Numerical computations of supersonic inlet flow

Gokhale, S. S.; Kumar, Venkat Ramana

doi:10.1002/fld.147

Cited by 12 publications

(8 citation statements)

References 8 publications

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“…The ÿrst series of element-level integrals in Equation (9) are the SUPG stabilization terms added to the variational formulation to stabilize the computations against node-to-node oscillations in the advection-dominated range. The SUPG formulation for the convection dominated ows was introduced by Hughes and Brooks [10] and Brooks and Hughes [11].…”

Section: The Governing Equations Letmentioning

confidence: 99%

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Euler flow in a supersonic mixed-compression inlet

Jain

Mittal

2006

Int. J. Numer. Meth. Fluids

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SUMMARYNumerical simulation of a two-dimensional mixed compression supersonic inlet is carried out by solving unsteady compressible Euler equations via a stabilized ÿnite element method. The geometry of the inlet is similar to the one used by Anderson and Wong for experimental investigation for Mach 3 ow. The computations are capable of simulating the start-up problems associated with the inlet. The critical back pressure for the successful operation of the inlet is computed. The e ect of inlet back pressure on the total pressure recovery and the ow distortion level is analysed. Contrary to the popular belief, it is found that in addition to the throat to inlet capture area ratio, the ramp geometry close to the throat plays an important role in the start-up dynamics. It is demonstrated via simulations that, everything else being same, the geometries of ramp upstream of the throat that are associated with a curvature higher than a certain threshold, result in unstarting the intake.

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Section: The Governing Equations Letmentioning

confidence: 99%

“…The geometry of the inlet they modelled is similar to the one experimentally studied by Anderson and Wong [3]. More recently, Gokhale and Venkat [9] also analysed supersonic inlets for ramjet and scramjet engines by using a explicit, ÿnite di erence MacCormack scheme.…”

Section: Introductionmentioning

confidence: 96%

Euler flow in a supersonic mixed-compression inlet

Jain

Mittal

2006

Int. J. Numer. Meth. Fluids

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“…These give the net scheme to be spatially second order. As the forward and backward differences are alternated between the predictor and corrector steps, this eliminates any bias due to the one-sided differentiation [6]. However, the alternation in the order of spatial differentiation introduces a pseudo-unsteadiness to the solution when marched in time.…”

Section: Maccormack Schemementioning

confidence: 99%

“…Most of the computations reported in the literature are for supersonic combustion chamber inlets and scramjet inlets [4,5,6]. The geometry of these inlets is not very complicated as the flow in these inlets lack any normal shock.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of Inviscid Airflows in Ramjet Inlets

Akbarzadeh

Kermani

2009

Transactions of the Canadian Society for Mechanical Engineering

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The performances of three different ramjet inlets and an entire ramjet are numerically studied in this paper. The fluid is assumed to be inviscid. Inlet 1 is a SCRAMJET inlet and is chosen from the literature. Inlets 2 and 3 are instead designed based on the Oswatitsch principle. Inlets 2 and 3 produce a series of oblique shocks merging at the engine cowl lip followed by a terminating normal shock just downstream of the inlet throat. In ramjet, the combustion is modeled using a non-uniform volumetric heat source distributed in the combustor area. The position of the terminating normal shock in Inlets 2 and 3 is controlled via the inlet's back pressure. Instead, in ramjet it is bounded by the amount of heat rate added in combustor and the exhaust nozzle throat area. For the numerical simulations, the Roe (1981) and MacCormack (1969) schemes are used. To prevent the spurious numerical oscillations in high resolution computations by Roe scheme the van Albada flux limiter (1982) is used, while in MacCormack scheme artificial viscosity terms are added to damp the oscillations. To double check the accuracy of the computations, the Fluent software package has also been used. Comparisons show very good agreement. LES SIMULATIONS NUMÉ RIQUES DE COURANTS ATMOSPHÉ RIQUES NON-VISQUEUX DANS DES ENTRÉ ES DE STATORÉ ACTEURS RÉ SUMÉLes performances de trois entrées de statoréacteurs différents et un statoréacteur entier sont été étudiés dans une façon numérique dans cet article. Le fluide est été supposé être nonvisqueux. L'entrée 1 est une entrée SCRAMJET et été choisie de la littérature. Au contraire, les entrées 2 et 3 ont été dessinées fondé sur le principe d'Oswatitsch. Les entrées 2 et 3 produisent un enchaînement des chocs obliques fondant à la lèvre sur le capot moteur suivi par un choc terminé normal en aval de la gorge de l'entrée. Dans le statoréacteur, la combustion est été imitée utilisant une source de chaleur volumétrique non-uniforme qui est été distribuée dans la chambre de combustion. La position du choc terminé normal dans les entrées 2 et 3 a été conduite par la contre-pression de l'entrée. Cependant, dans un statoréacteur, il est lié par l'amont de chaleur qui est été ajouté dans la chambre de combustion et la tuyère. Pour les simulations numériques, les schémas de Roe (1982) et MacCormack (1969 ont été utilisés. A empêcher les oscillations numériques fausses dans les calculs en haute résolution par le schème de Roe, le limiteur de fluidifiant de van Albada (1982) est été utilisé, pendant que dans le schème de MacCormack, les termes de viscosité artificielle ont été ajoutés à s'amortir les oscillations. A vérifier l'exactitude des calculs, le progiciel de Fluent est été utilisé. Les comparaisons montrent un très bon accord.

