Free Shear Layer Research Articles

Vortices evolution in the flow over a sharp leading edge at low Reynolds number

Particle image velocimetry and hydrogen bubble flow visualization techniques are used to experimentally investigate the vortex shedding and their formation in a separated boundary layer induced by the leading edge of a sharp-nosed plate. The Reynolds number based on the plate thickness is 370, while the maximal mean reverse velocity is 16% of the free-stream velocity. Two kinds of shedding vortices with different scales are identified: primary vortices (PVs) shedding periodically and secondary vortices (SVs) appearing irregularly with a relatively smaller scale. PVs are formed by the Kelvin-Helmholtz instability of the free shear layer with a consideration of wall effect. SVs are generated in the vicinity of the crest of the bubble, downstream of PVs’ formation region. The comparisons of conditional-averaged shedding periods with and without SV indicate that the formation of SV is related to the position where the adjacent downstream PV obtains maximal circulation. An SV tends to form when this position is further upstream. Moreover, the SVs are related to the disturbance amplification of 2f0, the high order harmonic of the PV shedding frequency f0. In the first half part of the bubble, the corresponding disturbance of 2f0 shows no distinct growth until the formation of SVs.

Observations of Island Wakes at High Rossby Numbers: Evolution of Submesoscale Vortices and Free Shear Layers

AbstractOceanic vortex evolution on the lee side of Taiwan’s Green Island (~7 km in diameter), where the Kuroshio flows at a speed of 1–1.5 m s−1, is observationally examined and compared to theories and the preceding results of laboratory experiments. In the near wake, recirculation occurs with a relative vorticity of ζ ~ 20f (where f is the planetary vorticity) and subsequently sheds at a combination of periods resulting from the tidal oscillations and the intrinsic time scale of eddy evolution. The tidal oscillations are the predominant processes. Our analysis suggests that an island positioned in the Kuroshio with periodic and cross-stream tidal excursions is analogous to a cross-stream oscillating cylinder. Consequently, the shedding period of the vortex is synchronized to a tidal period occurring close to the intrinsic period. The free shear layer, which is characterized by an ~30f relative vorticity band (2 km wide) and a wavy thermal front, develops between the Kuroshio and recirculation. The frontal wave occurring over a time period of 0.5–2 h resembles Kelvin–Helmholtz instability corresponding to high Re values. For the far wake, repeated cross-wake surveys suggest that cyclonic and anticyclonic vortices are alternatively present at a period close to the period of M2 tides in agreement with near-wake measurements. Repeated along-wake surveys reveal a cyclonic eddy shedding downstream at a speed of 0.35 m s−1, 1/3 of the upstream current speed, from the near wake. In comparing our observations with the results of previous water tank experiments, an Re value of O(103) for the submesoscale wake regime is expected.

Nonstationary Vortex Streets in Shear Flows

Spatially periodic vortex systems that form due to unstable shear flows are called vortex streets. A number of exact and asymptotic solutions of two-dimensional hydrodynamic equations describing nonstationary vortex streets have been constructed. It is shown that the superposition of the flow with a constant horizontal shear and its perturbations in the form of a nonmodal wave provides an exact solution that describes a nonstationary vortex street with rotating elliptic current lines. The width of the zone occupied by such a vortex street has been determined. The equation of separatrix separating vortex cells with closed current lines from an external meandering flow has been obtained. The influence of the quasi-two-dimensional compressibility and beta effect on the dynamics of vortex streets has been studied based on the potential vorticity transport equation. The solutions describing the formation of vortex streets during the development of an unstable zonal periodic flow and a free shear layer have been constructed using a longwave approximation.

Transition to chaos in a cross-corrugated channel at low Reynolds numbers

The pressure-gradient driven flow in a three-dimensional cross-corrugated channel is investigated based on large eddy simulations. The channel geometry is highly tortuous so that the flow unsteadiness can be triggered at a moderate Reynolds number. The objective of this paper is to provide a better understanding of the laminar-to-chaotic transition in this type of channel. The transition from steady to chaos is found to occur at a low Reynolds number range between 77.4 and 113.1. The nonlinear dynamics is analyzed based on the power spectra of the velocity and reconstructed phase space. The route to chaos is identified, which favors the Ruelle-Takens-Newhouse scenario. Moreover, the transition from quasiperiodic mode to chaotic mode is accompanied with temporal intermittencies. The fluid dynamics is analyzed. It is found that the cross-corrugated geometry prompts a recirculating-and-rotating wake behind each contact corner. Each wake is enfolded by a pair of curved free shear layers. They are destabilized by the Kelvin-Helmholtz instability, leading to the periodic flow oscillation. Subsequently, the centrifugal instability sets in and promotes a type of primary vortex structures, forming streamwise “zig-zag” vortex streets. The competition between the adjacent vortex streets leads to a quasiperiodic flow. Temporal intermittencies emerge as the Reynolds number is increased. Finally, the periodicities in both the streamwise and spanwise directions are broken, and the flow becomes chaotic. When further increasing the Reynolds number to 343.1, Taylor-Görtler-like vortexes and necklace-like vortexes are formed in the channel.

