A method of detect the onset of turbulence in connection with a body movinghrough a fluid medium. First, the body is supplied with sensors each for generating a signal suitable for measuring amplitude of pressure fluctuations of the medium proximate a region of said sidewall of the body in at least a region of the body in which turbulence is expected to occur. During a reference stage during which the body moves through the fluid medium when it is known that turbulence is occurring around at least a portion of said body , the sensors each generate reference temporal pressure data representing fluctuations in pressure of the fluid medium around said body. In response to reference temporal pressure data generated by sensors in a turbulence zone at which turbulence is occurring and sensors in a transition zone between the turbulence zone and a laminar flow zone, a method-of-delay phase portrait is generated for each of a progression of selected delay intervals. These operations are repeated during an operational stage, and phase portraits generated during the operational stage are compared to phase portraits in response to the reference temporal pressure data from the transitional zone and the turbulence zone, for corresponding ones of said selected delay intervals,, and a determination of the onset of turbulence is made in response to such comparison.