CN105223106A - Aluminium powder trace method observes hydrothermal wave - Google Patents
Aluminium powder trace method observes hydrothermal wave Download PDFInfo
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- CN105223106A CN105223106A CN201510677788.4A CN201510677788A CN105223106A CN 105223106 A CN105223106 A CN 105223106A CN 201510677788 A CN201510677788 A CN 201510677788A CN 105223106 A CN105223106 A CN 105223106A
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Abstract
The present invention relates to after aluminium powder trace method observes thermocapillary convection unstability and produce hydrothermal wave, belong to physical measurement field, it primarily of light source 1, image capturing system 2, flake aluminum 3, treat that fluid measured 4, hot bath 5, cooling bath 6 form.When it causes the fluid 4 thermocapillary convection unstability being mixed with aluminium powder 3 under the horizontal temperature difference of hot bath 5 and cooling bath 6 drives, when the change of fluid 4 flow direction causes the change of aluminium powder 3 flow direction, illuminated flake aluminum surface is changed the usable reflection amount that light source 1 emits beam, the image light and shade brightness that image capturing system 2 shows changes thereupon, thus observe hydrothermal wave, specific implementation process: take flake aluminum, aluminium powder mixes with fluid well-distributing, regulate light source and image capturing system, observe hydrothermal wave, be mainly used in the observation of hydrothermal wave in curved interface or planar interface fluid.
Description
Technical field:
The present invention relates to the hydrothermal wave produced after aluminium powder trace method observes thermocapillary convection unstability, belong to physical measurement field.
Background technology:
In gas-liquid two-phase system, the flowing that fluid produces because of surface tension gradient under the effect of tangential temperature gradients is called thermocapillary convection, when in microgravity environment or surface state, liquid layer is thinner, the impact of buoyancy weakens, thermocapillary convection just highlights, if additional thermograde is enough large, thermocapillary convection also can unstability, velocity field and temperature field are space-time fluctuation status, produce the unstable phenomenons such as hydrothermal wave.The thermocapillary convection of this space-time fluctuation brings adverse effect often to the production run of some reality, and such as, in Czochralski (Cz) method single crystal growth process, it will cause the defects such as segregation, reduce crystal mass.On the other hand, hydrothermal wave itself is a kind of typically orderly dissipative structure, the feature of research hydrothermal wave, contributes to the abundant and development nonequilibrium thermodynamics theory of dissipative structures.Therefore, this unstable phenomenon of research hydrothermal wave, had both had important engineering practical value, had also had important academic significance.In the past, the research of people to this dissipative structure of hydrothermal wave mainly concentrates in horizontal interface liquid layer.In fact, hydrothermal wave may be produced equally in curved interface liquid layer, as drop on substrate evaporates the hydrothermal wave caused.
The existing method of observing hydrothermal wave in experiment has shadowing method and thermal infrared imager method.The wherein ultimate principle of shadowing method: for most transparent fluid, the refractive index of fluid and temperature correlation, light can be deflected by direction of propagation when fluid and Air Interface, when fluid interface temperature is different, refractive index is just different, and the deflection of emergent ray is also just different.When being furnished with screen in emergent ray side, screen will being formed the different hot spot of light and shade, indirectly reflecting the Temperature Distribution of fluid interface, thus observing the image of hydrothermal wave.The work ultimate principle of infrared thermography: natural any object all can outside heat of emission ray, the wavelength of heat ray and the temperature of object are closely related, the heat ray signal that infrared sensor detects by thermal infrared imager changes temperature signal into, measure the temperature of body surface, thus observe the image of flow surface hydrothermal wave.
Observe hydrothermal wave effect better in horizontal interface fluid top shadow method and thermal infrared imager method, but for the fluid with curved interface, existing means better even can not be difficult to the hydrothermal wave image be accurate in one's observation, and major defect has:
One, for the fluid with curved interface, because curved interface is to the scattering process of light, the hydrothermal wave distortion of shadowing method display is serious, cannot the correct status of reflect heat fluid wave.
Two, because many fluids self are also the ultrared transparent body or translucent body, when adopting infrared heat image instrument measuring flow surface temperature, the heat ray of the lower certain thickness fluid in surface also can penetrate or partial penetration fluid, the temperature that thermal imaging system measures is not just the true temperature of flow surface yet, thus is difficult to the correct images observing hydrothermal wave.
