The effects of suction on the structure of a transitional bubble forming on a low-Reynolds-number airfoil are examined using the Reynolds-averaged Navier–Stokes and k–kL–ω transition model. The suction effects on the laminar and turbulent portions of the separation bubble and the locations of the main points in the separation bubble are discussed in relation to the transition process of the bubble. A single suction distribution located in the region of the baseline transitional bubble is used with two suction rates. One suction rate is sufficiently strong to eliminate the bubble from its original location and a lower suction rate that is only sufficient to create shallower bubbles. Eliminating the bubble from its original location maintains a laminar boundary layer downstream of the baseline transition location until a shallower separation bubble forms near the trailing edge. The lower suction rate shortens the separation bubble and reduces its height while approximately maintaining its original location. Analyzing the lengths of different portions of the bubble suggests that suction affects the instability growth rate and the nonlinear interactions in the separated shear layer. The lower suction rate shortens the distance between the separation and transition onset suggesting a higher growth rate of the inviscid instability. The higher suction rate, on the other hand, increases the distance between the separation and transition onset indicating a stabilizing effect by slowing down the growth rate of the inviscid instability. However, the percentage of distance between transition and separation to the total length is only slightly affected by the suction and the angle of attack.
Abstract
The back pressure of a gas–liquid swirl ejector is a critical parameter that affects the flow regime and entrainment performance of the system. In the case of a weak swirl injection, the motive jet carries relatively higher axial momentum thus remains in a single phase and the liquids appear glassy. With increasing in the back pressure of the bubble flow, the suction rate drops rapidly. For a strong swirl injection, the liquid jet is disintegrated due to higher angular momentum and the spray is atomized. Augmentation in the back pressure also causes the reduction in the suction rate but it tends to grow more gradual than the weak swirl injection. As a result, the suction rate of the strong swirl is greater than that of the weak swirl in the majority of the back-pressure range. However, owing to the high transition pressure, only the weak swirl entrains the air in the bubble flow regime at low back pressure. The relationship between the suction and the swirl intensity is not fixed and is influenced by the back pressure.
Bricks are one of the building materials that serves as a wall or anchoring the load. Therefore, it must be made according to the standards. In our previous observations, many found bricks were traditionally not quality, because the process of making bricks that are not right. Bricks are a class of ceramic materials that must be hard and should not be crushed when immersed in water. The method in this study focuses on optimizing compaction pressures, with printed pressures that are varied in MPa units. The results obtained as follows, in terms of mechanical properties of Compressive Strength increases with the addition of compaction pressure, an increase of 36% (brick becomes strong). In terms of physical properties of Density increased (porosity becomes smaller). For Suction rate down, this shows less water absorption. The results obtained in accordance with national and international quality standards.
There are many cases where a coastal dike or a seawall constructed on a very shallow area was broken by a wave of a smaller height than the designed height. In many of these cases, the reason of the destruction was the suction phenomena. This phenomenon happens when waves reaches the front of the dike or the seawall, the wave pressure scours the front soil of the structure until it reaches the lowest edge of the structure followed by sucking of backfilling material of the structure. In this research, the authors proposed the numerical model which can calculate the suction rate with elapsed time by applying the pore water pressure and the flow velocity inside a dike or a seawall using “CADMAS-SURF”. The authors proposed three coefficients for improving the calculated pressure from CADMAS-SURF. The reliability of the model was confirmed by reproducing the suction phenomena in Hirono Coast of Japan.
Cocoa bean winnowing has a function to separate cocoa nibs from shell after roasting process of dry bean. Nibs are further processed into fine cocoa liquor by refining process. The aim of this experiment was to evaluate working performance of a home-scale winnower to separate shell from nibs with minimum shell parchment content in cocoa nibs. This experiment was conducted in Postharvest Laboratory at the Indonesian Coffee and Cocoa Research Institute using roasted cocoa bean grade A according to standard of SNI 2323:2008/ Amd1:2010 with shell content of 15% originated from Forastero cocoa. Working performance of the home-scale winnower was evaluated based on shell parchment content in the output, its capacity, energy consumption and power transfer efficiency value by several air suction rates as variable. Data were analyzed using regression and variance analysis to evaluate the influence of the rate and to determine the optimum machine operation. Results of regression and variance analysis from winnowing experiment with air suction rate of 0.54 m/s; 0.63 m/s; 0.72 m/s and 0.90 m/s indicated that shell parchment content in cocoa nibs and power transfer efficiency value were affected by the rate. The optimum machine performance was obtained on 0.72 m/s of air suction rate with total winnowing capacity was 2.615 kg/hour, energy consumption of 132 Watt, power transfer efficiency value of 61.01% and shell parchment content was 1.06%. Shell parchment content in cocoa nibs was appropriate regarding to the SNI standard with maximum content of 1.75%.
A swirl body inserted into the entry of the primary fluid to a venturi-ejector influences the subsequent mixing of the two fluids and increases the suction rate of the ejector. An experimental facility has been developed to study the influence that a variation in the swirl angle has on the operational performance of a model venturi-ejector. Water and air were the primary and secondary fluids employed. Three swirl body configurations representing three different swirl angles were inserted upstream of the entry nozzle and the resultant downstream flow mixing characteristics were studied. The performance of the venturi-ejector with and without the use of the swirl body inserts was compared. The paper presents a description of the experiments performed and an analysis and discussion of the results obtained from this initial experimental study.
The water absorbent resin is a new type of polymer plugging materials developed in recent years, the water swelling with certain viscoelastic gel, with a certain intensity, strong water retention, salt resistance and stability. Polymerization aqueous solution of acrylic acid (AA), acrylamide (AM) as the experimental materials, the choice of a controllable expansion sealing agent the KP to determine the formula developed by the sealing agent, and has good suction rate, anti-performance of salt and water retention.
Optimization of compaction pressure on brick