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[en] DASH+Wings is a small hexapedal winged robot that uses flapping wings to increase its locomotion capabilities. To examine the effects of flapping wings, multiple experimental controls for the same locomotor platform are provided by wing removal, by the use of inertially similar lateral spars, and by passive rather than actively flapping wings. We used accelerometers and high-speed cameras to measure the performance of this hybrid robot in both horizontal running and while ascending inclines. To examine consequences of wing flapping for aerial performance, we measured lift and drag forces on the robot at constant airspeeds and body orientations in a wind tunnel; we also determined equilibrium glide performance in free flight. The addition of flapping wings increased the maximum horizontal running speed from 0.68 to 1.29 m s−1, and also increased the maximum incline angle of ascent from 5.6° to 16.9°. Free flight measurements show a decrease of 10.3° in equilibrium glide slope between the flapping and gliding robot. In air, flapping improved the mean lift:drag ratio of the robot compared to gliding at all measured body orientations and airspeeds. Low-amplitude wing flapping thus provides advantages in both cursorial and aerial locomotion. We note that current support for the diverse theories of avian flight origins derive from limited fossil evidence, the adult behavior of extant flying birds, and developmental stages of already volant taxa. By contrast, addition of wings to a cursorial robot allows direct evaluation of the consequences of wing flapping for locomotor performance in both running and flying.
[en] The basic characteristics are given of two types of precision devices for measuring probe adjustment in the flow area of a wind tunnel with return circuit: a Cartesian coordinate device, electrically controlled and with two degrees of freedom, and another electrically controlled device with remote electric position reading and one degree of freedom. The accuracy of the measuring probe adjustment in the tunnel is 0.01 mm in both directions in the first type and 0.05 mm in the second type. (F.M.)
[en] Composite corrugated structures are known for their anisotropic properties. They exhibit relatively high stiffness parallel (longitudinal) to the corrugation direction and are relatively compliant in the direction perpendicular (transverse) to the corrugation. Thus, they offer a potential solution for morphing skin panels (MSPs) in the trailing edge region of a wing as a morphing control surface. In this paper, an overview of the work carried out by the present authors over the last few years on corrugated structures for morphing skin applications is first given. The second part of the paper presents recent work on the application of corrugated sandwich structures. Panels made from multiple unit cells of corrugated sandwich structures are used as MSPs in the trailing edge region of a scaled morphing aerofoil section. The aerofoil section features an internal actuation mechanism that allows chordwise length and camber change of the trailing edge region (aft 35% chord). Wind tunnel testing was carried out to demonstrate the MSP concept but also to explore its limitations. Suggestions for improvements arising from this study were deduced, one of which includes an investigation of a segmented skin. The overall results of this study show that the MSP concept exploiting corrugated sandwich structures offers a potential solution for local morphing wing skins for low speed and small air vehicles
[en] A newly constructed towing wind tunnel facility is introduced. In this wind tunnel, unlike a conventional wind tunnel, a testing model moves in still air on a testing track. This towing wind tunnel facility can therefore simulate highly complex flow between steady ground and a moving model without using a moving belt system. The performance of this facility is first explained. Some results of wings in ground effect experiments and boundary-layer transition experiments obtained using this facility are then given. From these results, we conclude that this facility has enough performance for complex flow testing. (invited paper)
[en] Ecological effects are less if plant recovery occurs. - The present study was conducted to determine the effects of airborne herbicides on the photosynthesis and growth of non-target plants. Sunflowers at different growth stages were used as test plants and exposed for 24 h in a wind tunnel to a range of concentrations of bromoxynil-octanoate and metribuzin. The quantum yield (phiPSII) and the dry weight were used as response parameters. Results indicate that young sunflower plants are affected by sublethal concentrations of both herbicides, whereas metribuzin proved to be more phytotoxic. Bromoxynil-octanoate and metribuzin concentrations >0.265 and >0.135 μg/m3 impair the photosynthetic activity of exposed leaves and concentrations >0.780 and >0.641 μg/m3 of leaves developed after exposure. Effects on dry weight indicate that younger plants were more susceptible, whereby the response to metribuzin proved to be more dependent on growth stage. Based on these results and considering herbicide concentrations in ambient air, there is a reasonable probability that non-target plants are temporarily at risk of being affected
[en] A long-term investigation is presently underway to assess the overall performance of the modern design of fin keels for sailing yachts. An ultimate goal is to determine the specific advantages for such designs with respect to a centre-board configuration with outside ballast. The present preliminary studies were carried out to determine the basic performance of a typical fin keel shape for various values of leeway angle. A second aspect was to determine the effect upon this baseline performance of a number of endplates of varying sizes and shapes. (author)
[en] Highlights: ► We describe the flow around rectangular bluff bodies at different angles of attack. ► We identify a region of angles of attack where the lift remains roughly constant. ► The constant-lift region is characterized by three-dimensional (3-D) flow. ► We develop an empirical curve fit to predict the constant-lift region. ► The empirical curve fit is valuable for modeling and simulation purposes. -- Abstract: Using data present in the literature from wind tunnel testing of semi-infinite and infinite rectangular bluff bodies at angle of attack, we develop a simple relation to predict the range of angles of attack where the lift remains approximately constant. This prediction is useful for researchers attempting to develop simplified models of the forces on rectangular bluff bodies. Additionally, prior work has shown that this region of the lift curve is characterized by complex three-dimensional flow, which has consequences for computational simulations.
