Thomas F Geyer

Thomas F Geyer
German Aerospace Center (DLR) | DLR · Institute of Electrified Aero Engines

Dr.-Ing. habil.

About

150
Publications
44,864
Reads
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2,006
Citations
Citations since 2017
98 Research Items
1705 Citations
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Introduction
Thomas Geyer works at the Institute of Electrified Aero Engines of the German Aerospace Center DLR. His main interest is the identification and, subsequently, reduction of noise sources at novel aircraft propulsion systems.
Additional affiliations
May 2006 - October 2021
Brandenburg University of Technology Cottbus - Senftenberg
Position
  • Lecturer
Description
  • "Machinery and Vehicle Acoustics" "Low-Noise Design" "Sound and Vibration Measurement" "Engineering Acoustics"
April 2006 - March 2008
Gesellschaft für Akustikforschung Dresden mbH
Position
  • Engineer
Education
August 2011 - September 2021
May 2006 - August 2011
October 2000 - April 2006
Technische Universität Dresden
Field of study
  • Electrical Engineering

Publications

Publications (150)
Article
Full-text available
Aeroacoustic studies of porous cylinder coatings, which reduce the vortex shedding noise of cylinders in uniform flow, have received increased attention. To further understand how porous coatings suppress the vortex shedding tone, a numerical and experimental investigation of porous coated cylinders at a Reynolds number of is presented herein. Two...
Article
Full-text available
The tonal noise generated at the tip is a major contribution to the aerodynamic noise generated by three-dimensional airfoils. One way to reduce this noise is the use of end plates, which was investigated in the present study for three different circular end plate geometries applied to a cambered NACA 4412 airfoil with aspect ratio 2 and forced bou...
Chapter
An experimental study of the aerodynamic and the aeroacoustic performance of airfoils with additive manufactured permeable leading edges under disturbed inflow conditions is presented. A turbulent inflow increases the noise emission of the airfoils, which is related to turbulence interaction noise. By integrating a permeable structure on the leadin...
Preprint
Aeroacoustic studies of porous cylinder coatings, that reduce the vortex shedding noise of cylinders in uniform flow, is receiving increased attention. To further understand how porous coatings suppress the vortex shedding tone, we present in this paper a numerical and experimental investigation of porous coated cylinders at a Reynolds number of $1...
Article
Full-text available
This paper is a predominantly experimental study into the use of porosity located downstream of an aerofoil leading edge for the reduction of turbulence interaction noise. Locating the porosity downstream of the leading edge has been shown to be beneficial in reducing the aerodynamic performance penalty compared with locating it directly at the lea...
Conference Paper
Full-text available
In this work, various noise-reducing modifications known from airfoil investigations are applied to axial fans. Felts, micro-perforated plates, micro-porous resins, and porosities are applied to the leading edge of the fan blades. It was found that felts are unsuitable for the use in axial fans and that micro-perforated plates have too small active...
Conference Paper
The complex flow field around two staggered cylinders is of importance in many different engineering applications. Although it has received much attention in numerical and experimental research, only a very limited number of studies on the corresponding generation of aerodynamic noise has been published. In the study described in the present paper,...
Conference Paper
Full-text available
In this paper, the effect of uniform porous coating thickness on reducing flow noise in cylinders is investigated using numerical and experimental methods. Numerical simulations are performed using the large-eddy simulation approach with the Smagorinsky sub-grid length-scale model. The Ffowcs-Williams and Hawkings technique post-processes the press...
Conference Paper
Full-text available
The flow field around two staggered cylinders has been studied extensively due to its importance in various engineering applications. Despite the great interest attracted by both numerical and experimental research, few studies have been published on the generation of noise by this configuration. In the present work, we investigate the flow field a...
Article
The effect of a porous coating on the vortex shedding noise of a circular cylinder under disturbed inflow conditions was examined experimentally. The measurements were performed on a cylinder coated with an open-porous foam as well as on a bare reference cylinder in a small aeroacoustic wind tunnel using grid-generated turbulence. The measurements...
Article
The aerodynamic noise generated by aircraft landing gear components is often studied using a so-called tandem cylinder configuration, consisting of two circular cylinders arranged in a streamwise row and separated by a certain distance. The subject of the present study is the experimental investigation of the effect of porous coatings on the noise...
