Some general characteristics of the observed plasma motions in the actlve region are described. The data concerning the birth and evolution of sunspots, intrinaic internal motiona, the balance of plasma fluxes in individual sunspots and in the active region as a whole are presented. Special attention is paid to rotational plasma motion in sunspots and torsional oscillations of the spots. The.
importance of data on torsional oscillations of aunspots has been established for the study of the magnetic field structure and plasma convection in subphotospheric layers of the Sun.
Recent studies have shown that the presence of ice cover leads to an intensified local scour pattern in the vicinity of bridge piers. To investigate the local scour pattern in the vicinity of bridge pier under ice-covered flow condition comparing to that under open channel flow condition, it is essential to examine flow field around bridge piers under different flow conditions. In order to do so, after creation of smooth and rough ice covers, three-dimensional timeaveraged velocity components around four pairs of bridge piers were measured using an Acoustic Doppler velocimetry (ADV). The ADV measured velocity profiles describe the difference between the velocity distributions in the vicinity of bridge piers under different covered conditions. Experimental results show that the vertical velocity distribution which represents the strength of downfall velocity is the greatest under rough covered condition which leads to a greater scour depth. Besides, results show that the turbulent intensity increases with pier size regardless of flow cover, which implies that larger scour depth occurs around piers with larger diameter.