Implicit unstructured Navier-Stokes simulation of leading edge separation over a pitching airfoil

1997 ◽  
Author(s):  
Nora Okong'o ◽  
Doyle Knight ◽  
Nora Okong'o ◽  
Doyle Knight
Keyword(s):  
Leading Edge ◽  
Navier Stokes ◽  
Pitching Airfoil ◽  
Edge Separation

scholarly journals Leading edge separation: a comparison between interaction theory and Navier-Stokes computations

PAMM ◽  
2003 ◽  
Vol 2 (1) ◽  
pp. 312-313
Author(s):  
S Braun ◽  
A Kluwick ◽  
M Trenker
Keyword(s):  
Leading Edge ◽  
Navier Stokes ◽  
Interaction Theory ◽  
Edge Separation

Two-dimensional unsteady leading-edge separation on a pitching airfoil

AIAA Journal ◽  
1994 ◽  
Vol 32 (4) ◽  
pp. 673-681 ◽  
Author(s):  
P. Ghosh Choudhuri ◽  
D. D. Knight ◽  
M. R. Visbal
Keyword(s):  
Leading Edge ◽  
Two Dimensional ◽  
Pitching Airfoil ◽  
Edge Separation

scholarly journals Modeling and Prediction of the Laminar Leading-Edge Separation and Transition in a Blade-Cascade Flow

1996 ◽  
Author(s):  
Dimitri P. Tselepidakis ◽  
Sung-Eun Kim
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Plate Boundary ◽  
Leading Edge ◽  
Suction Side ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Real Flow ◽  
Side Flow ◽  
Edge Separation

This paper presents the computation of the flow around a controlled diffusion compressor cascade. Features associated with by-pass transition close to the leading edge — including laminar leading-edge separation — contribute significantly to the evolution of the boundary layer on the blade surface. Previous studies have demonstrated that conventional k-ε models, based on linear or non-linear Boussinesq stress-strain relations, are able to capture by-pass transition in simple shear, but are unable to resolve transitional features in complex strain, like the leading-edge separation bubble, which is of considerable influence to the suction-side flow at high inlet angle. Here, the k-ω turbulence model has been implemented in a nonstaggered, finite-volume based segregated Reynolds-Averaged Navier-Stokes solver. We demonstrate that this model, if properly sensitized to the generation of turbulence by irrotational strains, is capable of capturing the laminar leading-edge separation bubble. The real flow around the leading edge is laminar and the transition is only provoked on the reattachment region. Additional investigation of transition in a flat-plate boundary layer development has also produced reasonably promising results.

Laminar hypersonic leading edge separation – a numerical study

2017 ◽  
Vol 821 ◽  
pp. 624-646 ◽  
Author(s):  
Amna Khraibut ◽  
S. L. Gai ◽  
L. M. Brown ◽  
A. J. Neely
Keyword(s):  
Wall Temperature ◽  
Numerical Study ◽  
Separated Flow ◽  
Leading Edge ◽  
Slip Boundary Condition ◽  
Navier Stokes ◽  
Recirculation Region ◽  
Slip Boundary ◽  
Limiting Case ◽  
Edge Separation

This paper describes laminar hypersonic leading edge separation. Such a configuration of separated flow was originally studied by Chapman et al. (NACA Tech. Rep. 1356, 1958) at supersonic Mach numbers as it is particularly amenable to theoretical analysis and assumes no pre-existing boundary layer. It can be considered as a limiting case of much studied generic configurations such as separation at a compression corner and separated flow behind a base. A numerical investigation is described using a compressible Navier–Stokes solver assuming perfect gas air, no slip boundary condition and a non-catalytic surface. A moderate enthalpy flow of $3.1\times 10^{6}~\text{J}~\text{kg}^{-1}$ with a unit Reynolds number of $1.34\times 10^{6}~\text{ m}^{-1}$ and a Mach number of 9.66 was considered. The resulting separated flow is analysed in the context of viscous–inviscid interaction and interpreted in terms of ‘triple-deck’ concepts. Particular emphasis is given to wall temperature effects. The effects of strong to moderate wall cooling on flow in the separated region as well as on processes of separation, reattachment and separation length, are highlighted. The numerical simulations have also shown the existence of a secondary eddy embedded within the primary recirculation region, with its size, shape and position, being strongly affected by the wall temperature.

