Near-field experiments on tip vortices at Mach 3.1

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 750-753
Author(s):  
Frank Y. Wang ◽  
Pasquale M. Sforza
Keyword(s):  
Field Experiments ◽  
Near Field ◽  
Tip Vortices

Near-Field Experiments on Tip Vortices at Mach 3.1

AIAA Journal ◽  
10.2514/2.172 ◽  
1997 ◽  
Vol 35 (4) ◽  
pp. 750-753 ◽  
Author(s):  
Frank Y. Wang ◽  
Pasquale M. Sforza
Keyword(s):  
Field Experiments ◽  
Near Field ◽  
Tip Vortices

scholarly journals Simulation and Experimental Study of the Near Field Probe in the Form of a Folded Dipole for Measuring Glucose Concentration

2021 ◽  
Vol 11 (12) ◽  
pp. 5415
Author(s):  
Aleksandr Gorst ◽  
Kseniya Zavyalova ◽  
Aleksandr Mironchev ◽  
Andrey Zapasnoy ◽  
Andrey Klokov
Keyword(s):  
Experimental Measurement ◽  
Glucose Concentration ◽  
Field Experiments ◽  
Near Field ◽  
Vector Network Analyzer ◽  
Human Hand ◽  
Physical Parameters ◽  
Network Analyzer ◽  
Frequency Range ◽  
Average Deviation

The article investigates the near-field probe of a special design to account for changes in glucose concentration. The probe is designed in such a way that it emits radiation in both directions from its plane. In this paper, it was proposed to modernize this design and consider the unidirectional emission of the probe in order to maximize the signal and reduce energy loss. We have done extensive research for both bidirectional and unidirectional probe designs. Numerical simulations and field experiments were carried out to determine different concentrations of glucose (0, 4, 5.3, 7.5 mmol/L). Numerical modeling of a unidirectional probe showed that the interaction of radiation generated by such a probe with a multilayer structure simulating a human hand showed a better result and high sensitivity compared to a bidirectional probe. Further, based on the simulation results, a phantom (physical model) of a human hand was recreated from layers with dielectric properties as close as possible to the properties of materials during simulation. The probe was constructed from a copper tube and matched both the geometric and physical parameters of the model. The experimental measurement was carried out using a vector network analyzer in the frequency range 2–10 GHz. The experimental measurement was carried out using a vector network analyzer in the frequency range 2–10 GHz for the unidirectional and bidirectional probes. Further, the results of the experiment were compared with the results of numerical simulation. According to the results of multiple experiments, it was found that the average deviation between the concentrations was 2 dB for a unidirectional probe and 0.4 dB for a bidirectional probe. Thus, the sensitivity of the unidirectional probe was 1.5 dB/(mmol/L) for the bidirectional one 0.3 dB/(mmol/L). Thus, the improved design of the near-field probe can be used to record glucose concentrations.

Near field dynamics of wing tip vortices

2001 ◽  
Author(s):  
Lavi Zuhal ◽  
Morteza Gharib
Keyword(s):  
Near Field ◽  
Tip Vortices ◽  
Wing Tip

Numerical Experiments for Flow Around a Ducted Tip Hydrofoil

2002 ◽  
Author(s):  
Hildur Ingvarsdo´ttir ◽  
Carl Ollivier-Gooch ◽  
Sheldon I. Green
Keyword(s):  
Turbulence Model ◽  
Vortex Core ◽  
Vortex Flow ◽  
Computational Study ◽  
Near Field ◽  
Vortex Formation ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Computational Studies ◽  
Tip Vortices

The performance and cavitation characteristics of marine propellers and hydrofoils are strongly affected by tip vortex behavior. A number of previous computational studies have been done on tip vortices, both in aerodynamic and marine applications. The focus, however, has primarily been on validating methods for prediction and advancing the understanding of tip-vortex formation in general, rather than showing effects of tip modifications on tip vortices. Studies of the most relevance to the current work include computational studies by Dacles-Mariani et al. (1995) and Hsiao and Pauley (1998, 1999). Daeles-Mariani et al. carried out interactively a computational and experimental study of the wingtip vortex in the near field using a full Navier-Stokes simulation, accompanied with the Baldwin-Barth turbulence model. Although they showed improvement over numerical results obtained by previous researchers, the tip vortex strength was underpredicted. Hsiao and Pauley (1998) studied the steady-state tip vortex flow over a finite-span hydrofoil, also using the Baldwin-Barth turbulence model. They were able to achieve good agreement in pressure distribution and oil flow pattern with experimental data and accurately predict vertical and axial velocities of the tip vortex core within the near-field region. Far downstream, however, the computed flow field was overly diffused within the tip vortex core. Hsiao and Pauley (1999) also carried out a computational study of the tip vortex flow generated by a marine propeller. The general characteristics of the flow were well predicted but the vortex core was again overly diffused.

