Heat alleviation studies on hypersonic re-entry vehicles

2018 ◽  
Vol 122 (1257) ◽  
pp. 1673-1696 ◽  
Author(s):  
M. Khalid ◽  
K. A. Juhany
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Flow Field ◽  
Hypersonic Flow ◽  
Flow Rate ◽  
Leading Edge ◽  
Control Surface ◽  
Solid Boundary ◽  
Simulation Techniques ◽  
Hypersonic Speeds

ABSTRACTA numerical simulation has been carried out to investigate the effects of leading edge blowing upon heat alleviation on the surface of hypersonic vehicles. The initial phase of this work deals with the ability of the present CFD-based techniques to solve hypersonic flow field past blunt-nosed vehicles at hypersonic speeds. Towards this end, the authors selected three re-entry vehicles with published flow field data against which the present computed results could be measured. With increasing confidence on the numerical simulation techniques to accurately resolve the hypersonic flow, the boundary condition at the solid blunt surface was then equipped with the ability to blow the flow out of the solid boundary at a rate of at least 0.01–0.1 times the free stream (ρ∞u∞) mass flow rate. The numerical iterative procedure was then progressed until the flow at the surface matched this new ‘inviscid like’ boundary condition. The actual matching of the flow field at the ejection control surface was achieved by iterating the flow on the adjacent cells until the flow conformed to the conditions prescribed at the control surface. The conditions at the surface could be submitted as a ρ∞u∞at the surface or could be equipped as a simple static pressure condition providing the desired flow rate. The comparison between the present engineering approach and the experimental data presented in this study demonstrate its ability to solve complex problems in hypersonic.

Numerical Simulation of Flow Field Dynamics Characteristics for One Novel Twin-Screw Kneader

2012 ◽  
Vol 271-272 ◽  
pp. 1049-1055
Author(s):  
Jing Wei ◽  
Xin Long Liang ◽  
Wei Sun ◽  
Li Cun Wang
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Flow Field ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Maximum Shear Stress ◽  
Twin Screw ◽  
Screw Rotors ◽  
Center Distance

The numerical simulation for dynamic characteristics of the flow field of a novel twin-screw kneader is carried out. The flow field model of the twin-screw kneader is established, and the three-dimensional, isothermal and steady numerical analysis of non-Newtonian fluid is presented based on computational fluid dynamics (CFD) theory, and the characteristics under the conditions of different speeds and center distances such as the distribution of pressure and velocity field, the maximum shear stress, the mass flow rate and so on, are studied. The research results show that: with increasing speed, the maximum flow pressure, the mass flow rate, the maximum shear stress will increase; the maximum shear stress increases first and then decreases with increasing of center distance of the screw rotors, while the mass flow rate increases with increasing of center distance; but when the center distance reaches a certain degree, the mass flow rate will be negative and the material will appear serious reflux which can lead the kneader to stopping working.

scholarly journals Numerical and experimental investigation of the pressure fluctuation in a mixed-flow pump under low flow conditions

2019 ◽  
Vol 234 (1) ◽  
pp. 46-57 ◽  
Author(s):  
Xi Shen ◽  
Desheng Zhang ◽  
Bin Xu ◽  
Ruijie Zhao ◽  
Yongxin Jin ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Flow Separation ◽  
Pressure Fluctuation ◽  
Static Pressure ◽  
Leading Edge ◽  
Low Flow ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Flow Pump

In this paper, the large eddy simulation is utilized to simulate the flow field in a mixed-flow pump based on the standard Smagorinsky subgrid scale model, which is combined with the experiments to investigate pressure fluctuations under low flow conditions. The experimental results indicated that the amplitude of fluctuation at the impeller inlet is the highest, and increases with the reduction of the flow rate. The main frequencies of pressure fluctuation at the impeller inlet, impeller outlet, and vane inlet are blades passing frequency, while the main frequency at the vane outlet changes with the flow rate. The results of the simulation showed that the axial plane velocity at impeller inlet undergoes little change under 0.8 Qopt. In case of 0.4 Qopt, however, the flow field at impeller inlet becomes complicated with the axial plane velocity changing significantly. The flow separation is generated at the leading edge of the suction surface at t* = 0.0416 under 0.4 Qopt, which is caused by the increase of the incidence angle and the influence of the tip leakage flow. When the impeller rotates from t* = 0.0416 to t* = 0.1249, the flow separation intensified and the swirling strength of the separation vortex is gradually increased, leading to the reduction of the static pressure, the rise of adverse pressure gradient, and the generation of backflow. The static pressure at the leading edge of the impeller recovers gradually until the backflow is reached. In addition, the flow separation is the main reason for the intensification of the pressure fluctuation.

