Micro vortex generator (MVG) is a currently facile, robust, and feasible device for supersonic and hypersonic flow control. The purpose of this study is to investigate the impact on SWBLI from the streamwise location of MVG. Large eddy simulation (LES) was conducted on MVG controlled supersonic ramp flow to reveal the sensitivity of MVG streamwise position on shock-wave boundary-layer interaction (SWBLI) control. Numerical cases with minor different distances between MVG and ramp corner are carried out. The results are analyzed in time-averaged and instantaneous view, respectively. The results show that streamwise position has a significant effect on SWBLI in some aspects. With minor changes on the streamwise position, the ring-like vortices generated by MVG were very similar, with only small changes in height and intensity. However, the small changes made on the ring-like vortices produced relatively significant changes to the separation region in front of the ramp. In terms of the time-averaged solution, the farther the MVG is from the ramp, the higher the ring-like vortices are lifted, and the shock wave is also disturbed/reduced more strongly. Further, the flow separation zone on the wall also appears smaller. The results of this study play a guiding role for further optimal configuration of MVG in flow control.
more »
« less
Modal Analysis on MVG Controlled Supersonic Flow at Different Mach Numbers
Modal analysis on micro-vortex generator (MVG)-controlled supersonic flow at different Mach numbers is performed in this paper. The purpose of this investigation is to clarify the different properties of streamwise and ring-like vortical modes, and the effects of different Mach numbers on these modes, to further understand the vortical structures as they travel from MVG down to the shock wave/boundary-layer interaction (SWBLI) region. To this end, a high order and high resolution large eddy simulation (LES) was carried out, which identified the vortical structures behind the MVG and in the shock wave/boundary-layer interaction (SWBLI) region in the supersonic ramp flow with flow speeds of three different Mach numbers 1.5, 2.0, and 2.5. The proper orthogonal decomposition (POD) then was adopted to investigate the modes of the fluctuation flow field. It emerged that the streamwise and ring-like vortical modes were disparate in energy distribution, structural order, frequency and amplitude. Furthermore, it showed that as the Mach number increased, the energy of the streamwise modes increased while the opposite was true for ring-like modes; and the streamwise modal structures were altered more significantly than the ring-like modes, and the frequency of each mode scarcely varied. It was also found that the streamwise vortices absorbed energy from the ring-like vortices while they traveled from the MVG down to the SWBLI region, but the dominant frequency of each mode rarely changed during this process.
more »
« less
- Award ID(s):
- 1912191
- NSF-PAR ID:
- 10412275
- Date Published:
- Journal Name:
- Processes
- Volume:
- 10
- Issue:
- 8
- ISSN:
- 2227-9717
- Page Range / eLocation ID:
- 1456
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)The instability and transition to turbulence and its evolution in pulsatile flows, which involve reverse flows and unsteady flow separations, is the primary focus of this experimental work. A piston driven by a programmable DC servo motor was used to set-up a water flow system and provide the pulsation characteristics. Time-resolved particle image velocimetry data were acquired in a refractive index matching set-up by using a continuous wave laser and a high-frame-rate digital camera. The position of the piston was continuously recorded by a laser proximity sensor. Five different experiments were carried out with Reynolds numbers in the range of 535–4825 and Womersley numbers from 11.91 to 23.82. The non-stationarity of the data was addressed by incorporating trend removal methods involving low- and high-pass filtering of the data, and using empirical mode decomposition together with the relevant Hilbert–Huang transform to determine the intrinsic mode functions. This latter method is more appropriate for nonlinear and non-stationary cases, for which traditional analysis involving classical Fourier decomposition is not directly applicable. It was found that transition to turbulence is a spontaneous event covering the whole near-wall region. The instantaneous vorticity profiles show the development of a large-scale ring-like attached wall vortical layer (WVL) with smaller vortices of higher frequencies than the pulsation frequency superimposed, which point to a shear layer Kelvin–Helmholtz (K–H) type of instability. Inflectional instability leads to flow separation and the formation of a major roll-up structure with the K–H vortices superimposed. This structure breaks down in the azimuthal direction into smaller turbulence patches with vortical content, which appears to be the prevailing structural content of the flow at each investigated Reynolds number ( Re ). At higher Re numbers, the strength and extent of the vortices are larger and substantial disturbances appear in the free stream region of the flow, which are typical of pipe flows at transitional Re numbers. Turbulence appears to be produced at the locations of maximum or minimum vorticity within the attached WVL, in the ridges between the K–H vortices around the separated WVL and the upstream side of the secondary vortex where the flow impinges on the wall. This wall turbulence breaks away into the middle section of the pipe, at approximately $Re \ge 2200$ , by strong eruptions of the K–H vortices.more » « less
-
