An Assessment of the Two-Layer Quasi-Laminar Theory of Relaminarization Through Recent High-Re Accelerated Turbulent Boundary Layer Experiments

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Rajesh Ranjan ◽  
Roddam Narasimha
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Pressure Gradients ◽  
Number Range ◽  
High Acceleration ◽  
Precise Role ◽  
Good Agreement

The phenomenon of relaminarization is observed in many flow situations, including that of an initially turbulent boundary layer (TBL) subjected to strong favorable pressure gradients (FPG). As several experiments on relaminarizing flows have indicated, TBLs subjected to high pressure gradients do not follow the universal log-law, and (for this and other reasons) the prediction of boundary layer (BL) parameters using current turbulence models has not been successful. However, a quasi-laminar theory (QLT; proposed in 1973), based on a two-layer model to explain the later stages of relaminarization, showed good agreement with the experimental data available at that time. These data were mostly at relatively low Re and hence left the precise role of viscosity undefined. QLT, therefore, could not be assessed at high-Re. Recent experiments, however, have provided more comprehensive data and extended the Reynolds number range to nearly 5 × 103 in momentum thickness. These data provide a basis for a reassessment of QLT, which is revisited here with an improved predictive code. It is demonstrated that even for these high-Re flows subjected to high acceleration, QLT provides good agreement with experimental results, and therefore, has the potential to substitute for Reynolds-averaged Navier–Stokes (RANS) simulations in high FPG regions.

scholarly journals The effect of wall cooling on a compressible turbulent boundary layer

1974 ◽  
Vol 66 (3) ◽  
pp. 507-528 ◽  
Author(s):  
R. L. Gran ◽  
J. E. Lewis ◽  
T. Kubota
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Wall Temperature ◽  
High Speed ◽  
Thermal Boundary Layer ◽  
Pressure Gradients ◽  
Wall Boundary Layer ◽  
Free Stream Mach Number ◽  
High Speed Data ◽  
Good Agreement

Experimental results are presented for two turbulent boundary-layer experiments conducted at a free-stream Mach number of 4 with wall cooling. The first experiment examines a constant-temperature cold-wall boundary layer subjected to adverse and favourable pressure gradients. It is shown that the boundary-layer data display good agreement with Coles’ general composite boundary-layer profile using Van Driest's transformation. Further, the pressuregradient parameter βK found in previous studies to correlate adiabatic highspeed data with low-speed data also correlates the present cooled-wall high-speed data. The second experiment treats the response of a constant-pressure highspeed boundary layer to a near step change in wall temperature. It is found that the growth rate of the thermal boundary layer within the existing turbulent boundary layer varies considerably depending upon the direction of the wall temperature change. For the case of an initially cooled boundary layer flowing onto a wall near the recovery temperature, it is found that δT ∼ x whereas the case of an adiabatic boundary layer flowing onto a cooled wall gives δT ∼ x½. The apparent origin of the thermal boundary layer also changes considerably, which is accounted for by the variation in sublayer thicknesses and growth rates within the sublayer.

Assessment of DES Models for Separated Flow From a Hump in a Turbulent Boundary Layer

2007 ◽  
Author(s):  
Daniel C. Lyons ◽  
Leonard J. Peltier ◽  
Frank J. Zajaczkowski ◽  
Eric G. Paterson
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Mean Field ◽  
Turbulence Models ◽  
Separated Flow ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Rans Modeling

Turbulent flow past the Glauert-Goldschmied body, a flow-control hump in a turbulent boundary layer, is studied numerically using detached-eddy simulation (DES), zonal detached-eddy simulation (ZDES), delayed detached-eddy simulation (DDES), and Reynolds-Averaged Navier-Stokes (RANS) modeling. The geometry is smooth so the downstream separation point is not set by facets of the geometry but is a function of the pressure gradient, a challenging condition for turbulence models. Comparisons to experimental data show that RANS with the Spalart-Allmaras turbulence model predicts the mean-field statistics well. The ZDES and DDES methods perform better than the DES formulation and are comparable to RANS in most statistics. An analysis of model behavior indicates that modeled stress depletion in the detached shear layer shortly after separation leads to loss of accuracy in the DES variants.

Numerical Simulation of Turbine Blade Boundary Layer and Heat Transfer and Assessment of Turbulence Models

1997 ◽  
Vol 119 (4) ◽  
pp. 794-801 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Bypass Transition ◽  
Boundary Layer Development ◽  
Low Reynolds ◽  
Layer Development

The boundary layer development and convective heat transfer on transonic turbine nozzle vanes are investigated using a compressible Navier–Stokes code with three low-Reynolds-number k–ε models. The mean-flow and turbulence transport equations are integrated by a four-stage Runge–Kutta scheme. Numerical predictions are compared with the experimental data acquired at Allison Engine Company. An assessment of the performance of various turbulence models is carried out. The two modes of transition, bypass transition and separation-induced transition, are studied comparatively. Effects of blade surface pressure gradients, free-stream turbulence level, and Reynolds number on the blade boundary layer development, particularly transition onset, are examined. Predictions from a parabolic boundary layer code are included for comparison with those from the elliptic Navier–Stokes code. The present study indicates that the turbine external heat transfer, under real engine conditions, can be predicted well by the Navier–Stokes procedure with the low-Reynolds-number k–ε models employed.

