Cholesky decomposition–based generation of artificial inflow turbulence including scalar fluctuation

A downward blowing isothermal wall jet at moderate Reynolds numbers (1,500 to 8,500) with significant inflow turbulence (ca. 6%) was investigated. The flow configuration is an idealization of the air curtains of refrigerated display cases. Flow visualization using particle seeding was employed to identify the flow field eddy dynamics. Particle Image Velocimetry was used to examine the velocity fields in terms of mean and fluctuating values. These diagnostics showed that the air curtain entrainment was dominated by a large variety of eddies that engulfed ambient air into the air curtain. The velocity fields generally showed linear spreading, significant deceleration and high turbulence levels (ca. 25%). It was observed that the air curtain dynamics, velocity fields and growth were not significantly sensitive to Reynolds number variation between Re=3,800 and Re=8,500. However, at low air velocities (Re=1,500), the curtain was found to detach, leading to a large air curtain thickness and high curtain entrainment.

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A Wiener–Kolmogorov Filter for Seasonal Adjustment and the Cholesky Decomposition of a Toeplitz Matrix

SSRN Electronic Journal ◽

10.2139/ssrn.3743076 ◽

2020 ◽

Author(s):

Stephen Pollock ◽

E Mise

Keyword(s):

Toeplitz Matrix ◽

Cholesky Decomposition ◽

Seasonal Adjustment

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High-Fidelity Simulations of a Linear HPT Vane Cascade Subject to Varying Inlet Turbulence

Volume 2A: Turbomachinery ◽

10.1115/gt2017-63079 ◽

2017 ◽

Cited By ~ 1

Author(s):

Richard Pichler ◽

Richard D. Sandberg ◽

Gregory Laskowski ◽

Vittorio Michelassi

Keyword(s):

Heat Flux ◽

Turbulence Intensity ◽

Side Surface ◽

Suction Side ◽

Transition Process ◽

Length Scale ◽

Length Scales ◽

Inflow Turbulence ◽

High Turbulence ◽

Turbulence Length

The effect of inflow turbulence intensity and turbulence length scales have been studied for a linear high-pressure turbine vane cascade at Reis = 590,000 and Mis = 0.93, using highly resolved compressible large-eddy simulations employing the WALE turbulence model. The turbulence intensity was varied between 6% and 20% while values of the turbulence length scales were prescribed between 5% and 20% of axial chord. The analysis focused on characterizing the inlet turbulence and quantifying the effect of the inlet turbulence variations on the vane boundary layers, in particular on the heat flux to the blade. The transition location on the suction side of the vane was found to be highly sensitive to both turbulence intensity and length scale, with the case with turbulence intensity 20% and 20% length scale showing by far the earliest onset of transition and much higher levels of heat flux over the entire vane. It was also found that the transition process was highly intermittent and local, with spanwise parts of the suction side surface of the vane remaining laminar all the way to the trailing edge even for high turbulence intensity cases.

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