flow pattern

Deficiency of potable water has created many problems for human and human society, Therefore, The production of fresh water from saline water is an important issue. One of the method of production fresh water from saline water is the use of solar stills. This paper is the numerical simulation of the conventional solar stills with setting Rectangular, Triangular, Wavy barriers on the left and right walls inside the solar still. Setting barriers causes a change in the pattern of humid airflow in the solar still that it affect water productivity and convective heat transfer rate. Also, changes in the size and number of barriers cause changes it will be in the result. The continuity, momentum, energy and concentration equations are discretized by finite volume method and the results are presented as flow function and concentration and temperature contours. The simulation results show that setting wavy barriers with A=0.01(m) and N=2 at left wall and A=0.075(m) and N=5 at right wall water productivity and convective heat transfer rate can be increased by about 31% and 31.34%.

Investigating the flow pattern developed whitin spaces with relatively large scales that can be caused by forced or natural convection is of particular importance based on which, one can comment on the spread of polluting particles, temperature distribution and thermal comfort conditions. Calculating the developed flow field whitin such spaces using numerical methods, requires relatively large memory and long calculation time. Whereas, suitable zonal methods can predict accurate flow patterns with a very small amount of calculations. In the present research, equations similar to that of one-dimensional flow passing through an orifice, which is known as the zonal power law method, were used to predict the flow between the adjacent cells. These equations along with the mass conservation equation defined for each cell of the domain were solved using an innovative numerical method and the velocity distribution was specified. The 2-D sample domain had 1 m height and two different lengths of 0.5 and 2 m where the air inlet and outlet were considered at different positions. The air velocity at the inlet was 2 m/s. In order to make a better match with the experimental results, variable loss coefficients between the cells were used and significant improvement was found in the results. Despite the comformity made in the velocity distribution, the existence of recirculating flows predicted by the numerical methods could not be obtained using the employed method even with the variable coefficients.

Wingsuit flying is one of the most popular flight disciplines in recent decades. In the aviation profession, efficiency and safety are paramount concerns for costume designers. An article in this issue examines how waveform changes to the wing surfaces of a wingsuit model improves aerodynamic performance. In order to increase performance, vortices are produced inside the boundary layer that improve the exchange of motion. In this experimental and numerical study, we investigate the formation and evolution of vortices in the Reynolds number range of 106 and provide insights into flow patterns on surfaces with geometric changes. A detailed study of flow structure can be obtained from experimental and numerical evaluations. According to the results, there are significant vortex generators near the backpack due to high pressure. Immediately after the creation of these vortices, the flow is drawn and spread on the surface of the wing in three dimensions. As a result of the angle of attack, the wing surface separates prematurely. Based on the lift and drag coefficients, the study model showed the best performance in flight at an angle of attack of 10 degrees for this flow regime.

A compound open channel is composed of the main channel and flood plain. In experiments with compound open channel conducted to ensure that the flow is uniform and fully developed, it is necessary to study the distribution of discharge in the main channel and flood plains. The purpose of the present study is to investigate the effects of channel inlet condition on flow uniformity by considering distribution of discharge in channels with length to flood plain width ratio lower than 35 (needed for fully developed flow condition) by analyzing the flow field and turbulence parameters. For this purpose, particle image velocimetry method has been used in a rectangular compound open channel. To provide correct measurement of secondary velocities, using a non-intrusive method such as particle image velocimetry is completely essential. The results of this study show that in short compound channels with the same screen installed in the main channel and flood plain, there is significant mass transfer from the flood plain to the main channel until the end of the channel length. It was found that in this case, a considerable downfall occurs for the maximum velocity position in the main channel. However, with a supplementary screen installed in the flood plain, in addition to the typical screen, expected conditions are established similar to the fully developed compound channels. In this condition, the time-averaged streamwise velocities vary considerably in the flood plain along the spanwise direction. On the other hand, in short compound channels with the same screen installed in main channel and flood plain, the streamwise velocities do not change significantly along the flood plain width duo to the imperfect interaction of main channel and flood plain. These observations express that to provide correct distribution of discharge, a supplementary screen should be installed in the flood plain of the compound channel.

The purpose of this study is to generate two-phase flow patterns and to obtain a flow pattern map for two phases as water and air in a vertical pipe which is made of transparent Plexiglas. The pipe specification is 50 mm diameter and 390 cm length. In this attempt the average velocity of the Taylor bubble will be calculate. In order to facilitate this research work, a two phase flow was designed, built and adjusted at Tarbiat Modares University Two-phase flow laboratory. Three flow patterns as bubbly, slug and churn flow are generated and examined for 320 runs of different superficial velocities of air and water. A seven-layer distributor with the ability to change the number of bubbles produced is used to create a bubbly flow pattern at the air inlet. The effect of the superficial velocities of each phase on the flow pattern was evaluated and a flow pattern map was presented for 320 different data. By processing the images obtained from the high-speed camera, the average Taylor bubble velocity was calculated for different flow conditions with uncertainty in calculating the velocity. Also, for 5 different velocities of the liquid phase, a diagram of the average velocity of Taylor velocity with increasing gas velocity was drawn and compared with the Nicklin correlation which can be found in the literature

In this research, it has been tried to experimentally investigate the the effect of personalized ventilation system on air flow and temperature distribution in a room for two inlet air temperatures (24 and 32°C) and two different arrangements of the inlet diffusers (desk-mounted and under-desk air terminals). The results showed that the penetration depth of heat and momentum due to the inlet diffuseres were not the same; So that the effect of inlet diffusers’ temperature on the room temperature distribution is significant up to a distance of about 60 cm. However, the effect of inlet velocity is noticeable up to a distance of about 110 cm. As a result, the occupants’ thermal sensations up to about one meter from the inlet diffusers will be affected by the inlet conditions. Also, the results indicated that the draught dissatisfaction along with the diffusers’ centerline is significant to a distance of about 180 cm. Also, based on the results, the air velocity and turbulence intensity are the two main factors in determining the draught dissatisfaction in the personalized ventilation system and due to the rapid thermal mixing of inlet air with the room air, the effect of inlet temperature on the draught dissatisfaction is not significant.