Compressibility effects on the transition to turbulence in a spatially developing plane free shear layer

The compressibility effects on the transition to turbulence in a spatially developing, compressible plane free shear layer are investigated via direct numerical simulation using a high-order discontinuous spectral element method for three different convective Mach numbers of 0.3, 0.5, and 0.7. The location of the laminar–turbulent transition zone is predicted by the analyses of vorticities, Reynolds stresses, and the turbulent dissipation rate. In the turbulence transition and self-similar turbulence regions, the effects of compressibility on the flow properties, such as the velocity autocorrelation function, integral time scale, momentum thickness, Reynolds stress, and turbulent kinetic energy budget, are investigated. The compressibility effects on the onset and length of the turbulence transition zone are studied based on the analyses of such flow properties. The mean velocity, momentum thickness, and Reynolds stress profiles compare well with published experimental data. Vorticity contours and iso-surface of the second invariant of velocity gradient tensor identify the characteristic of flow structures. The two-point correlation functions of velocity components, the one-dimensional (1D) spanwise energy spectrum, and the balance of the turbulent kinetic energy transport equation validate the domain size and resolution of the adopted grid for turbulence simulation. An increase in the convective Mach number leads to a reduction in the sizes of the largest-scale structures, resulting in a significant decrease in Reynolds stresses and turbulence production. The onset of turbulence transition and the location where the transition completes shift downstream, while the length of the transition zone increases with increasing convective Mach number.

Towards an enhanced protection of attached boundary layers in hybrid RANS/LES methods

A robust strategy for the RANS shielding of attached boundary layers in a hybrid RANS/LES context is presented, addressing two major issues. Firstly, the attached boundary layers must be detected to ensure their RANS treatment, but the original shielding function used by automatic methods such as DDES (2006) or ZDES mode 2 (2012) fails for fine meshes and/or with adverse pressure gradients, motivating the present study. Secondly, even with a stronger shielding, there should not be an excessive delay in the formation of instabilities and resolved LES content in free shear layers. Both objectives cannot be simultaneously reached by only tuning a constant in the original shielding function. The proposed new ZDES mode 2 consequently involves three main ingredients, namely a second shielding function detecting the outer part of the wake layer including with strong adverse pressure gradients, an inhibition function which switches off the second shielding when flow separation is detected, and a significant enhancement of the destruction of eddy viscosity in grey areas. The calibration of the method relies on a set of boundary layers at various Reynolds numbers and pressure gradients conditions and is confirmed by a priori tests in three-dimensional flows around curved geometries. The resulting case-independent model, the new ZDES mode 2, is assessed on four test cases, namely a flat-plate boundary layer, a mixing layer, a backward facing step and transonic buffet over a supercritical airfoil. Overall, it is shown that the new ZDES mode 2 is relevant with respect to four objectives: protection of attached boundary layers for any grid cell size (including infinite mesh refinement) and pressure gradient, RANS shielding at least as broad as the original shielding in any situation, minimum delay in the formation of resolved LES content, and full compatibility of the resulting subgrid scale model in the LES branch with the other modes of ZDES (modes 1 and 3) ensuring a continuous treatment of resolved turbulence across zones treated with different ZDES modes. The new robust ZDES mode 2 consequently is a case-independent answer to the demand for a general automatic and robust RANS/LES treatment of attached and massively separated flows.

Choking and hydraulic jumps in laminar flow

AbstractThe viscous hydraulic jump still represents research in progress rather than a finalised edifice. The existing rigorous approaches show how this phenomenon is tied in with a bifurcation of the upstream flow adjacent to the guiding rigid plate of finite length, aligned perpendicularly to the direction of gravity. Here, this together with the upstream influence by the detached flow triggers transition from super‐ to subcritical flow (sensing its susceptibility to the upstream propagation of small disturbances). We present recent advances in the self‐consistent theory of single‐layer jumps continued as free shear layers.

