Aeroacoustic formulations for confined flows based on incompressible flow data

Maurerlehner, Paul; Schoder, Stefan; Tieber, Johannes; Freidhager, Clemens; Steiner, Helfried; Brenn, Günter; Schäfer, Karl-Heinz; Ennemoser, Andreas

doi:10.1051/aacus/2022041

Cited by 9 publications

(9 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Literature suggests that this unusual amplification of the acoustic is possibly by a duct mode resonance [12,15]. The duct mode was confirmed by a 2D eigenmode simulation [48] using openCFS [49] and the influence of the flow was corrected according to [50]. Also noteworthy is that at OP1, a hump between the BPF and the first harmonic occurs.…”

Section: Initial Campaignmentioning

confidence: 80%

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

Schoder¹,

Schmidt²,

Fürlinger³

et al. 2023

Preprint

View full text Add to dashboard Cite

New innovative green concepts in electrified vertical take-off and landing vehicles currently emerge as a revolution to urban mobility going into the third dimension (vertically). The high population density of cities makes the market share highly attractive while posing an extraordinary challenge for community acceptance due to the increasing and possibly noisier commuter traffic. In addition to passenger transport, package deliveries to customers by drones may enter the market. The new challenges associated with this increasing transportation need in urban, rural and populated areas pose challenges for established companies and startups to deliver low-noise emission products. The article's objective is to revisit the benefits and drawbacks of an affordable acoustic measurement campaign focused on early prototyping. In the very early phase of product development, often considerably limited resources are available. With this in mind, the article discusses the sound power results using the enveloping surface method in a typically available low-reflection room with a reflecting floor according to DIN EN ISO 3744:2011-02. The method is applied to a subsonic electric ducted fan (EDF) unit of a 1:2 scaled electrified vertical take-off and landing vehicle. The results show that considerable information at low costs can be gained for the early prototyping stage, despite this easy-to-use, easy-to-realize, and not fine-tuned measurement setup. Furthermore, the limitations and improvements to a possible experimental setup are presented to discuss a potentially more ideal measurement environment. Measurements at discrete operating points and transient measurements across the total operating range were conducted to provide complete information on the EDF's acoustic behavior. The rotor-self noise and the rotor-stator interaction were identified as primary tonal sound sources, along with the highest broadband noise sources located on the rotor. Based on engineering experience, a first acoustic improvement treatment is also quantified with a sound power level reduction of 4dB(A). In conclusion, the presented method is a beneficial first measurement campaign to quantify the acoustic properties of an electric ducted fan unit at minimal resources in a reasonable time of several weeks when starting from scratch.

show abstract

Section: Initial Campaignmentioning

confidence: 80%

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

Schoder¹,

Schmidt²,

Fürlinger³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…In a recent investigation, Maurerlehner et al [21] validated a methodology employing FEM, based on the hybrid computational aeroacoustic approach, for the simulation of the acoustic field of confined flows with a modular test rig. In [28], Maurerlehner investigated the aero-and vibroacoustic sound emissions of several geometries that induce turbulence and flow instabilities, e.g., a half-moon-shaped orifice in a circular pipe.…”

Section: Validation Example: Pipe With Orificementioning

confidence: 99%

“…The open source BEM software NiHu (https://last.hit.bme.hu/nihu (accessed on 23 November 2023)) [20] was verified previously by several test cases. In the first step focusing on the automotive industry, the FEM-BEM method was verified and compared with an existing acoustic simulation of a confined flow-sound prediction using the FEM method [21]. This example shows the accuracy of the workflow for a simple, realistic application.…”

Section: Introductionmentioning

confidence: 99%

Experimental Prediction Method of Free-Field Sound Emissions Using the Boundary Element Method and Laser Scanning Vibrometry