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“…The effect of the ramp geometry close to the throat on the starting of intake was also studied. Gokhale and Kumar [17] also analyzed supersonic inlets for ramjet and scramjet engines by using a explicit, finite difference MacCormack scheme. Trapier et al [18] simulated the supersonic inlet buzz at Mach number 1.8 using the Delayed Detached Eddy Simulation (DES) method.…”

Section: Introductionmentioning

confidence: 99%

Viscous flow in a mixed compression intake

Kotteda

Mittal

2010

Numerical Methods in Fluids

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Numerical simulation of the flow in a two-dimensional mixed compression intake is carried out by solving unsteady viscous compressible equations using a stabilized finite element method. The effect of bleed in starting/unstarting of the intake and controlling the buzz instability is investigated in detail. Higher bleed leads to an increase in the ability of the intake to sustain larger back-pressure for stable operation. The amount of bleed and its location is varied to understand its effect on the performance of the intake. Two kinds of unsteady oscillations are observed: 'little' and 'big' buzz. The frequency of the both kinds of buzz oscillations is found to be super-harmonic of the fundamental acoustic frequency of intake modeled as an open-closed organ pipe. The frequency as well as amplitudes of the big buzz cycles is larger than those of the little buzz. The little-and big-buzz are found to occur for low-and high-subcritical state of the intake and are very similar to Ferri and Dailey criteria, respectively. Buzz is eliminated when relatively high bleed is implemented, both, upstream and downstream of the throat. The effect of rate of change of back-pressure on the start/unstart of the intake is investigated. Two situations are considered. The first case is that of an intake where the back-pressure remains below the critical value. It is found that the intake remains started if the change in back-pressure is gradual. However, it unstarts if the back-pressure is changed relatively rapidly. The second set of simulations is an attempt to model the situation where the back-pressure at the exit of the intake exceeds the critical value and a logic is incorporated in the feed back loop of the fuel modulation to start the intake. Low rate of change of pressure is unsuccessful in starting the intake. Relatively high rates result in either a quick starting of the intake or a slow unstart. and forth in the convergent portion leading to high unsteadiness in the flow. It involves periodic filling and discharge of the plenum chamber, complex shock-boundary layer interaction, shear layer/slip stream-boundary layer interaction, transient shock movement and flow separation. It adversely affects the mass flow entering the engine and may lead to combustion instability, engine surge and flame out. It can also lead to deterioration of the performance of propulsion system, thus causing catastrophic loss in thrust.The buzz instability was first reported by Oswatitsch [3]. The tests were conducted for supersonic missile flights for Mach number in the range of 2.5-3.0. He observed buzz during his experiments, but disregarded it on the basis that a sub-critical range of operation is impractical and, therefore, not important. Later (1945)(1946)(1947)(1948)(1949)(1950)(1951)(1952)(1953)(1954)(1955), buzz was observed in many of the extensive experiments that were conducted at NASA, Langley on external compression inlets. Ferri and Nucci [4] conducted detailed experiments on an axisymmetrical external compression air intake. The occur...

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Numerical computations of supersonic inlet flow

Cited by 12 publications

References 8 publications

Euler flow in a supersonic mixed-compression inlet

Euler flow in a supersonic mixed-compression inlet

Numerical Simulations of Inviscid Airflows in Ramjet Inlets

Viscous flow in a mixed compression intake

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