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Bridge pier's local scouring is known to be a destructive factor in river engineering science. This phenomenon is widespread in river intersecting structures such as bridge piers, spur dykes, and downstream river structures. Extensive research has been conducted to reduce and control destructive phenomena, and many solutions have been proposed. These solutions are divided into two parts, namely, direct and indirect protection. In this study, the direct method was studied by defining scenarios. Since many bridges are affected by scouring during the operation, in the present study, the collar method, which is known as a direct protection method, in the case of flexible and permeable, is suggested. The technique is presented an adjustable chain collar, three times bigger than the pier's width (w/d=3), and its effect is investigated in clear water conditions. In the defined scenarios, three different diameters of the chain as CI=5 mm, CII=10 mm, and CIII=15 mm were used to control chain shapes' effect, and three dimensionless flow parameters (U/Uc 0.73, 0.85, and 0.96) were selected to investigate the effect of flow conditions. According to the results, the scour depth is related to changes in the diameter of the collar chain, as the final scour depth decreases by increasing the diameter of the chain from CI to CIII. Therefore, in the best conditions, for CIII, the dimensionless ratio of scouring reduction ( ) is equal to 71% near to inception motion parameter (U/Uc=0.96).

In this investigation, a numerical method based on potential flow for aerodynamic analysis of BWB aircrafts has been developed. At first, results of this method are validated with experimental data and then, three current BWB planforms have been chosen and analyzed to determine suitable planform for BWB aircrafts. The results show that aerodynamic characteristics of (A) and (B) planforms are better than (C) planform. On the other hand, the (A) planform has better a uniform lift distribution along the span, less induced drag, more space and less noise than (B) planform. Finally, the (A) planform is a suitable configuration for BWB aircrafts.

The effect of sail position on the downstream flow field of the sail is investigated in the wind tunnel. A five-hole pressure probe is used to measure the 3D flow field. The investigation of the five-hole results shows that the five-hole measurements can determine the horseshoe vortex structure. Also, the results show that the horseshoe vortexes become smaller by forward moving of the sail on the body to the nose. Therefore, if the sail is mounted on the hull near the bow, the performance of the impeller increases and nose level decreases. [ABSTRACT FROM AUTHOR]