[en] This paper gives first results of the newly established wind-tunnel/soil-column experiment, which is designed to study reemission of HTO from a soil-column into the air. Reemission is determined by time-dependent sampling of air-HTO during the experimental run and by evaluation of the soil-HTO profile after the experiment. All relevant micrometeorological parameters can be simulated and measured continuously. As a first approach to parameterize reemission the results presented here were obtained under constant windtunnel condiditions starting from a homogeneously HTO-labelled soil column. The results are in good agreement to previous findings of field experiments. (orig./DG)
[de]Wie Untersuchungen im Zusammenhang mit den Feldexperimenten in Frankreich und Canada gezeigt haben, ist die Reemission von Tritium nach Ablagerung am Boden ein Prozess von hoher Dosisrelevanz, dessen Abhaengigkeiten von mikrometeorologischen und bodenphysikalischen Bedingungen unzureichend bekannt sind. Zur Parameterisierung dieses Prozesses werden Untersuchungen mit Bodensaeulen in einem Windkanal durchgefuehrt, wobei die Reemission unter kontrollierten Umweltbedingungen bestimmt werden kann. Die ersten Ergebnisse zeigen bereits, dass entgegen bisheriger Annahmen und Modellansaetzen die Reemissionsrate nicht konstant ist, sondern mit fortschreitendem Prozess unter konstanten Untersuchungsbedingungen abnimmt. Die experimentellen HTO-Bodenprofile konnten mit einem mathematischen Ansatz in guter Naeherung beschrieben werden. (orig./DG)
[en] Highlights: ► We experimentally evaluated the performances of cellulosic pads. ► A number of experiments have been done in a wind tunnel. ► The results showed that cooling efficiency improves with decrease of air velocity and flute size. ► Water consumption increases with the increase of air velocity. ► Cooling efficiency of various pads was also compared. - Abstract: The purpose of this study was to evaluate the performances of cellulosic pads made out of Kraft and NSSC corrugated papers in three flute sizes, experimentally. A number of experiments have been done in a wind tunnel in order to evaluate the cooling efficiency and water consumption as a function of air velocity. The tests were carried out at three levels of air velocity (1.8, 2.25, and 2.67 ms−1) for three flute sizes of Kraft and NSSC corrugated papers (2.5, 3.5, and 4.5 mm). Analysis of the results indicated that cooling efficiency improves with decrease of air velocity and flute size of corrugated papers; however, water consumption increases with the increase of air velocity. The results were compared with each other and it was shown that the cellulosic pad made out of Kraft paper with 2.5 mm flute size has the highest performance (92%) at 1.8 ms−1 air velocity in comparison with the other cellulosic pads.
[en] Highlights: • First paper studying Markovian properties of turbulent boundary layers. • Markovian nature of turbulence evolves across the boundary layer. • Logarithmic behavior below the log-layer. • A constant behavior across the log-layer. • Connection between the spectral gap and Markovian nature of turbulence. Markovian properties of the turbulent velocity increments in a flat plate boundary layer at Re of are investigated using hot-wire anemometry measurements of the streamwise velocity component in a wind tunnel. Increments of the longitudinal velocities at different wall-normal positions show that the flow exhibits Markovian properties when the separation between different scales, or the Markov–Einstein coherence length, is on the order of the Taylor microscale, . The results indicate that Markovian nature of turbulence evolves across the boundary layer showing certain characteristics pertaining to the distance to the wall. The connection between the Markovian properties of turbulent boundary layer and existence of the spectral gap is explored. Markovianity of the process is also discussed in relation to the nonlocal nonlinear versus local nonlinear transfer of energy, triadic interactions and dissipation.