Abstract The linear instability and breakdown to turbulence induced by an isolated roughness element in a boundary layer at Mach $2. 5$ , over isothermal flat plate with laminar adiabatic wall temperature, have been analysed means of direct numerical simulations, aided spatial BiGlobal three-dimensional parabolized (PSE-3D) stability analyses. It is important understand transition this flow regime since the process can be slower than incompressible crucial prediction local heat loads on...

The existing database of transition measurements in hypersonic ground facilities has established that as the nose-tip bluntness is increased onset boundary-layer over a circular cone at zero angle attack shifts downstream. However, this trend reversed sufficiently large values Reynolds number, so location eventually moves upstream with further increase bluntness. This transition-reversal phenomenon was focus collaborative investigation under NATO Science and Technology Organization (STO)...

Experiments are performed to investigate the effect of nose-tip bluntness on instability mechanisms leading boundary-layer transition a $7^{\circ }$ half-angle cone in Mach-6 free stream. The development disturbances is characterized using combination high-speed calibrated schlieren images and pressure measurements, data compared with results computed parabolized stability equations. approximately 414 mm long model equipped an interchangeable nose tip ranging from sharp 5.08 radius. For tips...

Global linear instability theory is concerned with the temporal or spatial development of small-amplitude perturbations superposed upon laminar steady time-periodic three-dimensional flows, which are inhomogeneous in two (and periodic one) all three directions.After a brief exposition theory, some recent advances reported.First, results presented on implementation Jacobian-free Newton-Krylov time-stepping method into standard finite-volume aerodynamic code to obtain global flows industrial...

Steady laminar flow over a rounded-tip $2\,:\,1$ elliptic cone of 0.86 m length at zero angle attack and yaw has been computed Mach number $7.45$ unit Reynolds $Re^{\prime }=1.015\times 10^{7}~\text{m}^{-1}$ . The conditions are selected to match the planned flight Hypersonic Flight Research Experimentation HIFiRE-5 test geometry an altitude 21.8 km. Spatial linear BiGlobal modal instability analysis this performed streamwise locations on planes normal symmetry axis, resolving entire domain...

The existing database of transition measurements in hypersonic ground facilities has established that, as the nose-tip bluntness is increased, onset boundary-layer over a circular cone at zero angle attack shifts downstream. However, this downstream movement slows down and eventually reverses sufficiently large values nose Reynolds number. Because modal amplification too weak to initiate measured frustum moderate values, nonmodal growth investigated potential basis for physics-based model....

Instability measurements of an axisymmetric, laminar separation bubble were made over a sharp cone-cylinder-flare with $12^{\circ }$ flare angle under hypersonic quiet flow. Two distinct instabilities identified: Mack's second mode (which peaked between 190 and 290 kHz) the shear-layer instability in same frequency band as first (observed 50 150 kHz). Both measured surface pressure sensors captured high-speed schlieren. Linear stability analysis results agreed well these terms both peak...

Compression corners are commonly present along aircraft, such as at control surfaces, and can cause shock/boundary-layer interactions when the vehicle moves supersonic or hypersonic speeds. By generating a separation bubble corner, shear layer is in flow, which potentially amplify instabilities, leading to boundary-layer transition downstream of reattachment. We show, through experiments conducted under low-disturbance Mach-6 amplification shear-layer instability by comparing measurements...

The purpose of this paper is to provide secondary instability analysis stationary crossflow vortices on a hypersonic yawed straight circular cone with $7^{\circ }$ half-angle at $6^{\circ angle attack, free-stream Mach number 6 and unit Reynolds $10.09\times 10^{6}~\text{m}^{-1}$ . At an three-dimensional boundary layer developed between the windward leeward symmetry planes. Under action azimuthal pressure gradients, flow near surface deflected more than edge layer. This results in...

Complex interrelated mechanisms mediate the stability of hypersonic boundary layers. Simulations are used to investigate key primary and secondary instabilities, including nonparallel effects intermode phase synchronization.

The interaction of stationary streaks undergoing non-modal growth with modally unstable instability waves in a supersonic flat-plate boundary-layer flow is studied using numerical computations. For incompressible flows, previous studies have shown that modulation due to below threshold amplitude level can stabilize the Tollmien–Schlichting waves, resulting delay onset laminar–turbulent transition. In regime, most-amplified linear become three-dimensional, corresponding oblique, first-mode...

