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The laminar-turbulent transition zone is investigated for a broad class of jet flows. The problem is considered in terms of the inviscid model. The solution of the initial-boundary value problem for three-dimensional unsteady Euler equations is found by the Bubnov-Galerkin method using the generalized Rayleigh approach [1–4]. The occurrence, subsequent nonlinear evolution and interaction of two-dimensional wave disturbances are studied, together with their secondary instability with respect to three-dimensional disturbances.

During processing of cutting materials due to friction between tools and materials, a considerable amount of heat is released to the development of high cutting forces. Excess heat from the cutting area may aggravate the cutting process, the surfaces resulting from the cutting process may have a several defects. By simulating the flow phenomena on the computer, different forms of nozzles that send the liquid to the work area are studied to make the cutting process more efficient. This study attempts to simulate the flow of cooling fluid in an integrated system and also to quantify the amount of heat entering the workpiece during the machining processes. Simulation using the finite element method for the machining area was done for conventional cutting processes, taking into account the environment. The simulation also takes into account the convective cooling of the working fluid in the MQL system. By assessing the cooling efficiency of different lubrication conditions of the coolant, based on their convective heat transfer coefficient and the temperature in the cutting zone.

This paper analyzes several types of cooling agents, their properties and how they can be chosen for a better heat dispersion resulting from the cutting process. An excessive heat in the cutting zone leads to excessive wear of the cutting tools, that leading finally to additional costs of their acquisition and due to wear is reached in cutting process more irregular surfaces. The coolant chosen can be a combination of different cooling fluids from the most simple and inexpensive to more complex, the difference between them being more appropriately cool the processing area. The fluid flow parameters of coolant can be influenced by the nature of the fluid or fluids used, the geometry of the nozzle in order to achieve a better dispersion of the lubricant on the area to be processed. A smaller amount of fluid is important in terms of the economy lubricant, because some of these lubricants are quite expensive. A minimal quantity of lubricant (MQL) may have a better impact on the environment and the health of the operator because the coolants in contact with overheated machined surface may develop a substantial amount of these gases that are not always beneficial to health.

Studies and experimental research in the field of shredding of food materials with soft texture by means of metal wire cutting heated to 97degC are particularly important, their results can bring more clarification regarding the shredding analysis, analysis of cutting aspect, analysis of quantitative and quality of juice and / or material loses, determining of necessary shredding forces. For a better understanding of the phenomenon occurring in the shredding of food materials with soft texture, have been selected for study a large variety of materials with different textures and properties. In the experimental determinations by heating of metal wire cutting, the resulted surfaces after the cutting are more regular, are needed lower cutting forces necessary to shred the material and results reduces quantities of juice or material losses.

This paper aims analysing the type of coolants and the correct choice of that as well as the dispensation in the processing area to control the temperature resulted from the cutting operation and the choose of the cutting operating modes. A high temperature in the working area over a certain amount can be harmful in terms of the quality of resulting surface and that could have some influences on the life of the cutting tool. The coolant chosen can be a combination of different cooling fluids in order to achieve a better cooling of the cutting area at the same time for carrying out the proper lubrication of that area. The fluid flow parameters of coolant can be influenced by the nature of the fluid or fluids used, the geometry of the nozzle used which generally has a convergent-divergent geometry in order to achieve a better dispersion of the coolant / lubricant on the area to be processed. A smaller amount of fluid is important in terms of the economy lubricant, because they are quite expensive. A minimal amount of lubricant may have a better impact on the environment and the health of the operator because the coolants in contact with overheated machined surface may develop a substantial amount of these gases that are not always beneficial to health.

A study of geometry nozzle is particularly important in optimizing the quantity of coolant in terms to minimize that quantity or coolant can be used for lubrication of machines moving parts. Coolants can be from the simplest (water, air) as well as a mixture of liquid (emulsions) to achieve a good cooling in function of temperature that develops in the area concerned. The study from this paper proposes an analysis and a simulation of flow through the convergent-divergent nozzle type to optimize them and to use a minimum quantity of coolant or lubricant. This study is focus on the analysis of cooling systems for cutting processes on machine tools.