential injection mass-flow rate, predicted by a previously published quasi-steady model for the swirl-nozzle interaction sound source (Hirschberg, L., Hulshoff, S. J., and Bake, F., “Sound Production due to Swirl-Nozzle Interaction: Model-Based Analysis of Experiments,” AIAA Journal, Published online on Nov. 11th 2020, doi: 10.2514/1.J059669.). The tangential-injection time was varied, and found to not influence the amplitude of the acoustic response. This indicates that quasi-steady modelling remains applicable, even for smallest achievable upstream swirl structure with an axial length of ca. three upstream diameters., Aerodynamics

Published
2021
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78. Hindlimb growth after a transphyseal reconstruction of the anterior cruciate ligament: a study in skeletally immature sheep with wide-open physes

Author

Meller, Rupert, Kendoff, Daniel, Hankemeier, Stefan, Jagodzinski, Michael, Grotz, Martin, Knobloch, Karsten, and Krettek, Christian

Subjects
Anterior cruciate ligament -- Injuries, Anterior cruciate ligament -- Research, Orthopedic surgery -- Complications and side effects, Orthopedic surgery -- Research, Bones -- Growth, Bones -- Influence, Bones -- Research, Health, Sports and fitness
Published
2008

79. Superior Achilles Tendon Microcirculation in Tendinopathy Among Symptomatic Female Versus Male Patients

Author

Knobloch, Karsten, Schreibmueller, Louisa, Meller, Rupert, Busch, Kay H., Spies, Marcus, and Vogt, Peter M.

Subjects
Microcirculation -- Physiological aspects -- Research, Tendinitis -- Diagnosis -- Care and treatment -- Research, Achilles tendon -- Physiological aspects -- Research, Health, Sports and fitness, Diagnosis, Care and treatment, Physiological aspects, Research
Abstract

Byline: Karsten Knobloch, MD, PhD (Departments of Plastic, Hand, and Reconstructive Surgery, kknobi@yahoo.com); Louisa Schreibmueller, MD (Departments of Plastic, Hand, and Reconstructive Surgery); Rupert Meller, MD (Trauma Surgery, Hannover Medical [...]

Published
2008
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82. Acoustic Pressure Measurements in High-Temperature Environment

Author

Knobloch, Karsten, Enghardt, Lars, Bake, Friedrich, DLR Institut für Antriebstechnik / Institute of Propulsion Technology, and Deutsches Zentrum für Luft- und Raumfahrt [Köln] (DLR)

Subjects
[PHYS.MECA.VIBR]Physics [physics]/Mechanics [physics]/Vibrations [physics.class-ph], Microphone probes, measurement and simulation, acoustic pressure measurements, transfer function, Microphone probe, [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph]
Abstract

International audience; In order to measure acoustic pressure in flow ducts at temperature above 100°C or in combustion chambers, the use of high-accuracy condenser microphones is no longer possible due to the heat load damaging the delicate components. A possible mitigation is the remote placement of the microphone, with the sensor connected via a small diameter waveguide to the desired measurement location. Such a device (called ?microphone probe?) has been build and used by DLR Berlin for several years for the investigation of in-duct sound fields at elevated pressure and temperature. However, there are certain calibration procedures and corrections required to account for the probe design. An experimental test series has been made to assess the probe characteristics. Special focus was set on the influence of the extension of the waveguide, which shall reduce the detrimental effect of reflections on the measured signal. Tests included a comparative calibration and high temperature and high pressure testing. The results are compared to a one-dimensional model of the probe design.

Published
2020
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84. Eccentric training and an Achilles wrap reduce Achilles tendon capillary blood flow and capillary venous filling pressures and increase tendon oxygen saturation in insertional and midportion tendinopathy: a randomized trial

Author

Knobloch, Karsten, Schreibmueller, Louisa, Kraemer, Robert, Jagodzinski, Michael, Richter, Martinus, Zeichen, Johannes, and Vogt, Peter M.

