Visualization of Mach 3.0/3.8 Flow around Blunt Cone with Supersonic Film Cooling

2013 ◽  
Vol 419 ◽  
pp. 432-437
Author(s):  
Yang Zhu Zhu ◽  
Shi He Yi ◽  
Li Feng Tian ◽  
Lin He ◽  
Zhi Chen
Keyword(s):  
Film Cooling ◽  
Mixing Layer ◽  
Flow Structures ◽  
Spatiotemporal Resolution ◽  
Blunt Cone ◽  
Laser Scattering ◽  
Thin Film Layer ◽  
Planar Laser ◽  
Expansion Fan ◽  
Film Layer

Fine instantaneous flow structures of different scales around a blunt cone with or without supersonic film cooling were visualized via nanotracer planar laser scattering (NPLS), which has a high spatiotemporal resolution. The Mach number of the freestream is 3.0 and 3.8 respectively and the air injection is at Mach 2.5. Lots of typical flow structures were visible clearly, such as shock wave, expansion fan, shear layer, mixing layer, K-H vortices and turbulent boundary layer. With injection, the model wall surface can be covered by a thin film layer. While no injection, the flow is similar to the supersonic flow over a backward-facing step and the structures are simpler relatively and there is a longer laminar region. Flow structures with or without film cooling at Mach 3.0 and 3.8 were compared.

scholarly journals Characteristics of Large-Scale Structures in Supersonic Planar Mixing Layer with Finite Thickness

2014 ◽  
Vol 6 ◽  
pp. 878679
Author(s):  
Hailong Zhang ◽  
Jiping Wu ◽  
Jian Chen ◽  
Weidong Liu
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Finite Thickness ◽  
Mixing Layer ◽  
Mixing Enhancement ◽  
Laser Scattering ◽  
Large Scale Structures ◽  
Eddy Simulation ◽  
Planar Laser ◽  
Scale Structures

Nanoparticle-based planar laser scattering (NPLS) experiments and large eddy simulation (LES) were launched to get the fine structure of the supersonic planar mixing layer with finite thickness in the present study. Different from the turbulent development of supersonic planar mixing layer with thin thickness, the development of supersonic planar mixing layer with finite thickness is rapidly. The large-scale structures of mixing layer that possess the characters of quick movement and slow changes transmit to downriver at invariable speed. The transverse results show that the mixing layer is strip of right and dim and possess 3D characteristics. Meanwhile the vortices roll up from two sides to the center. Results indicate that the higher the pressure of the high speed side is, the thicker the mixing layer is. The development of mixing layer is restrained when the pressure of lower speed side is higher. The momentum thickness goes higher with the increase of the clapboard thickness. Through increasing the temperature to change the compression can affect the development of the vortices. The present study can make a contribution to the mixing enhancement and provide initial data for the later investigations.

Fractal features of turbulent/non-turbulent interface in a shock wave/turbulent boundary-layer interaction flow

2019 ◽  
Vol 869 ◽  
Author(s):  
Yi Zhuang ◽  
Huijun Tan ◽  
Weixing Wang ◽  
Xin Li ◽  
Yunjie Guo
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Turbulent Boundary Layer ◽  
Spatiotemporal Resolution ◽  
Laser Scattering ◽  
Layer Interaction ◽  
Planar Laser ◽  
Boundary Layer Interaction ◽  
Flow Evolution ◽  
Visualisation Technique

Fractal features of the turbulent/non-turbulent interface (TNTI) in shock wave/turbulent boundary-layer interaction (SWBLI) flows are essential in understanding the physics of the SWBLI and the supersonic turbulent boundary layer, yet have received almost no attention previously. Accordingly, this study utilises a high spatiotemporal resolution visualisation technique, ice-cluster-based planar laser scattering (IC-PLS), to acquire the TNTI downstream of the reattachment in a SWBLI flow. Evolution of the fractal features of the TNTI in this SWBLI flow is analysed by comparing the parameters of the TNTI acquired in this study with those from a previous result (Zhuang et al.J. Fluid Mech., vol. 843, 2018a).