Investigation of heating effects in near-field experiments with luminescent organic semiconductors

2004 ◽  
Vol 147 (1-3) ◽  
pp. 165-169 ◽  
Author(s):  
G. Latini ◽  
A. Downes ◽  
O. Fenwick ◽  
A. Ambrosio ◽  
M. Allegrini ◽  
...  
Keyword(s):  
Organic Semiconductors ◽  
Field Experiments ◽  
Near Field ◽  
Heating Effects

scholarly journals Coherence of Raman light arises from disorder

2019 ◽  
Vol 52 (382) ◽  
pp. MISC1-MISC3
Author(s):  
Barbara Fazio ◽  
Alessia Irrera
Keyword(s):  
Raman Scattering ◽  
Inelastic Scattering ◽  
Coming Out ◽  
Field Experiments ◽  
Physical Phenomenon ◽  
Near Field ◽  
Fast Time ◽  
Optical Information ◽  
Scattering Media ◽  
Scattering Events

Light propagation in random materials is a topic of great interest for the scientific community, not only for the possible relevant applications in the fields of photonics and renewable energies but even more since it allows to unveil new fascinating phenomena related to wave physics. Among these physical events, the most robust and always surviving any ensemble average is the coherent backscattering of light (CBS). It is a very subtle interference effect in disordered scattering media (such as semiconductor powders or micro-particle suspensions like milk or fog), in which wave coherence is preserved even after a very large number of random scattering events, eventually manifesting as a maximum of interference in the exact backscattering direction. CBS is related to the well-defined wave character and to the preservation of the optical information, for this reason it has been so far experimentally observed and theoretically studied only for elastic scattering, while the occurrence of inelastic scattering is known to reduce the degree of coherence in the diffusion process, affecting the visibility of the effect. Fazio et al. (2017) have demonstrated that this experimental evidence surprisingly survives also for the inelastic light scattering, such as the spontaneous Raman process, as long as the optical information of the propagating wave is retained. In this kind of inelastic scattering events, light loses a small part of its energy by slightly changing wavelength. Its phase coherence, however, is preserved for a very short time, thus making interference between Raman scattered waves still possible. The observed maximum of interference in the exact backscattering direction is therefore a signature of the coherent nature of individual Raman scattering processes. To date, indications on the coherence properties of Raman scattering have been reported only by looking at the nanoscopic scale, through complex near-field experiments making use of very sharp tips or through ultra-fast time resolved techniques. This time, however, we did not rely on complex experiments or advanced techniques. Conversely, the combination of an accurate experimental procedure and the unique structural properties of a silicon-based material were the only simple ingredients for the observation of a new unexpected physical phenomenon. In particular, a dense forest of ultrathin silicon wires arranged in a disordered fashion, where light waves bounce back and forth countless times before coming out, was the medium that allowed us to reveal this new effect, which opens the way for new and important discoveries.

scholarly journals Comparison of Near- and Far-Field Supercell Inflow Environments Using Radiosonde Observations

2018 ◽  
Vol 146 (8) ◽  
pp. 2403-2415 ◽  
Author(s):  
Andrew R. Wade ◽  
Michael C. Coniglio ◽  
Conrad L. Ziegler
Keyword(s):  
Field Experiments ◽  
Near Field ◽  
Static Stability ◽  
Far Field ◽  
Field Phase ◽  
Convective Storms ◽  
Close Range ◽  
Supercell Thunderstorms

