With reference to a relative coordinate system, the rate of change of the surface integral of thisquantity is equal to the number of pressure-volume solenoids embraced by the rate of change of theenclosed area projected on the equatorial plane. That is a theorem is named after Bjerknes, and useof the no-slip boundary condition results in this quantity being non-zero. According to one ofHelmholtz's theorems, if this property for a fluid particle is (*) zero initially, it will remain zeroforever. Using the differential form of Ampere's law and the Biot-Savart law, one can express the flowvelocity in terms of this property. A theorem named for Kelvin states that the surface integral of thisquantity is constant, which has an important implication for aircraft wings. This quantity is defined as thecurl of the flow velocity. For 10 points, name this property whose surface integral is circulation, themeasure of rotation of individual elements 
With reference to a relative coordinate system, the rate of change of the surface integral of thisquantity is equal to the number of pressure-volume solenoids embraced by the rate of change of theenclosed area projected on the equatorial plane. That is a theorem is named after Bjerknes, and useof the no-slip boundary condition results in this quantity being non-zero. According to one ofHelmholtz's theorems, if this property for a fluid particle is (*) zero initially, it will remain zeroforever. Using the differential form of Ampere's law and the Biot-Savart law, one can express the flowvelocity in terms of this property. A theorem named for Kelvin states that the surface integral of thisquantity is constant, which has an important implication for aircraft wings. This quantity is defined as thecurl of the flow velocity. For 10 points, name this property whose surface integral is circulation, themeasure of rotation of individual elements in a fluid.
With reference to a relative coordinate system, the rate of change of the surface integral of thisquantity is equal to the number of pressure-volume solenoids embraced by the rate of change of theenclosed area projected on the equatorial plane.
vorticity