tailieunhanh - HANDBOOK OF SCALING METHODS IN AQUATIC ECOLOGY MEASUREMENT, ANALYSIS, SIMULATION - PART 5

Wainwright và Dillon (1969) số lượng veriÞed giả thuyết lâu nay rằng fan hâm mộ hướng biển không phải ngẫu nhiên, trên thực tế, người hâm mộ biển định hướng ưu tiên để lưỡi của mình vuông góc với ßow của nước. Họ phát hiện ra rằng các fan hâm mộ biển lớn hơn độ lệch của một fan hâm mộ cá nhân từ định hướng trung bình của tất cả những người hâm mộ kiểm tra. Trong số những người hâm mộ biển lớn nhất, những người bằng hoặc lớn hơn 50 cm chiều cao, không có thay đổi hơn 20 ° từ. | 20 Orientation of Sea Fans Perpendicular to the Flow Thomas Osborn and Gary K. Ostrander CONTENTS The Rayleigh Sea Fan Effects of the Bottom Boundary Orientation Relative to the Local Discussion and References 327 Introduction The orientation of sea fans and sea pens Figure to the flow has been attributed to hydrodynamic phenomena without any detailed explanation of the reasons . Laborel and Vacelet 1958 Theodor and Denizot 1965 . There are two possible mechanisms through which the natural torque on the fan can cause the population to align with the axis of the dominant flow. 1. The torque applied to the stalk by the flow is sufficient to reorient the fan perpendicular to the flow as it grows or 2. The survivability of the fans with correct orientation within certain angular bands is dramatically better than the fans with improper orientation. Wainwright and Dillon 1969 quantitatively verified the long-held hypothesis that sea fan orientation was not random and in fact sea fans preferentially orient so that their blades are perpendicular to the flow of the water. They found that the larger the sea fan the less the deviation of an individual fan from the mean orientation of all the fans examined. Among the largest sea fans those equal to or greater than 50 cm in height none varied by more than 20 from the mean orientation of all those examined n 58 . In fact the average variation was only slightly more than 8 from the mean calculated from data in Wainwright and Dillon 1969 . The investigators also concluded that small fans 20 cm are oriented randomly and that there is an increase in the degree of preferred orientation with increasing size. Wainwright and Dillon 1969 also resolved the issue of the mechanism utilized by the sea fans for achieving the preferred orientation as they increased their size. Through examination of .