抄録
In recent years, improvement of fuel consumption efficiency of transport machines have been desired including the vehicles, trucks and construction machines in relation to recent environmental energy issue. Especially, in the construction machines, the power supplied by diesel engine is transferred through the hydraulic system and the working oil with high-pressure flows in hydraulic piping. The energy loss of construction machines caused on hydraulic piping is estimated about 5% or more of total power source, there is some room here for fuel consumption improvement. This paper shows the research on drag reduction in hydraulic piping focusing the Toms effect.