CONSIDERATION OF TOTAL ENERGY-LOSS IN THEORY OF FLOW TO WELLS

A coupled numerical solution was developed for unsteady flow in single or multiple confined or semiconfined aquifers and in the well penetrating the system. Analysis of hypothetical problems indicates that, because of friction losses and non-uniform flow in the well bore, a significant region of non-radial flow in the aquifer(s) results whenever aquifer hydraulic conductivity is greater than about 0.015 m/min. and pumping rate is greater than about 1.2 m2/min. Because of this non-radial flow, use of standard aquifer testing equations can lead to significant errors in computed aquifer transmissivity whenever aquifer hydraulic conductivity is greater than about 0.03 m/min. Because of unsteady flow in the well bore, flow may be highly non-radial for the first few seconds of pumping irrespective of hydraulic conductivity or pumping rate. Percentage of open area in the screened or perforated section of well bore, Fanning friction factor, and contraction coefficients characterizing flow through the perforations or slots are parameters that could cause large head losses in the well in some cases. Expressions for parameters B and C in the total drawdown equation sw = BQ + CQ2 (where sw is drawdown in the well and Q is pumping rate) were developed dimensionally from expressions used in this study. The development shows that both B and C could theoretically be dependent on Q. © 1979.