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Robin
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The pressure decrease in moving fluid is relative to the fluid at rest. You are referring to the momentum conservation equation for an inviscid fluids, aka Bernoulli equation: $$ \tfrac12 (v_2^2-v_1^2) + \frac 1 \rho (p_2-p_1)=0 $$ (here without the gravitation term). This is valid along a streamline only! It is not a general principle that the pressure decreases in fast moving fluids.

In short, using Bernoulli's equation on your spinning glass does not tell you anything on the pressure in the water. Instead, the pressure distribution inside your water can be calculated using e.g. the idea of potential energy.

Assuming the water spins so fast that a vortex is generated, and assuming that the air inside the water vortex spins equally fast, all you get is a pressure increase at the water-air boundary as @Peter.A.Schneider pointed out in his comment.

Since it is one of the fundamental assumption of continuum mechanics that the stress vector is continuous, the pressure at the water-air boundary is equal inside the water and the air. So however fast you spin your glass, the pressure on the water surface will not drop, but may increase.

Straight answer: No, you cannot make water boil simply by spinning it in a glass. It's impossible. The pressure inside the water will not decrease, but increase.

Robin
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