scholarly journals Oblique-mode breakdown in hypersonic and high-enthalpy boundary layers over a blunt cone

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Xianliang Chen ◽  
Dongxiao Xu ◽  
Song Fu
Keyword(s):  
Boundary Layer Transition ◽  
Normal Velocity ◽  
Sound Waves ◽  
Mean Flow ◽  
Spontaneous Radiation ◽  
Blunt Cone ◽  
Layer Transition ◽  
High Enthalpy ◽  
Product Term ◽  
Free Stream Mach Number

AbstractThe nonlinear analyses of the hypersonic and high-enthalpy boundary-layer transition had received little attention compared with the widely-studied linear instabilities. In this work, the oblique-mode breakdown, as one of the most available transition mechanisms, is studied using the nonlinear parabolized stability equations (NPSE) with consideration of the thermal-chemical non-equilibrium effects. The flow over a blunt cone is computed at a free-stream Mach-number of 15. The rope-like structures and the spontaneous radiation of sound waves are observed in the schlieren-like picture. It is also illustrated that the disturbances of the species mass and vibrational temperature near the wall are mainly generated by the product term of the wall-normal velocity disturbance and the mean-flow gradient. In comparison to the CPG flow, the TCNE effects destabilize the second mode and push upstream the N factor envelope. The higher growth rate of the oblique wave leads to stronger growth of the streamwise vortices and harmonic waves.

Boundary Layer Transition Under High Free-Stream Turbulence and Strong Acceleration Conditions: Part 1—Mean Flow Results

1997 ◽  
Vol 119 (3) ◽  
pp. 420-426 ◽  
Author(s):  
R. J. Volino ◽  
T. W. Simon
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Free Stream ◽  
Boundary Layer Transition ◽  
Temperature Profiles ◽  
Mean Flow ◽  
Transfer Coefficients ◽  
Mean Velocity ◽  
Layer Transition ◽  
Free Stream Turbulence

Measurements from heated boundary layers along a concave-curved test wall subject to high (initially 8 percent) free-stream turbulence intensity and strong (K = (ν/U∞2) dU∞/dx) as high as 9 × 10−6) acceleration are presented and discussed. Conditions for the experiments were chosen to roughly simulate those present on the downstream half of the pressure side of a gas turbine airfoil. Mean velocity and temperature profiles as well as skin friction and heat transfer coefficients are presented. The transition zone is of extended length in spite of the high free-stream turbulence level. Transitional values of skin friction coefficients and Stanton numbers drop below flat-plate, low-free-stream-turbulence, turbulent flow correlations, but remain well above laminar flow values. The mean velocity and temperature profiles exhibit clear changes in shape as the flow passes through transition. To the authors’ knowledge, this is the first detailed documentation of a high-free-stream-turbulence boundary layer flow in such a strong acceleration field.

Effects of Weak Free Stream Nonuniformity on Boundary Layer Transition (Keynote Paper)

2003 ◽  
Author(s):  
Jonathan H. Watmuff
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Mean Flow ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Tollmien Schlichting ◽  
Distorted Waves ◽  
Thickness Variations

Experiments are described in which well-defined FSN (Free Stream Nonuniformity) distributions are introduced by placing fine wires upstream of the leading edge of a flat plate. Large amplitude spanwise thickness variations are present in the downstream boundary layer resulting from the interaction of the laminar wakes with the leading edge. Regions of elevated background unsteadiness appear on either side of the peak layer thickness, which share many of the characteristics of Klebanoff modes, observed at elevated Free Stream Turbulence (FST) levels. However, for the low background disturbance level of the free stream, the layer remains laminar to the end of the test section (Rx ≈ l.4×106) and there is no evidence of bursting or other phenomena associated with breakdown to turbulence. A vibrating ribbon apparatus is used to demonstrate that the deformation of the mean flow is responsible for substantial phase and amplitude distortion of Tollmien-Schlichting (TS) waves. Pseudo-flow visualization of hot-wire data shows that the breakdown of the distorted waves is more complex and occurs at a lower Reynolds number than the breakdown of the K-type secondary instability observed when the FSN is not present.

scholarly journals Effects of Shock-Tube Cleanliness on Hypersonic Boundary Layer Transition at High Enthalpy

AIAA Journal ◽  
2017 ◽  
Vol 55 (1) ◽  
pp. 332-338 ◽  
Author(s):  
Joseph S. Jewell ◽  
Nicholaus J. Parziale ◽  
Ivett A. Leyva ◽  
Joseph E. Shepherd
Keyword(s):  
Boundary Layer ◽  
Shock Tube ◽  
Boundary Layer Transition ◽  
Hypersonic Boundary Layer ◽  
Layer Transition ◽  
High Enthalpy

A “Laminar + Transition Criteria” Model for Hypersonic Three-Dimensional Boundary Layer Transition Prediction

2015 ◽  
Vol 798 ◽  
pp. 627-631 ◽  
Author(s):  
Ling Zhou ◽  
Chao Yan ◽  
Zi Hui Hao ◽  
Wei Xuan Kong
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Streamwise Velocity ◽  
Boundary Layer Transition ◽  
Blunt Cone ◽  
Layer Transition ◽  
Total Enthalpy ◽  
Transition Prediction ◽  
Transition Criteria ◽  
Dimensional Boundary

A “laminar + transition criteria” model utilizingReθ/MeandReCFcriteria in conjunction with an intermittency functionΓis developed in this paper. With pretreated computational grid and total enthalpyh0=(h0,∞)maxcriteria the boundary layer edge and crossflow velocity can be obtained by using parallel methodology. Validation is accomplished via HIFiRE-5 and a blunt cone with small angle of attack. Results show that computedReθ/MeandReCFdistributions are similar to theN-factor for streamwise instability and crossflow instability from linear PSE methods. The shape and trend of transition regions predicted by the “laminar + transition criteria” model in HIFiRE-5 and blunt cone are in good agreement with the experiment and DNS. However, for the transition induced by inflection point on streamwise velocity profiles, using criteria related to boundary layer thickness is inappropriate and can predict transition onset prematurely.

The role of nonlinear critical layers in boundary layer transition

1995 ◽  
Vol 352 (1700) ◽  
pp. 425-442 ◽  
Keyword(s):  
Asymptotic Methods ◽  
Nonlinear Effects ◽  
Boundary Layer Transition ◽  
Critical Layer ◽  
Mean Flow ◽  
Layer Transition ◽  
Instability Waves ◽  
Laminar Boundary Layers ◽  
Instability Modes ◽  
Critical Layers

Asymptotic methods are used to describe the nonlinear self-interaction between pairs of oblique instability modes that eventually develops when initially linear spatially growing instability waves evolve downstream in nominally two-dimensional laminar boundary layers. The first nonlinear reaction takes place locally within a so-called ‘critical layer’, with the flow outside this layer consisting of a locally parallel mean flow plus a pair of oblique instability waves - which may or may not be accompanied by an associated plane wave. The amplitudes of these waves, which are completely determined by nonlinear effects within the critical layer, satisfy either a single integro-differential equation or a pair of integro-differential equations with quadratic to quartic-type nonlinearities. The physical implications of these equations are discussed.

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