A number of flow cases practical significance exhibit a predominant spatial direction, along which the mean properties field vary slowly while having fast variations on cross-sectional planes. This property is taken into account when three- dimensional parabolized stability equations (PSE-3D) are derived. These represent most efficient approach for solution instability problem such flows. In this work, linear PSE-3D extended to predict nonlinear development perturbations in kind complex...

The linear form of the parabolized stability equations is used in a variational approach to extend previous body results for optimal, nonmodal disturbance growth boundary-layer flows. This paper investigates optimal characteristics hypersonic Mach number regime without any high-enthalpy effects. influence wall cooling studied, with particular emphasis on role initial location and value spanwise wave that leads maximum energy up specified location. Unlike predictions basic state obtained from...

A convolutional neural network (CNN) is proposed to model laminar-turbulent transition. It takes velocity profiles as input and extracts scalars from the without using shape parameter directly. The CNN-extracted scalar correlates very well with for Falkner-Skan boundary layers.

Computations are performed to investigate the convective and global boundary-layer instabilities over a sharp cone–cylinder–flare model at zero-degree angle of attack. The geometry flow conditions selected match experiments conducted in Boeing/AFOSR Mach 6 Quiet Tunnel Purdue University. consists nominally 5 deg half-angle cone, followed by cylindrical segment, then 10 flare. Additionally, flare half angles equal 8 12 nosetip radii 0.1, 1, mm studied. An axisymmetric separation bubble is...

Non-modal linear stability analysis results are presented for hypersonic flow over an elliptic cone with aspect ratio of two at zero angle attack, completing earlier modal instability around the same geometry. The theoretical framework to perform transient growth compressible flows on a generalized two-dimensional frame reference is developed first time and then applied solve initial-value problem governing non-modal planes perpendicular axis, taken successive streamwise locations along...

Base flow computation and stability analysis were conducted for hypersonic over a cone-cylinder-flare (CCF) geometry conditions that correspond to the experimental runs carried out in three wind tunnels. Owing presence of an attached boundary layer, separation bubble induced by shock-boundary layer interaction, reattachment region, chosen configuration is physically rich. The complexity this flowfield encompasses combination convective instabilities developing on cone, global bubble,...

Several experimental campaigns have been conducted across a number of Mach-6 facilities on the hypersonic flow around cone-cylinder-flare (CCF) geometry with 5$^{\circ}$ half-angle cone and 12$^{\circ}$ flare. These experiments were as part NATO STO Research Task Group AVT-346, which is focused predicting boundary-layer transition complex geometries. This extended abstract describes details CCF model wind tunnel in France United States where this was tested. The final paper will include...

The present contribution discusses the development of a PSE-3D instability analysis algorithm, in which matrix forming and storing approach is followed. Alternatively to typically used stability calculations spectral methods, new stable high-order finite- dierence-based numerical schemes for spatial discretization 1 are employed. Attention paid issue eciency, critical success overall algorithm. To this end, use made parallelizable sparse linear algebra package takes advantage sparsity oered...

The interaction of stationary streaks undergoing non-modal growth with modally unstable instability waves in a high Mach number boundary-layer flow is studied using numerical computations. geometry and conditions are selected to match relevant trajectory location from the ascent phase HIFiRE-1 flight experiment; namely, $7^{\circ }$ half-angle, circular cone $2.5$ mm nose radius, free-stream equal $5.30$ , unit Reynolds $13.42~\text{m}^{-1}$ wall-to-adiabatic temperature ratio approximately...

Laminar–turbulent transition downstream of a backward-facing step (BFS) in two-dimensional zero-pressure-gradient boundary layer is investigated computationally for step-height–to–local-displacement-thickness ratios . The nominally sharp BFS previous wind tunnel experiment approximated via smooth shape with specified maximum slope. laminar basic state solutions the are computed by solving Navier–Stokes equations over curvilinear grid. linear amplification Tollmien–Schlichting instabilities...

To realize the drag reduction benefit of boundary-layer transition control strategies, it is crucial to integrate prediction into vehicle design through an optimization process. The integration based on linear stability analysis adjoint-based requires coupling adjoint-enabled computational fluid dynamics (CFD) solver with code. In particular, location often predicted using [Formula: see text]-factor method theory (LST). Thus, sensitivity linear-stability eigenvalues constitutes essential...