Experimental Investigation of Time Dependent Aerodynamic and Biological Flows

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: closed (15 January 2022) | Viewed by 6363

Special Issue Editor


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Guest Editor
1. School of Mechanical Engineering, National Technical University of Athens, 15780 Athens, Greece
2. School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
3. China-EU Institute for Clean and Renewable Energy, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: use of experimental techniques in fluid mechanics such as PIV, LDA, HWA, pressure, temperature (use of liquid crystals), wall shear and aerodynamic force measurements, and flow visualization; investigating flow phenomena such as dynamic stall and stall flutter of pitching and plunging wings; flow control using pulsating jets; aerodynamics of UAVs; performance of swim fins and sails; flow in microchannels with superhydrophobic/superhydrophylic surfaces; flow in stent models/aneurysms/self-oscillating flexible tubes; valveless pumping
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Special Issue Information

Dear Colleagues,

Unsteady flows occur in countless situations, both in nature and in technological applications. Faithfully recording quantities such velocity, pressure, and temperature in time and space is of paramount importance for broadening our understanding of the examined phenomena and improving their prediction through appropriate numerical modeling.

This Special Issue of Fluids is dedicated to experimental studies of unsteady aerodynamic and biological flows. Although the first are mainly external flows and the latter internal ones, there are many similarities between the two, such as self-sustained oscillations during flutter of an elastically mounted wing and the vibrating walls of a blood vessel, vortex shedding from solid bodies immersed in a fluid stream (e.g., buildings, vehicles) and downstream of a blood vessel bifurcation or stenosis, jet-like flows downstream of pitching wings and downstream of vibrating vocal folds during sound and voice production, etc.

Researchers will be able to publish their work on the aforementioned topics employing various measurement techniques, either traditional, e.g., PIV, LDA, HWA, or new ones, revealing flow details which could be beneficial for understanding the physics of the examined flows and provide useful information to those who work in CFD.

Prof. Dr. Dimitrios Mathioulakis
Guest Editor

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Keywords

  • experimental fluid mechanics
  • PIV–LDA–HWA
  • unsteady flows
  • forced/self-sustained oscillations
  • wing flutter
  • flow instabilities

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Published Papers (2 papers)

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Research

13 pages, 5997 KiB  
Article
Flow Dynamics in a Model of a Left Ventricle with Different Mitral Valve Orientations
by Ghassan Maraouch and Lyes Kadem
Fluids 2021, 6(12), 428; https://doi.org/10.3390/fluids6120428 - 26 Nov 2021
Viewed by 2246
Abstract
The formation of vortex rings at valve leaflets during ventricular inflow has been a topic of interest for many years. It is generally accepted nowadays that the purpose of vortex rings is to conserve energy, reduce the workload on the heart, and minimize [...] Read more.
The formation of vortex rings at valve leaflets during ventricular inflow has been a topic of interest for many years. It is generally accepted nowadays that the purpose of vortex rings is to conserve energy, reduce the workload on the heart, and minimize particle residence time. We investigated these claims by testing three different levels of annulus angle for the mitral valve: a healthy case, a slightly angled case (20°), and a highly angled case (46°). Circulation was determined to be reversed in the non-healthy case, with a dominant counterclockwise rotation instead of clockwise. Viscous energy dissipation was highest in the slightly angled case, followed by the healthy case and then the highly angled case. A Lagrangian analysis demonstrated that the healthy case resulted in the least amount of stasis, requiring eight cardiac cycles to evacuate 99% of initial ventricle volume compared to the 16 and 13 cardiac cycles required by the slightly angled and highly angled cases, respectively. Full article
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18 pages, 11137 KiB  
Article
Aerodynamic Study of a NACA 64418 Rectangular Wing under Forced Pitching Motions
by Dimitris Gkiolas and Dimitrios Mathioulakis
Fluids 2021, 6(11), 394; https://doi.org/10.3390/fluids6110394 - 2 Nov 2021
Cited by 2 | Viewed by 3244
Abstract
The aerodynamic behavior of a pitching NACA 64418 rectangular wing was experimentally studied in a subsonic wind tunnel. The wing had a chord c = 0.5 m, a span which covered the distance between the two parallel tunnel walls and an axis of [...] Read more.
The aerodynamic behavior of a pitching NACA 64418 rectangular wing was experimentally studied in a subsonic wind tunnel. The wing had a chord c = 0.5 m, a span which covered the distance between the two parallel tunnel walls and an axis of rotation 0.35 c far from the leading edge. Based on pressure distribution and flow visualization, intermittent flow separation (double stall) was revealed near the leading edge suction side when the wing was stationary, at angles higher than 17° and Re = 0.5 × 106. Under pitching oscillations, aerodynamic loads were calculated by integrating the output data of fast responding surface pressure transducers for various mean angles of attack (αm (max) = 15°), reduced frequencies (kmax = 0.2) and angle amplitudes Δα in the interval [2°, 8°]. The impact of the above parameters up to Re = 0.75 × 106 on the cycle-averaged lift and pitching moment loops is discussed and the cycle aerodynamic damping coefficient is calculated. Moreover, the boundaries of the above parameters are defined for the case that energy is transferred from the flow to the wing (negative aerodynamic damping coefficient), indicating the conditions under which aeroelastic instabilities are probable to occur. Full article
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