# US 5,341,677 A · Method of aerodynamic stall-turbulence indication > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,341,677 A - Document ID: US5341677A - Status: Granted - Kind: A - Application number: 07/979,794 - Filed: 1992-11-20 - Granted: 1994-08-30 - Earliest claimed: 1992-11-20 - Inventors: John M. Maris - Web page: https://patentgrep.com/patent/US5341677A ## CPC - G01M 9/065: {dealing with flow} - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract Method, apparatus, and sensor mast for airfoil aerodynamic performance monitoring are based on pressure measurement. Pressure transducers mounted within the sensor mast measure real-time pressure, to produce an output signal. The signal is separated into steady state and overlaid ripple components. The steady state component corresponds to the mean dynamic pressure of the airflow, while overlaid ripple component corresponds to the superimposed turbulent flow component. The overlaid ripple component is transformed to an amplitude equivalent. A dimensionless ratio of the two components forms a pressure turbulence intensity factor, which may be used consistently to predict and warn of imminent stall conditions. Pressure measurement was found to be an improvement over airspeed measurement. Pressure sensors proved more robust and less fragile than airspeed sensors. ## Claims ### Claim 1 In a method investigating airflow over the external surface of an airfoil comprising measuring at least one parameter of said airflow in real-time to produce a signal, identifying and measuring the steady state component of said signal, identifying and measuring the overlaid ripple component of said signal, expressing said components of said signal as a dimensionless ratio, to produce a turbulence intensity factor, the improvement comprising measuring the pressure of said airflow to produce a pressure turbulence intensity factor. ### Claim 2 (depends on 1) A method of claim 1, additionally comprising transforming said real-time overlaid ripple component of said signal into an amplitude equivalent. ### Claim 3 (depends on 2) A method of claim 2, additionally comprising presenting said pressure turbulence intensity factor by conventional means. ### Claim 4 (depends on 1) A method of claim 1 comprising measuring the real-time pressure of said airflow using pressure transducer means to produce an analog output signal, transforming said output signal from analog signal to digital signal, separating said digital signal into steady state and overlaid ripple components, transforming said overlaid ripple component into an amplitude equivalent expressing a dimensionless ratio of said amplitude equivalent of said overlaid ripple component and said steady state component to produce a pressure turbulence intensity factor. ### Claim 5 (depends on 4) A method of claim 4, additionally comprising amplifying said analog output signal, and presenting said pressure turbulence intensity factor by conventional means. ### Claim 6 (depends on 1) A method of claim 1 comprising measuring the real-time pressure of said airflow using pressure transducer means to produce an analog output signal, separating said analog output signal into steady state and overlaid ripple components, transforming said overlaid ripple component into an amplitude equivalent expressing a dimensionless ratio of said amplitude equivalent of said overlaid ripple component and said steady state component to produce a pressure turbulence intensity factor. ### Claim 7 (depends on 6) A method of claim 6, additionally comprising amplifying said analog output signal, and presenting said pressure turbulence intensity factor by conventional means. ### Claim 8 Apparatus for investigating airflow over the external surface of an airfoil comprising: means to measure pressure in real-time at a predetermined location spaced from said surface means to produce at least one output signal corresponding to said pressure, means to separate said signal into steady state and overlaid ripple components means to derive a dimensionless ratio of said overlaid ripple component and said steady state component to produce a pressure turbulence intensity factor. ### Claim 9 (depends on 8) An apparatus of claim 8, additionally comprising means to transform said real-time overlaid ripple component of said signal into an amplitude equivalent. ### Claim 10 (depends on 9) An apparatus of claim 9, additionally comprising conventional means to display said ratio. ### Claim 11 (depends on 8) Apparatus of claim 8 comprising means to measure pressure in real-time at a predetermined location spaced from said surface means to produce at least one output signal corresponding to said pressure, means to convert said output signal from analog to digital, means to separate said digital signal into steady state and overlaid ripple components means to transform said overlaid ripple component into an amplitude equivalent, means to derive a dimensionless ratio of amplitude equivalent of said overlaid ripple component and said steady state component to produce a pressure turbulence intensity factor. ### Claim 12 (depends on 11) An apparatus of claim 11, additionally comprising means to amplify said output signal and conventional means to display said ratio. ### Claim 13 (depends on 8) Apparatus of claim 8 comprising means to measure pressure in real-time at a predetermined location spaced from said surface means to produce at least one output signal corresponding to said pressure, means to separate said signal electrically into steady state and overlaid ripple components means to transform said overlaid ripple component into an amplitude equivalent, means to derive a dimensionless ratio of amplitude equivalent of said overlaid ripple component and said steady state component to produce a pressure turbulence intensity factor. ### Claim 14 (depends on 13) An apparatus of claim 13, additionally comprising means to amplify said output signal and conventional means to present said ratio.