Patent Document ID: 7720629
Application ID: 10549199
Patent Flag: 1

Claim One:
1. A method for measuring flow layer velocities using correlation velocity measuring sonar, the method comprising steps of: (1) selecting a transmit code for acoustic pulses; (2) according to the transmit code, transmitting the acoustic pulses into a fluid medium, and receiving echo signals backscattered by flow layers in the fluid medium; (3) demodulating and filtering the echo signals of the flow layers, and calculating a data temporal and spatial correlation function matrix of the flow layers according to the demodulated and filtered echo signals; (4) extracting a data matrix for fitting from the data temporal and spatial correlation function matrix derived from the step (3), the data matrix for fitting being a localized data temporal and spatial correlation function matrix of the flow layers derived by the steps of: (a) performing an absolute value operation on the data temporal and spatial correlation function matrix of the flow layers to obtain a data temporal and spatial correlation function absolute value matrix of the flow layers, elements of said data temporal and spatial correlation function absolute value matrix having a maximum value of E Max ; and (b) setting a threshold value X of 0< X ≦1, deriving the localized temporal and spatial correlation function absolute matrix by setting those elements in the absolute value matrix with a numerical value less than X E Max to zero, and by retaining those elements in the absolute value matrix with a numerical value equal to or larger than X E Max ; (5) setting a search range of an unknown parameter ensemble ={ V x , V y , σ vx , σ vy , γ}, wherein V x and V y are average values of relative velocities of the flow layers in x, y directions, respectively, σ vx and σ vy are standard deviations of the velocities in x, y directions, respectively, and γ is a width factor; (6) using a computer to fit the data matrix for fitting derived from the step (4) into a theoretical fluid medium sonar array function in the search range of the unknown parameter ensemble to obtain fitting results, the theoretical fluid medium sonar array function being: φ ⁡ ( τ , ϑ , d ) = C ⁢ { exp ⁡ ( γβ θ ) - ζ 2 2 ⁡ [ θ e 2 2 ⁢ π ⁢ 1 ⁢ F ⁢ ⁢ 1 ⁢ ( 2 ; 1 ; β θ ) - cos ⁢ ⁢ 2 ⁢ ( α 3 - α 2 ) ⁢ B 2 2 ⁢ θ e 4 8 ⁢ π 2 ⁢ F 1 1 ⁡ ( 3 ; 3 ; β θ ) ] } wherein, C is a constant, τ is a time delay parameter, d is a distance between receive elements of the sonar array, 1 F 1 (. ) is a Kummer function, β 0 = - β 2 2 ⁢ θ e / 4 ⁢ ⁢ π , β 2 = ω 0 c ⁢ ( ( τ ⁢ ⁢ V _ x + d x ) 2 + ( τ ⁢ ⁢ V _ y + d y ) 2 ) 1 / 2 , ⁢ ζ 2 = ω 0 ⁢ τ c ⁢ ( σ vx 2 + σ wy 2 ) 1 / 2 , α 2 = tg - 1 ⁢ τ ⁢ ⁢ V _ y + d y τ ⁢ ⁢ V _ x + d x , α 3 = tg - 1 ⁢ σ vy σ vx , ⁢ θ e 2 = 1 2 ⁢ θ b 2 ⁢ θ c 2 θ b 2 + θ c 2 , ω 0 is a central frequency of the transmitted acoustic pulses, c is the velocity of sound, dx and dy are components of d in x direction and y direction, respectively, and θ b and θ c are beam widths of the transmitted acoustic pulses and the received echo signal, respectively; and (7) Obtaining absolute velocities of each of the flow layers by cooperating the velocity of a vessel relative to the seabed with the average values of the relative velocities { V x , V y } derived according to the fitting results obtained in the step (6).