For a nonrotating force-free sphere moving with speed in a stationary tube, use its moving frame: the tube wall has velocity . In the parabolic lubrication gap , , moving-boundary lubrication flux gives . The wall-shear and pressure-drop balance in a tube rules out an net pressure jump. Applying this common pressure recovery to each angular strip gives . The next balance yields the displayed positive localized pressure drop. Meanwhile the integrated leading shear stress on the sphere vanishes in each strip; this is consistent with negligible leading torque, and does not mean the local shear or pressure force vanishes.
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