Conference Paper
Der stetige Anstieg des Luftverkehrsaufkommens bei gleichzeitiger, sehr begründeter Forderung nach deutlich zu reduzierendem Treibhausgasausstoß zum Schutz des Klimas macht die Forschung nach neuen, emissionsärmeren Luftfahrtantrieben zum weiteren Erhalt der weltweiten Mobilität vor allem für die zivile Luftfahrt notwendig. Solche Antriebe basieren...
Article
Full-text available
The special collection on Source Mechanisms and Control Methods for Aerodynamic Noise is available in the ASCE Library https://ascelibrary.org/jaeeez/source_mechanisms Aerodynamic noise, also known as aeroacoustic or flow noise, generally refers to the noise generated by unsteady flow. The noise sources are mainly associated with a turbulent flow...
Conference Paper
Full-text available
Der Einsatz von Lüftungsanlagen ist insbesondere in der Zeit der Covid-Pandemie wichtig, um ein gesundes Raumklima in Wohn- und Arbeitsräumen zu schaffen. Die eingesetzten Axialventilatoren in derartigen Anlagen sind jedoch diejenige Systemkomponente mit der höchsten Schallerzeugung. Eine erhöhte turbulente Zuströmung durch den Einsatz von Schutzgi...
Article
This paper is concerned with the flow characteristics and noise generation at the finite wing-wall junction. To characterize junction flow noise, acoustic measurements were taken in the acoustic wind tunnel at the Brandenburg University of Technology in Cottbus, Germany, with a planar 47-microphone array at a chord-based Reynolds number (Rec) of 2....
Article
Full-text available
The application of a porous coating to a smooth cylinder placed in uniform flow can reduce its vortex shedding tone and overall sound pressure level. The responsible noise generation mechanisms are not fully understood nor has an optimal porous coating type been presented. Structured Porous Coated Cylinders (SPCCs) have been recently investigated a...
Conference Paper
Full-text available
The aerodynamic noise generated by aircraft landing gear components is often studied using a so-called tandem cylinder configuration, consisting of two circular cylinders arranged in a streamwise row and separated by a certain distance. Based on previous studies that show the effectiveness of porous coatings to reduce the flow noise generated by si...
Conference Paper
The conceptual designing of rotating machines such as fans, wind turbines, counter-rotating open rotors and helicopter blades requires inexpensive and easy-to-use tools that enable rapid noise assessment and optimisation analyses. Modern numerical methods would be ideal, but they are usually too expensive to conduct in an optimisation study, while...
Article
Full-text available
A detailed experimental study on the aerodynamic performance and noise emission of airfoils and fan blades with permeable leading edge under disturbed inflow conditions was performed. The airfoils and fan blades with permeable leading edges were made of an aluminum alloy using a powder bed fusion based additive manufacturing process. In a first ste...
Article
Full-text available
This paper presents an experimental investigation of tip vortex formation noise produced by wall-mounted finite airfoils. Acoustic measurements were taken in the open jet anechoic wind tunnel at Brandenburg University of Technology with a planar 47-microphone array. A parameter space of eight airfoil models with variations in airfoil profile shape...
Article
Dissipative mufflers are often used for the reduction of broadband noise transmitted in ducts. Many common calculation procedures for the transmission loss of such mufflers require conventional shapes like rectangular or circular cross-sectional areas. In an effort to analyze the effect of the cross-sectional area of dissipative mufflers on the res...
Conference Paper
Full-text available
Der an Teilen des Fahrwerks von Flugzeugen entstehende Umströmungsschall wird oftmals vereinfacht an einer sogenannten Tandem-Zylinder-Anordnung untersucht, bei der sich in einem definierten Abstand stromab eines Zylinders ein zweiter Zylinder gleichen Durchmessers befindet. Der dabei entstehende Schall ist durch einen starken tonalen Anteil gekenn...
Conference Paper
An experimental investigation on the acoustic and aerodynamic effect of permeable structures at airfoils and fan blades under distorted inflow conditions was performed. The study focuses on the position and the extent of the porous structure with respect to the leading edge. In a first step, aerodynamic and aeroacoustic measurements are carried out...
