Wind Tunnel Setup Research Articles

Wind Tunnel Studies of Temperature Dependence and Behavior of Butterflies in the Context of Habitat Edges

ABSTRACT. Wind tunnel studies provide a valuable experimental approach that can be used to investigate the influence of specific environmental parameters and to make generalizations about insect behavior. In this study, we designed an experiment to test the sensitivity of butterflies to isolated environmental parameters in the context of understanding edge responses. We tested the behavior of 21 different butterfly species in response to certain stimuli, including food source, feeder color, temperature, and UV light. Certain butterfly species (e.g. Heliconius melpomene and Papilio polytes) were particularly active in the wind tunnel setup. All butterfly species tested preferred blue feeders over white, yellow or pink. Investigation of the UV content of the different feeders and the butterflies' preferred nectar plant showed a similar wavelength response, which could indicate a UV preference in butterflies. We also observed species-dependent temperature preferences. Papilio lowii had a significant preferen...

To be in time: egg deposition enhances plant-mediated detection of young caterpillars by parasitoids.

Animals use information from their environment while foraging for food or prey. When parasitic wasps forage for hosts, they use plant volatiles induced by herbivore activities such as feeding and oviposition. Little information is available on how wasps exploit specific plant volatiles over time, and which compounds indicate changes in host quality. In experiments investigating the role of herbivore-induced plant volatiles in wasp foraging, induction of plant response is usually achieved by placing larvae on clean plants instead of allowing the natural sequence of events: to let eggs deposited by the herbivore develop into larvae. We compared the attraction of the parasitoid Cotesia glomerata to volatiles emitted by black mustard (Brassica nigra) plants induced by eggs and successive larval stages of the Large Cabbage White butterfly (Pieris brassicae) to the attraction of this parasitoid to black mustard plant volatiles induced only by larval feeding in a wind tunnel setup. We show that wasps are attracted to plants infested with eggs just before and shortly after larval hatching. However, wasp preference changed at later time points towards plants induced only by larval feeding. These temporal changes in parasitoid attraction matched with changes in the chemical compositions of the blends of plant volatiles. Previous studies have shown that host quality/suitability decreases with caterpillar age and that P. brassicae oviposition induces plant defences that negatively affect subsequently feeding caterpillars. We investigated parasitoid performance in hosts of different ages. Wasp performance was positively correlated with preference. Moreover, parasitism success decreased with time and host stage. In conclusion, the behaviour of Cotesia glomerata is fine-tuned to exploit volatiles induced by eggs and early host stages that benefit parasitoid fitness.

Wind Tunnel Investigation of the Near-wake Flow Dynamics of a Horizontal Axis Wind Turbine

Experiments conducted in a large wind tunnel set-up investigate the 3D flow dynamics within the near-wake region of a horizontal axis wind turbine. Particle Image Velocimetry (PIV) measurements quantify the mean and turbulent components of the flow field. Measurements are performed in multiple adjacent horizontal planes in order to cover the area behind the rotor in a large radial interval, at several locations downstream of the rotor. The measurements were phase-locked in order to facilitate the re-construction of the threedimensional flow field. The mean velocity and turbulence characteristics clearly correlate with the near-wake vortex dynamics and in particular with the helical structure of the flow, formed immediately behind the turbine rotor. Due to the tip and root vortices, the mean and turbulent characteristics of the flow are highly dependent on the azimuth angle in regions close to the rotor and close to the blade tip and root. Further from the rotor, the characteristics of the flow become phase independent. This can be attributed to the breakdown of the vortical structure of the flow, resulting from the turbulent diffusion. In general, the highest levels of turbulence are observed in shear layer around the tip of the blades, which decrease rapidly downstream. The shear zone grows in the radial direction as the wake moves axially, resulting in velocity recovery toward the centre of the rotor due to momentum transport.

Influence of surface imperfections caused by thruster elements on the aerodynamics of a supersonic projectile

Pulsed side jet thrusters can be used to correct the trajectory of supersonic projectiles. After their time-of-action, these pyrotechnical thrusters leave a hole in the shaft, which sometimes also features a protuberance or burr at its rim. The current work quantifies the aerodynamic interference caused by this sub-boundary-layer disturbance by means of 3-axis-force balance measurements in a supersonic wind tunnel at Mach 3 at angles of attack between 0 and 10 degrees. Supplementary numerical time- and scale-resolving detached eddy simulations (DES) of the wind tunnel setup as well as basic theoretical correlations also support the experimental result that aerodynamic coefficients change by less than 2%, if the hole diameter is in the order of half a calibre and surface deformations protrude less than 2.5% of the calibre.

