Newsletter  2020.2  Index

Theme : "The Conference of Fluid Engineering Division (February issue)” Preface T. HASHIMOTO，S. MATSUDA，H.J. PARK Moving-boundary problems in rarefied gas dynamics Tetsuro TSUJI (Kyoto University) Flow Control of Jets and Separated Flows Toshihiko SHAKOUCHI (Mie University) Machine-learned three-dimensional super-resolution analysis of turbulent channel flow Kai FUKAMI, Koji FUKAGATA (Keio University), and Kunihiko TAIRA (UCLA) Flow control around an oscillating square cylinder by using plasma actuators Chihiro ONAHA (Toyohashi University of Technology) Dream to Sounds Takumi FUKUSHIMA (Tokyo University of science)

 

Flow Control of Jets and Separated Flows

Toshihiko SHAKOUCHI, Mie University

Abstract

This is a summary of the keynote lecture addressed above at “The Conference of Fluid Engineering Division, 2019, JSME”.

Jets, wakes and separated flows are fundamentally and practically important phe- nomena in the field of fluid dynamics and engineering because they include free or wall boundary layer flow, shear flow, vortex flow, mixing and diffusion of flow, etc.^{(1), (2)}. In this article, some examples of the controls of jet diffusion, jet noise and thrust vectoring, and flow separation are described.

The flow control is performed to obtain a desired optimal flow condition for a flow flowing around or through an object. Flow control method includes passive and

active flow control methods (Fig.1). Passive flow control is performed by changing flow path shape slightly or using tabs, ribs and turbulence prompters without applying external energy. Passive flow control is a simple and economical method, but, in order to control a more complicated or constantly changing flow, it is necessary to use an active flow control method. Active flow control includes Feedback flow control and Feedforward flow control which estimates the effect of flow disturbance and corrects it in advance. For these active flow controls, it is necessary to grasp the flow condition, setting of flow control target, sensors and sensing technologies, actuator, data collection method and device, and control method and theory, and to do them at a high level requires understanding and implementation of computers, programming, control technology, IT (information technology), and AI (artificial intelligence), etc.   

Table 1 shows the items of the contents, and some examples of flow control are shown. For example, the effects of nozzle configuration or tabs, ribs and turbulence promoters set at the nozzle exit on the flow characteristics of jet flow, jet noise reduction by chevron nozzle, globular formation of fine solid particle, toner for copy machine, by a hot gas jet, flow control of main jet by sub-, small-, synthetic- and plasma jets, NOTAR, no tail rotor helicopter, enhancement of lift force by BLC, and fluidic vector control of sub- and supersonic jets, are introduced and the flow control methods were discussed.

Key words

Flow control, Passive and active flow controls, Jet flows, Separated flows, Wake flows

Figures

Fig.1 Classification of flow control method

Table 1 Contents

Reference

(1)	Klar, L.D., “Active flow control technology”, ASMR Fluids Engineering Div. Technical Brief (1998), pp.1-28.
(2)	Shakouchi, T., “Passive flow control of jets”, Mechanical Engineering Review, JSME, Vol. 7, No. 1 (2020), p.19-00386