Understanding and control of wake vortices past a circular cylinder is a cardinal problem of interest to ocean engineering.The wake formation and vortex shedding behind a variety of ocean structures such as spars,are ...Understanding and control of wake vortices past a circular cylinder is a cardinal problem of interest to ocean engineering.The wake formation and vortex shedding behind a variety of ocean structures such as spars,are subjected to fatigue failure limiting their life span.The additional influences due to ocean waves and currents further exacerbate these effects.In the present study,flow past an isolated circu-lar cylindrical structure subjected to an oscillatory upstream are numerically investigated.These studies involve high resolution simulations over the low Reynolds number range(100-200).Although the prac-tical range of interest is in high Reynolds number range of 103-105,the flow physics and a number of qualitative and quantitative aspects are similar to the low Reynolds number flows.In the high Reynolds number range,statistical averaging tools in conjunction with suitable closure models would be neces-sary.The control of wake vortices is achieved with the aid of two small rotors located in the aft of the main cylinder.A control algorithm was coupled to determine the quantum of actuation to the rotating elements.Although control of wake vortices was observed for harmonic in-let forcing,residual vortical structures were found to persist at higher amplitudes of oscillation.To study the efficacy of this control,numerical simulations were further extended,when the circular cylinder was flexibly mounted.The con-trol of flow induced vibrations was observed to be reasonably effective in controlling the wake generated behind the main cylinder due to oscillatory upstream.展开更多
Smoothed Particle Hydrodynamics (SPH) is fast emerging as a practically usefulcomputational simulation tool for a wide variety of engineering problems. SPH isalso gaining popularity as the back bone for fast and reali...Smoothed Particle Hydrodynamics (SPH) is fast emerging as a practically usefulcomputational simulation tool for a wide variety of engineering problems. SPH isalso gaining popularity as the back bone for fast and realistic animations in graphicsand video games. The Lagrangian and mesh-free nature of the method facilitates fastand accurate simulation of material deformation, interface capture, etc. Typically,particle-based methods would necessitate particle search and locate algorithms tobe implemented efficiently, as continuous creation of neighbor particle lists is acomputationally expensive step. Hence, it is advantageous to implement SPH, on modernmulti-core platforms with the help of High-Performance Computing (HPC) tools. Inthis work, the computational performance of an SPH algorithm is assessed on multicore Central Processing Unit (CPU) as well as massively parallel General PurposeGraphical Processing Units (GP-GPU). Parallelizing SPH faces several challenges suchas, scalability of the neighbor search process, force calculations, minimizing threaddivergence, achieving coalesced memory access patterns, balancing workload, ensuringoptimum use of computational resources, etc. While addressing some of these challenges,detailed analysis of performance metrics such as speedup, global load efficiency, globalstore efficiency, warp execution efficiency, occupancy, etc. is evaluated. The OpenMP andCompute Unified Device Architecture (CUDA) parallel programming models have beenused for parallel computing on Intel Xeon(R) E5-2630 multi-core CPU and NVIDIAQuadro M4000 and NVIDIA Tesla p100 massively parallel GPU architectures. Standardbenchmark problems from the Computational Fluid Dynamics (CFD) literature are chosen for the validation. The key concern of how to identify a suitable architecturefor mesh-less methods which essentially require heavy workload of neighbor search andevaluation of local force fields from neighbor interactions is addressed.展开更多
文摘Understanding and control of wake vortices past a circular cylinder is a cardinal problem of interest to ocean engineering.The wake formation and vortex shedding behind a variety of ocean structures such as spars,are subjected to fatigue failure limiting their life span.The additional influences due to ocean waves and currents further exacerbate these effects.In the present study,flow past an isolated circu-lar cylindrical structure subjected to an oscillatory upstream are numerically investigated.These studies involve high resolution simulations over the low Reynolds number range(100-200).Although the prac-tical range of interest is in high Reynolds number range of 103-105,the flow physics and a number of qualitative and quantitative aspects are similar to the low Reynolds number flows.In the high Reynolds number range,statistical averaging tools in conjunction with suitable closure models would be neces-sary.The control of wake vortices is achieved with the aid of two small rotors located in the aft of the main cylinder.A control algorithm was coupled to determine the quantum of actuation to the rotating elements.Although control of wake vortices was observed for harmonic in-let forcing,residual vortical structures were found to persist at higher amplitudes of oscillation.To study the efficacy of this control,numerical simulations were further extended,when the circular cylinder was flexibly mounted.The con-trol of flow induced vibrations was observed to be reasonably effective in controlling the wake generated behind the main cylinder due to oscillatory upstream.
文摘Smoothed Particle Hydrodynamics (SPH) is fast emerging as a practically usefulcomputational simulation tool for a wide variety of engineering problems. SPH isalso gaining popularity as the back bone for fast and realistic animations in graphicsand video games. The Lagrangian and mesh-free nature of the method facilitates fastand accurate simulation of material deformation, interface capture, etc. Typically,particle-based methods would necessitate particle search and locate algorithms tobe implemented efficiently, as continuous creation of neighbor particle lists is acomputationally expensive step. Hence, it is advantageous to implement SPH, on modernmulti-core platforms with the help of High-Performance Computing (HPC) tools. Inthis work, the computational performance of an SPH algorithm is assessed on multicore Central Processing Unit (CPU) as well as massively parallel General PurposeGraphical Processing Units (GP-GPU). Parallelizing SPH faces several challenges suchas, scalability of the neighbor search process, force calculations, minimizing threaddivergence, achieving coalesced memory access patterns, balancing workload, ensuringoptimum use of computational resources, etc. While addressing some of these challenges,detailed analysis of performance metrics such as speedup, global load efficiency, globalstore efficiency, warp execution efficiency, occupancy, etc. is evaluated. The OpenMP andCompute Unified Device Architecture (CUDA) parallel programming models have beenused for parallel computing on Intel Xeon(R) E5-2630 multi-core CPU and NVIDIAQuadro M4000 and NVIDIA Tesla p100 massively parallel GPU architectures. Standardbenchmark problems from the Computational Fluid Dynamics (CFD) literature are chosen for the validation. The key concern of how to identify a suitable architecturefor mesh-less methods which essentially require heavy workload of neighbor search andevaluation of local force fields from neighbor interactions is addressed.
