本文探討進行熱線探針測速儀進行的圓柱尾流實驗時，受限於探針必須伸入流場中進行速度量測，侵入式的探針支架有可能會影響圓柱尾流的發展進而影響到實驗結果的精確度。
使用大尺度渦流法(LES)模擬並比較兩種計算域，分別是傳統上僅包含圓柱之計算域以及同時包含圓柱與侵入式支架之計算域，並使用兩種雷諾數Re = 3856和Re = 9959於近尾流區比較模擬結果之平均速度以及方均根擾動速度，並利用比較結果說明陳威呈(2018)以PIV實驗結果與熱線測速儀實驗結果之差異性。
計算中次格點模型使用Dynamic Smagorinsky model；使用熱線測速儀在入口處所量測的結果作為入口條件，取代一般無擾動的均值入口；網格的建立依照實驗值推估流場中的泰勒尺度分布，作為建立網格時網格密度分布的設置參考。研究中可以發現同時考量圓柱和侵入式支架的計算域的模擬結果與僅考量圓柱所設置的計算域模擬結果在主流方向平均速度在非常上游處有明顯的速度差異，並且在頻譜圖上可以推測侵入式的支架確實有破壞流場發展的現象。

This study is aimed detecting the influence of an intrusive anemometer on cylindrical wake flow measurements by comparing the turbulence statistics between two computational domains, a domain with cylinder and a domain with a cylinder and an intrusive hot-wire anemometer (HWA). The numerical results of the domain with only the cylinder and the HWA experimental results are compared to verify the credibility of the numerical method. A numerical simulation is performed with the LES method and a sub-grid model of the dynamic Smagorinsky model (DSM) by imposing the measured boundary conditions, mainly for the near wake region for two cases, Re = 3856 and Re = 9959.
The strategy for setting the mesh size is dependent on the estimated Tylor micro scale obtained from the experimental results for the purpose of approaching the physical interpretation of the LES method. Based on the estimated Tylor micro scale, different mesh densities were set up in the shear-layer region for mesh identification, and the results for the recirculation bubble length using this method were found to be close to each mesh density in both cases. The numerical results of the domain with the cylinder were found to be in good agreement with the experimental results at x/d = 4 ~ 10.
The numerical results for the two different domains in terms of the stream-wise mean velocity value were obviously different. At the very near wake region(x/d = 2), the deviation in the value was 13.5% for Re = 3865 and 9.8% for Re = 9959. The deviation in the stream-wise velocity gradually decreased in the downstream region, where the deviation in stream-wise velocity value was 4.7% at x = 6d for Re = 3856.

Paper:
[1] Alam, Moriya, Takai, H Sakamoto. “Fluctuating fluid forces acting on two circular cylinders in a tandem arrangement at a subcritical Reynolds number”, Wind Engineering and Industrial Aerodynamics 91(1-2), pp. 139-154 (2003)
[2] Breuer, “Large eddy simulation of the subcritical flow past a circular cylinder: numerical and modeling aspects”, Numerical Methods in Fluids 28, pp. 1281-1302(1998)
[3]Box and MULLER, “A note on the generation of random normal deviates” (1958)
[4]Franke and Frank,“ Large Eddy Simulation of the flow past a circular cylinder at ReD=3900”, Wind Engineering and Industrial Aerodynamics 90, pp. 1191–1206 (2002)
[5] Fourier, J. B. J., “Analytical theory of heat”, ‎University of Cambridge (1822)
[6] Germano, Piomelli, Moin, and Cabot., “A dynamic Subgrid-Scale Eddy Viscosity Model” Physics of Fluids A: Fluid Dynamics 3, pp. 1760 (1991);
[7]Kim and Menon, “Application of the localized dynamic subgrid-scale model to turbulent wall-bounded flows”, 35th Aerospace Sciences Meeting and Exhibit (1997)
[8]Lilly, “A propose modification of Germano subgrid scale closure method”, Physics of Fluids A: Fluid Dynamics 4, pp. 633 (1992)
[9]Ong and Walaace, “The velocity field of the turbulent very near wake of a circular cylinder”, Experiments in Fluids 20, pp. 441-453 (1996)
[10] Parnaudeau, Carlier, Heitz, and Lamballais. “Experimental and Numerical Studies of the Flow over a Circular Cylinder at Reynolds Number 3900”, Physics of Fluids 20, 085101 (2008)
[11]Pope, “Ten Questions Concerning the Large-Eddy Simulation of Turbulent Flows”, New Journal of Physics 6, pp. 35 (2004)
[12] MA, KARAMANOS and KARNIADAKIS. “Dynamics and Low-Dimensionality of a Turbulent Near Wake”, J. Fluid Mech. 410, pp. 29–65(2000)
[13] Prsic, Ongb, Pettersena and Myrhauga. “Large Eddy Simulations of flow around a smooth circular cylinder in a uniform current in the subcritical flow regime”, Ocean Engineering 77, pp. 61–73 (2014)
[14]Smagorinsky, “General Circulation Experiments with the Primitive Equations I, The Basic Experiment”, Washington, D.C 91, num. 3 (1963)
[15]石昌隆, “Investigation of Velocity Measurement Technology in Turbulent Wake Over the Circular Cylinder.” (2015)
[16]陳威呈, “Development of Two-phase Velocity Measurement Using PIV Technique” (2018)
[17]姚立謙, “Analysis of Flow over a Cylinder by Large Eddy Simulation” (2016)
Books:
[18]ANSYS Inc., ANSYS FLUENT 13.0.0 User’s Guide. (2010)
[19]Sagaut, “Large Eddy Simulation for incompressible flows: An Introduction” (2002)
[20]Tennekes and Lumley, “A first course in Turbulence” (1970)