Conference Paper
We consider a finite perforated plate and study the effects of smoothly varying chordwise porosity on turbulence-aerofoil interaction noise. To study this problem, we use a novel Mathieu function collocation method, rather than a traditional Wiener-Hopf approach which would be unable to deal with chordwise varying quantities. Our main focus is on t...
Article
Der lautlose Flug der Eulen ist eines der bekanntesten Beispiele für die Anpassungsfähigkeit der Natur und Vorbild für viele Innovationen auf dem Gebiet der Strömungsakustik mit dem Ziel der Lärmminderung an technischen Anwendungen wie Ventilatoren oder Windenergieanlagen. Die Ursachen dieses leisen Flugs sind, neben der geringen Fluggeschwindigkei...
Data
This is a gif that I made from the surface flow visualization obtained at different chord-based Reynolds numbers. The wall-mounted airfoil is a NACA0012 at 0° angle of attack, flow is from top to bottom.
Article
This paper presents an acoustic study of a standard NACA 0012 aerofoil with additional self-oscillating passive flaplets deployed from the trailing edge for self-noise reduction, putting special emphasis on the potential reduction of tonal noise generated by the periodic shedding of vortices from the trailing edge. The flaplets protruding out of th...
Article
Full-text available
One known method to reduce vortex shedding from the tip of a blade is the use of end plates or winglets. Although the aerodynamic impact of such end plates has been investigated in the past, no studies exist on the effect of such end plates on the far-field noise. The aeroacoustic noise reduction of three different end-plate geometries is experimen...
Article
The noise generated by finite, wall-mounted airfoils strongly affects the total noise from aerodynamic applications such as small unmanned aerial vehicles, micro wind turbines and cooling fans. In an attempt to understand the effect of airfoil thickness on the trailing edge tonal noise generated by such airfoils, detailed wind tunnel experiments ha...
Chapter
An aeroacoustic investigating looking into the effect of changing the inter-spacing of passive self-oscillating trailing edge flaplets has been carried out using a NACA 0012 aerofoil. Clear differences can be observed between each of the different cases. Where a reduction in low frequency noise, an increase in high frequency noise and a reduction i...
Article
Full-text available
The vortex shedding tone of a cylinder in uniform flow can be reduced by applying a porous coating yet this mechanism is not fully understood. An experimental investigation of asymmetric Structured Porous Coated Cylinders (SPCCs) was conducted in a small anechoic wind tunnel using a hot-wire anemometry probe placed in the boundary layer, separated...
Article
This paper investigates the effect of the geometric parameters-rod diameter and the distance between the rod and the airfoil-on the noise generated by a rod-airfoil configuration using experimental and numerical techniques. The numerical simulations are carried out using the low-dissipation up-wind scheme and the Delayed-Detached-Eddy Simulation (D...
Chapter
Aerofoil noise reduction is aTalboys, Edward topic of great interest at the present time and as such many strategies have been presented,Geyer, Thomas F. in previous literatures whether they are trailing edge serrations, leading edge undulations or porous aerofoils, to name a few. The present study investigates a bio-inspired solution where an arra...
Conference Paper
Full-text available
The vortex shedding tone of a cylinder in uniform flow can be suppressed by applying a porous coating yet the mechanisms responsible are not fully understood, nor is the optimal porous coating design. In this paper, Structured Porous Coated Cylinders (SPCCs) are investigated that have a porous structure that is not randomized (such as metal foam or...
Preprint
Full-text available
This paper investigates the effect of the geometric parameters -- rod diameter and the distance between the rod and the airfoil -- on the noise generated by rod-airfoil configuration using experimental and numerical techniques. The numerical simulations are carried out using the low-dissipation up-wind scheme and the Delayed-Detached-Eddy Simulatio...
Article
Full-text available
This paper considers the effects of smoothly varying chordwise porosity of a finite perforated plate on turbulence-aerofoil interaction noise. The aeroacoustic model is made possible through the use of a novel Mathieu function collocation method, rather than a traditional Wiener–Hopf approach, which would be unable to deal with chordwise varying qu...
Conference Paper
Full-text available
An experimental investigation of the aerodynamic performance and noise emission of airfoils and fan blades with perforated leading edges is presented. In a first step, a detailed wind tunnel study was carried out. Therefore, measurements on sixteen airfoils with different leading edge designs were performed for various flow speeds and geometric ang...
