scholarly journals Numerical Investigation of the Shock Train in a Scramjet with the Effects of Back-Pressure and Divergent Angles

2020 ◽  
Author(s):  
Santhosh Kumar Gugulothu ◽  
B. Bhaskar ◽  
V.V. Phani Babu
Keyword(s):  
Shock Wave ◽  
Transport Model ◽  
Wave Train ◽  
Leading Edge ◽  
Single Step ◽  
Back Pressure ◽  
Divergence Angle ◽  
Shock Train ◽  
Navier Stokes Equation ◽  
Ansys Fluent

Numerical simulations are carried out to study the effect of divergence angle and adverse pressure gradient on the movement of shock wave train in a scramjet isolator. The commercial software tool ANSYS Fluent 16 was used to simplify two dimensional Reynolds averaged Navier Stokes equation with compressible fluid flow by considering the density-based solver with standard K-ε turbulence model. The species transport model with single step volumetric reaction mechanism is employed. Initially, the simulated results are validated with experimental results available in open literature. The obtained results show that the variation of the divergence angle and back pressure on the scramjet isolator has greater significance on the flow field. Also, with an increase in the back pressure, due to the intense turbulent combustion, the shock wave train developed should expand along the length and also moves towards the leading edge of the isolator leading to rapid rise in the pressure so that the pressure at the entrance of the isolator can match the enhanced back pressures.

Three-Dimensional Passive and Active Control Methods of Shock Wave Train Physics in a Duct

2016 ◽  
Vol 08 (04) ◽  
pp. 1650047 ◽  
Author(s):  
Reza Kamali ◽  
Seyed Mahmood Mousavi ◽  
Danial Khojasteh
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
High Performance ◽  
Wave Train ◽  
Three Dimensional ◽  
Maximum Flow ◽  
Control Methods ◽  
Shock Train ◽  
Ansys Fluent ◽  
Starting Point

In the present work, the physics of a three-dimensional shock train in a convergent-divergent nozzle is numerically investigated. In this regards, the Ansys-Fluent Software with Algebraic Wall-Modeled Large-Eddy Simulation (WMLES) is used. To estimate precision and errors accumulation we used the Smirinov’s method; fine flow structures are obtained via Laplacian of density called shadowgraph and the shock parameter is defined as multiplication of flow Mach number by the normalized pressure gradient, in which shock wave structures are visible distinctly. The results are compared with the experimental data of Weiss et al. [Experiments in Fluids 49(2) (2010) 355–365], in the same conditions including geometry, boundary conditions, etc. The results show that there is good agreement with experimental trends concerning wall pressure and centerline Mach number profiles. Therefore, the focus of the present study is an assessment of various flow control methods to change the shock structures. Consequently, we investigated the effects of passive (bump and cavity) and active (suction and blowing) control methods on the starting point of shock, shock strength, minimum pressure, maximum flow Mach number, etc. All CFD investigations are carried out by High Performance Computing Center (HPCC).

Numerical Study on Control of Sunroof Buffeting

2021 ◽  
Vol 13 (2) ◽  
Author(s):  
K. Vijaykumar ◽  
S. Poonkodi ◽  
A.T. Sriram
Keyword(s):  
Numerical Study ◽  
Leading Edge ◽  
Dominant Frequency ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Flow Modification ◽  
Numerical Result ◽  
Modification Technique ◽  
Commercial Solver

Sunroof has become one of the essential features of a luxury car, and it provides natural air circulation and good illumination into the car. But the primary problem associated with it is the buffeting noise which causes discomfort to the passengers. Though adequate studies were carried out on sunroof buffeting, efficient control techniques are needed to be developed from fundamental mechanism. To reduce the buffeting noise, flow modifications at the entrance of the sunroof is considered in this study. The internal portion of the car with sunroof is simplified into a shear driven open cavity, and two-dimensional numerical simulations are carried out using commercial solver, ANSYS Fluent. Reynolds averaged Navier-Stokes equation is used with the realizable k-? turbulence model. The unsteady numerical result obtained in this study is validated with the available experimental results for the dominant frequency. The prediction is good agreement with experiment. Flow modification technique is proposed to control the sunroof buffeting by implementing geometric modifications. A hump has been placed near the leading edge of the cavity which resulted in significant reduction of pressure oscillations. Parametric studies have been performed by varying the height of hump and the distance of hump from the leading edge. There is no prominent difference when the height of the hump is varied. As the distance of the hump from the leading edge is reduced, the sound pressure level decreases.