An experimental study of compressible turbulent mixing enhancement in swirling jets

1997 ◽  
Vol 330 ◽  
pp. 271-305 ◽  
Author(s):  
JONATHAN W. NAUGHTON ◽  
LOUIS N. CATTAFESTA III ◽  
GARY S. SETTLES
Keyword(s):  
Growth Rate ◽  
Turbulent Mixing ◽  
Mixing Layer ◽  
Layer Growth ◽  
Mixing Enhancement ◽  
Streamwise Vorticity ◽  
Laser Scattering ◽  
Swirling Jets ◽  
Swirling Jet ◽  
Planar Laser

Compressible jets with various amounts of swirl and compressibility are investigated experimentally. The mixing-layer growth rate is obtained from time-averaged images of the mixing layer using the planar laser scattering (PLS) technique, and the swirl is quantified with laser Doppler velocimetry and intrusive probes. The results conclusively demonstrate that the addition of swirl to the jet increases entrainment by up to 60% compared to a corresponding non-swirling case. Instantaneous PLS images reveal modified turbulent structure in the mixing layer of the swirling-jet cases. In particular, analysis of these images indicates that both the spatial extent and amplitude of the largest turbulent fluctuations are increased when swirl is added. Based upon these results, a parameter β that correlates the observed growth-rate enhancement is proposed. This parameter is derived assuming that the streamwise vorticity, generated in the mixing layer by the addition of small amounts of swirl, causes additional turbulent mixing that increases the growth rate. When the available growth-rate data for swirling jets are plotted against this parameter, they collapse to a single curve with increased enhancement for higher values of β. This result implies that the degree of enhancement actually increases with compressibility, although the dimensional growth rates for the present compressible swirling-jet cases are still less than those of their incompressible counterparts.

scholarly journals Investigations on the effect of different influencing factors on film cooling effectiveness under the injection of synthetic coolant

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jianlong Chang ◽  
Xinlei Duan ◽  
Yang Du ◽  
Baoquan Guo ◽  
Yutian Pan
Keyword(s):  
Film Cooling ◽  
Elliptical Hole ◽  
Synthetic Jet ◽  
Cooling Effect ◽  
Flow Structures ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Flow ◽  
Cooling Method ◽  
Strong Controllability

AbstractBy combining the synthetic jet and film cooling, the incident cooling flow is specially treated to find a better film cooling method. Numerical simulations of the synthetic coolant ejected are carried out for analyzing the cooling performance in detail, under different blowing ratios, hole patterns, Strouhal numbers, and various orders of incidence for the two rows of holes. By comparing the flow structures and the cooling effect corresponding to the synthetic coolant and the steady coolant fields, it is found that within the scope of the investigations, the best cooling effect can be obtained under the incident conditions of an elliptical hole with the aspect ratio of 0.618, the blow molding ratio of 2.5, and the Strouhal number St = 0.22. Due to the strong controllability of the synthetic coolant, the synthetic coolant can be controlled through adjusting the frequency of blowing and suction, so as to change the interaction between vortex structures for improving film cooling effect in turn. As a result, the synthetic coolant ejection is more advisable in certain conditions to achieve better outcomes.

Measurements of Residual Stress in the Layers of Thin Film Micro-Gas Sensors

2000 ◽  
Vol 657 ◽  
Author(s):  
Youngman Kim ◽  
Sung-Ho Choo
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Residual Stress ◽  
Gas Sensor ◽  
Gas Sensors ◽  
Micro Gas Sensor ◽  
Thin Film Layer ◽  
Film Layer ◽  
The Difference ◽  
Stress States

ABSTRACTThe mechanical properties of thin film materials are known to be different from those of bulk materials, which are generally overlooked in practice. The difference in mechanical properties can be misleading in the estimation of residual stress states in micro-gas sensors with multi-layer structures during manufacturing and in service.In this study the residual stress of each film layer in a micro-gas sensor was measured according to the five difference sets of film stacking structure used for the sensor. The Pt thin film layer was found to have the highest tensile residual stress, which may affect the reliability of the micro-gas sensor. For the Pt layer the changes in residual stress were measured as a function of processing variables and thermal cycling.

