Numerical modelling of shock wave-boundary layer interaction control by passive wall ventilation

Szulc, Oskar; Doerffer, Piotr; Flaszyński, Paweł; Suresh, T.

doi:10.1016/j.compfluid.2020.104435

Cited by 16 publications

(8 citation statements)

References 9 publications

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“…However, in all the slot and flap controlled cases, the flow fields downstream of the SBLIs were found to have high levels of turbulence compared to the predominantly two-dimensional flow over the conventional porous surfaces. Szulc et al (2018) also found that in the presence of surface ventilation, the normal shock transforms into a new structure. This type of shock structure is based on the relative length of the cavity which might either lead to a large lambda-foot structure (classical cavity), or to a sequence of oblique waves (extended cavity with larger aspect ratios), or to a gradual compression [19].…”

Section: Introductionmentioning

confidence: 90%

“…This type of shock structure is based on the relative length of the cavity which might either lead to a large lambda-foot structure (classical cavity), or to a sequence of oblique waves (extended cavity with larger aspect ratios), or to a gradual compression [19]. It was also proposed by Szulc et al (2016), that the transformation of this normal shock forced by an extended cavity of large aspect ratio leads to noise reduction for high-speed impulsive helicopter rotors [20]. Compared to the other SBLI shock control techniques, the wall-ventilation through a shallow cavity has shown a considerable increase in losses due to boundary layer thickening.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Wall Ventilation on the Shock-wave/Viscous-Layer Interactions in a Mach 2.2 Intake

et al. 2020

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In order to achieve proficient combustion with the present technologies, the flow through an aircraft intake operating at supersonic and hypersonic Mach numbers must be decelerated to a low-subsonic level before entering the combustion chamber. High-speed intakes are generally designed to act as a flow compressor even in the absence of mechanical compressors. The reduction in flow velocity is essentially achieved by generating a series of oblique as well as normal shock waves in the external ramp region and also in the internal isolator region of the intake. Thus, these intakes are also referred to as mixed-compression intakes. Nevertheless, the benefits of shock-generated compression do not arise independently but with enormous losses because of the shockwave and boundary layer interactions (SBLIs). These interactions should be manipulated to minimize or alleviate the losses. In the present investigation a wall ventilation using a new cavity configuration (having a cross-section similar to a truncated rectangle with the top wall covered by a thin perforated surface is deployed underneath the cowl-shock impinging point of the Mach 2.2 mixed-compression intake. The intake is tested for four different contraction ratios of 1.16, 1.19, 1.22, and 1.25, with emphasis on the effect of porosity, which is varied at 10.6%, 15.7%, 18.8%, and 22.5%. The introduction of porosity on the surface covering the cavity has been proved to be beneficial in decreasing the wall static pressure substantially as compared to the plain intake. A maximum of approximately 24.2% in the reduction in pressure at the upstream proximal location of 0.48 L is achieved in the case of the wall-ventilated intake with 18.8% porosity, at the contraction ratio of 1.19. The Schlieren density field images confirm the efficacy of the 18.8% ventilation in stretching the shock trains and in decreasing the separation length. At the contraction ratios of 1.19, 1.22, and 1.25 (‘dual-mode’ contraction ratios), the controlled intakes with higher porosity reduce the pressure gradients across the shockwaves and thereby yields an ‘intake-start’ condition. However, for the uncontrolled intake, the ‘unstart’ condition emerges due to the formation of a normal shock at the cowl lip. Additionally, the cowl shock in the ‘unstart’ intake is shifted upstream because of higher downstream pressure.

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Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Effects of Wall Ventilation on the Shock-wave/Viscous-Layer Interactions in a Mach 2.2 Intake

et al. 2020

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“…So far, a few SWBLI flow control methods have been developed and can generally be divided into passive and active groups. The former group usually includes placing bumps, [4][5][6][7] micro vortex generators, 8,9 and cavities [10][11][12][13][14][15] at some specific positions to adjust the local energy distribution in the flow field without importing any external energy. In the latter group, the boundary layer suction [16][17][18][19][20] and blowing 21,22 techniques are most common, which require extra energy expenditure to some degree.…”

Section: Introductionmentioning

confidence: 99%

“…However, to the authors’ acknowledgment, nearly all the available relevant literature indicates that cavity tends to thicken the outside boundary layer and leads to the growth of viscous loss. Cavity is thus more commonly used in flat plate, 10,11 supersonic intake, 12 airfoil, 13,14 and compressor cascade 15 but is rarely seen to be applied in the compressor rotor. Kerrebrock, 17 according to the authors, was the first to introduce and apply the active boundary layer aspiration technique to the axial fan/compressor.…”

