低速平面噴流在長波與主頻雙頻激擾下之流場量測研究

Experimental Study of a Low-speed Plane Jet under Long-wave and Fundamental Forcing

葉泳蘭(Yung-Lan Yeh)

《航空太空及民航學刊.系列B》 43卷2期 (2011/10) Pp. 117-123

https://doi.org/10.6124/JAAA.201110_43(2).07

摘要

本研究主要以實驗量測之法探討平面噴流在長波與主頻激擾下的流場演變，目的在了解流場由上游具主頻特徵的結構過渡至下游區大尺度長波的過程。實驗中，噴流出口操作流速固定為10m/sec，基於出口高度（H=12mm）為特徵長度之雷諾數為ReH=8.2 10^3，長波激擾（fe=10Hz和5Hz）與主頻（f0= 480Hz）為本研究的主要操作頻率，主要的速度量測設備為十字型定溫熱線測速儀。頻譜結果顯示，經過主頻激擾後的流場至等勢核末端之主導頻率為顯著頻率（f0/4），在雙模激擾下，長波激擾之低頻會取代顯著頻率而成下游區的主導頻率。雙模激擾之混合與擴展特性結果除在近場與單純長波激擾比較有增加外，遠場區之結果與長波激擾之結果相當近似。

關鍵字

平面噴流 ； 長波激擾 ； 雙模激擾

並列摘要

The flow field evolutions of a plane jet under long-wave and fundamental forcing are studied experimentally in this study. The process of fundamental mode in the upstream transit to long-wave mode in the far field is the main purpose. The exit speed is fix at 10m/sec and the Reynolds number based on nozzle height is ReH=8.2×10^3. Excitation frequency of long-wave forcing is 10 and 5Hz and fundamental forcing is 480Hz with constant intensity. The cross-type of constant temperature hot-wire anemometer is adopted for velocity measurement. Results reveal that the dominat frequency after the end of potential core of fundamental excited jet is prefereed mode (f0/4)，but it will be suppressed when bi-mode forcing. Furthermore, the properties of mixing and spreading of bi-mode forcing increase in the near field and similar to the results of long-wave forcing.

並列關鍵字

Plane jet ； Long-wave ； Bi-mode