Optimization of Aerodynamic Parameters of Cropped Delta Wing with Fence at Sonic Mach Number

2019 ◽  
Vol 16 (2) ◽  
pp. 403-409
Author(s):  
M. P. Arun ◽  
M. Satheesh ◽  
Edwin Raja J. Dhas
Keyword(s):  
Shock Wave ◽  
Boundary Condition ◽  
Mach Number ◽  
Sound Speed ◽  
Delta Wing ◽  
Leading Edge ◽  
Supersonic Speed ◽  
Sweep Angle ◽  
Ansys Fluent ◽  
Aerodynamic Parameters

Manufacturing and maintaining different aircraft fleet leads to various purposes, which consumes more money as well as man power. Solution to this, nations that are leading in the field of aeronautics are performing much research and development works on new aircraft designs that could do the operations those were done by varied aircrafts. The foremost benefit of this delta wing is, along the huge rearward sweep angle, the wing’s leading edge would not contact the boundary of shock wave. Further, the boundary is produced at the fuselage nose due to the speed of aircraft approaches and also goes beyond the transonic to supersonic speed. Further, rearward sweep angle greatly worse the airspeed: wings under normal condition to leading edge, so permits the aircraft to fly at great transonic, subsonic, or supersonic speed, whereas the over wing speed is kept to minimal range than that of the sound speed. The cropped delta wing with fence has analysed in three cases: Fences at 3/4th distance from the centre, with fences at half distance from the centre and with fences at the centre. Further, the delta wing that cropped is exported to ANSYS FLUENT V14.0 software and analysed by making the boundary condition settings like sonic Mach number of flow over wing along with the angle of attack.

Numerical investigation on implication of innovative hydrogen strut injector on performance and combustion characteristics in a scramjet combustor

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sribhashyam Krishna Kireeti ◽  
Gadepalli Ravikiran Sastry ◽  
Santosh Kumar Gugulothu
Keyword(s):  
Transport Model ◽  
Weight Ratio ◽  
Combustion Efficiency ◽  
Navier Stokes ◽  
Mixing Efficiency ◽  
Injection Technique ◽  
Mixing Rate ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Scramjet Combustor

Abstract A detailed numerical analysis on a scramjet combustor is carried out by introducing an innovative shaped strut in place of the conventional strut. The design of newly added strut aids in generating intense vorticity which helps in efficient mixing of fuel and oxidizer. The air from the isolator enters the combustor at Mach 2.0, whereas fuel enters from the trailing edge of the strut sonically. In this study the flow dynamics with finite volume approach on commercial software Ansys-Fluent 20.0 to solve the two-dimensional Reynolds average Navier Stokes equation (RANS) with compressible fluid flow by considering the density-based solver with SST k-ε turbulent model. The species transport model with volumetric reaction and finite rate/eddy dissipation turbulence chemistry interaction is adopted to study the combustion phenomena and validated with the experimental results, and it is found that the interaction of the shear shock layer enhances the mixing rate by intensifying turbulence. The modified strut injector’s mixing efficiency is compared to the base strut and observed that with a 40% reduction in length, the modified strut injection technique exhibited a mixing efficiency of >95%. The combustion efficiency is then estimated streamwise, and the plot follows the same pattern as the mixing efficiency with fuel burns down completely when x = 150 mm for the modified strut whereas x = 200 mm for the base strut. This can compact the combustion chamber and increases the thrust-to-weight ratio. So, the innovative strut adopted can improvise the combustion efficiency.

Influence of innovative hydrogen multi strut injector with different spacing on cavity-based scramjet combustor

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Sribhashyam K. Kireeti ◽  
Ravikiran Sastry Gadepalli ◽  
Santhosh K. Gugulothu
Keyword(s):  
Recirculation Zone ◽  
Transport Model ◽  
Combustion Efficiency ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Scramjet Combustor ◽  
Separation Layers ◽  
Finite Volume Approach ◽  
And Performance

Abstract In this study, the flow dynamics with finite volume approach on commercial software Ansys-Fluent 20.0 to solve the compressible two-dimensional fluid flow with Reynolds Average Navier Stokes equation (RANS) equation by considering the density-based solver with Shaer stress transport model (SST) k- ω turbulent model. The species transport model with volumetric reaction and finite rate/eddy dissipation turbulence chemistry interaction is adopted to study the combustion phenomena. Additionally, the effect of spacing between the struts on the flow characters and performance of the combustor is studied by increasing the spacing of struts from 1 mm to 4 mm for each increment of 1 mm. It is found that the multi strut improves the mixing and combustion efficiency compared with that of the single strut owing to the formation of a significant separation layer, resulting in multiple shocks, vortices, and a larger recirculation zone. However, when the spacing of struts is increased further, the performance of the combustor is found to be deteriorating owing to the formation of larger separation layers. The recirculation zone is significant when the strut spacing is minimal and shrinks and restricts itself within the cavity when spacing is increased. So, for better performance of combustor, multi strut with minimum spacing is preferable.

scholarly journals Simulation of Back Pressure Effect on Behaviour of Convergent Divergent Nozzle

2013 ◽  
Vol 6 (1) ◽  
pp. 105-120
Author(s):  
Nazar Muneam Mahmood
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Gas Flow ◽  
Static Pressure ◽  
Flow Region ◽  
Back Pressure ◽  
Cross Sectional ◽  
Ansys Fluent ◽  
One Dimensional ◽  
Velocity Magnitude

In this research a simulation of steady flow of a gas through a convergent divergent nozzle which has a varying cross sectional area will be considered. The nature of the flow can be explained by considering how the flow and its characteristics in the nozzle changes as nthe back pressure Pb is decreased.The characteristics of gas flow i.e.(Mach number, static pressure, density, velocity magnitude and static temperature) distributions for the convergent divergent nozzle are implemented by using the ANSYS Fluent 12.1 software to solve the quasi-one dimensional nozzle flow.The reductions in the back pressure cannot affect conditions upstream of the throat. The nozzle is, therefore, choked. The shock wave increases the pressure, density and temperature and reduces the velocity and Mach number to a subsonic value, and as back pressure is further reduced to a certain value, the extent of the supersonic flow region increases, the shock wave moving further down the divergent portion of the nozzle towards the exit plane.

