The swimming patterns and energy-saving mechanism revealed from three fish in a school

Fish in nature are believed to favor their swimming performance by swimming in a school. We investigated numerically the thrust and power consumption of a school of fish with an arrangement of one upstream and two downstream. The upstream fish enhances the thrust with an area of high pressure at the heads of the two downstream fish, but the region of low pressure created between the two downstream fish generates a strong suction and is detrimental to the swimming of the upstream fish. The thrust forces increase but the power consumptions of the downstream fish decrease. The downstream fish in this arrangement can avoid the jet flow of the upstream fish and benefit from the counter flow at the verge of the upstream wake. The power-saving mechanism is obvious and sensitive to the longitudinal distance when the fish are in a school within a small lateral distance. The maximum average power consumption in a school is 20% less than not in a school. The mechanisms of thrust enhancement and energy saving in a school of fish interact in manifold ways, and provide insight into the bio-inspired design for arrays of underwater vehicles. (C) 2016 Elsevier Ltd. All rights reserved.