A few remarks concerning the flow of fluid under a sluice gate
"The two-dimensional, irrotatational flow of incompressible fluid under a sluice gate in a gravitational field has been treated by de Boor (Ref. 1) using the integral equation method of Birkhoff and Zarantonello (Ref. 2). However, de Boor was not able to satisfactorily satisfy the constant pressure condition on the free streamline in the neighborhood of the point at infinity. He established (using certain hypotheses) that this difficulty occurred because the singularity in the velocity potential at this point did not have a continuous derivative. The author has determined the apparent form of this singularity. By removing part of it, he has obtained solutions which appear to be substantially more accurate than those obtained by deBoor."--Abstract.