Large eddy simulations of multiphase flows past a finite plate near a free surface

Simulations have been conducted to quantify the effects of aspect ratio on the lift and drag coefficient for a finite plate near a free surface. Large eddy simulations using a VOF multiphase model were conducted for a plate length to height aspect ratio of 2.5, 5 and 10 for a Reynolds number of 50,000 and a Froude number of 1.3. Eulerian and Lagrangian coherent structures were employed to characterize the turbulent flow fields. As the aspect ratio increases, the mean drag coefficient decreases from 1.88 to 1.73. This is due to an increase in vortex activity caused by separation of the free shear layer at L/D of 5 and 10. Both the upstream and downstream region are affected by the hairpin-like vortices generated from the bursting of the free shear layer. With increasing plate length, Karman vortex shedding from the face near the free surface is suppressed, and the influence of tip vortices on the near wake flow is reduced. The aspect ratio has a strong influence on the free surface shape and dynamics because surface deflections increase with L/D. Free surface flows studied here provide valuable insight into designing off-shore structures, platforms, hydraulic and marine-current energy harvesting devices.

Reference numerical database for turbulent flow and heat transfer in liquid metals

Turbulent heat transfer is a complex phenomenon that has challenged turbulence modellers over various decades. In this regard, in the recent past, several attempts have been made for the assessment and further development/calibration of the available turbulent heat flux modelling approaches. One of the main hampering factors with respect to the further assessment of these modelling approaches is the lack of reference data. In the framework of the EU SESAME and MYRTE projects, an extensive effort has been put forward to generate a wide range of reference data, both experimental and numerical, to fill this gap. In that context, this article reports the numerical database that has been generated within these projects for various liquid metal flow configurations in different flow regimes. These high fidelity numerical data include seven different flow configurations: a wall-bounded mixed convection flow at low Prandtl number with varying Richardson number (Ri) values; a wall-bounded mixed and forced convection flow in a bare rod bundle configuration; a forced convection confined backward facing step (BFS) with conjugate heat transfer; a forced convection impinging jet for three different Prandtl fluids corresponding to two different Reynolds numbers of the fully developed planar turbulent jets; a mixed-convection cold-hot-cold triple jet configuration corresponding to Ri=0.25; an unconfined free shear layer for three different Prandtl fluids; and a forced convection infinite wire-wrapped fuel assembly. These high-fidelity numerical databases will serve the further development of turbulent heat transfer models by providing unique, new and detailed data for the thermal-hydraulic behaviour of liquid metals in various flow configurations.

Large-scale motions in a plane wall jet

The plane wall jet (PWJ) is a wall-bounded flow in which a wall shear layer develops in the presence of extremely energetic flow structures of the outer free-shear layer. The structure of a PWJ, developing in still air, was studied with the focus on the large scales in the flow. Wall-normal hot-wire anemometry (HWA) measurements along with double-frame particle image velocimetry (PIV) measurements (wall-normal–streamwise plane) were carried out at streamwise distances up to $162b$, where $b$ is the slot width of the PWJ exit. The nominal PWJ Reynolds number based on exit parameters was $Re_{j}\approx 5940$. Comparisons with a zero-pressure-gradient boundary layer (ZPGBL) at nominally matched friction Reynolds number $Re_{\unicode[STIX]{x1D70F}}$ were also carried out as appropriate, to highlight key features of the PWJ structure. Consistent with previous work, the PWJ showed a dependence of the peak turbulent stresses on the jet exit Reynolds number. The turbulent production showed a peak corresponding to the near-wall cycle similar to the peak seen in the ZPGBL. However, another turbulent production peak was observed in the outer free-shear layer that was an order of magnitude larger than the inner one. Along with the change in sign of the viscous and Reynolds shear stresses, the PWJ was shown to have a region of very low turbulent production between these two peaks. The dissipation rate increased over the PWJ layer with a peak also in the outer region. Visualizations of the flow and two-point correlations reveal that the most energetic large-scale structures within a PWJ are vortical motions in the wall-normal–streamwise plane similar to those structures seen in free-shear layers. These structures are referred to as J (for jet) type structures. In addition two-point correlations reveal the existence of large-scale structures in the wall region which have a signature similar to those structures seen in canonical boundary layers. These structures are referred to as W (for wall) type structures. Instantaneous PIV realizations and flow visualizations reveal that these W type large-scale features are consistent with the paradigm of hairpin vortex packets in the wall region. The J type structures were seen to intrude well into the wall region while the W type structures were also seen to extend into the outer shear layer. Further, these large-scale structures were shown to modulate the amplitude of the finer scales of the flow.

