摘要 :
Lossy compression techniques are ubiquitous in many fields including imagery and video; however, the incursion of such lossy compression techniques in the computational fluid dynamics community has not advanced to the same extent ...
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Lossy compression techniques are ubiquitous in many fields including imagery and video; however, the incursion of such lossy compression techniques in the computational fluid dynamics community has not advanced to the same extent in decades. In this work, the lossy compression of high-fidelity direct numerical simulation (DNS) is evaluated to assess the impact on various parameters of engineering interest. A Mach 2.5, spatially developing turbulent boundary layer (SDTBL) at a moderately high Reynolds number has been selected as the subject of the study [1]. The ZFP compression scheme was chosen as the core driving algorithm for this study as it was carefully crafted for scientific, floating point data. The resilience of spectral quantities as well as two-point correlations is highlighted. Notwithstanding, we also noted that point-wise values calculated in the physical domain were prone to quantization errors at high compression ratios. Further, we have also presented the impact on higher order statistics. In summary, we have demonstrated that high fidelity results are within reach while achieving 1.45x to 9.82x reductions in required storage over single precision, IEEE 754-compliant data values.
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In the scenario of a curved hill, the main objective is to study a turbulent boundary layer for incoming horizontal turbulent airstream at 20 m/s by reproducing the wind-tunnel geometry as in [1]. A two-dimensional CFD RANS is per...
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In the scenario of a curved hill, the main objective is to study a turbulent boundary layer for incoming horizontal turbulent airstream at 20 m/s by reproducing the wind-tunnel geometry as in [1]. A two-dimensional CFD RANS is performed with scope in the curved hill where moderate and strong pressure gradients (both, favorable and adverse) are observed. We validate the incoming flow conditions with published Direct Numerical Simulation (DNS) and focus on comparisons with experimental data by Baskaran et al. [1] for the curved hill. The simulations leveraged the open-source software OpenFOAM® and compared two turbulence models, the K - ω SST and the Spalart-AUmaras. The thermal field is included and assumed a passive scalar (i.e., buoyancy forces are neglected). Additionally, the passive scalar transport (with a molecular Prandtl number of 0.71) is validated against DNS database at moderate Reynolds numbers. Further, identifying the edge of the boundary layer's edge becomes nontrivial under strong pressure gradients caused by wall curvature where the BL becomes significantly distorted and can experience strong acceleration/deceleration and higher peak velocities than that of the freestream. In the present work, we follow a more theoretical approach to identifying the edge of the boundary layer based on a potential flow solution in the same domain. This leads to more consistent results without the need for corrections considering pressure gradients. The results exhibit very good agreement with the data published by Baskaran et al. [1]. The SA model shows better agreement with the experimental baseline on wall parameters whereas the K - ω SST has a slight edge on the transition to the adverse pressure gradient (APG) region in terms of its wall pressure prediction which leads to a superior prediction of the separation point over the SA model, which possesses a small delay in this prediction. Nonetheless, the SA model exhibits a superior performance in the presence of strong surface curvature induced favorable pressure gradient (FPG) where, we hypothesize, the flow experiences a quasi-laminarization process. Nonetheless, more information is certainly required to confirm the presence (or lack thereof) of a laminarescent state at the top of the hill.
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Lagrangian Coherent Structures (LCS) have recently received a significant attention due to its advantages over Eulerian coherent structure identification schemes. Transport barriers and transport enhancers as material surfaces are...
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Lagrangian Coherent Structures (LCS) have recently received a significant attention due to its advantages over Eulerian coherent structure identification schemes. Transport barriers and transport enhancers as material surfaces are identified by LCS techniques and can be used to analyze turbulent mixing in many engineering applications. This study utilized high-fidelity Direct Numerical Simulation (DNS) databases of spatially-developing turbulent boundary layers (SDTBL) at the incompressible, supersonic (M_∞ = 2.5), and hypersonic (M_∞= 5) flow regimes. The main purpose is to qualitatively study the effects of flow compressibility and Reynolds number on LCS. Compressibility effects on turbulent coherent structures were observed to be weak, becoming more noticeable in the hypersonic regime for low Reynolds cases. Furthermore, the presence of hairpin vortices was scarce beyond y~+ = 100 (i.e., in the log-wake region) of hypersonic turbulent boundary layers. In contrast, the Reynolds number dependency on LCS was evident given by the high level of isotropization of turbulent coherent structures. Moreover, strong compressbility effects were observed once the Reynolds number was increased. This resulted in more abundant and more isotropic structures for high Reynolds supersonic flow.
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High-speed, compressible, turbulent boundary layers will be continue to gain relevance in many military, space and future civilian applications. However, furthering our understanding of crucial aspects of such flows present comple...
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High-speed, compressible, turbulent boundary layers will be continue to gain relevance in many military, space and future civilian applications. However, furthering our understanding of crucial aspects of such flows present complex computational challenges from the preparation to the execution of said simulations. For instance, a relatively modest DNS could generate 12-billion-data points with a simple geometry. This can be attributed in part to the resolution required to capture the smallest scales of motion at higher Reynolds numbers. More complex geometries could generate 16 TB of raw data. If more complex geometries are to be explored at higher Reynolds numbers, the need for scalable post-processing utilities will continue to increase at an exponential pace. Furthermore, present times have seen the advent of increasingly more heterogeneous and diversified computing infrastructure which adds significant complexity to the development of a portable solution. Consequently, we propose Aquila, a performance-portable, distributed library capable of handling the post-processing of large-scale simulations while alleviating the burden from the domain expert through a modern abstraction mechanism that hides unnecessary complexity from the application writer. Aquila builds over two major abstractions a distributed flow field and modular operations. The distributed flow field leverages both Kokkos and any distributed computing library wrapped around the Aquila Communicator interface. Kokkos enables Aquila to execute transparently and with performance portability on both CPUs and GPUs from multiple vendors while abstracting the distributed computing layer enables the adoption of virtually any distributed memory communication library although MPI is the only currently supported backend. Aquila is portable from laptop computers to supercomputers with no changes to the source code. In this paper, we present Aquila's design rationale and implementation details. A key distinction in Aquila's design is the scalable inclusion of out-of-core post-processing pipelines with data pre-fetch to give the illusion of in-memory availability of files. Furthermore, we show preliminary results, from a performance and usability point of view, on porting a post-processing analysis to Aquila.
