Coupling Flow Of Jet Impinging On Rotating Wall

The jet impact rotating wall surface is mainly used in the heating or cooling field of various machinery,such as metal annealing,glass tempering,turbine blade cooling,avionics cooling,electronic packaging,and vapor deposition.The flow characteristics are the fundamental factors affecting the noise mechanism and heat transfer characteristics.Therefore,it is of great engineering application background and academic value to study the coupled flow of jet impinging on the rotating wall.In this paper,the method of combining numerical calculation and PIV experiment is used to study the flow characteristics and impact pressure of the jet impacting the rotating wall under different parameters.The research parameters include Reynolds number Re,impact height H,wall speed n and pulse period T.The main findings are as follows:(1)The numerical calculation and PIV experimental study of the continuous jet impacting the static wall under different Reynolds numbers and impact heights show that the jet flow structure depends on the impact height and is relatively independent of Reynolds number.As the impact height increases,the degree of diffusion of the jet reaching the impact zone gradually increases,and its velocity gradually decreases.The pressure coefficient on the impact wall is mainly concentrated in the impact area within the range of-2?x/D?2.As the impact height increases,the maximum pressure coefficient gradually decreases,and the rate of decrease gradually increases;the dimensionless pressure distribution is almost unchanged.(2)The erosion characteristics of continuous impact jets under different Reynolds numbers and impact heights were studied by sand erosion experiments,and it was found that with the increase of impact height,the range of sand pits formed obviously increased,but the width of sand dunes did not change significantly;The dunes are approximately circular,with similar widths at different locations.With the increase of Reynolds number,the width of the sand pit and the width of the sand dune showed an upward trend,while the extreme value of the sand pit and the extreme value of the sand dune fluctuated.(3)The numerical calculation of the continuous jet impinging on the rotating wall under different wall speeds is carried out,and it is found that the wall rotation mainly affects the wall jet area,but has little effect on the free jet area and the impact area.As the rotational speed of the disk increases,the vortex center gradually approaches the wall of the disk until it reaches the edge of the disk;The radial component and the circumferential component of the velocity near the wall at larger radial distances gradually increase linearly.The disc rotation speed does not affect the impact pressure coefficient distribution in the center area of the disc.(4)The numerical calculation of the continuous jet impacting the rotating wall at different impact heights shows that with the increase of the impact height,the flow structure near the wall area remains basically unchanged,and the flow away from the impact wall gradually becomes irregular and vortices appear structure;When the radial distance is small,the maximum value of the radial component of velocity gradually decreases and gradually moves away from the center of the jet.The radial distribution of the circumferential component of velocity is almost unchanged.The average impact pressure coefficient on the wall surface of the disc gradually decreases,and the magnitude of the decrease first increases and then decreases.(5)The numerical calculation of the impulsive jet impinging on the rotating wall revealed that the jet fluid and the surrounding fluid exchanged mass,momentum,and energy under shear.The velocity of the fluid near the shear layer gradually decreased,and the radial distribution of the jet internal velocity change;The impact pressure on the impact wall first increases and then decreases,and the effective impact area remains unchanged.(6)The numerical calculation of the pulse jet impinging on the rotating wall under different Reynolds numbers,wall speeds and pulse periods is carried out.Independent of wall speed.With the increase of the Reynolds number and the pulse period,the dimensionless velocity on the jet axis and the pressure change on the impact wall appear a transition zone,and the velocity and pressure in the transition zone gradually develop towards the steady velocity and pressure of the continuous jet impact wall.Due to the water hammer effect,the pulse jet generates an impact pressure greater than the pressure of the continuous jet against the wall surface.