Computation of Internal and External Compressible Flows Using EDICT

Int. J. Numer. Meth. Fluids

2006

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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.

Section: The Governing Equations Letmentioning

confidence: 99%

Euler flow in a supersonic mixed-compression inlet

Jain

Int. J. Numer. Meth. Fluids

2006

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“…Most studies that use the stabilized finite‐element method, for computing compressible flows, employ first‐order shape functions . Higher‐order methods provide geometric flexibility and are more efficient than low‐order methods, for problems that involve wave propagation, vortex‐dominated flows including high‐lift configuration.…”

Section: Introductionmentioning

confidence: 99%

“…In the present work, the stabilized finite‐element formulation is employed with quadratic interpolation. The stabilization coefficients for the linear triangular interpolation are the ones that were used in our earlier work and similar to those employed by Aliabadi and Tezduyar . These definitions are extended to quadratic elements.…”

Section: Introductionmentioning

confidence: 99%

Stabilized finite‐element computation of compressible flow with linear and quadratic interpolation functions

Kotteda

Numerical Methods in Fluids

2014

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SUMMARYThe unsteady compressible flow equations are solved using a stabilized finite‐element formulation with C0 elements. In 2D, the performance of three‐noded linear and six‐noded quadratic triangular elements is compared. In 3D, the relative performance is evaluated for 6‐noded linear and 18‐noded quadratic wedge elements. Results are compared for the solutions to Euler, laminar, and turbulent flows at different Mach numbers for several flow problems. The finite‐element meshes considered for comparison have same location of nodes for the linear and quadratic interpolations. For the turbulent flow, the Spalart–Allmaras model is used for closure. It is found that the quadratic elements yield better performance than the linear elements. This is attributed to accurate representation of the stabilization terms that involve second‐order derivatives in the formulation. When these terms are dropped from the formulation with quadratic interpolation, the numerical results are similar to those obtained with linear interpolation. The absence of these terms result in added numerical diffusion that seems to give the effect of a relatively reduced Reynolds number. For the same location of nodes, the computations with the linear triangular and wedge elements are approximately 20% and 100% faster than those with quadratic triangular and wedge elements, respectively. However, if the same quadrature rule for numerical integration is used for both interpolations, the computations with quadratic elements are approximately 20% and 45% faster in 2D and 3D, respectively. Copyright © 2014 John Wiley & Sons, Ltd.

“…The stabilization coefficients τ and δ are the ones that were used in our earlier work [16,17,[23][24][25] and similar to those employed by Aliabadi and Tezduyar [26]. The application of this formulation to compute various internal and external flows can be found in our earlier papers [16,17,[23][24][25]27]. The time discretization of the variational formulation given by Eq.…”

Section: A Flow Equationsmentioning

confidence: 99%

Flow in a Y-Intake at Supersonic Speeds

Kotteda

Journal of Propulsion and Power

2016

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Numerical simulation of the flow in a twin intake via solution to unsteady viscous compressible equations using a stabilized finite-element method has been carried out for various sideslip angles and backpressure ratios. Various flow regimes that are possible in the entire parameter space are identified. They are classified on the basis of shock structure and their locations and the unsteadiness in the flow. Buzz instability is observed in the intake at low system mass rates for nonzero sideslip angles. The onset of buzz is identified by zero mass flow rate in the leeward duct. It is associated with asymmetric movement of the bow shocks upstream of the duct entry. The onset of buzz is accompanied with a loss in static and total pressure recovery and increase in flow distortion. The effect of initial condition is studied. The flow in a certain regime is sensitive to the time history of the backpressure. Hysteresis in the flow as well as in the onset of buzz are observed. The effect of bleed is studied. The amount of bleed and the regions on which it is applied are varied to understand their effect on the performance of the intake. The onset of buzz is delayed with application of bleed.