Abstract
For a micro-gap rotational flow field with a large horizontal extent, tiny gap and fast flow velocity, the two-dimensional images shot by the micro-scale Particle ImageVelocimetry(Micro-PIV) technique are not sufficient for the study of local or whole flow characteristics. In this paper, by establishing a test bench of a rotational flow field with the functions of driving, positioning, adjustment and sensing, all the local states of the micro-gap rotational flow field can be obtained by horizontally moving the rotating axis to observe point by point. While measuring some local flow fields, two-dimensional pictures are taken by adjusting the focusing height of the objective lens, and then superposed and interpolated according to their shooting order to obtain a quasi-three-dimensional distribution image of the local flow fields, thus obtaining the flow condition of the vertical section of the flow field. The position of the focusing plane and mutual distance are adjusted to realize the measurement of wall shear force in the flow field, providing a feasible reference method for detecting the rheological property of the gap flow field and the effect of surface drag reduction.
Highlights
INTRODUCTIONExtensive and in-depth studies have been done on rotating mechanical structures, and among them, the rotational flow field between two coaxial discs has been the focus of study due to its complicated rules and extensive uses.There are various forms, such as the stator– rotor structure or rotor–rotor structure with an enclosed cavity or open type channel flow, which have been widely applied in turbine engines, gas-liquid mixing exchangers and fluidized beds, etc
The position of the focusing plane and mutual distance are adjusted to realize the measurement of wall shear force in the flow field, providing a feasible reference method for detecting the rheological property of the gap flow field and the effect of surface drag reduction
Extensive and in-depth studies have been done on rotating mechanical structures, and among them, the rotational flow field between two coaxial discs has been the focus of study due to its complicated rules and extensive uses.There are various forms, such as the stator– rotor structure or rotor–rotor structure with an enclosed cavity or open type channel flow, which have been widely applied in turbine engines, gas-liquid mixing exchangers and fluidized beds, etc
Summary
Extensive and in-depth studies have been done on rotating mechanical structures, and among them, the rotational flow field between two coaxial discs has been the focus of study due to its complicated rules and extensive uses.There are various forms, such as the stator– rotor structure or rotor–rotor structure with an enclosed cavity or open type channel flow, which have been widely applied in turbine engines, gas-liquid mixing exchangers and fluidized beds, etc. This paper focuses on the special structure of a liquid-floated rotor gyroscope, that is, to fill in a layer of 100–300μm thin liquid flow film between the rotating surface and the static horizontal plane of the cavity.The main characteristics of the flow field are the non-equivalence of the three-dimensional size with a large horizontal extent, tiny gap and fast flow velocity.As macroscopic non-contact testing methods are not applicable to this flow field, the Micro-PIV testing technique provides a method to solve the problem. The shooting field of view with Micro-PIV is too small to observe the whole flow in the horizontal surface; and the fluid flow states are different at the vertical positions of the gap, so a single shooting cannot represent the whole flow conditions of the gap.
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