This paper describes extensive numerical studies on the gases diffusion flame gas-turbine combustor using a interactive steering supercomputing simulation system. The system which are CRAY Y-MP and IRIS4D connected by Ultra-net can vizualize analysis process and alter the numerical condition. The complicated 3D flow cased by air jet and the temperature increase result of combustion reaction was obtained. It was found that the interactive simulation system was valid for the complicated combustion analysis. These were enabled by real time data transfer, that monitoring of calculating status and steering a parameter of analysis interactively.
The present visualization shows the limiting streamline vector, the velocity vector, the isotherm, the local Nusselt number, and the wall shear stress for the 3D thermalflow from a heated, vertical square plate by solving numerically the 3D Navier-Stokes equations and the 3D energy equation using the vector potential.
The formation, development and collapse process of three-dimensional vortex over a cone-cylinder at high angles of attack and the resulted separated flow pattern are visualized by a laser-light-sheet method. A new idea for shear layer splitting and the formation of three dimensional vortex is presented. It is shown that the shear layer over a slender body at high angles of attack does not roll up directly into one large vortex but splits into several parts while each part forms a small vortex. Thus generated vortices then merge together to form the large scale vortex. The asymmetry in shear layer splitting and vortex merge on the two sides of a body dominates the asymmetry of the large scale vortex.
This paper deals with an experimental investigation on buoyancy-driven exchange flows through horizontal and inclined openings. The method of the mass increment was developed to measure the flow rate in helium-air system and a displacement fringe technique was adopted in Mach-Zehnder interferometer to visualize the flow. As the result, the followings were obtained : Flow visualization results indicate that the upward and downward plumes of helium and air break through the opening intermittently, and they swing in the lateral direction through the horizontal opening. It is clearly visualized that the exchange flows through the inclined openings take place smoothly and stably in the separated passages. The inclination angle for the maximum Froude number decreases with increasing length-to-diameter ratio in the helium-air system, on the contrary to Mercer's experimental results in the water-brine system indicating that the angle remains almost constant.
Air ingress after pipe rupture accidents causes corrosion of the graphite structures in a pressure vessel in a High Temperature Gas-Cooled Reactor (HTGR). Injection of inert gas might be very effective to prevent this phenomenon. We have carried out the transient numerical analysis on the code based on the SIMPLEST algorithm to study the flow behavior and mass transfer. Experimentally we have visualized the mass fraction of inert gas by using the Mach-Zehnder interferometer and compared the results with those from numerical calculations. As the results, the head of the jet is pushed out to radial direction by impinging against the stagnant air at the first stage of the discharging. The flow patern reaches a steady state after 0.5s of gas injection.
Surface deformation by impact of a droplet and entrainment of the droplet into water arc visualized by means of a high-speed video camera developed by the authors, of which framerate is 4, 500 pps. The average diameter of droplets used in the experiment is 4.6 mm. The height of the nozzle which releases droplets is varied in the range of 5-45 cm. Some preliminary results are obtained as follows : (1) The relation between height (i.e., impact speed) and size of the crater changes for the low or high falling velocity, which implies the process is also different, (2) The surface deformation and entrainment processes can be clearly visualized in detail by the camera.
Aerator for air entrainment has been adopted in spillway structures to prevent possible cavitation errosion on the surface of concrete. So far, many model studies and field measurement have been carried out. This paper describes a measurement of air bubble entrained through aerator in tunnel spillway model. Air bubble sizes were read from visualized air-water flow pictures, the result of which was consistent with ones measured by electric probe method. As a result, it became clear that, by a few visualized pictures, air bubble size distribution after aerator could be estimated.
In this study, the effect of the variations in the logarithmic spiral angle of the curved diffuser profile and the interposed position of a guide vane in the curved diffuser on the flow patterns are clarified by the flow visualization using dye-streak method, and their results are compared with the numerical solutions obtained by the finite element method. As a results of this study, it was found that the flow patterns in a curved diffuser are affected considerably by the logarithmic spiral angle and the interposed position of the guide vane, and the desirable profile of the curved diffuser can be estimated relatively easily.
The inner flow situated just behind the regular pyramidal diffuser inlet is a complicated turbulence with a shear voitex produced by separated flow at the diffuser inlet wall and voltex produced by secondary flow at the four corners of the diffuser. This turbulent flow could be visualized by the tuft grid method. The averaged fluctuation pattern in cross section across inlet flow of reguler pyramidal diffuser, in which unsteadily flow, is visualized by the improved tuft grid method, and recorded by using the photographic film and video imaging. On the other hand, the amplitude of the fluctuation was measured by used hot-film probe. The diffusers are presented for following condition : length ratio N/W = 10 and total divergence angles 2Θ = 2°, 4°, 6° and 8°.
It is important to disclose flow characteristics of various flow networks in engineering apparatus and human body. In this paper, experiments for flow inside two intersecting pipes are performed using various technics of flow visualization. As a result, it is disclosed that coefficients of pressure drop, head loss and velocity in intersecting pipes change with Re number for different intersecting angles.
