Linear-stability-theory-based [Formula: see text] method plays an important role in boundary-layer transition prediction of aeronautical flows. Based on the simplification linear stability theory (Drela and Giles, AIAA J, 1987), amplification factor transport (AFT) equation for Tollmien–Schlichting waves using local variables was first proposed 2013 (Coder Maughmer, 2014). However, transonic high-Reynolds-number flows, AFT model seriously overestimates value text]. To fix this problem, we...

When studying instability of weakly non-parallel flows, it is often desirable to convert temporal growth rates unstable modes, which can readily be computed, physically more relevant spatial rates. This has been performed using the well-known Gaster's transformation for primary and Herbert's secondary a saturated mode. The issue temporal–spatial revisited in present paper clarify/rectify ambiguity/misunderstanding that appears exist literature. A mode its counterpart may related by sharing...

A computational fluid dynamics (CFD) compatible and fully local transition closure model is proposed for three-dimensional hypersonic boundary layers considering crossflow effects. The constructed with transport equations laminar fluctuation viscosity intermittency factor coupled Menter's shear stress turbulence model. Based on the parameter analyses of compressible Falkner–Skan–Cooke similarity solutions, key factors modeling, namely, maximum velocity Reynolds number, are evaluated through...

A new computational fluid dynamics compatible transition model for the natural and laminar separation bubble induced is established using two transport equations with consideration of analysis results through linear stability theory theory. One equation introduced to describe growth kinetic energy in boundary layer. In addition, another intermittency factor built trigger by controlling source term turbulent equation. Finally, applying a shear stress turbulence completes four-equation model....

A single-point transition closure model that incorporates analytical results by stability theory in a reasonably wide range of Mach numbers has been formulated for supersonic/hypersonic boundary-layer flows, which includes two transport equations to specify the onset locations: one eddy-viscosity coefficient laminar fluctuations and another intermittency factor. The effects compressibility are modeled through solutions self-similar boundary layer at subsonic supersonic conditions with...

In laminar hypersonic boundary layers, it is known that secondary instability plays a crucial role in transition to turbulence. The usually includes the fundamental mode, subharmonic and detuned mode. Considerable research exists on mechanism layers with smooth wall condition. topic of using micro-porous surfaces for disturbance stabilization has recently drawn interest. and, thus, possible delay arise due reduction growth rate primary Mack mode by porous surface. This paper focuses...

Transition prediction is a hot research topic of fluid mechanics. For subsonic and transonic aerodynamic flows, eN method based on Linear Stability Theory (LST) usually adopted reliably to predict transition. In 2013, Coder Maughmer established transport equation for Tollmien-Schlichting (T-S) instability so that the can be applied general Reynolds-Average-Navier-Stokes (RANS) solvers conveniently. However, this focuses T-S instability, invalid crossflow induced transition which plays...

Sediment movements on the riverbeds are crucial in fluvial processes. Therefore, studying incipient sediment motion is valuable for predicting changes behavior. In this study, influence of aquatic vegetation introduced into momentum balance equation under condition a bare bed. The presented model open channels covered by derived, consideration density and relative submergence. This study simplifies format. its coefficients demonstrate good applicability to various working conditions without...

During the cruise status of an underwater high-speed vehicle, flow around vehicle's head typically transitions from a laminar to turbulent state, triggering noise that can interfere with normal operation sonar. In order accurately investigate this through numerical simulation, high-fidelity field solution is essential. Common traditional turbulence simulation methods, such as unsteady Reynolds-averaged and large eddy (LES), struggle capture high-frequency fluctuations due their inability...

The traditional linear stability analysis for transition prediction includes the following steps: solving velocity profiles using boundary-layer equations or a computational fluid dynamics solver, guessing and searching operations eigenvalues, computing perturbation equations, integrating amplification factor . It is difficult to implement into modern solvers with parallel computations because it requires many nonlocal variables coordinate system transformations. In this Paper, an transport...

As boundary layer transition plays an important role in aerodynamic drag prediction, the proposal and study of prediction methods simulating complex flow phenomena are prerequisite for design. In this paper, with application linear stability theory based on amplification factor transport equations two-equation shear stress (SST) eddy-viscosity model, a new method, SST-NTS-NCF is yielded. The equation crossflow instability induced proposed to add NTS by Coder, which simulates...

In a previous study, we developed one-equation transition model for the bypass and laminar separation bubble (LSB)-induced based on local variables. this paper, distributed surface roughness effects are taken into account by constructing new transport equation amplification factor Ar. Modified criteria taking of Ar proposed to describe LSB-induced transitions. Moreover, predict flow properties in laminar–turbulent region more accurately, modified boundary condition rough surfaces is...

A correlation-based transition model has been developed by Langtry and Menter for modern computational fluid dynamics codes, which is widely used prediction in the field of turbomachinery aircraft. Langtry's could simulate bypass, laminar separation streamwsie Tollmien–Schlichting wave transition. Even so, this no ability to predict due crossflow instabilities three dimensional boundary layer. In paper, a new transport equation established based on experiment data self-similar equations. The...

The aerodynamic forces and flowfield on a delta-wing Unmanned Aerial Vehicle (UAV) with specific airfoil are studied here. leading-edge protuberances inspired from the flippers of humpback whale is introduced in present work to watch its effect stall delaying drag reduction. Two installing factors, which amplitude wavelength protuberances, considered study interaction variation de-tached vortex. Three changes both investigated herein. Generally, modified models have larger angle attack than...

In hypersonic boundary layers, Mack mode disturbances play an important role in laminar–turbulence transition. Understanding the secondary instability mechanism of will provide physical insight into turbulence generation for researchers, which is also meaningful transition control. According to previous studies over straight cones and flared cones, it seems that a pressure gradient may affect primary obviously. this paper, we are trying make clear what effect on modes influence rule is. Four...

A one-equation Reynolds-averaged Navier–Stokes closure model is established for bypass transition in this paper. new local indicator proposed to describe the variation of turbulence intensities and pressure gradients. Based on indicator, a novel efficient criterion formulated. For laminar separation bubble induced transition, reasonable modified intermittency factor developed complete reattachment process control size bubbles. Incorporated with Menter's k−ω shear stress transport model,...