scholarly journals Flow dynamics and wall-pressure signatures in a high-Reynolds-number overexpanded nozzle with free shock separation

2020 ◽  
Vol 895 ◽  
Author(s):  
E. Martelli ◽  
L. Saccoccio ◽  
P. P. Ciottoli ◽  
C. E. Tinney ◽  
W. J. Baars ◽  
...  
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Wall Pressure ◽  
Flow Dynamics ◽  
Free Shock Separation ◽  
High Reynolds ◽  
Image Position ◽  
Free Shock

Well Resolved Wall Pressure Measurements in a High Reynolds Number Turbulent Boundary Layer

2004 ◽  
Author(s):  
Brendan F. Perkins
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Surface Pressure ◽  
High Reynolds Number ◽  
Wall Pressure ◽  
Pressure Measurements ◽  
Boundary Layer Turbulence ◽  
High Reynolds ◽  
Salt Playa

In order to better understand boundary layer turbulence at high Reynolds number, the fluctuating wall pressure was measured within the turbulent boundary layer that forms over the salt playa of Utah’s west desert. Pressure measurements simultaneously acquired from an array of nine microphones were analyzed and interpreted. The wall pressure intensity was computed and compared with low Reynolds number data. This analysis indicated that the variance in wall pressure increases logarithmically with Reynolds number. Computed autocorrelations provide evidence for a hierarchy of surface pressure producing scales. Space-time correlations are used to compute broadband convection velocities. The convection velocity data indicate an increasing value for larger sensor separations. To the author’s knowledge, the pressure measurements are the highest Reynolds number, well resolved measurements of fluctuating surface pressure to date.

The wall-pressure spectrum of high-Reynolds-number turbulent boundary-layer flows over rough surfaces

2015 ◽  
Vol 768 ◽  
pp. 261-293 ◽  
Author(s):  
Timothy Meyers ◽  
Jonathan B. Forest ◽  
William J. Devenport
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Boundary Layers ◽  
High Reynolds Number ◽  
Wall Pressure ◽  
Boundary Layer Flows ◽  
High Frequency Region ◽  
Pressure Drag ◽  
Roughness Elements ◽  
High Reynolds

Experiments have been performed on a series of high-Reynolds-number flat-plate turbulent boundary layers formed over rough and smooth walls. The boundary layers were fully rough, yet the elements remained a very small fraction $({<}1.4\,\%)$ of the boundary-layer thickness, ensuring conditions free of transitional effects. The wall-pressure spectrum and its scaling were studied in detail. One of the major findings is that the rough-wall turbulent pressure spectrum at vehicle relevant conditions is comprised of three scaling regions. These include a newly discovered high-frequency region where the pressure spectrum has a viscous scaling controlled by the friction velocity, adjusted to exclude the pressure drag on the roughness elements.

Prediction of Vortex Shedding From a High Reynolds Number Airfoil Using LES With and Without Wall Model

2006 ◽  
Author(s):  
Peter A. Chang ◽  
Meng Wang ◽  
Jonathan Gershfeld
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Vortex Shedding ◽  
High Reynolds Number ◽  
Wall Stress ◽  
Wall Pressure ◽  
Pressure Side ◽  
Stress Model ◽  
High Reynolds

ATTACHED, wall-bounded flows impose computational requirements on LES that increase drastically with Reynolds number. For that reason, even simple geometries, such as airfoils at small angles of attack, with spanwise uniform section shape, challenge the bounds of LES as chord-based Reynolds numbers increase much above 1 million. Of particular concern is the ability of LES to predict the occurrence, and strength of, weak vortex shedding from the airfoil trailing edge (by weak vortex shedding we mean that the acoustic vortex shedding signature may rise only a few decibels above that for the broadband turbulent boundary layer acoustic sources). Correct prediction of weak vortex shedding may depend on accurately predicting the flow over the entire airfoil that includes the attached, turbulent upstream flow, adverse pressure gradient and separated flow regions and finally, the turbulent wake. This paper compares results of two full-LES and two LES with wall-stress model for the flow about a modified NACA 0016 airfoil with a 41° trailing edge apex angle and a slightly convex pressure side. Comparisons of vortex shedding, as measured by the power spectral density (PSD) of wall pressure fluctuations (WPF) on the pressure side of the TE and the PSD of the vertical velocity fluctuations in the wake are made. The results indicate that vortex shedding predictions are dependent upon the stream-wise and spanwise grid resolution. In order to reduce the large computational times required for simulating the high-Reynolds number flows with fully-resolved LES, a wall-stress model that solves the turbulent boundary layer equations in the near-wall region is applied. Compared with the fully-resolved LES, the LES with wall-stress simulations require about 20 percent the number of grid points and require about 10 percent of the computational time. However, the LES with wall stress model results under-predict the vortex shedding peak in the wake and are not able to predict the vortex shedding signature in TE wall pressure spectra. These results indicate that near-wall turbulence structures need to be resolved in order to correctly predict the occurence and strength of vortex shedding.

