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The terminal velocity and coefficient of friction data are necessary for designing of handling and separating equipments. The terminal velocity data are also valuable in designing pneumatic conveying, fluidized bed dryer and cleaning equipments. In this paper, the terminal velocity and coefficient of static friction of saffron flower and its components (stigma, stamina, petal and stem) were determined as a function of moisture content. The experiments were conducted on saffron flower selected from fields of Kashmar. The data was statistically analyzed using factorial experiments with completely randomized design. The results showed that the terminal velocity of the saffron flower, stigma, stamina, petal and stem at moisture content of harvesting level to 40% (w.b.) were in the range of 1.03 to 5.13 m/s. With decreasing moisture content from harvesting level to 40% the terminal velocity of the flower and stem decreased significantly but the terminal velocity of the stigma, petal and stamina were not decreased significantly. The terminal velocity of the petal was the minimum value at the three moisture content levels. The coefficient of friction of saffron flower and its components on the friction surfaces were in the range of 0.52 to 1.1. The friction coefficients of all the components except the stem were the maximum values on polyethylene surface. The coefficients of friction were the minimum values on galvanized iron surface for all of the components. With decreasing moisture content from harvesting level to 40% (w.b.) the average values of coefficient of friction increased significantly for all of the components. The coefficient of friction of the stigma and flower were the maximum and minimum values, respectively at different levels of moisture content. Generally, at moisture content of harvesting it is possible to separate the flower, petal, stamina, stigma and stem from each others with changing air stream velocity. As well, it is possible to separate the petal from the others components at moisture levels of 70% and 40% (w.b.) using wind column device.  

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Knowledge of the aerodynamic properties of agricultural materials is needed in equip-ment design for operations such as pneumatic conveying in loading/unloading operations of corn silage into/from silos. While considerable information is available on seed grains, little is known about the aerodynamic behavior of corn (Zea mays L.) silage. In this re-search, the weighed mean terminal velocity of a sample representative of the entire bulk mass was determined using Wolf and Tatepo’s method. The terminal velocity of various particle types (leaf, stalk and corncob pieces) of chopped forage corn plants, which were kept in silo for six months, at different moisture contents (40-50, 50-60 and 60-70% w.b.) was also studied. The terminal velocity was determined by measuring the air velocity re-quired to suspend a particle in a vertical air stream using a wind tunnel. A 3 3 factorial treatment arrangement with 30 replications in a completely randomized design was used to study the effect of moisture content and particle type on the terminal velocity. The mass mean terminal velocities of the corn silage at 40-50, 50-60 and 60-70% moisture con-tents were 7.1, 7.3 and 7.8 m/s, respectively. The results showed that only the effect of par-ticle type on the terminal velocity of corn silage was significant. The mean values of the terminal velocity of corn leaf, stalk and cob pieces were 3.8, 6.8 and 8.8 m/s, respectively. For each particle type at a given moisture content, the terminal velocity was best de-scribed by means of the equation of velocity squared in terms of weight.

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In order to provide the data needed for the design of saffron processing equipment, physical properties of its flower were investigated. These properties included dimensions, mass, true and bulk densities, porosity, static and dynamic coefficients of friction, and terminal velocity as a function of moisture content. The average range of these properties for the three different parts of saffron flower was about 0.03 to 0.16 gcm-3 for bulk density, 0.55 to 1.56 gcm-3 for true density, and 85.2 to 95.5% for porosity. Also, the coefficients of friction were measured for three flower parts by using three surface materials including plywood, iron, and galvanized steel sheets. The minimum and the maximum values of static coefficients of friction were found on galvanized steel sheet. They were 0.8 and 2.14 for anther and stigma, respectively. The dynamic coefficient of friction ranged from 0.45 for anther on iron to 1.14 for petal on galvanized steel sheet. The variation range of terminal velocity for three different parts of the flower was recorded between 0.9 and 2.38 ms-1. The results of friction coefficients and terminal velocity measurements suggest that, based on these properties, design of a separator for saffron flower parts is feasible.

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In recent years, pneumatic method of stigma separation has been considered by some researchers. In this regard, computer simulation of the process is necessary as well as determination of the engineering properties of the various flower parts. According to preliminary observations, the number of flower components, their characteristics, and the simulation of the separation process, all depend on the flower cutting location. In this study, cutting of flower was done in two modes. In the first mode, the flower was cut from the top of the receptacle and divided into three parts including petals (2), stamens (3) and a three-branch stigma. In the second mode, the cutting accomplished from the bottom of the receptacle and the flower divided into two parts including flower without stigma, and a three-branch stigma. Variations in weight, density and terminal velocity of different flower components were studied as a function of moisture content. According to the results of this study and in contrast to most of the published papers, vertical wind tunnels are not suitable for pneumatic separation of saffron stigma. In order to provide required information for computer simulation, the flower components were considered as spherical particles, and then their aerodynamic diameters were calculated using the proposed flowchart. The results showed that the difference in aerodynamic diameter values in the two-section cutting mode reach to significant amount of 70%. Results of present study also indicate that the appropriate stigma separator mechanism should have singular feeding system and ability to provide turbulent air flow. Preliminary results obtained from computer simulations are hopeful in the case of using dual internal tunnels equipped with rotational flow.

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The falling and sedimentation of solid particles in liquids occur in many natural and industrial processes such as water and waste water industries, biotechnologies, environmental engineering, marine engineering, etc. This study represents the results of the experimental study of the falling velocity of steel balls in the water channel for different ball diameters (in the range of 8 to 25mm). The tests are done far from the channel walls. Moreover, as a case study, the wall effect on falling velocity of steel ball (i.e. diameter=12mm) is examined. A high-speed camera is used to determine the coordinate of a falling sphere and estimate the ball velocity and drag coefficients. In addition, a numerical method is used to solve the governing equations in comparison with experimental data. Comparing experimental and numerical results for transient and terminal velocities shows the maximum difference of 12 and 4.5% respectively. Experimental drag coefficients have good agreement with other published data. In addition, falling near the wall leads to a negligible effect on velocity but path diversion is observed.