Experimental Study On Dynamic Characteristics Of Inner Wall Of Circular Tube Covered With Film

In recent years,driven by a variety of engineering and biological applications,the viscous fluid coating of the inner and outer walls of vertical circular tubes has become a research hotspot,especially in the coating of the protective layer of the tube wall,the surface coating of optical fiber,wire and cable has been widely used.At present,most of the existing methods for measuring the thickness of fluid film are contact measurement.However,the reliability and measurement accuracy of contact measurement results are not high.In order to further study the dynamic characteristics of coated inner wall of circular pipe,a set of non-contact experimental device for measuring coated inner wall of circular pipe was designed,and an image processing GUI interface software for digital extraction of coated process and instantaneous flow pattern was developed.The fluid film image of the inner wall of the vertical circular tube was obtained by using the function of CCD image fast collection and recording.The original image was processed by gray conversion,guided filtering,binarization,Canny edge detection,etc.,and all kinds of characteristic images needed for the experiment were summarized and calculated.The specific experimental results of this paper are as follows:1.In this paper,the viscosity is: ?= 3000 m Pa·s,?= 5000 m Pa·s and ?= 10000 m Pa·s Dimethicone Newtonian fluid as the fluid medium,respectively in 8 different flow rates of experimental research shows that: When the silicone oil at the same viscosity,with the increase of the flow rate,the average thickness of the fluid film is increasing,until the fluid is immersed in the entire tube inlet,forming a fluid plug in the inner wall of the tube;At the same fluid flow rate,with the increase of viscosity coefficient of silicone oil,the thickness of fluid film is also increasing.The temporal and spatial evolution characteristics of the fluid thin film of silicon oil at a flow rate of 11ml/min at a rate of ?=5000 m Pa·s are drawn,and the conclusions are summarized as follows: When the fluid flow of the silicone oil is stable,as time goes on,the fluid film is affected by the surface tension,and the small perturbations on the free surface will increase continuously.If the film is thick enough,the instability will increase unlimitedly,and the thickness of the fluid film will change gradually until they are squeezed away to form a fluid plug.2.In this paper,through the exploratory experimental study and analysis of the flow rates of two kinds of non-Newtonian polyacrylamide solutions at (?)_=15ml/min,(?)_=20ml/min,(?)_ =25ml/min and (?)_ =30ml/min respectively,it can be seen that: The same solution preparation of non-newtonian fluid,with the increase of flow rate,fluid film layer constantly tend to steady state flow,the gap between the surface wave changes constantly tend to be more stable,when the fluid flow and increasing effect of fluid flow form to unstable turbulence type development,but still the fluid film spiral down a small Angle,It keeps flowing asymmetrically.In this paper,the design of non-contact experimental device for measuring the inner coating of the tube,the developed GUI interface software for extracting the boundary contour of the inner coating and the image processing technology have certain guiding significance and reference value for the further study of the inner coating dynamic characteristics of the tube.