Passive control of normal-shock-wave/boundary-layer interaction using porous medium: Computational study
05 Jun 2017-
About: The article was published on 2017-06-05. It has received 7 citations till now. The article focuses on the topics: Shock wave & Porous medium.
Citations
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08 Feb 2020
TL;DR: In this article, 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.
Abstract: 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.
8 citations
TL;DR: In this article, the relationship of the total oblique shock loss with the groove number is analyzed theoretically and numerically in entropy, and the physical mechanism for the generation of approximately parallel and divergent shockwave structures is understood and then the approximately parallel shock wave structure belongs to the same family with the divergent one.
8 citations
25 Jun 2018
3 citations
01 Jan 2020
TL;DR: In this paper, a sharp-interface immersed boundary method for compressible, turbulent flows and its application to transonic/supersonic flows is discussed, where the flow properties in the immediate neighbourhood of the immersed surface are reconstructed using inverse distance-based interpolation procedures.
Abstract: In this chapter, we discuss the development of a sharp-interface immersed boundary method for compressible, turbulent flows and its application to transonic/supersonic flows. A direct-forcing-type immersed boundary method is elucidated wherein the flow properties in the immediate neighbourhood of the immersed surface are reconstructed using inverse distance-based interpolation procedures. The flow is assumed to be locally parallel to the immersed surface, and the tangential velocity in the vicinity of the immersed surface is assumed to obey a power-law function of the local immersed surface normal. This approach helps in mimicking the energising effects of turbulent boundary layers without excessive mesh refinement near the immersed surface for suitable choices of the power-law coefficient. Temperature reconstruction is achieved from considerations of temperature variation in compressible thermal boundary layers, and density is estimated by either solving the continuity equation or by interpolation. The turbulence variables are reconstructed using law-of-the-wall-type approach. The application of the outlined immersed boundary method to the simulation of flow control devices is also discussed. Additionally, interpolation procedures for reconstructing the pressure and shear stress at the immersed surface and its application to simple cases are also presented. This information can be useful for comparison with experimental data, performing fluid–structure interaction studies, and also identifying flow-separation and re-attachment locations on the immersed surface.
3 citations
11 Jan 2021
1 citations
References
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TL;DR: In this paper, two new two-equation eddy-viscosity turbulence models are presented, which combine different elements of existing models that are considered superior to their alternatives.
Abstract: Two new two-equation eddy-viscosity turbulence models will be presented. They combine different elements of existing models that are considered superior to their alternatives. The first model, referred to as the baseline (BSL) model, utilizes the original k-ω model of Wilcox in the inner region of the boundary layer and switches to the standard k-e model in the outer region and in free shear flows. It has a performance similar to the Wilcox model, but avoids that model's strong freestream sensitivity
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