Three, when there is hydrothermal wave but flow surface temperature fluctuation is less, if temperature fluctuation amplitude is lower than the temperature resolution of thermal infrared imager, then can not observe hydrothermal wave image, therefore thermal infrared imager can not be used for observing faint hydrothermal wave.
Four, shadowing method and thermal infrared imager method all belong to optical means, be all easily subject to external environmental interference, and thermal infrared imager are expensive.
Therefore be badly in need of that a kind of fluid, resolution that can be used for having curved interface is high, small investment, easy to operate hydrothermal wave display packing.
Summary of the invention:
In order to overcome the deficiency of existing hydrothermal wave Observations Means, the invention provides aluminium powder trace method and observing hydrothermal wave.Element of the present invention: light source 1, image capturing system 2, flake aluminum 3, detected fluid 4, hot bath 5, cooling bath 6 form.Ultimate principle of the present invention: aluminium powder 3 will be driven to flow when the fluid 4 being mixed with aluminium powder 3 flows, the resistance that the aluminium powder of following fluid flowing is subject to is little, and flake aluminum total surface is parallel with fluid flow direction.When aluminium powder surface is vertical with incident light, reflective surface area is maximum, and image is the brightest; When aluminium powder surface is parallel with incident light, reflective surface area is minimum, and image is the darkest.When the flow direction of fluid is changed to vertical direction gradually by horizontal direction, aluminium powder surface changes to 0 degree by 90 degree with the angle of incident light, and image is by bright dimmed; Otherwise, then by secretly brightening.After thermocapillary convection unstability, the flow direction of fluid is time-space periodicity change, is mixed with the flow surface then light and shade alternately change thereupon of aluminium powder, thus is shown by astable hydrothermal wave.
Aluminium powder trace method provided by the invention compared with the conventional method, has following advantage:
One, the present invention not only solves the problem having hydrothermal wave in curved interface fluid and be difficult to show, and also can be used for the display of hydrothermal wave in planar interface fluid.
Two, the present invention is the direct display of fluid flow state, even if faint hydrothermal wave also can show, and aluminium powder trace method antijamming capability is to external world strong.
Three, the present invention does not need complicated instrument and equipment, and aluminium powder is easy to obtain, easy and simple to handle, small investment, be easy to realize.
Accompanying drawing illustrates:
Fig. 1 is that aluminium powder trace method observes hydrothermal wave device schematic diagram
The present invention forms primarily of light source 1, image capturing system 2, flake aluminum 3, detected fluid 4, hot bath 5, cooling bath 6.
Specific implementation method:
One, use balance to take a certain amount of flake aluminum 3 (diameter is less than 20 microns), aluminium powder is added in fluid 4 to be seen, fully stir and make aluminium powder Homogeneous phase mixing in fluid.
Two, placement of images acquisition system 2 and light source 1 directly over detected fluid, all positive convection cell surface, regulates image capturing system focal length and light-source brightness, until image capturing system terminal observes is to Experimental Area image clearly.
Three, cleaned up Experimental Area, join in Experimental Area by the fluid being mixed with aluminium powder tracer agent, the temperature difference between change hot bath 5 and cooling bath 6 is until image capturing system 2 observes hydrothermal wave image.
Claims (2)
1. the present invention relates to the hydrothermal wave produced after aluminium powder trace method observes thermocapillary convection unstability, belong to physical measurement field, its design feature is primarily of light source 1, image capturing system 2, flake aluminum 3, detected fluid 4, hot bath 5, cooling bath 6 forms, its characteristics of principle cause under the horizontal temperature difference of hot bath 5 and cooling bath 6 drives be mixed with aluminium powder 3 fluid 4 in after thermocapillary convection unstability, when the change of fluid 4 flow direction causes the change of aluminium powder 3 flow direction, illuminated aluminium powder surface is changed the usable reflection amount that light source 1 emits beam, the image light and shade brightness that image capturing system 2 shows changes thereupon, thus observe hydrothermal wave.
2. the hydrothermal wave that the aluminium powder trace method in right descriptions 1 produces after observing thermocapillary convection unstability, its feature is that the ultimate principle of aluminium powder trace method being observed stable state B é nard-Marangoni convective methods is applied in the unstable state hydrothermal wave observing curved interface or planar interface fluid.
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| CN111504854A (en) * | 2020-04-13 | 2020-08-07 | 中国矿业大学 | Temperature difference type measuring device and method for viscosity of Newton fluid |
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Cited By (2)
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