Section: Introductionmentioning

confidence: 99%

Combined application of passive and active boundary layer aspiration in a transonic compressor rotor for shock wave/boundary layer interaction control

Zhou

Zhao

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part G:

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Shock wave/boundary layer interaction (SWBLI) is one of the key factors that limits the improvement of aerodynamic performance and stability for supersonic/transonic compressors. In this research, a combined flow control device (CFCD) was designed for controlling SWBLI in the NASA transonic compressor Rotor 35. The original flow fields for Rotor 35 were numerically analyzed first. The results show that the SWBLI is severe, resulting in much flow loss and partly leading to the compressor instability. Based on this phenomenon, the CFCD was designed with a novel three-dimensional passive self-recirculation flow channel and an active suction slot. The flow channel is mounted on the rotor blade suction surface to connect the low- and high-pressure regions ahead of and behind the shock, respectively. The effect of the CFCD on the rotor performance and corresponding working mechanism are then researched as well. With the help of CFCD, the rotor-achieved total pressure ratio (TPR) is maximally increased by 3.0%, and the stall margin (SM) is improved by 4.1% as well. But the rotor isentropic efficiency (IE) considering additional energy expenditure caused by active suction flow has the maximum increment at choke point of 0.27% and highest reduction at near-stall point of 0.54%. The working mechanisms of CFCD include two aspects: one is forming a stable and low-entropy generated lambda shock wave and the other one is reducing the magnitude of flow separation. The dominant mechanism varies with the rotor working condition and depends on whether the leading-edge shock moves upstream of the passive bleed slot.

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“…One among such a flow field is supersonic flow past a confined cavity [19][20][21][22] . Mixed-compression inlet for shock-wave boundary layer control 23,24 , resonator type supersonic nozzles 25,26 , gas-dynamic lasers 27,28 , and scram-jet combustors 29,30 often employ cavities in supersonic flow which are placed in closed proximity to the surrounding walls. Aerodynamic testing facilities like the wind-tunnel facilities aim to study the multipurpose bay-door interaction with freestream, as seen in supersonic aircraft, by modeling the system as a cavity on the test-section wall [31][32][33][34] .…”

Section: Introductionmentioning

confidence: 99%

Shock and shear layer interaction in a confined supersonic cavity flow

Karthick

2021

Preprint

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The impinging shock of varying strengths on the free shear layer in a confined supersonic cavity flow is studied numerically using the detached-eddy simulation. The resulting spatiotemporal variations are analyzed between the different cases using unsteady statistics, x − t diagrams, spectral analysis, and modal decomposition. A confined passage height of H/D = 2 and a cavity of length to depth ratio L/D = 2 at a freestream Mach number of M ∞ = 1.71 is considered. Impinging shock strength is controlled by changing the ramp angle (θ ) on the top-wall. The static pressure change across the impinging shock (p 2 /p 1 ) is used to quantify the shock strength. Five different cases are realized: [p 2 /p 1 ] = 1.0, 1.2, 1.5, 1.7 and 2.0. At [p 2 /p 1 ] = 1.5, fundamental fluidic mode or Rossiter's frequency corresponding to n = 1 mode vanishes whereas frequencies correspond to higher modes (n = 2 and 4) resonate. Wavefronts interaction from the longitudinal reflections inside the cavity with the transverse disturbances from the shock-shear layer interactions is identified to drive the strong resonant behavior. Due to Mach-reflections inside the confined passage at [p 2 /p 1 ] = 2.0, shock-cavity resonance is lost. Besides, the cavity wall experiences a higher pressure of 25% for [p 2 /p 1 ] = 1.0 due to shock loading. Based on the present findings, an idea to use a shock-laden confined cavity flow in an enclosed supersonic wall-jet configuration as passive flow control or a fluidic device is also demonstrated.

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Numerical modelling of shock wave-boundary layer interaction control by passive wall ventilation

Cited by 16 publications

References 9 publications

Effects of Wall Ventilation on the Shock-wave/Viscous-Layer Interactions in a Mach 2.2 Intake

Effects of Wall Ventilation on the Shock-wave/Viscous-Layer Interactions in a Mach 2.2 Intake

Combined application of passive and active boundary layer aspiration in a transonic compressor rotor for shock wave/boundary layer interaction control

Shock and shear layer interaction in a confined supersonic cavity flow

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