Recent advancement of technology.need the compactness of heat exchanger to be used in the air conditioner without lowering it's overall performance. It is well known that the performance of heat exchanger can be improved by introducing slits on the fin. However, the important problem here, is to choose the best possible slit pattern. In order to study the above mentioned problem, in the present work, experiment is carried out by using 10 times enlarged model fins of heat exchanger for flow visualization. Results indicate fully developed laminar flow pattern in the case of flat parallel plate. In the case of alternative arrangement of the slits, it is observed that the flow is symmetrical downstream the second stage of alternative slit pattern. Comparison of the experimental flow pattern with the calculated heat transfer coefficient lead to the understanding that downstream the second stage, if slits are arranged in such a way that the flow interact with the slits in the portion where the flow velocity is high, it is possible to increase the heat transfer coefficient.
Systematic measurements on the heat transfer and pressure loss performance of pin-fin arrays were conducted using a wind tunnel, by varying the pin pitch as a parameter. The pin-fin arrays used in the present study were made of square shaped thin pins arranged densely in a rectangular form. The modified single blow transient testing method was applied to the measurement. Additionally, the flow visualization tests were carried out utilizing fifteen times enlarged pin-array models with dye injection technique. Water was used as the test fluid. The test results showed a good correspondence between the heat transfer and pressure loss phenomena and the flow pattern characteristics.
The lift and drag characteristics of specially designed complex airfoil are investigated by surface pressure and wake velocity measurements in a smoke tunnel. To understand the characteristics obtained, flow mechanism induced by this complex airfoil was investigated in the same tunnel by flow visualization technique using the smoke-line, tuft and oil flow methods. Both airfoil characteristic study and flow visualization were carried out under the same following conditions; Reynolds Number Re=3.3 × 105, angle of attack α=-615 degrees.
This study aims to be clear the behavior of surface buoyant jet discharged on the sloping bottom which is very important for the engineering aspects. Experimental studies are conducted using veritically two-dimensional flume at various conditions. The classifications of density interface are done and find strong effects by bottom slope : S and densimetric Froude number at outlet : F do. Also, densimetric Froude number of the ultimate flow condition : F 1f is found F 1f0.8 regardless of S and F do.
This paper presents experimental study on the behavior of buoyant surface jet discharged on the sloping bottom. The important resuts of this study are concluded as follows. (A) Smaller bottom slope prompts jet type spreading rather than buoyant speading. (B) Smaller bottom slope prompts meandering of jet axis and cause large scale coherent motion. (C) bottom slope does not affect the temperature distributions even though the effects of bottom slope are very strong against spreadings.
There are many papers concerned with flow visualization around a circular cylinder, but most of them reported the flow that flow boundary did not affect the flow pattern around a circular cylinder. Now since offshore structures have been or will be built, it is necessary to investigate the flow field around a horizontal circular cylinder suffered from bed boundary effects. In this paper, changing the clearance.e, between cylinder and bed. We report the results of flow visualization around a horizontal circular cylinder placed at flat and curved bed.
This paper is concerned with the 3D trajectory of particle released from the crest of modeled river bed configuration. The trajectory of particle was visualized by using of two CCD video cameras. One of them is placed on the flume and the other is placed at the flume side. After the correction for particle coordinate, the particle trajectory was shown by means of wire frame method, and moreover the 3D trajectory was indicated realistically by means of ray tracing method. The results of this paper are as follows : A ccording to increasing discharge, trajectory of particle showed a complex motion such as abruptly upward or swirly motion.
In order to investigate the flow around a shaft bracket at stern, the horseshoe vortex around the jounction between flat plate and airfoil is observed by using the so-called milk painting method. Only one separation line is appeared in front of the airfoil, although the several lines have been observed in the case of circular cylinder. The flow inside the separated region is visualized by milk injection from the small hole on the flat plate.
A fundamental visualization of flow inside of a non-bleeding air cooling turbine vane model has been conducted. Owing to its relatively complicated 3D structure, the flow includes turbulence and wide-range velocity distribution, so that it is relatively difficult to visualize the flow under these condition. In the present paper, a few kinds of flow visualization method using water current were applied; those were dye color streak method and polystyrene tracer method. In the tracer method, particle images were taken under the condition of continuous light and multi-exposure plural flashing-light, respectively. Characteristics of the flow pattern due to the different impingement hole arrangements has been indicated.
Experiments have been carried out to elucidate the gas exchange in pulsating flow through the inlet of a duct, that simulates the nose. The pulsating flow in a two-dimensional duct was visualized by the smoke wire method and the cigarette-smoke injection method. The results show that the time-dependent velocity inside of the duct could be measured with reasonable accuracy and a steady streaming are found to be existing near the open end of the duct.
