Abstract
This study is the first in a series that investigates the effects of turbulence in the boundary layer of a tornado vortex. In this part, axisymmetric simulations with constant viscosity are used to explore the relationships between vortex structure, intensity, and unsteadiness as functions of diffusion (measured by a Reynolds number Rer) and rotation (measured by a swirl ratio Sr). A deep upper-level damping zone is used to prevent upper-level disturbances from affecting the low-level vortex. The damping zone is most effective when it overlaps with the specified convective forcing, causing a reduction to the effective convective velocity scale We. With this damping in place, the tornado-vortex boundary layer shows no sign of unsteadiness for a wide range of parameters, suggesting that turbulence in the tornado boundary layer is inherently a three-dimensional phenomenon. For high Rer, the most intense vortices have maximum mean tangential winds well in excess of We, and maximum mean vertical velocity exceeds 3 times We. In parameter space, the most intense vortices fall along a line that follows Sr~Rer -1/3, in agreement with previous analytical predictions by Fiedler and Rotunno. These results are used to inform the design of three-dimensional large-eddy simulations in subsequent papers.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3843-3854 |
| Number of pages | 12 |
| Journal | Journal of the Atmospheric Sciences |
| Volume | 73 |
| Issue number | 10 |
| DOIs | |
| State | Published - 2016 |
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Keywords
- Circulation/ dynamics
- Dynamics
- Tornadogenesis
- Turbulence
ASJC Scopus subject areas
- Atmospheric Science
Cite this
Axisymmetric Tornado simulations at high reynolds number. / Rotunno, Richard; Bryan, George H.; Nolan, David S; Dahl, Nathan A.
In: Journal of the Atmospheric Sciences, Vol. 73, No. 10, 2016, p. 3843-3854.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Axisymmetric Tornado simulations at high reynolds number
AU - Rotunno, Richard
AU - Bryan, George H.
AU - Nolan, David S
AU - Dahl, Nathan A.
PY - 2016
Y1 - 2016
N2 - This study is the first in a series that investigates the effects of turbulence in the boundary layer of a tornado vortex. In this part, axisymmetric simulations with constant viscosity are used to explore the relationships between vortex structure, intensity, and unsteadiness as functions of diffusion (measured by a Reynolds number Rer) and rotation (measured by a swirl ratio Sr). A deep upper-level damping zone is used to prevent upper-level disturbances from affecting the low-level vortex. The damping zone is most effective when it overlaps with the specified convective forcing, causing a reduction to the effective convective velocity scale We. With this damping in place, the tornado-vortex boundary layer shows no sign of unsteadiness for a wide range of parameters, suggesting that turbulence in the tornado boundary layer is inherently a three-dimensional phenomenon. For high Rer, the most intense vortices have maximum mean tangential winds well in excess of We, and maximum mean vertical velocity exceeds 3 times We. In parameter space, the most intense vortices fall along a line that follows Sr~Rer -1/3, in agreement with previous analytical predictions by Fiedler and Rotunno. These results are used to inform the design of three-dimensional large-eddy simulations in subsequent papers.
AB - This study is the first in a series that investigates the effects of turbulence in the boundary layer of a tornado vortex. In this part, axisymmetric simulations with constant viscosity are used to explore the relationships between vortex structure, intensity, and unsteadiness as functions of diffusion (measured by a Reynolds number Rer) and rotation (measured by a swirl ratio Sr). A deep upper-level damping zone is used to prevent upper-level disturbances from affecting the low-level vortex. The damping zone is most effective when it overlaps with the specified convective forcing, causing a reduction to the effective convective velocity scale We. With this damping in place, the tornado-vortex boundary layer shows no sign of unsteadiness for a wide range of parameters, suggesting that turbulence in the tornado boundary layer is inherently a three-dimensional phenomenon. For high Rer, the most intense vortices have maximum mean tangential winds well in excess of We, and maximum mean vertical velocity exceeds 3 times We. In parameter space, the most intense vortices fall along a line that follows Sr~Rer -1/3, in agreement with previous analytical predictions by Fiedler and Rotunno. These results are used to inform the design of three-dimensional large-eddy simulations in subsequent papers.
KW - Circulation/ dynamics
KW - Dynamics
KW - Tornadogenesis
KW - Turbulence
UR - http://www.scopus.com/inward/record.url?scp=84994153752&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84994153752&partnerID=8YFLogxK
U2 - 10.1175/JAS-D-16-0038.1
DO - 10.1175/JAS-D-16-0038.1
M3 - Article
AN - SCOPUS:84994153752
VL - 73
SP - 3843
EP - 3854
JO - Journals of the Atmospheric Sciences
JF - Journals of the Atmospheric Sciences
SN - 0022-4928
IS - 10
ER -