This article presents a numerical investigation of 2D turbulent flow within a double external gear pump. The configuration of the inlet and outlet ports is determined such that the double gear pump acts like the combination of two parallel pumps. The complex geometry of the double gear pump, existence of narrow gaps between rotating and stationary walls, and rapidly deforming flow domain make the numerical solution more complicated. In order to solve the mass, momentum, and energy conservation laws along with the k-ε turbulence model, a second-order finite volume method has been used over a dynamically varying unstructured mesh. The numerical results including pressure contours, velocity vectors, flow patterns inside the suction chamber, leakage paths, and time variation of volumetric flow rate are presented in detail. The flow rate characteristic curves with linear behavior are demonstrated at rotational speeds and outlet pressures in the range of 1500–4000 rpm and 2–80 bar, respectively. The effect of reducing the gear-casing gap-size on the augmentation of the net flow rate has been investigated. It is concluded that the minimum oil pressure within the gear pump occurs at the two places between contacting gears near the inlet ports. The contours of vapor volume fraction are also illustrated.