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# Fluid shear-force field measurement?

## Fluid shear-force field measurement?

(OP)
Is anyone aware of any way to measure the surface shear-force field (2D distribution of shear forces) created by an impinging fluid jet?

As an analogy, think of shooting a garden hose at a wall, creating the circular flow pattern. I want to know (to some decent spatial resolution) the shear stresses/forces across the wetted area as the jet impinges and then flows off in all directions on the surface of the wall.

I'm thinking a sensor like this must exist in the world of aerodynamics/wind-tunnel testing, etc.

I'm aware of force sensing films (like Tekscan and others), but to my knowledge they only measure normal (compressive) forces. I sort of want the shear version of that product, though a shear/normal force combo would be ideal.

I'm also open to other crazy ways to do this - like using photochromic paints and the like...

Double extra credit if you can think of a way to do the same thing, though over some type of 3D structure - think of spraying the garden hose on a rock.

### RE: Fluid shear-force field measurement?

You could measure local static pressure, e.g. with taps flush to surface, and then infer velocity from dP/dx.

### RE: Fluid shear-force field measurement?

Measure the reaction force on the target object and then use geometry to resolve this into the normal and shear forces.

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