Numerical analysis of exhaust jet secondary combustion in hypersonic flow field

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840045
Author(s):  
Tian-Peng Yang ◽  
Jiang-Feng Wang ◽  
Fa-Ming Zhao ◽  
Xiao-Feng Fan ◽  
Yu-Han Wang
Keyword(s):  
Flow Field ◽  
Hypersonic Flow ◽  
Flight Control ◽  
Stokes Equations ◽  
Field Structure ◽  
Control Surface ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Secondary Combustion ◽  
Exhaust Jet

The interaction effect between jet and control surface in supersonic and hypersonic flow is one of the key problems for advanced flight control system. The flow properties of exhaust jet secondary combustion in a hypersonic compression ramp flow field were studied numerically by solving the Navier–Stokes equations with multi-species and combustion reaction effects. The analysis was focused on the flow field structure and the force amplification factor under different jet conditions. Numerical results show that a series of different secondary combustion makes the flow field structure change regularly, and the temperature increases rapidly near the jet exit.

scholarly journals Numerical Simulation of Full-Scale Three-Dimensional Fluid Flow in an Oscillating Reactor

2021 ◽  
Vol 9 ◽  
Author(s):  
Houjun Gong ◽  
Mengqi Wu
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Flow Field ◽  
Flow Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Full Scale ◽  
Variation Patterns ◽  
Oscillating Motion ◽  
Resistance Coefficients

Marine reactors are subjected to additional motions due to ocean conditions. These additional motions will cause large fluctuation of flow rate and change the coolant flow field, making the system unstable. Therefore, in order to understand the effect of oscillating motion on the flow characteristics, a numerical simulation of fluid flow is carried out based on a full-scale three-dimensional oscillating marine reactor. In this study, the resistance coefficients of the lattice, rod buddle and steam generator are fitted, and the distribution of flow rate, velocity as well as pressure in different regions is investigated through the standard model. After additional oscillation is introduced, the flow field in an oscillating reactor is presented and the effect of oscillating angle and elevation on the flow rate is investigated. Results show that the oscillating motion can greatly change the flow field in the reactor; most of the coolant circulates in the downcommer and lower head with only a small amount of coolant entering the core; the flow fluctuation period is consistent with the oscillating period, and the flow variation patterns under different oscillating conditions are basically the same; since the flow amplitude is related to oscillating speed, the amplitude of flow rate rises when decreasing the maximum oscillating angle; the oscillating elevation has little effect on the flow rate.

Computation of an Unsteady Orifice Flow in a Circular Pipe From Wall Pressure Measurements Based on Measurement-Integrated Simulation Using a Turbulent Model

2010 ◽  
Author(s):  
Mitsuhiro Nakao ◽  
Kenji Kawashima ◽  
Toshiharu Kagawa
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Flow Rate ◽  
Experimental Measurement ◽  
Pressure Measurement ◽  
Estimation Error ◽  
Wall Pressure ◽  
Turbulent Model ◽  
Actual Case ◽  
Combination Methods

Visualizing the state of real turbulent flow is important in many applications such as safe operation and fault diagnosis in plant or pipeline. Two approaches to this purpose exist: experimental measurement and numerical simulation. In experimental measurement, reliability of the result at measured point is easy to evaluate. However, information of the whole flow field is difficult to obtain. On the other hand, numerical simulation easily obtains any information of the flow field. However, the reliability of the result strongly depends on the numerical model and boundary condition and/or the initial condition. In general, the more precise results are needed, the heavier computation load we spend. None of these approaches is superior, and combination methods of them are subjected to extensive research. Above all, we particularly paid attention to measurement-integrated (MI) simulation proposed by Hayase et al. MI simulation can expect to reduce computational load. We have applied MI simulation to unsteady oscillatory airflows passing through an orifice. In our previous study, a standard k-ε model was used for MI simulation. Estimation error remained due to inadequate consideration of the feedback law. In our latest study, the feedback law was decided considering an effect of computation grid on CFD of contracted flow. As a result, wall pressures near the orifice plate and axial velocities on vena contracta estimated with MI simulation showed good agreement with that of measurement. In the present paper, we deal with visualization of unsteady oscillatory airflows passing through an orifice from wall pressure measurement based on MI simulation using a turbulent model. The former studies have used measured inlet flow rate which is unknown in many actual case. Compared with the flow rate measurement, wall pressure measurement is simple. Therefore, we consider MI simulation using only wall pressure are of practical use. The developed MI simulation was performed with unsteady flow rate with the frequency up to 10 Hz. Computation results obtained with the developed MI simulation using coarse computation grid is compared with experimental results. It is confirmed that flow field obtained with the developed MI simulation is close to that of experiment.

