Begell House Inc.
Journal of Flow Visualization and Image Processing
JFV
1065-3090
4
3
1997
IMAGING SUPERSONIC AIRCRAFT SHOCK WAVES
189-199
10.1615/JFlowVisImageProc.v4.i3.10
Leonard M.
Weinstein
Measurement Science and Technology Branch, NASA Langley Research Center, Hampton, Virginia
Kathryn
Stacy
Scientific Applications Branch, NASA Langley Research Center, Hampton, Virginia
Gerald J.
Vieira
Sounding Rockets and Range Management Branch, NASA Wallops Flight Facility, Wallops Island, Virginia
Edward A.
Haering, Jr.
Aerodynamics Branch, NASA Dryden Flight Research Center, Edwards Air Force Base, California
Albion H.
Bowers
Aerodynamics Branch, NASA Dryden Flight Research Center, Edwards Air Force Base, California
A schlieren imaging system that uses the sun as a light source was developed to obtain direct flow-field images of shock waves of aircraft in flight This system was used to study how shock waves evolve to form sonic booms. The image quality obtained was limited by several optical and mechanical factors. Converting the photographs to digital images and applying digital image-processing techniques greatly improved the final quality of the images and more clearly showed the shock structures.
PHASE-CONTROLLED MIE-SCATTERING VISUALIZATION FOR STUDYING PERIODIC FUEL INJECTION INTO OSCILLATING FLOWFIELD
201-210
10.1615/JFlowVisImageProc.v4.i3.20
Ken H.
Yu
Research and Technology Division, Naval Air Warfare Center Code 4B3200D, China Lake, CA 93555
Klaus C.
Schadow
Research and Technology Division, Naval Air Warfare Center, China Lake, CA 93555
A simple, inexpensive flow visualization technique for studying moderate-frequency oscillating flow field is described. The technique involves performing planar Mie-scattering visualization in a phase-sensitive fashion using a conventional CCD camera equipped with a built-in electronic shutter. The periodic nature of the flow field is utilized making it possible to study a rapidly oscillating flow field without the use of high-speed film. It allows the use of video camera in studying the oscillatory phenomena with the period much shorter than the video display period. In this article the technique was used to study periodic fuel injection into a forced flow field. Real-time phase-resolved acquisition and computerized processing of planar Mie-scattering images were performed with a simple setup and at a reasonable cost. While a copper-vapor laser was used as the light source in the work, the technique can also be employed with other less-expensive light sources, including continuous as well as spark-based types.
MANIPULATION OF THE STARTING SEMICIRCULAR-CYLINDER NEAR-WAKE BY MEANS OF A SPLITTER PLATE
211-221
10.1615/JFlowVisImageProc.v4.i3.30
Nathalie
Boisaubert
LE.A./LM.F. (U.M.R. CNRS n°6609), Bâtiment de Mécanique-40, avenue du Recteur Pineau-86022 Poitiers Cedex, Université de Poitiers - France
Madeleine
Coutanceau
LE.A./LM.F. (U.M.R. CNRS n°6609), Bâtiment de Mécanique-40, avenue du Recteur Pineau-86022 Poitiers Cedex, Université de Poitiers - France
Alain
Texier
LE.A./LM.F. (U.M.R. CNRS n°6609), Bâtiment de Mécanique-40, avenue du Recteur Pineau-86022 Poitiers Cedex, Université de Poitiers - France
As an example of flow controller, a short ID-long splitter plate is selected to manipulate the wake of an impulsively started flat-back semicircular cylinder (of diameter D) exhibiting fixed separation points. The way the plate-interaction develops with time and modifies the early vortex formation and shedding is analyzed with details by means of two complementary techniques of visualization (dispersed solid particles and dye filaments) when, positioned along the downstream center plane, the body-to-plate gap ranges from 0 to 1D and the Reynolds number is 600. Both topological observations like the possible occurrence and development of more or less important secondary separations and vortices, the shifting of the vortex shedding to the trailing edge of the plate and quantitative measurements characterizing the recirculating zone geometry and velocity magnitude are proposed and compared with the previous data by Boisaubert et al. [1] related to the plain body wake.