Large-scale structure and entrainment in the supersonic mixing layer

1995 ◽  
Vol 284 ◽  
pp. 171-216 ◽  
Author(s):  
N. T. Clemens ◽  
M. G. Mungal
Keyword(s):  
Mach Number ◽  
High Speed ◽  
Large Scale ◽  
Mixture Fraction ◽  
Mixing Layer ◽  
Mie Scattering ◽  
Planar Laser ◽  
The Cross ◽  
Convective Mach Number ◽  
Stream Direction

Experiments were conducted in a two-stream planar mixing layer at convective Mach numbers,Mc, of 0.28, 0.42, 0.50, 0.62 and 0.79. Planar laser Mie scattering (PLMS) from a condensed alcohol fog and planar laser-induced fluorescence (PLIF) of nitric oxide were used for flow visualization in the side, plan and end views. The PLIF signals were also used to characterize the turbulent mixture fraction fluctuations.Visualizations using PLMS indicate a transition in the turbulent structure from quasi-two-dimensionality at low convective Mach number, to more random three-dimensionality for$M_c\geqslant 0.62$. A transition is also observed in the core and braid regions of the spanwise rollers as the convective Mach number increases from 0.28 to 0.62. A change in the entrainment mechanism with increasing compressibility is also indicated by signal intensity profiles and perspective views of the PLMS and PLIF images. These show that atMc= 0.28 the instantaneous mixture fraction field typically exhibits a gradient in the streamwise direction, but is more uniform in the cross-stream direction. AtMc= 0.62 and 0.79, however, the mixture fraction field is more streamwise uniform and with a gradient in the cross-stream direction. This change in the composition of the structures is indicative of different entrainment motions at the different compressibility conditions. The statistical results are consistent with the qualitative observations and suggest that compressibility acts to reduce the magnitude of the mixture fraction fluctuations, particularly on the high-speed edge of the layer.

Modal Analysis of Inclined Jet Film Cooling Flows With Density Variation

2013 ◽  
Author(s):  
Prasad Kalghatgi ◽  
Sumanta Acharya
Keyword(s):  
Modal Analysis ◽  
Wall Temperature ◽  
Film Cooling ◽  
Free Stream ◽  
Density Ratio ◽  
Intermediate Frequency ◽  
Hydrodynamic Flow ◽  
Dynamic Mode Decomposition ◽  
Flow Structures ◽  
Dynamic Mode

Thermal and hydrodynamic flow field over a flat surface cooled with a single round inclined film cooling jet and fed by a plenum chamber is numerically investigated using Large Eddy Simulation (LES) and validated with published measurements. The calculations are done for a free stream Reynolds number Re = 16000, density ratio of coolant to free stream fluid ρj/ρ∞ = 2.0 and blowing ratio BR = ρjV/ρ∞V = 1.0. A short delivery tube with aspect ratio l/D = 1.75 and 35° inclination is considered. The evolution of the Kelvin-Helmholtz (K-H), hairpin and Counter-Rotating Vortex Pair (CVP) vortical structures are discussed to identify their origins. Modal analysis of the complete 3D flow and temperature field is carried out using a Dynamic Mode Decomposition (DMD) technique. The modal frequencies are identified, and the specific modal contribution towards the cooling wall temperature fluctuation is estimated on the film cooling wall. The low and intermediate frequency modes associated with streamwise and hairpin flow structures are found to have largest contribution (in-excess of 28%) towards wall temperature (or cooling effectiveness) fluctuations. The high frequency Kelvin-Helmholtz mode contributes towards initial mixing in the region of film cooling hole away from the wall. The individual modal temperature fluctuations on the wall and their corresponding hydrodynamic flow structures are presented and discussed.

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