Numerical simulation of boundary-layer excitation by surface heating/cooling

A theoretical and numerical study is carried out to investigate the transformation of the wave boundary layer from non-depth-limited (wave-like boundary layer) to depth-limited one (current-like boundary layer) over a smooth bottom. A long period of wave motion is not sufficient to induce depth-limited properties, although it has simply been assumed in various situations under long waves, such as tsunami and tidal currents. Four criteria are obtained theoretically for recognizing the inception of the depth-limited condition under waves. To validate the theoretical criteria, numerical simulation results using a turbulence model as well as laboratory experiment data are employed. In addition, typical field situations induced by tidal motion and tsunami are discussed to show the usefulness of the proposed criteria.

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Numerical Simulation about Reconstruction of the Boundary Layer

Energies ◽

10.3390/en10122074 ◽

2017 ◽

Vol 10 (12) ◽

pp. 2074

Author(s):

Yan Li ◽

Chuan Li ◽

Yajie Wu ◽

Cong Liu ◽

Han Yuan ◽

...

Keyword(s):

Numerical Simulation ◽

Boundary Layer

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

Volume 2D: Turbomachinery ◽

10.1115/gt2014-25685 ◽

2014 ◽

Cited By ~ 2

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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