Formation of Simple Nitriles upon Glucosinolate Hydrolysis Affects Direct and Indirect Defense Against the Specialist Herbivore, Pieris rapae

The glucosinolate-myrosinase system, found in plants of the order Brassicales, has long been considered an effective defense system against herbivores. The defensive potential of glucosinolates is mainly due to the products formed after myrosinase-catalyzed hydrolysis upon tissue damage. The most prominent hydrolysis products, the isothiocyanates, are toxic to a wide range of organisms, including herbivorous lepidopterans. In contrast, little is known about the biological activities of alternative hydrolysis products such as simple nitriles and epithionitriles that are formed at the expense of isothiocyanates in the presence of epithiospecifier proteins (ESPs). Here, we used transgenic Arabidopsis thaliana (Brassicaceae) plants overexpressing ESP (35S:ESP plants) to investigate the effects of simple nitriles on direct and indirect defense against the specialist cabbage white butterfly Pieris rapae L. (Lepidoptera, Pieridae). In the 35S:ESP plants, glucosinolates are hydrolyzed mainly to simple nitriles upon tissue disruption, while isothiocyanates are the predominant hydrolysis products in Columbia-0 (Col-0) wild-type plants. The parasitoid Cotesia rubecula (Hymenoptera, Braconidae), a specialist on P. rapae larvae, was significantly more attracted to P. rapae-infested 35S:ESP plants than to P. rapae-infested Col-0 wild-type plants in a wind tunnel setup. Furthermore, female P. rapae butterflies laid more eggs on Col-0 wild-type plants than on 35S:ESP plants when the plants had been damaged previously. However, when given a choice to feed on 35S:ESP or Col-0 plants, caterpillars did not discriminate between the two genotypes. Growth rate and developmental time were not significantly different between caterpillars that were reared on 35S:ESP or Col-0 plants. Thus, the production of simple nitriles instead of isothiocyanates, as catalyzed by ESP, can promote both direct and indirect defense against the specialist herbivore P. rapae.

PIV technique implementation for wind mapping in complex topographies

An experimental study was conducted to demonstrate PIV's capability to provide a detailed characterization of the flow field over complex topographic terrain in a large boundary layer wind tunnel setup. Two-dimensional velocity fields were measured in horizontal and vertical planes over a 1:3000 scaled topographic model. The non-uniform seed distribution was found to be a major issue which could affect the PIV velocity vectors. A novel scheme was developed to automatically detect the regions with low seed density and exclude them from further analysis. The mean and turbulent velocities obtained from PIV and previous hotwire measurements are compared and show good agreement. The study shows that PIV can be successfully used to measure flow over complex geometries in large wind tunnel setups, enabling the flow structure to be mapped with a very high spatial resolution.

Wind-Tunnel Setup for Investigations of Normal Shock Wave/Boundary Layer Interaction Control

The use of wind-tunnel setup for study of normal shock wave/boundary layer interaction control, was investigated. The rectangular working section that was 114 mm wide, and 178 mm high at the straight downstream of the nozzle was used. The incoming airflow was partitioned by a plate of 6 mm thickness to overcome the problem of shock wave instability. The height of the upper and lower passage was maintained at 91 and 122 mm respectively. The incoming boundary layer thickness was 5.7 mm and the Reynolds number based on boundary-layer displacement thickness was approximately 25,000. It was observed that shock can be located above 3-D bump and large ?-shock structure whose front shock leg starts at the onset of control cab be analyzed. Result shows that wind-tunnel setup can be used to test various types of shock control at positions where conventional setups are unable to hold shock system due to shock instability.

Screen characterization under fan induced swirl conditions

In this paper, loss coefficients are determined for a fine and a coarse EMC screen placed in a swirling flow. In an axisymmetric swirl generator test rig the screen performance is measured under well-defined swirling conditions. Based on velocity and pressure measurements on one hand and on axial and tangential momentum balances on the other, directional loss coefficients are obtained. It is shown that in this way in-plane coefficients can be accurately determined. In contrast, the normal component can more accurately be determined in a basic wind-tunnel setup. Subsequently, the obtained coefficients are used in a commercial computational fluid dynamics code using a volume resistance model for the screens. Validation of the numerical results against fan measurements shows that using in-plane coefficients is superior to one-dimensional models. Indeed, in the former case the effect of the screen on the tangential velocity component is well predicted by the model, whereas for the latter only the axial velocity components are affected. Finally, a full rack simulation reveals that component temperatures strongly depend on local flow phenomena. Therefore, it can be concluded that fan induced swirl should always be modeled and that screen models should account for in-plane loss coefficients

The Second International Vortex Flow Experiment (VFE-2): Objectives and first results

This paper presents the objectives for the new International Vortex Flow Experiment (VFE-2), and its organization within an RTO Task Group is outlined. The available wind tunnel models as well as the applied experimental techniques are described briefly. Results of Pressure-Sensitive Paint (PSP) measurements at DLR Goettingen showed a first insight into the flow mechanisms. Additional CFD results from numerical solutions of the RANS equations as calculated by EADS Munich led to an initial understanding of the flow details and allowed a proper wind tunnel set-up for the Particle Image Velocimetry (PIV) experiments at DLR Goettingen. These measurements showed the details of the flow field in the vicinity of the wing in excellent agreement with the CFD results.

