Article
Mechanics
Omar Kamal, Matthew T. Lakebrink, Tim Colonius
Summary: Linear input-output analysis is used to determine worst-case disturbances in a laminar base flow based on a generic forcing term. However, physically realizable worst-case disturbance problems lack a generic framework. In natural receptivity analysis, disturbances are forced by matching local solutions within the boundary layer to outer solutions. A scattering formalism is proposed to restrict the input forcing to realizable disturbances associated with plane-wave solutions of the outer problem. The method is validated through numerical simulations and provides insights into transition mechanisms.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Engineering, Aerospace
Shu-zi Yang, Wen-zhong Xie, Zhen-yu Wang, Jun Hu, Shengmin Guo
Summary: This paper presents a generalized scaling analysis of separation zones induced by shock wave-turbulent boundary layer interactions (SWTBLIs), considering the downstream expansion fan. The size of the separation zone is found to be closely related to the pressure increase at the reattachment point. The scaling correlation, normalized by the displacement thickness of the incoming boundary layer and the dynamic pressure of the incoming free stream, fits a wide range of experimental and numerical data.
JOURNAL OF AEROSPACE ENGINEERING
(2023)
Article
Engineering, Aerospace
Carson L. Running, Thomas J. Juliano
Summary: Measurements were conducted on a high-speed model using pressure-sensitive paint to capture unsteady shock-wave/boundary-layer interactions, with results indicating a significant effectiveness in providing insights into surface behavior. By calculating mean and fluctuating surface pressure, researchers were able to analyze the local characteristics of shock feet locations and frequency-dependent relationships, highlighting the importance of such measurements.
Article
Mechanics
Bajrang Sharma, Sharath S. Girimaji
Summary: Helmholtz decomposition is applied to study the effects of flow-thermodynamics interactions on high-speed boundary layer stability. The contributions of different perturbation components to the instability modes are investigated. It is found that dilatational and pressure field effects have little influence on the first-mode behavior, while the second mode is dominated by dilatational effects. The observed behavior is explained by examining the production and pressure-dilatation processes. The decomposition of perturbation momentum vector reveals that both first and second modes are dominated by solenoidal components.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
B. Bugeat, J-Ch Robinet, J-C Chassaing, P. Sagaut
Summary: Resolvent analysis is used to study the low-frequency behavior of the laminar oblique shock wave/boundary layer interaction (SWBLI). The computed optimal gain follows a first-order low-pass filter equation, consistent with previous findings. The damping rate scales with the scale, resulting in a constant Strouhal number. The study supports the idea that the low-frequency dynamics of the SWBLI is a forced dynamics, with background perturbations continuously exciting the flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Paolo Blondeaux, Giovanna Vittori
Summary: By investigating the stability of the boundary layer generated by the oscillations of a plate, critical values of Reynolds number for instability can be determined, corresponding to the transition from laminar to disturbed laminar, intermittently turbulent, and fully turbulent regimes in the flow.
JOURNAL OF FLUID MECHANICS
(2021)
Review
Mechanics
Datta V. Gaitonde, Michael C. Adler
Summary: Advances in measuring and understanding 2D shock-wave/turbulent-boundary-layer interactions have led to a focus on 3D STBLI, which display greater configuration diversity. Semi-infinite interactions exhibit a conical asymptotic behavior where specifics of the shock-generator become insignificant.