Abstract A great deal of research focuses on how the mesoscale environment influences convective storms, but relatively little is known about how supercells modify the nearby environment. Soundings from three field experiments are used to investigate differences in the near and far inflow of supercell thunderstorms. Close-range soundings in the near inflow of supercells are compared to near-simultaneous soundings released farther away (but still within inflow). Several soundings from the second field phase of the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) supplement the Mesoscale Predictability Experiment (MPEX/MiniMPEX) dataset, resulting in 28 near–far inflow pairs from a wide variety of tornadic and nontornadic supercells. The focus of this study is on a comparison of a subset of 12 near–far inflow pairs taken near tornadic supercells and 16 near–far inflow pairs taken near nontornadic supercells. Similar values of 0–1-km storm-relative helicity (SRH01) are found in the far field of the tornadic and nontornadic supercells, possibly as a result of a difference in mean diurnal timing. However, SRH01 is found to increase substantially in the near field of the tornadic supercells, but not the nontornadic supercells. Differences in the thermodynamic environment include greater moisture above the ground in the far field of the tornadic supercells (despite similar near-ground moisture in both the tornadic and nontornadic subsets) and a subtle increase in static stability near the surface in the nontornadic near inflow.

FROM BLOWOUT TO BEACH: AN INTEGRATED MODELING APPROACH

2014 ◽  
Vol 2014 (1) ◽  
pp. 919-932
Author(s):  
Piers Chapman ◽  
Scott Socolofsky ◽  
Robert Hetland
Keyword(s):  
Gulf Of Mexico ◽  
Field Experiments ◽  
Oil And Gas ◽  
North Atlantic Ocean ◽  
Near Field ◽  
Transformation Model ◽  
Navier Stokes ◽  
Small Scale ◽  
Nested Model ◽  
Research Initiative

ABSTRACT As part of the response to the BP Deepwater Horizon spill in 2010, we have been funded by the Gulf of Mexico Research Initiative to construct a nested model suite that can follow an oil particle from its first release to its arrival on a shoreline, taking into account natural rates of mixing and degradation of the oil components. The model suite incorporates (at increasing levels of resolution) a coupled ocean-atmosphere model of the full Gulf of Mexico and North Atlantic Ocean, a deep Gulf of Mexico model, a regional model of the Texas-Louisiana shelf, a 3D, non-hydrostatic bay model, a 3D Navier-Stokes model of the spill plume, and a particle tracking and transformation model for dispersed and dissolved oil and gas fate and transport integrated within the full flow domain. The models are supported by a series of laboratory and field experiments, including studies of single droplets, with and without dispersant, plumes, a deep-sea tracer release experiment and bubble releases to simulate an underwater blowout. The laboratory experiments will improve modeling of small-scale, near-field processes such as bubble and droplet formation, dissolution, droplet-turbulence interaction, and evaporation and dispersion at the air-sea interface. We show how the models are linked and how we are making progress towards the complete nested model suite, which will be available for use in future spills.

Effect of counter-rotating vortices on the development of aircraft wakes

2004 ◽  
Vol 108 (1089) ◽  
pp. 585-592 ◽  
Author(s):  
A. Panaras ◽  
S. G. Voutsinas
Keyword(s):  
Near Field ◽  
Small Radius ◽  
Particle Model ◽  
Large Radius ◽  
Two Dimensional ◽  
Vortex System ◽  
Tip Vortices ◽  
Initial Vorticity ◽  
Aircraft Wake ◽  
Triangular Wing

AbstractA two-dimensional vortex particle model is used for studying the development of the vortex wake generated by the wing of an aircraft in the Trefftz plane. Two-dimensional, finite-area vortex structures simulate the initial vorticity distribution at a near-field cross-section of the wing, as provided by either measurements or simulations. The code is used for studying the effect of weak or strong counter-rotating vortices on the development of an aircraft wake. Application in a three-vortex configuration, consisting of the tip and flap vortices, plus a weak negative vorticity sheet lying between them, supports the hypothesis of Graham that the merging of the tip and flap vortices is prevented, because in such an arrangement the counter-rotating vorticity sheet is wrapped around the primary vortices. The present results indicate that even in the far field the tip and flap vortices remain distinct and follow a helical trajectory with large-pitch and small-radius. The code is next applied to the two-vortex system of Savas’s triangular wing, in which the circulation of the flap vortex is comparable to that of the tip. Although a 2D analysis is inappropriate for stability analysis it is still useful for a quick qualitative investigation. Results indicate that the flap and tip vortices follow a helical trajectory with large-pitch but also very large radius. During one period, the flap vortex covers a span wise distance equal to the wing span. Such a flow has not been observed in flight or in laboratory tests. Actually, Ortegaet al, who studied experimentally the triangular wing of O. Savas, found out that before concluding one full spiral, the vortices are literally destroyed (rapid spreading of their vorticity) by an instability mechanism.

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