Herbivore-Induced Plant Volatiles Mediate In-Flight Host Discrimination by Parasitoids

Herbivore feeding induces plants to emit volatiles that are detectable and reliable cues for foraging parasitoids, which allows them to perform oriented host searching. We investigated whether these plant volatiles play a role in avoiding parasitoid competition by discriminating parasitized from unparasitized hosts in flight. In a wind tunnel set-up, we used mechanically damaged plants treated with regurgitant containing elicitors to simulate and standardize herbivore feeding. The solitary parasitoid Cotesia rubecula discriminated among volatile blends from Brussels sprouts plants treated with regurgitant of unparasitized Pieris rapae or P. brassicae caterpillars over blends emitted by plants treated with regurgitant of parasitized caterpillars. The gregarious Cotesia glomerata discriminated between volatiles induced by regurgitant from parasitized and unparasitized caterpillars of its major host species, P. brassicae. Gas chromatography-mass spectrometry analysis of headspace odors revealed that cabbage plants treated with regurgitant of parasitized P. brassicae caterpillars emitted lower amounts of volatiles than plants treated with unparasitized caterpillars. We demonstrate (1) that parasitoids can detect, in flight, whether their hosts contain competitors, and (2) that plants reduce the production of specific herbivore-induced volatiles after a successful recruitment of their bodyguards. As the induced volatiles bear biosynthetic and ecological costs to plants, downregulation of their production has adaptive value. These findings add a new level of intricacy to plant-parasitoid interactions.

An Active Flap Deployment System for Blade–Disturbance Interaction Alleviation

A new, actively deployable trailing edge flap system is introduced and an experimental investigation is undertaken to determine its effects on the disturbances created during blade–disturbance interactions (BDI), with blade–vortex interaction (BVI) alleviation being the ultimate objective. Experimental tests were conducted using a two-dimensional (2D) wind tunnel setup incorporating a pressure instrumented airfoil section with a deployable 20% trailing edge flap and an upstream vortex generator to produce the disturbance. Results of this study showed that the disturbances, caused by BDI events, to the pressure distribution over the airfoil occur mostly at the leading edge. Carefully synchronized deployment of the trailing edge flap during BDI events resulted in a reduction of this pressure disturbance. The aeroelastic response of the active flap was modeled via unsteady linear theory and the model was validated experimentally. The aeroelastic model shows good agreement with experimental results, which supports its use as a preliminary design tool for the actuation parameters of the active flap system.

Analysis of Flow Conditions in Freejet Experiments for Studying Airfoil Self-Noise

A new set of mean wall pressure data has been collected on a controlled diffusion airfoil at a chord Reynolds number of 1.2 £ £105 in a freejet anechoic wind tunnel. Comparisons of the experimental data with Reynoldsaveraged Navier‐ Stokes (RANS) simulationsin freeairshow signie cant e owe eld and pressure loading differences, indicatingsubstantialjetinterferenceeffects.Toanalyzetheseeffects,asystematicRANS-basedcomputationale uid dynamicsstudyoftheexperimentale owconditionshasbeencarriedout,whichquantie esthestrongine uenceofthe e nite jet (nozzle) width on the aerodynamic loading and e ow characteristics. When the jet width is not sufe ciently large compared to the frontal wetted area of the airfoil, the airfoil pressure distribution is found to be closer to the distribution on a cascade than that of an isolated proe le. The airfoil lift is signie cantly reduced. Accounting for the actual wind-tunnel setup recovers the wall pressure distribution on the airfoil without further empirical angle-of-attack corrections. These jet interference effects could be responsible for the discrepancies among some earlier experimental and computational studies of airfoil self-noise. They should be accounted for in future noise computations to ensure that the experimental e ow conditions are simulated accurately.

Study on Oxidation Mechanism of Nitrogen Monoxide in Indoor Environment

AbstractWith the aid of wind‐tunnel experimental setup, the possibilities that nitrogen monoxide (NO) is oxidized to nitrogen dioxide (NO2) in various environments were studied, which include indoor, outdoor and darkroom conditions. By comparing their effects, a conclusion can be drawn that NO can be oxidized to NO2 in indoor environment with a low rate, and micro amount of ozone, propylene and methane can accelerate the reaction: 2NO+ O2·NO2. The initial concentration of NO has effect on the oxidation rate. When the initial concentration of NO ranges between 500 and 900 μg/L, natural logarithm of initial rate and natural logarithm of initial concentration have a good linear relation, so do m(1/[NO]) and the time (t). Besides mat, the possible oxidation mechanism of indoor NO has also been studied.