Effects of non-uniform permeability on vortex shedding and noise control of blunt trailing edge

In this paper, the characteristics of the vortex shedding and noise of the blunt trailing edge with different porous permeable segment are studied by numerical simulation. The permeability distribution is adjusted through continuously changing the viscous drag of porous region to achieve uniformity and non-uniformity. The simulation results firstly show that the porous trailing edge can stabilize the free shear layer in a certain range of viscous drag coefficient to suppress the vortex shedding and reduce the overall noise level significantly. The optimized non-uniform permeability can further reduce the noise by 3dB than that of uniform permeability for porous blunt trailing edge. The discrete strip-shaped porous blunt trailing edge is proposed for more practical engineering application. It is found that the noise level is increased by 2 dB rather than optimal function distribution. However, the discrete strip porous trailing edge still has significant noise reduction capacity with respect to solid blunt trailing edge. The three-dimensional simulation demonstrates further that the non-uniform permeable trailing edge behaves more potential than uniform permeable trailing edge and reveals the crucial spanwise synergy effects by porous treatment.

RANS prediction of open jet aerofoil interaction and design metrics

ABSTRACTRANS models remain an attractive turbulence simulation method which could provide some open jet aerofoil interaction analysis at a fraction of the cost of a high-fidelity LES approach. The present work explores the potential and limitations of RANS in this context by simulating an open jet aerofoil noise experiment using the aerospace oriented Menter SST RANS model. This model’s tendency to transition at a critical Reynolds number lower than the experimental value was found to impact the boundary layer development. However, the introduction of a low-Re correction improved the prediction of surface pressure and skin friction, enabling the suction surface separation bubble to be captured. The free shear layer’s virtual origin characteristics exhibited sensitivity to the interaction with the aerofoil, which can be developed into a metric of the interaction. The main challenge for RANS was accounting for the rise in background disturbance level in the working section, which is caused by the high-turbulence intensity in the free shear layers.

Experimental Investigation of Isoenergetic Film-Cooling Flows with Shock Interaction

The interaction of shock waves with supersonic film-cooling flows is investigated experimentally by high-speed particle-image velocimetry. A laminar jet is tangentially injected into a turbulent boundary layer at a freestream Mach number . The injection Mach numbers are and . The total temperature and static pressure of the injection match the freestream condition. A deflection of and generates a shock that impinges upon the film-cooling flow at two positions downstream of the injection slot. The flow structure of the shock/cooling-film interaction is highly sensitive to the injection Mach number. An increased injection Mach number (i.e., higher near-wall momentum) stabilizes the flow and drastically decreases the separation-bubble size. Because of the additional free shear layer and the near-wall jet, the large-scale low-frequency motion of the separation shock is reduced by one order of magnitude compared to the oscillation in standard shock/boundary-layer interaction.

GPGPU implementation of a lattice Boltzmann methodology for particle transport and deposition in complex flow

Purpose This study aims to modify the standard probabilistic lattice Boltzmann methodology (LBM) cellular automata (CA) algorithm to enable a more realistic and accurate computation of the ensemble rather than individual particle trajectories that need to be updated from one time step to the next (allowing, as such, a fraction of the collection of particles in any lattice grid cell to be updated in a time step, rather than the entire collection of particles as in the standard LBM-CA algorithm leading to a better representation of the dynamic interaction between the particles and the background flow). Exploitation of the inherent parallelism of the modified LBM-CA algorithm to provide a computationally efficient scheme for computation of particle-laden flows on readily available commodity general-purpose graphics processing units (GPGPUs). Design/methodology/approach This paper presents a framework for the implementation of a LBM for the simulation of particle transport and deposition in complex flows on a GPGPU. Towards this objective, the authors have shown how to map the data structure of the LBM with a multiple-relaxation-time (MRT) collision operator and the Smagorinsky subgrid-scale turbulence model (for turbulent fluid flow simulations) coupled with a CA probabilistic method (for particle transport and deposition simulations) to a GPGPU to give a high-performance computing tool for the calculation of particle-laden flows. Findings A fluid-particle simulation using our LBM-MRT-CA algorithm run on a single GPGPU was 160 times as computationally efficient as the same algorithm run on a single CPU. Research limitations/implications The method is limited by the available computational resources (e.g. GPU memory size). Originality/value A new 3D LBM-MRT-CA model was developed to simulate the particle transport and deposition in complex laminar and turbulent flows with different hydrodynamic characteristics (e.g. vortex shedding, impingement, free shear layer, turbulent boundary layer). The solid particle information is encapsulated locally at the lattice grid nodes, allowing for straightforward mapping of the datastructure onto a GPGPU enabling a massive parallel execution of the LBM-MRT-CA algorithm. The new particle transport algorithm was based on the local (bulk) particle density and velocity and provides more realistic results for the particle transport and deposition than the standard LBM-CA algorithm.

