HP 48gII hp 48gII_user's manual_English_E_HDPMSG48E67_V2.pdf - Page 665

where Cu is a constant that depends on the system of units used [Cu = 1.0 for units of the International System (S.I.), and Cu = 1.486 for units of the English System (E.S.)], n is the Manning's resistance coefficient, which depends on the type of channel lining and other factors, y0 is the flow depth, and S0 is the channel bed slope given as a dimensionless fraction. Note: Values of the Manning's coefficient, n, are available in tables as dimensionless numbers, typically between 0.001 to 0.5. The value of Cu is also used without dimensions. However, care should be taken to ensure that the value of y0 has the proper units, i.e., m in S.I. and ft in E.S. The result for q is returned in the proper units of the corresponding system in use, i.e., m2/s in S.I. and ft2/s in E.S. Manning's equation is, therefore, not dimensionally consistent. Suppose that we want to create a function q(Cu, n, y0, S0) to calculate the unit discharge q for this case. Use the expression 'q(Cu,n,y0,S0)=Cu/n*y0^(5./3.)*√S0', as the argument of function DEFINE. Notice that the exponent 5./3., in the equation, represents a ratio of real numbers due to the decimal points. Press J, if needed, to recover the variable list. At this point there will be a variable called @@@q@@@ in your soft menu key labels. To see the contents of q, use ,@@@q@@@. The program generated by defining the function q(Cu,n,y0,S0)is shown as: « → Cu n y0 S0 'Cu/n*y0^(5./3.)*√S0' ». This is to be interpreted as "enter Cu, n, y0, S0, in that order, then calculate the expression between quotes." For example, to calculate q for Cu = 1.0, n = 0.012, y0 = 2 m, and S0 = 0.0001, use, in RPN mode: 1 ` 0.012 ` 2 ` 0.0001 ` @@@q@@@ The result is 2.6456684 (or, q = 2.6456684 m2/s). Page 21-16