Carrying Capacity of a Flow with Flow Rounding under Permafrost Conditions
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Vol. 54, No. 3, September, 2020
CARRYING CAPACITY OF A FLOW WITH FLOW ROUNDING UNDER PERMAFROST CONDITIONS V. K. Debol’skii,1 O. Ya. Maslikova,2 and I. I. Gritsuk3 Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 3, March 2020, pp. 36 – 40.
Under natural conditions in winter, narrowing of a flow due to partial freezing of the channel and formation of a slush ice run or ice jam, as a result of which flow speeds increase in sections of the turn of the channel, is characteristic. Laboratory experiments that have been carried out in the rotary installation of the hydraulics laboratory at the to model such a section, have shown that if the flow speeds entering the curvature increase or there is an increase in the Reynolds number, vortex motions and counterflows at the inner slope inevitably occur, which inevitably is shown in the nature of the channel washout. Keywords: flow rounding; counterflow; eddies; soil erosion; thawing.
The intensity of destruction of banks in the discontinuous frozen state zone, the boundary of which is moving northward, is caused by the fact that the erosion of the underwater part of the bank slope occurs from the effect of the mechanical and thermal energies of the flow, and the intensity of this erosion depends on the temperature [1] and ice content of the soils [2]. A section where there is gradual development of circulation [3] precedes the flow ahead of the turn. The turn itself causes a redistribution of speeds across the width and verticals of the channel cross section (Fig. 1). In the curve itself, due to the exchange of momentum between the estimated stream flows caused by transverse circulation, there occurs a redistribution of velocities and the maximum speed gradually moves to the external concave bank. Upon exit from the curve, where the centrifugal force and transverse inclination are no longer in effect, the vertical with maximum velocity turns out to be present for a considerable stretch at the prolongation of the concave bank. This change of speeds in turn causes a change in action on bank erosion. On the circular experimental setup for studying a flow with possible accounting for the Coriolis force due to rotation of the centrifuge around a central axis, a laboratory test of flow motion on a curve was conducted, where the behavior of frozen and unfrozen soil, the effect of snow cover on erosion of a bank slope, the effect of the direction of flow about the circle (effect of Coriolis force), and also the change in the carrying capacity of the flow as velocity increased was studied.
Studies of permafrost are closely associated with other sectors of science: geology, geomorphology, physics, construction, and climate change. Nevertheless, in recent decades, although there have been significant advances in the sector for study of frozen earth, the number of works linking all processes and demonstrating the response of permafrost to external influences has been very small. Observations of recent years indicate an evident trend of permafrost thaw on the lands of Russia, and
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