scholarly journals Numerical study on the standing morphology of an oblique detonation wave under the influence of an incoming boundary layer

Open Physics ◽  
2015 ◽  
Vol 13 (1) ◽  
Author(s):  
Jin Zhou ◽  
Yu Liu ◽  
Zhi-yong Lin
Keyword(s):  
Boundary Layer ◽  
Detonation Wave ◽  
Transverse Wave ◽  
Large Scale ◽  
Numerical Study ◽  
Boundary Layer Separation ◽  
Adiabatic Wall ◽  
Scale Separation ◽  
Oblique Detonation Wave ◽  
Wall Condition

AbstractThe influence of an incoming boundary layer to the standing morphology of an oblique detonation wave (ODW) induced by a compression ramp is numerically studied in this paper. The Spalart-Allmaras (SA) turbulence model is used to perform simulation of detonationboundary- layer interactions. Three different wall conditions are applied to realize control on the boundary-layer separation scales. Accordingly, different standing morphologies of the ODWs are obtained, including smooth ODW (without transverse wave) under no-slip, adiabatic wall condition with large-scale separation, abrupt ODW (with transverse wave) under no-slip, cold wall condition with moderate-scale separation, and bow-shaped detached ODW under slipwall condition without a boundary layer.

Large Eddy Simulations of Separated Boundary Layer With Pressure Gradient and Heat Transfer

2018 ◽  
Author(s):  
Yifei Wu ◽  
Weihao Zhang ◽  
Zhengping Zou ◽  
Jiang Chen
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Large Scale ◽  
Separation Bubble ◽  
Bottom Wall ◽  
Wall Heat Transfer ◽  
Adiabatic Wall ◽  
Wall Condition ◽  
Spanwise Vortex ◽  
Isothermal Wall

Separated boundary layers of the low pressure turbine blade suction surface under wall heat transfer and pressure gradient conditions are investigated using large eddy simulations (LES) in this paper. The study constructed a converging-diverging channel with a flat plate as the bottom wall, and the pressure distribution of the bottom wall is similar to that of a high lift low pressure turbine blade suction surface. The boundary layer was investigated under different heat transfer boundary conditions of the bottom wall (i.e., the adiabatic wall and the isothermal wall with the wall temperature being 0.8 times of the inflow temperature). The time-averaged flow parameters and the separation bubble characteristics were analyzed and discussed. The evolution of coherent structure diagrams of the boundary layer was also obtained to study the evolution process of the vortex. The results show that the cooled isothermal wall condition can significantly suppress the separation bubble and reduce the frequency of the large scale spanwise vortex roll-up. Under the two wall heat transfer conditions, the scale of the near wall small scale spanwise vortex is similar as well as the scale of the large scale spanwise wortex. The location of the vortex are also approximate under the two wall heat transfer conditions, but the position of the large scale spanwise vortex shedding from separated laminar boundary layers moves upstream under the cooled isothermal wall condition, and the transition process is more rapid than that of the adiabatic wall condition.

Non-uniqueness in wakes and boundary layers

1984 ◽  
Vol 391 (1800) ◽  
pp. 1-26 ◽  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Near Wake ◽  
Algebraic Decay ◽  
Scale Separation ◽  
Boundary Layer Equations ◽  
Classical Boundary ◽  
Streamlined Flow ◽  
High Reynolds

In streamlined flow past a flat plate aligned with a uniform stream, it is shown that ( a ) the Goldstein near-wake and ( b ) the Blasius boundary layer are non-unique solutions locally for the classical boundary layer equations, whereas ( c ) the Rott-Hakkinen very-near-wake appears to be unique. In each of ( a ) and ( b ) an alternative solution exists, which has reversed flow and which apparently cannot be discounted on immediate grounds. So, depending mainly on how the alternatives for ( a ), ( b ) develop downstream, the symmetric flow at high Reynolds numbers could have two, four or more steady forms. Concerning non-streamlined flow, for example past a bluff obstacle, new similarity forms are described for the pressure-free viscous symmetric closure of a predominantly slender long wake beyond a large-scale separation. Features arising include non-uniqueness, singularities and algebraic behaviour, consistent with non-entraining shear layers with algebraic decay. Non-uniqueness also seems possible in reattachment onto a solid surface and for non-symmetric or pressure-controlled flows including the wake of a symmetric cascade.

Numerical Study of Wall Influence on Boundary-Layer Transition for Two-Dimensional NACA 16-012 and 4412 Hydrofoil Sections

1990 ◽  
Vol 34 (01) ◽  
pp. 38-47
Author(s):  
R. Latorre ◽  
R. Baubeau
Keyword(s):  
Boundary Layer ◽  
Test Section ◽  
Numerical Study ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Turbulent Separation ◽  
Side Pressure ◽  
Effective Angle

One of the difficulties in hydrofoil model tests is the relatively low Reynolds number of the test piece and the presence of the test section walls. This paper presents the results of systematic calculations of the potential flow field of NA 4412 and NACA 16-012 hydrofoil in a test section with wall-to-chord ratios h/c -1.0. The corresponding boundary-layer calculations using the CERT calculation scheme are presented to show the influence of the nearby walls on shifting the location of the boundary-layer laminar-turbulent separation as well as turbulent separation. By introducing an effective angle of attack, it is possible to obtain close agreement in the calculated and measured suction side pressure distortion as well as the locations of the boundary-layer separation and transition.

