Shock wave-boundary-layer interactions in high-speed intakes

Shock wave boundary layer interaction (SWBLI) occurs in many aerospace applications such as wings in high-speed flight, missiles, and supersonic intakes. Key to the design of the latter is compressing a large volume of air with SWBLIs while maintaining maximum total pressure recovery and minimum flow distortion over a wide operating range. Under specific conditions, the formation of multiple SWBLIs (shock trains) within the intake can occur. Over the years, many numerical methods and models have been employed to predict the flow physics of shock trains. This work aims to determine the suitability of non-linear RANS turbulence closures for modelling shock trains in ducted geometries by implementing several non-linear closures in the University of Glasgow HMB3 CFD solver. First, the best modelling techniques for matching the experimental conditions were identified by performing validations against several shock train experiments. As a next step, several non-linear RANS closures were implemented in the solver. All closures improved the predicted wall pressures by accounting for the secondary flows present near the duct corners. The closures accounted for the secondary flow by predicting a fair level of normal Reynolds stress anisotropy near the corner of the duct. It was found that even simple non-linear closures based on quadratic constitutive relations result in significant improvements compared to linear closures. Additional simulations were performed at different Mach numbers, Reynolds numbers, and back (exit) pressures to assess the robustness of the non-linear closures and the sensitivity of the solution to changes in modelling parameters. It was observed that the flow distortion decreases rapidly downstream of the first shock in the shock train and that it is greatly influenced by its structure. As a final step, simulations of a shock train in a geometry representative of a highspeed intake were performed to assess the suitability of the closures for practical (real-world) applications. Three different geometries resulted in considerably different shock train structures compared to the ones in ducts. The flow distortion downstream of the shock train was found to be sensitive to both the incidence and roll angles. The SWBLI exhibited upstream and downstream movements within the intake with increasing incidence and roll angles

The Influence of Modelling in Predictions of Vortex Interactions About a Generic Missile Airframe: RANS

Within the framework of the NATO Science and Technology Organization Applied Vehicle Technology Task Group AVT316 calculations have been made of the supersonic flow around a slender body with wings and fins. In this paper a synthesis of the results obtained using the Reynolds Averaged Navier-Stokes equations are presented. The results show significant sensitivity to the choice of turbulence model. Whilst the gross features of the flow are similar, details of the development of the leeward wake are different. Simple linear eddy viscosity models predict vortices that rapidly decay, resulting in weak interactions with the downstream fins and relatively small rolling moments. This is attributed to an over production in turbulence quantities that results in excessive effective turbulent viscosity. Interventions that limit the production of turbulence, for example the SST limiter or curvature corrections, results in vortices that grow more slowly, changing the nature of the downstream interactions resulting in increased rolling moment. The use of more complex formulations, such as Reynolds stress models, that are inherently more capable for highly strained flows, further limits the rate of growth of the vortex cores leading to rolling moment predictions that are 2-3 times greater than those obtained with the simples

The Influence of Computational Mesh on the Prediction of Vortex Interactions about a Generic Missile Airframe

A research program has been underway for four years to study vortex interaction aerodynamics that are relevant to military air vehicle performance. The program has been conducted under the auspices of the NATO Science and Technology Organization (STO), Applied Vehicle Technology (AVT) panel by a Task Group with the identification of AVT-316. The Missile Facet of this group has concentrated their work on the vortical flow field around a generic missile airframe and its prediction via computational methods. This paper focuses on mesh-related effects and RANS simulations. Simulated vortex characteristics were found to depend strongly on the properties of the employed mesh, in terms of both resolution and topology. Predictions of missile aerodynamic coefficients show a great dependence on mesh properties as they are sensitive to computed vortex dynamics. Key suggestions about the desired mesh characteristics have been made. Based on these, a shared mesh was constructed to perform common analyses between the AVT-316 Missile Facet members. Mesh based uncertainties of the aerodynamic coefficient predictions were estimated via Richardson Extrapolation method

