Journal of Visualization

The internal flows of solid rocket motors are not yet fully understood. Several cold-air flow experiments that simulated combustion gas flow with compressed gas wall injections have been conducted to observe the behavior of internal flows and acoustic phenomena. Direct visualization, however, has rarely been performed due to the non-transparency of the wall-injecting media. In this study, novel techniques were employed to visualize the internal flow of the cold-flow model of a solid rocket motor. The smoke, which was generated using a heated Ni–Cr wire, was used as a flow tracer, and a light penetrated through an acrylic nozzle. The head-end of the test model was made with a transparent acrylic window to record the visualized flow using a high-speed CCD camera. The results of the visualization at the nozzle entrance region showed the symmetric vortex tube structures and the transient behavior of the circumferential flow. The vortex tube generation mechanism was explained with reference to the inlet vortex phenomenon of an aircraft engine. Also, it was observed that the interaction between the adjacent vortex tubes created the circumferential flow.

In this research, the effect of the leading-edge extension (LEX) angle on the flow pattern upstream and downstream of the diamond wing has been investigated experimentally. The measurement of turbulence intensity by the hot-wire and the measurement of pressure on the wing by the five-hole probe in a closed-circuit wind tunnel at a free flow velocity of 12.5 m/s, which is equivalent to the Reynolds number of 202,000, have been carried out. In order to better observe the flow physics and qualitative analysis of the vortex flow, the smoke tunnel has been used. In this case, the free flow velocity is equal to 1 m/s equivalent to the Reynolds number of 16,000. The results indicated that the increase in the LEX sweep angle has led to an increase in the strength of the vortex, and with the increase in the angle of attack, the vortices have moved further away from the wing's upper surface. Also, the increase in the angle of attack shifts the breakdown location upstream, eventually reaching a complete wing stall. The use of LEX produced a vortex flow, which delayed the vortex breakdown by increasing the kinetic energy in the vortex core. The turbulence downstream of the wing is reduced with the breakdown delay. The frequency analysis showed that at the vortex core, the instantaneous velocity fluctuations are very high, which indicates an increase in turbulent kinetic energy.

This work presents a novel method of visually capturing the relative importance of different flow regions with respect to a quantity of interest. Existing flow visualization techniques are enhanced to convey flow importance. This is accomplished by filtering their output with additional information obtained from the adjoint counterpart of the physical flow field. The additional adjoint data is of equal resolution to the physical flow field. The adjoint flow data links physical fluid regions to user chosen quantities of interest. Thus, regions that are less relevant to the quantity of interest can be masked or deemphasized to reduce clutter and to highlight the behavior of the more important flow regions. The concept is demonstrated on a series of fluid simulations. The visualizations highlight the temporally changing importance of flow features, regions of influence in complex flows, and occlusion reduction in 3D flows. The method is also demonstrated by checking the impact of perturbations introduced in flow regions that were found to be both important and unimportant based on the adjoint data.

Current visualization design toolkits help users to explore data and create visualizations. However, most of these systems do not record the executed actions during the visualization construction process with semantic context. In this paper, we present VisAct, a visualization design system based on semantic actions, that helps average users to construct visualizations step by step. Our system contributes a set of action-based visualization components and a high-level grammar for semantic actions. VisAct also guides the visualization construction process and provides an action tracker for history management and data collection. We demonstrate the usability of VisAct by visualizations and a plugin application. Finally, we conduct a user study to evaluate the efficiency and effectiveness of our system.

