Spatial direct numerical simulation of high-speed boundary-layer flows part I: Algorithmic considerations and validation

1995 ◽  
Vol 7 (1) ◽  
pp. 49-76 ◽  
Author(s):  
C. David Pruett ◽  
Thomas A. Zang ◽  
Chau-Lyan Chang ◽  
Mark H. Carpenter
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Direct Numerical Simulation ◽  
High Speed ◽  
Boundary Layer Flows

Direct Numerical Simulation of Turbulent Flow Around a Rotating Circular Cylinder

2006 ◽  
Vol 129 (1) ◽  
pp. 40-47 ◽  
Author(s):  
Jong-Yeon Hwang ◽  
Kyung-Soo Yang ◽  
Klaus Bremhorst
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Circular Cylinder ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Plane Channel ◽  
Outer Region ◽  
Wave Number ◽  
Boundary Layer Flows ◽  
Rotating Circular Cylinder

Turbulent flow around a rotating circular cylinder has numerous applications including wall shear stress and mass-transfer measurement related to the corrosion studies. It is also of interest in the context of flow over convex surfaces where standard turbulence models perform poorly. The main purpose of this paper is to elucidate the basic turbulence mechanism around a rotating cylinder at low Reynolds numbers to provide a better understanding of flow fundamentals. Direct numerical simulation (DNS) has been performed in a reference frame rotating at constant angular velocity with the cylinder. The governing equations are discretized by using a finite-volume method. As for fully developed channel, pipe, and boundary layer flows, a laminar sublayer, buffer layer, and logarithmic outer region were observed. The level of mean velocity is lower in the buffer and outer regions but the logarithmic region still has a slope equal to the inverse of the von Karman constant. Instantaneous flow visualization revealed that the turbulence length scale typically decreases as the Reynolds number increases. Wavelet analysis provided some insight into the dependence of structural characteristics on wave number. The budget of the turbulent kinetic energy was computed and found to be similar to that in plane channel flow as well as in pipe and zero pressure gradient boundary layer flows. Coriolis effects show as an equivalent production for the azimuthal and radial velocity fluctuations leading to their ratio being lowered relative to similar nonrotating boundary layer flows.

scholarly journals Compressible Direct Numerical Simulation of Low-Pressure Turbines: Part I — Methodology

2014 ◽  
Author(s):  
Richard D. Sandberg ◽  
Richard Pichler ◽  
Liwei Chen ◽  
Roderick Johnstone ◽  
Vittorio Michelassi
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Direct Numerical Simulation ◽  
Environmental Parameters ◽  
Boundary Layer Separation ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Laminar Separation ◽  
Background Turbulence

Modern low pressure turbines (LPT) feature high pressure ratios and moderate Mach and Reynolds numbers, increasing the possibility of laminar boundary-layer separation on the blades. Upstream disturbances including background turbulence and incoming wakes have a profound effect on the behavior of separation bubbles and the type/location of laminar-turbulent transition and therefore need to be considered in LPT design. URANS are often found inadequate to resolve the complex wake dynamics and impact of these environmental parameters on the boundary layers and may not drive the design to the best aerodynamic efficiency. LES can partly improve the accuracy, but has difficulties in predicting boundary layer transition and capturing the delay of laminar separation with varying inlet turbulence levels. Direct Numerical Simulation (DNS) is able to overcome these limitations but has to date been considered too computationally expensive. Here a novel compressible DNS code is presented and validated, promising to make DNS practical for LPT studies. Also, the sensitivity of wake loss coefficient with respect to freestream turbulence levels below 1% is discussed.

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