A flow measurement device includes a first sensor device that responds to stimulus from fluid medium flowing through a measurement section by registering a measure representing a physical characteristic, a processor, and a data storage including a look-up table containing a first collection of values representing a first value of flow of a first fluid or a first value of flow of a second fluid, and a second look-up table containing a second collection of the values representing a second value of the flow of the first fluid or a second value of the flow of the second fluid, the processor receiving the measures registered during a measurement time interval and estimating a flow pattern of the fluid medium during the measurement interval where the flow pattern describes how the first and second fluids are distributed in the measurement section over the measurement time interval.