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摘要 :
High-speed, compressible, turbulent boundary layers will be continue to gain relevance in many military, space and future civilian applications. However, furthering our understanding of crucial aspects of such flows present comple...
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High-speed, compressible, turbulent boundary layers will be continue to gain relevance in many military, space and future civilian applications. However, furthering our understanding of crucial aspects of such flows present complex computational challenges from the preparation to the execution of said simulations. For instance, a relatively modest DNS could generate 12-billion-data points with a simple geometry. This can be attributed in part to the resolution required to capture the smallest scales of motion at higher Reynolds numbers. More complex geometries could generate 16 TB of raw data. If more complex geometries are to be explored at higher Reynolds numbers, the need for scalable post-processing utilities will continue to increase at an exponential pace. Furthermore, present times have seen the advent of increasingly more heterogeneous and diversified computing infrastructure which adds significant complexity to the development of a portable solution. Consequently, we propose Aquila, a performance-portable, distributed library capable of handling the post-processing of large-scale simulations while alleviating the burden from the domain expert through a modern abstraction mechanism that hides unnecessary complexity from the application writer. Aquila builds over two major abstractions a distributed flow field and modular operations. The distributed flow field leverages both Kokkos and any distributed computing library wrapped around the Aquila Communicator interface. Kokkos enables Aquila to execute transparently and with performance portability on both CPUs and GPUs from multiple vendors while abstracting the distributed computing layer enables the adoption of virtually any distributed memory communication library although MPI is the only currently supported backend. Aquila is portable from laptop computers to supercomputers with no changes to the source code. In this paper, we present Aquila's design rationale and implementation details. A key distinction in Aquila's design is the scalable inclusion of out-of-core post-processing pipelines with data pre-fetch to give the illusion of in-memory availability of files. Furthermore, we show preliminary results, from a performance and usability point of view, on porting a post-processing analysis to Aquila.
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The use of dirigible or "zeppelin" airships in aerospace applications represents a promising avenue to explore. Although research of airships in academia might have passed below the radar of many, interest in adopting the dirigibl...
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The use of dirigible or "zeppelin" airships in aerospace applications represents a promising avenue to explore. Although research of airships in academia might have passed below the radar of many, interest in adopting the dirigible's floating concept has risen thanks to the development of the past 30 years in high-tech solar panels and materials. The following crucial advantages of dirigibles can be mentioned: i) great dynamic/static stability, ii) long flight duration, iii) vertical takeoff, iv) safe landing without the need of any structure to deploy, v) low energy consumption (amenable to solar power capabilities), to name a few. This manuscript explores the feasibility of a drone "dirigible-based carrier" for longer aircraft range, endurance, and environmental sustainability. In this study, we propose the aerodynamic design of a dirigible system able to transport several drones or Unmanned Aerial Vehicles (UAV). The purpose of the UAV Search & Rescue project at the University of Puerto Rico-Mayagiiez consists in the design, development and building of a UAV with autonomous self-piloting capable of locating a civilian in distress, autonomously land near the objective in case of need, signal position and coordinates and deliver supplies. In this opportunity, several aerodynamic concepts of "cigar-like" shape or axisymmetric design are scrutinized: one or multiple dirigibles (up to three structures). The first step involves selecting, analyzing, and optimizing the single dirigible structure. The second stage will evaluate the tandem configuration with two and three arrangements. The initial conceptual analysis will be performed via a CFD software and theoretical and empirical correlations available for the literature to calculate the aerodynamic forces (i.e., C_D and C_L and moments (C_m) over the dirigible-based carrier. The outcome expected is to achieve insight for a modular design that adjusts the "wetted area" configuration as a function of the desired payload.
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The widespread availability of high-performance commodity computing hardware has enabled technologies such as Virtual Reality and Augmented Reality to come out of research laboratories and enter the homes of many. Further, the wid...
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The widespread availability of high-performance commodity computing hardware has enabled technologies such as Virtual Reality and Augmented Reality to come out of research laboratories and enter the homes of many. Further, the widespread adoption of these technologies has caught the attention of the scientific community which is constantly researching potential applications. In the present study, we focus on applying virtual reality technologies as a scientific visualization tool. In particular, we show a virtual wind tunnel which enables the user to visualize complex and intricate turbulent flow patterns within an immersive environment. We also highlight potential research avenues within this particular area and present results for a sink flow DNS visualization.
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摘要 :
The widespread availability of high-performance commodity computing hardware has enabled technologies such as Virtual Reality and Augmented Reality to come out of research laboratories and enter the homes of many. Further, the wid...
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The widespread availability of high-performance commodity computing hardware has enabled technologies such as Virtual Reality and Augmented Reality to come out of research laboratories and enter the homes of many. Further, the widespread adoption of these technologies has caught the attention of the scientific community which is constantly researching potential applications. In the present study, we focus on applying virtual reality technologies as a scientific visualization tool. In particular, we show a virtual wind tunnel which enables the user to visualize complex and intricate turbulent flow patterns within an immersive environment. We also highlight potential research avenues within this particular area and present results for a sink flow DNS visualization.
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