Inertial effects in the dynamics of the role of coagulation _1466

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Inertial effects in the dynamics of the role of coagulation
 
 
Abstract: This is the first micro-structure of the scale of turbulence is sub-micro scale dynamics of coagulation was studied, the inertia effect is proposed cause of the flocculation dynamics; proposed response to turbulent shear stress is the flocculation the decisive factor in the dynamics and the establishment of the dynamic similarity of flocculation. Article pointed out that macro-diffusion process should be divided into sub-microscopic diffusion and spread of two different physical processes, and the proliferation of sub-microscopic dynamics is the cause of the inertia effects, especially micro-vortex turbulence centrifugal effect.    Keywords: concrete dynamics     one, flocculation kinetics of Research     where P is unit of water bodies can; μ is the dynamic viscosity of the liquid. Due to the above formula is derived under laminar flow conditions, which apply to current state, has been a turbulent people care about the flocculation. This issue has been inconclusive. In fact, the above formula is under the condition of laminar flow velocity gradient. For the turbulent vortex turbulence is the role of the greatly increased turbulence in the momentum exchange, greatly in both of the turbulent velocity distribution, so the turbulence on the velocity gradient is much less than the calculated values. That being the case, the above formula to the water treatment engineering of why it can be used for half a century? Because the above formula P (units of water consumption) that a vortex with turbulence in the closely related micro, from the back we can see the contents of the article, it is these micro-structure of turbulence determines the dynamics of small particles in water and the collision between them. Through decades of engineering practice it has accumulated a large amount of empirical data above formula, use this to guide the engineering design course, no major problems. However, the above formula to improve the existing flocculation process has no value. Because increasing the flocculation velocity gradient must be increased to increase the velocity gradient is necessary to increase the energy consumption of water, that is, the flow rate of increase in flocculation. But the speed is limited flocculation process is the process of growing up with alum, the water flow rate should continue to decrease.     the other hand we can cite a complete contradiction to the theory and speed of the flocculation gradient engineering examples. Reaction cell in the grid a certain distance behind the grid in a homogeneous isotropic turbulence flow condition similar to that in the region of space different points in the flow are the same when the average speed, velocity gradient is zero. In accordance with the velocity gradient theory, the velocity gradient the greater the more the number of particle collisions. The flocculation reactor grid velocity gradient is zero, the reaction efficiency should be the worst. The opposite, the flocculation reactor grid effect is superior to all conventional reaction equipment. This project fully illustrated examples of velocity gradient theory is far from revealing the dynamic nature of the flocculation.     in flocculation studies, there is a school of turbulence with the turbulent diffusion of the agenda for the calculation of the average number of particle collisions. Finally, the conclusion with the same velocity gradient theory, the turbulence with the turbulent times in the particle collision energy increases. As used in this approach is the average turbulent diffusion equation, and therefore can not reveal the micro structure turbulence in the dynamic role in flocculation. Such as flocculation dynamics in the study, the research into micro and macro only has enough. Flocculation of particles due to collision with the turbulence in the dynamic role of the microstructure is closely related to the micro-structure scale, so completely free from the microscopic molecular motion of turbulent micro-structure, only with the thermodynamic coefficient. The macro-flow calculation is the people's attention when the average speed, time average pressure, time average concentration, not to reveal the micro structure turbulence in the dynamic role in flocculation. Therefore, the study of flocculation kinetics from the scale of turbulence micro-structure, from the submicroscopic scale research. Turbulence flocculation of the school is because the macro uses the average flow of statistical calculation methods, so we can not reveal the dynamic nature of the flocculation.     Second, the dynamic cause of flocculation     suggested that turbulence in the particle collision is caused by the turbulence. This recognition is not very precise. In fact there is no turbulent fluctuation, the so-called pulse is due to the result of the research methods used. People use traditional methods of Euler fluid dynamics to study law, that is observed in the fixed space point of water movement parameters change over time, so there are different sizes at different times in different parts of the turbulent vortex through a fixed spatial point, so the fixed measured space points show a strong rate of pulsation. If we follow the water particles move together, to observe the movement, you will find the speed of changes in water physical point is continuous, there is no pulse. In fact water is a continuous medium. Water velocity distribution is continuous, without any jump. Distance of two particles in the water near the speed difference between the more smaller, when the two particles a distance no study hours, the speed difference is also infinitely small, that is no speed difference. Water