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Abstract

A vortex flow measuring device as well as a method for determining by means of a vortex, flow measuring a device, which has a bluff body protruding into the flowing medium and a vortex sensor, the mass flow ratio (x) of an at least at times two- or multiphase medium flowing in a measuring tube and having a gaseous first phase flowing with a first mass flow rate {dot over (m)}_G and a liquid second phase flowing with a second mass flow rate {dot over (m)}_L. The gaseous phase has a first density (ρ_G), which differs from a second density (ρ_L) of the liquid phase, comprising: producing Kármán vortices in the flowing medium at least in the region of the vortex sensor by means of the bluff body, the vortices are shed from the bluff body with a vortex shedding frequency (f_v) dependent on an instantaneous flow velocity of the flowing medium; registering by means of the vortex sensor periodic pressure fluctuations caused by the Kármán vortex in the flowing medium for producing a sensor signal corresponding to the pressure fluctuations; selecting from the sensor signal a wanted signal component, which has a frequency band, especially a narrow frequency band, containing the vortex shedding frequency, especially with a relative bandwidth less than 50% of the instantaneous vortex shedding frequency, wherein preferably the instantaneous vortex shedding frequency represents the center frequency of the frequency bandwidth; and applying the wanted signal component (M) for determining a mass flow ratio (x) of the flowing medium, wherein the mass flow ratio (x) is defined as a ratio of the first mass flow {dot over (m)}_G to a total mass flow, with which the medium flows, especially according to a formula:

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