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我国北方地区的明渠,冬季运行常面临冰害问题。为消除明渠冬季运行冰害,工程实践中常通过控制水流条件(水温、流速、水深等)而使其形成冰水二相流输水方式或结冰盖输水方式。以冰水二相流方式输水,对明渠的过流条件要求较高(流速≥1.2m/s、水深≥1.5m、流冰花疏密度η<60%、弯道曲率半径 R≥8B 及转角等),而且在运行中常具有一定风险;而采用结冰盖方式输水,当冰盖结成后,明渠冬季运行中的许多困难都会消除,因其能安全可靠地避免冰害,而为许多输水工程所采用。当地的气象条件决定了可采用的明渠冬季运行方式。结冰盖运行的明渠其水流控制条件为 F_(rc)≤0.09,V_c≤0.5m/s,h≥1.5m。
The open channels in the northern part of our country often face the problem of ice damage in winter operation. In order to eliminate the ice damage caused by the operation of the open channel in winter, it is common practice in engineering practice to control the water flow conditions (water temperature, flow rate, water depth, etc.) to form the ice water two phase flow water delivery method or the ice cap water delivery method. Water is transported by means of ice-water two-phase flow, which requires high overcurrent conditions for the open channel (flow rate ≥1.2m / s, depth ≥1.5m, flow sparseness η <60%, curvature radius R≥8B and rotation angle Etc.) and often have certain risks in operation. However, when the ice cap is used for water conveyance, many difficulties in the operation of the open channel in winter are eliminated because of the safe and reliable avoidance of ice damage and many Water projects used. Local meteorological conditions determine the operational modes of open channels that can be used in winter. The condition of water flow control of open channel with icing cap running is F_ (rc) ≤0.09, V_c≤0.5m / s, h≥1.5m.