Vortex merging in a laminar separation bubble under natural and forced conditions

Vortex merging in a laminar separation bubble (LSB) is studied experimentally. The bubble is formed on the suction side of a NACA 0018 airfoil at an angle of attack of 4° and a Reynolds number of 125 000. The merging process in the bubble is manipulated through acoustic forcing applied as a tone at either the fundamental vortex shedding frequency or at the first subharmonic of this frequency. The flow field is assessed using time-resolved, two-component particle image velocimetry. A method for detecting merged structures using wavelet analysis is introduced, allowing for reliable quantification of merging events. The results show that vortex merging occurs naturally in the separation bubble, while forcing at the subharmonic and fundamental frequencies promotes and inhibits merging, respectively. While these trends are similar to those observed for free shear layers, the subharmonic forcing of an LSB is found to directly promote disturbance development at the subharmonic frequency. For all cases, the majority of merging events take place in the aft portion of the bubble, i.e., downstream from the maximum bubble height location and upstream of mean reattachment, with subharmonic forcing causing merging to shift upstream. The merged structures are found to be the most energetic flow features; however, promoting vortex merging through subharmonic forcing does not lead to significant changes in the mean bubble topology. The spanwise behavior of the vortex merging process is studied, revealing that structures merge in a spanwise nonuniform manner, with localized merging occurring away from where forward or rearward streamwise bugles develop in the vortex filaments. Statistical characterization reveals that merging tends to occur more often over some specific spanwise segments, with the number of primary structures that merge varying by as much as 50% between spanwise locations. These findings offer insight into vortex merging in laminar separation bubbles and the attendant influence of forcing, while also highlighting the need to consider spanwise aspects of flow development.

Analysis of Flow Oscillation Due to Sidewall of Three-Dimensional Supersonic Open Cavity Flow

Unsteady turbulent flow simulations were performed based on the Reynolds-averaged Navier–Stokes (RANS) equations to investigate flow oscillation due to three-dimensional (3D) configuration of a Mach 1.5 supersonic open cavity flow with a length-to-depth ratio of 3. Two-dimensional (2D) and 3D unsteady simulation results were analyzed and compared with experimental data and Rossiter’s empirical prediction data. The three-dimensional cavity width-to-depth ratio (W/D) was 1, 3.8 and 7.6. Computational results indicated that pressure oscillation in the 2D flow was generated by a single-flow structure, whereas a multiple-flow structure generated multiple oscillation peaks in the 3D flow. The flow structure in the 3D cavity was investigated. For the 2D flow case, the cavity internal pressure wave was directly synchronized with the free shear layer. In the 3D flow case, an unstable spanwise flow due to the sidewall was observed. This spanwise fluctuation produced additional pressure oscillations coupled with the streamwise internal pressure wave. The numerical results indicate that the spanwise flow reduces the propagation speed of the internal pressure waves and the intensity of the corresponding pressure fluctuation.

Flow structure and unsteady fluctuation with separation over a two-dimensional backward-facing step

The flow over a backward-facing step (BFS) is a typical separation and reattachment flow. Its flow structures and unsteady mechanisms are still not well explored. In this paper, the global velocity fields of a BFS are obtained by a synchronous particle image velocimetry (PIV) system with Reh = 5 345 (Reynolds number) and Er = 2 (expansion ratio). Flow structures are distinguished and defined by the fraction of the negative velocity (upn). The reattachment zone (Lr) is quantitatively defined as (u0.9, u0.1) on the bottom wall. Spatial distribution of the large-scale vortices couples well with the divided flow structures and their temporal evolution presenting four stages (forming, developing, shedding and redeveloping) when travel downstream. The unsteady motions with various low frequencies are well explained by the coherent vortices and flow structures. Among the unsteady low frequency motions, the Kelvin Helmholtz (KH) vortices and the oscillation of Xr (OX) come likely from the free shear layer. The KH vortices contribute to the unsteadiness of the temporal flow, and the OX is the primary response to the vortical fluctuations.

