  Understanding force generation in non-equilibrium systems is a significant
challenge in statistical physics. We uncover a surprising fluctuation-induced
force between two plates immersed in homogeneous isotropic turbulence using
Direct Numerical Simulation. The force is a non-monotonic function of plate
separation. The mechanism of force generation reveals an intriguing analogy
with fluctuation-induced forces: energy in the fluid is localised in regions of
high vorticity, or "worms", which have a characteristic length scale. The
magnitude of the force depends on the packing of worms inside the plates, with
the maximal force attained when the plate separation is comparable to the
characteristic worm length. A key implication of our study is that the length
scale-dependent partition of energy in an active or non-equilibrium system
determines force generation.
