Journal of Visualization - Volume 2, issue 3-4

Authors: Kobayashi, Toshio

Article Type: Other

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 205-205, 2000

Article Type: Other

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 207-212, 2000

Authors: Elavarasan, R. | Venkatakrishnan, L. | Krothapalli, A. | Lourenco, L.

Article Type: Research Article

Abstract: The characteristics of supersonic impinging jets are investigated using Particle Image Velocimetry (PIV). The purpose of the experiments is to understand the jet induced forces on STOVL aircraft while hovering close to the ground. For this purpose, a large diameter circular plate was attached at the nozzle exit. The oscillations of the impinging jet generated due to a feedback loop are captured in the PIV images. The instantaneous velocity field measurements are used to describe flow …characteristics of the impinging jet. The important flow features such as oscillating shock waves, slipstream shear layers and large scale structures are captured clearly by the PIV. The presence of large scale structures in the impinging jet induced high entrainment velocity in the near hydrodynamic field, which resulted in lift plate suction pressures. A passive control device is used to interfere with the acoustic waves travelling in the ambient medium to suppress the feedback loop. As a consequence, the large scale vortical structures disappeared completely leading to a corresponding reduction in the entrainment. Show more

Keywords: supersonic impinging jets, PIV, large scale structures, convection velocity, feedback control

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 213-221, 2000

Authors: Kimura, I. | Hattori, A. | Ueda, M.

Article Type: Research Article

Abstract: This paper presents a new particle pairing algorithm using "Genetic Algorithms" for DPIV (Digital Particle Image Velocimetry), which are searching algorithms for obtaining an optimal solution based on the mechanism of evolution. The particle pairing between two tracer images with a constant time interval is needed to obtain a velocity vector field. Since the algorithm adopts a fitness function which totally evaluates the similarity between respective small particle patterns in the two tracer images over the …field, it promises to give a more correct velocity vector distribution than the conventional PTV (Particle Tracking Velocimetry) which identifies each particle based on its local information. In addition, a particle pattern matching for the similarity is performed after correcting fluid rotation. It therefore is robust against a high particle density and an increase in the time interval. The algorithm is applied to the PIV standard images distributed through the Internet (http://www.vsj.or.jp/piv). It gives a correct velocity vector distribution as a result even if a pair of the successive images has a large time interval. Show more

Keywords: PIV, PTV, particle pairing, genetic algorithms

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 223-228, 2000

Authors: Kompenhans, J. | Raffel, M. | Dieterle, L. | Dewhirst, T. | Vollmers, H. | Ehrenfried, K. | Willert, C. | Pengel, K. | Kähler, C. | Schröder, A. | Ronneberger, O.

Article Type: Research Article

Abstract: Particle image velocimetry (PIV) is increasingly used for aerodynamic research and development. The PIV technique allows the recording of a complete flow velocity field in a plane of the flow within a few microseconds. Thus, it provides information about unsteady flow fields, which is difficult to obtain with other experimental techniques. The short acquisition time and fast availability of data reduce the operational time, and hence cost, in large scale test facilities. Technical progress made in …the last years allowed DLR to develop a reliable, modular PIV system for use in industrial wind tunnels. The features of this system are summarized and results of recent PIV applications are presented. Show more

Keywords: particle image velocimetry, PIV, industrial wind tunnels, aerodynamics, unsteady flow fields

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 229-244, 2000

Authors: Trinité, M. | Lecordier, B. | Lecerf, A.

Article Type: Research Article

Abstract: An understanding of flame propagation needs the knowledge of the flame location and of the velocity field near the front. Time resolved laser Tomography coupled with high resolution cross correlation PIV has been developed. The method is based on the use of a copper vapor laser and a high-speed camera. The seeding level used for tomography provides an excellent resolution of the flame location and of the velocity vectors in the fresh gases. Experiment is conducted …in a simulated engine where turbulence is controlled by means of a perforated grid. Interest is shown for the determination of laminar burning velocity and for the study of interaction between the flame front and the turbulent structures. Perspectives of stereoscopic PIV are also started on. It is shown that the existence of a normal component to the sheet plane of the velocity can lead to an erroneous flame velocity determination. Show more

Keywords: tomography, PIV, time resolved, stereoscopy, flame propagation

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 245-256, 2000

Authors: Roquemore, W.M. | Katta, V.R.

Article Type: Research Article

Abstract: This paper describes how visualizations have been used in the development and evaluation of a reacting-flow-simulation model known as UNICORN (UNsteady Ignition and COmbustion with ReactioNs). UNICORN, which solves full Navier-Stokes equations, has evolved over a 6-year period and is perhaps one of the most thoroughly evaluated codes of its kind. It evolved hand-in-hand with experiments that have been conducted to test its ability to predict ignition, extinction, and the dynamic characteristics of diffusion and premixed …flames of hydrogen, methane, and propane fuels and that are stabilized in different ways. This paper also describes how UNICORN has been used, in conjunction with experiments, to provide new insights into combusting flows. Also, predictions of unobserved phenomena that were later confirmed by experiments are described. This paper demonstrates that the judicious use of a well-validated simulation in conjunction with laser based diagnostics is an effective way of understanding complex combusting flows. Show more

Keywords: vortices, visualization, flames, combustion, laser diagnostics, turbulence

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 257-272, 2000

Authors: Tropea, C. | Damaschke, N.

Article Type: Research Article

Abstract: This article reviews a number of recent PDA developments designed to either improve accuracy or extend the technique in measurement range or measurand. Many of these developments have depended on improvements in the computation of light scattering from small particles and initially several of these improvements will be discussed. The sensitivity of the dual-mode PDA to particle sphericity will be discussed, followed by possibilities for the sizing of oscillating particles/droplets. Finally, some remarks will be directed …to the dual-burst technique and its use in novel optical systems. Show more

Keywords: phase Doppler anemometry, light scattering, particle sizing

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 273-279, 2000

Authors: Dopheide, D. | Többen, H. | Strunck, V. | Grosche, G. | Müller, H.

Article Type: Research Article

Abstract: Advanced novel techniques for sophisticated LDA applications are presented in this paper. By applying laser sources with high output powers like MOPA-lasers (master oscillator power amplifier), fiber lasers and booster fiber amplifiers to increase the laser power in the measuring volume and by amplifying the scattered light power with optical fiber preamplifiers to increase the sensitivity of the receiving units, the signal-to-noise-ratio of laser Doppler signals is drastically improved and the overall performance of a …laser Doppler anemometer is significantly enhanced. Show more

Keywords: novel LDA-techniques, semiconductor laser LDA, optical amplifiers, fibre amplifier LDA, fibre laser LDA

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 281-292, 2000

Authors: Hargrave, G.K. | Wigley, G. | Allen, J. | Bacon, A.

Article Type: Research Article

Abstract: The research described here addresses the problem of a paucity of high quality data on the full field structure of high pressure liquid fuel sprays for gasoline direct injection, GDI, engines. The paper describes the application of phase Doppler anemometry, PDA, and single-shot laser sheet Mie imaging to the study of GDI sprays and discusses the methodologies adopted for the experimental systems and the optimisation of the techniques. Experimental data is presented which defines the spray …structure in terms of PDA vector and scalar fields and single-shot CCD digital images. The work demonstrates the essential complementary nature of the single point and planar optical diagnostics for spray studies. Show more

Keywords: spray, GDI, PDA, laser sheet, visualisation

Citation: Journal of Visualization, vol. 2, no. 3-4, pp. 293-300, 2000