Timeline for What is the proof that shear stress in a static fluid element reduces to zero?
Current License: CC BY-SA 3.0
7 events
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| Jul 30, 2016 at 8:19 | comment | added | CoolHandLouis | If there was a shear stress, the fluid would flow, would it not? And if it did not flow, then we would no longer call it a fluid, right? It seems definitional to me. Unless I'm missing something, it seems similar to asking for a proof why solids can sustain non-zero shear stresses. On the other hand, are you asking for an atomic model of a substance which guarantees fluid-like qualities, which therefore guarantee any shear stress would be eliminated through fluid-like accomodation (ie, molecules moving until shear forces are eliminated through equilibrium)? | |
| Jul 6, 2016 at 12:11 | comment | added | Lelouch | The fact that the fluid element is not deforming will conclude whether the shear force is zero or not. If the shear stress is T then T = M du/dy. For a static fluid, du/dy is zero and hence T is zero. | |
| Jul 6, 2016 at 12:08 | comment | added | Haridev V | The statement that shear stress in a static fluid element is always zero arises only from observation, and is there no fundamental proof to it? | |
| Jul 6, 2016 at 12:03 | comment | added | Diracology | @SergeiPatiakin I think your comment above is the correct answer! | |
| Jul 6, 2016 at 11:54 | comment | added | Sergei Patiakin | By empirical observation, some materials can support shear stress in their static state, whereas others cannot. We have chosen the term 'fluid' to describe those materials which cannot. | |
| Jul 6, 2016 at 11:49 | comment | added | Haridev V | When we consider force balance on a static fluid element which is cut along some arbitrary plane, we start by saying that the fluid is static and hence there is no shear stress along that plane. And from there we define the pressure on the face of the plane as acting normal to the plane, and go on to derive the hydrostatic condition of pressures at a point. My question is, where does the assumption that the shear stress is zero come from? Is it purely due to observation that a fluid flows continuously under any applied shear, or is there a fundamental basis? | |
| Jul 6, 2016 at 11:01 | history | answered | Sergei Patiakin | CC BY-SA 3.0 |