This article reports the active control of base FLOWs using the experimental procedure. Active control of base pressure helps in reducing the base drag in aerodynamic devices having suddenly expanded FLOWs. Active control in the form of microjets having 0. 5 mm radius placed at forty-five degrees apart is employed to control the base pressure. The Mach numbers of the present analysis are 1. 7, 2. 3, and 2. 7. The length to diameter (L/D) ratio is varied from 10 to 1 and the nozzle pressure ratio (NPR) being changed from 1 to 10 in steps of 1 for base pressure measurements. The area ratio for the entire analysis is fixed at 2. 56. Wall pressure distribution along the enlarged duct is also recorded. No change in base pressure increase/decrease is thoroughly analysed as well. From the experimental investigation, it is found that control plays an important in modifying the base pressure without disturbing the wall pressure distribution. The base pressure variation is entirely different at L/D = 1 compared to a higher L/D ratio due to change in reattachment length and the requirement of the duct length at higher inertia levels. The quality of the FLOW in the duct in the presence and absence of control remained the same.

Different FLOW patterns of downward gas-liquid two-phase FLOW using simple mixer are studied in an experimental manner. An experimental setup is designed and fabricated to allow the visual observation of downward two-phase FLOW patterns and their transitions. The FLOW patterns are recorded by a 1200 frames per second high speed video camera. The quality of downward two-phase FLOW patterns photos are improved through image processing. The setup includes a transparent vertical pipe of 50 mm diameter and the (L/d) aspect ratio of 80. FLOW patterns are obtained through 374 test cases during which air and water superficial velocities changed. In order to assess the performance of the mixer, all expected FLOW patterns are obtained. The four observed FLOW REGIMEs are: of falling film, bubbly, slug and froth. The FLOW map is plotted and transitions among different FLOW patterns are compared with previous finding in specified conditions indicating a good agreement was observed.

One of the essential areas of the study of transport in porous medium is the FLOW phenomena at the onset of inertia. While this area has attracted considerable research interest, many fundamental questions remain. Such questions relate to things such as the nature of the multi-dimensional velocities of the FLOW, the evolution of inertia, the differences in FLOW phenomena at various complexity of porous media, and the best constitutive equation for the FLOW. To resolve some of these questions, the present research program was designed to experimentally investigate pressure-driven FLOW through two-and three-dimensional porous media at the onset of inertia. Specifically, the goals in view were to obtain velocity data and pressure measurements, apply the benchmark experimental data to study the evolution of inertia, distinguish differences in such evolution with respect to the parameters of the porous media, and to establish the constitutive equation that best describes the porous media FLOW when inertia sets in. What particularly sets this work apart, is the use of particle image velocimetry (PIV) – an experimental technique that captures multi-dimensional FLOW quantities, as opposed to mere FLOW rates. Using PIV then, detailed velocity measurements were conducted for FLOWs through model porous media of solid volume fraction 6%, 12%, and 22%. The velocities were spatially averaged to obtain average streamwise and transverse components. In addition to the velocity measurements, differential pressure measurements were obtained using pressure-measurement gauges and transducers. The pressure and velocity data sets were then statistically analyzed and presented to provide a complete set of experimental data to characterize the FLOW through the model porous media. The results show that the velocity FLOW domain is dictated by the streamwise velocities, which are at least an order of magnitude greater than the transverse components. Furthermore, pressure drag was found to increase with compactness and complexity of the porous media. While inertia increases exponentially from particle Reynolds number ~ 1 – 3 onwards, it is apparently subdued by the form drag that tends to dominate the FLOW through complex media. Overall, the FLOW at the onset of inertia is best described by a power law. These results provide insights that are applicable to FLOWs such as those near well bores and fractures where seepage velocities are relatively high.

In this work computational fluid dynamics is used to describe the fluid FLOW across a randomly packed absorption tower. The CFD simulation method is employed on a packed tower that is packed with 1cm Raschig rings. Tower is 175cm in height. Air FLOW rate range was 1.5 to 5 m/s. The measured pressure drops were in 1.5 to 12 Pascal per height of tower in meter. The Klerk’s approach is examined to define the influence of confining walls on pressure drop in packed areas. It is concluded that CFD model that uses the Klerk’s definition of radial porosity distribution is a successful way for pressure drop prediction in packed beds. Model prediction of dry pressure drop is about 4% lower than the experimental measurements. Ergun’s pressure drop prediction is compared with that of Reichelt’s using averaged and distributed porosity profiles. In both methods Ergun’s approach in comparison with Reichelt’s approach has %6 lesser error in dry pressure drop prediction.