Numerical Simulations of Gas-Centered Swirl-Coaxial Injectors for Rocket Engine Applications. Evaluating the ability of “standard” turbulence models in capturing the complex nature of spray atomization

2016 ◽  
Author(s):  
Larry A. Villasmil ◽  
Stephen Danczyk ◽  
Malissa Lightfoot ◽  
Stephen Shumaker ◽  
Ananda Himansu
Keyword(s):  
Numerical Simulations ◽  
Rocket Engine ◽  
Turbulence Models ◽  
Complex Nature ◽  
Spray Atomization

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

Numerical simulations of temperature fields in the uncooled nozzle of a short-range anti-aircraft rocket engine with an insert in the critical section made of various materials

2021 ◽  
Vol 70 (1) ◽  
pp. 15-30
Author(s):  
Mateusz Zieliński ◽  
Piotr Koniorczyk ◽  
Janusz Zmywaczyk ◽  
Marek Preiskorn
Keyword(s):  
Numerical Simulations ◽  
Cross Section ◽  
Heat Flux Density ◽  
Short Range ◽  
Rocket Engine ◽  
Transient Heat Conduction ◽  
Critical Section ◽  
Temperature Fields ◽  
Critical Cross Section ◽  
Calculation Results

Abstract. The paper presents numerical simulations of transient heat conduction in the uncooled nozzle of a short-range anti-aircraft rocket engine. The calculations were made for the configuration of the nozzle with an insert in the critical section made of various materials. The inserts used were: POCO graphite, Al2O3 ceramics, ZrO2-3Y2O3 ceramics. For comparison, numerical simulations of the heat transfer in a nozzle made entirely of St 45 steel, the melting point of which is 1700K, were also carried out. The engine's working time was in the order of 3 s. Numerical simulations were performed using the COMSOL program. The calculation results are given in the form of temperature dependence and heat flux density as a function of time in the critical cross-section. Keywords: non-cooled nozzle, rocket engine, temperature field

scholarly journals Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1663 ◽  
Author(s):  
Lei Jiang ◽  
Mingjun Diao ◽  
Haomiao Sun ◽  
Yu Ren
Keyword(s):  
Numerical Simulations ◽  
Discharge Coefficient ◽  
Separation Zone ◽  
Turbulence Models ◽  
Numerical Results ◽  
Upstream Face ◽  
Flow Conditions ◽  
Flow Features ◽  
The Mean ◽  
Absolute Percent Error

The objective of this study was to evaluate the effect of the upstream angle on flow over a trapezoidal broad-crested weir based on numerical simulations using the open-source toolbox OpenFOAM. Eight trapezoidal broad-crested weir configurations with different upstream face angles (θ = 10°, 15°, 22.5°, 30°, 45°, 60°, 75°, 90°) were investigated under free-flow conditions. The volume-of-fluid (VOF) method and two turbulence models (the standard k-ε model and the SST k-w model) were employed in the numerical simulations. The numerical results were compared with the experimental results obtained from published papers. The root mean square error (RMSE) and the mean absolute percent error (MAPE) were used to evaluate the accuracy of the numerical results. The statistical results show that RMSE and MAPE values of the standard k-ε model are 0.35–0.67% and 0.50–1.48%, respectively; the RMSE and MAPE values of the SST k-w model are 0.25–0.66% and 0.55–1.41%, respectively. Additionally, the effects of the upstream face angle on the flow features, including the discharge coefficient and the flow separation zone, were also discussed in the present study.

A Contribution to Study on the Lift of Ventilated Supercavitating Vehicle With Low Froude Number

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Yu Kaiping ◽  
Zhou Jingjun ◽  
Min Jingxin ◽  
Zhang Guang
Keyword(s):  
Numerical Simulations ◽  
Froude Number ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Gravitational Effect ◽  
Gas Leakage ◽  
Supercavitating Vehicle ◽  
Numerical Predictions ◽  
Low Froude Number

A ventilated cavity was investigated using three-dimensional numerical simulation and cavitation water tunnel experiments under the condition of low Froude number. A two-fluid multiphase flow model was adopted in numerical predictions. The drag between the different phases and gravitational effect, as well as the compressibility of gas, was considered in the numerical simulations. By comparing the ventilated coefficient computational results of three different turbulence models with the Epshtein formula, the shear-stress-transport turbulence model was finally employed. The phenomenon of double-vortex tube gas-leakage was observed in both numerical simulations and experiments. Based on the validity of the numerical method, the change law of the lift coefficient on the afterbody was given by numerical predictions and accorded well with experimental results. The cause for the appearance of an abrupt increase in lift was difficult to get from experiments for the hard measurement, whereas the numerical simulations provided some supplements to analyze the reasons. The distribution of lift coefficient on the afterbody had important significance to the design of underwater vehicles.

MISSILE VERTICAL LAUNCH SYSTEM WITH REACTION CONTROL JETS

2018 ◽  
Vol 145 (1) ◽  
pp. 25-46 ◽  
Author(s):  
Robert Głębocki ◽  
Mariusz Jacewicz
Keyword(s):  
Mathematical Model ◽  
Numerical Simulations ◽  
Fuel Consumption ◽  
Rocket Engine ◽  
Unsteady Aerodynamics ◽  
Aerodynamic Characteristics ◽  
Flight Path

The paper deals with a concept of a missile vertical launch system using reaction control jets. The purpose of the study was a detailed investigation of a method optimizing fuel consumption in the first phase of the missile flight to increase the range and optimize the flight path. In the designed system the missile is ejected vertically and turned to the desired position by using corrective engines before the sustainer motor is started. The dynamics and controllability of the missile at low velocities were studied. The physical and mathematical model of the object has been described, taking into account the nonlinearities connected with the dynamics of the rocket itself, the disturbances caused by firing the rocket engine as well as some effects the unsteady aerodynamics. A method identifying the aerodynamic characteristics of the missile and an algorithm controlling the correction engines is presented. A prepared mathematical model of the missile was used to create a simulating environment. The results of numerical simulations in the form of graphs and tables are presented.