Effects of compressibility, pitch rate, and Reynolds number on unsteady incipient leading-edge boundary layer separation over a pitching airfoil

1996 ◽  
Vol 308 ◽  
pp. 195-217 ◽  
Author(s):  
P. Ghosh Choudhuri ◽  
D. D. Knight
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Stokes Equations ◽  
Leading Edge ◽  
Boundary Layer Separation ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Approximate Factorization ◽  
Simultaneous Formation ◽  
Pitching Airfoil

The effects of compressibility, pitch rate and Reynolds number on the initial stages of two-dimensional unsteady separation of laminar subsonic flow over a pitching NACA-0012 airfoil have been studied numerically. The approach involves the simulation of the flow by solving the two-dimensional unsteady compressible laminar Navier-Stokes equations employing the implicit approximate-factorization algorithm of Beam & Warming and a boundary-fitted C-grid. The algorithm has been extensively validated through comparison with analytical and previous numerical results. The computations display several important trends for the ‘birth’ of the primary recirculating region which is a principal precursor to leading-edge separation. Increasing the non-dimensional pitch rate from 0.05 to 0.2 at a fixed Reynolds number and Mach number delays the formation of the primary recirculating region. The primary recirculating region also forms closer to the leading edge. Increasing the Mach number from 0.2 to 0.5 at a fixed Reynolds number and pitch rate causes a delay in the formation of the primary recirculating region and also leads to its formation farther from the airfoil top surface. The length scale associated with the recirculating regions increases as well. Increasing the Reynolds number from 104 to 105 at a fixed Mach number and pitch rate hastens the appearance of the primary recirculating region. A shock appears on the top surface at a Reynolds number of 105 along with the simultaneous formation of multiple recirculating regions near the leading edge.

Rotational temperature imaging of a leading-edge separation in hypervelocity flow

2019 ◽  
Author(s):  
Laurent M. Le Page ◽  
Matthew Barrett ◽  
Sean O’Byrne ◽  
Sudhir L. Gai
Keyword(s):  
Rotational Temperature ◽  
Leading Edge ◽  
Temperature Imaging ◽  
Edge Separation

Three-Dimensional and Rotational Aerodynamics on the NREL Phase VI Wind Turbine Blade

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Alvaro Gonzalez ◽  
Xabier Munduate
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Three Dimensional ◽  
Separated Flow ◽  
Leading Edge ◽  
Wind Turbine Blade ◽  
Trailing Edge ◽  
Rotating Blade ◽  
Nrel Phase Vi ◽  
Edge Separation

This work undertakes an aerodynamic analysis over the parked and the rotating NREL Phase VI wind turbine blade. The experimental sequences from NASA Ames wind tunnel selected for this study respond to the parked blade and the rotating configuration, both for the upwind, two-bladed wind turbine operating at nonyawed conditions. The objective is to bring some light into the nature of the flow field and especially the type of stall behavior observed when 2D aerofoil steady measurements are compared to the parked blade and the latter to the rotating one. From averaged pressure coefficients together with their standard deviation values, trailing and leading edge separated flow regions have been found, with the limitations of the repeatability of the flow encountered on the blade. Results for the parked blade show the progressive delay from tip to root of the trailing edge separation process, with respect to the 2D profile, and also reveal a local region of leading edge separated flow or bubble at the inner, 30% and 47% of the blade. For the rotating blade, results at inboard 30% and 47% stations show a dramatic suppression of the trailing edge separation, and the development of a leading edge separation structure connected with the extra lift.

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