Subjects
Tendon injuries -- Risk factors -- Care and treatment -- Diagnosis, Microcirculation disorders -- Diagnosis -- Risk factors -- Care and treatment, Sports injuries -- Diagnosis -- Care and treatment -- Risk factors, Achilles tendon -- Injuries, Health, Sports and fitness, Diagnosis, Care and treatment, Risk factors, Injuries
Abstract

Background: Eccentric training has been demonstrated to decrease pain in patients with Achilles tendinopathy. Whether an Achilles wrap in addition to eccentric training changes parameters of tendon microcirculation in insertional [...]

Published
2007

87. Changes of Achilles midportion tendon microcirculation after repetitive simultaneous cryotherapy and compression using a Cryo/Cuff

Author

Knobloch, Karsten, Grasemann, Ruth, Jagodzinski, Michael, Richter, Martinus, Zeichen, Johannes, and Krettek, Christian

Subjects
Tendon injuries -- Care and treatment, Cold -- Health aspects, Sports injuries -- Care and treatment, Achilles tendon -- Health aspects, Health, Sports and fitness, Care and treatment, Health aspects
Abstract

Background: Cryotherapy and compression have been shown to decrease pain and improve function. The dosage and timing of these options remain unclear. Purpose: To examine the effects of a standardized [...]

Published
2006

88. Achilles tendon and paratendon microcirculation in midportion and insertional tendinopathy in athletes

Author

Knobloch, Karsten, Robert, Kraemer, Lichtenberg, Artur, Jagodzinski, Michael, Gossling, Thomas, Richter, Martinus, Zeichen, Johannes, Hufner, Tobias, and Krettek, Christian

Subjects
Tendon injuries -- Care and treatment, Athletes -- Injuries -- Health aspects, Sports injuries -- Care and treatment, Achilles tendon -- Medical examination -- Health aspects, Health, Sports and fitness, Care and treatment, Medical examination, Injuries, Health aspects
Abstract

Background: Neovascularisation can be detected qualitatively by Power Doppler in Achilles tendinopathy. Quantitative data regarding tendon microcirculation have not been established and may be substantial. Purpose; To assess the microcirculation of the Achilles tendon and the paratendon in healthy volunteers as well as in athletes with either midportion or insertional tendinopathy. Study Design: Cohort study; Level of evidence, 2. Methods: In 66 physically active volunteers, parameters of Achilles tendon and paratendon microcirculation, such as tissue oxygen saturation, relative postcapillary venous filling pressures, and microcirculatory blood flow, were determined at rest at 2-mm and 8-mm tissue depths. Forty-one patients never had Achilles pain (25 men, 27 ± 8 years), 14 patients had insertional pain (7 men, 29 ± 8 years), and 11 patients had midportion tendinopathy (7 men, 38 ± 13 years, not significant). Results: Achilles tendon diameter 2 cm and 6 cm proximal to the insertion was increased in symptomatic tendons. Compared with the uninvolved opposite tendon, deep microcirculatory blood flow was significantly elevated at insertional (160 ± 79 vs 132 ± 42, P < .05) as well as in midportion tendinopathy (150 ± 74 vs 119 ± 34, P < .05). The microcirculation in the uninvolved opposite tendon and the normal athlete controls were not significantly different from each other (132 ± 42 insertional asymptomatic vs 119 ± 34 mid-portion vs 120 ± 48 healthy tendon). Insertional paratendon deep microcirculatory flow was elevated in all groups, whereas tissue oxygen saturation and relative postcapillary venous filling pressures were not significantly different. Conclusion: Microcirculatory blood flow is significantly elevated at the point of pain in insertional and midportion tendinopathy. Postcapillary venous filling pressures are increased at both the midportion Achilles tendon and the midportion paratendon, whereas tissue oxygen saturation is not different among the studied groups. We found no evidence of an abnormal microcirculation of the asymptomatic limb in Achilles tendinopathy. Keywords: Achilles tendon; tendinopathy; Doppler; pain; microcirculation, Achilles tendinopathy is a common condition of yet unknown origin and pathogenesis. (21) Treatment is currently very difficult and often anecdotal without large, evidence-based controlled intervention trials. When studying patients [...]

Published
2006

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