dorsal/arxiv
View SchemaNumerical and Experimental Investigation of Circulation in Short Cylinders
| Authors | Akira Kageyama, Hantao Ji, Jeremy Goodman, Fei Chen, Ethan Shoshan |
|---|---|
| Categories | |
| ArXiv ID | physics/0405123 |
| URL | https://arxiv.org/abs/physics/0405123 |
| DOI | 10.1143/JPSJ.73.2424 |
| Journal | J.Phys.Soc.Jap. 73 (2004) 2424-2437 |
Abstract
In preparation for an experimental study of magnetorotational instability (MRI) in liquid metal, we explore Couette flows having height comparable to the gap between cylinders, centrifugally stable rotation, and high Reynolds number. Experiments in water are compared with numerical simulations. Simulations show that endcaps corotating with the outer cylinder drive a strong poloidal circulation that redistributes angular momentum. Predicted azimuthal flow profiles agree well with experimental measurements. Spin-down times scale with Reynolds number as expected for laminar Ekman circulation; extrapolation from two-dimensional simulations at $Re\le 3200$ agrees remarkably well with experiment at $Re\sim 10^6$. This suggests that turbulence does not dominate the effective viscosity. Further detailed numerical studies reveal a strong radially inward flow near both endcaps. After turning vertically along the inner cylinder, these flows converge at the midplane and depart the boundary in a radial jet. To minimize this circulation in the MRI experiment, endcaps consisting of multiple, differentially rotating rings are proposed. Simulations predict that an adequate approximation to the ideal Couette profile can be obtained with a few rings.
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"abstract": "In preparation for an experimental study of magnetorotational instability\n(MRI) in liquid metal, we explore Couette flows having height comparable to the\ngap between cylinders, centrifugally stable rotation, and high Reynolds number.\nExperiments in water are compared with numerical simulations. Simulations show\nthat endcaps corotating with the outer cylinder drive a strong poloidal\ncirculation that redistributes angular momentum. Predicted azimuthal flow\nprofiles agree well with experimental measurements. Spin-down times scale with\nReynolds number as expected for laminar Ekman circulation; extrapolation from\ntwo-dimensional simulations at $Re\\le 3200$ agrees remarkably well with\nexperiment at $Re\\sim 10^6$. This suggests that turbulence does not dominate\nthe effective viscosity. Further detailed numerical studies reveal a strong\nradially inward flow near both endcaps. After turning vertically along the\ninner cylinder, these flows converge at the midplane and depart the boundary in\na radial jet. To minimize this circulation in the MRI experiment, endcaps\nconsisting of multiple, differentially rotating rings are proposed. Simulations\npredict that an adequate approximation to the ideal Couette profile can be\nobtained with a few rings.",
"arxiv_id": "physics/0405123",
"authors": [
"Akira Kageyama",
"Hantao Ji",
"Jeremy Goodman",
"Fei Chen",
"Ethan Shoshan"
],
"categories": [
"physics.flu-dyn",
"astro-ph",
"physics.comp-ph"
],
"doi": "10.1143/JPSJ.73.2424",
"journal_ref": "J.Phys.Soc.Jap. 73 (2004) 2424-2437",
"title": "Numerical and Experimental Investigation of Circulation in Short Cylinders",
"url": "https://arxiv.org/abs/physics/0405123"
},
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