Parametric Study of Multiple Shock Wave/Turbulent Boundary Layer Interactions with a Reynolds Stress Model

No abstract available

The Influence of Modelling in Predictions of Vortex Interactions About a Generic Missile Airframe: RANS

Within the framework of the NATO Science and Technology Organization Applied Vehicle Technology Task Group AVT316 calculations have been made of the supersonic flow around a slender body with wings and fins. In this paper a synthesis of the results obtained using the Reynolds Averaged Navier-Stokes equations are presented. The results show significant sensitivity to the choice of turbulence model. Whilst the gross features of the flow are similar, details of the development of the leeward wake are different. Simple linear eddy viscosity models predict vortices that rapidly decay, resulting in weak interactions with the downstream fins and relatively small rolling moments. This is attributed to an over production in turbulence quantities that results in excessive effective turbulent viscosity. Interventions that limit the production of turbulence, for example the SST limiter or curvature corrections, results in vortices that grow more slowly, changing the nature of the downstream interactions resulting in increased rolling moment. The use of more complex formulations, such as Reynolds stress models, that are inherently more capable for highly strained flows, further limits the rate of growth of the vortex cores leading to rolling moment predictions that are 2-3 times greater than those obtained with the simplest models

The Influence of the Computational Mesh on the Prediction of Vortex Interactions about a Generic Missile Airframe

A research program has been underway for four years to study vortex interaction aerodynamics that are relevant to military air vehicle performance. The program has been conducted under the auspices of the NATO Science and Technology Organization (STO), Applied Vehicle Technology (AVT) panel by a Task Group with the identification of AVT-316. The Missile Facet of this group has concentrated their work on the vortical flow field around a generic missile airframe and its prediction via computational methods. This paper focuses on mesh-related effects and RANS simulations. Simulated vortex characteristics were found to depend strongly on the properties of the employed mesh, in terms of both resolution and topology. Predictions of missile aerodynamic coefficients show a great dependence on mesh properties as they are sensitive to computed vortex dynamics. Key suggestions about the desired mesh characteristics have been made. Based on these, a shared mesh was constructed to perform common analyses between the AVT-316 Missile Facet members. Mesh based uncertainties of the aerodynamic coefficient predictions were estimated via Richardson Extrapolation method

The Prediction of Vortex Interactions on a Generic Missile Configuration Using CFD: Current Status of Activity in NATO AVT-316

This paper provides a brief overview of the activities undertaken by the Missile Facet of NATO STO AVT 316 (Vortex Interaction Effects Relevant to Military Air Vehicle Performance) since its first meeting in April 2018. Rather than setting out to provide definitive technical statements, a broader, more narrative approach is taken towards summarising some of the key developments that have occurred during the early stages of the facet’s existence. To date, work has focussed on investigating a blind test case (CFD_OTC1) based on a generic missile airframe at a supersonic flight condition. Attention is focussed on the predicted total rolling moment coefficient, the polarity of which determines the airframe’s local static roll stability. While the facet is still some way from demonstrably achieving verified CFD solutions at the flight condition of primary interest, there is now little doubt that the airframe will be predicted to be locally unstable in roll

The Prediction of Vortex Interactions on a Generic Missile Configuration Using CFD: Current Status of Activity in NATO AVT-316

This paper provides a brief overview of the activities undertaken by the Missile Facet of NATO STO AVT 316 (Vortex Interaction Effects Relevant to Military Air Vehicle Performance) since its first meeting in April 2018. Rather than setting out to provide definitive technical statements, a broader, more narrative approach is taken towards summarising some of the key developments that have occurred during the early stages of the facet’s existence. To date, work has focussed on investigating a blind test case (CFD_OTC1) based on a generic missile airframe at a supersonic flight condition. Attention is focussed on the predicted total rolling moment coefficient, the polarity of which determines the airframe’s local static roll stability. While the facet is still some way from demonstrably achieving verified CFD solutions at the flight condition of primary interest, there is now little doubt that the airframe will be predicted to be locally unstable in roll