Article
Full-text available
The tonal noise generation of a circular cylinder in a uniform flow is an important source of aerodynamic noise. It can be found at parts of the landing gear of airplanes, at pantographs of trains, at antennas and basically all other protruding parts of vehicles. This noise is due to the periodic shedding of vortices along the cylinder span. One me...
Conference Paper
Full-text available
The vortex shedding tone magnitude of a cylinder in uniform flow can be suppressed by applying a porous coating. The mechanism for the vortex shedding tone suppression is not fully understood, nor is the optimal porous coating to achieve maximum tone suppression. Understanding the internal flow field of Porous Coated Cylinder (PCC) can provide a de...
Preprint
Full-text available
This paper presents an acoustic study of a standard NACA 0012 aerofoil with additional self-oscillating passive flaplets attached to the trailing edge. The tests with varying geometries of the flaplets were conducted in the anechoic wind tunnel at Brandenburg University of Technology, at chord based Reynolds numbers, $Re_c = 100,000 - 900,000$ at t...
Article
Full-text available
The interaction of a turbulent flow with the leading edge of a blade is a main noise source mechanism for fans and wind turbines. Motivated by the silent flight of owls, the present paper describes an experimental study performed to explore the noise-reducing effect of comb-like extensions, which are fixed to the leading edge of a low-speed airfoil...
Article
Full-text available
Airfoil tip vortex formation noise is a significant noise source in many aerodynamic applications such as aircraft, fans, rotors and propellers. The data collection presented in this paper examines the effects of sinusoidal geometry and porosity on the tip vortex formation noise produced by finite length airfoils. The use of serrated and porous mat...
Article
The aerodynamic noise generated by a circular cylinder in a cross flow is a classical problem in aeroacoustics, which can be found in various practical applications such as parts of the landing gear of airplanes, train pantographs and antennas of vehicles. The noise is especially disturbing since it contains strong tonal contributions due to the re...
Article
Full-text available
The vortex generated at the tip of an airfoil such as an aircraft wing, wind turbine blade, submarine fin or propeller blade can dominate its wake and be a significant source of unwanted noise. The data collection presented in this paper consists of measurements of tip vortex formation noise produced by finite length airfoils with flat and rounded...
Conference Paper
Full-text available
The aeroacoustics of a tripped NACA0012 aerofoil with an array of self-oscillating flexible flaplets attached to the trailing edge at low to moderate Reynolds number and at geometric angles of attack α g = 0 • − 20 • is investigated. A low frequency noise reduction occurs at a chord-based Strouhal number of 2-3 across all Reynolds number and angles...
Conference Paper
Full-text available
The flow around circular cylinders is one of the major aeroacoustic noise source mechanisms. Such a cylinder represents a simple model for technical applications like parts of the landing gear of airplanes, train pantographs, antennas or other protruding parts of vehicles. A reduction of the flow noise is especially desirable since it contains both...
Article
Serrated leading edges are well-known for their ability to reduce leading edge broadband noise at highly turbulent inflow conditions. For maximum effect, special care needs to be taken in the selection of the geometric parameters. To date, several extensive studies of numerical and experimental nature are available, focusing on the identification o...
Article
Full-text available
The application of open-porous materials is a possible method to effectively reduce the aerodynamic noise of an airfoil. However, the porous consistency may have a negative effect on the aerodynamic performance of the airfoil, since very often the lift is decreased while the drag increases. In a recent investigation, the generation of trailing edg...
Conference Paper
Full-text available
Bildet sich bei der Umströmung eines Tragflügel- oder Schaufelprofils auf dessen Oberfläche eine laminare Grenzschicht aus, so kommt es zu einer stark tonalen Schallentstehung. Diese äußert sich durch eine sehr charakteristische spektrale Struktur, die sich aus deutlichen Haupttönen und weiteren kleineren Nebenmaxima zusammensetzt. Dieser Schallent...
Article
Full-text available
Phased microphone arrays have become a well-established tool for performing aeroacoustic measurements in wind tunnels (both open-jet and closed-section), flying aircraft, and engine test beds. This paper provides a review of the most well-known and state-of-the-art acoustic imaging methods and recommendations on when to use them. Several exemplary...