The paper to be presented is related to one of the methods of fuel supply to the gasoline engine that is, the method of direct fuel injection into the engine cylinder. This method utilizes as the injector the poppet nozzle which is shaped in the manner of two parallel conical surfaces. This flow visualization study deals with basic flow phenomena occurring in the annular- conical passage, similar to that one creating the poppet nozzle and helps to understand them. The paraffin mist was used as a tracer. An Argon laser and a 500 W flood - light were used for the illumination.
The flow field in a sharp bend tube was visualized using laser light sheet method and the velocity field was also measured by laser Doppler velocimeter. A 90° bend tube whose radius of curvature is four times its tube radius is connected with 70 diameters long straight tube in order to establish a fully developed laminar pipe flow at the inlet of the bend. The flow field in the plane of symmetry is visualized to show flow reversals at the outer side of the bend near its inlet for Re > 613 and at the inner side of the bend around the bend angle Ω = 58° for Re > 1320. The distributions of streamwise and transverse velocities at several bend angles were obtained. The contours of streamwise velocities are found to shift towards the outer side of the bend and form C-shaped distributions. The secondary flow is found to form a pair of vortex and is strongest at the bend angle Ω = 30°.
In the present study, the results of an attempt to estimate the flow field, pressure, and wall shear stress distribution patterns at arterial bifurcations of various configurations are shown with videotape and discussed with respect to pathogenesis of vascular disorders. The three dimensional Navier-Stokes equations for incompressible Newtonian fluid flow were solved by a finite volume method with the generalized curvilinear coordinate system, or the body-fitted coordinate (BFC) system. Models were two dimensional and had various branching angle and mother-daughter diameter ratio. The boundary conditions specified are : steady and pulsatile fully developed flow at the inflow cross-section, a non slip condition at the rigid wall and zero pressure with zero velocity gradient at the outlet cross-section. Obtained results were displayed using color computer graphics and animation technique. Complex vortices were always found at the bifurcation regardless the branching angle. It is necessary to take them into account when discussing the development of atherosclerosis, since the progression of the disease may be significantly altered by these flow patterns.
Atherosclerosis and atherosclerotic aneurysms can occur in the abdominal aorta. Steady and pulsatile three-dimensional flow cases were simulated in an abdominal aortic aneurysm on a graphics workstation. In the steady flow case, in the aneurysm center, two symmetric vortices were formed, and flow separation started at the aneurysm inlet. Regions of high pressure were observed at the aneurysm exit caused by the symmetric jets that were formed, implying that this high-pressure region could be an area where rupture is most likely. The shear stress was low in the aneurysm portion of the vessel, and local maximum values were observed at the distal aneurysm constriction. In the unsteady flow case, the main vortex appeared and disappeared and changed position in the unsteady flow case and induced vortices were formed; in the steady flow case only one constant vortex was observed in the centerline view. The graphics system allows instant observation of the vascular structures from any angle or distance while moving, with wire frame and solid viewing modes being possible. The graphics programs allow the viewer to travel inside the aneurysm to observe the pressure and shear distribution in colorful detail, and videos have been made.
Numerical investigations were carried out for natural convection in a two-dimensional square enclosure. The boundary walls were included in the calculation, in which heat conduction in the walls and heat transfer between the walls and the ambient were considered.The simulation results with and without the boundary walls were compared. The distributions of velocity vectors and stream functions had no distinct difference between two cases, while the isotherms were different near the upper and lower walls. In the simulation with the walls, heat transfer between inside fluid and the upper or lower walls was found to play an important role in natural convection in the square enclosure, while heat transfer between the walls and the ambient had only a little influence. Numerical results were also compared with the experiments. Calculated isotherms and stream lines agree well with those of the experiments.
This paper presents a comparison of the experimental flow visualization and the numerical simulation of Mach 3 supersonic air-intake. Two models are investigated. The results of 2-D and 3-D Navier-Stokes analysis are compared with schlieren photographs and oil flow visualization, respec-tively. The shock behaviors near throat regions and basic flow structures on the side wall including the boundary layer separation and reattachement induced by 3-D shock boundary layer interactions are well simulated.
As a simple model of the large-scale structure in the laminar boundary layer, the development of multi-disturbances is calculated using a three-dimensional discrete vortex filament method. Two equivalent initial disturbances are applied to the same filament and are stretched by the streamwise velocity. The top regions of the disturbance are deformed by the induced velocity. The hairpin-shaped structure deforms and pinches out. A unique vortex loop is created and the sweep structure appears in the vicinity of the wall which does not appear in the case of deformation of a unique disturbance.
Recently, the biological effects of electric and magnetic fields have been investigated by many researchers. In this paper, we present the visualization of magnetic field distribution under the Ultra High Voltage (UHV) power transmission lines to investigate the effects of magnetic fields on human bodies. The method for solving problems of the magnetic fields is based on the electric image method which is the best way of analyzing electric and magnetic fields around the transmission lines. The distribution of magnetic field intensities is visualized by personal computer graphics with 10 color grades. From the above, it is considered that the effects of magnetic fields on human bodies at the surface of the earth when exposed to UHV power transmission lines can be neglected.