In this investigation, a flow rate estimation guided wave based scheme in pipes is proposed. The effect of the fluid over the propagation of longitudinal waves has been experimentally studied by using several laminar flows of water transported by a steel pipe. Results have shown a decrease of the guided wave pattern repeatability and the signal energy as the flow rate increase as a result of the energy leakage from the pipe to the fluid. A Matlab ® script is used to excite the PZT actuator via picoscope 2208 of Picotech ® , the captured signal is acquired also by the picoscope and the data is processed in Matlab. The test bench utilized is composed by a 1” sch 40 A-106 pipe, a needle valve and a centrifugal pump provides the flow energy. A couple of PZTs are used in a picth-catch configuration to produce and capture the longitudinal waves along the cross section of the pipe