Shock-Wave/Boundary-Layer Interactions in a Model Scramjet Intake

Large eddy simulation of flow around a NACA-0012 airfoil at a Reynolds number of 50,000 has been used to study the behavior of a laminar separation bubble near stall. The effects of the subgrid-scale model and explicit filtering were studied for a test case in which direct numerical simulation results were available. It was found that a method incorporating a mixed-time-scale model in addition to explicit filtering gave improved results compared with a method with filtering alone. Statistical results as well as snapshots of the flow below stall exhibit good agreement with the direct numerical simulations. For a configuration near stall, the effect of the spanwise domain width was investigated by increasing the spanwise length from 20 to 50% chord. Two-point velocity correlations showed a significant improvement for the wider computational domain, in which the simulation was able to capture a lowfrequency flow oscillation, in which intermittent bursting of the bubble was observed. The bubble bursting observed here is more irregular than in experiments at higher Reynolds number. The amplitude and frequency are compared with experimental results and with an unsteady viscous-inviscid interaction method which is shown to be capable of capturing unsteady behavior during stall.inviscid fluxes vector f = frequency of the flow oscillation G = filtered viscous fluxes vector H = shape factor H = L z = domain length in spanwise direction M = reference Mach number Pr = Prandtl number p = filtered pressure Q = conservative flow variables vector or second invariant of the velocity gradient tensor Q = filtered conservative flow variables vector q = flow variable q = filtered flow variablẽ q = Favre filtered flow variable q SGS = velocity scale for unresolved flow q 0 = small scale of the flow variable Re = Reynolds number based on the freestream conditions and chord length St = Strouhal number St fc sin =U S ij = strain rate tensor T= filtered temperature U = freestream velocity u = friction velocity t = eddy viscosity = angle of attack incidence = ratio of specific heats = filter size ij = Kronecker delta = displacement thickness = momentum thickness = dynamic viscosity = fluid kinematic viscosity = filtered fluid density ij = subgrid scale stress tensor kk = isotropic part of the subgrid scale Reynolds stress tensor w = shear wall stress h i = averaging over z

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“…These values were set from initial tests for turbulent channel flow with our code and have since been left unchanged [20].…”

Section: B Mixed-time-scale Modelmentioning

confidence: 99%

Intermittent Bursting of a Laminar Separation Bubble on an Airfoil

2010

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“…Furthermore, some studies during NASP indicated that an important delay of transition could eventually reduce the GTOW up to a factor of 2. On the other hand, the boundary layer on an intake surface is more robust in a turbulent state as an earlier transition can prevent massive separation [62] [63].…”

Section: High-speed Transitionmentioning

confidence: 99%

Achievements Obtained for Sustained Hypersonic Flight within the LAPCAT-II project

Steelant¹,

Varvill²,

Defoort³

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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The design of hypersonic airbreathing vehicles is a challenging objective due to the intrinsic complexity of propulsion-airframe integration in combination with an engine cycle design able to operate over a wide Mach number range. This is one of the objectives of EC co-funded project LAPCAT-II aiming to reduce antipodal flights to less than 2 to 4 hours. Among the several studied vehicles in the preceding project LAPCAT-I, only aircraft designs for Mach 5 and 8 flights were retained in the present project. Starting from the available Mach 5 vehicle and its related pre-cooled turbo-ramjet, assumed performance figures of different components were now assessed in more detail numerically and experimentally. Though the cruise flight of the Mach 8 vehicle based on a scramjet seemed feasible, further refinement was needed. In support to the integrated vehicle design, dedicated aerodynamic and propulsive experiments were done for the different components as well as for the complete vehicle. This included also the mutual verification of the windtunnels within Europe. In parallel, modelling implementation and validation on high-speed aerodynamics and propulsion were performed. The validated tools gave confidence to assess the performances of the fully integrated vehicles to comply with the mission goals. Finally, the impact of the emissions onto the climate was evaluated. Nomenclature

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“…In these inlets, the captured air is decelerated by a series of shock waves. As a result, the growing boundary layer along the wall of the inlet will experience several adverse pressure gradients, possibly leading to boundary-layer separation, which causes large total pressure loss, large distortion at the engine face, and even an inlet unstart [2,3]. It is therefore beneficial to control the flow either before or during the interaction process to prevent shock-induced separation, thereby improving the efficiency and reducing the distortion for hypersonic inlets.…”

Section: Introductionmentioning

confidence: 97%

Control of Shock/Boundary-Layer Interaction for Hypersonic Inlets by Highly Swept Microramps

Zhang

Tan

et al. 2015

Journal of Propulsion and Power

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The performance of hypersonic inlets is significantly affected by the presence of shock/boundary-layer interactions. To examine the potential of microramps for shock/boundary-layer interaction control in a finite-width duct, a detailed experimental and computational study has been conducted with a separated oblique shock/boundary-layer interaction generated by a 12 deg shock generator at Mach 3.5. Results show that the shock/boundary-layer interaction in the finite-width duct generates complex three-dimensional flow structures with significant swirling nature, and the traditional microramps cannot suppress the separation effectively. Therefore, a type of highly swept microramps with a large chord ratio and small incidence angle is brought forward and investigated. By the precompression effect, the dividing effect, the obstructing effect, and the energizing effect, the highly swept microramps with a height of 0.24 times the boundary-layer thickness show good control capability on the shock/ boundary-layer interaction. In addition, the efficiency of the control method for different shock impingement positions is obtained, indicating that the separation can be well controlled when the shock impinges on the aft part of the highly swept microramps. Nomenclature Ap= microramp incidence angle c = microramp chord length h = microramp height M 0 = incoming Mach number p symmetry = static pressure on the plate symmetry plane at station, where x is equal to 174 mm p 0 = static pressure of the incoming flow s w = spacing between adjacent microramps at the centerline W = plate width x = X-axis coordinate x 0 = distance between microramp beginning and the shock impingement position y = Y-axis coordinate z = Z-axis coordinate α = angle of the shock generator δ = thickness of the boundary layer θ = angle between side surface and bottom surface at tail of microramp σ = total pressure recovery coefficient

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Shock-Wave/Boundary-Layer Interactions in a Model Scramjet Intake

Cited by 62 publications

References 24 publications

Intermittent Bursting of a Laminar Separation Bubble on an Airfoil

Intermittent Bursting of a Laminar Separation Bubble on an Airfoil

Achievements Obtained for Sustained Hypersonic Flight within the LAPCAT-II project

Control of Shock/Boundary-Layer Interaction for Hypersonic Inlets by Highly Swept Microramps

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