Granted Patent B2

US 7,516,024 · App. 11/934,282 · Granted Apr 7, 2009

Abstract

Claims (43)

1. An apparatus for measuring a parameter of a flow passing through a pipe, the flow including a plurality of coherent structures, each coherent structure having one of a plurality of length scales wherein a group of coherent structures includes coherent structures having similar length scales, and wherein a corresponding average convection velocity of a group of coherent structures scales with the average length scale of the group, the apparatus comprising:

a spatial array of sensors disposed at different axial locations along the pipe, each of the sensors providing a signal indicative of unsteady pressure created by the coherent structures convecting with the flow; and

a signal processor responsive to the signal for:

determining the corresponding convection velocity of each group of coherent structures, and

comparing the convection velocities of the groups of coherent structures to determine a level of stratification of the flow.

2. The apparatus of claim 1 , wherein, in comparing the convection velocities, the signal processor is configured to:

construct a plot of the convection velocities as a function of the length scales, and

determine a slope of a best-fit line through the plot, the slope of the line indicating the level of stratification of the flow.

3. The apparatus of claim 2 , wherein the plot is normalized by a nominal velocity of the flow and a diameter of the pipe.

4. The apparatus of claim 2 , wherein the slope is used to calibrate the signal processor to determine the volumetric flow rate of the flow.

5. The apparatus of claim 4 , wherein the signal processor is configured to:

construct from the signals at least a portion of a k-ω plot; and

determine a frequency range over which the signal processor analyzes a convective ridge in the k-ω plot for determining the volumetric flow rate.

6. The apparatus of claim 2 , wherein, in constructing the plot of convection velocities, the signal processor is configured to:

construct from the signals at least a portion of a k-ω plot;

identify a convective ridge in the k-ω plot over a first frequency range;

determine a first slope of the convective ridge, the first slope being indicative of a nominal velocity of the flow;

identify a plurality of portions of the convective ridge over a plurality of second frequency ranges, each second frequency range being smaller than the first frequency range and having a respective midpoint;

determine a second slope for each of the portions of the convective ridge, each second slope being indicative of a nominal convection velocity of coherent structures having a range of length scales corresponding to an associated second frequency range;

normalize the nominal convection velocities of coherent structures using the nominal velocity of the flow to provide normalized convection velocities; and

plot each normalized convection velocity as a function of the respective midpoint non-dimensionalized by the nominal velocity of the flow and the diameter of the pipe to provide the plot.

7. The apparatus of claim 6 , wherein the first frequency range is adjusted based on the slope.

8. The apparatus of claim 6 , wherein a non-dimensional length scale that is least sensitive to stratification is used to determine the mid-point of the first frequency range, the non-dimensional length scale that is least sensitive to stratification being determined by comparing a plurality of dispersion plots for different levels of stratification and identifying the pivot point of the dispersion plots from one dispersion plot to another.

9. A method for measuring a parameter of a flow passing through a pipe using a spatial array of sensors disposed at different axial locations along the pipe, the flow including a plurality of coherent structures, each coherent structure having one of a plurality of length scales, wherein a group of coherent structures includes coherent structures having similar length scales, and wherein a corresponding average convection velocity of a group of coherent structures scales with the average length scale of the group, each of the sensors providing a signal indicative of unsteady pressure created by the coherent structures convecting with the flow, the method comprising:

determining, from the signals, the corresponding convection velocity of each group of coherent structures, and

comparing the convection velocities of the groups of coherent structures to determine a level of stratification of the flow.

10. The method of claim 9 , wherein comparing the convection velocities includes:

constructing a plot of the convection velocities as a function of the length scales, and

determining a slope of a best-fit line through the plot, the slope of the line indicating the level of stratification of the flow.

11. The method of claim 10 , wherein the plot is normalized by a nominal velocity of the flow and a diameter of the pipe.

12. The method of claim 10 , further comprising;

constructing from the signals at least a portion of a k-ω plot; and

using the slope, determining a frequency range over which the signal processor analyzes a convective ridge in the k-ω plot for determining the volumetric flow rate.

13. The method of claim 10 , wherein constructing the plot of convection velocities comprises:

constructing from the signals at least a portion of a k-ω plot;

identifying a convective ridge in the k-ω plot over a first frequency range;

determining a first slope of the convective ridge, the first slope being indicative of a nominal velocity of the flow;

identifying a plurality of portions of the convective ridge over a plurality of second frequency ranges, each second frequency range being smaller than the first frequency range and having a respective midpoint;

determining a second slope for each of the portions of the convective ridge, each second slope being indicative of a nominal convection velocity of coherent structures having a range of length scales corresponding to an associated second frequency range;

normalizing the nominal convection velocities of coherent structures using the nominal velocity of the flow to provide normalized convection velocities; and

plotting each normalized convection velocity as a function of the respective midpoint non-dimensionalized by the nominal velocity of the flow and the diameter of the pipe to provide the plot.

14. The method of claim 13 , wherein the first frequency range is adjusted based on the slope.

15. The method of claim 14 , wherein a non-dimensional length scale that is least sensitive to stratification is used to determine the mid-point of the first frequency range, the non-dimensional length scale that is least sensitive to stratification being determined by comparing a plurality of dispersion plots for different levels of stratification and identifying the pivot point of the dispersion plots from one dispersion plot to another.

Assignments (8)