Wurzinger,

Kraxberger,

Maurerlehner

et al. 2024

Acoustics

Self Cite

View full text Add to dashboard Cite

Acoustic emissions play a major role in the usability of many product categories. Therefore, mitigating the emitted sound directly at the source is paramount to improve usability and customer satisfaction. To reliably predict acoustic emissions, numerical methods such as the boundary element method (BEM) are employed, which allow for predicting, e.g., the acoustic emission into the free field. BEM algorithms need appropriate boundary conditions to couple the sound field with the structural motion of the vibrating body. In this contribution, firstly, an interpolation scheme is presented, which allows for appropriate interpolation of arbitrary velocity data to the computational grid of the BEM. Secondly, the free-field Helmholtz problem is solved with the open-source BEM software framework NiHu. The forward coupling between the device of interest and BEM is based on the surface normal velocities (i.e., a Neumann boundary condition). The BEM simulation results are validated using a previously established aeroacoustic benchmark problem. Furthermore, an application to a medical device (knee prosthesis frame) is presented. Furthermore, the radiated sound power is evaluated and contextualized with other low-cost approximations. Regarding the validation example, very good agreements are achieved between the measurements and BEM results, with a mean effective pressure level error of 0.63 dB averaged across three microphone positions. Applying the workflow to a knee prosthesis frame, the simulation is capable of predicting the acoustic radiation to four microphone positions with a mean effective pressure level error of 1.52 dB.

show abstract

“…Experimentally, these modes can be measured using a loudspeaker as a source inside the duct, driven at a specific frequency, and evaluating the sound emissions characteristics and directivity without flow. The duct mode was confirmed by a 2D eigenmode simulation [63] using openCFS [64] and the influence of the flow was corrected according to [65]. Furthermore, it is noteworthy is that at OP1, a hump between the BPF and the first harmonic occurs.…”

Section: Initial Campaignmentioning

confidence: 99%

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

Schoder

Schmidt

Fürlinger³

et al. 2023

Fluids

Self Cite

View full text Add to dashboard Cite

New innovative green concepts in electrified vertical take-off and landing vehicles are currently emerging as a revolution in urban mobility going into the third dimension (vertically). The high population density of cities makes the market share highly attractive while posing an extraordinary challenge in terms of community acceptance due to the increasing and possibly noisier commuter traffic. In addition to passenger transport, package deliveries to customers by drones may enter the market. The new challenges associated with this increasing transportation need in urban, rural, and populated areas pose challenges for established companies and startups to deliver low-noise emission products. The article’s objective is to revisit the benefits and drawbacks of an affordable acoustic measurement campaign focused on early prototyping. In the very early phase of product development, available resources are often considerably limited. With this in mind, this article discusses the sound power results using the enveloping surface method in a typically available low-reflection room with a reflecting floor according to DIN EN ISO 3744:2011-02. The method is applied to a subsonic electric ducted fan (EDF) unit of a 1:2 scaled electrified vertical take-off and landing vehicle. The results show that considerable information at low costs can be gained for the early prototyping stage, despite this easy-to-use, easy-to-realize, and non-fine-tuned measurement setup. Furthermore, the limitations and improvements to a possible experimental setup are presented to discuss a potentially more ideal measurement environment. Measurements at discrete operating points and transient measurements across the total operating range were conducted to provide complete information on the EDF’s acoustic behavior. The rotor-self noise and the rotor–stator interaction were identified as primary tonal sound sources, along with the highest broadband noise sources located on the rotor. Based on engineering experience, a first acoustic improvement treatment was also quantified with a sound power level reduction of 4 dB(A). In conclusion, the presented method is a beneficial first measurement campaign to quantify the acoustic properties of an electric ducted fan unit under minimal resources in a reasonable time of several weeks when starting from scratch.

show abstract

Aeroacoustic formulations for confined flows based on incompressible flow data

Cited by 9 publications

References 50 publications

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

Experimental Prediction Method of Free-Field Sound Emissions Using the Boundary Element Method and Laser Scanning Vibrometry

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

Contact Info

Product

Resources

About