particle size is very small, similar to the proportion of water and therefore the flow is very good in the following. If the synchronous movement with the flow of these particles, because there is no speed difference will not collide. This shows that the flow of particles in order to collide with the water flow to be generated to the relative motion, so that water will produce the hydraulic resistance of particle movement, set the shape of spherical particles, the radius r0, the relative velocity between particles and water to v, the density of water p, spherical particles can be calculated as follows Fd suffered hydraulic resistance (slightly)     where po is the density of spherical particles. If it was omitted due to differences in particle size due to density changes can be seen from the above equation suffered hydraulic unit mass of spherical particles increases with size reduction of the resistance; that the greater the unit mass of particles smaller pressure drop suffered. While the above is for spherical lectures, but also applies to non-spherical particles. Suffered due to the different particle size hydraulic resistance are different, so different scale to produce a speed difference between. The speed difference for the neighboring particles of different scales to provide the conditions for the collision. How to make the water flow generated particles and the relative movement? The best way is to change the speed of the water. Because the water inertia (density) and particle inertia (density) is different from the speed change when the flow rate of their change (acceleration) are also different, making water and solid particles which produce the relative movement and collision of the adjacent particles of different scales provided the conditions.     rate of change in two ways: (1) is to change the average flow velocity, hydraulic pulse clarifier, wave tank, reaction tank and the hole room micro-flocculation filter, mainly using the average rate of change in water flow caused by the inertia effect for flocculation; (2) is to change the direction of flow, because turbulence in the vortex full of large and small, so when the water particles constantly in motion change their movement in the direction. When the water flow for the vortex motion under the action of the centrifugal force and flow of solid particles produced along the radial relative motion for different scales of the radial particle collisions along the Vortex provides the conditions. Particles in different scales in the turbulent vortex suffered centrifugal force per unit mass is different. This role will be to increase the vortex at different scales in turbulent radial particle collision probability. Here to discuss this issue. In the turbulent vortex in the body to take out a small, apparently acting on the radial direction from the body with two forces: one is the centrifugal force; the second is the pressure force. Both equilibrium. If the origin of coordinates taken at the center of the vortex motion, you can write the following equation: (abbreviated)     discussed by the above theory can be seen , if a significant increase in the flocculation and turbulent micro-pool, the ratio of the vortex, can dramatically increase the number of particle collision, effectively improve the flocculation effect. This can be in the flow channel flocculation additional multi-grid approach the eye holes to achieve. Since the inertia of water over the net, so that the large vortex flow over the net into a small vortex, small vortices into smaller vortices. No flocculation grid turbulence scale and the largest eddy flocculation channels the same magnitude scale. When the additional grid, the largest scale and mesh size vortex same order of magnitude.     additional holes in the grid after the eye has the following effects: (1) flow of water through the section of the grid is the speed section of intense change,You are not allowed to view links. Register or Login, the inertia effect is most strong, the highest probability of particle collision zone; (2) holes in the eye after the turbulence of the vortex grid scale drastically reduced. Increase the proportion of micro-vortex, vortex centrifugal effect would increase, effectively increasing the number of particle collision; (3) The inertia of flow over the net, a strong deformation of alum, so that alum in a low absorption level part, because of its role in deformation Roudong achieve high absorption level of the site, so that after making through the mesh becomes more dense alum.   

  three alum reasonable effective collision <? xml: namespace prefix = o ns = microsoft-com: office: office that gather together particles called effective collision collision, the collision of particles called to gather together the effective collision. If the condensation of particles in the flocculation will grow up too fast there are two issues: (1) the strength of alum grow too fast is weakened, the strong flow shear encountered in the process to make adsorption bridge will be cut was difficult to cut the continuous bridge up adsorption, a phenomenon known as the phenomenon of over reaction, should be absolutely prohibited; (2) some growing up too fast alum alum in water surface area dropped sharply, and some reaction imperfect loss of small particles of reaction conditions, these small particles and large particle collision probability decreases sharply, very difficult to grow up. These particles not only can not be retained by the sedimentation tank, it is difficult to filter retention. Flocculation alum particles can not grow too slowly though dense, but when it reaches the sedimentation tanks, and many do not grow to precipitation size particles, water quality will not be good. Resulting in the flocculation tank design that should be the reasonable control of alum particles grow.