For large air bubbles rising steadily through still water, the upward reaction force on the spherical cap is calculated. When added to the buoyancy force on the roughly flat base of the bubble, the friction force at terminal velocity must be larger than it would be in the absence of the reaction force. Experimental data are used to estimate that the increase in the drag coefficient is expected to be about 4%.

background

/pdf/reaction-force-on-bubbles-4ul30mjqb6.pdf

Reaction Forces of Fluid Flows on Solid Boundaries

Reaction Force on Bubbles

Steady flow past a circular arc wing produces a
vertical lift force, which has been calculated before, but it also causes two
horizontal reaction forces, equal and opposite, due to Newton’s third law: the
accelerated and decelerated flows act back on the top surfaces of the wing. Reaction
forces are computed here and compared with the lift force. The magnitude of the
two perpendicular forces are equal when the ratio of the maximum thickness of
the wing is about 1/5 the length of the wing’s flat bottom surface. An example
of an asymmetric wing is discussed and the net reaction force is calculated,
which is always directed horizontally away from the top surface of the wing
that has the greater mean slope. Based on these results,it is
predicted that a surface ship should go more easily through the water if the
bow were blunt and the stern pointed, just the opposite configuration of what
is commonly found traversing lakes and oceans. Surface gravity waves are argued
not to change this conclusion in general.

/pdf/fluid-reaction-force-on-solids-1scq4fqc3i.pdf

Fluid Reaction Force on Solids

Assuming
thermal convection takes place continuously inside the North Pacific High, an
application of physics to the rising sea-warmed air plumes increases
understanding of the relatively high air pressure at the sea surface and at the
bases of the plumes. Since the ocean is warmer than the air under the NPH, heat
is transferred upward decreasing the air density, which should then accelerate upward
when no other forces are around to stop it. By Newton’s 3rd law the
upward accelerating air will cause an equal but opposite (downward) reaction
resulting in high pressure in the air under the rising column. That is the
central proposal offered, which is consistent with available observations. New
data that confirm the upward acceleration of the heated air are especially
needed. Perhaps dye or neutrally buoyant particles could be released from a
ship or buoy to make the upward air motion visible.

/pdf/thermal-convection-mechanics-3rx9fohbe1.pdf

Reaction Forces of Fluid Flows on Solid Boundaries

Citations

Reaction Force on Bubbles

Fluid Reaction Force on Solids

Thermal Convection Mechanics

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