Influence of Exhaust Nozzle Geometry on the Jet Potential Core Development

2015 ◽  
Vol 811 ◽  
pp. 145-151 ◽  
Author(s):  
Daniel Eugeniu Crunteanu ◽  
Valentin Ionut Misirliu ◽  
Oana Dumitrescu ◽  
Bogdan Gherman
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Boundary Conditions ◽  
Turbulence Model ◽  
Nozzle Geometry ◽  
Turbofan Engine ◽  
Potential Core ◽  
The Third ◽  
The Impact

In this paper, a numerical simulation was performed on a scale turbofan engine nozzle to asses the influence of two nozzle configurations over the flow performance while the nozzle is situated at a certain distance from the ground. The turbulence model chosen for this numerical simulation was SST k-ω to capture boundary layer detachment and jet attachment to the ground. For this analysis two different computational domains where considered, while for the third case, boundary conditions for secondary inlet where modified. To assess the impact of these geometry changes a comparison between cases is made at different location in the domain.

The Impact of Viscous Effects on the Aerodynamic Damping of Vibrating Transonic Compressor Blades—A Numerical Study

2000 ◽  
Vol 123 (2) ◽  
pp. 409-417 ◽  
Author(s):  
Bjo¨rn Gru¨ber ◽  
Volker Carstens
Keyword(s):  
Boundary Layer ◽  
Turbulence Model ◽  
Navier Stokes ◽  
Implicit Time ◽  
Compressor Cascade ◽  
Viscous Effects ◽  
Aerodynamic Forces ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
The Impact

A parametric study which investigates the influence of viscous effects on the damping behavior of vibrating compressor cascades is presented here. To demonstrate the dependence of unsteady aerodynamic forces on the flow viscosity, a computational study was performed for a transonic compressor cascade of which the blades underwent tuned pitching oscillations while the flow conditions extended from fully subsonic to highly transonic flow. Additionally, the reduced frequency and Reynolds number were varied. In order to check the linear behavior of the aerodynamic forces, all calculations were carried out for three different oscillation amplitudes. Comparisons with inviscid Euler results helped identify the influence of viscous effects. The computations were performed with a Navier-Stokes code, the basic features of which are the use of an AUSM upwind scheme, an implicit time integration, and the implementation of the Baldwin-Lomax turbulence model. In order to demonstrate the possibility of this code to correctly predict the unsteady behavior of strong shock-boundary layer interactions, the experiment of Yamamoto and Tanida on a self-induced shock oscillation due to shock-boundary layer interaction was calculated. A significant improvement in the prediction of the shock amplitude was achieved by a slight modification of the Baldwin Lomax turbulence model. An important result of the presented compressor cascade investigations is that viscous effects may cause a significant change in the aerodynamic damping. This behavior is demonstrated by two cases in which an Euler calculation predicts a damped oscillation whereas a Navier-Stokes computation leads to an excited vibration. It was found that the reason for these contrary results are shock-boundary-layer interactions which dramatically change the aerodynamic damping.

Study on the Downburst Field Characteristics under the Influence of Two-Dimensional Continuous Mountains at Different Distance

2014 ◽  
Vol 580-583 ◽  
pp. 3111-3114
Author(s):  
Yi Sun ◽  
Yuan Ze Wu ◽  
Hai Tao Shi ◽  
Bai Feng Ji
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Wind Field ◽  
Strong Wind ◽  
Two Dimensional ◽  
Field Characteristic ◽  
Main Factors ◽  
Cfd Numerical Simulation ◽  
The Impact

Downburst is an outburst strong wind on or near the ground, and its wind field characteristics are significantly different from boundary layer winds. Continuous mountains at different distance are one of the main factors for the influence of downburst wind field characteristic. In this thesis, the changes of the wind field characteristics under the influence of continuous mountains at different distance after the downburst happened are studied by CFD numerical simulation. The impact of downburst is analysed and summarized through the charts.

scholarly journals Research on Flow and Temperature Fields in Aircraft Engines

2014 ◽  
Vol 8 (1) ◽  
pp. 731-738 ◽  
Author(s):  
Guochang Zhao ◽  
Daniel X. Zhao ◽  
Jing Li ◽  
Xia Du ◽  
Xianyi Tong ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Boundary Conditions ◽  
Analytical Solutions ◽  
Temperature Fields ◽  
Dimensionless Temperature ◽  
Wedge Flow ◽  
Dimensionless Velocity ◽  
Temperature Distributions ◽  
Wall Boundary Conditions