scholarly journals A self-sustaining process theory for uniform momentum zones and internal shear layers in high Reynolds number shear flows

2020 ◽  
Vol 901 ◽  
Author(s):  
Brandon Montemuro ◽  
Christopher M. White ◽  
Joseph C. Klewicki ◽  
Gregory P. Chini
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Shear Flows ◽  
Shear Layers ◽  
Process Theory ◽  
High Reynolds ◽  
Image Position

Abstract

Modeling the Vertical Spincasting of Large Bimetallic Rolling Mill Rolls

2010 ◽  
Vol 443 ◽  
pp. 15-20
Author(s):  
Léo Studer ◽  
Sylvain Detrembleur ◽  
Benjamin J. Dewals ◽  
Michel Pirotton ◽  
Anne Marie Habraken
Keyword(s):  
Reynolds Number ◽  
Finite Elements ◽  
Rolling Mill ◽  
High Reynolds Number ◽  
Industrial Process ◽  
Flow Dynamics ◽  
Dynamic Effects ◽  
Metal Solidification ◽  
Hot Rolling Mill ◽  
High Reynolds

In order to take into account the dynamic effects of molten metal during solidification, a methodology is presented to interface a metal solidification solver (coupled thermal mechanical metallurgical finite elements solver) with a specifically developed flow dynamics solver. (flow dynamics and thermics finite volume solver) The numerical set of tools is designed to be used for the simulation of bimetallic hot rolling mill rolls vertical spincasting. Modeling the industrial process for these products imply certain specifications on the numerical methods used, mainly due to the size of the geometrical domain, low Rossby & Ekman numbers, and a high Reynolds number.

Statistical structure of the fluctuating wall pressure and its in-plane gradients at high Reynolds number

2008 ◽  
Vol 609 ◽  
pp. 195-220 ◽  
Author(s):  
J. C. KLEWICKI ◽  
P. J. A. PRIYADARSHANA ◽  
M. M. METZGER
Keyword(s):  
Reynolds Number ◽  
Pressure Gradient ◽  
High Reynolds Number ◽  
Low Reynolds Number ◽  
Wall Pressure ◽  
Low Frequencies ◽  
Flux Intensity ◽  
Low Reynolds ◽  
High Reynolds ◽  
Surface Layer Thickness

The fluctuating wall pressure and its gradients in the plane of the surface were measured beneath the turbulent boundary layer that forms over the salt playa of Utah's west desert. Measurements were acquired under the condition of near-neutral thermal stability to best mimic the canonical zero-pressure-gradient boundary-layer flow. The Reynolds number (based on surface-layer thickness, δ, and the friction velocity, uτ) was estimated to be 1 × 106 ± 2 × 105. The equivalent sandgrain surface roughness was estimated to be in the range 15≤ks+≤85. Pressure measurements acquired simultaneously from an array of up to ten microphones were analysed. A compact array of four microphones was used to estimate the instantaneous streamwise and spanwise gradients of the surface pressure. Owing to the large length scales and low flow speeds, attaining accurate pressure statistics in the present flow required sensors capable of measuring unusually low frequencies. The effects of imperfect spatial and temporal resolution on the present measurements were also explored. Relative to pressure, pressure gradients exhibit an enhanced sensitivity to spatial resolution. Their accurate measurement does not, however, require fully capturing the low frequencies that are inherent and significant in the pressure itself. The present pressure spectra convincingly exhibit over three decades of approximately −1 slope. Comparisons with low-Reynolds-number data support previous predictions that the inner normalized wall pressure variance increases logarithmically with Reynolds number. The wall pressure autocorrelation exhibits its first zero-crossing at an advected length that is between one tenth and one fifth of the surface-layer thickness. Under any of the normalizations investigated, the present surface vorticity flux intensity values are difficult to reconcile with low-Reynolds-number data trends. Inner variables, however, do yield normalized flux intensity values that are of the same order of magnitude at low and high Reynolds number. Spectra reveal that even at high Reynolds number, the primary contributions to the pressure gradient intensities occur over a relatively narrow frequency range. This frequency range is shown to be consistent with the scale of the sublayer pocket motions. In accord with low-Reynolds-number data, the streamwise pressure gradient signals at high Reynolds number are also characterized by statistically significant pairings of opposing sign fluctuations.

scholarly journals Large-scale structures in high-Reynolds-number rotating Waleffe flow

2019 ◽  
Vol 884 ◽  
Author(s):  
Shafqat Farooq ◽  
Martin Huarte-Espinosa ◽  
Rodolfo Ostilla-Mónico
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Large Scale ◽  
Large Scale Structures ◽  
Scale Structures ◽  
High Reynolds ◽  
Image Position

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