Turbine blade boundary layer separation suppression via synthetic jet: An experimental and numerical study

2012 ◽  
Vol 21 (5) ◽  
pp. 404-412 ◽  
Author(s):  
C. Bernardini ◽  
M. Carnevale ◽  
M. Manna ◽  
F. Martelli ◽  
D. Simoni ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Turbine Blade ◽  
Numerical Study ◽  
Boundary Layer Separation ◽  
Synthetic Jet ◽  
Layer Separation

On the Axisymmetric Vortex Flow Over a Flat Surface

1969 ◽  
Vol 36 (3) ◽  
pp. 614-619 ◽  
Author(s):  
E. W. Schwiderski
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Critical Reynolds Number ◽  
Numerical Study ◽  
Lower Boundary ◽  
Tangential Velocity ◽  
Slow Motion ◽  
Boundary Layer Separation ◽  
Local Boundary ◽  
Self Similar

The numerical study of the interaction of a potential vortex with a stationary surface recently published by Kidd and Farris [1] is extended through a transformation of the boundary-value problem to Volterra integral equations. The new calculations verified the results by Kidd and Farris and improved the bounds of the critical Reynolds number Nc, beyond which no self-similar vortex flows exist, to 5.5 < Nc < 5.6 The breakdown of the self-similar motions develops through an instability in the lower boundary layer, which is indicated by two inflection points in the tangential velocity profile. At the critical Reynolds number the lower inflection point reaches the surface and indicates the beginning of boundary-layer separation in the wake-type flow. If the Stokes linearization is applied, one arrives at a new Stokes paradox. However, this “paradox” can be resolved by correcting the free-stream pressure distortion of the Stokes approximation. The new slow-motion approximation is nonlinear and yields an integral which is also free of the Whitehead paradox. The properties of the new exact solution confirm the novel flow features previously detected in almost self-similar motions, which were constructed by adjustable local boundary-layer approximations.

Boundary Layer Separation Control With Fluidic Oscillators

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Ciro Cerretelli ◽  
Kevin Kirtley
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Separated Flow ◽  
Boundary Layer Separation ◽  
Maximum Pressure ◽  
Suction Surface ◽  
Stator Vane ◽  
Average Operating ◽  
Fluidic Actuators ◽  
Layer Flow

Fluidic oscillating valves have been used in order to apply unsteady boundary layer injection to “repair” the separated flow of a model diffuser, where the hump pressure gradient represents that of the suction surface of a highly loaded stator vane. The fluidic actuators employed in this study consist of a fluidic oscillator that has no moving parts or temperature limitations and is therefore more attractive for implementation on production turbomachinery. The fluidic oscillators developed in this study generate an unsteady velocity with amplitudes up to 60% rms of the average operating at nondimensional blowing frequencies (F+) in the range of 0.6<F+<6. These actuators are able to fully reattach the flow and achieve maximum pressure recovery with a 60% reduction of injection momentum required and a 30% reduction in blowing power compared with optimal steady blowing. Particle image velocimetry velocity and vorticity measurements have been performed, which show no large-scale unsteadiness in the controlled boundary layer flow.

Potential Flow Field Generated by Downstream Moving Bars and Propagated on a Turbine Blade at Low Reynolds Number

2011 ◽  
Author(s):  
Ve´ronique Penin ◽  
Pascale Kulisa ◽  
Franc¸ois Bario
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Numerical Study ◽  
Three Dimensional ◽  
Potential Effect ◽  
Navier Stokes ◽  
Turbine Cascade ◽  
Wake Interaction ◽  
Rotor Stator Interaction ◽  
The Stability

During the last few decades, the size and weight of turbo-machinery have been continuously reduced. However, by decreasing the distance between rows, rotor-stator interaction is strengthened. Two interactions now have the same magnitude: wake interaction and potential effect. Studying this effect is essential to understand rotor-stator interactions. Indeed, this phenomenon influences the whole flow, including the boundary layer of the upstream and downstream blades, ergo the stability of the flow and the efficiency of the machine. A large scale turbine cascade followed by a specially designed rotating cylinder system is used. Synchronised velocity LDA measurements on the vane profile show the flow and boundary layer behavior due to the moving bars. To help the general understanding and to corroborate our experimental results, numerical investigations are carried out with an unsteady three dimensional Navier-Stokes code. Moreover, the numerical study informs about the potential disturbance to the whole flow of the cascade.

scholarly journals Numerical study of oblique detonation wave initiation in a stoichiometric hydrogen-air mixture

2015 ◽  
Vol 27 (9) ◽  
pp. 096101 ◽  
Author(s):  
Tao Wang ◽  
Yining Zhang ◽  
Honghui Teng ◽  
Zonglin Jiang ◽  
Hoi Dick Ng
Keyword(s):  
Detonation Wave ◽  
Numerical Study ◽  
Oblique Detonation Wave
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