ANNUAL REVIEW OF FLUID MECHANICS
(2023)
Article
Mechanics
Weibo Hu, Stefan Hickel, Bas W. van Oudheusden
Summary: The flow over a forward-facing step at Ma(infinity) = 1.7 and Re-delta 0 = 1.3718 x 10(4) was investigated using large-eddy simulation. The study compared the effects of laminar inflow and turbulent inflow on the dynamics of the shock wave/boundary layer interaction. The results showed that in the turbulent inflow case, the separation shock and Gortler-like vortices were strongly correlated with low-frequency unsteadiness.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Thermodynamics
J. Braun, I. Rahbari, G. Paniagua, P. Aye-Addo, J. Garicano-Mena, E. Valero, S. Le Clainche
Summary: Investigation of a canonical wavy surface exposed to a Mach 2 flow reveals its unsteady characteristics and different flow features through various measurement methods.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2024)
Article
Mechanics
Rong Ma, Krishnan Mahesh
Summary: This study investigates boundary layer flows with an isolated roughness element using global stability analysis and direct numerical simulation. The results show that changes in geometry lead to different instability mechanisms, which in turn affect the evolution of vortical structures and the transition process of the flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Xin Li, Yue Zhang, Huijun Tan, Shu Sun, Hang Yu, Yi Jin, Jie Zhou
Summary: This study experimentally and analytically investigates the length scaling for the boundary layer separation induced by two incident shock waves in a Mach 2.73 flow. The experimental results show that the separation point moves downstream with increasing shock wave distance. For the dual-incident shock wave-turbulent boundary layer interactions exhibiting a coupling separation state, the upstream interaction length approximately linearly decreases with increasing distance, and the decrease rate increases with the second deflection angle. A prediction method for the upstream interaction length is proposed, with a relative error of about 10% compared to the experimental result.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Yongxiang Wu, Gabriel Axtmann, Ulrich Rist
Summary: Rotating cylinder stubs can exert significant control on their wake, creating a 'dominating inner vortex' which intensifies lift-up effects and generates high-amplitude streaks. These effects can effectively stabilize Tollmien-Schlichting modes. However, roughness elements also introduce irregularities in the boundary layer flow, leading to increased fluid instability.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Xin Li, Yue Zhang, Huijun Tan, Yi Jin, Chao Li
Summary: This study investigates the interactions between the boundary layer and two successive incident shock waves in supersonic mixed-compression inlets. Experimental and analytical methods are used to study the turbulent boundary layer separation induced by single and dual shock waves. The study reveals different flow features and separation region shapes depending on the distance between the shock waves.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Aerospace
Yuhan Lu, Jianhan Liang, Zaijie Liu, Hongkang Liu, Chao Yan
Summary: Here, a numerical approach for the three-dimensional global instability analysis of high-speed boundary layer is developed and validated in two cases. The results demonstrate that this approach can accurately predict the wavelength, growth rate, and disturbance amplitude of unstable modes.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)
Article
Mechanics
Shuyi Liu, Bingbing Wan, Xianxu Yuan, Ligeng Zhang, Jianqiang Chen, Xi Chen
Summary: A systematic parametric study was conducted on the modal global linear instability of Mach 6 boundary-layer flow over an inclined cone at a 6° angle of attack under typical wind tunnel conditions using spatial BiGlobal theory. Two classes of global instabilities were observed in the outboard region away from the leeward plane: high-frequency second mode instabilities and low-frequency crossflow instabilities. The global stability characteristics of the crossflow instability over a conical configuration were uncovered for the first time, revealing many unstable modes with a complex pattern. The most amplified frequency of these modes was around 30 kHz, and they were mainly distributed on the leeward side of the cone.
Article
Physics, Fluids & Plasmas
Pedro S. Volpiani, Matteo Bernardini, Johan Larsson
PHYSICAL REVIEW FLUIDS
(2020)
Article
Physics, Fluids & Plasmas
Pedro S. Volpiani, Prahladh S. Iyer, Sergio Pirozzoli, Johan Larsson
PHYSICAL REVIEW FLUIDS
(2020)
Article
Engineering, Aerospace
Jan-Erik Schumann, Siavash Toosi, Johan Larsson
Article
Chemistry, Physical
Abishek Gopal, Pedro S. Volpiani, Shashank Yellapantula, Johan Larsson
Summary: This study investigates the effects of real fluid thermodynamic and transport properties on the structure and propagation of canonical planar, unstretched, premixed methane-oxygen flames at transcritical conditions. It is found that the choice of chemical mechanism has a much greater influence on mass burning rates than the real fluid effects, which mainly lower mass burning rates and laminar flame speeds.
JOURNAL OF SUPERCRITICAL FLUIDS
(2021)
Article
Engineering, Aerospace
Johan Larsson
Article
Mechanics
Mario Di Renzo, Nikhil Oberoi, Johan Larsson, Sergio Pirozzoli
Summary: Crossflow has a significant impact on the interaction between an impinging shock wave and a high-speed turbulent boundary layer, leading to changes in the size and strength of the separation bubble and the growth rate of the shear layer. The three-dimensional effects observed in this interaction present challenges for turbulence models for compressible flows.
THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS
(2022)
Article
Engineering, Aerospace
Johan Larsson, Vedant Kumar, Nikhil Oberoi, Mario Di Renzo, Sergio Pirozzoli
Summary: This study investigates an idealized shock/boundary-layer interaction problem that is two dimensional in the mean but has a three-component mean velocity field using large-eddy simulations. The results reveal that the addition of a crossflow significantly increases the size of the separation bubble, and the flow reattaches after the precursor bubble at high Reynolds numbers.
Article
Computer Science, Interdisciplinary Applications
Siavash Toosi, Johan Larsson
Summary: This paper presents an alternative derivation and interpretation of the Germano identity and its error, indicating that the Germano identity error directly estimates the residual of the LES equation, serving as the source of errors in LES. The proposed method offers a robust and easy to compute definition for the source of errors, with important applications in grid/filter adaptation and estimating uncertainties in coarse-graining.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Engineering, Aerospace
Ali Berk Kahraman, Johan Larsson
Summary: This paper presents a postprocessing algorithm that systematically determines the exchange location for wall-modeled large-eddy simulations. The algorithm combines a model for the error in predicted wall shear stress and a model for computational cost to find the optimal exchange location. The algorithm is tested under different flow conditions and shows agreement with expert suggestions for exchange locations, providing more accurate wall-modeled layer thickness in different flow regions.
Article
Mechanics
Alessandro Ceci, Andrea Palumbo, Johan Larsson, Sergio Pirozzoli
Summary: This study investigates the influence of turbulence inflow generation on high-speed turbulent boundary layers through direct numerical simulations (DNS). Two main types of inflow conditions are considered and compared. DNS with very long streamwise domains are performed to provide reliable data. Simulations with shorter domains are then conducted and compared with benchmark data, revealing significant deviations and dependency on inflow turbulence seeding.
THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS
(2022)
Article
Mechanics
Alessandro Ceci, Andrea Palumbo, Johan Larsson, Sergio Pirozzoli
Summary: We develop a scaling law for the characteristic frequencies of wall pressure fluctuations in swept shock wave/turbulent boundary layer interactions with cylindrical symmetry. Direct numerical simulations reveal the presence of spanwise rippling of the separation line, with wavelength proportional to separation bubble size. Pressure disturbances around the separation line are convected at a phase speed proportional to the cross-flow velocity. Based on this information, we propose a simple model for low-frequency unsteadiness that accurately predicts the growth of the typical frequency with the sweep angle. The typical frequencies in more general swept shock wave/turbulent boundary layer interactions are also discussed.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Engineering, Aerospace
Walter Arias-Ramirez, Nikhil Oberoi, Johan Larsson
Summary: A novel approach to compute affordable approximate sensitivities in a large-eddy simulation (LES) is proposed and assessed. The approach involves solving a linearized Reynolds-averaged Navier-Stokes (RANS) problem around the mean LES solution, with closure modeling for the linearized changes in turbulent Reynolds stresses. The method is evaluated using a linearized algebraic turbulence model, and demonstrates accurate prediction of sensitivity for skin friction coefficient and mean velocity field.
Article
Engineering, Aerospace
Cetin C. C. Kiris, Aditya S. S. Ghate, Oliver M. F. Browne, Jeffrey Slotnick, Johan Larsson
Summary: A summary is provided of the nine submissions to the WMLESLB TFG at the 4th High lift Prediction Workshop. The analysis of the data suggests that a high number of spatial degrees of freedom are needed for accurate prediction of pitching moments at high angles of attack. The superior performance of WMLES methods over RANS is demonstrated in terms of separation patterns and agreement with experimental results.
JOURNAL OF AIRCRAFT
(2023)
Article
Engineering, Aerospace
Asif Manzoor Hasan, Johan Larsson, Sergio Pirozzoli, Rene Pecnik
Article
Physics, Fluids & Plasmas
Asif Manzoor Hasan, Johan Larsson, Sergio Pirozzoli, Rene Pecnik
Summary: The paper presents a transformation method that converts compressible wall-bounded turbulent flows with nonuniform fluid properties into equivalent incompressible flows with uniform fluid properties. The method considers both variable-property and intrinsic compressibility effects, with the latter being the key improvement over existing techniques. The importance of intrinsic compressibility effects contradicts the renowned Morkovin's hypothesis.
PHYSICAL REVIEW FLUIDS
(2023)