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管道內不滿流时,水流的基本水力因素是流量、流速,和管內水深等三个变值。这三个变值又決定于管道縱坡、粗糙度和横断面等物理因素。一般来说,难于从这些物理因素直接求出变值,而必須先定出水流断面湿周和水力半径等輔助值。在管道内不滿流时,水力計算包括很多变值,这些变值不能用一个公式或共线图来求出而必须进行较繁复的計算。本計算尺能克服这些困难,能夠根据一些物理因素直接讀出流量,流速,和管内水深等值。
When the pipeline is under full flow, the basic hydraulic factors of the flow are the three variables of flow rate, flow velocity, and water depth in the pipe. These three variables are also determined by physical factors such as longitudinal slope, roughness and cross-section of the pipeline. In general, it is difficult to determine the change value directly from these physical factors, and it is necessary to first determine the auxiliary values such as the wet period and the hydraulic radius of the flow section. When the pipeline is under full flow, the hydraulic calculation includes many variable values. These variable values cannot be calculated by a formula or collinear map but must be calculated more complicatedly. The slide rule can overcome these difficulties and can directly read the flow rate, flow rate, and water depth in the pipe based on some physical factors.