Numerical Research on Flow Characteristics of Inlet Flow-Path for Ram-Rotor

2012 ◽  
Author(s):  
Weijia Kang ◽  
Zhansheng Liu ◽  
Zhixuan Cao ◽  
Le Wang ◽  
Gangwei Wang
Keyword(s):  
Shock Wave ◽  
Rotational Speed ◽  
Design Method ◽  
Pressure Ratio ◽  
Flow Path ◽  
Back Pressure ◽  
Shock Train ◽  
Constant Length ◽  
Compression Efficiency ◽  
Inlet Flow

A design method of ram-rotor inlet flow-path with shock wave compression is proposed with consideration of shock wave angle, plane turning angle, the inlet flow-path throat, and subsonic diffuser. A 3D model of the inlet flow path for ram-rotor is established by applying this design method. Effects of the back pressure, rotational speed and flow-path structure on the structure of shock wave and flow-path field distribution are numerically analyzed. The simulation results indicate that the inlet compression efficiency and thermal efficiency of rotating ramjet engine are improved with the increment of exit back pressure when the inlet flow-path operates normally. But along with the increase of rotational speed, the change trends of pressure ratio and compression efficiency are opposite. Reasonable compromise is needed in improving the rotating speed of ram-rotor. In addition, the constant length should also be guaranteed in the throat of inlet flow-path, where a relatively stable shock train forms.

scholarly journals Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4168
Author(s):  
Botao Zhang ◽  
Xiaochen Mao ◽  
Xiaoxiong Wu ◽  
Bo Liu
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Axial Flow ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Transonic Compressor

To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the investigated varied range, when the rotor tip clearance size is half of the design, the compressor performance is improved best, and the peak efficiency and stall margin are increased by 0.2% and 3.5%, respectively.

Self-Acceleration in the Parameterization of Orographic Gravity Wave Drag

2010 ◽  
Vol 67 (8) ◽  
pp. 2537-2546 ◽  
Author(s):  
John F. Scinocca ◽  
Bruce R. Sutherland
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Wave Train ◽  
Leading Edge ◽  
Wave Theory ◽  
Wave Drag ◽  
Tuning Parameter ◽  
Mean Flow ◽  
Propagating Waves ◽  
The Impact

Abstract A new effect related to the evaluation of momentum deposition in conventional parameterizations of orographic gravity wave drag (GWD) is considered. The effect takes the form of an adjustment to the basic-state wind about which steady-state wave solutions are constructed. The adjustment is conservative and follows from wave–mean flow theory associated with wave transience at the leading edge of the wave train, which sets up the steady solution assumed in such parameterizations. This has been referred to as “self-acceleration” and it is shown to induce a systematic lowering of the elevation of momentum deposition, which depends quadratically on the amplitude of the wave. An expression for the leading-order impact of self-acceleration is derived in terms of a reduction of the critical inverse Froude number Fc, which determines the onset of wave breaking for upwardly propagating waves in orographic GWD schemes. In such schemes Fc is a central tuning parameter and typical values are generally smaller than anticipated from conventional wave theory. Here it is suggested that self-acceleration may provide some of the explanation for why such small values of Fc are required. The impact of Fc on present-day climate is illustrated by simulations of the Canadian Middle Atmosphere Model.

A note on the solution of the Navier-Stokes equations for a spherically symmetric expansion into a very low pressure

1973 ◽  
Vol 59 (2) ◽  
pp. 391-396 ◽  
Author(s):  
N. C. Freeman ◽  
S. Kumar
Keyword(s):  
Shock Wave ◽  
Reynolds Number ◽  
Stokes Equation ◽  
Stokes Equations ◽  
Low Pressure ◽  
Navier Stokes ◽  
Spherically Symmetric ◽  
Navier Stokes Equation ◽  
Navier Stokes Equations ◽  
Type Flow

It is shown that, for a spherically symmetric expansion of a gas into a low pressure, the shock wave with area change region discussed earlier (Freeman & Kumar 1972) can be further divided into two parts. For the Navier–Stokes equation, these are a region in which the asymptotic zero-pressure behaviour predicted by Ladyzhenskii is achieved followed further downstream by a transition to subsonic-type flow. The distance of this final region downstream is of order (pressure)−2/3 × (Reynolds number)−1/3.

Sign in / Sign up

Export Citation Format

Share Document