FLOW VISUALIZATION OF A BALLISTIC RANGE BY COLOR SCHLIEREN METHODS
223-230
10.1615/JFlowVisImageProc.v4.i3.40
M.
Kameda
Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, Japan
Hiroyuki
Abe
Computational Science Research Group, Japan Aerospace Exploration Agency
H.
Chinju
Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, Japan
M.
Konno
Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, Japan
Yoshimi
Watanabe
Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan
F.
Higashino
Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, Japan
A vertical ballistic range is constructed to investigate sonic boom properties. The flow field around a launched projectile in the range is visualized by both one- and two-dimensional color schlieren methods. The flight Mach number of the projectile is lower than 1.5. The flow visualization shows that some disturbances, such as blast waves, vortex rings, and jets, are generated when the projectile is launched. The blast waves have strong influences on the flow field around the projectile because the propagation velocity of the blast waves is close to the velocity of the projectile. Setting a few baffle plates at the exit of the barrel effectively reduces the strength of the disturbances. The present color schlieren method extended to two-dimensional analysis is an effective one to visualize a complicated supersonic flow field like the present experiment.
MEASUREMENT OF CONDENSATION HEAT TRANSFER COEFFICIENTS AT STRATIFIED FLOW USING LINEAR RAMAN SPECTROSCOPY
231-244
10.1615/JFlowVisImageProc.v4.i3.50
J.
Karl
Lehrstuhl für Thermische Kraftanlagen, Technische Universität München, Boltzmannstrasse 15, D-85747 Garching, Germany
T.
Weiss
Lehrstuhl für Thermische Kraftanlagen, Technische Universität München, Boltzmannstrasse 15, D-85747 Garching, Germany
To determine heat transfer coefficients during condensation at stratified flows in absence or presence of noncondensable gases, it is essential to either know the temperature profile in the water layer or the concentration profile in the vaporous phase with a satisfactory local resolution. The presented method to achieve those profiles is the linear Raman spectroscopy. The obtained spectra of the condensation boundary layer were processed by an algorithm that evaluates the concentration profiles in the vaporous phase and the water temperature of the liquid phase with a local resolution of 0.06 mm. The water temperatures were measured with an accuracy of ±2 K. The errors of the determined heat transfer coefficients are estimated to be less than 10%.
MIXING INSIDE A CAVITY AT INTERSECTION OF TWO CROSSING FLOW PASSAGES
245-259
10.1615/JFlowVisImageProc.v4.i3.60
An experimental study is conducted on mixing phenomena inside a circular cavity at the intersection of two crossing ducts, creating converging and diverging flow into and out of the cavity after mixing. The intersecting angle and the relative flow rates in the pair are varied to investigate their effects on the secondary flow and mixing phenomena in the cavity. Flow pattern is visualized by means of the particle tracing method and velocity distribution is obtained by laser Doppler velocimetry (LDV). The exiting flow rate and total pressure loss across the cavity are determined by hydrometry. Colorimetry, which has been used with color video images to analyze the visual field of complex scenes, such as landscapes and building interiors, is employed to investigate the mixing phenomena. It is shown that a critical Reynolds number exists beyond which the mixing performance and total pressure loss across a cavity becomes independent of the intersecting angle and relative converging flow rate.
THERMO-FLUID-DYNAMIC APPLICATIONS OF QUANTITATIVE INFRARED THERMOGRAPHY
261-280
10.1615/JFlowVisImageProc.v4.i3.70
Infrared thermography can be regarded as a powerful technique from both qualitative and quantitative points of view to be employed in a vast variety of industrial applications as well as research fields. However, for accurate quantitative measurements, particular attention is required to overcome all the potential error sources that can entail degradation of the thermal image. In this work, the emphasis is on convective heat transfer measurements; the degradation introduced by the heat flux sensor and by the IR imaging system is analyzed and restoration of the thermal image is discussed. Some fluid flow configurations studied by means of the IR imaging system are also presented.
