scholarly journals Wide domain simulations of flow over an unswept laminar wing section undergoing transonic buffet

2020 ◽  
Vol 5 (8) ◽  
Author(s):  
Markus Zauner ◽  
Neil D. Sandham
Keyword(s):  
Wing Section ◽  
Wide Domain ◽  
Transonic Buffet

Energetic comparison of some stump-removing methods

2014 ◽  
Vol 10 (1) ◽  
pp. 35-51
Author(s):  
I. Czupy
Keyword(s):  
Alternative Energy ◽  
Fossil Fuel ◽  
Alternating Current ◽  
Above Ground Biomass ◽  
Alternative Energy Sources ◽  
Wide Domain ◽  
Fuel Substitution ◽  
Unused Resource ◽  
Root Connection ◽  
Different Soils

Concerns about climate change and fossil fuel shortages are encouraging interest in stumps, as alternative energy sources. Stumps are an almost unused resource in the context of bio fuels. Stump harvesting signifies an intensification of forest management compared with conventional stem-only or above-ground biomass-only harvesting. There are many benefits of stump harvesting. These include: the production of wood fuel, fossil fuel substitution, and improved soil preparation.Removing tree trunks in Hungary has been going on according to the principle of stump extraction, which means stumps are removed by grabbing technology. Experiments have been carried out to reduce the extraction force. In the Great Hungarian Lowland, where large areas require the operation implementation, stump extraction is done by special, hydraulic driven baggers equipped with a special bucket. During operation of the equipment, we carried out measurements of the extraction force and the time requirement. The experiments are designed to carry out the measurements with different soils and different tree species. According to our proposal the suitable force and torque required to remove stumps can be significantly reduced if before the lifting the soil — root connection is loosened. One of the possible ways to implement this task is the use of vibration. Since relatively great vibration power and wide domain of frequency are necessary, therefore we prepared the loosening machinery elements of alternating-current hydraulics system. Based on constructions variants we created a tractor-mounted experimental alternating-current hydraulic stump-loosening machine. It was designed with the ability to produce horizontal vibration in order to loosen stumps.

scholarly journals Transonic buffet instability: From two-dimensional airfoils to three-dimensional swept wings

2019 ◽  
Vol 4 (10) ◽  
Author(s):  
Edorado Paladini ◽  
Samir Beneddine ◽  
Julien Dandois ◽  
Denis Sipp ◽  
Jean-Christophe Robinet
Keyword(s):  
Three Dimensional ◽  
Two Dimensional ◽  
Swept Wings ◽  
Transonic Buffet

scholarly journals Analysis of transonic buffet using dynamic mode decomposition

2021 ◽  
Vol 62 (4) ◽  
Author(s):  
Antje Feldhusen-Hoffmann ◽  
Christian Lagemann ◽  
Simon Loosen ◽  
Pascal Meysonnat ◽  
Michael Klaas ◽  
...  
Keyword(s):  
Shock Wave ◽  
Flow Field ◽  
Acoustic Waves ◽  
Feedback Loop ◽  
Measurement Data ◽  
Dynamic Mode Decomposition ◽  
Recirculation Region ◽  
Dynamic Mode ◽  
Mode Decomposition ◽  
Transonic Buffet

AbstractThe buffet flow field around supercritical airfoils is dominated by self-sustained shock wave oscillations on the suction side of the wing. Theories assume that this unsteadiness is driven by a feedback loop of disturbances in the flow field downstream of the shock wave whose upstream propagating part is generated by acoustic waves. High-speed particle-image velocimetry measurements are performed to investigate this feedback loop in transonic buffet flow over a supercritical DRA 2303 airfoil. The freestream Mach number is $$M_{\infty } = 0.73$$ M ∞ = 0.73 , the angle of attack is $$\alpha = 3.5^{\circ }$$ α = 3 . 5 ∘ , and the chord-based Reynolds number is $${\mathrm{Re}}_{c} = 1.9\times 10^6$$ Re c = 1.9 × 10 6 . The obtained velocity fields are processed by sparsity-promoting dynamic mode decomposition to identify the dominant dynamic features contributing strongest to the buffet flow field. Two pronounced dynamic modes are found which confirm the presence of two main features of the proposed feedback loop. One mode is related to the shock wave oscillation frequency and its shape includes the movement of the shock wave and the coupled pulsation of the recirculation region downstream of the shock wave. The other pronounced mode represents the disturbances which form the downstream propagating part of the proposed feedback loop. The frequency of this mode corresponds to the frequency of the acoustic waves which are generated by these downstream traveling disturbances and which form the upstream propagating part of the proposed feedback loop. In this study, the post-processing, i.e., the DMD, is highlighted to substantiate the existence of this vortex mode. It is this vortex mode that via the Lamb vector excites the shock oscillations. The measurement data based DMD results confirm numerical findings, i.e., the dominant buffet and vortex modes are in good agreement with the feedback loop suggested by Lee. Graphic abstract

Simulation of Transonic Buffet Using a Time-Spectral Method

AIAA Journal ◽  
2019 ◽  
Vol 57 (3) ◽  
pp. 1275-1287 ◽  
Author(s):  
Frédéric Plante ◽  
Éric Laurendeau
Keyword(s):  
Spectral Method ◽  
Time Spectral Method ◽  
Transonic Buffet
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