The paper presents numerical research of supersonic flow around the aerodynamic configuration with a conical stabilizer (flare). Analysis of flow fields and distributions of the gas-dynamic parameters was carried out. The calculated results and the experimental data are compared. A characteristic feature is revealed which is associated with the nonmonotonic character of pressure distribution on the flare.

The present work describes the development and application of a single lens-based schlieren microscopic system for imaging of buoyancy-induced convective fields and subsequent determination of three-dimensional temperature and/or concentration fields. The system differs from the conventionally employed schlieren method in a way that in contrast to a collimated beam of light in conventional methods, the developed optical system employs a diverging beam of light to scan the area of interest. The usage of the diverging beam of light shifts the rear focal plane of the microscopic objective lens, which also acts as the magnifying lens, by a finite distance outside its body without the need of any extra lens pair arrangement. This configuration enables the use of only a single microscopic objective lens for focusing the light beam onto a knife edge and/or a color filter placed at its rear focal plane to get the desired schlieren cut-off. The appli-cability of the proposed method has been demonstrated by imaging the buoyancy-induced convection currents around a sodium chlorate (NaClO3) crystal growing from its aqueous solution in the free-convection regime in situ. Monochrome as well as rainbow schlieren images of the convective fields have been recorded using a knife edge and a rainbow filter placed at the rear focal plane of the objective lens. A detailed quantitative analysis of the monochrome schlieren images has then been carried out to determine the path-averaged concentration profiles in the growth chamber. Subsequently, principles of tomography have been employed to determine the three-dimensional distribution of the concentration field around the growing crystal. Results have been presented in the form of monochrome and rainbow schlieren images recorded using the developed optical setup, path-averaged salt concentration distribution as deduced from the microscopic monochrome schlieren images, and local concentration distributions at various horizontal planes above the growing crystal using the principles of tomography. A comparative study of the results obtained using the proposed method has also been carried out against the results of the standard microscopic inter-ferometry tomography to establish the accuracy of the results and an overall good match is to be seen in the two approaches.

Visualization experiments are conducted to study the evolution of hairpin vortices shed from a pair of surface-mounted rectangular cylinders at a Reynolds number of approximately 300. The gap between the cylinders normalized by the width of the cylinders is fixed to the value of 0.75. Hairpin vortices are shed downstream from the combined wake of the paired cylinders due to the blocking effect of the combined wake on the flow exited from the gap. The hairpin vortices are large in scale and are lifted away from the surface toward the free stream as they move to farther downstream locations.

Results of the experimental study of the space-time structure of a separated flow behind a single transverse rib mounted in a channel in laminar and transitional flow regimes are presented. Smoke visualization and PIV measurements of instantaneous velocity vector fields have been carried out. Reynolds numbers corresponding to the onset of large-scale vortices generation in the shear layer behind the rib have been established; principal scenarios of the evolution of vortical structures have been revealed. Basic laws of flow statistics distribution have been obtained for different stages of transition to turbulence.

In this paper, simultaneous visualization technique for temperature and velocity fields of a premixed methane air flame is described. The temperature field is visualized by the flame reaction of potassium combined with inverse Abel transformation, while the velocity field of the flame is simultaneously measured by particle image velocimetry (PIV). This new experimental technique allows an insight into the structure of temperature and velocity fields of the flickering flame. It is found that the temperature and the velocity fields in the flickering flame indicate nonlinear oscillation of the flame. During the flame flickering, the temperature in the flame fronts increases to the highest temperature in the merging region, which is followed by the entrainment of the surrounding air into the flame. This fluid motion contributes to the decrease in temperature and self-sustained oscillation of the flame.

The main objective of this work was to visualize the buoyancy-induced flow in a road tunnel model that is analogous to the thermally driven smoke flow in the case of a tunnel fire. In the beginning, the tunnel model was made of Plexiglas and a large water tank was built using tempered glass. A cathode was placed within the tunnel model so that fine hydrogen bubbles were released as a result of the electrolysis of water. The hydrogen bubbles rose and eventually left the tunnel model enabling the simulation of the fire source in the case of a tunnel fire. Pictures were then taken at different timings to capture the instantaneous development of the flow. After that, a waterproof water pump was used to produce the effect of force convection on the rising bubbles in the tunnel model to simulate ventilation of tunnel fires. For comparison, several computational simulations were performed. Two of the most critical issues to focus are the backlayering effect and the downstream smoke propagation speed due to factors such as the fire size, the ventilation speed, and the tunnel gradient. Numerical simulations were performed through the control volume approach using FDS. The turbulence model employed for computation was the Large Eddy Simulation (LES) based on Smogorinsky model.

The drop-size distribution is a very important characteristic of liquid sprays. From a mathematical point of view these distributions are defined for spherical drops. Furthermore, the experimental diagnostics widely used to measure spray drop-size distribution characterize the droplets by a single length-scale equivalent to a diameter. However, more recent techniques based on spray image processing clearly show that a high proportion of liquid droplets are barely spherical, especially those issued from primary atomization processes. In the present paper, a new description of 2D liquid spray images is presented: the surface-based scale distribution. This distribution and its series of mean scales are functions of the shape of the particles. In the first part of the paper, this description is applied for theoretical sets of objects with controlled shape and size. Characteristic features of the surface-based scale distribution and of the corresponding mean scale series are emphasized from these applications. These features are of practical interest for the determination of the scale distribution characteristics of real 2D liquid spray images presented in the second part of the paper. Among other results, it is found that the ratios of the mean-scales to the traditional mean-diameters, which quantify the deformation of the objects, appear to be mainly a characteristic of the atomization mechanism. Finally, although it has not been explored here, an interesting aspect of this scale distribution is that it can be applied on atomizing liquid flows, opening new fields of investigation.

A numerical study is performed to investigate two-dimensional, incompressible thermal-fluid flow in a confined channel in the presence of dual laminar jet impingement. The governing equations are discretized by means of a finite-difference technique and numerically solved to determine the velocity vector and fluid temperature distributions under the appropriate boundary conditions. The Reynolds number (Re), the velocity ratio (N) at the nozzle tip, the angle (θ) of an inclined upper wall surface, and the dimensionless nozzle height (H) from the heated wall are varied to determine their effects on both the formation of jet flows and the heat transfer along the flat plate impinged by the dual jet. It is found from the study that: (i) the isotherms and the velocity distribution, particularly in the stagnation zone, are substantially affected by the velocity ratio, (ii) heat-transfer performance along the heated plate is intensified by increasing the Reynolds number and by decreasing the nozzle height, and (iii) the effect of θ becomes larger in the downstream region.

This paper summarizes results obtained by the authors from the experimental studies on flow characteristics and energy transport in both single and multiple intersecting flow networks with various geometries. The intersecting pressure loss coefficient, which represents the performance of flow networks, is determined as a function of geometric and flow conditions. A method is developed to measure the ramming loss in an intersecting tube. Flow visualization by various techniques is applied to observe flow patterns, flow separation, and mixing behavior in the flow networks.