Experimental and Numerical Analysis of the air Flow in T-Shape Channel Flow / Eksperymentalna i numeryczna analiza przepływu powietrza przez skrzyżowanie kanałów w kształcie litery T

2013 ◽  
Vol 58 (2) ◽  
pp. 333-348 ◽  
Author(s):  
Janusz Szmyd ◽  
Marian Branny ◽  
Michal Karch ◽  
Waldemar Wodziak ◽  
Marek Jaszczur ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Air Flow ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Laboratory Model ◽  
Image Velocimetry ◽  
Stereo Particle Image Velocimetry ◽  
Rsm Model ◽  
Calculated Velocity ◽  
Real Flow

This paper presents the results of experimental and numerical investigations of air flow through the crossing of a mining longwall and ventilation gallery. The object investigated consists of airways (headings) arranged in a T-shape. Maintained for technological purposes, the cave is exposed particularly to dangerous accumulations of methane. The laboratory model is a certain simplification of a real longwall and ventilation gallery crossing. Simplifications refer to both the object’s geometry and the air flow conditions. The aim of the research is to evaluate the accuracy with which numerical simulations model the real flow. Stereo Particle Image Velocimetry (SPIV) was used to measure all velocity vector components. Three turbulence models were tested: standard k-ε, k-ε realizable and the Reynolds Stress Model (RSM). The experimental results have been compared against the results of numerical simulations. Good agreement is achieved between all three turbulence model predictions and measurements in the inflow and outflow of the channel. Large differences between the measured and calculated velocity field occur in the cavity zone. Two models, the standard k-ε and k-ε realizable over-predict the measure value of the streamwise components of velocity. This causes the ventilation intensity to be overestimated in this domain. The RSM model underestimates the measure value of streamwise components of velocity and therefore artificially decreases the intensity of ventilation in this zone. The RSM model provides better predictions than the standard k-ε and k-ε realizable in the cavity zone.

Influence of Mesh Density and Turbulence Models on 2D Viscous Flutter in 11th Standard Configuration

2012 ◽  
Author(s):  
Aleksandra Pajak ◽  
Romuald Rzadkowski
Keyword(s):  
Large Deviations ◽  
Numerical Simulations ◽  
Qualitative Agreement ◽  
Phase Distribution ◽  
Turbulence Models ◽  
Experimental Results ◽  
Pressure Amplitude ◽  
Ansys Cfx ◽  
Mesh Density ◽  
Standard Configuration

In this study, numerical simulations of 2D viscous flutter were performed and compared with the available experimental results for different mesh density and different turbulence models. The calculations were carried out for bending oscillations of the cascade known as the Eleventh Standard Configuration. The ANSYS CFX v.12.1 code with SST, SA, k-ω turbulence models was used for calculations with various values of the inter-blade phase angle. Three moving H-O grids were used. Comparison of the calculated and the experimental results for the Eleventh Standard Configurations for the IBPA = 180 deg has shown good quantitative and qualitative agreement for local performances (unsteady pressure amplitude and phase distribution). For the IBPA = 90 and −90 deg the results are correct only in terms of amplitude. The phase distribution showed large deviations. The effect of various grids as well as SST, Spalart Allmaras and k-ω turbulence models was not significant in the subsonic case, but it turned out to be very noticeable in the transonic case.

Numerical investigations of vortex flows and vortex suppression schemes in a large pumping-station sump

2011 ◽  
Vol 225 (6) ◽  
pp. 1459-1480 ◽  
Author(s):  
X L Tang ◽  
F J Wang ◽  
Y J Li ◽  
G H Cong ◽  
X Y Shi ◽  
...  
Keyword(s):  
Free Surface ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Complex Nature ◽  
Stable Operation ◽  
Vortex Flows ◽  
Pumping Station ◽  
Pump Station ◽  
Pump Sump ◽  
Under Construction

This work uses a commercial computational fluid dynamics code to predict three-dimensional (3D) vortex flows in a large centrifugal-pump station under construction in China and proposes relevant vortex-eliminating schemes. Because of the complex nature of the vortex flows in sumps, different turbulence models, namely, standard k–ε, re-normalization group k–ε and realizable k–ε models, are first used to investigate their feasibility in predicting flows in a small physical model of an open pump sump, and various vortex streamlines and strength in the sump are predicted, analysed, and compared with the experimental data. The comparisons show that the realizable k–ε model predicts the position and strength of free-surface, sidewall-attached, and floor-attached vortices more accurately than the other two models. Then, the realizable k–ε model is used here to investigate 3D vortex flows in a large pumping-station sump. All the various vortices, such as free-surface, wall-attached vortices, are successfully predicted. Thus, based on the information of location, shape, size, and strength of the calculated vortices, three types of vortex-eliminating devices are proposed and their corresponding vortex suppression effects are analysed. These results will be used as reference for the safe and stable operation of the Hui–Nan–Zhuang pumping station in the future.

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