scholarly journals The numerical simulation techniques research and preliminary experimental validation of the start characteristics for a two-dimensional hypersonic inlet

2019 ◽  
Author(s):  
A. Yu ◽  
D. Yang ◽  
J. Wu ◽  
H. Ni ◽  
J. Le
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Flow Field ◽  
Experimental Validation ◽  
Incoming Flow ◽  
Two Dimensional ◽  
Numerical Techniques ◽  
Simulation Techniques ◽  
Hypersonic Inlet ◽  
Mach Numbers

The paper presents the research of the numerical simulation techniques and the preliminary experimental validation on the start characteristics for a typical two-dimensional (2D) hypersonic inlet. In order to obtain the start and unstart hysteresis loop, numerical simulations methods using the incoming flow field, the zero-velocity flow field, and the latest convergent flow field as the initialized flow field separately are adopted to calculate the inlet start characteristics until the flow fields converge. The calculation software is AHL3D, a parallel computational fluid software self-developed by CARDC. The numerical methods also include the method from unstart flow field to start one with Mach-numbers gradually increasing till the inlet is start and the method from start flow field to unstart one with Mach-numbers decreasing till the inlet is unstart. According to the comparison with different initialized flow field and with different step-size of Mach-number, the inlet start characteristics are obtained and the numerical techniques are analyzed. Based on the comparison and the analysis, it is suggested that the numerical techniques of inlet start characteristics should use the zero-initialized flow field with one step to the final Mach-numbers to predict the minimal self-start Mach-number of the inlet and use the incoming flow-initialized flow field to predict the minimum start Mach-number. The results show that the numerical techniques are high-efficient and easily operational. To verify the effect of the numerical techniques, wind tunnel tests are arranged to research the start characteristics of a typical 2D hypersonic inlet. The preliminary experimental result shows that the numerical techniques of predicting inlet start characteristics are consistent with the experiments very well, which means that the application of the numerical techniques can be further carried out for such hypersonic inlets as mentioned in the current paper.

Numerical Simulation of Quenchant Flow Characteristics in Large Quench Tank

2012 ◽  
Vol 271-272 ◽  
pp. 1372-1376
Author(s):  
Hui Sun
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Flow Field ◽  
Flow Rate ◽  
Inner Core ◽  
Flow Characteristics ◽  
Structure Design ◽  
Inner Surface ◽  
Computational Fluid Dynamics Cfd

The computational fluid dynamics (CFD) technique is employed to predict the flow of quenchant in a large quench tank. The characteristics of flow field in the existing quench tank are investigated, and the major deficiency occurred in the tank structure design is analyzed. Two different schemes for improving the tank structure design are brought forward, and further numerical simulations are carried out. Results show that the non-uniform flow field is generated throughout the quenching zone in the existing large quench tank. There is clear difference in flow rate in the regions near the inner surface of workpiece and the outer, which may cause the workpiece distortion and even cracking. Reduction in ring pipe intermediate diameter can not obviously enhance the uniformity of flow field in the quench tank. By adding an inner core in the center zone of the tank, the flow rate in the region near the inner surface of workpiece can be increased effectively, and the flow rate difference found in the quenching zone reduced significantly, which are beneficial to guarantee the quenching quality of workpiece.

Numerical Study on Structural Improvement of the Grill Fixed at the Outlet of the Air Conditioner Outdoor Unit

2011 ◽  
Vol 141 ◽  
pp. 386-391 ◽  
Author(s):  
Ying Liu ◽  
C.J. Wu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Flow Rate ◽  
Numerical Study ◽  
Structural Parameters ◽  
Turbulent Intensity ◽  
Air Conditioner ◽  
Increase Flow Rate ◽  
Structural Improvement ◽  
Field Information

This paper presents the techniques to numerically simulate the inner flow field of the air conditioner outdoor unit with Fluent. The results are verified experimentally and proved to be mesh-independent. The possibility of improvement to increase the flow rate by modifying the grill’s structural parameters is shown through analyzing the numerical results. The gill’s structure is improved using the flow field information got from numerical simulation and the improvement helps to increase flow rate by 4.1% and reduces the turbulent intensity near the grill significantly.

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