Article
Full-text available
The aeroacoustics of a NACA 0012 aerofoil with an array of self-oscillating flexible flaplets attached to the trailing edge has been investigated at low to moderate chord based Reynolds number (50,000–350,000) and at geometric angles of attack from α = 0° – 20°. Two distinct situations were tested: one in which the flaplets were attached to the pre...
Article
Full-text available
Steel sheet metal is important for architecture, for mechanical engineering and vehicle construction due to its various usability and the fact that it is relatively easy to manufacture. When a regular structure is applied to such metal plates, their stiffness can be increased significantly in order to meet higher static requirements while keeping t...
Chapter
Measurements of flow induced wall-mounted finite airfoil noise have been taken in an anechoic wind tunnel to examine the influence of camber on tonal noise production. The airfoils have an aspect ratio (ratio of airfoil span, L, to chord, C) of \(L/C = 2\) and measurements encompass variations in camber of 0–8%. The results include far-field acoust...
Article
Full-text available
When a cylinder is subject to a flow, vortices will be shed that can lead to strong tonal noise. The modification of the cylinder with soft, flexible flaps made of silicone rubber has been shown to affect the vortex shedding cycle in a way that the Strouhal number associated with the vortex shedding suddenly jumps to a higher value at a certain Rey...
Article
Full-text available
With the aim of reducing turbulence interaction noise of axial fans, a wind tunnel study was performed on airfoils equipped with a flow permeable leading edge. The leading edges were realized as bulk materials with round pores and manufactured using rapid prototyping. The inflow turbulence was generated by a turbulence grid. Acoustic measurements w...
Preprint
Full-text available
The aeroacoustics of a NACA 0012 aerofoil with an array of self-oscillating flexible flaplets attached on the trailing edge has been investigated at low to moderate chord based Reynolds number (50,000-350,000) and at geometric angles of attack from α = 0-20. When the aerofoil is untripped, tonal peaks are observed on the baseline aerofoil. When the...
Preprint
The aeroacoustics of a NACA 0012 aerofoil with an array of self-oscillating flexible flaplets attached on the trailing edge has been investigated at low to moderate chord based Reynolds number (50,000 -- 350,000) and at geometric angles of attack from $\alpha_g = 0^\circ$ -- $20^\circ$. When the aerofoil is untripped, tonal peaks are observed on th...
Conference Paper
Full-text available
The application of open-porous materials is one possible method to reduce the aerodynamic noise of an airfoil. Depending on the exact location and extent of the porous region, it enables the reduction of trailing edge noise or of noise from the leading edge when subject to inflow turbulence. However, the porous consistency may have a negative effec...
Conference Paper
Full-text available
Time-domain boundary element methods (BEM) have been in use to calculate the unsteady loading on the airfoil for quite a long time now. The unsteady loading caused by the response of the body to the turbulent inflow is the leading cause of broadband noise from the turbomachinery. Hence, it is vitally important to calculate the unsteady loading due...
Conference Paper
Full-text available
The flow around a wall-mounted finite airfoil with natural transition can lead to complex tonal characteristics in the corresponding aeroacoustic noise spectra. While many of the flow features and noise generating mechanisms are well understood, there are still open questions, for example regarding the influence of the airfoil shape. In the present...
Conference Paper
Aerofoils subjected to leading edge serrations have been in the focus of several recently published studies. Especially when it comes to inflow conditions of high turbulence, serrations have proofed to be of high aeroacoustic effect. Aerodynamically, serrations are known to reduce the total lift but lead to a delay of the stall angle as well as to...
Conference Paper
Full-text available
The use of porous materials is a known method for the reduction of cylinder vortex shedding noise. In a previous experimental wind tunnel study, the noise reducing effect of a modification of circular cylinders with open-porous materials was shown. The cylinder models consisted of a solid core cylinder with porous covers with different material par...
Conference Paper
Full-text available
Aerofoil noise reduction is a topic of great interest at the present time and as such many strategies have been presented, in previous literatures whether they are trailing edge serrations, leading edge undulations or porous aerofoils, to name a few. The present study investigates a bio-inspired solution where an array of passive flexible elements,...