null (Ed.)Flight vehicles that operate in the supersonic regime can be subject to adverse fluid-structure interactions due to their lightweight design. The presence of geometric obstructions such as control surfaces or fins can induce compression shocks that can interact with the boundary layer, leading to flow separation. The interaction of flow, compression shock and structural dynamics is very difficult to model and currently only poorly understood. This work investigates experimentally the interaction between a compliant panel in a Mach 2 flow under a ramp-induced shock-wave/boundary layer interaction (SWBLI). Brass panels of length 4.8" and width 2.5" and different thicknesses (h=0.020", 0.016", 0.012" and 0.010") are investigated. Tests are performed both with and without a compression ramp installed. This direct comparison allows characterization of the effect of the SWBLI on the system dynamics. High-speed stereoscopic digital image correlation (DIC) and fast-response pressure sensitive paint (PSP) are used to obtain simultaneous full field deformation and surface pressure of the panels. The results show that the shock induced by the 20compression ramp leads to separation of the turbulent boundary layer close to the ramp starting at about 80% of the panel length. This results in a region of large pressure fluctuations which primarily increase the vibration amplitude of the second panel mode. Analysis of the fundamental mode, which contains most of the vibration energy of the panel, shows that the SWBLI does not lead to changes of this mode, neither in frequency, amplitude or mode shape. On the other hand, analysis of the shock foot motion shows that the shock primarily oscillates at the fundamental frequency of the panel. This means that while the shock and panel oscillate at the same frequency, it is not two-way coupling. The panel vibration dictates the motion of the shock, but the shock (or rather the SWBLI) does not modify the fundamental panel vibration beyond the forcing provided by the turbulent boundary layer. Full field surface pressure predictions are made using linearized potential flow theory, which relates the local slope of the panel to the surface pressure. Results are found to be in good agreement in the region of attached flow.more » « less
-
In this work, we introduce a scalable and efficient GPU-accelerated methodology for volumetric particle advection and finite-time Lyapunov exponent (FTLE) calculation, focusing on the analysis of Lagrangian Coherent Structures (LCS) in large-scale Direct Numerical Simulation (DNS) datasets across incompressible, supersonic, and hypersonic flow regimes. LCS play a significant role in turbulent boundary layer analysis, and our proposed methodology offers valuable insights into their behavior in various flow conditions. Our novel owning-cell locator method enables efficient, constant-time cell search, and the algorithm draws inspiration from classical search algorithms and modern multi-level approaches in numerical linear algebra. The proposed method is implemented for both multi-core CPUs and Nvidia GPUs, demonstrating strong scaling up to 32,768 CPU cores and up to 62 Nvidia V100 GPUs. By decoupling particle advection from other problems, we achieve modularity and extensibility, resulting in consistent parallel efficiency across different architectures. Our methodology was applied to calculate and visualize the FTLE on four turbulent boundary layers at different Reynolds and Mach numbers, revealing that coherent structures grow more isotropic proportional to the Mach number, and their inclination angle varies along the streamwise direction. We also observed increased anisotropy and FTLE organization at lower Reynolds numbers, with structures retaining coherency along both spanwise and streamwise directions. Additionally, we demonstrated the impact of lower temporal frequency sampling by upscaling with an efficient linear upsampler, preserving general trends with only 10% of the required storage. In summary, we present a particle search scheme for particle advection workloads in the context of visualizing LCS via FTLE that exhibits strong scaling performance and efficiency at scale. Our proposed algorithm is applicable across various domains requiring efficient search algorithms in large structured domains. While this manuscript focuses on the methodology and its application to LCS, an in-depth study of the physics and compressibility effects in LCS candidates will be explored in a future publication.more » « less
-
more » « less
In this work, we introduce a scalable and efficient GPU-accelerated methodology for volumetric particle advection and finite-time Lyapunov exponent (FTLE) calculation, focusing on the analysis of Lagrangian coherent structures (LCS) in large-scale direct numerical simulation (DNS) datasets across incompressible, supersonic, and hypersonic flow regimes. LCS play a significant role in turbulent boundary layer analysis, and our proposed methodology offers valuable insights into their behavior in various flow conditions. Our novel owning-cell locator method enables efficient constant-time cell search, and the algorithm draws inspiration from classical search algorithms and modern multi-level approaches in numerical linear algebra. The proposed method is implemented for both multi-core CPUs and Nvidia GPUs, demonstrating strong scaling up to 32,768 CPU cores and up to 62 Nvidia V100 GPUs. By decoupling particle advection from other problems, we achieve modularity and extensibility, resulting in consistent parallel efficiency across different architectures. Our methodology was applied to calculate and visualize the FTLE on four turbulent boundary layers at different Reynolds and Mach numbers, revealing that coherent structures grow more isotropic proportional to the Mach number, and their inclination angle varies along the streamwise direction. We also observed increased anisotropy and FTLE organization at lower Reynolds numbers, with structures retaining coherency along both spanwise and streamwise directions. Additionally, we demonstrated the impact of lower temporal frequency sampling by upscaling with an efficient linear upsampler, preserving general trends with only 10% of the required storage. In summary, we present a particle search scheme for particle advection workloads in the context of visualizing LCS via FTLE that exhibits strong scaling performance and efficiency at scale. Our proposed algorithm is applicable across various domains, requiring efficient search algorithms in large, structured domains. While this article focuses on the methodology and its application to LCS, an in-depth study of the physics and compressibility effects in LCS candidates will be explored in a future publication.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/pr10081456