Influence of air rifle pellet geometry on aerodynamic drag

Air rifles and air pistols find widespread use in formal and recreational sports events. Despite their widespread use in sport, they have rarely been studied scientifically. The influence of air rifle pellet geometry on aerodynamic drag was investigated experimentally and theoretically at Mach number of 0.58 (approximately 200 m/s) and Reynolds number of 54,000 using a low-turbulence open wind tunnel. Measurements were made of surface pressure and aerodynamic drag distribution for five pellets having different geometries. Pellet overall drag was also measured with a load cell system. Theoretical analysis based on two-dimensional potential flow theory was used to study the relationship between nose shape and drag. Results indicate that the overall drag of non-spherical pellets was dominated by the drag on their front face, with the face contributing approximately 65% of the overall pellet drag, while base drag contributed almost all of the remaining 35%. The net drag contribution of the pellet side-slopes was close to zero. The geometry of the front face had a weak influence on the drag acting on the pellet base. This influence was exercised through the behaviour of the free shear layer separating from the pellet head rim. It was apparent that the presence of the tail in a dome-head pellet enabled flow reattachment and a rise in base pressure, which reduced the base drag. In contrast, at Re ~54,000, flow reattachment on the rear surface of the spherical pellet was not possible. For this reason, its base drag was higher than that for the dome-head pellet. Flat-, cone-, and cavity-head pellets had higher overall drag coefficient values than a spherical pellet. The higher overall coefficients were due to the higher face drag than the spherical pellet, which was not compensated sufficiently by their lower base drag.

Effect of Piezo-Embedded Inverted Flag in Free Shear Layer Wake

The use of flexible inverted piezo embedded Polyvinylidene Difluoride (PVDF) as a simultaneous energy harvester and as a wake sensor is explored. The oscillation amplitude (characterized by voltage output) and oscillation frequency of the piezo-embedded PDVF was quantified in the wake of a 2D NACA 0012 model and SD7003 model at a Reynolds number of 100,000 and 67,000, respectively. The performance of the sensor was also quantified in the freestream without the presence of the wing. In order to quantify the sensor response to angle of attack and downstream distance, the amplitude and frequency of oscillations were recorded in the wing wake. Increase in angle of attack of the wing resulted in increase in oscillation frequency and amplitude of the PVDF. The results also indicated that the inverted flag configuration performed better in the wake under unsteady conditions when compared to freestream conditions. The results from Particle Image Velocimetry indicated that the wake signature was not affected by the presence of the PVDF in the wake. The root mean square voltage contours in the wake of SD7003 airfoil show remarkable free shear layer wake features such as upper and lower surface stratification and downwash angle which shows the sensitivity of the sensor to the unsteadiness in the wake. The capability of this device to act as a potential energy harvester and as a sensor has serious implications in extending the mission capabilities of small UAVs.

On the simulation of the flow around a circular cylinder at [formula omitted

The flow around a circular cylinder at Reynolds number of 1.4 × 105 is examined with Reynolds-Averaged Navier–Stokes equations (RANS) and Scale-Resolving Simulation (SRS) methods. Such problem is in the upper limit of the flow regime where turbulent transition occurs in the free shear-layers and so the flow dynamics is dominated by the spatial development of vortex-shedding structure, and in particular by the Kelvin–Helmholtz rollers and turbulence onset. The objectives of this investigation are threefold: (i) determine the aptitude of distinct RANS and SRS models to simulate the correct flow regime; (ii) compare the predictions of selected methods with available experimental measurements; and (iii) examine key modelling and flow features that contribute to the observed results. The evaluated models range from RANS supplemented with linear, transition, and non-linear turbulent viscosity closures, to hybrid and bridging SRS methods. Bridging computations are conducted at various constant degrees of physical resolution (range of resolved scales). The results illustrate the complexity of predicting the present flow problem. It is shown that RANS and SRS formulations modelling turbulence in boundary-layers with the selected linear turbulent viscosity closures lead to a premature onset of turbulence which alters the flow regime of the simulations. Although the transition and non-linear RANS closures can predict the correct flow regime, the outcome of this study indicates that solely the bridging model at constant physical resolution is able to achieve an accurate and physics-based prediction of the flow dynamics. Nonetheless, the necessary degree of physical resolution makes the numerical requisites of such computations demanding.