Terminal velocity and drag coefficient are the most important aerodynamic properties of agricultural products like soya in the designing of machines and processing equipment. In this study, these properties were evaluated for three soybean varieties (Sahar, Viliyams and Dpx) and five moisture content levels (4, 8, 12, 16 and 20% d.b.). First, relation of the terminal velocity and the drag coefficient with the moisture content was mathematically formulated, and then, in fluidized bed dryer was practically investigated. The results showed, with the changing of the moisture content of three varieties (Sahar, Viliyams and DPX) from 4% to 20%, the terminal velocity of three varieties increased respectively from 4.42 to 5.1, 5.12 to 5.94 and 4.71 to 5.5 (m/s) while at the same moisture content the drag coefficient decreased from 0.45 to 0.389, 0.53 to 0.452 and 0.512 to 0.444. The diagrams of the terminal velocity and the drag coefficient revealed that the terminal velocity and the drag coefficient values have a linear relationship with the moisture content, but with increasing the moisture content, terminal velocity values increased whilist drag coefficient ones decreased.

Knowledge of the aerodynamic properties of agricultural materials is needed in equipment 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 research, 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 required 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 contents were 7.1, 7.3 and 7.8 m/s, respectively. The results showed that only the effect of particle 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 described by means of the equation of velocity squared in terms of weight.

Determining the terminal velocity as one of the important aerodynamic properties of particles and grains is essential for pneumatic separation, grading, and handling. A wind tunnel system was used in the present research to measure the aerodynamic terminal velocity of pistachio nuts. Some physical properties were measured and calculated. The effects of pistachio mouth status at four levels (closed, open, and semi-open mouth, and shell) were investigated on its terminal velocity. The volume, mass and density of that were 1.33±0.37 cm3, 0.97±0.31 g and 0.72±0.18 g cm3-1, respectively. The average aerodynamic terminal velocity of pistachio was 9.43±1.38 m s-1. The aerodynamic terminal velocity of the pistachio had a direct relationship with the studied physical characteristics, except for density. The terminal velocity of open-mouth pistachio nuts (9.50±0.61 m s-1) was significantly lower than that of closed (10.12±0.51 m s-1) and semi-open mouth (10.16±0.62 m s-1) nuts, with the terminal velocity of the shells (6.51±0.65 m s-1) showing the lowest values. The results revealed that terminal velocity can be considered for pneumatic separation of shells from pistachio nuts as well as the separation of open-mouth nuts from closed-mouth ones.

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.

Hydrodynamic and mass transfer simulations of toluene rising drops have been investigated. The VOF-PLIC method with surface tension model of CSS was applied. Drops have been simulated in the three regimes of spherical, circulating, and oscillating regimes. Simulation results agreed well with existing experimental data with the average relative error of 3.63 percent. The current hydrodynamic model predicted the oscillating regime for the drop diameter of 4.4 mm and 3.5 mm drops were identified as the drops with maximum velocity. These findings agreed well with existing experimental data. In the next step of simulations, mass transfer equation was supplemented into the simulations investigating mass transfer effect on the velocity of 2 mm toluene drops. All of the properties of drops were assumed constant except surface tension coefficient. Simulation results showed that, with the assumption of concentration dependent surface tension coefficient, terminal velocity relative error was about 2 percent, while without considering of that, relative error increased to 83 percent. Streamlines, drop shapes, axial velocity, and terminal velocity were also reported.

The present experimental study was done aimed to investigate dynamic ofa single bubble rising through wall-bounded flow at high Reynoldsnumber. Thus, Rhamnolipid biosurfactant was added to stagnant fluid andbubble diameter was controlled between 2.5 and 3.5mm. The resultedReynolds number was in the range of 400 to 900 depends on biosurfactantconcentration. Rhamnolipid has a low toxicity, a high biodegradabilityand good stability at a wide range of temperatures. The results showedthat terminal velocity linearly depends on Reynolds number. Furthermore,drag coefficient is related to Eötvos number and is autonomous toReynolds number. Finally, to estimate terminal velocity and dragcoefficient, four empirical correlations were developed. Relative errors ofthe proposed correlations were less than of 3.35% and 1.97% for velocityand dimensionless velocity equations, respectively, and average errors oftwo equations proposed for drag coefficient were 4.44% and 3.26%.