Morphing Continuum Theory: Incorporating the Physics of Microstructures to Capture the Transition to Turbulence Within a Boundary Layer

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Louis B. Wonnell ◽  
James Chen
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Ad Hoc ◽  
Constitutive Relations ◽  
Turbulence Models ◽  
Continuum Theory ◽  
Transition To Turbulence ◽  
Flow Turbulence ◽  
Good Agreement ◽  
Inherent Advantage

A boundary layer with Re = 106 is simulated numerically on a flat plate using morphing continuum theory. This theory introduces new terms related to microproperties of the fluid. These terms are added to a finite-volume fluid solver with appropriate boundary conditions. The success of capturing the initial disturbances leading to turbulence is shown to be a byproduct of the physical and mathematical rigor underlying the balance laws and constitutive relations introduced by morphing continuum theory (MCT). Dimensionless equations are introduced to produce the parameters driving the formation of disturbances leading to turbulence. Numerical results for the flat plate are compared with the experimental results determined by the European Research Community on Flow, Turbulence, and Combustion (ERCOFTAC) database. Experimental data show good agreement inside the boundary layer and in the bulk flow. Success in predicting conditions necessary for turbulent and transitional (T2) flows without ad hoc closure models demonstrates the theory's inherent advantage over traditional turbulence models.

Predicting Turbulent Boundary Layer Wall Pressure Fluctuations in Adverse Pressure Gradients

2005 ◽  
Author(s):  
Frank J. Aldrich
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Pressure Fluctuations ◽  
Adverse Pressure Gradient ◽  
Wall Pressure ◽  
Prediction Tool ◽  
Pressure Gradients ◽  
Wall Pressure Fluctuations ◽  
The Difference

A physics-based approach is employed and a new prediction tool is developed to predict the wavevector-frequency spectrum of the turbulent boundary layer wall pressure fluctuations for subsonic airfoils under the influence of adverse pressure gradients. The prediction tool uses an explicit relationship developed by D. M. Chase, which is based on a fit to zero pressure gradient data. The tool takes into account the boundary layer edge velocity distribution and geometry of the airfoil, including the blade chord and thickness. Comparison to experimental adverse pressure gradient data shows a need for an update to the modeling constants of the Chase model. To optimize the correlation between the predicted turbulent boundary layer wall pressure spectrum and the experimental data, an optimization code (iSIGHT) is employed. This optimization module is used to minimize the absolute value of the difference (in dB) between the predicted values and those measured across the analysis frequency range. An optimized set of modeling constants is derived that provides reasonable agreement with the measurements.

Numerical simulation of crossing-shock-wave/turbulent-boundary-layer interaction using a two-equation model of turbulence

2000 ◽  
Vol 409 ◽  
pp. 121-147 ◽  
Author(s):  
D. KNIGHT ◽  
M. GNEDIN ◽  
R. BECHT ◽  
A. ZHELTOVODOV
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Shock Wave ◽  
Turbulent Boundary Layer ◽  
Three Dimensional ◽  
Equation Model ◽  
Adiabatic Wall ◽  
Layer Interaction ◽  
Boundary Layer Interaction ◽  
Good Agreement

A crossing-shock-wave/turbulent-boundary-layer interaction is investigated using the k–ε turbulence model with a new low-Reynolds-number model based on the approach of Saffman (1970) and Speziale et al. (1990). The crossing shocks are generated by two wedge-shaped fins with wedge angles α1 and α2 attached normal to a flat plate on which an equilibrium supersonic turbulent boundary layer has developed. Two configurations, corresponding to the experiments of Zheltovodov et al. (1994, 1998a, b), are considered. The free-stream Mach number is 3.9, and the fin angles are (α1, α2) = (7°, 7°) and (7°, 11°). The computed surface pressure displays very good agreement with experiment. The computed surface skin friction lines are in close agreement with experiment for the initial separation, and are in qualitative agreement within the crossing shock interaction region. The computed heat transfer is in good agreement with experiment for the (α1, α2) = (7°, 7°) configuration. For the (α1, α2) = (7°, 11°) configuration, the heat transfer is significantly overpredicted within the three-dimensional interaction. The adiabatic wall temperature is accurately predicted for both configurations.

Intermittency measurements in the turbulent boundary layer

1966 ◽  
Vol 25 (4) ◽  
pp. 719-735 ◽  
Author(s):  
H. Fiedler ◽  
M. R. Head
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Focal Point ◽  
Pressure Gradients ◽  
Narrow Beam ◽  
Hot Wire ◽  
Characteristic Parameters ◽  
Mean Velocity ◽  
Form Parameter ◽  
The Mean

An improved version of Corrsin & Kistler's method has been used to measure intermittency in favourable and adverse pressure gradients, and the characteristic parameters of the intermittency have been related to the form parameterHof the mean velocity profiles.It is found that with adverse pressure gradients the centre of intermittency moves outward from the surface while the width of the intermittent zone decreases. The converse is true of favourable pressure gradients, and it seems likely that at sufficiently low values ofHthe flow over the full depth of the layer is only intermittently turbulent.A new method of intermittency measurement is presented which makes use of a photo-electric probe. Smoke is introduced into the boundary layer and illuminated by a narrow beam of parallel light normal to the surface. The photoelectric probe is focused on the illuminated region and a signal is generated when smoke passes through the focal point of the probe lens. Comparison of this signal with the output from a hot-wire at very nearly the same point shows the identity of smoke and turbulence distributions.

Sign in / Sign up

Export Citation Format

Share Document