Immersive analytics often takes place in virtual environments which promise the users immersion. To fulfill this promise, sensory feedback, such as haptics, is an important component, which is however not well supported yet. Existing haptic devices are often expensive, stationary, or occupy the user’s hand, preventing them from grasping objects or using a controller. We propose PropellerHand, an ungrounded hand-mounted haptic device with two rotatable propellers, that allows exerting forces on the hand without obstructing hand use. PropellerHand is able to simulate feedback such as weight and torque by generating thrust up to 11 N in 2-DOF and a torque of 1.87 Nm in 2-DOF. Its design builds on our experience from quantitative and qualitative experiments with different form factors and parts. We evaluated our prototype through a qualitative user study in various VR scenarios that required participants to manipulate virtual objects in different ways, while changing between torques and directional forces. Results show that PropellerHand improves users’ immersion in virtual reality. Additionally, we conducted a second user study in the field of immersive visualization to investigate the potential benefits of PropellerHand there.

The three-dimensional structure of the reattached flow caused by synthetic jet actuation on an airfoil was investigated using surface flow visualization. Without active control, the flow was stalled with laminar boundary layer separation occurring near the leading edge. Tuft and oil visualization showed the shape and spanwise extent of the attached flow due to a finite span synthetic jet where the effect of excitation frequency and blowing ratio was the focus. For all excitation frequencies tested, a similar contraction of the spanwise extent of the attached flow towards the trailing edge was observed due to edge effects of the finite span jet. Increasing the blowing ratio was found to decrease the amount by which the attached flow contracted.

In the present study, three types of experiments on immiscible CO2 flooding in porous media were conducted and high-resolution images of asphaltene precipitation obtained using X-ray micro-CT scanner. It was found that the effective oil mobility is reduced due to the adsorption of deposited asphaltene onto the rock which blocks the pore throats, whereby the formation wettability is changed and both the effective porosity and permeability are reduced. The deposited asphaltene cannot be redissolved or displaced by the reinjected crude oil, and the formation damage is irreversible. In addition, the porosity-based permeability model was applied to study the effective permeability reduction that results from porosity reduction. The porosity-based permeability was calculated based on the Kozeny–Carman equation and experimental data. The effective permeability variation rate obtained by the porosity-based permeability model agreed well with the results obtained by Darcy’s law, which demonstrates that the method is feasible in evaluating the effective permeability variation rate based on the porosity of the cores acquired from micro-CT images.

The complex separated flows induced by shock wave/boundary layer interaction were studied at hypersonic speed of Mach number 5. The experimental results on hypersonic flow over a set of rectangular cylinders are presented in this paper. The rectangular cylinder mounted on a flat plate worked as a typical model to simulate the obstacle on the vehicle surface. The effects of flow interaction on the aerodynamic characteristics have to be predicted for various geometrical parameters. So the static pressure distributions on the model surface were measured, the complex shock wave system was shown by schlieren photos, and the separated flow patterns around the obstacle were visualized by oil flow technique. All of the results describe the interactive flowfield features including peak pressure levels and their locations as well as separated boundaries associated with influence regions.

We propose an event-based analysis system for comparison of several ensemble time-varying simulations. In this pipeline, users can customize the selection of events (i.e., the keyframes of the simulations) for each simulation on the timeline view. The associated rendered thumbnails are tiled in the rendered thumbnail view. The ticks on the timeline and the rendered thumbnails are connected by a link. Users are allowed to do 3D exploration on the render thumbnails and the high-resolution view on which the details can be displayed. Switching between different variables is supported to assist users in exploring the rendering of different ensemble variables or even combinations of variables. We apply our system into the deep water impact ensemble dataset. The system is proved to have the ability to help users better explore the simulations.

A standard 75-cl bottle of champagne holds about 5 l of dissolved carbon dioxide (CO2). When pouring champagne into a glass, a significant part of dissolved CO2 desorbs from the liquid phase (Liger-Belair in J Agric Food Chem 53:2788–2802, 2005; Liger-Belair et al. in Chem Soc Rev 37:2490–2511, 2008a). As CO2 is invisible under natural light, its progressive release in the atmosphere was made visible through an infrared (IR) camera equipped with a band-pass filter (Pron et al. in J Vis 13:181–182, 2010). By use of this novel method, the visual tracking of the progressive desorption of dissolved CO2 has been carried out, under standard serving conditions, whether champagne was served into a flute or into a coupe.