The similarity criteria which ensure the similarity between flow and temperature fields of both the lowtemperature turbine cavity model and the actual high-temperature turbine cavity are derived and then verified using numerical simulation of two different sized rotor-stator system turbine cavities. The analytical solution of threedimensional dimensionless velocity distribution and the numerical solutions of both the three-dimensional dimensionless velocity and temperature distributions of the free disk flow field are obtained. Using these solutions as a foundation, the analytical solutions of the dimensionless temperature distribution within the boundary layer of the isothermal and nonisothermal free disk model are obtained. The numerical and analytical solutions of velocity and temperature are compared to ensure that the solutions are consistent with each other. The analytical solutions of the dimensionless velocity and temperature fields within the laminar boundary layer of the wedge flow are obtained. The approximation solutions of the dimensionless temperature of the wedge flow under subsonic speed and isothermal wall boundary conditions and the dimensionless temperature of the wedge flow under supersonic speed and adiabatic wall boundary conditions are provided. The velocity and temperature distributions of the airflow outside the strut are obtained through numerical simulation and the pattern of changes in the velocity and temperature within the laminar boundary layer of the strut is revealed. Numerical simulation on gas jet cooling and regenerative cooling for the strut are simulated and shown to be effective for thermal protection. Using a strut with rough internal surface and aviation kerosene as the cooling medium is effective at cooling. The experiment fixture used to simulate the outlet temperature of the combustor and the experimental fixture used to simulate the dynamic temperature of the compressor are designed and built. The dynamic temperature of the compressor airflow is measured using combined thermocouples. Experimental results show that the dynamic error caused by the thermal inertia of the thermocouple can be eliminated by the compensation algorithm.

Study on Vertical Earth Pressure of Slab Culvert under High Embankment

2012 ◽  
Vol 256-259 ◽  
pp. 1898-1902 ◽  
Author(s):  
Bao Kuan Ning ◽  
He Fan ◽  
Lei Gong ◽  
Guo Qing Liu
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Field Test ◽  
Structural Design ◽  
Earth Pressure ◽  
Test Results ◽  
Soil Pressure ◽  
Vertical Earth Pressure ◽  
The Impact ◽  
Good Agreement

With the increasing of embankment culvert engineering applications, there has been due in part to the structural design is too conservative and not economic or select unreasonable structural form, leading to the phenomenon of cracking or even collapse of the culvert structure, and the phenomenon has seriously affected the normal use of the highway. In this paper, the numerical simulation of vertical earth pressure distribution on different structural forms of embankment on culverts, to discuss the impact of boundary conditions, fill height, the thickness of the culvert culverts vertical earth pressure. Combined with Heda highway a culvert covert field test results and numerical simulation results were compared and analyzed. The results show that the numerical simulation and field test results in good agreement with the culvert structure in the form of vertical earth pressure of the embankment culverts have a greater impact; the structure of different forms of the culvert in the upper soil pressure is significantly different. In addition, analysis of the impact of boundary conditions, filling height of culvert vertical earth pressure values. The results can reference for the study of the structural design of the embankment culverts security.

scholarly journals Selecting a k-ε turbulence model for investigating n-decane combustion in a diesel engine combustion chamber

2019 ◽  
Vol 7 (2) ◽  
pp. 80-87
Author(s):  
Andrii Avramenko
Keyword(s):  
Numerical Simulation ◽  
Diesel Engine ◽  
Combustion Chamber ◽  
Turbulent Flows ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Toxic Substances ◽  
Engine Combustion ◽  
Experimental Findings ◽  
The Impact

The results of a comparative numerical simulation of combustion and formation of toxic substances in a diesel engine combustion chamber are given. Experimental findings were used to identify the mathematical models. The impact of the standard, RNG and realizable k-ε turbulence models on the accuracy of numerical simulation of combustion and the formation of toxic substances was studied. The realizable k-ε turbulence model was shown to provide a closer agreement of computational and experimental data during simulation of the diesel engine process when turbulent flows are described.

scholarly journals Impact of Improved Mellor–Yamada Turbulence Model on Tropical Cyclone-Induced Vertical Mixing in the Oceanic Boundary Layer

2020 ◽  
Vol 8 (7) ◽  
pp. 497
Author(s):  
Taekyun Kim ◽  
Jae-Hong Moon
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Turbulence Model ◽  
Mixed Layer ◽  
General Circulation ◽  
Vertical Mixing ◽  
Circulation Model ◽  
Sea Surface ◽  
Oceanic Boundary Layer ◽  
The Impact

It has been identified that there are several limitations in the Mellor–Yamada (MY) turbulence model applied to the atmospheric mixed layer, and Nakanishi and Niino proposed an improved MY model using a database for large-eddy simulations. The improved MY model (Mellor–Yamada–Nakanishi–Niino model; MYNN model) is popular in atmospheric applications; however, it is rarely used in oceanic applications. In this study, the MY model and the MYNN model are compared to identify the efficiency of the MYNN model incorporated into an ocean general circulation model. To investigate the impact of the improved MY model on the vertical mixing in the oceanic boundary layer, the response of the East/Japan Sea to Typhoon Maemi in 2003 was simulated. After the typhoon event, the sea surface temperature obtained from the MYNN model showed better agreement with the satellite measurements than those obtained from the MY model. The MY model produced an extremely shallow mixed layer, and consequently, the surface temperatures were excessively warm. Furthermore, the near-inertial component of the velocity simulated using the MY model was larger than that simulated using the MYNN model at the surface layer. However, in the MYNN model, the near-inertial waves became larger than those simulated by the MY model at all depths except the surface layer. Comparatively, the MYNN model showed enhanced vertical propagation of the near-inertial activity from the mixed layer into the deep ocean, which results in a temperature decrease at the sea surface and a deepening of the mixed layer.

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