41. For an irrotational flow, the flow velocity can be described as the gradient of a velocity potential. 42. In fluid dynamics, a flow is considered incompressible if the divergence of the flow velocity is zero. 43. By reducing flow velocity to limit solids being transported along with fast flowing liquid, separation can occur. 44. If the trailing edge has a non-zero angle, the flow velocity there must be zero. 45. By Bernoulli's principle, this increases the flow velocity of the water, thus reducing pressure. 46. Here " ? " is the mean flow velocity below steady in this reference frame ). 47. The steps of the spillway greatly reduce the kinetic energy of the flow and therefore reduce flow velocity . 48. Incompressible flow implies that the density remains constant within a parcel of fluid that moves with the flow velocity . 49. With large areas of impervious surfaces, airports must employ methods to collect runoff and reduce its flow velocity . 50. The Boussinesq approximation for water waves takes into account the vertical structure of the horizontal and vertical flow velocity .
