Adaptive Wavelet-based Delayed Detached Eddy Simulations of Anisothermal Channel Flows with High Transverse Temperature Gradients

Abstract Investigations of tornadogenesis in supercells attempt to find the origin of the tornado’s large vorticity by determining vorticity generation and amplification along trajectories that enter the tornado from a horizontally uniform unstable environment. Insights into tornadogenesis are provided by finding analytical formulas for vorticity variations along streamlines in idealized, steady, inviscid, isentropic inflows of dry air imported from the environment. The streamlines and vortex lines lie in the stationary isentropic surfaces so the vorticity is 2D. The transverse vorticity component (positive leftward of the streamlines) arises from imported transverse vorticity and from baroclinic vorticity accumulated in streamwise temperature gradients. The streamwise component stems from imported streamwise vorticity, from baroclinic vorticity accrued in transverse temperature gradients, and from positive transverse vorticity that is turned streamwise in cyclonically curved flow by a “river-bend process.” It is amplified in subsiding air as it approaches the ground. Streamwise stretching propagates a parcel’s streamwise vorticity forward in time. In steady flow, vorticity decomposes into baroclinic vorticity and two barotropic parts ωBTIS and ωBTIC arising from imported storm-relative streamwise vorticity (directional shear) and storm-relative crosswise vorticity (speed shear), respectively. The Beltrami vorticity ωBTIS is purely streamwise. It explains why abundant environmental storm-relative streamwise vorticity close to ground favors tornadic supercells. It flows directly into the updraft base unmodified apart from streamwise stretching, establishing mesocyclonic rotation and strong vortex suction at low altitudes. Increase (decrease) in storm-relative environmental wind speed with height near the ground accelerates (delays) tornadogenesis as positive (negative) ωBTIC is turned into streamwise (antistreamwise) vorticity within cyclonically curved flow around the mesocyclone.

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Effects of Variable Thermal Properties on Moving-Band-Source Temperatures

Journal of Engineering for Industry ◽

10.1115/1.3438658 ◽

1975 ◽

Vol 97 (3) ◽

pp. 1074-1078 ◽

Cited By ~ 2

Author(s):

J. Isenberg ◽

S. Malkin

Keyword(s):

Thermal Properties ◽

Thermal Stresses ◽

Temperature Gradients ◽

Heat Sources ◽

Moving Heat Source ◽

Constant Property ◽

Surface Temperatures ◽

Transverse Temperature ◽

Property Model ◽

Moving Band

Temperatures calculated by moving-heat-source theory for machining and sliding processes are often sufficiently large that the assumption of temperature-independent thermal properties is invalid. In the present paper results of a numerical analysis are presented that consider the effects of variable thermal properties on the temperatures due to a moving-band source. Compared with the constant-property model, the maximum surface temperatures are found to be significantly higher with small Peclet numbers and strong heat sources, but the average surface temperatures within the band are much less affected by the variations of thermal properties with temperature. The variable-property model also indicates significantly larger transverse temperature gradients, a phenomenon that should cause greater thermal stresses.

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A numerical investigation of the effects of a transverse temperature gradient on the formation of regular and irregular acoustic streaming in an enclosure

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/09544062jmes1834 ◽

2010 ◽

Vol 225 (1) ◽

pp. 132-144 ◽

Cited By ~ 1

Author(s):

M K Aktas ◽

T Ozgumus

Keyword(s):

Temperature Gradient ◽

Stokes Equations ◽

Acoustic Streaming ◽

Fluid Motion ◽

Sound Field ◽

Flow Patterns ◽

Temperature Gradients ◽

Left Wall ◽

Steady Streaming ◽

Transverse Temperature

The effects of a transverse temperature gradient on the formation of regular and irregular acoustic streaming structures in air-filled, two-dimensional, rectangular, shallow enclosures carrying a longitudinal sound field are investigated numerically. The fluid motion is induced by the harmonic vibration of the enclosure left wall. The fully compressible form of the Navier—Stokes equations is considered to predict the primary oscillatory and secondary pseudo-steady streaming flow fields. An explicit time-marching flux-corrected transport algorithm is used to simulate the acoustic wave formation, propagation, and the resulting flow patterns in the enclosure. The vertical walls of the enclosure are adiabatic whereas the horizontal walls are heated differentially or symmetrically. The transverse temperature gradients are found to strongly affect the acoustic streaming structures and the velocities. The steady streaming velocities significantly increase when the enclosure horizontal walls are asymmetrically heated for both regular and irregular streaming flows. For irregular streaming, the transverse temperature gradients completely change the flow patterns. The irregular streaming velocities are greatly reduced in case of the symmetric temperature increase of the horizontal walls.

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