A MEASUREMENT OF MOVING SHOCK WAVE POSITIONS BY A LINEAR IMAGE SENSOR AND SCHLIEREN SYSTEM
281-294
10.1615/JFlowVisImageProc.v4.i3.80
Toshimasa
Shiratori
Department of Aerospace Engineering, Tokyo Metropolitan Institute of Technology, Hino, Tokyo, Japan
Masahiro
Matsushita
Systems Engineering, Graduate School, Tokyo Metropolitan Institute of Technology, Hino, Tokyo, Japan
A simple and efficient system to measure positions of the shock wave fluctuating with high frequency is evaluated. This system consists of a Schlieren optical system and a line scan camera using a linear image sensor, and a data acquisition and processing computer. The shock position was determined by shock position-recognition processing. The unsteady shock waves occurring in the flow passage of a two-dimensional cascade were measured using this system. The results show that this system can effectively measure the unsteady shock position moving at several hundreds Hz for a single shock wave. However, more creative techniques are required for the measurement and the recognition of multiple shock waves.
LARGE BODY AIRCRAFT CABIN A/C FLOW MEASUREMENT BY HELIUM BUBBLE TRACKING
295-306
10.1615/JFlowVisImageProc.v4.i3.90
R. H. G.
Muller
F.I.B.U.S. Research Institute, Paul-Klee-Weg 8, D-40489 Dusseldorf, Germany
Th.
Scherer
Daimler-Benz Aerospace Airbus GmbH, Postfach 950190, D-21111 Hamburg, Germany
Th.
Rotger
Daimler-Benz Aerospace Airbus GmbH, Postfach 950190, D-21111 Hamburg, Germany
O.
Schaumann
Daimler-Benz Aerospace Airbus GmbH, Postfach 950190, D-21111 Hamburg, Germany
M.
Markwart
Daimler-Benz Aerospace Airbus GmbH, Postfach 950190, D-21111 Hamburg, Germany
Air conditioning in large body aircraft is a very important and delicate task. Due to the complex cabin geometry, it is difficult to obtain an equally distributed low-speed airflow with high air exchange rates. Experimental data of the A/C flow have to be provided for development or verification of computational fluid dynamics codes (CFD) that can be used for optimization. The technique described in this publication uses soap bubbles filled with helium for visualization and particle tracking software for image analysis. Time averaging of long image sequences is used to produce air velocity vector plots and vorticity contour plots. The complex A/C flow shows rotational flow areas and proves that air velocities are well in the range of the aircraft specifications. Qualitative comparison between experiment and CFD calculation is reasonable and encourages the use of CFD for cabin design to optimize the A/C flow.
VISUALIZATION OF OSCILLATORY FLOW IN TAPERED TUBE
307-315
10.1615/JFlowVisImageProc.v4.i3.100
Takehiro
Himeno
Department of Aeronautics and Astronautics, University of Tokyo
Toshinori
Watanabe
Department of Aeronautics and Astronautics, University of Tokyo, Tokyo 113-8656, Japan
Seiichi
Shinada
Department of Aeronautics and Astronautics, University of Tokyo, Tokyo, Japan
To clarify the flow mechanism that could enhance the gas exchange in lung system, the oscillatory flow fields in some types of tapered tubes were visualized by a laser light sheet method. The light sheet was made with a polygon-mirror scanning system of a laser beam. In the tapered section, it was observed that the vortex sheet of a Kelvin-Helmholtz type was generated at the outer edge of the tube-wall boundary layer, or that the flow separated at the diverging region and the resultant shear layer rolled up into vortices. The observed flow patterns could be classified based on the Reynolds number defined by the Stokes layer thickness and the mean velocity amplitude. The flow features were discussed from the viewpoint of flow instability related to the adverse pressure gradient in the tube flow field.