This study addresses the measurement of three-dimensional (3D) bubble rising behaviour in still water with bubble equivalent diameters ranging from 2.61 mm to 5.11 mm using high-speed imaging and virtual stereo vision technology. The bubble shape, 3D trajectory/velocity, displacement angular frequency and terminal velocity of bubbles are analysed. The bubble equivalent diameter is obtained by the elliptic volume method. The bubbles are divided into small and large bubbles with a critical equivalent diameter of 4.49 mm, according to whether they are accompanied by deformation. The small bubbles (deq<4.49 mm) are spherical or ellipsoid, while the large bubbles (deq≥4.49 mm) exhibit ellipsoid, mushroom and hat shapes. The 3D trajectory is obtained by 3D reconstruction of bubble centroid coordinates. The rising trajectory of small bubbles shows 3D spiral motion, while the pitch increases gradually with the increase in the equivalent diameter. The trajectory of large bubbles is a two-dimensional (2D) zigzag. The bubble displacement curves in x- and z-directions are evaluated with third-order Fourier fitting. The results show that the bubble displacement frequency in the x and z-directions decreases with the increasing bubble diameter, and the displacement frequency in the xdirection is larger than that in the z-direction. The relative proportions of the viscous force, buoyancy, surface tension and inertial force on bubbles with different equivalent diameters are different, which leads to three trends in the vertical velocity of bubbles within the diameter range of this study. Finally, the bubble terminal velocity in still water is investigated. The terminal velocity first decreases and then increases with the increase in the equivalent diameter. The minimum value is 16.17 cm/s when the diameter of the bubble equivalent diameter is 4.49 mm. Moreover, the applicability of some classical prediction models is discussed.

This research was conducted with two varieties of almond kernel (thin shell and semi stone shell) for five moisture levels (5%, 10%, 15%, 20%, 25% d.b.) with five replications using completely randomized base factorial design. The results showed increases with increasing moisture content from 5% to 25% for the thin shell almond for the following variables: true density (851.12 to 1138.94 Kg/m3); porosity (35.69 to54.45%), terminal velocity (4.81 to 6.18 m/s); static friction coefficient on Plexiglas (0.471 to 0.591); static friction coefficient on galvanized iron (0.417 to 0.552); projected area (1.45 to 1.67 m2); repose angle (18.26° to 27.59°). Corresponding values for the semi stone shell almond were: true density (897.18 to 1123.84 Kg/ m3); porosity (32.09 to 47.22%); terminal velocity (5.35 to 6.53 m/s); static friction coefficient on Plexiglas (0.368 to 0.458); static friction coefficient on galvanized iron (0.356 to 0.447); projected area (1.36 to 1.53 m2); repose angle (16.33° to 22.45°). The results also showed that bulk density decreased as moisture content increased from 5% to 25% for the thin shell (547.26 to 518.76) and semi stone shell (609 to 592.94 Kg/m3).

Knowledge of physical properties of fruits is requirement and necessary for design and optimization of food processing machinery. In this study, some geometrical properties (length, width, thickness, geometric mean diameter, arithmetic mean diameters and surface area), gravimetrical properties (unit mass, true density, bulk density and porosity) and physical and aerodynamical properties (static coefficient of friction and the terminal velocity) of Ahmad aghaei pistachio nut variety in five moisture content 4.6%, 12.35%, 20.1%, 27.85 and 35.36% of basis on wet were measured and evaluated. The effect of moisture on length, width, thickness, geometric and arithmetic mean diameters and surface area of pistachio and its kernel were nonlinear and linear, respectively. Values of unit mass, true and bulk density were increased linearly by increasing of moisture content. However, the porosity of pistachio and its kernel were decreased linearly by increasing moisture content. The highest and lowest value of friction coefficient of pistachio nut and its kernel were obtained on plywood and galvanized iron sheet, respectively. The terminal velocity of pistachio nut and its kernel were increased linearly by increasing moisture content and located in the range of 10.59-11.6 m/s and 9.16 - 10.8 m/s, respectively.

In order to design and manufacturing some postharvest equipment, determination of some hydrodynamic properties of crops are necessary. The quality of products in global and local markets can be increased by applying these properties and receive economical benefits. For these purpose, two local varieties of apples in the East Azerbaijan province, Iran(Asheghi and Gare Yapraq)were selected.Asheghi and Gare Yapraq apples varieties  were randomly hand picked in  two times (14th and 23th July, 2012) ,and in one time (14th July, 2012) respectively. Then some of their physical and hydrodynamic properties such as mass, density, volume, projected area, terminal velocity, drag, bouncy and gravity forces were studied. The mean values of mass of fruit, density, volume, projected area, terminal velocity, drag, bouncy and gravity forces of Asheghi variety for first harvest time, were 47.57 gr, 773.23 kg m-3 , 61.71 cm3, 32.23 cm2 ,0.40 m s-1, 0.12 N , 0.61 N, 0.42 N and for second harvest time, 58.82 gr , 765.81 kg m-3, 77.06 cm3, 25.80 cm2, 0.43 m s-1, 0.11 N, 0.76 N, 0.52 N respectively. The corresponding value for Gare Yapraq variety were obtained as 66.42 gr, 712.67 kg m-3 , 93.43 cm3, 45.38 cm2, 0.52 m s-1, 0.29 N, 0.92 N, 0.60 N  respectively.